| /*- |
| * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 |
| * The Regents of the University of California. All rights reserved. |
| * Copyright (c) 2007-2008,2010 |
| * Swinburne University of Technology, Melbourne, Australia. |
| * Copyright (c) 2009-2010 Lawrence Stewart <lstewart@freebsd.org> |
| * Copyright (c) 2010 The FreeBSD Foundation |
| * Copyright (c) 2010-2011 Juniper Networks, Inc. |
| * All rights reserved. |
| * |
| * Portions of this software were developed at the Centre for Advanced Internet |
| * Architectures, Swinburne University of Technology, by Lawrence Stewart, |
| * James Healy and David Hayes, made possible in part by a grant from the Cisco |
| * University Research Program Fund at Community Foundation Silicon Valley. |
| * |
| * Portions of this software were developed at the Centre for Advanced |
| * Internet Architectures, Swinburne University of Technology, Melbourne, |
| * Australia by David Hayes under sponsorship from the FreeBSD Foundation. |
| * |
| * Portions of this software were developed by Robert N. M. Watson under |
| * contract to Juniper Networks, Inc. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * 1. Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * 4. Neither the name of the University nor the names of its contributors |
| * may be used to endorse or promote products derived from this software |
| * without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND |
| * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE |
| * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
| * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
| * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
| * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
| * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| * SUCH DAMAGE. |
| * |
| * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 |
| */ |
| |
| |
| /* |
| * Determine a reasonable value for maxseg size. |
| * If the route is known, check route for mtu. |
| * If none, use an mss that can be handled on the outgoing interface |
| * without forcing IP to fragment. If no route is found, route has no mtu, |
| * or the destination isn't local, use a default, hopefully conservative |
| * size (usually 512 or the default IP max size, but no more than the mtu |
| * of the interface), as we can't discover anything about intervening |
| * gateways or networks. We also initialize the congestion/slow start |
| * window to be a single segment if the destination isn't local. |
| * While looking at the routing entry, we also initialize other path-dependent |
| * parameters from pre-set or cached values in the routing entry. |
| * |
| * Also take into account the space needed for options that we |
| * send regularly. Make maxseg shorter by that amount to assure |
| * that we can send maxseg amount of data even when the options |
| * are present. Store the upper limit of the length of options plus |
| * data in maxopd. |
| * |
| * NOTE that this routine is only called when we process an incoming |
| * segment, or an ICMP need fragmentation datagram. Outgoing SYN/ACK MSS |
| * settings are handled in tcp_mssopt(). |
| */ |
| |
| #include <errno.h> |
| #include <string.h> |
| #include <strings.h> |
| |
| #include "tcp.h" |
| #include "tcp_fsm.h" |
| #include "tcp_seq.h" |
| #include "tcp_timer.h" |
| #include "tcp_var.h" |
| #include "../lib/bitmap.h" |
| #include "../lib/cbuf.h" |
| #include "icmp_var.h" |
| #include "ip.h" |
| #include "ip6.h" |
| #include "sys/queue.h" |
| |
| #include "tcp_const.h" |
| |
| /* samkumar: Copied from in.h */ |
| #define IPPROTO_DONE 267 |
| |
| /* samkumar: Copied from sys/libkern.h */ |
| static int imax(int a, int b) { return (a > b ? a : b); } |
| static int imin(int a, int b) { return (a < b ? a : b); } |
| |
| static int min(int a, int b) { return imin(a, b); } |
| |
| static void tcp_dooptions(struct tcpopt *, uint8_t *, int, int); |
| static void |
| tcp_do_segment(struct ip6_hdr* ip6, struct tcphdr *th, otMessage* msg, |
| struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos, |
| struct tcplp_signals* sig); |
| static void tcp_xmit_timer(struct tcpcb *, int); |
| void tcp_hc_get(/*struct in_conninfo *inc*/ struct tcpcb* tp, struct hc_metrics_lite *hc_metrics_lite); |
| static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *); |
| |
| /* |
| * CC wrapper hook functions |
| */ |
| static inline void |
| cc_ack_received(struct tcpcb *tp, struct tcphdr *th, uint16_t type) |
| { |
| tp->ccv->bytes_this_ack = BYTES_THIS_ACK(tp, th); |
| if (tp->snd_cwnd <= tp->snd_wnd) |
| tp->ccv->flags |= CCF_CWND_LIMITED; |
| else |
| tp->ccv->flags &= ~CCF_CWND_LIMITED; |
| |
| if (type == CC_ACK) { |
| if (tp->snd_cwnd > tp->snd_ssthresh) { |
| tp->t_bytes_acked += min(tp->ccv->bytes_this_ack, |
| V_tcp_abc_l_var * tp->t_maxseg); |
| if (tp->t_bytes_acked >= tp->snd_cwnd) { |
| tp->t_bytes_acked -= tp->snd_cwnd; |
| tp->ccv->flags |= CCF_ABC_SENTAWND; |
| } |
| } else { |
| tp->ccv->flags &= ~CCF_ABC_SENTAWND; |
| tp->t_bytes_acked = 0; |
| } |
| } |
| |
| if (CC_ALGO(tp)->ack_received != NULL) { |
| /* XXXLAS: Find a way to live without this */ |
| tp->ccv->curack = th->th_ack; |
| CC_ALGO(tp)->ack_received(tp->ccv, type); |
| } |
| } |
| |
| static inline void |
| cc_conn_init(struct tcpcb *tp) |
| { |
| struct hc_metrics_lite metrics; |
| int rtt; |
| |
| /* |
| * samkumar: remove locks, inpcb, and stats. |
| */ |
| |
| /* samkumar: Used to take &inp->inp_inc as an argument. */ |
| tcp_hc_get(tp, &metrics); |
| |
| if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { |
| tp->t_srtt = rtt; |
| tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; |
| if (metrics.rmx_rttvar) { |
| tp->t_rttvar = metrics.rmx_rttvar; |
| } else { |
| /* default variation is +- 1 rtt */ |
| tp->t_rttvar = |
| tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; |
| } |
| TCPT_RANGESET(tp->t_rxtcur, |
| ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, |
| tp->t_rttmin, TCPTV_REXMTMAX); |
| } |
| if (metrics.rmx_ssthresh) { |
| /* |
| * There's some sort of gateway or interface |
| * buffer limit on the path. Use this to set |
| * the slow start threshhold, but set the |
| * threshold to no less than 2*mss. |
| */ |
| tp->snd_ssthresh = max(2 * tp->t_maxseg, metrics.rmx_ssthresh); |
| } |
| |
| /* |
| * Set the initial slow-start flight size. |
| * |
| * RFC5681 Section 3.1 specifies the default conservative values. |
| * RFC3390 specifies slightly more aggressive values. |
| * RFC6928 increases it to ten segments. |
| * Support for user specified value for initial flight size. |
| * |
| * If a SYN or SYN/ACK was lost and retransmitted, we have to |
| * reduce the initial CWND to one segment as congestion is likely |
| * requiring us to be cautious. |
| */ |
| if (tp->snd_cwnd == 1) |
| tp->snd_cwnd = tp->t_maxseg; /* SYN(-ACK) lost */ |
| else if (V_tcp_initcwnd_segments) |
| tp->snd_cwnd = min(V_tcp_initcwnd_segments * tp->t_maxseg, |
| max(2 * tp->t_maxseg, V_tcp_initcwnd_segments * 1460)); |
| else if (V_tcp_do_rfc3390) |
| tp->snd_cwnd = min(4 * tp->t_maxseg, |
| max(2 * tp->t_maxseg, 4380)); |
| else { |
| /* Per RFC5681 Section 3.1 */ |
| if (tp->t_maxseg > 2190) |
| tp->snd_cwnd = 2 * tp->t_maxseg; |
| else if (tp->t_maxseg > 1095) |
| tp->snd_cwnd = 3 * tp->t_maxseg; |
| else |
| tp->snd_cwnd = 4 * tp->t_maxseg; |
| } |
| |
| if (CC_ALGO(tp)->conn_init != NULL) |
| CC_ALGO(tp)->conn_init(tp->ccv); |
| |
| /* samkumar: print statement for debugging. Resurrect with DEBUG macro? */ |
| #ifdef INSTRUMENT_TCP |
| tcplp_sys_log("TCP CC_INIT %u %d %d", (unsigned int) tcplp_sys_get_millis(), (int) tp->snd_cwnd, (int) tp->snd_ssthresh); |
| #endif |
| } |
| |
| inline void |
| cc_cong_signal(struct tcpcb *tp, struct tcphdr *th, uint32_t type) |
| { |
| /* samkumar: Remove locks and stats from this function. */ |
| |
| switch(type) { |
| case CC_NDUPACK: |
| if (!IN_FASTRECOVERY(tp->t_flags)) { |
| tp->snd_recover = tp->snd_max; |
| if (tp->t_flags & TF_ECN_PERMIT) |
| tp->t_flags |= TF_ECN_SND_CWR; |
| } |
| break; |
| case CC_ECN: |
| if (!IN_CONGRECOVERY(tp->t_flags)) { |
| tp->snd_recover = tp->snd_max; |
| if (tp->t_flags & TF_ECN_PERMIT) |
| tp->t_flags |= TF_ECN_SND_CWR; |
| } |
| break; |
| case CC_RTO: |
| tp->t_dupacks = 0; |
| tp->t_bytes_acked = 0; |
| EXIT_RECOVERY(tp->t_flags); |
| tp->snd_ssthresh = max(2, min(tp->snd_wnd, tp->snd_cwnd) / 2 / |
| tp->t_maxseg) * tp->t_maxseg; |
| tp->snd_cwnd = tp->t_maxseg; |
| |
| /* |
| * samkumar: Stats for TCPlp: count the number of timeouts (RTOs). |
| * I've commented this out (with #if 0) because it isn't part of TCP |
| * functionality. At some point, we may want to bring it back to |
| * measure performance. |
| */ |
| #if 0 |
| tcplp_timeoutRexmitCnt++; |
| #endif |
| #ifdef INSTRUMENT_TCP |
| tcplp_sys_log("TCP CC_RTO %u %d %d", (unsigned int) tcplp_sys_get_millis(), (int) tp->snd_cwnd, (int) tp->snd_ssthresh); |
| #endif |
| break; |
| case CC_RTO_ERR: |
| /* RTO was unnecessary, so reset everything. */ |
| tp->snd_cwnd = tp->snd_cwnd_prev; |
| tp->snd_ssthresh = tp->snd_ssthresh_prev; |
| tp->snd_recover = tp->snd_recover_prev; |
| if (tp->t_flags & TF_WASFRECOVERY) |
| ENTER_FASTRECOVERY(tp->t_flags); |
| if (tp->t_flags & TF_WASCRECOVERY) |
| ENTER_CONGRECOVERY(tp->t_flags); |
| tp->snd_nxt = tp->snd_max; |
| tp->t_flags &= ~TF_PREVVALID; |
| tp->t_badrxtwin = 0; |
| #ifdef INSTRUMENT_TCP |
| tcplp_sys_log("TCP CC_RTO_ERR %u %d %d", (unsigned int) tcplp_sys_get_millis(), (int) tp->snd_cwnd, (int) tp->snd_ssthresh); |
| #endif |
| break; |
| } |
| |
| if (CC_ALGO(tp)->cong_signal != NULL) { |
| if (th != NULL) |
| tp->ccv->curack = th->th_ack; |
| CC_ALGO(tp)->cong_signal(tp->ccv, type); |
| } |
| } |
| |
| static inline void |
| cc_post_recovery(struct tcpcb *tp, struct tcphdr *th) |
| { |
| /* samkumar: remove lock */ |
| |
| /* XXXLAS: KASSERT that we're in recovery? */ |
| if (CC_ALGO(tp)->post_recovery != NULL) { |
| tp->ccv->curack = th->th_ack; |
| CC_ALGO(tp)->post_recovery(tp->ccv); |
| } |
| /* XXXLAS: EXIT_RECOVERY ? */ |
| tp->t_bytes_acked = 0; |
| } |
| |
| |
| /* |
| * Indicate whether this ack should be delayed. We can delay the ack if |
| * following conditions are met: |
| * - There is no delayed ack timer in progress. |
| * - Our last ack wasn't a 0-sized window. We never want to delay |
| * the ack that opens up a 0-sized window. |
| * - LRO wasn't used for this segment. We make sure by checking that the |
| * segment size is not larger than the MSS. |
| * - Delayed acks are enabled or this is a half-synchronized T/TCP |
| * connection. |
| */ |
| #define DELAY_ACK(tp, tlen) \ |
| ((!tcp_timer_active(tp, TT_DELACK) && \ |
| (tp->t_flags & TF_RXWIN0SENT) == 0) && \ |
| (tlen <= tp->t_maxopd) && \ |
| (V_tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) |
| |
| static inline void |
| cc_ecnpkt_handler(struct tcpcb *tp, struct tcphdr *th, uint8_t iptos) |
| { |
| /* samkumar: remove lock */ |
| |
| if (CC_ALGO(tp)->ecnpkt_handler != NULL) { |
| switch (iptos & IPTOS_ECN_MASK) { |
| case IPTOS_ECN_CE: |
| tp->ccv->flags |= CCF_IPHDR_CE; |
| break; |
| case IPTOS_ECN_ECT0: |
| tp->ccv->flags &= ~CCF_IPHDR_CE; |
| break; |
| case IPTOS_ECN_ECT1: |
| tp->ccv->flags &= ~CCF_IPHDR_CE; |
| break; |
| } |
| |
| if (th->th_flags & TH_CWR) |
| tp->ccv->flags |= CCF_TCPHDR_CWR; |
| else |
| tp->ccv->flags &= ~CCF_TCPHDR_CWR; |
| |
| if (tp->t_flags & TF_DELACK) |
| tp->ccv->flags |= CCF_DELACK; |
| else |
| tp->ccv->flags &= ~CCF_DELACK; |
| |
| CC_ALGO(tp)->ecnpkt_handler(tp->ccv); |
| |
| if (tp->ccv->flags & CCF_ACKNOW) |
| tcp_timer_activate(tp, TT_DELACK, tcp_delacktime); |
| } |
| } |
| |
| /* |
| * External function: look up an entry in the hostcache and fill out the |
| * supplied TCP metrics structure. Fills in NULL when no entry was found or |
| * a value is not set. |
| */ |
| /* |
| * samkumar: This function is taken from tcp_hostcache.c. We have no host cache |
| * in TCPlp, so I changed this to always act as if there is a miss. I removed |
| * the first argument, formerly "struct in_coninfo *inc". |
| */ |
| void |
| tcp_hc_get(struct tcpcb* tp, struct hc_metrics_lite *hc_metrics_lite) |
| { |
| bzero(hc_metrics_lite, sizeof(*hc_metrics_lite)); |
| } |
| |
| /* |
| * External function: look up an entry in the hostcache and return the |
| * discovered path MTU. Returns NULL if no entry is found or value is not |
| * set. |
| */ |
| /* |
| * samkumar: This function is taken from tcp_hostcache.c. We have no host cache |
| * in TCPlp, so I changed this to always act as if there is a miss. |
| */ |
| uint64_t |
| tcp_hc_getmtu(struct tcpcb* tp) |
| { |
| return 0; |
| } |
| |
| |
| /* |
| * Issue RST and make ACK acceptable to originator of segment. |
| * The mbuf must still include the original packet header. |
| * tp may be NULL. |
| */ |
| /* |
| * samkumar: Original signature was: |
| * static void tcp_dropwithreset(struct mbuf *m, struct tcphdr *th, struct tcpcb *tp, |
| * int tlen, int rstreason) |
| */ |
| void |
| tcp_dropwithreset(struct ip6_hdr* ip6, struct tcphdr *th, struct tcpcb *tp, otInstance* instance, |
| int tlen, int rstreason) |
| { |
| /* |
| * samkumar: I removed logic to skip this for broadcast or multicast |
| * packets. In the FreeBSD version of this function, it would just |
| * call m_freem(m), if m->m_flags has M_BCAST or M_MCAST set, and not |
| * send a response packet. |
| * I also removed bandwidth limiting. |
| */ |
| if (th->th_flags & TH_RST) |
| return; |
| |
| /* tcp_respond consumes the mbuf chain. */ |
| if (th->th_flags & TH_ACK) { |
| tcp_respond(tp, instance, ip6, th, (tcp_seq) 0, th->th_ack, TH_RST); |
| } else { |
| if (th->th_flags & TH_SYN) |
| tlen++; |
| tcp_respond(tp, instance, ip6, th, th->th_seq + tlen, (tcp_seq) 0, TH_RST | TH_ACK); |
| } |
| return; |
| } |
| |
| /* |
| * TCP input handling is split into multiple parts: |
| * tcp6_input is a thin wrapper around tcp_input for the extended |
| * ip6_protox[] call format in ip6_input |
| * tcp_input handles primary segment validation, inpcb lookup and |
| * SYN processing on listen sockets |
| * tcp_do_segment processes the ACK and text of the segment for |
| * establishing, established and closing connections |
| */ |
| /* samkumar: The signature of this function was originally: |
| tcp_input(struct mbuf **mp, int *offp, int proto) */ |
| /* NOTE: tcp_fields_to_host(th) must be called before this function is called. */ |
| int |
| tcp_input(struct ip6_hdr* ip6, struct tcphdr* th, otMessage* msg, struct tcpcb* tp, struct tcpcb_listen* tpl, |
| struct tcplp_signals* sig) |
| { |
| /* |
| * samkumar: I significantly modified this function, compared to the |
| * FreeBSD version. This function used to be reponsible for matching an |
| * incoming TCP segment to its TCB. That functionality is now done by |
| * TCPlp, and this function is only called once a match has been |
| * identified. |
| * |
| * The tp and tpl arguments are used to indicate the match. Exactly one of |
| * them must be NULL, and the other must be set. If tp is non-NULL, then |
| * this function assumes that the packet was matched to an active socket |
| * (connection endpoint). If tpl is non-NULL, then this function assumes |
| * that this packet is a candidate match for a passive socket (listener) |
| * and attempts to set up a new connection if the flags, sequence numbers, |
| * etc. look OK. |
| * |
| * TCPlp assumes that the packets are IPv6, so I removed any logic specific |
| * to IPv4. |
| * |
| * And of course, all code pertaining to locks and stats has been removed. |
| */ |
| int tlen = 0, off; |
| int thflags; |
| uint8_t iptos = 0; |
| int drop_hdrlen; |
| int rstreason = 0; |
| struct tcpopt to; /* options in this segment */ |
| uint8_t* optp = NULL; |
| int optlen = 0; |
| to.to_flags = 0; |
| KASSERT(tp || tpl, ("One of tp and tpl must be positive")); |
| |
| /* |
| * samkumar: Here, there used to be code that handled preprocessing: |
| * calling m_pullup(m, sizeof(*ip6) + sizeof(*th)) to get the headers |
| * contiguous in memory, setting the ip6 and th pointers, validating the |
| * checksum, and dropping packets with unspecified source address. In |
| * TCPlp, all of this is done for a packet before this function is called. |
| */ |
| |
| tlen = ntohs(ip6->ip6_plen); // assume *off == sizeof(*ip6) |
| |
| /* |
| * samkumar: Logic that handled IPv4 was deleted below. I won't add a |
| * comment every time this is done, but I'm putting it here (one of the |
| * first instances of this) for clarity. |
| */ |
| iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff; |
| |
| /* |
| * Check that TCP offset makes sense, |
| * pull out TCP options and adjust length. XXX |
| */ |
| off = (th->th_off_x2 >> TH_OFF_SHIFT) << 2; |
| if (off < sizeof (struct tcphdr) || off > tlen) { |
| goto drop; |
| } |
| tlen -= off; /* tlen is used instead of ti->ti_len */ |
| /* samkumar: now, tlen is the length of the data */ |
| |
| if (off > sizeof (struct tcphdr)) { |
| /* |
| * samkumar: I removed a call to IP6_EXTHDR_CHECK, which I believe |
| * checks for IPv6 extension headers. In TCPlp, we assume that these |
| * are handled elsewhere in the networking stack, before the incoming |
| * packet is processed at the TCP layer. I also removed the followup |
| * calls to reassign the ip6 and th pointers. |
| */ |
| optlen = off - sizeof (struct tcphdr); |
| optp = (uint8_t *)(th + 1); |
| } |
| |
| thflags = th->th_flags; |
| |
| /* |
| * samkumar: There used to be a call here to tcp_fields_to_host(th), which |
| * changes the byte order of various fields to host format. I removed this |
| * call from there and handle it in TCPlp, before calling this. The reason |
| * is that it's possible for this function to be called twice by TCPlp's |
| * logic (e.g., if the packet matches a TIME-WAIT socket this function |
| * returns early, and the packet may then match a listening socket, at |
| * which ppoint this function will be called again). Thus, any operations |
| * like this, which mutate the packet itself, need to happen before calling |
| * this function. |
| */ |
| |
| /* |
| * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options. |
| * |
| * samkumar: My TCP header is in a different buffer from the IP header. |
| * drop_hdrlen is only meaningful as an offset into the TCP buffer, |
| * because it is used to determine how much of the packet to discard |
| * before copying it into the receive buffer. Therefore, my offset does |
| * not include the length of IP header and options, only the length of |
| * the TCP header and options. |
| */ |
| drop_hdrlen = /*off0 +*/ off; |
| |
| /* |
| * Locate pcb for segment; if we're likely to add or remove a |
| * connection then first acquire pcbinfo lock. There are three cases |
| * where we might discover later we need a write lock despite the |
| * flags: ACKs moving a connection out of the syncache, ACKs for a |
| * connection in TIMEWAIT and SYNs not targeting a listening socket. |
| */ |
| |
| /* |
| * samkumar: Locking code is removed, invalidating most of the above |
| * comment. |
| */ |
| |
| /* |
| * samkumar: The FreeBSD code at logic here to check m->m_flags for the |
| * M_IP6_NEXTHOP flag, and search for the PACKET_TAG_IPFORWARD tag and |
| * store it in fwd_tag if so. In TCPlp, we assume that the IPv6 layer of |
| * the host network stack handles this kind of IPv6-related functionality, |
| * so this logic has been removed. |
| */ |
| |
| /* |
| * samkumar: Here, there was code to match the packet to an inpcb and reply |
| * with an RST segment if no match is found. This included taking the |
| * fwd_tag into account, if set above (see the previous comment). I removed |
| * this code because, in TCPlp, this is done before calling this function. |
| */ |
| |
| /* |
| * A previous connection in TIMEWAIT state is supposed to catch stray |
| * or duplicate segments arriving late. If this segment was a |
| * legitimate new connection attempt, the old INPCB gets removed and |
| * we can try again to find a listening socket. |
| * |
| * At this point, due to earlier optimism, we may hold only an inpcb |
| * lock, and not the inpcbinfo write lock. If so, we need to try to |
| * acquire it, or if that fails, acquire a reference on the inpcb, |
| * drop all locks, acquire a global write lock, and then re-acquire |
| * the inpcb lock. We may at that point discover that another thread |
| * has tried to free the inpcb, in which case we need to loop back |
| * and try to find a new inpcb to deliver to. |
| * |
| * XXXRW: It may be time to rethink timewait locking. |
| */ |
| /* |
| * samkumar: The original code checked inp->inp_flags & INP_TIMEWAIT. I |
| * changed it to instead check tp->t_state, since we don't use inpcbs in |
| * TCPlp. |
| */ |
| if (tp && tp->t_state == TCP6S_TIME_WAIT) { |
| /* |
| * samkumar: There's nothing wrong with the call to tcp_dooptions call |
| * that I've commented out below; it's just that the modified |
| * "tcp_twcheck" function no longer needs the options structure, so |
| * I figured that there's no longer a good reason to parse the options. |
| * In fact, this call was probably unnecessary even in the original |
| * FreeBSD TCP code, since tcp_twcheck, even without my modifications, |
| * did not use the pointer to the options structure! |
| */ |
| //if (thflags & TH_SYN) |
| //tcp_dooptions(&to, optp, optlen, TO_SYN); |
| /* |
| * samkumar: The original code would "goto findpcb;" if this branch is |
| * taken. Matching with a TCB is done outside of this function in |
| * TCPlp, so we instead return a special value so that the caller knows |
| * to try re-matching this packet to a socket. |
| */ |
| if (tcp_twcheck(tp,/*inp, &to,*/ th, /*m,*/ tlen)) |
| return (RELOOKUP_REQUIRED); |
| return (IPPROTO_DONE); |
| } |
| /* |
| * The TCPCB may no longer exist if the connection is winding |
| * down or it is in the CLOSED state. Either way we drop the |
| * segment and send an appropriate response. |
| */ |
| /* |
| * samkumar: There used to be code here that grabs the tp from the inpcb |
| * and drops with reset if the connection is in the closed state or if |
| * the tp is NULL. In TCPlp, the equivalent logic is done before entering |
| * this function. There was also code here to handle TCP offload, which |
| * TCPlp does not handle. |
| */ |
| |
| /* |
| * We've identified a valid inpcb, but it could be that we need an |
| * inpcbinfo write lock but don't hold it. In this case, attempt to |
| * acquire using the same strategy as the TIMEWAIT case above. If we |
| * relock, we have to jump back to 'relocked' as the connection might |
| * now be in TIMEWAIT. |
| */ |
| /* |
| * samkumar: There used to be some code here for synchronization, MAC |
| * management, and debugging. |
| */ |
| |
| /* |
| * When the socket is accepting connections (the INPCB is in LISTEN |
| * state) we look into the SYN cache if this is a new connection |
| * attempt or the completion of a previous one. Instead of checking |
| * so->so_options to check if the socket is listening, we rely on the |
| * arguments passed to this function (if tp == NULL, then tpl is not NULL |
| * and is the matching listen socket). |
| */ |
| |
| if (/*so->so_options & SO_ACCEPTCONN*/tp == NULL) { |
| /* samkumar: NULL check isn't needed but prevents a compiler warning */ |
| KASSERT(tpl != NULL && tpl->t_state == TCP6S_LISTEN, ("listen socket must be in listening state!")); |
| |
| /* |
| * samkumar: There used to be some code here that checks if the |
| * received segment is an ACK, and if so, searches the SYN cache to |
| * find an entry whose connection establishment handshake this segment |
| * completes. If such an entry is found, then a socket is created and |
| * then tcp_do_segment is called to actually run the code to mark the |
| * connection as established. If the received segment is an RST, then |
| * that is processed in the syncache as well. In TCPlp we do not use a |
| * SYN cache, so I've removed that code. The actual connection |
| * establishment/processing logic happens in tcp_do_segment anyway, |
| * which is called at the bottom of this function, so there's no need |
| * to rewrite this code with special-case logic for that. |
| */ |
| |
| /* |
| * We can't do anything without SYN. |
| */ |
| if ((thflags & TH_SYN) == 0) { |
| /* |
| * samkumar: Here, and in several other instances, the FreeBSD |
| * code would call tcp_log_addrs. Improving logging in these |
| * edge cases in TCPlp is left for the future --- for now, I just |
| * put "<addrs go here>" where the address string would go. |
| */ |
| tcplp_sys_log("%s; %s: Listen socket: " |
| "SYN is missing, segment ignored", |
| "<addrs go here>", __func__); |
| goto dropunlock; |
| } |
| /* |
| * (SYN|ACK) is bogus on a listen socket. |
| */ |
| if (thflags & TH_ACK) { |
| /* samkumar: See above comment regarding tcp_log_addrs. */ |
| tcplp_sys_log("%s; %s: Listen socket: " |
| "SYN|ACK invalid, segment rejected", |
| "<addrs go here>", __func__); |
| /* samkumar: Removed call to syncache_badack(&inc); */ |
| rstreason = BANDLIM_RST_OPENPORT; |
| goto dropwithreset; |
| } |
| /* |
| * If the drop_synfin option is enabled, drop all |
| * segments with both the SYN and FIN bits set. |
| * This prevents e.g. nmap from identifying the |
| * TCP/IP stack. |
| * XXX: Poor reasoning. nmap has other methods |
| * and is constantly refining its stack detection |
| * strategies. |
| * XXX: This is a violation of the TCP specification |
| * and was used by RFC1644. |
| */ |
| if ((thflags & TH_FIN) && V_drop_synfin) { |
| /* samkumar: See above comment regarding tcp_log_addrs. */ |
| tcplp_sys_log("%s; %s: Listen socket: " |
| "SYN|FIN segment ignored (based on " |
| "sysctl setting)", "<addrs go here>", __func__); |
| goto dropunlock; |
| } |
| /* |
| * Segment's flags are (SYN) or (SYN|FIN). |
| * |
| * TH_PUSH, TH_URG, TH_ECE, TH_CWR are ignored |
| * as they do not affect the state of the TCP FSM. |
| * The data pointed to by TH_URG and th_urp is ignored. |
| */ |
| KASSERT((thflags & (TH_RST|TH_ACK)) == 0, |
| ("%s: Listen socket: TH_RST or TH_ACK set", __func__)); |
| KASSERT(thflags & (TH_SYN), |
| ("%s: Listen socket: TH_SYN not set", __func__)); |
| |
| /* |
| * samkumar: There used to be some code here to reject incoming |
| * SYN packets for deprecated interface addresses unless |
| * V_ip6_use_deprecated is true. Rejecting the packet, in this case, |
| * means to "goto dropwithreset". I removed this functionality. |
| */ |
| |
| /* |
| * Basic sanity checks on incoming SYN requests: |
| * Don't respond if the destination is a link layer |
| * broadcast according to RFC1122 4.2.3.10, p. 104. |
| * If it is from this socket it must be forged. |
| * Don't respond if the source or destination is a |
| * global or subnet broad- or multicast address. |
| * Note that it is quite possible to receive unicast |
| * link-layer packets with a broadcast IP address. Use |
| * in_broadcast() to find them. |
| */ |
| |
| /* |
| * samkumar: There used to be a sanity check that drops (via |
| * "goto dropunlock") any broadcast or multicast packets. This check is |
| * done by checking m->m_flags for (M_BAST|M_MCAST). The original |
| * FreeBSD code for this has been removed (since checking m->m_flags |
| * isn't really useful to us anyway). Note that other FreeBSD code that |
| * checks for multicast source/destination addresses is retained below |
| * (but only for the IPv6 case; the original FreeBSD code also handled |
| * it for IPv4 addresses). |
| */ |
| |
| if (th->th_dport == th->th_sport && |
| IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) { |
| /* samkumar: See above comment regarding tcp_log_addrs. */ |
| tcplp_sys_log("%s; %s: Listen socket: " |
| "Connection attempt to/from self " |
| "ignored", "<addrs go here>", __func__); |
| goto dropunlock; |
| } |
| if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || |
| IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) { |
| /* samkumar: See above comment regarding tcp_log_addrs. */ |
| tcplp_sys_log("%s; %s: Listen socket: " |
| "Connection attempt from/to multicast " |
| "address ignored", "<addrs go here>", __func__); |
| goto dropunlock; |
| } |
| |
| /* |
| * samkumar: The FreeBSD code would call |
| * syncache_add(&inc, &to, th, inp, &so, m, NULL, NULL); |
| * to add an entry to the SYN cache at this point. TCPlp doesn't use a |
| * syncache, so we initialize the new socket right away. The code to |
| * initialize the socket is taken from the syncache_socket function. |
| */ |
| |
| tcp_dooptions(&to, optp, optlen, TO_SYN); |
| tp = tcplp_sys_accept_ready(tpl, &ip6->ip6_dst, th->th_sport); // Try to allocate an active socket to accept into |
| if (tp == NULL) { |
| /* If we couldn't allocate, just ignore the SYN. */ |
| return IPPROTO_DONE; |
| } |
| if (tp == (struct tcpcb *) -1) { |
| rstreason = ECONNREFUSED; |
| goto dropwithreset; |
| } |
| tcp_state_change(tp, TCPS_SYN_RECEIVED); |
| tpmarkpassiveopen(tp); |
| tp->t_flags |= TF_ACKNOW; // samkumar: my addition |
| tp->iss = tcp_new_isn(tp); |
| tp->irs = th->th_seq; |
| tcp_rcvseqinit(tp); |
| tcp_sendseqinit(tp); |
| tp->snd_wl1 = th->th_seq; |
| tp->snd_max = tp->iss/* + 1*/; |
| tp->snd_nxt = tp->iss/* + 1*/; |
| tp->rcv_up = th->th_seq + 1; |
| tp->rcv_wnd = imin(imax(cbuf_free_space(&tp->recvbuf), 0), TCP_MAXWIN); |
| tp->rcv_adv += tp->rcv_wnd; |
| tp->last_ack_sent = tp->rcv_nxt; |
| memcpy(&tp->laddr, &ip6->ip6_dst, sizeof(tp->laddr)); |
| memcpy(&tp->faddr, &ip6->ip6_src, sizeof(tp->faddr)); |
| tp->fport = th->th_sport; |
| tp->lport = tpl->lport; |
| |
| /* |
| * samkumar: Several of the checks below (taken from syncache_socket!) |
| * check for flags in sc->sc_flags. They have been written to directly |
| * check for the conditions on the TCP options structure or in the TCP |
| * header that would ordinarily be used to set flags in sc->sc_flags |
| * when adding an entry to the SYN cache. |
| * |
| * In effect, we combine the logic in syncache_add to set elements of |
| * sc with the logic in syncache_socket to transfer state from sc |
| * to the socket, but short-circuit the process to avoid ever storing |
| * data in sc. Since this isn't just adding or deleting code, I decided |
| * that it's better to keep comments indicating exactly how I composed |
| * these two functions. |
| */ |
| tp->t_flags = tp->t_flags & (TF_NOPUSH | TF_NODELAY | TF_NOOPT); |
| // tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY); |
| // if (sc->sc_flags & SCF_NOOPT) |
| // tp->t_flags |= TF_NOOPT; |
| // else { |
| if (!(tp->t_flags & TF_NOOPT) && V_tcp_do_rfc1323) { |
| if (/*sc->sc_flags & SCF_WINSCALE*/to.to_flags & TOF_SCALE) { |
| int wscale = 0; |
| |
| /* |
| * Pick the smallest possible scaling factor that |
| * will still allow us to scale up to sb_max, aka |
| * kern.ipc.maxsockbuf. |
| * |
| * We do this because there are broken firewalls that |
| * will corrupt the window scale option, leading to |
| * the other endpoint believing that our advertised |
| * window is unscaled. At scale factors larger than |
| * 5 the unscaled window will drop below 1500 bytes, |
| * leading to serious problems when traversing these |
| * broken firewalls. |
| * |
| * With the default maxsockbuf of 256K, a scale factor |
| * of 3 will be chosen by this algorithm. Those who |
| * choose a larger maxsockbuf should watch out |
| * for the compatiblity problems mentioned above. |
| * |
| * RFC1323: The Window field in a SYN (i.e., a <SYN> |
| * or <SYN,ACK>) segment itself is never scaled. |
| */ |
| |
| /* |
| * samkumar: The original logic, taken from syncache_add, is |
| * listed below, commented out. In practice, we just use |
| * wscale = 0 because in TCPlp we assume that the buffers |
| * aren't big enough for window scaling to be all that useful. |
| */ |
| #if 0 |
| while (wscale < TCP_MAX_WINSHIFT && |
| (TCP_MAXWIN << wscale) < sb_max) |
| wscale++; |
| #endif |
| |
| tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE; |
| tp->snd_scale = /*sc->sc_requested_s_scale*/to.to_wscale; |
| tp->request_r_scale = wscale; |
| } |
| if (/*sc->sc_flags & SCF_TIMESTAMP*/to.to_flags & TOF_TS) { |
| tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP; |
| tp->ts_recent = /*sc->sc_tsreflect*/to.to_tsval; |
| tp->ts_recent_age = tcp_ts_getticks(); |
| tp->ts_offset = /*sc->sc_tsoff*/0; // No syncookies, so this should always be 0 |
| } |
| |
| /* |
| * samkumar: there used to be code here that would set the |
| * TF_SIGNATURE flag on tp->t_flags if SCF_SIGNATURE is set on |
| * sc->sc_flags. I've left it in below, commented out. |
| */ |
| #if 0 |
| #ifdef TCP_SIGNATURE |
| if (sc->sc_flags & SCF_SIGNATURE) |
| tp->t_flags |= TF_SIGNATURE; |
| #endif |
| #endif |
| if (/*sc->sc_flags & SCF_SACK*/ to.to_flags & TOF_SACKPERM) |
| tp->t_flags |= TF_SACK_PERMIT; |
| } |
| if (/*sc->sc_flags & SCF_ECN*/(th->th_flags & (TH_ECE|TH_CWR)) && V_tcp_do_ecn) |
| tp->t_flags |= TF_ECN_PERMIT; |
| |
| /* |
| * Set up MSS and get cached values from tcp_hostcache. |
| * This might overwrite some of the defaults we just set. |
| */ |
| tcp_mss(tp, /*sc->sc_peer_mss*/(to.to_flags & TOF_MSS) ? to.to_mss : 0); |
| |
| tcp_output(tp); // to send the SYN-ACK |
| |
| tp->accepted_from = tpl; |
| return (IPPROTO_DONE); |
| } else if (tp->t_state == TCPS_LISTEN) { |
| /* |
| * When a listen socket is torn down the SO_ACCEPTCONN |
| * flag is removed first while connections are drained |
| * from the accept queue in a unlock/lock cycle of the |
| * ACCEPT_LOCK, opening a race condition allowing a SYN |
| * attempt go through unhandled. |
| */ |
| goto dropunlock; |
| } |
| |
| KASSERT(tp, ("tp is still NULL!")); |
| |
| /* |
| * samkumar: There used to be code here to verify TCP signatures. We don't |
| * support TCP signatures in TCPlp. |
| */ |
| |
| /* |
| * Segment belongs to a connection in SYN_SENT, ESTABLISHED or later |
| * state. tcp_do_segment() always consumes the mbuf chain, unlocks |
| * the inpcb, and unlocks pcbinfo. |
| */ |
| tcp_do_segment(ip6, th, msg, tp, drop_hdrlen, tlen, iptos, sig); |
| return (IPPROTO_DONE); |
| |
| /* |
| * samkumar: Removed some locking and debugging code under all three of |
| * these labels: dropwithreset, dropunlock, and drop. I also removed some |
| * memory management code (e.g., calling m_freem(m) if m != NULL) since |
| * the caller of this function will take care of that kind of memory |
| * management in TCPlp. |
| */ |
| dropwithreset: |
| |
| /* |
| * samkumar: The check against inp != NULL is now a check on tp != NULL. |
| */ |
| if (tp != NULL) { |
| tcp_dropwithreset(ip6, th, tp, tp->instance, tlen, rstreason); |
| } else |
| tcp_dropwithreset(ip6, th, NULL, tpl->instance, tlen, rstreason); |
| goto drop; |
| |
| dropunlock: |
| drop: |
| return (IPPROTO_DONE); |
| } |
| |
| /* |
| * samkumar: Original signature |
| * static void |
| * tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so, |
| * struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos, |
| * int ti_locked) |
| */ |
| static void |
| tcp_do_segment(struct ip6_hdr* ip6, struct tcphdr *th, otMessage* msg, |
| struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos, |
| struct tcplp_signals* sig) |
| { |
| /* |
| * samkumar: All code pertaining to locks, stats, and debug has been |
| * removed from this function. |
| */ |
| |
| int thflags, acked, ourfinisacked, needoutput = 0; |
| int rstreason, todrop, win; |
| uint64_t tiwin; |
| struct tcpopt to; |
| uint32_t ticks = tcplp_sys_get_ticks(); |
| otInstance* instance = tp->instance; |
| thflags = th->th_flags; |
| tp->sackhint.last_sack_ack = 0; |
| |
| /* |
| * If this is either a state-changing packet or current state isn't |
| * established, we require a write lock on tcbinfo. Otherwise, we |
| * allow the tcbinfo to be in either alocked or unlocked, as the |
| * caller may have unnecessarily acquired a write lock due to a race. |
| */ |
| |
| /* samkumar: There used to be synchronization code here. */ |
| KASSERT(tp->t_state > TCPS_LISTEN, ("%s: TCPS_LISTEN", |
| __func__)); |
| KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: TCPS_TIME_WAIT", |
| __func__)); |
| |
| /* |
| * Segment received on connection. |
| * Reset idle time and keep-alive timer. |
| * XXX: This should be done after segment |
| * validation to ignore broken/spoofed segs. |
| */ |
| tp->t_rcvtime = ticks; |
| if (TCPS_HAVEESTABLISHED(tp->t_state)) |
| tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp)); |
| |
| /* |
| * Scale up the window into a 32-bit value. |
| * For the SYN_SENT state the scale is zero. |
| */ |
| tiwin = th->th_win << tp->snd_scale; |
| |
| /* |
| * TCP ECN processing. |
| */ |
| /* |
| * samkumar: I intentionally left the TCPSTAT_INC lines below commented |
| * out, to avoid altering the structure of the code too much by |
| * reorganizing the switch statement. |
| */ |
| if (tp->t_flags & TF_ECN_PERMIT) { |
| if (thflags & TH_CWR) |
| tp->t_flags &= ~TF_ECN_SND_ECE; |
| switch (iptos & IPTOS_ECN_MASK) { |
| case IPTOS_ECN_CE: |
| tp->t_flags |= TF_ECN_SND_ECE; |
| //TCPSTAT_INC(tcps_ecn_ce); |
| break; |
| case IPTOS_ECN_ECT0: |
| //TCPSTAT_INC(tcps_ecn_ect0); |
| break; |
| case IPTOS_ECN_ECT1: |
| //TCPSTAT_INC(tcps_ecn_ect1); |
| break; |
| } |
| |
| /* Process a packet differently from RFC3168. */ |
| cc_ecnpkt_handler(tp, th, iptos); |
| |
| /* Congestion experienced. */ |
| if (thflags & TH_ECE) { |
| cc_cong_signal(tp, th, CC_ECN); |
| } |
| } |
| |
| /* |
| * Parse options on any incoming segment. |
| */ |
| tcp_dooptions(&to, (uint8_t *)(th + 1), |
| ((th->th_off_x2 >> TH_OFF_SHIFT) << 2) - sizeof(struct tcphdr), |
| (thflags & TH_SYN) ? TO_SYN : 0); |
| |
| /* |
| * If echoed timestamp is later than the current time, |
| * fall back to non RFC1323 RTT calculation. Normalize |
| * timestamp if syncookies were used when this connection |
| * was established. |
| */ |
| |
| if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) { |
| to.to_tsecr -= tp->ts_offset; |
| if (TSTMP_GT(to.to_tsecr, tcp_ts_getticks())) |
| to.to_tsecr = 0; |
| } |
| /* |
| * If timestamps were negotiated during SYN/ACK they should |
| * appear on every segment during this session and vice versa. |
| */ |
| if ((tp->t_flags & TF_RCVD_TSTMP) && !(to.to_flags & TOF_TS)) { |
| /* samkumar: See above comment regarding tcp_log_addrs. */ |
| tcplp_sys_log("%s; %s: Timestamp missing, " |
| "no action", "<addrs go here>", __func__); |
| } |
| if (!(tp->t_flags & TF_RCVD_TSTMP) && (to.to_flags & TOF_TS)) { |
| /* samkumar: See above comment regarding tcp_log_addrs. */ |
| tcplp_sys_log("%s; %s: Timestamp not expected, " |
| "no action", "<addrs go here>", __func__); |
| } |
| |
| /* |
| * Process options only when we get SYN/ACK back. The SYN case |
| * for incoming connections is handled in tcp_syncache. |
| * According to RFC1323 the window field in a SYN (i.e., a <SYN> |
| * or <SYN,ACK>) segment itself is never scaled. |
| * XXX this is traditional behavior, may need to be cleaned up. |
| */ |
| if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { |
| if ((to.to_flags & TOF_SCALE) && |
| (tp->t_flags & TF_REQ_SCALE)) { |
| tp->t_flags |= TF_RCVD_SCALE; |
| tp->snd_scale = to.to_wscale; |
| } |
| /* |
| * Initial send window. It will be updated with |
| * the next incoming segment to the scaled value. |
| */ |
| tp->snd_wnd = th->th_win; |
| if (to.to_flags & TOF_TS) { |
| tp->t_flags |= TF_RCVD_TSTMP; |
| tp->ts_recent = to.to_tsval; |
| tp->ts_recent_age = tcp_ts_getticks(); |
| } |
| if (to.to_flags & TOF_MSS) |
| tcp_mss(tp, to.to_mss); |
| if ((tp->t_flags & TF_SACK_PERMIT) && |
| (to.to_flags & TOF_SACKPERM) == 0) |
| tp->t_flags &= ~TF_SACK_PERMIT; |
| } |
| /* |
| * Header prediction: check for the two common cases |
| * of a uni-directional data xfer. If the packet has |
| * no control flags, is in-sequence, the window didn't |
| * change and we're not retransmitting, it's a |
| * candidate. If the length is zero and the ack moved |
| * forward, we're the sender side of the xfer. Just |
| * free the data acked & wake any higher level process |
| * that was blocked waiting for space. If the length |
| * is non-zero and the ack didn't move, we're the |
| * receiver side. If we're getting packets in-order |
| * (the reassembly queue is empty), add the data to |
| * the socket buffer and note that we need a delayed ack. |
| * Make sure that the hidden state-flags are also off. |
| * Since we check for TCPS_ESTABLISHED first, it can only |
| * be TH_NEEDSYN. |
| */ |
| /* |
| * samkumar: Replaced LIST_EMPTY(&tp->tsegq with the call to bmp_isempty). |
| */ |
| if (tp->t_state == TCPS_ESTABLISHED && |
| th->th_seq == tp->rcv_nxt && |
| (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && |
| tp->snd_nxt == tp->snd_max && |
| tiwin && tiwin == tp->snd_wnd && |
| ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && |
| bmp_isempty(tp->reassbmp, REASSBMP_SIZE(tp)) && |
| ((to.to_flags & TOF_TS) == 0 || |
| TSTMP_GEQ(to.to_tsval, tp->ts_recent)) ) { |
| |
| /* |
| * If last ACK falls within this segment's sequence numbers, |
| * record the timestamp. |
| * NOTE that the test is modified according to the latest |
| * proposal of the tcplw@cray.com list (Braden 1993/04/26). |
| */ |
| if ((to.to_flags & TOF_TS) != 0 && |
| SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { |
| tp->ts_recent_age = tcp_ts_getticks(); |
| tp->ts_recent = to.to_tsval; |
| } |
| |
| if (tlen == 0) { |
| if (SEQ_GT(th->th_ack, tp->snd_una) && |
| SEQ_LEQ(th->th_ack, tp->snd_max) && |
| !IN_RECOVERY(tp->t_flags) && |
| (to.to_flags & TOF_SACK) == 0 && |
| TAILQ_EMPTY(&tp->snd_holes)) { |
| /* |
| * This is a pure ack for outstanding data. |
| */ |
| |
| /* |
| * "bad retransmit" recovery. |
| */ |
| if (tp->t_rxtshift == 1 && |
| tp->t_flags & TF_PREVVALID && |
| (int)(ticks - tp->t_badrxtwin) < 0) { |
| cc_cong_signal(tp, th, CC_RTO_ERR); |
| } |
| |
| /* |
| * Recalculate the transmit timer / rtt. |
| * |
| * Some boxes send broken timestamp replies |
| * during the SYN+ACK phase, ignore |
| * timestamps of 0 or we could calculate a |
| * huge RTT and blow up the retransmit timer. |
| */ |
| |
| if ((to.to_flags & TOF_TS) != 0 && |
| to.to_tsecr) { |
| uint32_t t; |
| |
| t = tcp_ts_getticks() - to.to_tsecr; |
| if (!tp->t_rttlow || tp->t_rttlow > t) |
| tp->t_rttlow = t; |
| tcp_xmit_timer(tp, |
| TCP_TS_TO_TICKS(t) + 1); |
| } else if (tp->t_rtttime && |
| SEQ_GT(th->th_ack, tp->t_rtseq)) { |
| if (!tp->t_rttlow || |
| tp->t_rttlow > ticks - tp->t_rtttime) |
| tp->t_rttlow = ticks - tp->t_rtttime; |
| tcp_xmit_timer(tp, |
| ticks - tp->t_rtttime); |
| } |
| |
| acked = BYTES_THIS_ACK(tp, th); |
| |
| /* |
| * samkumar: Replaced sbdrop(&so->so_snd, acked) with this call |
| * to lbuf_pop. |
| */ |
| { |
| uint32_t poppedbytes = lbuf_pop(&tp->sendbuf, acked, &sig->links_popped); |
| KASSERT(poppedbytes == acked, ("More bytes were acked than are in the send buffer")); |
| sig->bytes_acked += poppedbytes; |
| } |
| if (SEQ_GT(tp->snd_una, tp->snd_recover) && |
| SEQ_LEQ(th->th_ack, tp->snd_recover)) |
| tp->snd_recover = th->th_ack - 1; |
| |
| /* |
| * Let the congestion control algorithm update |
| * congestion control related information. This |
| * typically means increasing the congestion |
| * window. |
| */ |
| cc_ack_received(tp, th, CC_ACK); |
| |
| tp->snd_una = th->th_ack; |
| /* |
| * Pull snd_wl2 up to prevent seq wrap relative |
| * to th_ack. |
| */ |
| tp->snd_wl2 = th->th_ack; |
| tp->t_dupacks = 0; |
| |
| /* |
| * If all outstanding data are acked, stop |
| * retransmit timer, otherwise restart timer |
| * using current (possibly backed-off) value. |
| * If process is waiting for space, |
| * wakeup/selwakeup/signal. If data |
| * are ready to send, let tcp_output |
| * decide between more output or persist. |
| */ |
| |
| if (tp->snd_una == tp->snd_max) |
| tcp_timer_activate(tp, TT_REXMT, 0); |
| else if (!tcp_timer_active(tp, TT_PERSIST)) |
| tcp_timer_activate(tp, TT_REXMT, |
| tp->t_rxtcur); |
| |
| /* |
| * samkumar: There used to be a call to sowwakeup(so); here, |
| * which wakes up any threads waiting for the socket to |
| * become ready for writing. TCPlp handles its send buffer |
| * differently so we do not need to replace this call with |
| * specialized code to handle this. |
| */ |
| |
| /* |
| * samkumar: Replaced sbavail(&so->so_snd) with this call to |
| * lbuf_used_space. |
| */ |
| if (lbuf_used_space(&tp->sendbuf)) |
| (void) tcp_output(tp); |
| goto check_delack; |
| } |
| } else if (th->th_ack == tp->snd_una && |
| /* |
| * samkumar: Replaced sbspace(&so->so_rcv) with this call to |
| * cbuf_free_space. |
| */ |
| tlen <= cbuf_free_space(&tp->recvbuf)) { |
| |
| /* |
| * This is a pure, in-sequence data packet with |
| * nothing on the reassembly queue and we have enough |
| * buffer space to take it. |
| */ |
| /* Clean receiver SACK report if present */ |
| if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks) |
| tcp_clean_sackreport(tp); |
| |
| tp->rcv_nxt += tlen; |
| /* |
| * Pull snd_wl1 up to prevent seq wrap relative to |
| * th_seq. |
| */ |
| tp->snd_wl1 = th->th_seq; |
| /* |
| * Pull rcv_up up to prevent seq wrap relative to |
| * rcv_nxt. |
| */ |
| tp->rcv_up = tp->rcv_nxt; |
| |
| /* |
| * Automatic sizing of receive socket buffer. Often the send |
| * buffer size is not optimally adjusted to the actual network |
| * conditions at hand (delay bandwidth product). Setting the |
| * buffer size too small limits throughput on links with high |
| * bandwidth and high delay (eg. trans-continental/oceanic links). |
| * |
| * On the receive side the socket buffer memory is only rarely |
| * used to any significant extent. This allows us to be much |
| * more aggressive in scaling the receive socket buffer. For |
| * the case that the buffer space is actually used to a large |
| * extent and we run out of kernel memory we can simply drop |
| * the new segments; TCP on the sender will just retransmit it |
| * later. Setting the buffer size too big may only consume too |
| * much kernel memory if the application doesn't read() from |
| * the socket or packet loss or reordering makes use of the |
| * reassembly queue. |
| * |
| * The criteria to step up the receive buffer one notch are: |
| * 1. Application has not set receive buffer size with |
| * SO_RCVBUF. Setting SO_RCVBUF clears SB_AUTOSIZE. |
| * 2. the number of bytes received during the time it takes |
| * one timestamp to be reflected back to us (the RTT); |
| * 3. received bytes per RTT is within seven eighth of the |
| * current socket buffer size; |
| * 4. receive buffer size has not hit maximal automatic size; |
| * |
| * This algorithm does one step per RTT at most and only if |
| * we receive a bulk stream w/o packet losses or reorderings. |
| * Shrinking the buffer during idle times is not necessary as |
| * it doesn't consume any memory when idle. |
| * |
| * TODO: Only step up if the application is actually serving |
| * the buffer to better manage the socket buffer resources. |
| */ |
| |
| /* |
| * samkumar: There used to be code here to dynamically size the |
| * receive buffer (tp->rfbuf_ts, rp->rfbuf_cnt, and the local |
| * newsize variable). In TCPlp, we don't support this, as the user |
| * allocates the receive buffer and its size can't be changed here. |
| * Therefore, I removed the code that does this. Note that the |
| * actual resizing of the buffer is done using sbreserve_locked, |
| * whose call comes later (not exactly where this comment is). |
| */ |
| |
| /* Add data to socket buffer. */ |
| |
| /* |
| * samkumar: The code that was here would just free the mbuf |
| * (with m_freem(m)) if SBS_CANTRCVMORE is set in |
| * so->so_rcv.sb_state. Otherwise, it would cut drop_hdrlen bytes |
| * from the mbuf (using m_adj(m, drop_hdrlen)) to discard the |
| * headers and then append the mbuf to the receive buffer using |
| * sbappendstream_locked(&so->so_rcv, m, 0). I've rewritten this |
| * to work the TCPlp way. The check to so->so_rcv.sb_state is |
| * replaced by a tcpiscantrcv call, and we copy bytes into |
| * TCPlp's circular buffer (since we designed it to avoid |
| * having dynamically-allocated memory for the receive buffer). |
| */ |
| |
| if (!tpiscantrcv(tp)) { |
| cbuf_write(&tp->recvbuf, msg, otMessageGetOffset(msg) + drop_hdrlen, tlen, cbuf_copy_from_message); |
| if (tlen > 0) { |
| sig->recvbuf_added = true; |
| } |
| } else { |
| /* |
| * samkumar: We already know tlen != 0, so if we got here, then |
| * it means that we got data after we called SHUT_RD, or after |
| * receiving a FIN. I'm going to drop the connection in this |
| * case. I think FreeBSD might have just dropped the packet |
| * silently, but Linux handles it this way; this seems to be |
| * the right approach to me. |
| */ |
| tcp_drop(tp, ECONNABORTED); |
| goto drop; |
| } |
| /* NB: sorwakeup_locked() does an implicit unlock. */ |
| /* |
| * samkumar: There used to be a call to sorwakeup_locked(so); here, |
| * which wakes up any threads waiting for the socket to become |
| * become ready for reading. TCPlp handles its buffering |
| * differently so we do not need to replace this call with |
| * specialized code to handle this. |
| */ |
| if (DELAY_ACK(tp, tlen)) { |
| tp->t_flags |= TF_DELACK; |
| } else { |
| tp->t_flags |= TF_ACKNOW; |
| tcp_output(tp); |
| } |
| goto check_delack; |
| } |
| } |
| |
| /* |
| * Calculate amount of space in receive window, |
| * and then do TCP input processing. |
| * Receive window is amount of space in rcv queue, |
| * but not less than advertised window. |
| */ |
| /* samkumar: Replaced sbspace(&so->so_rcv) with call to cbuf_free_space. */ |
| win = cbuf_free_space(&tp->recvbuf); |
| if (win < 0) |
| win = 0; |
| tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); |
| |
| /* Reset receive buffer auto scaling when not in bulk receive mode. */ |
| /* samkumar: Removed this receive buffer autoscaling code. */ |
| |
| switch (tp->t_state) { |
| |
| /* |
| * If the state is SYN_RECEIVED: |
| * if seg contains an ACK, but not for our SYN/ACK, send a RST. |
| * (Added by Sam) if seg is resending the original SYN, resend the SYN/ACK |
| */ |
| /* |
| * samkumar: If we receive a retransmission of the original SYN, then |
| * resend the SYN/ACK segment. This case was probably handled by the |
| * SYN cache. Because TCPlp does not use a SYN cache, we need to write |
| * custom logic for it. It is handled in the "else if" clause below. |
| */ |
| case TCPS_SYN_RECEIVED: |
| if ((thflags & TH_ACK) && |
| (SEQ_LEQ(th->th_ack, tp->snd_una) || |
| SEQ_GT(th->th_ack, tp->snd_max))) { |
| rstreason = BANDLIM_RST_OPENPORT; |
| goto dropwithreset; |
| } else if ((thflags & TH_SYN) && !(thflags & TH_ACK) && (th->th_seq == tp->irs)) { |
| tp->t_flags |= TF_ACKNOW; |
| } |
| break; |
| |
| /* |
| * If the state is SYN_SENT: |
| * if seg contains an ACK, but not for our SYN, drop the input. |
| * if seg contains a RST, then drop the connection. |
| * if seg does not contain SYN, then drop it. |
| * Otherwise this is an acceptable SYN segment |
| * initialize tp->rcv_nxt and tp->irs |
| * if seg contains ack then advance tp->snd_una |
| * if seg contains an ECE and ECN support is enabled, the stream |
| * is ECN capable. |
| * if SYN has been acked change to ESTABLISHED else SYN_RCVD state |
| * arrange for segment to be acked (eventually) |
| * continue processing rest of data/controls, beginning with URG |
| */ |
| case TCPS_SYN_SENT: |
| if ((thflags & TH_ACK) && |
| (SEQ_LEQ(th->th_ack, tp->iss) || |
| SEQ_GT(th->th_ack, tp->snd_max))) { |
| rstreason = BANDLIM_UNLIMITED; |
| goto dropwithreset; |
| } |
| if ((thflags & (TH_ACK|TH_RST)) == (TH_ACK|TH_RST)) { |
| tp = tcp_drop(tp, ECONNREFUSED); |
| } |
| if (thflags & TH_RST) |
| goto drop; |
| if (!(thflags & TH_SYN)) |
| goto drop; |
| |
| tp->irs = th->th_seq; |
| tcp_rcvseqinit(tp); |
| if (thflags & TH_ACK) { |
| /* |
| * samkumar: Removed call to soisconnected(so), since TCPlp has its |
| * own buffering. |
| */ |
| |
| /* Do window scaling on this connection? */ |
| if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == |
| (TF_RCVD_SCALE|TF_REQ_SCALE)) { |
| tp->rcv_scale = tp->request_r_scale; |
| } |
| tp->rcv_adv += imin(tp->rcv_wnd, |
| TCP_MAXWIN << tp->rcv_scale); |
| tp->snd_una++; /* SYN is acked */ |
| /* |
| * If there's data, delay ACK; if there's also a FIN |
| * ACKNOW will be turned on later. |
| */ |
| if (DELAY_ACK(tp, tlen) && tlen != 0) |
| tcp_timer_activate(tp, TT_DELACK, |
| tcp_delacktime); |
| else |
| tp->t_flags |= TF_ACKNOW; |
| |
| if ((thflags & TH_ECE) && V_tcp_do_ecn) { |
| tp->t_flags |= TF_ECN_PERMIT; |
| } |
| |
| /* |
| * Received <SYN,ACK> in SYN_SENT[*] state. |
| * Transitions: |
| * SYN_SENT --> ESTABLISHED |
| * SYN_SENT* --> FIN_WAIT_1 |
| */ |
| tp->t_starttime = ticks; |
| if (tp->t_flags & TF_NEEDFIN) { |
| tcp_state_change(tp, TCPS_FIN_WAIT_1); |
| tp->t_flags &= ~TF_NEEDFIN; |
| thflags &= ~TH_SYN; |
| } else { |
| tcp_state_change(tp, TCPS_ESTABLISHED); |
| /* samkumar: Set conn_established signal for TCPlp. */ |
| sig->conn_established = true; |
| cc_conn_init(tp); |
| tcp_timer_activate(tp, TT_KEEP, |
| TP_KEEPIDLE(tp)); |
| } |
| } else { |
| /* |
| * Received initial SYN in SYN-SENT[*] state => |
| * simultaneous open. |
| * If it succeeds, connection is * half-synchronized. |
| * Otherwise, do 3-way handshake: |
| * SYN-SENT -> SYN-RECEIVED |
| * SYN-SENT* -> SYN-RECEIVED* |
| */ |
| tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); |
| tcp_timer_activate(tp, TT_REXMT, 0); |
| tcp_state_change(tp, TCPS_SYN_RECEIVED); |
| /* |
| * samkumar: We would have incremented snd_next in tcp_output when |
| * we sent the original SYN, so decrement it here. (Another |
| * consequence of removing the SYN cache.) |
| */ |
| tp->snd_nxt--; |
| } |
| |
| /* |
| * Advance th->th_seq to correspond to first data byte. |
| * If data, trim to stay within window, |
| * dropping FIN if necessary. |
| */ |
| th->th_seq++; |
| if (tlen > tp->rcv_wnd) { |
| todrop = tlen - tp->rcv_wnd; |
| /* |
| * samkumar: I removed a call to m_adj(m, -todrop), which intends |
| * to trim the data so it fits in the window. We can just read less |
| * when copying into the receive buffer in TCPlp, so we don't need |
| * to do this. |
| */ |
| (void) todrop; /* samkumar: Prevent a compiler warning */ |
| tlen = tp->rcv_wnd; |
| thflags &= ~TH_FIN; |
| } |
| tp->snd_wl1 = th->th_seq - 1; |
| tp->rcv_up = th->th_seq; |
| /* |
| * Client side of transaction: already sent SYN and data. |
| * If the remote host used T/TCP to validate the SYN, |
| * our data will be ACK'd; if so, enter normal data segment |
| * processing in the middle of step 5, ack processing. |
| * Otherwise, goto step 6. |
| */ |
| if (thflags & TH_ACK) |
| goto process_ACK; |
| |
| goto step6; |
| |
| /* |
| * If the state is LAST_ACK or CLOSING or TIME_WAIT: |
| * do normal processing. |
| * |
| * NB: Leftover from RFC1644 T/TCP. Cases to be reused later. |
| */ |
| case TCPS_LAST_ACK: |
| case TCPS_CLOSING: |
| break; /* continue normal processing */ |
| } |
| |
| /* |
| * States other than LISTEN or SYN_SENT. |
| * First check the RST flag and sequence number since reset segments |
| * are exempt from the timestamp and connection count tests. This |
| * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix |
| * below which allowed reset segments in half the sequence space |
| * to fall though and be processed (which gives forged reset |
| * segments with a random sequence number a 50 percent chance of |
| * killing a connection). |
| * Then check timestamp, if present. |
| * Then check the connection count, if present. |
| * Then check that at least some bytes of segment are within |
| * receive window. If segment begins before rcv_nxt, |
| * drop leading data (and SYN); if nothing left, just ack. |
| */ |
| if (thflags & TH_RST) { |
| /* |
| * RFC5961 Section 3.2 |
| * |
| * - RST drops connection only if SEG.SEQ == RCV.NXT. |
| * - If RST is in window, we send challenge ACK. |
| * |
| * Note: to take into account delayed ACKs, we should |
| * test against last_ack_sent instead of rcv_nxt. |
| * Note 2: we handle special case of closed window, not |
| * covered by the RFC. |
| */ |
| if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) && |
| SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) || |
| (tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) { |
| |
| /* |
| * samkumar: This if statement used to also be prefaced with |
| * "V_tcp_insecure_rst ||". But I removed it, since there's no |
| * reason to support an insecure option in TCPlp (my guess is that |
| * FreeBSD supported it for legacy reasons). |
| */ |
| if (tp->last_ack_sent == th->th_seq) { |
| /* |
| * samkumar: Normally, the error number would be stored in |
| * so->so_error. Instead, we put it in this "droperror" local |
| * variable and then pass it to tcplp_sys_connection_lost. |
| */ |
| int droperror = 0; |
| /* Drop the connection. */ |
| switch (tp->t_state) { |
| case TCPS_SYN_RECEIVED: |
| droperror = ECONNREFUSED; |
| goto close; |
| case TCPS_ESTABLISHED: |
| case TCPS_FIN_WAIT_1: |
| case TCPS_FIN_WAIT_2: |
| case TCPS_CLOSE_WAIT: |
| droperror = ECONNRESET; |
| close: |
| tcp_state_change(tp, TCPS_CLOSED); |
| /* FALLTHROUGH */ |
| default: |
| tp = tcp_close(tp); |
| tcplp_sys_connection_lost(tp, droperror); |
| } |
| } else { |
| /* Send challenge ACK. */ |
| tcp_respond(tp, tp->instance, ip6, th, tp->rcv_nxt, tp->snd_nxt, TH_ACK); |
| tp->last_ack_sent = tp->rcv_nxt; |
| } |
| } |
| goto drop; |
| } |
| |
| /* |
| * RFC5961 Section 4.2 |
| * Send challenge ACK for any SYN in synchronized state. |
| */ |
| /* |
| * samkumar: I added the check for the SYN-RECEIVED state in this if |
| * statement (another consequence of removing the SYN cache). |
| */ |
| if ((thflags & TH_SYN) && tp->t_state != TCPS_SYN_SENT && tp->t_state != TCP6S_SYN_RECEIVED) { |
| /* |
| * samkumar: The modern way to handle this is to send a Challenge ACK. |
| * FreeBSD supports this, but it also has this V_tcp_insecure_syn |
| * options that will cause it to drop the connection if the SYN falls |
| * in the receive window. In TCPlp we *only* support Challenge ACKs |
| * (the secure way of doing it), so I've removed code for the insecure |
| * way. (Presumably the reason why FreeBSD supports the insecure way is |
| * for legacy code, which we don't really care about in TCPlp). |
| */ |
| /* Send challenge ACK. */ |
| tcplp_sys_log("Sending challenge ACK"); |
| tcp_respond(tp, tp->instance, ip6, th, tp->rcv_nxt, tp->snd_nxt, TH_ACK); |
| tp->last_ack_sent = tp->rcv_nxt; |
| goto drop; |
| } |
| |
| /* |
| * RFC 1323 PAWS: If we have a timestamp reply on this segment |
| * and it's less than ts_recent, drop it. |
| */ |
| if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && |
| TSTMP_LT(to.to_tsval, tp->ts_recent)) { |
| |
| /* Check to see if ts_recent is over 24 days old. */ |
| if (tcp_ts_getticks() - tp->ts_recent_age > TCP_PAWS_IDLE) { |
| /* |
| * Invalidate ts_recent. If this segment updates |
| * ts_recent, the age will be reset later and ts_recent |
| * will get a valid value. If it does not, setting |
| * ts_recent to zero will at least satisfy the |
| * requirement that zero be placed in the timestamp |
| * echo reply when ts_recent isn't valid. The |
| * age isn't reset until we get a valid ts_recent |
| * because we don't want out-of-order segments to be |
| * dropped when ts_recent is old. |
| */ |
| tp->ts_recent = 0; |
| } else { |
| if (tlen) |
| goto dropafterack; |
| goto drop; |
| } |
| } |
| |
| /* |
| * In the SYN-RECEIVED state, validate that the packet belongs to |
| * this connection before trimming the data to fit the receive |
| * window. Check the sequence number versus IRS since we know |
| * the sequence numbers haven't wrapped. This is a partial fix |
| * for the "LAND" DoS attack. |
| */ |
| if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { |
| rstreason = BANDLIM_RST_OPENPORT; |
| goto dropwithreset; |
| } |
| |
| todrop = tp->rcv_nxt - th->th_seq; |
| if (todrop > 0) { |
| if (thflags & TH_SYN) { |
| thflags &= ~TH_SYN; |
| th->th_seq++; |
| if (th->th_urp > 1) |
| th->th_urp--; |
| else |
| thflags &= ~TH_URG; |
| todrop--; |
| } |
| /* |
| * Following if statement from Stevens, vol. 2, p. 960. |
| */ |
| if (todrop > tlen |
| || (todrop == tlen && (thflags & TH_FIN) == 0)) { |
| /* |
| * Any valid FIN must be to the left of the window. |
| * At this point the FIN must be a duplicate or out |
| * of sequence; drop it. |
| */ |
| thflags &= ~TH_FIN; |
| |
| /* |
| * Send an ACK to resynchronize and drop any data. |
| * But keep on processing for RST or ACK. |
| */ |
| tp->t_flags |= TF_ACKNOW; |
| todrop = tlen; |
| } |
| /* samkumar: There was an else case that only collected stats. */ |
| drop_hdrlen += todrop; /* drop from the top afterwards */ |
| th->th_seq += todrop; |
| tlen -= todrop; |
| if (th->th_urp > todrop) |
| th->th_urp -= todrop; |
| else { |
| thflags &= ~TH_URG; |
| th->th_urp = 0; |
| } |
| } |
| |
| /* |
| * If new data are received on a connection after the |
| * user processes are gone, then RST the other end. |
| */ |
| /* |
| * samkumar: TCPlp is designed for embedded systems where there is no |
| * concept of a "process" that has allocated a TCP socket. Therefore, we |
| * do not implement the functionality in the above comment (the code for |
| * it used to be here, and I removed it). |
| */ |
| /* |
| * If segment ends after window, drop trailing data |
| * (and PUSH and FIN); if nothing left, just ACK. |
| */ |
| todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); |
| if (todrop > 0) { |
| if (todrop >= tlen) { |
| /* |
| * If window is closed can only take segments at |
| * window edge, and have to drop data and PUSH from |
| * incoming segments. Continue processing, but |
| * remember to ack. Otherwise, drop segment |
| * and ack. |
| */ |
| if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { |
| tp->t_flags |= TF_ACKNOW; |
| } else |
| goto dropafterack; |
| } |
| /* |
| * samkumar: I removed a call to m_adj(m, -todrop), which intends |
| * to trim the data so it fits in the window. We can just read less |
| * when copying into the receive buffer in TCPlp, so we don't need |
| * to do this. Subtracting it from tlen gives us enough information to |
| * do this later. In FreeBSD, this isn't possible because the mbuf |
| * itself becomes part of the receive buffer, so the mbuf has to be |
| * trimmed in order for this to work out. |
| */ |
| tlen -= todrop; |
| thflags &= ~(TH_PUSH|TH_FIN); |
| } |
| |
| /* |
| * If last ACK falls within this segment's sequence numbers, |
| * record its timestamp. |
| * NOTE: |
| * 1) That the test incorporates suggestions from the latest |
| * proposal of the tcplw@cray.com list (Braden 1993/04/26). |
| * 2) That updating only on newer timestamps interferes with |
| * our earlier PAWS tests, so this check should be solely |
| * predicated on the sequence space of this segment. |
| * 3) That we modify the segment boundary check to be |
| * Last.ACK.Sent <= SEG.SEQ + SEG.Len |
| * instead of RFC1323's |
| * Last.ACK.Sent < SEG.SEQ + SEG.Len, |
| * This modified check allows us to overcome RFC1323's |
| * limitations as described in Stevens TCP/IP Illustrated |
| * Vol. 2 p.869. In such cases, we can still calculate the |
| * RTT correctly when RCV.NXT == Last.ACK.Sent. |
| */ |
| |
| if ((to.to_flags & TOF_TS) != 0 && |
| SEQ_LEQ(th->th_seq, tp->last_ack_sent) && |
| SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + |
| ((thflags & (TH_SYN|TH_FIN)) != 0))) { |
| tp->ts_recent_age = tcp_ts_getticks(); |
| tp->ts_recent = to.to_tsval; |
| } |
| |
| /* |
| * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN |
| * flag is on (half-synchronized state), then queue data for |
| * later processing; else drop segment and return. |
| */ |
| if ((thflags & TH_ACK) == 0) { |
| if (tp->t_state == TCPS_SYN_RECEIVED || |
| (tp->t_flags & TF_NEEDSYN)) |
| goto step6; |
| else if (tp->t_flags & TF_ACKNOW) |
| goto dropafterack; |
| else |
| goto drop; |
| } |
| |
| tcplp_sys_log("Processing ACK"); |
| |
| /* |
| * Ack processing. |
| */ |
| switch (tp->t_state) { |
| |
| /* |
| * In SYN_RECEIVED state, the ack ACKs our SYN, so enter |
| * ESTABLISHED state and continue processing. |
| * The ACK was checked above. |
| */ |
| case TCPS_SYN_RECEIVED: |
| /* |
| * samkumar: Removed call to soisconnected(so), since TCPlp has its |
| * own buffering. |
| */ |
| /* Do window scaling? */ |
| if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == |
| (TF_RCVD_SCALE|TF_REQ_SCALE)) { |
| tp->rcv_scale = tp->request_r_scale; |
| tp->snd_wnd = tiwin; |
| } |
| /* |
| * Make transitions: |
| * SYN-RECEIVED -> ESTABLISHED |
| * SYN-RECEIVED* -> FIN-WAIT-1 |
| */ |
| tp->t_starttime = ticks; |
| if (tp->t_flags & TF_NEEDFIN) { |
| tcp_state_change(tp, TCPS_FIN_WAIT_1); |
| tp->t_flags &= ~TF_NEEDFIN; |
| } else { |
| tcp_state_change(tp, TCPS_ESTABLISHED); |
| /* samkumar: Set conn_established signal for TCPlp. */ |
| sig->conn_established = true; |
| cc_conn_init(tp); |
| tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp)); |
| /* |
| * samkumar: I added this check to account for simultaneous open. |
| * If this socket was opened actively, then the fact that we are |
| * in SYN-RECEIVED indicates that we are in simultaneous open. |
| * Therefore, don't ACK the SYN-ACK (unless it contains data or |
| * something, which will be processed later). |
| */ |
| if (!tpispassiveopen(tp)) { |
| tp->t_flags &= ~TF_ACKNOW; |
| } else { |
| /* |
| * samkumar: Otherwise, we entered the ESTABLISHED state by |
| * accepting a connection, so call the appropriate callback in |
| * TCPlp. TODO: consider using signals to handle this? |
| */ |
| bool accepted = tcplp_sys_accepted_connection(tp->accepted_from, tp, &ip6->ip6_src, th->th_sport); |
| if (!accepted) { |
| rstreason = ECONNREFUSED; |
| goto dropwithreset; |
| } |
| } |
| } |
| /* |
| * If segment contains data or ACK, will call tcp_reass() |
| * later; if not, do so now to pass queued data to user. |
| */ |
| if (tlen == 0 && (thflags & TH_FIN) == 0) |
| (void) tcp_reass(tp, (struct tcphdr *)0, 0, |
| (otMessage*)0, 0, sig); |
| |
| tp->snd_wl1 = th->th_seq - 1; |
| /* FALLTHROUGH */ |
| |
| /* |
| * In ESTABLISHED state: drop duplicate ACKs; ACK out of range |
| * ACKs. If the ack is in the range |
| * tp->snd_una < th->th_ack <= tp->snd_max |
| * then advance tp->snd_una to th->th_ack and drop |
| * data from the retransmission queue. If this ACK reflects |
| * more up to date window information we update our window information. |
| */ |
| case TCPS_ESTABLISHED: |
| case TCPS_FIN_WAIT_1: |
| case TCPS_FIN_WAIT_2: |
| case TCPS_CLOSE_WAIT: |
| case TCPS_CLOSING: |
| case TCPS_LAST_ACK: |
| if (SEQ_GT(th->th_ack, tp->snd_max)) { |
| goto dropafterack; |
| } |
| |
| if ((tp->t_flags & TF_SACK_PERMIT) && |
| ((to.to_flags & TOF_SACK) || |
| !TAILQ_EMPTY(&tp->snd_holes))) |
| tcp_sack_doack(tp, &to, th->th_ack); |
| |
| if (SEQ_LEQ(th->th_ack, tp->snd_una)) { |
| if (tlen == 0 && tiwin == tp->snd_wnd) { |
| /* |
| * If this is the first time we've seen a |
| * FIN from the remote, this is not a |
| * duplicate and it needs to be processed |
| * normally. This happens during a |
| * simultaneous close. |
| */ |
| if ((thflags & TH_FIN) && |
| (TCPS_HAVERCVDFIN(tp->t_state) == 0)) { |
| tp->t_dupacks = 0; |
| break; |
| } |
| /* |
| * If we have outstanding data (other than |
| * a window probe), this is a completely |
| * duplicate ack (ie, window info didn't |
| * change and FIN isn't set), |
| * the ack is the biggest we've |
| * seen and we've seen exactly our rexmt |
| * threshhold of them, assume a packet |
| * has been dropped and retransmit it. |
| * Kludge snd_nxt & the congestion |
| * window so we send only this one |
| * packet. |
| * |
| * We know we're losing at the current |
| * window size so do congestion avoidance |
| * (set ssthresh to half the current window |
| * and pull our congestion window back to |
| * the new ssthresh). |
| * |
| * Dup acks mean that packets have left the |
| * network (they're now cached at the receiver) |
| * so bump cwnd by the amount in the receiver |
| * to keep a constant cwnd packets in the |
| * network. |
| * |
| * When using TCP ECN, notify the peer that |
| * we reduced the cwnd. |
| */ |
| if (!tcp_timer_active(tp, TT_REXMT) || |
| th->th_ack != tp->snd_una) |
| tp->t_dupacks = 0; |
| else if (++tp->t_dupacks > tcprexmtthresh || |
| IN_FASTRECOVERY(tp->t_flags)) { |
| cc_ack_received(tp, th, CC_DUPACK); |
| if ((tp->t_flags & TF_SACK_PERMIT) && |
| IN_FASTRECOVERY(tp->t_flags)) { |
| int awnd; |
| |
| /* |
| * Compute the amount of data in flight first. |
| * We can inject new data into the pipe iff |
| * we have less than 1/2 the original window's |
| * worth of data in flight. |
| */ |
| awnd = (tp->snd_nxt - tp->snd_fack) + |
| tp->sackhint.sack_bytes_rexmit; |
| if (awnd < tp->snd_ssthresh) { |
| tp->snd_cwnd += tp->t_maxseg; |
| if (tp->snd_cwnd > tp->snd_ssthresh) |
| tp->snd_cwnd = tp->snd_ssthresh; |
| } |
| } else |
| tp->snd_cwnd += tp->t_maxseg; |
| #ifdef INSTRUMENT_TCP |
| tcplp_sys_log("TCP DUPACK"); |
| #endif |
| (void) tcp_output(tp); |
| goto drop; |
| } else if (tp->t_dupacks == tcprexmtthresh) { |
| tcp_seq onxt = tp->snd_nxt; |
| |
| /* |
| * If we're doing sack, check to |
| * see if we're already in sack |
| * recovery. If we're not doing sack, |
| * check to see if we're in newreno |
| * recovery. |
| */ |
| if (tp->t_flags & TF_SACK_PERMIT) { |
| if (IN_FASTRECOVERY(tp->t_flags)) { |
| tp->t_dupacks = 0; |
| break; |
| } |
| } else { |
| if (SEQ_LEQ(th->th_ack, |
| tp->snd_recover)) { |
| tp->t_dupacks = 0; |
| break; |
| } |
| } |
| /* Congestion signal before ack. */ |
| cc_cong_signal(tp, th, CC_NDUPACK); |
| cc_ack_received(tp, th, CC_DUPACK); |
| tcp_timer_activate(tp, TT_REXMT, 0); |
| tp->t_rtttime = 0; |
| |
| #ifdef INSTRUMENT_TCP |
| tcplp_sys_log("TCP DUPACK_THRESH"); |
| #endif |
| if (tp->t_flags & TF_SACK_PERMIT) { |
| tp->sack_newdata = tp->snd_nxt; |
| tp->snd_cwnd = tp->t_maxseg; |
| (void) tcp_output(tp); |
| goto drop; |
| } |
| |
| tp->snd_nxt = th->th_ack; |
| tp->snd_cwnd = tp->t_maxseg; |
| (void) tcp_output(tp); |
| tp->snd_cwnd = tp->snd_ssthresh + |
| tp->t_maxseg * |
| (tp->t_dupacks - tp->snd_limited); |
| #ifdef INSTRUMENT_TCP |
| tcplp_sys_log("TCP SET_cwnd %d", (int) tp->snd_cwnd); |
| #endif |
| if (SEQ_GT(onxt, tp->snd_nxt)) |
| tp->snd_nxt = onxt; |
| goto drop; |
| } else if (V_tcp_do_rfc3042) { |
| /* |
| * Process first and second duplicate |
| * ACKs. Each indicates a segment |
| * leaving the network, creating room |
| * for more. Make sure we can send a |
| * packet on reception of each duplicate |
| * ACK by increasing snd_cwnd by one |
| * segment. Restore the original |
| * snd_cwnd after packet transmission. |
| */ |
| uint64_t oldcwnd; |
| tcp_seq oldsndmax; |
| uint32_t sent; |
| int avail; |
| cc_ack_received(tp, th, CC_DUPACK); |
| oldcwnd = tp->snd_cwnd; |
| oldsndmax = tp->snd_max; |
| |
| #ifdef INSTRUMENT_TCP |
| tcplp_sys_log("TCP LIM_TRANS"); |
| #endif |
| |
| KASSERT(tp->t_dupacks == 1 || |
| tp->t_dupacks == 2, |
| ("%s: dupacks not 1 or 2", |
| __func__)); |
| if (tp->t_dupacks == 1) |
| tp->snd_limited = 0; |
| tp->snd_cwnd = |
| (tp->snd_nxt - tp->snd_una) + |
| (tp->t_dupacks - tp->snd_limited) * |
| tp->t_maxseg; |
| /* |
| * Only call tcp_output when there |
| * is new data available to be sent. |
| * Otherwise we would send pure ACKs. |
| */ |
| /* |
| * samkumar: Replace sbavail(&so->so_snd) with the call to |
| * lbuf_used_space. |
| */ |
| avail = lbuf_used_space(&tp->sendbuf) - |
| (tp->snd_nxt - tp->snd_una); |
| if (avail > 0) |
| (void) tcp_output(tp); |
| sent = tp->snd_max - oldsndmax; |
| if (sent > tp->t_maxseg) { |
| KASSERT((tp->t_dupacks == 2 && |
| tp->snd_limited == 0) || |
| (sent == tp->t_maxseg + 1 && |
| tp->t_flags & TF_SENTFIN), |
| ("%s: sent too much", |
| __func__)); |
| tp->snd_limited = 2; |
| } else if (sent > 0) |
| ++tp->snd_limited; |
| tp->snd_cwnd = oldcwnd; |
| #ifdef INSTRUMENT_TCP |
| tcplp_sys_log("TCP RESET_cwnd %d", (int) tp->snd_cwnd); |
| #endif |
| goto drop; |
| } |
| } else |
| tp->t_dupacks = 0; |
| break; |
| } |
| |
| KASSERT(SEQ_GT(th->th_ack, tp->snd_una), |
| ("%s: th_ack <= snd_una", __func__)); |
| |
| /* |
| * If the congestion window was inflated to account |
| * for the other side's cached packets, retract it. |
| */ |
| if (IN_FASTRECOVERY(tp->t_flags)) { |
| if (SEQ_LT(th->th_ack, tp->snd_recover)) { |
| if (tp->t_flags & TF_SACK_PERMIT) |
| tcp_sack_partialack(tp, th); |
| else |
| tcp_newreno_partial_ack(tp, th); |
| } else |
| cc_post_recovery(tp, th); |
| } |
| |
| tp->t_dupacks = 0; |
| /* |
| * If we reach this point, ACK is not a duplicate, |
| * i.e., it ACKs something we sent. |
| */ |
| if (tp->t_flags & TF_NEEDSYN) { |
| /* |
| * T/TCP: Connection was half-synchronized, and our |
| * SYN has been ACK'd (so connection is now fully |
| * synchronized). Go to non-starred state, |
| * increment snd_una for ACK of SYN, and check if |
| * we can do window scaling. |
| */ |
| tp->t_flags &= ~TF_NEEDSYN; |
| tp->snd_una++; |
| /* Do window scaling? */ |
| if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == |
| (TF_RCVD_SCALE|TF_REQ_SCALE)) { |
| tp->rcv_scale = tp->request_r_scale; |
| /* Send window already scaled. */ |
| } |
| } |
| |
| process_ACK: |
| acked = BYTES_THIS_ACK(tp, th); |
| |
| tcplp_sys_log("Bytes acked: %d", acked); |
| /* |
| * If we just performed our first retransmit, and the ACK |
| * arrives within our recovery window, then it was a mistake |
| * to do the retransmit in the first place. Recover our |
| * original cwnd and ssthresh, and proceed to transmit where |
| * we left off. |
| */ |
| if (tp->t_rxtshift == 1 && tp->t_flags & TF_PREVVALID && |
| (int)(ticks - tp->t_badrxtwin) < 0) |
| cc_cong_signal(tp, th, CC_RTO_ERR); |
| |
| /* |
| * If we have a timestamp reply, update smoothed |
| * round trip time. If no timestamp is present but |
| * transmit timer is running and timed sequence |
| * number was acked, update smoothed round trip time. |
| * Since we now have an rtt measurement, cancel the |
| * timer backoff (cf., Phil Karn's retransmit alg.). |
| * Recompute the initial retransmit timer. |
| * |
| * Some boxes send broken timestamp replies |
| * during the SYN+ACK phase, ignore |
| * timestamps of 0 or we could calculate a |
| * huge RTT and blow up the retransmit timer. |
| */ |
| |
| if ((to.to_flags & TOF_TS) != 0 && to.to_tsecr) { |
| uint32_t t; |
| |
| t = tcp_ts_getticks() - to.to_tsecr; |
| if (!tp->t_rttlow || tp->t_rttlow > t) |
| tp->t_rttlow = t; |
| tcp_xmit_timer(tp, TCP_TS_TO_TICKS(t) + 1); |
| } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { |
| if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime) |
| tp->t_rttlow = ticks - tp->t_rtttime; |
| tcp_xmit_timer(tp, ticks - tp->t_rtttime); |
| } |
| |
| /* |
| * If all outstanding data is acked, stop retransmit |
| * timer and remember to restart (more output or persist). |
| * If there is more data to be acked, restart retransmit |
| * timer, using current (possibly backed-off) value. |
| */ |
| if (th->th_ack == tp->snd_max) { |
| tcp_timer_activate(tp, TT_REXMT, 0); |
| needoutput = 1; |
| } else if (!tcp_timer_active(tp, TT_PERSIST)) { |
| tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); |
| } |
| |
| /* |
| * If no data (only SYN) was ACK'd, |
| * skip rest of ACK processing. |
| */ |
| if (acked == 0) |
| goto step6; |
| |
| /* |
| * Let the congestion control algorithm update congestion |
| * control related information. This typically means increasing |
| * the congestion window. |
| */ |
| cc_ack_received(tp, th, CC_ACK); |
| |
| /* |
| * samkumar: I replaced the calls to sbavail(&so->so_snd) with new |
| * calls to lbuf_used_space, and then I modified the code to actually |
| * remove code from the send buffer, formerly done via |
| * sbcut_locked(&so->so_send, (int)sbavail(&so->so_snd)) in the if case |
| * and sbcut_locked(&so->so_snd, acked) in the else case, to use the |
| * data structures for TCPlp's data buffering. |
| */ |
| if (acked > lbuf_used_space(&tp->sendbuf)) { |
| uint32_t poppedbytes; |
| uint32_t usedspace = lbuf_used_space(&tp->sendbuf); |
| tp->snd_wnd -= usedspace; |
| poppedbytes = lbuf_pop(&tp->sendbuf, usedspace, &sig->links_popped); |
| KASSERT(poppedbytes == usedspace, ("Could not fully empty send buffer")); |
| sig->bytes_acked += poppedbytes; |
| ourfinisacked = 1; |
| } else { |
| uint32_t poppedbytes = lbuf_pop(&tp->sendbuf, acked, &sig->links_popped); |
| KASSERT(poppedbytes == acked, ("Could not remove acked bytes from send buffer")); |
| sig->bytes_acked += poppedbytes; |
| tp->snd_wnd -= acked; |
| ourfinisacked = 0; |
| } |
| /* NB: sowwakeup_locked() does an implicit unlock. */ |
| /* |
| * samkumar: There used to be a call to sowwakeup(so); here, |
| * which wakes up any threads waiting for the socket to |
| * become ready for writing. TCPlp handles its send buffer |
| * differently so we do not need to replace this call with |
| * specialized code to handle this. |
| */ |
| /* Detect una wraparound. */ |
| if (!IN_RECOVERY(tp->t_flags) && |
| SEQ_GT(tp->snd_una, tp->snd_recover) && |
| SEQ_LEQ(th->th_ack, tp->snd_recover)) |
| tp->snd_recover = th->th_ack - 1; |
| /* XXXLAS: Can this be moved up into cc_post_recovery? */ |
| if (IN_RECOVERY(tp->t_flags) && |
| SEQ_GEQ(th->th_ack, tp->snd_recover)) { |
| EXIT_RECOVERY(tp->t_flags); |
| } |
| tp->snd_una = th->th_ack; |
| if (tp->t_flags & TF_SACK_PERMIT) { |
| if (SEQ_GT(tp->snd_una, tp->snd_recover)) |
| tp->snd_recover = tp->snd_una; |
| } |
| if (SEQ_LT(tp->snd_nxt, tp->snd_una)) |
| tp->snd_nxt = tp->snd_una; |
| |
| switch (tp->t_state) { |
| |
| /* |
| * In FIN_WAIT_1 STATE in addition to the processing |
| * for the ESTABLISHED state if our FIN is now acknowledged |
| * then enter FIN_WAIT_2. |
| */ |
| case TCPS_FIN_WAIT_1: |
| if (ourfinisacked) { |
| /* |
| * If we can't receive any more |
| * data, then closing user can proceed. |
| * Starting the timer is contrary to the |
| * specification, but if we don't get a FIN |
| * we'll hang forever. |
| * |
| * XXXjl: |
| * we should release the tp also, and use a |
| * compressed state. |
| */ |
| /* |
| * samkumar: I replaced a check for the SBS_CANTRCVMORE flag |
| * in so->so_rcv.sb_state with a call to tcpiscantrcv. |
| */ |
| if (tpiscantrcv(tp)) { |
| /* samkumar: Removed a call to soisdisconnected(so). */ |
| tcp_timer_activate(tp, TT_2MSL, |
| (tcp_fast_finwait2_recycle ? |
| tcp_finwait2_timeout : |
| TP_MAXIDLE(tp))); |
| } |
| tcp_state_change(tp, TCPS_FIN_WAIT_2); |
| } |
| break; |
| |
| /* |
| * In CLOSING STATE in addition to the processing for |
| * the ESTABLISHED state if the ACK acknowledges our FIN |
| * then enter the TIME-WAIT state, otherwise ignore |
| * the segment. |
| */ |
| case TCPS_CLOSING: |
| if (ourfinisacked) { |
| /* |
| * samkumar: I added the line below. We need to avoid sending |
| * an ACK in the TIME-WAIT state, since we don't want to |
| * ACK ACKs. This edge case appears because TCPlp, unlike the |
| * original FreeBSD code, uses tcpcbs for connections in the |
| * TIME-WAIT state (FreeBSD uses a different, smaller |
| * structure). |
| */ |
| tp->t_flags &= ~TF_ACKNOW; |
| tcp_twstart(tp); |
| return; |
| } |
| break; |
| |
| /* |
| * In LAST_ACK, we may still be waiting for data to drain |
| * and/or to be acked, as well as for the ack of our FIN. |
| * If our FIN is now acknowledged, delete the TCB, |
| * enter the closed state and return. |
| */ |
| case TCPS_LAST_ACK: |
| if (ourfinisacked) { |
| tp = tcp_close(tp); |
| tcplp_sys_connection_lost(tp, CONN_LOST_NORMAL); |
| goto drop; |
| } |
| break; |
| } |
| } |
| |
| step6: |
| |
| /* |
| * Update window information. |
| * Don't look at window if no ACK: TAC's send garbage on first SYN. |
| */ |
| if ((thflags & TH_ACK) && |
| (SEQ_LT(tp->snd_wl1, th->th_seq) || |
| (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || |
| (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { |
| /* keep track of pure window updates */ |
| /* |
| * samkumar: There used to be an if statement here that would check if |
| * this is a "pure" window update (tlen == 0 && |
| * tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) and keep |
| * statistics for how often that happens. |
| */ |
| tp->snd_wnd = tiwin; |
| tp->snd_wl1 = th->th_seq; |
| tp->snd_wl2 = th->th_ack; |
| if (tp->snd_wnd > tp->max_sndwnd) |
| tp->max_sndwnd = tp->snd_wnd; |
| needoutput = 1; |
| } |
| |
| /* |
| * Process segments with URG. |
| */ |
| /* |
| * samkumar: TCPlp does not support the urgent pointer, so we omit all |
| * urgent-pointer-related processing and buffering. The code below is the |
| * code that was in the "else" case that handles no valid urgent data in |
| * the received packet. |
| */ |
| { |
| /* |
| * If no out of band data is expected, |
| * pull receive urgent pointer along |
| * with the receive window. |
| */ |
| if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) |
| tp->rcv_up = tp->rcv_nxt; |
| } |
| |
| /* |
| * Process the segment text, merging it into the TCP sequencing queue, |
| * and arranging for acknowledgment of receipt if necessary. |
| * This process logically involves adjusting tp->rcv_wnd as data |
| * is presented to the user (this happens in tcp_usrreq.c, |
| * case PRU_RCVD). If a FIN has already been received on this |
| * connection then we just ignore the text. |
| */ |
| if ((tlen || (thflags & TH_FIN)) && |
| TCPS_HAVERCVDFIN(tp->t_state) == 0) { |
| tcp_seq save_start = th->th_seq; |
| /* |
| * samkumar: I removed a call to m_adj(m, drop_hdrlen), which intends |
| * to drop data from the mbuf so it can be chained into the receive |
| * header. This is not necessary for TCPlp because we copy the data |
| * anyway; we just add the offset when copying data into the receive |
| * buffer. |
| */ |
| /* |
| * Insert segment which includes th into TCP reassembly queue |
| * with control block tp. Set thflags to whether reassembly now |
| * includes a segment with FIN. This handles the common case |
| * inline (segment is the next to be received on an established |
| * connection, and the queue is empty), avoiding linkage into |
| * and removal from the queue and repetition of various |
| * conversions. |
| * Set DELACK for segments received in order, but ack |
| * immediately when segments are out of order (so |
| * fast retransmit can work). |
| */ |
| /* |
| * samkumar: I replaced LIST_EMPTY(&tp->t_segq) with the calls to |
| * tpiscantrcv and bmp_isempty on the second line below. |
| */ |
| if (th->th_seq == tp->rcv_nxt && |
| (tpiscantrcv(tp) || bmp_isempty(tp->reassbmp, REASSBMP_SIZE(tp))) && |
| TCPS_HAVEESTABLISHED(tp->t_state)) { |
| if (DELAY_ACK(tp, tlen)) |
| tp->t_flags |= TF_DELACK; |
| else |
| tp->t_flags |= TF_ACKNOW; |
| tp->rcv_nxt += tlen; |
| thflags = th->th_flags & TH_FIN; |
| |
| /* |
| * samkumar: I replaced the code that used to be here (which would |
| * free the mbuf with m_freem(m) if the SBS_CANTRCVMORE flag is set |
| * on so->so_rcv.sb_state, and otherwise call |
| * sbappendstream_locked(&so->so_rcv, m, 0);). |
| */ |
| if (!tpiscantrcv(tp)) { |
| cbuf_write(&tp->recvbuf, msg, otMessageGetOffset(msg) + drop_hdrlen, tlen, cbuf_copy_from_message); |
| if (tlen > 0) { |
| sig->recvbuf_added = true; |
| } |
| } else if (tlen > 0) { |
| /* |
| * samkumar: We already know tlen != 0, so if we got here, then |
| * it means that we got data after we called SHUT_RD, or after |
| * receiving a FIN. I'm going to drop the connection in this |
| * case. I think FreeBSD might have just dropped the packet |
| * silently, but Linux handles it this way; this seems to be |
| * the right approach to me. |
| */ |
| tcp_drop(tp, ECONNABORTED); |
| goto drop; |
| } |
| /* NB: sorwakeup_locked() does an implicit unlock. */ |
| /* |
| * samkumar: There used to be a call to sorwakeup_locked(so); here, |
| * which wakes up any threads waiting for the socket to become |
| * become ready for reading. TCPlp handles its buffering |
| * differently so we do not need to replace this call with |
| * specialized code to handle this. |
| */ |
| } else if (tpiscantrcv(tp)) { |
| /* |
| * samkumar: We will reach this point if we get out-of-order data |
| * on a socket which was shut down with SHUT_RD, or where we |
| * already received a FIN. My response here is to drop the segment |
| * and send an RST. |
| */ |
| tcp_drop(tp, ECONNABORTED); |
| goto drop; |
| } else { |
| /* |
| * XXX: Due to the header drop above "th" is |
| * theoretically invalid by now. Fortunately |
| * m_adj() doesn't actually frees any mbufs |
| * when trimming from the head. |
| */ |
| thflags = tcp_reass(tp, th, &tlen, msg, otMessageGetOffset(msg) + drop_hdrlen, sig); |
| tp->t_flags |= TF_ACKNOW; |
| } |
| // Only place tlen is used after the call to tcp_reass is below |
| if (tlen > 0 && (tp->t_flags & TF_SACK_PERMIT)) |
| tcp_update_sack_list(tp, save_start, save_start + tlen); |
| /* |
| * samkumar: This is not me commenting things out; this was already |
| * commented out in the FreeBSD code. |
| */ |
| #if 0 |
| /* |
| * Note the amount of data that peer has sent into |
| * our window, in order to estimate the sender's |
| * buffer size. |
| * XXX: Unused. |
| */ |
| if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) |
| len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); |
| else |
| len = so->so_rcv.sb_hiwat; |
| #endif |
| } else { |
| thflags &= ~TH_FIN; |
| } |
| |
| /* |
| * If FIN is received ACK the FIN and let the user know |
| * that the connection is closing. |
| */ |
| if (thflags & TH_FIN) { |
| tcplp_sys_log("FIN Processing start"); |
| if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { |
| /* samkumar: replace socantrcvmore with tpcantrcvmore */ |
| tpcantrcvmore(tp); |
| /* |
| * If connection is half-synchronized |
| * (ie NEEDSYN flag on) then delay ACK, |
| * so it may be piggybacked when SYN is sent. |
| * Otherwise, since we received a FIN then no |
| * more input can be expected, send ACK now. |
| */ |
| if (tp->t_flags & TF_NEEDSYN) |
| tp->t_flags |= TF_DELACK; |
| else |
| tp->t_flags |= TF_ACKNOW; |
| tp->rcv_nxt++; |
| } |
| /* |
| * samkumar: This -2 state is added by me, so that we do not consider |
| * any more FINs in reassembly. |
| */ |
| if (tp->reass_fin_index != -2) { |
| sig->rcvd_fin = true; |
| tp->reass_fin_index = -2; |
| } |
| switch (tp->t_state) { |
| |
| /* |
| * In SYN_RECEIVED and ESTABLISHED STATES |
| * enter the CLOSE_WAIT state. |
| */ |
| case TCPS_SYN_RECEIVED: |
| tp->t_starttime = ticks; |
| /* FALLTHROUGH */ |
| case TCPS_ESTABLISHED: |
| tcp_state_change(tp, TCPS_CLOSE_WAIT); |
| break; |
| |
| /* |
| * If still in FIN_WAIT_1 STATE FIN has not been acked so |
| * enter the CLOSING state. |
| */ |
| case TCPS_FIN_WAIT_1: |
| tcp_state_change(tp, TCPS_CLOSING); |
| break; |
| |
| /* |
| * In FIN_WAIT_2 state enter the TIME_WAIT state, |
| * starting the time-wait timer, turning off the other |
| * standard timers. |
| */ |
| case TCPS_FIN_WAIT_2: |
| tcp_twstart(tp); |
| return; |
| } |
| } |
| |
| /* |
| * samkumar: Remove code for synchronization and debugging, here and in |
| * the labels below. I also removed the line to free the mbuf if it hasn't |
| * been freed already (the line was "m_freem(m)"). |
| */ |
| /* |
| * Return any desired output. |
| */ |
| if (needoutput || (tp->t_flags & TF_ACKNOW)) |
| (void) tcp_output(tp); |
| |
| check_delack: |
| if (tp->t_flags & TF_DELACK) { |
| tp->t_flags &= ~TF_DELACK; |
| tcp_timer_activate(tp, TT_DELACK, tcp_delacktime); |
| } |
| return; |
| |
| dropafterack: |
| /* |
| * Generate an ACK dropping incoming segment if it occupies |
| * sequence space, where the ACK reflects our state. |
| * |
| * We can now skip the test for the RST flag since all |
| * paths to this code happen after packets containing |
| * RST have been dropped. |
| * |
| * In the SYN-RECEIVED state, don't send an ACK unless the |
| * segment we received passes the SYN-RECEIVED ACK test. |
| * If it fails send a RST. This breaks the loop in the |
| * "LAND" DoS attack, and also prevents an ACK storm |
| * between two listening ports that have been sent forged |
| * SYN segments, each with the source address of the other. |
| */ |
| if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && |
| (SEQ_GT(tp->snd_una, th->th_ack) || |
| SEQ_GT(th->th_ack, tp->snd_max)) ) { |
| rstreason = BANDLIM_RST_OPENPORT; |
| goto dropwithreset; |
| } |
| |
| tp->t_flags |= TF_ACKNOW; |
| (void) tcp_output(tp); |
| return; |
| |
| dropwithreset: |
| if (tp != NULL) { |
| tcp_dropwithreset(ip6, th, tp, instance, tlen, rstreason); |
| } else |
| tcp_dropwithreset(ip6, th, NULL, instance, tlen, rstreason); |
| return; |
| |
| drop: |
| return; |
| } |
| |
| /* |
| * Parse TCP options and place in tcpopt. |
| */ |
| static void |
| tcp_dooptions(struct tcpopt *to, uint8_t *cp, int cnt, int flags) |
| { |
| int opt, optlen; |
| |
| to->to_flags = 0; |
| for (; cnt > 0; cnt -= optlen, cp += optlen) { |
| opt = cp[0]; |
| if (opt == TCPOPT_EOL) |
| break; |
| if (opt == TCPOPT_NOP) |
| optlen = 1; |
| else { |
| if (cnt < 2) |
| break; |
| optlen = cp[1]; |
| if (optlen < 2 || optlen > cnt) |
| break; |
| } |
| switch (opt) { |
| case TCPOPT_MAXSEG: |
| if (optlen != TCPOLEN_MAXSEG) |
| continue; |
| if (!(flags & TO_SYN)) |
| continue; |
| to->to_flags |= TOF_MSS; |
| bcopy((char *)cp + 2, |
| (char *)&to->to_mss, sizeof(to->to_mss)); |
| to->to_mss = ntohs(to->to_mss); |
| break; |
| case TCPOPT_WINDOW: |
| if (optlen != TCPOLEN_WINDOW) |
| continue; |
| if (!(flags & TO_SYN)) |
| continue; |
| to->to_flags |= TOF_SCALE; |
| to->to_wscale = min(cp[2], TCP_MAX_WINSHIFT); |
| break; |
| case TCPOPT_TIMESTAMP: |
| if (optlen != TCPOLEN_TIMESTAMP) |
| continue; |
| to->to_flags |= TOF_TS; |
| bcopy((char *)cp + 2, |
| (char *)&to->to_tsval, sizeof(to->to_tsval)); |
| to->to_tsval = ntohl(to->to_tsval); |
| bcopy((char *)cp + 6, |
| (char *)&to->to_tsecr, sizeof(to->to_tsecr)); |
| to->to_tsecr = ntohl(to->to_tsecr); |
| break; |
| #ifdef TCP_SIGNATURE |
| /* |
| * XXX In order to reply to a host which has set the |
| * TCP_SIGNATURE option in its initial SYN, we have to |
| * record the fact that the option was observed here |
| * for the syncache code to perform the correct response. |
| */ |
| case TCPOPT_SIGNATURE: |
| if (optlen != TCPOLEN_SIGNATURE) |
| continue; |
| to->to_flags |= TOF_SIGNATURE; |
| to->to_signature = cp + 2; |
| break; |
| #endif |
| case TCPOPT_SACK_PERMITTED: |
| if (optlen != TCPOLEN_SACK_PERMITTED) |
| continue; |
| if (!(flags & TO_SYN)) |
| continue; |
| if (!V_tcp_do_sack) |
| continue; |
| to->to_flags |= TOF_SACKPERM; |
| break; |
| case TCPOPT_SACK: |
| if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) |
| continue; |
| if (flags & TO_SYN) |
| continue; |
| to->to_flags |= TOF_SACK; |
| to->to_nsacks = (optlen - 2) / TCPOLEN_SACK; |
| to->to_sacks = cp + 2; |
| break; |
| default: |
| continue; |
| } |
| } |
| } |
| |
| |
| /* |
| * Collect new round-trip time estimate |
| * and update averages and current timeout. |
| */ |
| static void |
| tcp_xmit_timer(struct tcpcb *tp, int rtt) |
| { |
| int delta; |
| |
| tp->t_rttupdated++; |
| if (tp->t_srtt != 0) { |
| /* |
| * srtt is stored as fixed point with 5 bits after the |
| * binary point (i.e., scaled by 8). The following magic |
| * is equivalent to the smoothing algorithm in rfc793 with |
| * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed |
| * point). Adjust rtt to origin 0. |
| */ |
| delta = ((rtt - 1) << TCP_DELTA_SHIFT) |
| - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); |
| |
| if ((tp->t_srtt += delta) <= 0) |
| tp->t_srtt = 1; |
| |
| /* |
| * We accumulate a smoothed rtt variance (actually, a |
| * smoothed mean difference), then set the retransmit |
| * timer to smoothed rtt + 4 times the smoothed variance. |
| * rttvar is stored as fixed point with 4 bits after the |
| * binary point (scaled by 16). The following is |
| * equivalent to rfc793 smoothing with an alpha of .75 |
| * (rttvar = rttvar*3/4 + |delta| / 4). This replaces |
| * rfc793's wired-in beta. |
| */ |
| if (delta < 0) |
| delta = -delta; |
| delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); |
| if ((tp->t_rttvar += delta) <= 0) |
| tp->t_rttvar = 1; |
| if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) |
| tp->t_rttbest = tp->t_srtt + tp->t_rttvar; |
| } else { |
| /* |
| * No rtt measurement yet - use the unsmoothed rtt. |
| * Set the variance to half the rtt (so our first |
| * retransmit happens at 3*rtt). |
| */ |
| tp->t_srtt = rtt << TCP_RTT_SHIFT; |
| tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); |
| tp->t_rttbest = tp->t_srtt + tp->t_rttvar; |
| } |
| tp->t_rtttime = 0; |
| tp->t_rxtshift = 0; |
| |
| /* |
| * the retransmit should happen at rtt + 4 * rttvar. |
| * Because of the way we do the smoothing, srtt and rttvar |
| * will each average +1/2 tick of bias. When we compute |
| * the retransmit timer, we want 1/2 tick of rounding and |
| * 1 extra tick because of +-1/2 tick uncertainty in the |
| * firing of the timer. The bias will give us exactly the |
| * 1.5 tick we need. But, because the bias is |
| * statistical, we have to test that we don't drop below |
| * the minimum feasible timer (which is 2 ticks). |
| */ |
| TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), |
| max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); |
| |
| #ifdef INSTRUMENT_TCP |
| tcplp_sys_log("TCP timer %u %d %d %d", (unsigned int) tcplp_sys_get_millis(), rtt, (int) tp->t_srtt, (int) tp->t_rttvar); |
| #endif |
| |
| |
| /* |
| * We received an ack for a packet that wasn't retransmitted; |
| * it is probably safe to discard any error indications we've |
| * received recently. This isn't quite right, but close enough |
| * for now (a route might have failed after we sent a segment, |
| * and the return path might not be symmetrical). |
| */ |
| tp->t_softerror = 0; |
| } |
| |
| /* |
| * samkumar: Taken from netinet6/in6.c. |
| * |
| * This function is supposed to check whether the provided address is an |
| * IPv6 address of this host. This function, however, is used only as a hint, |
| * as the MSS is clamped at V_tcp_v6mssdflt for connections to non-local |
| * addresses. It is difficult for us to actually determine if the address |
| * belongs to us, so we are conservative and only return 1 (true) if it is |
| * obviously so---we keep the part of the function that checks for loopback or |
| * link local and remove the rest of the code that checks for the addresses |
| * assigned to interfaces. In cases where we return 0 but should have returned |
| * 1, we may conservatively clamp the MTU, but that should be OK for TCPlp. |
| * In fact, the constants are set such that we'll get the right answer whether |
| * we clamp or not, so this shouldn't really matter at all. |
| */ |
| int |
| in6_localaddr(struct in6_addr *in6) |
| { |
| if (IN6_IS_ADDR_LOOPBACK(in6) || IN6_IS_ADDR_LINKLOCAL(in6)) |
| return 1; |
| return (0); |
| } |
| |
| /* |
| * Determine a reasonable value for maxseg size. |
| * If the route is known, check route for mtu. |
| * If none, use an mss that can be handled on the outgoing interface |
| * without forcing IP to fragment. If no route is found, route has no mtu, |
| * or the destination isn't local, use a default, hopefully conservative |
| * size (usually 512 or the default IP max size, but no more than the mtu |
| * of the interface), as we can't discover anything about intervening |
| * gateways or networks. We also initialize the congestion/slow start |
| * window to be a single segment if the destination isn't local. |
| * While looking at the routing entry, we also initialize other path-dependent |
| * parameters from pre-set or cached values in the routing entry. |
| * |
| * Also take into account the space needed for options that we |
| * send regularly. Make maxseg shorter by that amount to assure |
| * that we can send maxseg amount of data even when the options |
| * are present. Store the upper limit of the length of options plus |
| * data in maxopd. |
| * |
| * NOTE that this routine is only called when we process an incoming |
| * segment, or an ICMP need fragmentation datagram. Outgoing SYN/ACK MSS |
| * settings are handled in tcp_mssopt(). |
| */ |
| /* |
| * samkumar: Using struct tcpcb instead of the inpcb. |
| */ |
| void |
| tcp_mss_update(struct tcpcb *tp, int offer, int mtuoffer, |
| struct hc_metrics_lite *metricptr, struct tcp_ifcap *cap) |
| { |
| /* |
| * samkumar: I removed all IPv4-specific logic and cases, including logic |
| * to check for IPv4 vs. IPv6, as well as all locking and debugging code. |
| */ |
| int mss = 0; |
| uint64_t maxmtu = 0; |
| struct hc_metrics_lite metrics; |
| int origoffer; |
| size_t min_protoh = IP6HDR_SIZE + sizeof (struct tcphdr); |
| |
| if (mtuoffer != -1) { |
| KASSERT(offer == -1, ("%s: conflict", __func__)); |
| offer = mtuoffer - min_protoh; |
| } |
| origoffer = offer; |
| |
| maxmtu = tcp_maxmtu6(tp, cap); |
| tp->t_maxopd = tp->t_maxseg = V_tcp_v6mssdflt; |
| |
| /* |
| * No route to sender, stay with default mss and return. |
| */ |
| if (maxmtu == 0) { |
| /* |
| * In case we return early we need to initialize metrics |
| * to a defined state as tcp_hc_get() would do for us |
| * if there was no cache hit. |
| */ |
| if (metricptr != NULL) |
| bzero(metricptr, sizeof(struct hc_metrics_lite)); |
| return; |
| } |
| |
| /* What have we got? */ |
| switch (offer) { |
| case 0: |
| /* |
| * Offer == 0 means that there was no MSS on the SYN |
| * segment, in this case we use tcp_mssdflt as |
| * already assigned to t_maxopd above. |
| */ |
| offer = tp->t_maxopd; |
| break; |
| |
| case -1: |
| /* |
| * Offer == -1 means that we didn't receive SYN yet. |
| */ |
| /* FALLTHROUGH */ |
| |
| default: |
| /* |
| * Prevent DoS attack with too small MSS. Round up |
| * to at least minmss. |
| */ |
| offer = max(offer, V_tcp_minmss); |
| } |
| |
| /* |
| * rmx information is now retrieved from tcp_hostcache. |
| */ |
| tcp_hc_get(tp, &metrics); |
| if (metricptr != NULL) |
| bcopy(&metrics, metricptr, sizeof(struct hc_metrics_lite)); |
| |
| /* |
| * If there's a discovered mtu in tcp hostcache, use it. |
| * Else, use the link mtu. |
| */ |
| if (metrics.rmx_mtu) |
| mss = min(metrics.rmx_mtu, maxmtu) - min_protoh; |
| else { |
| mss = maxmtu - min_protoh; |
| if (!V_path_mtu_discovery && |
| !in6_localaddr(&tp->faddr)) |
| mss = min(mss, V_tcp_v6mssdflt); |
| /* |
| * XXX - The above conditional (mss = maxmtu - min_protoh) |
| * probably violates the TCP spec. |
| * The problem is that, since we don't know the |
| * other end's MSS, we are supposed to use a conservative |
| * default. But, if we do that, then MTU discovery will |
| * never actually take place, because the conservative |
| * default is much less than the MTUs typically seen |
| * on the Internet today. For the moment, we'll sweep |
| * this under the carpet. |
| * |
| * The conservative default might not actually be a problem |
| * if the only case this occurs is when sending an initial |
| * SYN with options and data to a host we've never talked |
| * to before. Then, they will reply with an MSS value which |
| * will get recorded and the new parameters should get |
| * recomputed. For Further Study. |
| */ |
| } |
| mss = min(mss, offer); |
| |
| /* |
| * Sanity check: make sure that maxopd will be large |
| * enough to allow some data on segments even if the |
| * all the option space is used (40bytes). Otherwise |
| * funny things may happen in tcp_output. |
| */ |
| /* |
| * samkumar: When I was experimenting with different MSS values, I had |
| * changed this to "mss = max(mss, TCP_MAXOLEN + 1);" but I am changing it |
| * back for the version that will be merged into OpenThread. |
| */ |
| mss = max(mss, 64); |
| |
| /* |
| * maxopd stores the maximum length of data AND options |
| * in a segment; maxseg is the amount of data in a normal |
| * segment. We need to store this value (maxopd) apart |
| * from maxseg, because now every segment carries options |
| * and thus we normally have somewhat less data in segments. |
| */ |
| tp->t_maxopd = mss; |
| |
| /* |
| * origoffer==-1 indicates that no segments were received yet. |
| * In this case we just guess. |
| */ |
| if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && |
| (origoffer == -1 || |
| (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) |
| mss -= TCPOLEN_TSTAMP_APPA; |
| |
| tp->t_maxseg = mss; |
| } |
| |
| void |
| tcp_mss(struct tcpcb *tp, int offer) |
| { |
| struct hc_metrics_lite metrics; |
| struct tcp_ifcap cap; |
| |
| KASSERT(tp != NULL, ("%s: tp == NULL", __func__)); |
| |
| bzero(&cap, sizeof(cap)); |
| tcp_mss_update(tp, offer, -1, &metrics, &cap); |
| |
| /* |
| * samkumar: There used to be code below that might modify the MSS, but I |
| * removed all of it (see the comments below for the reason). It used to |
| * read tp->t_maxseg into the local variable mss, modify mss, and then |
| * reassign tp->t_maxseg to mss. I've kept the assignments, commented out, |
| * for clarity. |
| */ |
| //mss = tp->t_maxseg; |
| |
| /* |
| * If there's a pipesize, change the socket buffer to that size, |
| * don't change if sb_hiwat is different than default (then it |
| * has been changed on purpose with setsockopt). |
| * Make the socket buffers an integral number of mss units; |
| * if the mss is larger than the socket buffer, decrease the mss. |
| */ |
| |
| /* |
| * samkumar: There used to be code here would would limit the MSS to at |
| * most the size of the send buffer, and then round up the send buffer to |
| * a multiple of the MSS using |
| * "sbreserve_locked(&so->so_snd, bufsize, so, NULL);". With TCPlp, we do |
| * not do this, because the linked buffer used at the send buffer doesn't |
| * have a real limit. Had we used a circular buffer, then limiting the MSS |
| * to the buffer size would have made sense, but we still would not be able |
| * to resize the send buffer because it is not allocated by TCPlp. |
| */ |
| |
| /* |
| * samkumar: See the comment above about me removing code that modifies |
| * the MSS, making this assignment and the one above both unnecessary. |
| */ |
| //tp->t_maxseg = mss; |
| |
| /* |
| * samkumar: There used to be code here that would round up the receive |
| * buffer size to a multiple of the MSS, assuming that the receive buffer |
| * size is bigger than the MSS. The new buffer size is set using |
| * "sbreserve_locked(&so->so_rcv, bufsize, so, NULL);". In TCPlp, the |
| * buffer is not allocated by TCPlp so I removed the code for this. |
| */ |
| /* |
| * samkumar: There used to be code here to handle TCP Segmentation |
| * Offloading (TSO); I removed it becuase we don't support that in TCPlp. |
| */ |
| } |
| |
| /* |
| * Determine the MSS option to send on an outgoing SYN. |
| */ |
| /* |
| * samkumar: In the signature, changed "struct in_conninfo *inc" to |
| * "struct tcpcb* tp". |
| */ |
| int |
| tcp_mssopt(struct tcpcb* tp) |
| { |
| /* |
| * samkumar: I removed all processing code specific to IPv4, or to decide |
| * between IPv4 and IPv6. This is OK because TCPlp assumes IPv6. |
| */ |
| int mss = 0; |
| uint64_t maxmtu = 0; |
| uint64_t thcmtu = 0; |
| size_t min_protoh; |
| |
| KASSERT(tp != NULL, ("tcp_mssopt with NULL tcpcb pointer")); |
| |
| mss = V_tcp_v6mssdflt; |
| maxmtu = tcp_maxmtu6(tp, NULL); |
| min_protoh = IP6HDR_SIZE + sizeof(struct tcphdr); |
| |
| thcmtu = tcp_hc_getmtu(tp); /* IPv4 and IPv6 */ |
| |
| if (maxmtu && thcmtu) |
| mss = min(maxmtu, thcmtu) - min_protoh; |
| else if (maxmtu || thcmtu) |
| mss = max(maxmtu, thcmtu) - min_protoh; |
| |
| return (mss); |
| } |
| |
| /* |
| * On a partial ack arrives, force the retransmission of the |
| * next unacknowledged segment. Do not clear tp->t_dupacks. |
| * By setting snd_nxt to ti_ack, this forces retransmission timer to |
| * be started again. |
| */ |
| static void |
| tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th) |
| { |
| tcp_seq onxt = tp->snd_nxt; |
| uint64_t ocwnd = tp->snd_cwnd; |
| |
| tcp_timer_activate(tp, TT_REXMT, 0); |
| tp->t_rtttime = 0; |
| tp->snd_nxt = th->th_ack; |
| /* |
| * Set snd_cwnd to one segment beyond acknowledged offset. |
| * (tp->snd_una has not yet been updated when this function is called.) |
| */ |
| tp->snd_cwnd = tp->t_maxseg + BYTES_THIS_ACK(tp, th); |
| tp->t_flags |= TF_ACKNOW; |
| #ifdef INSTRUMENT_TCP |
| tcplp_sys_log("TCP Partial_ACK"); |
| #endif |
| (void) tcp_output(tp); |
| tp->snd_cwnd = ocwnd; |
| if (SEQ_GT(onxt, tp->snd_nxt)) |
| tp->snd_nxt = onxt; |
| /* |
| * Partial window deflation. Relies on fact that tp->snd_una |
| * not updated yet. |
| */ |
| if (tp->snd_cwnd > BYTES_THIS_ACK(tp, th)) |
| tp->snd_cwnd -= BYTES_THIS_ACK(tp, th); |
| else |
| tp->snd_cwnd = 0; |
| tp->snd_cwnd += tp->t_maxseg; |
| #ifdef INSTRUMENT_TCP |
| tcplp_sys_log("TCP Partial_ACK_final %d", (int) tp->snd_cwnd); |
| #endif |
| } |