| /** |
| * @file |
| * |
| * Transmission Control Protocol, outgoing traffic |
| */ |
| /* |
| * Copyright (c) 2001-2004 Swedish Institute of Computer Science. |
| * All rights reserved. |
| * |
| * 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. |
| * 3. The name of the author may not be used to endorse or promote products |
| * derived from this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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. |
| * |
| * This file is part of the lwIP TCP/IP stack. |
| * |
| * Author: Adam Dunkels <adam@sics.se> |
| * |
| */ |
| |
| |
| /* tcp_output.c |
| * |
| * The output functions of TCP. |
| * |
| */ |
| |
| |
| |
| #include "lwip/def.h" |
| #include "lwip/opt.h" |
| |
| #include "lwip/mem.h" |
| #include "lwip/memp.h" |
| #include "lwip/sys.h" |
| |
| #include "lwip/netif.h" |
| |
| #include "lwip/inet.h" |
| #include "lwip/tcp.h" |
| |
| #include "lwip/stats.h" |
| |
| #if LWIP_TCP |
| |
| /* Forward declarations.*/ |
| static void tcp_output_segment(struct tcp_seg *seg, struct tcp_pcb *pcb); |
| |
| |
| |
| err_t |
| tcp_send_ctrl(struct tcp_pcb *pcb, u8_t flags) |
| { |
| return tcp_enqueue(pcb, NULL, 0, flags, 1, NULL, 0); |
| |
| } |
| |
| err_t |
| tcp_write(struct tcp_pcb *pcb, const void *arg, u16_t len, u8_t copy) |
| { |
| LWIP_DEBUGF(TCP_OUTPUT_DEBUG, ("tcp_write(pcb=%p, arg=%p, len=%u, copy=%d)\n", (void *)pcb, |
| arg, len, (unsigned int)copy)); |
| if (pcb->state == SYN_SENT || |
| pcb->state == SYN_RCVD || |
| pcb->state == ESTABLISHED || |
| pcb->state == CLOSE_WAIT) { |
| if (len > 0) { |
| return tcp_enqueue(pcb, (void *)arg, len, 0, copy, NULL, 0); |
| } |
| return ERR_OK; |
| } else { |
| LWIP_DEBUGF(TCP_OUTPUT_DEBUG | DBG_STATE | 3, ("tcp_write() called in invalid state\n")); |
| return ERR_CONN; |
| } |
| } |
| |
| err_t |
| tcp_enqueue(struct tcp_pcb *pcb, void *arg, u16_t len, |
| u8_t flags, u8_t copy, |
| u8_t *optdata, u8_t optlen) |
| { |
| struct pbuf *p; |
| struct tcp_seg *seg, *useg, *queue; |
| u32_t left, seqno; |
| u16_t seglen; |
| void *ptr; |
| u8_t queuelen; |
| |
| LWIP_DEBUGF(TCP_OUTPUT_DEBUG, ("tcp_enqueue(pcb=%p, arg=%p, len=%u, flags=%x, copy=%u)\n", |
| (void *)pcb, arg, len, (unsigned int)flags, (unsigned int)copy)); |
| left = len; |
| ptr = arg; |
| /* fail on too much data */ |
| if (len > pcb->snd_buf) { |
| LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 3, ("tcp_enqueue: too much data (len=%u > snd_buf=%u)\n", len, pcb->snd_buf)); |
| return ERR_MEM; |
| } |
| |
| /* seqno will be the sequence number of the first segment enqueued |
| * by the call to this function. */ |
| seqno = pcb->snd_lbb; |
| |
| queue = NULL; |
| LWIP_DEBUGF(TCP_QLEN_DEBUG, ("tcp_enqueue: queuelen: %u\n", (unsigned int)pcb->snd_queuelen)); |
| |
| /* Check if the queue length exceeds the configured maximum queue |
| * length. If so, we return an error. */ |
| queuelen = pcb->snd_queuelen; |
| if (queuelen >= TCP_SND_QUEUELEN) { |
| LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 3, ("tcp_enqueue: too long queue %u (max %u)\n", queuelen, TCP_SND_QUEUELEN)); |
| goto memerr; |
| } |
| |
| if (pcb->snd_queuelen != 0) { |
| LWIP_ASSERT("tcp_enqueue: valid queue length", pcb->unacked != NULL || |
| pcb->unsent != NULL); |
| } |
| |
| seg = useg = NULL; |
| seglen = 0; |
| |
| /* First, break up the data into segments and tuck them together in |
| * the local "queue" variable. */ |
| while (queue == NULL || left > 0) { |
| |
| /* The segment length should be the MSS if the data to be enqueued |
| * is larger than the MSS. */ |
| seglen = left > pcb->mss? pcb->mss: left; |
| |
| /* Allocate memory for tcp_seg, and fill in fields. */ |
| seg = memp_malloc(MEMP_TCP_SEG); |
| if (seg == NULL) { |
| LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 2, ("tcp_enqueue: could not allocate memory for tcp_seg\n")); |
| goto memerr; |
| } |
| seg->next = NULL; |
| seg->p = NULL; |
| |
| if (queue == NULL) { |
| useg = queue = seg; |
| } |
| else { |
| /* Attach the segment to the end of the queued segments. */ |
| LWIP_ASSERT("useg != NULL", useg != NULL); |
| useg->next = seg; |
| useg = seg; |
| } |
| |
| /* If copy is set, memory should be allocated |
| * and data copied into pbuf, otherwise data comes from |
| * ROM or other static memory, and need not be copied. If |
| * optdata is != NULL, we have options instead of data. */ |
| if (optdata != NULL) { |
| if ((seg->p = pbuf_alloc(PBUF_TRANSPORT, optlen, PBUF_RAM)) == NULL) { |
| goto memerr; |
| } |
| ++queuelen; |
| seg->dataptr = seg->p->payload; |
| } |
| else if (copy) { |
| if ((seg->p = pbuf_alloc(PBUF_TRANSPORT, seglen, PBUF_RAM)) == NULL) { |
| LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 2, ("tcp_enqueue : could not allocate memory for pbuf copy size %u\n", seglen)); |
| goto memerr; |
| } |
| ++queuelen; |
| if (arg != NULL) { |
| memcpy(seg->p->payload, ptr, seglen); |
| } |
| seg->dataptr = seg->p->payload; |
| } |
| /* do not copy data */ |
| else { |
| |
| /* first, allocate a pbuf for holding the data. |
| * since the referenced data is available at least until it is sent out on the |
| * link (as it has to be ACKed by the remote party) we can safely use PBUF_ROM |
| * instead of PBUF_REF here. |
| */ |
| if ((p = pbuf_alloc(PBUF_TRANSPORT, seglen, PBUF_ROM)) == NULL) { |
| LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 2, ("tcp_enqueue: could not allocate memory for zero-copy pbuf\n")); |
| goto memerr; |
| } |
| ++queuelen; |
| p->payload = ptr; |
| seg->dataptr = ptr; |
| |
| /* Second, allocate a pbuf for the headers. */ |
| if ((seg->p = pbuf_alloc(PBUF_TRANSPORT, 0, PBUF_RAM)) == NULL) { |
| /* If allocation fails, we have to deallocate the data pbuf as |
| * well. */ |
| pbuf_free(p); |
| LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 2, ("tcp_enqueue: could not allocate memory for header pbuf\n")); |
| goto memerr; |
| } |
| ++queuelen; |
| |
| /* Concatenate the headers and data pbufs together. */ |
| pbuf_cat(seg->p, p); |
| p = NULL; |
| } |
| |
| /* Now that there are more segments queued, we check again if the |
| length of the queue exceeds the configured maximum. */ |
| if (queuelen > TCP_SND_QUEUELEN) { |
| LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 2, ("tcp_enqueue: queue too long %u (%u)\n", queuelen, TCP_SND_QUEUELEN)); |
| goto memerr; |
| } |
| |
| seg->len = seglen; |
| #if 0 /* Was commented out. TODO: can someone say why this is here? */ |
| if ((flags & TCP_SYN) || (flags & TCP_FIN)) { |
| ++seg->len; |
| } |
| #endif |
| /* Build TCP header. */ |
| if (pbuf_header(seg->p, TCP_HLEN)) { |
| |
| LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 2, ("tcp_enqueue: no room for TCP header in pbuf.\n")); |
| |
| TCP_STATS_INC(tcp.err); |
| goto memerr; |
| } |
| seg->tcphdr = seg->p->payload; |
| seg->tcphdr->src = htons(pcb->local_port); |
| seg->tcphdr->dest = htons(pcb->remote_port); |
| seg->tcphdr->seqno = htonl(seqno); |
| seg->tcphdr->urgp = 0; |
| TCPH_FLAGS_SET(seg->tcphdr, flags); |
| /* don't fill in tcphdr->ackno and tcphdr->wnd until later */ |
| |
| /* Copy the options into the header, if they are present. */ |
| if (optdata == NULL) { |
| TCPH_HDRLEN_SET(seg->tcphdr, 5); |
| } |
| else { |
| TCPH_HDRLEN_SET(seg->tcphdr, (5 + optlen / 4)); |
| /* Copy options into data portion of segment. |
| Options can thus only be sent in non data carrying |
| segments such as SYN|ACK. */ |
| memcpy(seg->dataptr, optdata, optlen); |
| } |
| LWIP_DEBUGF(TCP_OUTPUT_DEBUG | DBG_TRACE, ("tcp_enqueue: queueing %lu:%lu (0x%x)\n", |
| ntohl(seg->tcphdr->seqno), |
| ntohl(seg->tcphdr->seqno) + TCP_TCPLEN(seg), |
| flags)); |
| |
| left -= seglen; |
| seqno += seglen; |
| ptr = (void *)((char *)ptr + seglen); |
| } |
| |
| |
| /* Now that the data to be enqueued has been broken up into TCP |
| segments in the queue variable, we add them to the end of the |
| pcb->unsent queue. */ |
| if (pcb->unsent == NULL) { |
| useg = NULL; |
| } |
| else { |
| for (useg = pcb->unsent; useg->next != NULL; useg = useg->next); |
| } |
| |
| /* If there is room in the last pbuf on the unsent queue, |
| chain the first pbuf on the queue together with that. */ |
| if (useg != NULL && |
| TCP_TCPLEN(useg) != 0 && |
| !(TCPH_FLAGS(useg->tcphdr) & (TCP_SYN | TCP_FIN)) && |
| !(flags & (TCP_SYN | TCP_FIN)) && |
| useg->len + queue->len <= pcb->mss) { |
| /* Remove TCP header from first segment. */ |
| pbuf_header(queue->p, -TCP_HLEN); |
| pbuf_cat(useg->p, queue->p); |
| useg->len += queue->len; |
| useg->next = queue->next; |
| |
| LWIP_DEBUGF(TCP_OUTPUT_DEBUG | DBG_TRACE | DBG_STATE, ("tcp_enqueue: chaining, new len %u\n", useg->len)); |
| if (seg == queue) { |
| seg = NULL; |
| } |
| memp_free(MEMP_TCP_SEG, queue); |
| } |
| else { |
| if (useg == NULL) { |
| pcb->unsent = queue; |
| |
| } |
| else { |
| useg->next = queue; |
| } |
| } |
| if ((flags & TCP_SYN) || (flags & TCP_FIN)) { |
| ++len; |
| } |
| pcb->snd_lbb += len; |
| pcb->snd_buf -= len; |
| pcb->snd_queuelen = queuelen; |
| LWIP_DEBUGF(TCP_QLEN_DEBUG, ("tcp_enqueue: %d (after enqueued)\n", pcb->snd_queuelen)); |
| if (pcb->snd_queuelen != 0) { |
| LWIP_ASSERT("tcp_enqueue: valid queue length", pcb->unacked != NULL || |
| pcb->unsent != NULL); |
| |
| } |
| |
| /* Set the PSH flag in the last segment that we enqueued, but only |
| if the segment has data (indicated by seglen > 0). */ |
| if (seg != NULL && seglen > 0 && seg->tcphdr != NULL) { |
| TCPH_SET_FLAG(seg->tcphdr, TCP_PSH); |
| } |
| |
| return ERR_OK; |
| memerr: |
| TCP_STATS_INC(tcp.memerr); |
| |
| if (queue != NULL) { |
| tcp_segs_free(queue); |
| } |
| if (pcb->snd_queuelen != 0) { |
| LWIP_ASSERT("tcp_enqueue: valid queue length", pcb->unacked != NULL || |
| pcb->unsent != NULL); |
| |
| } |
| LWIP_DEBUGF(TCP_QLEN_DEBUG | DBG_STATE, ("tcp_enqueue: %d (with mem err)\n", pcb->snd_queuelen)); |
| return ERR_MEM; |
| } |
| |
| /* find out what we can send and send it */ |
| err_t |
| tcp_output(struct tcp_pcb *pcb) |
| { |
| struct pbuf *p; |
| struct tcp_hdr *tcphdr; |
| struct tcp_seg *seg, *useg; |
| u32_t wnd; |
| #if TCP_CWND_DEBUG |
| int i = 0; |
| #endif /* TCP_CWND_DEBUG */ |
| |
| /* First, check if we are invoked by the TCP input processing |
| code. If so, we do not output anything. Instead, we rely on the |
| input processing code to call us when input processing is done |
| with. */ |
| if (tcp_input_pcb == pcb) { |
| return ERR_OK; |
| } |
| |
| wnd = LWIP_MIN(pcb->snd_wnd, pcb->cwnd); |
| |
| |
| seg = pcb->unsent; |
| |
| /* useg should point to last segment on unacked queue */ |
| useg = pcb->unacked; |
| if (useg != NULL) { |
| for (; useg->next != NULL; useg = useg->next); |
| } |
| |
| |
| /* If the TF_ACK_NOW flag is set, we check if there is data that is |
| to be sent. If data is to be sent out, we'll just piggyback our |
| acknowledgement with the outgoing segment. If no data will be |
| sent (either because the ->unsent queue is empty or because the |
| window doesn't allow it) we'll have to construct an empty ACK |
| segment and send it. */ |
| if (pcb->flags & TF_ACK_NOW && |
| (seg == NULL || |
| ntohl(seg->tcphdr->seqno) - pcb->lastack + seg->len > wnd)) { |
| pcb->flags &= ~(TF_ACK_DELAY | TF_ACK_NOW); |
| p = pbuf_alloc(PBUF_IP, TCP_HLEN, PBUF_RAM); |
| if (p == NULL) { |
| LWIP_DEBUGF(TCP_OUTPUT_DEBUG, ("tcp_output: (ACK) could not allocate pbuf\n")); |
| return ERR_BUF; |
| } |
| LWIP_DEBUGF(TCP_OUTPUT_DEBUG, ("tcp_output: sending ACK for %lu\n", pcb->rcv_nxt)); |
| |
| tcphdr = p->payload; |
| tcphdr->src = htons(pcb->local_port); |
| tcphdr->dest = htons(pcb->remote_port); |
| tcphdr->seqno = htonl(pcb->snd_nxt); |
| tcphdr->ackno = htonl(pcb->rcv_nxt); |
| TCPH_FLAGS_SET(tcphdr, TCP_ACK); |
| tcphdr->wnd = htons(pcb->rcv_wnd); |
| tcphdr->urgp = 0; |
| TCPH_HDRLEN_SET(tcphdr, 5); |
| |
| tcphdr->chksum = 0; |
| tcphdr->chksum = inet_chksum_pseudo(p, &(pcb->local_ip), &(pcb->remote_ip), |
| IP_PROTO_TCP, p->tot_len); |
| |
| |
| ip_output(p, &(pcb->local_ip), &(pcb->remote_ip), pcb->ttl, pcb->tos, |
| IP_PROTO_TCP); |
| pbuf_free(p); |
| |
| return ERR_OK; |
| } |
| |
| #if TCP_OUTPUT_DEBUG |
| if (seg == NULL) { |
| LWIP_DEBUGF(TCP_OUTPUT_DEBUG, ("tcp_output: nothing to send (%p)\n", pcb->unsent)); |
| } |
| #endif /* TCP_OUTPUT_DEBUG */ |
| #if TCP_CWND_DEBUG |
| if (seg == NULL) { |
| LWIP_DEBUGF(TCP_CWND_DEBUG, ("tcp_output: snd_wnd %lu, cwnd %lu, wnd %lu, seg == NULL, ack %lu\n", |
| pcb->snd_wnd, pcb->cwnd, wnd, |
| pcb->lastack)); |
| } else { |
| LWIP_DEBUGF(TCP_CWND_DEBUG, ("tcp_output: snd_wnd %lu, cwnd %lu, wnd %lu, effwnd %lu, seq %lu, ack %lu\n", |
| pcb->snd_wnd, pcb->cwnd, wnd, |
| ntohl(seg->tcphdr->seqno) - pcb->lastack + seg->len, |
| ntohl(seg->tcphdr->seqno), pcb->lastack)); |
| } |
| #endif /* TCP_CWND_DEBUG */ |
| |
| while (seg != NULL && |
| ntohl(seg->tcphdr->seqno) - pcb->lastack + seg->len <= wnd) { |
| #if TCP_CWND_DEBUG |
| LWIP_DEBUGF(TCP_CWND_DEBUG, ("tcp_output: snd_wnd %lu, cwnd %lu, wnd %lu, effwnd %lu, seq %lu, ack %lu, i%d\n", |
| pcb->snd_wnd, pcb->cwnd, wnd, |
| ntohl(seg->tcphdr->seqno) + seg->len - |
| pcb->lastack, |
| ntohl(seg->tcphdr->seqno), pcb->lastack, i)); |
| ++i; |
| #endif /* TCP_CWND_DEBUG */ |
| |
| pcb->unsent = seg->next; |
| |
| if (pcb->state != SYN_SENT) { |
| TCPH_SET_FLAG(seg->tcphdr, TCP_ACK); |
| pcb->flags &= ~(TF_ACK_DELAY | TF_ACK_NOW); |
| } |
| |
| tcp_output_segment(seg, pcb); |
| pcb->snd_nxt = ntohl(seg->tcphdr->seqno) + TCP_TCPLEN(seg); |
| if (TCP_SEQ_LT(pcb->snd_max, pcb->snd_nxt)) { |
| pcb->snd_max = pcb->snd_nxt; |
| } |
| /* put segment on unacknowledged list if length > 0 */ |
| if (TCP_TCPLEN(seg) > 0) { |
| seg->next = NULL; |
| if (pcb->unacked == NULL) { |
| pcb->unacked = seg; |
| useg = seg; |
| } else { |
| useg->next = seg; |
| useg = useg->next; |
| } |
| } else { |
| tcp_seg_free(seg); |
| } |
| seg = pcb->unsent; |
| } |
| return ERR_OK; |
| } |
| |
| static void |
| tcp_output_segment(struct tcp_seg *seg, struct tcp_pcb *pcb) |
| { |
| u16_t len; |
| struct netif *netif; |
| |
| /* The TCP header has already been constructed, but the ackno and |
| wnd fields remain. */ |
| seg->tcphdr->ackno = htonl(pcb->rcv_nxt); |
| |
| /* silly window avoidance */ |
| if (pcb->rcv_wnd < pcb->mss) { |
| seg->tcphdr->wnd = 0; |
| } else { |
| /* advertise our receive window size in this TCP segment */ |
| seg->tcphdr->wnd = htons(pcb->rcv_wnd); |
| } |
| |
| /* If we don't have a local IP address, we get one by |
| calling ip_route(). */ |
| if (ip_addr_isany(&(pcb->local_ip))) { |
| netif = ip_route(&(pcb->remote_ip)); |
| if (netif == NULL) { |
| return; |
| } |
| ip_addr_set(&(pcb->local_ip), &(netif->ip_addr)); |
| } |
| |
| pcb->rtime = 0; |
| |
| if (pcb->rttest == 0) { |
| pcb->rttest = tcp_ticks; |
| pcb->rtseq = ntohl(seg->tcphdr->seqno); |
| |
| LWIP_DEBUGF(TCP_RTO_DEBUG, ("tcp_output_segment: rtseq %lu\n", pcb->rtseq)); |
| } |
| LWIP_DEBUGF(TCP_OUTPUT_DEBUG, ("tcp_output_segment: %lu:%lu\n", |
| htonl(seg->tcphdr->seqno), htonl(seg->tcphdr->seqno) + |
| seg->len)); |
| |
| len = (u16_t)((u8_t *)seg->tcphdr - (u8_t *)seg->p->payload); |
| |
| seg->p->len -= len; |
| seg->p->tot_len -= len; |
| |
| seg->p->payload = seg->tcphdr; |
| |
| seg->tcphdr->chksum = 0; |
| seg->tcphdr->chksum = inet_chksum_pseudo(seg->p, |
| &(pcb->local_ip), |
| &(pcb->remote_ip), |
| IP_PROTO_TCP, seg->p->tot_len); |
| TCP_STATS_INC(tcp.xmit); |
| |
| ip_output(seg->p, &(pcb->local_ip), &(pcb->remote_ip), pcb->ttl, pcb->tos, |
| IP_PROTO_TCP); |
| } |
| |
| void |
| tcp_rst(u32_t seqno, u32_t ackno, |
| struct ip_addr *local_ip, struct ip_addr *remote_ip, |
| u16_t local_port, u16_t remote_port) |
| { |
| struct pbuf *p; |
| struct tcp_hdr *tcphdr; |
| p = pbuf_alloc(PBUF_IP, TCP_HLEN, PBUF_RAM); |
| if (p == NULL) { |
| LWIP_DEBUGF(TCP_DEBUG, ("tcp_rst: could not allocate memory for pbuf\n")); |
| return; |
| } |
| |
| tcphdr = p->payload; |
| tcphdr->src = htons(local_port); |
| tcphdr->dest = htons(remote_port); |
| tcphdr->seqno = htonl(seqno); |
| tcphdr->ackno = htonl(ackno); |
| TCPH_FLAGS_SET(tcphdr, TCP_RST | TCP_ACK); |
| tcphdr->wnd = htons(TCP_WND); |
| tcphdr->urgp = 0; |
| TCPH_HDRLEN_SET(tcphdr, 5); |
| |
| tcphdr->chksum = 0; |
| tcphdr->chksum = inet_chksum_pseudo(p, local_ip, remote_ip, |
| IP_PROTO_TCP, p->tot_len); |
| |
| TCP_STATS_INC(tcp.xmit); |
| /* Send output with hardcoded TTL since we have no access to the pcb */ |
| ip_output(p, local_ip, remote_ip, TCP_TTL, 0, IP_PROTO_TCP); |
| pbuf_free(p); |
| LWIP_DEBUGF(TCP_RST_DEBUG, ("tcp_rst: seqno %lu ackno %lu.\n", seqno, ackno)); |
| } |
| |
| void |
| tcp_rexmit(struct tcp_pcb *pcb) |
| { |
| struct tcp_seg *seg; |
| |
| if (pcb->unacked == NULL) { |
| return; |
| } |
| |
| /* Move all unacked segments to the unsent queue. */ |
| for (seg = pcb->unacked; seg->next != NULL; seg = seg->next); |
| |
| seg->next = pcb->unsent; |
| pcb->unsent = pcb->unacked; |
| |
| pcb->unacked = NULL; |
| |
| |
| pcb->snd_nxt = ntohl(pcb->unsent->tcphdr->seqno); |
| |
| ++pcb->nrtx; |
| |
| /* Don't take any rtt measurements after retransmitting. */ |
| pcb->rttest = 0; |
| |
| /* Do the actual retransmission. */ |
| tcp_output(pcb); |
| |
| } |
| |
| void |
| tcp_keepalive(struct tcp_pcb *pcb) |
| { |
| struct pbuf *p; |
| struct tcp_hdr *tcphdr; |
| |
| LWIP_DEBUGF(TCP_DEBUG, ("tcp_keepalive: sending KEEPALIVE probe to %u.%u.%u.%u\n", |
| ip4_addr1(&pcb->remote_ip), ip4_addr2(&pcb->remote_ip), |
| ip4_addr3(&pcb->remote_ip), ip4_addr4(&pcb->remote_ip))); |
| |
| LWIP_DEBUGF(TCP_DEBUG, ("tcp_keepalive: tcp_ticks %ld pcb->tmr %ld pcb->keep_cnt %ld\n", tcp_ticks, pcb->tmr, pcb->keep_cnt)); |
| |
| p = pbuf_alloc(PBUF_IP, TCP_HLEN, PBUF_RAM); |
| |
| if(p == NULL) { |
| LWIP_DEBUGF(TCP_DEBUG, ("tcp_keepalive: could not allocate memory for pbuf\n")); |
| return; |
| } |
| |
| tcphdr = p->payload; |
| tcphdr->src = htons(pcb->local_port); |
| tcphdr->dest = htons(pcb->remote_port); |
| tcphdr->seqno = htonl(pcb->snd_nxt - 1); |
| tcphdr->ackno = htonl(pcb->rcv_nxt); |
| tcphdr->wnd = htons(pcb->rcv_wnd); |
| tcphdr->urgp = 0; |
| TCPH_HDRLEN_SET(tcphdr, 5); |
| |
| tcphdr->chksum = 0; |
| tcphdr->chksum = inet_chksum_pseudo(p, &pcb->local_ip, &pcb->remote_ip, IP_PROTO_TCP, p->tot_len); |
| |
| TCP_STATS_INC(tcp.xmit); |
| |
| /* Send output to IP */ |
| ip_output(p, &pcb->local_ip, &pcb->remote_ip, pcb->ttl, 0, IP_PROTO_TCP); |
| |
| pbuf_free(p); |
| |
| LWIP_DEBUGF(TCP_RST_DEBUG, ("tcp_keepalive: seqno %lu ackno %lu.\n", pcb->snd_nxt - 1, pcb->rcv_nxt)); |
| } |
| |
| #endif /* LWIP_TCP */ |
| |
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