| // Copyright 2020 The gVisor Authors. |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| package tcp |
| |
| // renoRecovery stores the variables related to TCP Reno loss recovery |
| // algorithm. |
| // |
| // +stateify savable |
| type renoRecovery struct { |
| s *sender |
| } |
| |
| func newRenoRecovery(s *sender) *renoRecovery { |
| return &renoRecovery{s: s} |
| } |
| |
| func (rr *renoRecovery) DoRecovery(rcvdSeg *segment, fastRetransmit bool) { |
| ack := rcvdSeg.ackNumber |
| snd := rr.s |
| |
| // We are in fast recovery mode. Ignore the ack if it's out of range. |
| if !ack.InRange(snd.sndUna, snd.sndNxt+1) { |
| return |
| } |
| |
| // Don't count this as a duplicate if it is carrying data or |
| // updating the window. |
| if rcvdSeg.logicalLen() != 0 || snd.sndWnd != rcvdSeg.window { |
| return |
| } |
| |
| // Inflate the congestion window if we're getting duplicate acks |
| // for the packet we retransmitted. |
| if !fastRetransmit && ack == snd.fr.first { |
| // We received a dup, inflate the congestion window by 1 packet |
| // if we're not at the max yet. Only inflate the window if |
| // regular FastRecovery is in use, RFC6675 does not require |
| // inflating cwnd on duplicate ACKs. |
| if snd.sndCwnd < snd.fr.maxCwnd { |
| snd.sndCwnd++ |
| } |
| return |
| } |
| |
| // A partial ack was received. Retransmit this packet and remember it |
| // so that we don't retransmit it again. |
| // |
| // We don't inflate the window because we're putting the same packet |
| // back onto the wire. |
| // |
| // N.B. The retransmit timer will be reset by the caller. |
| snd.fr.first = ack |
| snd.dupAckCount = 0 |
| snd.resendSegment() |
| } |
