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