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Remove duplicate accept queue fullness check

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Both code paths perform this check; extract it and remove the comment
that suggests it is unique to one of the paths.

PiperOrigin-RevId: 367666160
This commit is contained in:
Tamir Duberstein
2021-04-09 11:08:21 -07:00
committed by gVisor bot
parent 1fe5dd8c68
commit 070b76fe7f
1 changed files with 44 additions and 53 deletions
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pkg/tcpip/transport/tcp/accept.go
+44 -53
View File
@@ -538,65 +538,56 @@ func (e *endpoint) handleListenSegment(ctx *listenContext, s *segment) tcpip.Err
switch {
case s.flags == header.TCPFlagSyn:
opts := parseSynSegmentOptions(s)
if !ctx.useSynCookies() {
if !e.acceptQueueIsFull() {
s.incRef()
atomic.AddInt32(&e.synRcvdCount, 1)
return e.handleSynSegment(ctx, s, &opts)
}
if e.acceptQueueIsFull() {
e.stack.Stats().TCP.ListenOverflowSynDrop.Increment()
e.stats.ReceiveErrors.ListenOverflowSynDrop.Increment()
e.stack.Stats().DroppedPackets.Increment()
return nil
} else {
// If cookies are in use but the endpoint accept queue
// is full then drop the syn.
if e.acceptQueueIsFull() {
e.stack.Stats().TCP.ListenOverflowSynDrop.Increment()
e.stats.ReceiveErrors.ListenOverflowSynDrop.Increment()
e.stack.Stats().DroppedPackets.Increment()
return nil
}
cookie := ctx.createCookie(s.id, s.sequenceNumber, encodeMSS(opts.MSS))
route, err := e.stack.FindRoute(s.nicID, s.dstAddr, s.srcAddr, s.netProto, false /* multicastLoop */)
if err != nil {
return err
}
defer route.Release()
// Send SYN without window scaling because we currently
// don't encode this information in the cookie.
//
// Enable Timestamp option if the original syn did have
// the timestamp option specified.
//
// Use the user supplied MSS on the listening socket for
// new connections, if available.
synOpts := header.TCPSynOptions{
WS: -1,
TS: opts.TS,
TSVal: tcpTimeStamp(time.Now(), timeStampOffset()),
TSEcr: opts.TSVal,
MSS: calculateAdvertisedMSS(e.userMSS, route),
}
fields := tcpFields{
id: s.id,
ttl: e.ttl,
tos: e.sendTOS,
flags: header.TCPFlagSyn | header.TCPFlagAck,
seq: cookie,
ack: s.sequenceNumber + 1,
rcvWnd: ctx.rcvWnd,
}
if err := e.sendSynTCP(route, fields, synOpts); err != nil {
return err
}
e.stack.Stats().TCP.ListenOverflowSynCookieSent.Increment()
return nil
}
opts := parseSynSegmentOptions(s)
if !ctx.useSynCookies() {
s.incRef()
atomic.AddInt32(&e.synRcvdCount, 1)
return e.handleSynSegment(ctx, s, &opts)
}
route, err := e.stack.FindRoute(s.nicID, s.dstAddr, s.srcAddr, s.netProto, false /* multicastLoop */)
if err != nil {
return err
}
defer route.Release()
// Send SYN without window scaling because we currently
// don't encode this information in the cookie.
//
// Enable Timestamp option if the original syn did have
// the timestamp option specified.
//
// Use the user supplied MSS on the listening socket for
// new connections, if available.
synOpts := header.TCPSynOptions{
WS: -1,
TS: opts.TS,
TSVal: tcpTimeStamp(time.Now(), timeStampOffset()),
TSEcr: opts.TSVal,
MSS: calculateAdvertisedMSS(e.userMSS, route),
}
cookie := ctx.createCookie(s.id, s.sequenceNumber, encodeMSS(opts.MSS))
fields := tcpFields{
id: s.id,
ttl: e.ttl,
tos: e.sendTOS,
flags: header.TCPFlagSyn | header.TCPFlagAck,
seq: cookie,
ack: s.sequenceNumber + 1,
rcvWnd: ctx.rcvWnd,
}
if err := e.sendSynTCP(route, fields, synOpts); err != nil {
return err
}
e.stack.Stats().TCP.ListenOverflowSynCookieSent.Increment()
return nil
case (s.flags & header.TCPFlagAck) != 0:
if e.acceptQueueIsFull() {
// Silently drop the ack as the application can't accept