From 326394b79a62061e3e239ac104c151ca13647439 Mon Sep 17 00:00:00 2001 From: Mithun Iyer Date: Tue, 13 Apr 2021 00:56:32 -0700 Subject: Fix listener close, client connect race Fix a race where the ACK completing the handshake can be dropped by a closing listener without RST to the peer. The listener close would reset the accepted queue and that causes the connecting endpoint in SYNRCVD state to drop the ACK thinking the queue if filled up. PiperOrigin-RevId: 368165509 --- pkg/tcpip/transport/tcp/accept.go | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) (limited to 'pkg/tcpip/transport/tcp/accept.go') diff --git a/pkg/tcpip/transport/tcp/accept.go b/pkg/tcpip/transport/tcp/accept.go index 7acc7e7b0..63c46b1be 100644 --- a/pkg/tcpip/transport/tcp/accept.go +++ b/pkg/tcpip/transport/tcp/accept.go @@ -511,22 +511,22 @@ func (e *endpoint) handleSynSegment(ctx *listenContext, s *segment, opts *header func (e *endpoint) synRcvdBacklogFull() bool { e.acceptMu.Lock() - backlog := e.accepted.cap + acceptedCap := e.accepted.cap e.acceptMu.Unlock() - // The allocated accepted channel size would always be one greater than the + // The capacity of the accepted queue would always be one greater than the // listen backlog. But, the SYNRCVD connections count is always checked // against the listen backlog value for Linux parity reason. // https://github.com/torvalds/linux/blob/7acac4b3196/include/net/inet_connection_sock.h#L280 // // We maintain an equality check here as the synRcvdCount is incremented // and compared only from a single listener context and the capacity of - // the accepted channel can only increase by a new listen call. - return int(atomic.LoadInt32(&e.synRcvdCount)) == backlog-1 + // the accepted queue can only increase by a new listen call. + return int(atomic.LoadInt32(&e.synRcvdCount)) == acceptedCap-1 } func (e *endpoint) acceptQueueIsFull() bool { e.acceptMu.Lock() - full := e.accepted.endpoints.Len() == e.accepted.cap + full := e.accepted != (accepted{}) && e.accepted.endpoints.Len() == e.accepted.cap e.acceptMu.Unlock() return full } -- cgit v1.2.3