diff options
Diffstat (limited to 'pkg/tcpip/transport/tcp/endpoint.go')
| -rw-r--r-- | pkg/tcpip/transport/tcp/endpoint.go | 41 |
1 files changed, 39 insertions, 2 deletions
diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go index bc3b409ba..3bcd3923a 100644 --- a/pkg/tcpip/transport/tcp/endpoint.go +++ b/pkg/tcpip/transport/tcp/endpoint.go @@ -248,6 +248,11 @@ type ReceiveErrors struct { // ZeroRcvWindowState is the number of times we advertised // a zero receive window when rcvList is full. ZeroRcvWindowState tcpip.StatCounter + + // WantZeroWindow is the number of times we wanted to advertise a + // zero receive window but couldn't because it would have caused + // the receive window's right edge to shrink. + WantZeroRcvWindow tcpip.StatCounter } // SendErrors collect segment send errors within the transport layer. @@ -1162,7 +1167,7 @@ func (e *endpoint) cleanupLocked() { // wndFromSpace returns the window that we can advertise based on the available // receive buffer space. func wndFromSpace(space int) int { - return space / (1 << rcvAdvWndScale) + return space >> rcvAdvWndScale } // initialReceiveWindow returns the initial receive window to advertise in the @@ -1518,6 +1523,38 @@ func (e *endpoint) Peek(vec [][]byte) (int64, tcpip.ControlMessages, *tcpip.Erro return num, tcpip.ControlMessages{}, nil } +// selectWindowLocked returns the new window without checking for shrinking or scaling +// applied. +// Precondition: e.mu and e.rcvListMu must be held. +func (e *endpoint) selectWindowLocked() (wnd seqnum.Size) { + wndFromAvailable := wndFromSpace(e.receiveBufferAvailableLocked()) + maxWindow := wndFromSpace(e.rcvBufSize) + wndFromUsedBytes := maxWindow - e.rcvBufUsed + + // We take the lesser of the wndFromAvailable and wndFromUsedBytes because in + // cases where we receive a lot of small segments the segment overhead is a + // lot higher and we can run out socket buffer space before we can fill the + // previous window we advertised. In cases where we receive MSS sized or close + // MSS sized segments we will probably run out of window space before we + // exhaust receive buffer. + newWnd := wndFromAvailable + if newWnd > wndFromUsedBytes { + newWnd = wndFromUsedBytes + } + if newWnd < 0 { + newWnd = 0 + } + return seqnum.Size(newWnd) +} + +// selectWindow invokes selectWindowLocked after acquiring e.rcvListMu. +func (e *endpoint) selectWindow() (wnd seqnum.Size) { + e.rcvListMu.Lock() + wnd = e.selectWindowLocked() + e.rcvListMu.Unlock() + return wnd +} + // windowCrossedACKThresholdLocked checks if the receive window to be announced // would be under aMSS or under the window derived from half receive buffer, // whichever smaller. This is useful as a receive side silly window syndrome @@ -1534,7 +1571,7 @@ func (e *endpoint) Peek(vec [][]byte) (int64, tcpip.ControlMessages, *tcpip.Erro // // Precondition: e.mu and e.rcvListMu must be held. func (e *endpoint) windowCrossedACKThresholdLocked(deltaBefore int) (crossed bool, above bool) { - newAvail := wndFromSpace(e.receiveBufferAvailableLocked()) + newAvail := int(e.selectWindowLocked()) oldAvail := newAvail - deltaBefore if oldAvail < 0 { oldAvail = 0 |