diff options
| author | Andrei Vagin <avagin@google.com> | 2019-03-19 17:32:23 -0700 |
|---|---|---|
| committer | Shentubot <shentubot@google.com> | 2019-03-19 17:33:20 -0700 |
| commit | 87cce0ec08b9d629a5e3a88be411b1721d767301 (patch) | |
| tree | 86c7f3b29933a86a1b7efb22694fb8413c70e780 /pkg/tcpip/transport/tcp | |
| parent | 7b33df68450bdb9519cf650a8d92fa4a81f37fa0 (diff) | |
netstack: reduce MSS from SYN to account tcp options
See: https://tools.ietf.org/html/rfc6691#section-2
PiperOrigin-RevId: 239305632
Change-Id: Ie8eb912a43332e6490045dc95570709c5b81855e
Diffstat (limited to 'pkg/tcpip/transport/tcp')
| -rw-r--r-- | pkg/tcpip/transport/tcp/endpoint.go | 10 | ||||
| -rw-r--r-- | pkg/tcpip/transport/tcp/snd.go | 13 |
2 files changed, 17 insertions, 6 deletions
diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go index 7d18e3612..5656890f6 100644 --- a/pkg/tcpip/transport/tcp/endpoint.go +++ b/pkg/tcpip/transport/tcp/endpoint.go @@ -1596,6 +1596,16 @@ func (e *endpoint) maybeEnableSACKPermitted(synOpts *header.TCPSynOptions) { } } +// maxOptionSize return the maximum size of TCP options. +func (e *endpoint) maxOptionSize() (size int) { + var maxSackBlocks [header.TCPMaxSACKBlocks]header.SACKBlock + options := e.makeOptions(maxSackBlocks[:]) + size = len(options) + putOptions(options) + + return size +} + // completeState makes a full copy of the endpoint and returns it. This is used // before invoking the probe. The state returned may not be fully consistent if // there are intervening syscalls when the state is being copied. diff --git a/pkg/tcpip/transport/tcp/snd.go b/pkg/tcpip/transport/tcp/snd.go index e38932df7..18365a673 100644 --- a/pkg/tcpip/transport/tcp/snd.go +++ b/pkg/tcpip/transport/tcp/snd.go @@ -172,6 +172,11 @@ type fastRecovery struct { } func newSender(ep *endpoint, iss, irs seqnum.Value, sndWnd seqnum.Size, mss uint16, sndWndScale int) *sender { + // The sender MUST reduce the TCP data length to account for any IP or + // TCP options that it is including in the packets that it sends. + // See: https://tools.ietf.org/html/rfc6691#section-2 + maxPayloadSize := int(mss) - ep.maxOptionSize() + s := &sender{ ep: ep, sndCwnd: InitialCwnd, @@ -183,7 +188,7 @@ func newSender(ep *endpoint, iss, irs seqnum.Value, sndWnd seqnum.Size, mss uint rto: 1 * time.Second, rttMeasureSeqNum: iss + 1, lastSendTime: time.Now(), - maxPayloadSize: int(mss), + maxPayloadSize: maxPayloadSize, maxSentAck: irs + 1, fr: fastRecovery{ // See: https://tools.ietf.org/html/rfc6582#section-3.2 Step 1. @@ -226,11 +231,7 @@ func (s *sender) initCongestionControl(congestionControlName CongestionControlOp func (s *sender) updateMaxPayloadSize(mtu, count int) { m := mtu - header.TCPMinimumSize - // Calculate the maximum option size. - var maxSackBlocks [header.TCPMaxSACKBlocks]header.SACKBlock - options := s.ep.makeOptions(maxSackBlocks[:]) - m -= len(options) - putOptions(options) + m -= s.ep.maxOptionSize() // We don't adjust up for now. if m >= s.maxPayloadSize { |