diff options
Diffstat (limited to 'pkg/tcpip/header/tcp.go')
| -rw-r--r-- | pkg/tcpip/header/tcp.go | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/pkg/tcpip/header/tcp.go b/pkg/tcpip/header/tcp.go index 13480687d..21581257b 100644 --- a/pkg/tcpip/header/tcp.go +++ b/pkg/tcpip/header/tcp.go @@ -594,3 +594,20 @@ func AddTCPOptionPadding(options []byte, offset int) int { } return paddingToAdd } + +// Acceptable checks if a segment that starts at segSeq and has length segLen is +// "acceptable" for arriving in a receive window that starts at rcvNxt and ends +// before rcvAcc, according to the table on page 26 and 69 of RFC 793. +func Acceptable(segSeq seqnum.Value, segLen seqnum.Size, rcvNxt, rcvAcc seqnum.Value) bool { + if rcvNxt == rcvAcc { + return segLen == 0 && segSeq == rcvNxt + } + if segLen == 0 { + // rcvWnd is incremented by 1 because that is Linux's behavior despite the + // RFC. + return segSeq.InRange(rcvNxt, rcvAcc.Add(1)) + } + // Page 70 of RFC 793 allows packets that can be made "acceptable" by trimming + // the payload, so we'll accept any payload that overlaps the receieve window. + return rcvNxt.LessThan(segSeq.Add(segLen)) && segSeq.LessThan(rcvAcc) +} |