KarpelesLab / slirp / 23945997146

71%

Build Type

push

github

Committed by MagicalTux

Commit Message

Implement RFC 7323 window scaling and fix throughput

Window scaling:
- Auto-computed from RecvBufSize (default 1MB → shift 4)
- Always offered in SYN options (enabled by default)
- Negotiated during handshake: both sides must offer WScale
- rcvWindow() now advertises actual buffer availability, scaled
- sndWnd properly shifted by remote's scale factor

Initial congestion window:
- Fixed RFC 6928 formula: min(10*MSS, max(2*MSS, 14600))
- Was incorrectly using 4380 instead of 14600
- Initial window now 14600 bytes (10 segments) instead of 4380 (3)

Data race fix:
- rcvWindow() acquires recvMu when reading recvBuf.Readable()
- Prevents race between HandleSegment (builds ACK under mu)
  and Read() (modifies recvBuf under recvMu)

Throughput improvement at 100ms RTT (50ms one-way):
  Before: 0.5 MB/s (64KB window cap, 3-segment initial window)
  After:  4.0 MB/s (1MB window, 10-segment initial window)

Test sizes increased to 4MB to measure steady-state throughput.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Coverage Stats

39 of 46 new or added lines in 2 files covered. (84.78%)

3 existing lines in 2 files now uncovered.

2637 of 3529 relevant lines covered (74.72%)

539.21 hits per line