Honor MSG_NOSIGNAL on AF_INET loopback stream send#858
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`send(fd, buf, MSG_NOSIGNAL)` on a broken connection must return EPIPE without raising SIGPIPE. `sys_send` honored this only on the AF_UNIX branch; the AF_INET loopback path called `sys_write` directly, which unconditionally raises SIGPIPE on a closed pipe. So a loopback TCP server whose peer closed its read side got a spurious SIGPIPE — terminating a process using the default disposition — the exact outcome MSG_NOSIGNAL exists to prevent. This also contradicted the documented guarantee (docs/posix-status.md: "MSG_NOSIGNAL is honored for stream/broken-pipe paths"). Apply the same save/clear-SIGPIPE handling the AF_UNIX branch already uses to the AF_INET loopback path. EPIPE is still returned; only the signal is suppressed. No ABI change. Validation: `cargo test -p kandelo --lib` (964 pass, incl. new `test_send_msg_nosignal_inet_loopback` — a loopback INET connect/accept, close the server end, `send(MSG_NOSIGNAL)`, assert EPIPE and no pending SIGPIPE; verified to fail without the fix). `scripts/check-abi-version.sh` in sync. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Contract: MSG_NOSIGNAL must suppress SIGPIPE on broken streams
send(fd, buf, MSG_NOSIGNAL)on a broken connection must returnEPIPEwithout raising SIGPIPE.sys_sendhonored this only on the AF_UNIX branch; the AF_INET loopback path calledsys_writedirectly, which unconditionally raises SIGPIPE on a closed pipe. A loopback TCP server whose peer closed its read side got a spurious SIGPIPE — terminating a process using the default disposition, the exact outcome MSG_NOSIGNAL exists to prevent.This also contradicted a documented guarantee (
docs/posix-status.md: "MSG_NOSIGNAL is honored for stream/broken-pipe paths"); the fix makes that statement true.Fix
Apply the same save/clear-SIGPIPE handling the AF_UNIX branch already uses to the AF_INET loopback path.
EPIPEis still returned; only the signal is suppressed.ABI
No change.
Validation
cargo test -p kandelo --target aarch64-apple-darwin --lib— 964 pass, including newtest_send_msg_nosignal_inet_loopback(loopback INET connect/accept → close server end →send(MSG_NOSIGNAL)→ assertEPIPE+ no pending SIGPIPE). Verified the test fails without the fix (SIGPIPE raised).scripts/check-abi-version.sh— snapshot in sync.🤖 Generated with Claude Code