This gist documents subtle behavioral quirks of the SCM_RIGHTS ancillary message API on Linux, explaining how received messages may be coalesced or split across recvmsg() calls. It notes that the recvmsg() receiving the first byte of an ancillary message's data range will also receive that ancillary message, and the kernel artificially limits that call to prevent multiple ancillary messages from being delivered simultaneously.
Background
SCM_RIGHTS is a Unix domain socket ancillary message mechanism used to pass file descriptors between processes, widely employed in service architectures like systemd socket activation and capability-based IPC systems.
- Source
- Lobsters
- Published
- Aug 17, 2026 at 12:12 PM
- Score
- 5.0 / 10