EmbeddingGemma 2: an open, lightweight multimodal embedding model
deepmind.google·6d ago
AI Engineering
Lobsters·Aug 17·5 min read
SCM_RIGHTS API quirks (2019)
TL;DR
SCM_RIGHTS ancillary messages are sent alongside data in sendmsg() calls, but their reception can be complex due to message coalescing and splitting. This can lead to unexpected behavior in how ancillary data is read by recvmsg() calls.
✦ Why It Matters
Ensure your buffer management in recvmsg() accounts for potential message coalescing to avoid data handling errors.
Key Takeaways
- Always allocate sufficient buffer space for ancillary messages.
- Be aware that recvmsg() can read beyond the intended message range.
- Monitor for potential descriptor loss when buffer limits are exceeded.
- Understand that regular read() calls may not indicate data availability accurately.
How It Works
SCM_RIGHTS messages are sent alongside data in a single sendmsg() call, allowing multiple file descriptors to be transmitted. The receiving end uses recvmsg() to retrieve both the data and the ancillary message, but the behavior can vary based on buffer size and message coalescing.
⚠ The Catch
If the buffer provided to recvmsg() is too small to accommodate all file descriptors, the excess descriptors are discarded, leading to potential data loss.