Hi, I use unix domain datagram sockets for IPC, e.g. I receive messages by calling recv().
"man 2 recv" tells me about the flags argument to a recv() call, namely: MSG_TRUNC Return the real length of the packet, even when it was longer than the passed buffer. Only valid for packet sockets. Thus I used recv() with flags MSG_TRUNC|MSG_PEEK in order to detect message truncation due to insufficient buffer size. Strangely enough, MSG_TRUNC seems to get ignored by the kernel: If the message received is larger than the receive buffer I supplied, the function returns the size of the buffer. I think, the function should return the real message length instead (at least according to the manual page). To work around this problem, I now use the ioctl FIONREAD instead. On the other hand, in this mailing list, I found an old bug report describing the same problem using UDP sockets: http://groups.google.com/group/fa.linux.kernel/browse_frm/thread/fb6acbb527507e26/ad0b2ba33b6b66fa UDP sockets seem to have been patched by now. From linux/net/ipv4/udp.c: udp_recvmsg() ... err = copied; if (flags & MSG_TRUNC) err = skb->len - sizeof(struct udphdr); ... Why doesn't unix_dgram_recvmsg() in linux/net/unix/af_unix.c contain code to this effect? Is this a feature or a bug? What is the correct semantics of MSG_TRUNC when used for unix sockets? Cheers Daniel Kabs PS: According to some lkml archives, my previous mail did not come through, so I reposted it. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/