Kernel bug with UNIX sockets not detecting other end gone?

[Chris Evans]

Hi,

I wonder if the following is a bug? It certainly differs from FreeBSD 4.2
behaviour, which gives the behaviour I would expect.

The following program blocks indefinitely on Linux (2.2, 2.4 not tested).
Since the other end is clearly gone, I would expect some sort of error
condition. Indeed, FreeBSD gives ECONNRESET.

#include <sys/types.h>
#include <sys/socket.h>
#include <stdio.h>
#include <unistd.h>

int
main(int argc, const char* argv[])
{
  int the_sockets[2];
  int retval;
  char the_char;
  int opt = 1;

  retval = socketpair(PF_UNIX, SOCK_DGRAM, 0, the_sockets);
  if (retval != 0)
  {
    perror("socketpair");
    exit(1);
  }
  close(the_sockets[0]);
  /* Linux (2.2) blocks here; FreeBSD does not */
  retval = read(the_sockets[1], &the_char, sizeof(the_char));
}

Cheers
Chris