Comment 1 for bug 1823790

As described on the systemd issue, the syscall we're getting wrong here is getsockopt(fd, SOL_SOCKET, SO_PEERSEC, ...). Our linux-user/syscall.c:do_getsockopt() doesn't have any special case code for the payload on this function, so we treat it as if it were just an integer payload, which is not correct here.

Unfortunately I can't find any documentation on exactly what SO_PEERSEC does or what the payload format is, which makes it pretty hard to fix this bug :-( It's not listed in the socket(7) manpage -- https://linux.die.net/man/7/socket -- which is where I'd expect to find it, and the kernel source code is pretty confusing in this area.