Re: [Qemu-devel] [PATCH] slirp: Fix error reported by static code analysis and remove wrong type casts

[Peter Maydell]

On 4 September 2012 08:27, Jan Kiszka <address@hidden> wrote:
> Indeed, this is a "XXX Should never fail" case - according to the code
> that checks tp at the call site. But as no one seriously understands
> slirp details, we are better safe than sorry.

Actually it looks like you can get here with both tp and m NULL:

 * we set up a non-blocking connect
 * at some point slirp.c:slirp_select_poll() finds the fd is writable
 * ...but the send() on slirp.c line 504 fails, so we set SS_NOFDREF
   in the so->so_state
 * on line 520 we call tcp_input() with m == NULL
 * tcp_input checks for m == NULL and immediately goes to cont_conn
 * if so->so_state & SS_NOFDREF we call tcp_close, which
   frees tp and returns 0
 * so we goto dropwithreset with tp NULL and m NULL
 * where we call tcp_respond to try to send a RST or RST|ACK

So I think you have to have failed a syscall for this to happen,
and if we haven't got an outbound fd then there's not a lot we
can do, so just returning from tcp_respond() seems like the best
thing.

-- PMM