slirp: goto bad in udp_input if sosendto fails

Before this patch, if sosendto fails, udp_input is executed as if the
packet was sent, recording the packet for icmp errors, which does not
makes sense since the packet was not actually sent, errors would be
related to a previous packet.

This patch adds a goto bad to cut the execution of this function.
Signed-off-by: NGuillaume Subiron <maethor@subiron.org>
Signed-off-by: NSamuel Thibault <samuel.thibault@ens-lyon.org>
Reviewed-by: NThomas Huth <thuth@redhat.com>
Signed-off-by: NJason Wang <jasowang@redhat.com>

slirp/udp.c

@@ -218,6 +218,7 @@ udp_input(register struct mbuf *m, int iphlen)
 	  *ip=save_ip;
 	  DEBUG_MISC((dfd,"udp tx errno = %d-%s\n",errno,strerror(errno)));
 	  icmp_error(m, ICMP_UNREACH,ICMP_UNREACH_NET, 0,strerror(errno));
+	  goto bad;
 	}
 
 	m_free(so->so_m);   /* used for ICMP if error on sorecvfrom */