slirp: Only start packet expiration for delayed ones

The expiration timeout must only affect packets that are queued due to
pending ARP resolutions. The old version broke ping e.g.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

slirp/if.c

@@ -106,9 +106,6 @@ if_output(struct socket *so, struct mbuf *ifm)
 	ifs_init(ifm);
 	insque(ifm, ifq);
 
-        /* Expiration date = Now + 1 second */
-        ifm->expiration_date = qemu_get_clock_ns(rt_clock) + 1000000000ULL;
-
 diddit:
 	slirp->if_queued++;
 

slirp/slirp.c

@@ -738,6 +738,9 @@ int if_encap(Slirp *slirp, struct mbuf *ifm)
             slirp->client_ipaddr = iph->ip_dst;
             slirp_output(slirp->opaque, arp_req, sizeof(arp_req));
             ifm->arp_requested = true;
+
+            /* Expire request and drop outgoing packet after 1 second */
+            ifm->expiration_date = qemu_get_clock_ns(rt_clock) + 1000000000ULL;
         }
         return 0;
     } else {