Unnecessary lookup for every packet in ip_output()

[Martin Pieuchot]

Now that we can use the routing table to check if the destination
of a packet is a broadcast address, we can replace the lookup done
for every packet by the simple check below.

Ok?

Index: netinet/ip_output.c
===================================================================
RCS file: /home/ncvs/src/sys/netinet/ip_output.c,v
retrieving revision 1.267
diff -u -p -r1.267 ip_output.c
--- netinet/ip_output.c 27 Sep 2014 12:26:16 -0000      1.267
+++ netinet/ip_output.c 7 Oct 2014 10:09:56 -0000
@@ -484,8 +484,8 @@ reroute:
         * such a packet; if the packet is going in an IPsec tunnel, skip
         * this check.
         */
-       if ((sproto == 0) && (in_broadcast(dst->sin_addr, ifp,
-           m->m_pkthdr.ph_rtableid))) {
+       if ((sproto == 0) && ((dst->sin_addr.s_addr == INADDR_BROADCAST) ||
+           (ro && ro->ro_rt && ISSET(ro->ro_rt->rt_flags, RTF_BROADCAST)))) {
                if ((ifp->if_flags & IFF_BROADCAST) == 0) {
                        error = EADDRNOTAVAIL;
                        goto bad;