mark arp broadcasts in the mbuf

[Camiel Dobbelaar]

Mark ARP request broadcasts as such in the mbuf flags.  FreeBSD and NetBSD 
both have this.

Without this, bridge_output() drops ARP request broadcasts on interfaces 
without the discover flag:

                        if ((p->bif_flags & IFBIF_DISCOVER) == 0 &&
                            (m->m_flags & (M_BCAST | M_MCAST)) == 0)
                                continue;


Index: if_ether.c
===================================================================
RCS file: /cvs/src/sys/netinet/if_ether.c,v
retrieving revision 1.88
diff -u -r1.88 if_ether.c
--- if_ether.c  22 Jul 2010 00:41:55 -0000      1.88
+++ if_ether.c  26 Jun 2011 17:30:29 -0000
@@ -359,6 +359,7 @@
        bcopy((caddr_t)tip, (caddr_t)ea->arp_tpa, sizeof(ea->arp_tpa));
        sa.sa_family = pseudo_AF_HDRCMPLT;
        sa.sa_len = sizeof(sa);
+       m->m_flags |= M_BCAST;
        (*ifp->if_output)(ifp, m, &sa, (struct rtentry *)0);
 }
 
@@ -994,6 +995,7 @@
           sizeof(ea->arp_tha));
        sa.sa_family = pseudo_AF_HDRCMPLT;
        sa.sa_len = sizeof(sa);
+       m->m_flags |= M_BCAST;
        ifp->if_output(ifp, m, &sa, (struct rtentry *)0);
 }