From cb24e9343dfdd2c90611cefacb0016af3e769349 Mon Sep 17 00:00:00 2001
From: thompsa <thompsa@FreeBSD.org>
Date: Sun, 4 Sep 2011 22:06:32 +0000
Subject: [PATCH] On the first loop for generating a bridge MAC address use the
 local hostid, this gives a good chance of keeping the same address over
 reboots. This is intended to help IPV6 and similar which generate their
 addresses from the mac.

PR:		kern/160300
Submitted by:	mdodd
Approved by:	re (kib)
---
 sys/net/if_bridge.c | 27 +++++++++++++++++++++------
 1 file changed, 21 insertions(+), 6 deletions(-)

diff --git a/sys/net/if_bridge.c b/sys/net/if_bridge.c
index a4bf2b2a13be..c251653841f1 100644
--- a/sys/net/if_bridge.c
+++ b/sys/net/if_bridge.c
@@ -85,6 +85,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/malloc.h>
 #include <sys/protosw.h>
 #include <sys/systm.h>
+#include <sys/jail.h>
 #include <sys/time.h>
 #include <sys/socket.h> /* for net/if.h */
 #include <sys/sockio.h>
@@ -560,7 +561,8 @@ bridge_clone_create(struct if_clone *ifc, int unit, caddr_t params)
 {
 	struct bridge_softc *sc, *sc2;
 	struct ifnet *bifp, *ifp;
-	int retry;
+	int fb, retry;
+	unsigned long hostid;
 
 	sc = malloc(sizeof(*sc), M_DEVBUF, M_WAITOK|M_ZERO);
 	ifp = sc->sc_ifp = if_alloc(IFT_ETHER);
@@ -593,17 +595,30 @@ bridge_clone_create(struct if_clone *ifc, int unit, caddr_t params)
 	IFQ_SET_READY(&ifp->if_snd);
 
 	/*
-	 * Generate a random ethernet address with a locally administered
-	 * address.
+	 * Generate an ethernet address with a locally administered address.
 	 *
 	 * Since we are using random ethernet addresses for the bridge, it is
 	 * possible that we might have address collisions, so make sure that
 	 * this hardware address isn't already in use on another bridge.
+	 * The first try uses the hostid and falls back to arc4rand().
 	 */
+	fb = 0;
+	getcredhostid(curthread->td_ucred, &hostid);
 	for (retry = 1; retry != 0;) {
-		arc4rand(sc->sc_defaddr, ETHER_ADDR_LEN, 1);
-		sc->sc_defaddr[0] &= ~1;	/* clear multicast bit */
-		sc->sc_defaddr[0] |= 2;		/* set the LAA bit */
+		if (fb || hostid == 0) {
+			arc4rand(sc->sc_defaddr, ETHER_ADDR_LEN, 1);
+			sc->sc_defaddr[0] &= ~1;/* clear multicast bit */
+			sc->sc_defaddr[0] |= 2;	/* set the LAA bit */
+		} else {
+			sc->sc_defaddr[0] = 0x2;
+			sc->sc_defaddr[1] = (hostid >> 24) & 0xff;
+			sc->sc_defaddr[2] = (hostid >> 16) & 0xff;
+			sc->sc_defaddr[3] = (hostid >> 8 ) & 0xff;
+			sc->sc_defaddr[4] =  hostid        & 0xff;
+			sc->sc_defaddr[5] = ifp->if_dunit & 0xff;
+		}
+
+		fb = 1;
 		retry = 0;
 		mtx_lock(&bridge_list_mtx);
 		LIST_FOREACH(sc2, &bridge_list, sc_list) {