Put the bridge mac inheritance behind a sysctl with the default off as this

still needs all the edge cases fixed.

Submitted by:	Eygene Ryabinkin

2 files changed, 23 insertions, 2 deletions

diff --git a/share/man/man4/if_bridge.4 b/share/man/man4/if_bridge.4
index 3701acd..9eebe98 100644
--- a/share/man/man4/if_bridge.4
+++ b/share/man/man4/if_bridge.4
@@ -92,6 +92,22 @@ the same link addresses.
 The address can be changed by assigning the desired link address using
 .Xr ifconfig 8 .
 .Pp
+If
+.Xr sysctl 8
+node
+.Va net.link.bridge.inherit_mac
+has non-zero value, newly created bridge will inherit MAC address
+from its first member instead of choosing random link-level address.
+This will provide more predictable bridge MAC without any
+additional configuration, but currently this feature is known
+to break some L2 protocols, for example PPPoE that is provided
+by
+.Xr ng_pppoe 4
+and
+.Xr ppp 8 .
+Now this feature is considered as experimental and is turned off
+by-default.
+.Pp
 A bridge can be used to provide several services, such as a simple
 802.11-to-Ethernet bridge for wireless hosts, and traffic isolation.
 .Pp
diff --git a/sys/net/if_bridge.c b/sys/net/if_bridge.c
index 88eda1d..4e124d2 100644
--- a/sys/net/if_bridge.c
+++ b/sys/net/if_bridge.c
@@ -347,6 +347,7 @@ static int pfil_ipfw_arp = 0;   /* layer2 filter with ipfw */
 static int pfil_local_phys = 0; /* run pfil hooks on the physical interface for
                                    locally destined packets */
 static int log_stp   = 0;   /* log STP state changes */
+static int bridge_inherit_mac = 0;   /* share MAC with first bridge member */
 SYSCTL_INT(_net_link_bridge, OID_AUTO, pfil_onlyip, CTLFLAG_RW,
     &pfil_onlyip, 0, "Only pass IP packets when pfil is enabled");
 SYSCTL_INT(_net_link_bridge, OID_AUTO, ipfw_arp, CTLFLAG_RW,
@@ -360,6 +361,9 @@ SYSCTL_INT(_net_link_bridge, OID_AUTO, pfil_local_phys, CTLFLAG_RW,
     "Packet filter on the physical interface for locally destined packets");
 SYSCTL_INT(_net_link_bridge, OID_AUTO, log_stp, CTLFLAG_RW,
     &log_stp, 0, "Log STP state changes");
+SYSCTL_INT(_net_link_bridge, OID_AUTO, inherit_mac, CTLFLAG_RW,
+    &bridge_inherit_mac, 0,
+    "Inherit MAC address from the first bridge member");
 
 struct bridge_control {
 	int	(*bc_func)(struct bridge_softc *, void *);
@@ -923,7 +927,8 @@ bridge_delete_member(struct bridge_softc *sc, struct bridge_iflist *bif,
 	 * the mac address of the bridge to the address of the next member, or
 	 * to its default address if no members are left.
 	 */
-	if (!memcmp(IF_LLADDR(sc->sc_ifp), IF_LLADDR(ifs), ETHER_ADDR_LEN)) {
+	if (bridge_inherit_mac &&
+	    !memcmp(IF_LLADDR(sc->sc_ifp), IF_LLADDR(ifs), ETHER_ADDR_LEN)) {
 		if (LIST_EMPTY(&sc->sc_iflist))
 			bcopy(sc->sc_defaddr,
 			    IF_LLADDR(sc->sc_ifp), ETHER_ADDR_LEN);
@@ -1030,7 +1035,7 @@ bridge_ioctl_add(struct bridge_softc *sc, void *arg)
 	 * member and the MAC address of the bridge has not been changed from
 	 * the default randomly generated one.
 	 */
-	if (LIST_EMPTY(&sc->sc_iflist) &&
+	if (bridge_inherit_mac && LIST_EMPTY(&sc->sc_iflist) &&
 	    !memcmp(IF_LLADDR(sc->sc_ifp), sc->sc_defaddr, ETHER_ADDR_LEN))
 		bcopy(IF_LLADDR(ifs), IF_LLADDR(sc->sc_ifp), ETHER_ADDR_LEN);