Fix a bug in if_findmulti(), whereby it would not find (and thus delete)

a link-layer multicast group membership.
Such memberships are needed in order to support protocols such as
IS-IS without putting the interface into PROMISC or ALLMULTI modes.

sa_equal() is not OK for comparing sockaddr_dl as it has deeper structure
than a simple byte array, so add sa_dl_equal() and use that instead.

Reviewed by:	rwatson
Verified with:	/usr/sbin/mtest
Bug found by:	Jouke Witteveen
MFC after:	2 weeks

1 files changed, 22 insertions, 3 deletions

diff --git a/sys/net/if.c b/sys/net/if.c
index 6d693df..04e8310 100644
--- a/sys/net/if.c
+++ b/sys/net/if.c
@@ -978,7 +978,21 @@ if_rtdel(struct radix_node *rn, void *arg)
 	return (0);
 }
 
-#define	sa_equal(a1, a2)	(bcmp((a1), (a2), ((a1))->sa_len) == 0)
+/*
+ * XXX: Because sockaddr_dl has deeper structure than the sockaddr
+ * structs used to represent other address families, it is necessary
+ * to perform a different comparison.
+ */
+
+#define	sa_equal(a1, a2)	\
+	(bcmp((a1), (a2), ((a1))->sa_len) == 0)
+
+#define	sa_dl_equal(a1, a2)	\
+	((((struct sockaddr_dl *)(a1))->sdl_len ==			\
+	 ((struct sockaddr_dl *)(a2))->sdl_len) &&			\
+	 (bcmp(LLADDR((struct sockaddr_dl *)(a1)),			\
+	       LLADDR((struct sockaddr_dl *)(a2)),			\
+	       ((struct sockaddr_dl *)(a1))->sdl_alen) == 0))
 
 /*
  * Locate an interface based on a complete address.
@@ -2123,8 +2137,13 @@ if_findmulti(struct ifnet *ifp, struct sockaddr *sa)
 	IF_ADDR_LOCK_ASSERT(ifp);
 
 	TAILQ_FOREACH(ifma, &ifp->if_multiaddrs, ifma_link) {
-		if (sa_equal(ifma->ifma_addr, sa))
-			break;
+		if (sa->sa_family == AF_LINK) {
+			if (sa_dl_equal(ifma->ifma_addr, sa))
+				break;
+		} else {
+			if (sa_equal(ifma->ifma_addr, sa))
+				break;
+		}
 	}
 
 	return ifma;