Re: ioctl: SIOCADDMULTI (howto?)

Jouke Witteveen wrote:

I hope someone can find a spare minute to look at if_findmulti. It
would help me quite much.
I verified with mtest that FreeBSD cannot delete an AF_LINK multicast membership, reproduced with both 7-CURRENT and 6.2-RELEASE.

if_findmulti() appears to be doing a possibly incorrect comparison.
sa_equal() is not valid for use with AF_LINK in some cases, as sockaddr_dl has deeper structure than a simple array of bytes.

Thanks for finding this bug -- it would have affected XORP's IS-IS implementation further on in time.

Further testing would be appreciated. If the fix is good I will merge, though it should perhaps be a more general fix for sa_equal().

BMS Index: src/sys/net/if.c
===================================================================
RCS file: /home/ncvs/src/sys/net/if.c,v
retrieving revision 1.265
diff -u -p -r1.265 if.c
--- src/sys/net/if.c 30 Nov 2006 15:02:01 -0000 1.265
+++ src/sys/net/if.c 21 Feb 2007 00:34:12 -0000
@@ -2123,8 +2123,16 @@ if_findmulti(struct ifnet *ifp, struct s
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) {
+ struct sockaddr_dl *sdl = (struct sockaddr_dl *)sa;
+
+ if (bcmp(LLADDR((struct sockaddr_dl *)ifma->ifma_addr),
+ LLADDR(sdl), sdl->sdl_alen) == 0)
+ break;
+ } else {
+ if (sa_equal(ifma->ifma_addr, sa))
+ break;
+ }
}

return ifma;
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