svn commit: r206452 - head/sys/netinet

[Bruce M Simpson]

Author: bms
Date: Sat Apr 10 12:05:31 2010
New Revision: 206452
URL: http://svn.freebsd.org/changeset/base/206452

Log:
  Fix a few issues related to the legacy 4.4 BSD multicast APIs.
  
  IPv4 addresses can and do change during normal operation. Testing by
  pfSense developers exposed an issue where OpenOSPFD was using the IPv4
  address to leave the OSPF link-scope multicast groups on a dynamic
  OpenVPN tun interface, rather than using RFC 3678 with the interface
  index, which won't be raced when the interface's addresses change.
  
  In inp_join_group():
   If we are already a member of an ASM group, and IP_ADD_MEMBERSHIP or
   MCAST_JOIN_GROUP ioctls are re-issued, return EADDRINUSE as per the
   legacy 4.4BSD multicast API. This bends RFC 3678 slightly, but does
   not violate POLA for apps using the old API.
   It also stops us falling through to kicking IGMP state transactions
   in what is otherwise a no-op case.
   [This has already been dealt with in HEAD, but make it explicit before
    we MFC the change to 8.]
  
  In inp_leave_group():
   Fix a bogus conditional.
   Move the ifp null check to ioctls MCAST_LEAVE* in the switch..case
   where it actually belongs.
   If an interface was specified, by primary IPv4 address, for ioctl
   IP_DROP_MEMBERSHIP or MCAST_LEAVE_GROUP (an ASM full leave operation),
   then and only then should we look up the ifp from the IPv4 address in
   mreqs.imr_interface.
   If not, we fall through to imo_match_group() as before, but only in
   the IP_DROP_MEMBERSHIP case.
  
  With these changes, the legacy 4.4BSD multicast API idempotence should
  be mostly preserved in the SSM enabled IPv4 stack.
  
  Found by:	ermal (with pfSense)
  MFC after:	3 days

Modified:
  head/sys/netinet/in_mcast.c

Modified: head/sys/netinet/in_mcast.c
==============================================================================
--- head/sys/netinet/in_mcast.c	Sat Apr 10 11:52:12 2010	(r206451)
+++ head/sys/netinet/in_mcast.c	Sat Apr 10 12:05:31 2010	(r206452)
@@ -1999,9 +1999,12 @@ inp_join_group(struct inpcb *inp, struct
 			}
 		} else {
 			/*
-			 * MCAST_JOIN_GROUP alone, on any existing membership,
-			 * is rejected, to stop the same inpcb tying up
-			 * multiple refs to the in_multi.
+			 * MCAST_JOIN_GROUP on an existing exclusive
+			 * membership is an error; return EADDRINUSE
+			 * to preserve 4.4BSD API idempotence, and
+			 * avoid tedious detour to code below.
+			 * NOTE: This is bending RFC 3678 a bit.
+			 *
 			 * On an existing inclusive membership, this is also
 			 * an error; if you want to change filter mode,
 			 * you must use the userland API setsourcefilter().
@@ -2010,6 +2013,8 @@ inp_join_group(struct inpcb *inp, struct
 			 * is atomic with allocation of a membership.
 			 */
 			error = EINVAL;
+			if (imf->imf_st[1] == MCAST_EXCLUDE)
+				error = EADDRINUSE;
 			goto out_inp_locked;
 		}
 	}
@@ -2186,7 +2191,14 @@ inp_leave_group(struct inpcb *inp, struc
 			ssa->sin.sin_addr = mreqs.imr_sourceaddr;
 		}
 
-		if (!in_nullhost(gsa->sin.sin_addr))
+		/*
+		 * Attempt to look up hinted ifp from interface address.
+		 * Fallthrough with null ifp iff lookup fails, to
+		 * preserve 4.4BSD mcast API idempotence.
+		 * XXX NOTE WELL: The RFC 3678 API is preferred because
+		 * using an IPv4 address as a key is racy.
+		 */
+		if (!in_nullhost(mreqs.imr_interface))
 			INADDR_TO_IFP(mreqs.imr_interface, ifp);
 
 		CTR3(KTR_IGMPV3, "%s: imr_interface = %s, ifp = %p",
@@ -2222,6 +2234,9 @@ inp_leave_group(struct inpcb *inp, struc
 			return (EADDRNOTAVAIL);
 
 		ifp = ifnet_byindex(gsr.gsr_interface);
+
+		if (ifp == NULL)
+			return (EADDRNOTAVAIL);
 		break;
 
 	default:
@@ -2234,9 +2249,6 @@ inp_leave_group(struct inpcb *inp, struc
 	if (!IN_MULTICAST(ntohl(gsa->sin.sin_addr.s_addr)))
 		return (EINVAL);
 
-	if (ifp == NULL)
-		return (EADDRNOTAVAIL);
-
 	/*
 	 * Find the membership in the membership array.
 	 */