set ISC_SOCKEVENTATTR_MULTICAST on packets received from a multicast address

lib/isc/include/isc/socket.h

@@ -122,6 +122,7 @@ struct isc_socket_connev {
  *		all the data is valid.
  * _TIMESTAMP:	The timestamp member is valid.
  * _PKTINFO:	The pktinfo member is valid.
+ * _MULTICAST:	The UDP packet was received via a multicast transmission.
  */
 #define ISC_SOCKEVENTATTR_ATTACHED		0x80000000U /* internal */
 #define ISC_SOCKEVENTATTR_FATALERROR		0x40000000U /* sock is dead */
@@ -129,6 +130,7 @@ struct isc_socket_connev {
 #define ISC_SOCKEVENTATTR_CTRUNC		0x00400000U /* public */
 #define ISC_SOCKEVENTATTR_TIMESTAMP		0x00200000U /* public */
 #define ISC_SOCKEVENTATTR_PKTINFO		0x00100000U /* public */
+#define ISC_SOCKEVENTATTR_MULTICAST		0x00080000U /* public */
 
 #define ISC_SOCKEVENT_ANYEVENT  (0)
 #define ISC_SOCKEVENT_RECVDONE	(ISC_EVENTCLASS_SOCKET + 1)

lib/isc/unix/socket.c

@@ -366,6 +366,12 @@ process_cmsg(isc_socket_t *sock, struct msghdr *msg, isc_socketevent_t *dev) {
 		dev->attributes |= ISC_SOCKEVENTATTR_CTRUNC;
 #endif
 
+	/*
+	 * Check for multicast.
+	 */
+	if (isc_sockaddr_ismulticast(&dev->address))
+		dev->attributes |= ISC_SOCKEVENTATTR_MULTICAST;
+
 #ifndef USE_CMSG
 	return;
 #else
@@ -1171,6 +1177,15 @@ isc_socket_create(isc_socketmgr_t *manager, int pf, isc_sockettype_t type,
 					 "setsockopt(%d) failed: %s",
 					 sock->fd, strerror(errno));
 		}
+
+#ifdef IPV6_USE_MIN_MTU        /*2292bis, not too common yet*/
+		/* use minimum MTU */
+		if (pf == AF_INET6) {
+			(void)setsockopt(sock->fd, IPPROTO_IPV6,
+					 IPV6_USE_MIN_MTU,
+					 (void *)&on, sizeof (on));
+		}
+#endif
 #endif /* ISC_PLATFORM_HAVEIPV6 */
 
 	}
@@ -2667,6 +2682,9 @@ isc_socket_connect(isc_socket_t *sock, isc_sockaddr_t *addr,
 	REQUIRE(VALID_MANAGER(manager));
 	REQUIRE(addr != NULL);
 
+	if (isc_sockaddr_ismulticast(addr))
+		return (ISC_R_MULTICAST);
+
 	LOCK(&sock->lock);
 
 	REQUIRE(!sock->connecting);