I wrote:

> Can you build a custom kernel which [...]

Here's a diff. Remove or modify the printf()s if you wish.
It'd be nice to know exaclty which (if any) are triggered.


--- Ip_output.c.20	2005-11-14 20:28:03.000000000 -0800
+++ ip_output.c.20.test	2005-11-14 20:31:49.000000000 -0800
@@ -408,8 +408,12 @@
 			goto done;
 		}
 
+		if (IN_MULTICAST(ip->ip_src.s_addr)) {
+			printf("PR 7003 rides again\n");
+		}
 		goto sendit;
 	}
+
 #ifndef notdef
 	/*
 	 * If source address not specified yet, use address
@@ -418,7 +422,6 @@
 	if (in_nullhost(ip->ip_src))
 		ip->ip_src = ia->ia_addr.sin_addr;
 #endif
-
 	/*
 	 * packets with Class-D address as source are not valid per
 	 * RFC 1112
@@ -453,6 +456,26 @@
 		m->m_flags &= ~M_BCAST;
 
 sendit:
+#ifndef notdef
+	/*
+	 * If source address not specified yet, use address
+	 * of outgoing interface.
+	 */
+	if (in_nullhost(ip->ip_src))
+		ip->ip_src = ia->ia_addr.sin_addr;
+#endif
+
+	/*
+	 * packets with Class-D address as source are not valid per
+	 * RFC 1112
+	 */
+	if (IN_MULTICAST(ip->ip_src.s_addr)) {
+		ipstat.ips_odropped++;
+		error = EADDRNOTAVAIL;
+		printf("XXX: Class_D source address\n");
+		goto bad;
+	}
+
 	/*
 	 * If we're doing Path MTU Discovery, we need to set DF unless
 	 * the route's MTU is locked.