10.4/allow-forwarding-ip4-with-loopback-address-range.diff

Allow forwarding IPv4 packets from/to 127.0.0.0/8 except 127.0.0.1.

diff -ru --exclude-from freebsd-src-diff-exclude-names --new-file /var/archive3/public/freebsd-releng-10.4-src/sys/net/flowtable.c freebsd-10.4/sys/net/flowtable.c
--- /var/archive3/public/freebsd-releng-10.4-src/sys/net/flowtable.c	2017-09-29 08:20:07.000000000 +0800
+++ freebsd-10.4/sys/net/flowtable.c	2022-11-27 00:18:01.170901000 +0800
@@ -199,9 +199,10 @@
 	ip = mtod(m, struct ip *);
 
 	if (ip->ip_src.s_addr == ip->ip_dst.s_addr ||
-	    (ntohl(ip->ip_dst.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET ||
-	    (ntohl(ip->ip_src.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET)
+	    ntohl(ip->ip_dst.s_addr) == INADDR_LOOPBACK ||
+	    ntohl(ip->ip_src.s_addr) == INADDR_LOOPBACK) {
 		return (NULL);
+	}
 
 	fibnum = M_GETFIB(m);
 
diff -ru --exclude-from freebsd-src-diff-exclude-names --new-file /var/archive3/public/freebsd-releng-10.4-src/sys/netinet/in.c freebsd-10.4/sys/netinet/in.c
--- /var/archive3/public/freebsd-releng-10.4-src/sys/netinet/in.c	2017-09-29 08:20:06.000000000 +0800
+++ freebsd-10.4/sys/netinet/in.c	2022-11-26 20:53:07.717981000 +0800
@@ -139,11 +139,7 @@
 
 	if (IN_EXPERIMENTAL(i) || IN_MULTICAST(i) || IN_LINKLOCAL(i))
 		return (0);
-	if (IN_CLASSA(i)) {
-		net = i & IN_CLASSA_NET;
-		if (net == 0 || net == (IN_LOOPBACKNET << IN_CLASSA_NSHIFT))
-			return (0);
-	}
+	if (!(i & 0xff000000)) return 0;
 	return (1);
 }
 
diff -ru --exclude-from freebsd-src-diff-exclude-names --new-file /var/archive3/public/freebsd-releng-10.4-src/sys/netinet/ip_fastfwd.c freebsd-10.4/sys/netinet/ip_fastfwd.c
--- /var/archive3/public/freebsd-releng-10.4-src/sys/netinet/ip_fastfwd.c	2017-09-29 08:20:06.000000000 +0800
+++ freebsd-10.4/sys/netinet/ip_fastfwd.c	2022-11-27 00:23:34.897572000 +0800
@@ -273,10 +273,10 @@
 	}
 
 	/*
-	 * Is packet from or to 127/8?
+	 * Is packet from or to 127.0.0.1?
 	 */
-	if ((ntohl(ip->ip_dst.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET ||
-	    (ntohl(ip->ip_src.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET) {
+	if (ntohl(ip->ip_dst.s_addr) == INADDR_LOOPBACK ||
+	    ntohl(ip->ip_src.s_addr) == INADDR_LOOPBACK) {
 		IPSTAT_INC(ips_badaddr);
 		goto drop;
 	}
diff -ru --exclude-from freebsd-src-diff-exclude-names --new-file /var/archive3/public/freebsd-releng-10.4-src/sys/netinet/ip_input.c freebsd-10.4/sys/netinet/ip_input.c
--- /var/archive3/public/freebsd-releng-10.4-src/sys/netinet/ip_input.c	2017-09-29 08:20:06.000000000 +0800
+++ freebsd-10.4/sys/netinet/ip_input.c	2022-11-27 00:21:46.854283000 +0800
@@ -411,9 +411,10 @@
 	IP_PROBE(receive, NULL, NULL, ip, m->m_pkthdr.rcvif, ip, NULL);
 
 	/* 127/8 must not appear on wire - RFC1122 */
+	/* Modified to filter 127.0.0.1 only */
 	ifp = m->m_pkthdr.rcvif;
-	if ((ntohl(ip->ip_dst.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET ||
-	    (ntohl(ip->ip_src.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET) {
+	if (ntohl(ip->ip_dst.s_addr) == INADDR_LOOPBACK ||
+	    ntohl(ip->ip_src.s_addr) == INADDR_LOOPBACK) {
 		if ((ifp->if_flags & IFF_LOOPBACK) == 0) {
 			IPSTAT_INC(ips_badaddr);
 			goto bad;
diff -ru --exclude-from freebsd-src-diff-exclude-names --new-file /var/archive3/public/freebsd-releng-10.4-src/sys/netinet/ip_output.c freebsd-10.4/sys/netinet/ip_output.c
--- /var/archive3/public/freebsd-releng-10.4-src/sys/netinet/ip_output.c	2017-09-29 08:20:06.000000000 +0800
+++ freebsd-10.4/sys/netinet/ip_output.c	2022-11-27 00:22:12.011746000 +0800
@@ -577,8 +577,9 @@
 
 passout:
 	/* 127/8 must not appear on wire - RFC1122. */
-	if ((ntohl(ip->ip_dst.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET ||
-	    (ntohl(ip->ip_src.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET) {
+	/* Modified to filter 127.0.0.1 only */
+	if (ntohl(ip->ip_dst.s_addr) == INADDR_LOOPBACK ||
+	    ntohl(ip->ip_src.s_addr) == INADDR_LOOPBACK) {
 		if ((ifp->if_flags & IFF_LOOPBACK) == 0) {
 			IPSTAT_INC(ips_badaddr);
 			error = EADDRNOTAVAIL;