--- linux-2.2.14/net/ipv4/route.c	Tue Jan  4 19:12:26 2000
+++ linux/net/ipv4/route.c	Thu Apr 27 16:30:23 2000
@@ -52,6 +52,7 @@
  *	Tobias Ringstrom	:	Uninitialized res.type in ip_route_output_slow.
  *	Vladimir V. Ivanov	:	IP rule info (flowid) is really useful.
  *		Marc Boucher	:	routing by fwmark
+ *		Rene Mayrhofer	:	valid packet rejected bug in ip_route_input_slow
  *
  *		This program is free software; you can redistribute it and/or
  *		modify it under the terms of the GNU General Public License
@@ -93,6 +94,9 @@
 #ifdef CONFIG_SYSCTL
 #include <linux/sysctl.h>
 #endif
+#ifdef CONFIG_IP_MASQUERADE
+#include <net/ip_masq.h>
+#endif
 
 #define IP_MAX_MTU	0xFFF0
 
@@ -1182,8 +1186,28 @@
 		int result;
 		result = fib_validate_source(saddr, daddr, tos, loopback_dev.ifindex,
 					     dev, &spec_dst, &itag);
-		if (result < 0)
+		if (result < 0) {
+#ifdef CONFIG_IP_MASQUERADE
+			/*
+			 * Is this packet going to be demasqueraded ? 
+			 * In that case, fib_validate_source returns an error when there is no
+			 * default route for packets coming from loopback and rp_filter is
+			 * activated for the interface that the returning packet has been 
+			 * recieved on.
+			 * But in such a special case (a combination of source-based routing
+			 * and masquerading), the returning packet is indeed valid. It will 
+			 * get demasqueraded later on.
+			 */
+			{
+				struct sk_buff *tmp = skb;
+				if(ip_fw_demasquerade(&tmp) <= 0) {
+					goto martian_source;
+				}
+			}
+#else
 			goto martian_source;
+#endif
+		}
 		if (result)
 			flags |= RTCF_DIRECTSRC;
 		spec_dst = daddr;