package-nopast/network/pptpd/pptpd-1.3.4-pptpgre-out-of-order-sequence-number.patch

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From b99f5370362fe266b10dd195120c23e2bf64286f Mon Sep 17 00:00:00 2001
From: Christian Wiese <christian.wiese@securepoint.de>
Date: Wed, 24 Aug 2011 13:53:45 +0200
Subject: [PATCH] pptpgre: added check for out-of-order sequence number

Origin: http://marc.info/?l=poptop-server&m=117737453400588&w=2

Debian Bugs: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=416404
---
 pptpgre.c |   11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)

diff --git pptpd-1.3.4.orig/pptpgre.c 1.3.4/pptpgre.c
index 9efabae..d84ea9b 100644
--- pptpd-1.3.4.orig/pptpgre.c
+++ 1.3.4/pptpgre.c
@@ -403,15 +403,20 @@ int decaps_gre(int fd, int (*cb) (int cl, void *pack, unsigned len), int cl)
 			stats.rx_truncated++;
 			return 0;
 		}
-		/* check for out-of-order sequence number */
-		if (seq == gre.seq_recv + 1) {
+		/* check for out-of-order sequence number
+		 * N.B.: some client implementations violate RFC 2637
+		 * and start their sequence numbers at 1 instead of 0,
+		 * so we have to introduce a kludge to deal with it. 
+		 * on wrap we may allow an out of order packet to pass
+		*/
+		if (seq == gre.seq_recv + 1 || seq == 1) {
 			if (pptpctrl_debug)
 				syslog(LOG_DEBUG, "GRE: accepting packet #%d", 
 				       seq);
 			stats.rx_accepted++;
 			gre.seq_recv = seq;
 			return cb(cl, buffer + ip_len + headersize, payload_len);
-		} else if (seq == gre.seq_recv) {
+		} else if (!seq_greater(seq, gre.seq_recv)) {
 			if (pptpctrl_debug)
 				syslog(LOG_DEBUG,
 				       "GRE: discarding duplicate or old packet #%d (expecting #%d)", 
-- 
1.6.6.2