Fix the flooding procedure. Violate the RFC else many BAD_LS_REQ events and

session drops happend while booting up. If a router is conected to a other
router over two different interface one session will be unable to load until
the other one is in state FULL. ospfd no longer issues a BAD_LS_REQ event
if the LSA is equal to the one in table but if the sent lsa is older a
BAD_LS_REQ event is still issued.  OK norby@

2 files changed, 40 insertions, 20 deletions

diff --git a/usr.sbin/ospfd/iso_cksum.c b/usr.sbin/ospfd/iso_cksum.c
index f3a050b37fe..de8d2c6a156 100644
--- a/usr.sbin/ospfd/iso_cksum.c
+++ b/usr.sbin/ospfd/iso_cksum.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: iso_cksum.c,v 1.1 2005/01/28 14:05:40 claudio Exp $ */
+/*	$OpenBSD: iso_cksum.c,v 1.2 2005/10/12 09:51:58 claudio Exp $ */
 
 /*
  * Copyright (c) 2005 Claudio Jeker <claudio@openbsd.org>
@@ -21,17 +21,18 @@
 #include "ospfd.h"
 #include "log.h"
 
+/* implementation of Fletcher Checksum -- see RFC 1008 for more info */
+
 /* pos needs to be 0 for verify and 2 <= pos < len for calculation */
 u_int16_t
 iso_cksum(void *buf, u_int16_t len, u_int16_t pos)
 {
 	u_int8_t	*p = buf;
-	int		 c0 = 0, c1 = 0;	/* counters */
-	int		 r0, r1;		/* results */
+	int		 c0 = 0, c1 = 0, x;	/* counters */
 	u_int16_t	 sop;
 
-	sop = len - pos - 1;	/* pos is an offset (pos 2 is at len 3) */
-	p += 2;
+	sop = len - pos - 1;	/* pos is an offset (pos 2 is 3rd element) */
+	p += 2;			/* jump over age field */
 	len -= 2;
 	while (len--) {
 		c0 += *p++;
@@ -41,18 +42,27 @@ iso_cksum(void *buf, u_int16_t len, u_int16_t pos)
 			c0 %= 255;
 			c1 %= 255;
 		}
+#ifdef DEBUG
+		if (c0 + 256 < c0 || c1 + 256 < c1)
+			fatalx("iso_cksum: overflowed");
+#endif
 	}
-	r0 = c0 = c0 % 255;
-	r1 = c1 % 255;
 
 	if (pos) {
-		r0 = ((sop * r0 - r1)) % 255;
-		if (r0 <= 0)
-			r0 += 255;
-		r1 = 510 - r0 - c0;
-		if (r1 > 255)
-			r1 -= 255;
+		x = ((sop * c0 - c1)) % 255;
+		if (x <= 0)
+			x += 255;
+#if 1
+		c1 = 510 - c0 - x;
+		if (c1 > 255)
+			c1 -= 255;
+#else
+		c1 = (-c0 - x) % 255;
+		if (c1 < 0)
+			c1 += 255;
+#endif
+		c0 = x;
 	}
 
-	return (r0 << 8 | r1);
+	return (c0 << 8 | c1);
 }
diff --git a/usr.sbin/ospfd/rde.c b/usr.sbin/ospfd/rde.c
index f538f41cde2..200d5fc3f13 100644
--- a/usr.sbin/ospfd/rde.c
+++ b/usr.sbin/ospfd/rde.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: rde.c,v 1.29 2005/10/12 09:42:57 claudio Exp $ */
+/*	$OpenBSD: rde.c,v 1.30 2005/10/12 09:51:58 claudio Exp $ */
 
 /*
  * Copyright (c) 2004, 2005 Claudio Jeker <claudio@openbsd.org>
@@ -402,20 +402,30 @@ rde_dispatch_imsg(int fd, short event, void *bula)
 				/* lsa not added so free it */
 				if (self)
 					free(lsa);
-			} else if (rde_req_list_exists(nbr, &lsa->hdr)) {
-				/* lsa no longer needed */
-				free(lsa);
-				imsg_compose(ibuf_ospfe, IMSG_LS_BADREQ,
-				    imsg.hdr.peerid, 0, -1, NULL, 0);
 			} else if (r < 0) {
 				/* lsa no longer needed */
 				free(lsa);
 
+				/*
+				 * point 6 of "The Flooding Procedure"
+				 * We are violating the RFC here because
+				 * it does not make sense to reset a session
+				 * because a equal LSA is already in the table.
+				 * Only if the LSA sent is older than the one
+				 * in the table we should reset the session.
+				 */
+				if (rde_req_list_exists(nbr, &lsa->hdr)) {
+					imsg_compose(ibuf_ospfe, IMSG_LS_BADREQ,
+					    imsg.hdr.peerid, 0, -1, NULL, 0);
+					break;
+				}
+
 				/* new LSA older than DB */
 				if (ntohl(db_hdr->seq_num) == MAX_SEQ_NUM &&
 				    ntohs(db_hdr->age) == MAX_AGE)
 					/* seq-num wrap */
 					break;
+
 				if (v->changed + MIN_LS_ARRIVAL >= now)
 					break;