ospf6d: review LSA sequence number comparison
It seems that there is a bug in ospf6d in ospf6_lsa_compare(): If LSA A
has sequence number smaller than 0x80000000 and LSA B has sequence
number larger than 0x80000000, ospf6_lsa_compare() returns that B is
more recent than A, although RFC says that sequence numbers should be
compared as signed numbers (0x8000001 smallest and 0x7FFFFFFF largest).
In ospfd, the function ospf_lsa_more_recent() has it right.
The problem appears when Quagga is used together with OSPFv3 in
development version of BIRD daemon ( http://bird.network.cz/ ),
which creates LSAs with maximum sequence number (0x7FFFFFFF)
as a part of flushing/premature aging LSA from OSPF area.
Because both daemons has different idea of which LSA instance
is more recent, it would lead to LSA storm.
diff --git a/ospf6d/ospf6_lsa.c b/ospf6d/ospf6_lsa.c
index 07d9f91..c1db374 100644
--- a/ospf6d/ospf6_lsa.c
+++ b/ospf6d/ospf6_lsa.c
@@ -256,7 +256,7 @@
int
ospf6_lsa_compare (struct ospf6_lsa *a, struct ospf6_lsa *b)
{
- signed long seqnuma, seqnumb;
+ int seqnuma, seqnumb;
u_int16_t cksuma, cksumb;
u_int16_t agea, ageb;
@@ -264,16 +264,13 @@
assert (b && b->header);
assert (OSPF6_LSA_IS_SAME (a, b));
- seqnuma = ((signed long) ntohl (a->header->seqnum))
- - (signed long) INITIAL_SEQUENCE_NUMBER;
- seqnumb = ((signed long) ntohl (b->header->seqnum))
- - (signed long) INITIAL_SEQUENCE_NUMBER;
+ seqnuma = (int) ntohl (a->header->seqnum);
+ seqnumb = (int) ntohl (b->header->seqnum);
/* compare by sequence number */
- /* XXX, LS sequence number wrapping */
if (seqnuma > seqnumb)
return -1;
- else if (seqnuma < seqnumb)
+ if (seqnuma < seqnumb)
return 1;
/* Checksum */