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Babel: Fix missing modulo comparison of seqnos

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Juliusz noticed there were a couple of places we were doing straight
inequality comparisons of seqnos in Babel. This is wrong because seqnos can
wrap: so we need to use the modulo-64k comparison function for these cases
as well.

Introduce a strict-inequality version of the modulo-comparison for this
purpose.
This commit is contained in:
Toke Høiland-Jørgensen 2023-01-30 23:36:39 +01:00 committed by Ondrej Zajicek
parent 72230d3ca3
commit 3e7e4a7186
1 changed files with 6 additions and 2 deletions
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8
proto/babel/babel.c
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@ -49,6 +49,10 @@
static inline int ge_mod64k(uint a, uint b)
{ return (u16)(a - b) < 0x8000; }
/* Strict inequality version of the above */
static inline int gt_mod64k(uint a, uint b)
{ return ge_mod64k(a, b) && a != b; }
static void babel_expire_requests(struct babel_proto *p, struct babel_entry *e);
static void babel_select_route(struct babel_proto *p, struct babel_entry *e, struct babel_route *mod);
static inline void babel_announce_retraction(struct babel_proto *p, struct babel_entry *e);
@ -559,7 +563,7 @@ babel_is_feasible(struct babel_source *s, u16 seqno, u16 metric)
{
return !s ||
(metric == BABEL_INFINITY) ||
(seqno > s->seqno) ||
gt_mod64k(seqno, s->seqno) ||
((seqno == s->seqno) && (metric < s->metric));
}
@ -1013,7 +1017,7 @@ babel_send_update_(struct babel_iface *ifa, btime changed, struct fib *rtable)
struct babel_source *s = babel_get_source(p, e, e->router_id);
s->expires = current_time() + BABEL_GARBAGE_INTERVAL;
if ((msg.update.seqno > s->seqno) ||
if (gt_mod64k(msg.update.seqno, s->seqno) ||
((msg.update.seqno == s->seqno) && (msg.update.metric < s->metric)))
{
s->seqno = msg.update.seqno;