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. Reported-by: Juliusz Chroboczek <jch@irif.fr> Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk> --- proto/babel/babel.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/proto/babel/babel.c b/proto/babel/babel.c index ff8b6b52ef4a..a20bd72456bb 100644 --- a/proto/babel/babel.c +++ b/proto/babel/babel.c @@ -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; -- 2.39.1