net: fix inet_getid() and ipv6_select_ident() bugs
I noticed we were sending wrong IPv4 ID in TCP flows when MTU discovery
is disabled.
Note how GSO/TSO packets do not have monotonically incrementing ID.
06:37:41.575531 IP (id 14227, proto: TCP (6), length: 4396)
06:37:41.575534 IP (id 14272, proto: TCP (6), length: 65212)
06:37:41.575544 IP (id 14312, proto: TCP (6), length: 57972)
06:37:41.575678 IP (id 14317, proto: TCP (6), length: 7292)
06:37:41.575683 IP (id 14361, proto: TCP (6), length: 63764)
It appears I introduced this bug in linux-3.1.
inet_getid() must return the old value of peer->ip_id_count,
not the new one.
Lets revert this part, and remove the prevention of
a null identification field in IPv6 Fragment Extension Header,
which is dubious and not even done properly.
Fixes: 87c48fa3b463 ("ipv6: make fragment identifications less predictable")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/inetpeer.h b/include/net/inetpeer.h
index 6efe73c..058271b 100644
--- a/include/net/inetpeer.h
+++ b/include/net/inetpeer.h
@@ -177,16 +177,9 @@
/* can be called with or without local BH being disabled */
static inline int inet_getid(struct inet_peer *p, int more)
{
- int old, new;
more++;
inet_peer_refcheck(p);
- do {
- old = atomic_read(&p->ip_id_count);
- new = old + more;
- if (!new)
- new = 1;
- } while (atomic_cmpxchg(&p->ip_id_count, old, new) != old);
- return new;
+ return atomic_add_return(more, &p->ip_id_count) - more;
}
#endif /* _NET_INETPEER_H */