From: Eric Dumazet <edumazet@xxxxxxxxxx>
3.12-stable review patch. If anyone has any objections, please let me know.
===============
[ Upstream commit 39c36094d78c39e038c1e499b2364e13bce36f54 ]
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@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
include/net/inetpeer.h | 9 +--------
net/ipv6/output_core.c | 11 +++--------
2 files changed, 4 insertions(+), 16 deletions(-)
diff --git a/include/net/inetpeer.h b/include/net/inetpeer.h
index 53f464d7cddc..6ca347a0717e 100644
--- a/include/net/inetpeer.h
+++ b/include/net/inetpeer.h
@@ -178,16 +178,9 @@ static inline void inet_peer_refcheck(const struct inet_peer *p)
/* 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 */
diff --git a/net/ipv6/output_core.c b/net/ipv6/output_core.c
index 827f795209cf..b31a01263185 100644
--- a/net/ipv6/output_core.c
+++ b/net/ipv6/output_core.c
@@ -10,7 +10,7 @@
void ipv6_select_ident(struct frag_hdr *fhdr, struct rt6_info *rt)
{
static atomic_t ipv6_fragmentation_id;
- int old, new;
+ int ident;
#if IS_ENABLED(CONFIG_IPV6)
if (rt && !(rt->dst.flags & DST_NOPEER)) {
@@ -26,13 +26,8 @@ void ipv6_select_ident(struct frag_hdr *fhdr, struct rt6_info *rt)
}
}
#endif
- do {
- old = atomic_read(&ipv6_fragmentation_id);
- new = old + 1;
- if (!new)
- new = 1;
- } while (atomic_cmpxchg(&ipv6_fragmentation_id, old, new) != old);
- fhdr->identification = htonl(new);
+ ident = atomic_inc_return(&ipv6_fragmentation_id);
+ fhdr->identification = htonl(ident);
}
EXPORT_SYMBOL(ipv6_select_ident);
--
2.0.0
--
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