From: Su Xuemin <s...@chinanetcenter.com> Date: Mon, 13 Jun 2016 11:02:50 +0800
> From: "Su, Xuemin" <s...@chinanetcenter.com> > > There is a corner case in which udp packets belonging to a same > flow are hashed to different socket when hslot->count changes from 10 > to 11: > > 1) When hslot->count <= 10, __udp_lib_lookup() searches udp_table->hash, > and always passes 'daddr' to udp_ehashfn(). > > 2) When hslot->count > 10, __udp_lib_lookup() searches udp_table->hash2, > but may pass 'INADDR_ANY' to udp_ehashfn() if the sockets are bound to > INADDR_ANY instead of some specific addr. > > That means when hslot->count changes from 10 to 11, the hash calculated by > udp_ehashfn() is also changed, and the udp packets belonging to a same > flow will be hashed to different socket. > > This is easily reproduced: > 1) Create 10 udp sockets and bind all of them to 0.0.0.0:40000. > 2) From the same host send udp packets to 127.0.0.1:40000, record the > socket index which receives the packets. > 3) Create 1 more udp socket and bind it to 0.0.0.0:44096. The number 44096 > is 40000 + UDP_HASH_SIZE(4096), this makes the new socket put into the > same hslot as the aformentioned 10 sockets, and makes the hslot->count > change from 10 to 11. > 4) From the same host send udp packets to 127.0.0.1:40000, and the socket > index which receives the packets will be different from the one received > in step 2. > This should not happen as the socket bound to 0.0.0.0:44096 should not > change the behavior of the sockets bound to 0.0.0.0:40000. > > It's the same case for IPv6, and this patch also fixes that. > > Signed-off-by: Su, Xuemin <s...@chinanetcenter.com> > Signed-off-by: Eric Dumazet <eduma...@google.com> Applied and queued up for -stable, thanks.
