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.
The fix here is that when searching udp_table->hash, if the socket
supports reuseport, pass inet_sk(sk)->inet_rcv_saddr to udp_ehashfn()
instead of daddr. When the sockets are bound to some specific addr,
inet_sk(sk)->inet_rcv_saddr should equal to daddr, and when the sockets
are bould to INADDR_ANY, this will pass INADDR_ANY to udp_ehashfn() as
what is done when searching udp_table->hash2.
It's the same case for IPv6, and this patch also fixes that.
Signed-off-by: Su, Xuemin <s...@chinanetcenter.com>
---
The patch v1 does not fix the code in IPv6. Thank Eric Dumazet for
pointing that.
And I use this tree to generate this patch, hope it's correct:
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
net/ipv4/udp.c | 4 +++-
net/ipv6/udp.c | 4 +++-
2 files changed, 6 insertions(+), 2 deletions(-)
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index d56c055..57c38f6 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -577,7 +577,9 @@ begin:
if (score > badness) {
reuseport = sk->sk_reuseport;
if (reuseport) {
- hash = udp_ehashfn(net, daddr, hnum,
+ hash = udp_ehashfn(net,
+ inet_sk(sk)->inet_rcv_saddr,
+ hnum,
saddr, sport);
result = reuseport_select_sock(sk, hash, skb,
sizeof(struct udphdr));
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 2da1896..41ca493 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -290,7 +290,9 @@ begin:
if (score > badness) {
reuseport = sk->sk_reuseport;
if (reuseport) {
- hash = udp6_ehashfn(net, daddr, hnum,
+ hash = udp6_ehashfn(net,
+ &sk->sk_v6_rcv_saddr,
+ hnum,
saddr, sport);
result = reuseport_select_sock(sk, hash, skb,
sizeof(struct udphdr));
--
1.8.3.1
