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Date: Sun, 12 Jun 2016 20:43:27 +0800
From: Su Xuemin <suxm@...nanetcenter.com>
To: "David S. Miller" <davem@...emloft.net>,
Alexey Kuznetsov <kuznet@....inr.ac.ru>,
James Morris <jmorris@...ei.org>,
Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
Patrick McHardy <kaber@...sh.net>, netdev@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, suxm@...nanetcenter.com,
Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH v3] udp reuseport: fix packet of same flow hashed to different socket
From: "Su, Xuemin" <suxm@...nanetcenter.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 <suxm@...nanetcenter.com>
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
I use this tree to generate the patch:
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
net/ipv4/udp.c | 68 ++++++++++++----------------------------------------------
net/ipv6/udp.c | 66 ++++++++++++--------------------------------------------
2 files changed, 28 insertions(+), 106 deletions(-)
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 0ff31d9..586f1b0 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -391,9 +391,9 @@ int udp_v4_get_port(struct sock *sk, unsigned short snum)
return udp_lib_get_port(sk, snum, ipv4_rcv_saddr_equal, hash2_nulladdr);
}
-static inline int compute_score(struct sock *sk, struct net *net,
- __be32 saddr, unsigned short hnum, __be16 sport,
- __be32 daddr, __be16 dport, int dif)
+static int compute_score(struct sock *sk, struct net *net,
+ __be32 saddr, __be16 sport,
+ __be32 daddr, unsigned short hnum, int dif)
{
int score;
struct inet_sock *inet;
@@ -434,52 +434,6 @@ static inline int compute_score(struct sock *sk, struct net *net,
return score;
}
-/*
- * In this second variant, we check (daddr, dport) matches (inet_rcv_sadd, inet_num)
- */
-static inline int compute_score2(struct sock *sk, struct net *net,
- __be32 saddr, __be16 sport,
- __be32 daddr, unsigned int hnum, int dif)
-{
- int score;
- struct inet_sock *inet;
-
- if (!net_eq(sock_net(sk), net) ||
- ipv6_only_sock(sk))
- return -1;
-
- inet = inet_sk(sk);
-
- if (inet->inet_rcv_saddr != daddr ||
- inet->inet_num != hnum)
- return -1;
-
- score = (sk->sk_family == PF_INET) ? 2 : 1;
-
- if (inet->inet_daddr) {
- if (inet->inet_daddr != saddr)
- return -1;
- score += 4;
- }
-
- if (inet->inet_dport) {
- if (inet->inet_dport != sport)
- return -1;
- score += 4;
- }
-
- if (sk->sk_bound_dev_if) {
- if (sk->sk_bound_dev_if != dif)
- return -1;
- score += 4;
- }
-
- if (sk->sk_incoming_cpu == raw_smp_processor_id())
- score++;
-
- return score;
-}
-
static u32 udp_ehashfn(const struct net *net, const __be32 laddr,
const __u16 lport, const __be32 faddr,
const __be16 fport)
@@ -492,7 +446,7 @@ static u32 udp_ehashfn(const struct net *net, const __be32 laddr,
udp_ehash_secret + net_hash_mix(net));
}
-/* called with read_rcu_lock() */
+/* called with rcu_read_lock() */
static struct sock *udp4_lib_lookup2(struct net *net,
__be32 saddr, __be16 sport,
__be32 daddr, unsigned int hnum, int dif,
@@ -506,7 +460,7 @@ static struct sock *udp4_lib_lookup2(struct net *net,
result = NULL;
badness = 0;
udp_portaddr_for_each_entry_rcu(sk, &hslot2->head) {
- score = compute_score2(sk, net, saddr, sport,
+ score = compute_score(sk, net, saddr, sport,
daddr, hnum, dif);
if (score > badness) {
reuseport = sk->sk_reuseport;
@@ -556,14 +510,20 @@ struct sock *__udp4_lib_lookup(struct net *net, __be32 saddr,
daddr, hnum, dif,
hslot2, slot2, skb);
if (!result) {
+ unsigned int old = hash2;
hash2 = udp4_portaddr_hash(net, htonl(INADDR_ANY), hnum);
+
+ /* avoid search the same slot again. */
+ if (unlikely(old == hash2))
+ return result;
+
slot2 = hash2 & udptable->mask;
hslot2 = &udptable->hash2[slot2];
if (hslot->count < hslot2->count)
goto begin;
result = udp4_lib_lookup2(net, saddr, sport,
- htonl(INADDR_ANY), hnum, dif,
+ daddr, hnum, dif,
hslot2, slot2, skb);
}
return result;
@@ -572,8 +532,8 @@ begin:
result = NULL;
badness = 0;
sk_for_each_rcu(sk, &hslot->head) {
- score = compute_score(sk, net, saddr, hnum, sport,
- daddr, dport, dif);
+ score = compute_score(sk, net, saddr, sport,
+ daddr, hnum, dif);
if (score > badness) {
reuseport = sk->sk_reuseport;
if (reuseport) {
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index f421c9f..7c833dd 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -115,11 +115,10 @@ static void udp_v6_rehash(struct sock *sk)
udp_lib_rehash(sk, new_hash);
}
-static inline int compute_score(struct sock *sk, struct net *net,
- unsigned short hnum,
- const struct in6_addr *saddr, __be16 sport,
- const struct in6_addr *daddr, __be16 dport,
- int dif)
+static int compute_score(struct sock *sk, struct net *net,
+ const struct in6_addr *saddr, __be16 sport,
+ const struct in6_addr *daddr, unsigned short hnum,
+ int dif)
{
int score;
struct inet_sock *inet;
@@ -162,50 +161,7 @@ static inline int compute_score(struct sock *sk, struct net *net,
return score;
}
-static inline int compute_score2(struct sock *sk, struct net *net,
- const struct in6_addr *saddr, __be16 sport,
- const struct in6_addr *daddr,
- unsigned short hnum, int dif)
-{
- int score;
- struct inet_sock *inet;
-
- if (!net_eq(sock_net(sk), net) ||
- udp_sk(sk)->udp_port_hash != hnum ||
- sk->sk_family != PF_INET6)
- return -1;
-
- if (!ipv6_addr_equal(&sk->sk_v6_rcv_saddr, daddr))
- return -1;
-
- score = 0;
- inet = inet_sk(sk);
-
- if (inet->inet_dport) {
- if (inet->inet_dport != sport)
- return -1;
- score++;
- }
-
- if (!ipv6_addr_any(&sk->sk_v6_daddr)) {
- if (!ipv6_addr_equal(&sk->sk_v6_daddr, saddr))
- return -1;
- score++;
- }
-
- if (sk->sk_bound_dev_if) {
- if (sk->sk_bound_dev_if != dif)
- return -1;
- score++;
- }
-
- if (sk->sk_incoming_cpu == raw_smp_processor_id())
- score++;
-
- return score;
-}
-
-/* called with read_rcu_lock() */
+/* called with rcu_read_lock() */
static struct sock *udp6_lib_lookup2(struct net *net,
const struct in6_addr *saddr, __be16 sport,
const struct in6_addr *daddr, unsigned int hnum, int dif,
@@ -219,7 +175,7 @@ static struct sock *udp6_lib_lookup2(struct net *net,
result = NULL;
badness = -1;
udp_portaddr_for_each_entry_rcu(sk, &hslot2->head) {
- score = compute_score2(sk, net, saddr, sport,
+ score = compute_score(sk, net, saddr, sport,
daddr, hnum, dif);
if (score > badness) {
reuseport = sk->sk_reuseport;
@@ -270,14 +226,20 @@ struct sock *__udp6_lib_lookup(struct net *net,
daddr, hnum, dif,
hslot2, slot2, skb);
if (!result) {
+ unsigned int old = hash2;
hash2 = udp6_portaddr_hash(net, &in6addr_any, hnum);
+
+ /* avoid search the same slot again. */
+ if (unlikely(old == hash2))
+ return result;
+
slot2 = hash2 & udptable->mask;
hslot2 = &udptable->hash2[slot2];
if (hslot->count < hslot2->count)
goto begin;
result = udp6_lib_lookup2(net, saddr, sport,
- &in6addr_any, hnum, dif,
+ daddr, hnum, dif,
hslot2, slot2, skb);
}
return result;
@@ -286,7 +248,7 @@ begin:
result = NULL;
badness = -1;
sk_for_each_rcu(sk, &hslot->head) {
- score = compute_score(sk, net, hnum, saddr, sport, daddr, dport, dif);
+ score = compute_score(sk, net, saddr, sport, daddr, hnum, dif);
if (score > badness) {
reuseport = sk->sk_reuseport;
if (reuseport) {
--
1.8.3.1
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