udp reuseport: fix packet of same flow hashed to different socket

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@chinanetcenter.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index ba0d8b8..ca5e8ea 100644 (file)
--- 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)
@@ -492,11 +446,11 @@ 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,
-               struct udp_hslot *hslot2, unsigned int slot2,
+               struct udp_hslot *hslot2,
                struct sk_buff *skb)
 {
        struct sock *sk, *result;
@@ -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;
@@ -554,17 +508,22 @@ struct sock *__udp4_lib_lookup(struct net *net, __be32 saddr,
 
                result = udp4_lib_lookup2(net, saddr, sport,
                                          daddr, hnum, dif,
-                                         hslot2, slot2, skb);
+                                         hslot2, skb);
                if (!result) {
+                       unsigned int old_slot2 = slot2;
                        hash2 = udp4_portaddr_hash(net, htonl(INADDR_ANY), hnum);
                        slot2 = hash2 & udptable->mask;
+                       /* avoid searching the same slot again. */
+                       if (unlikely(slot2 == old_slot2))
+                               return result;
+
                        hslot2 = &udptable->hash2[slot2];
                        if (hslot->count < hslot2->count)
                                goto begin;
 
                        result = udp4_lib_lookup2(net, saddr, sport,
-                                                 htonl(INADDR_ANY), hnum, dif,
-                                                 hslot2, slot2, skb);
+                                                 daddr, hnum, dif,
+                                                 hslot2, skb);
                }
                return result;
        }
@@ -572,8 +531,8 @@ 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..005dc82 100644 (file)
--- 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;
@@ -162,54 +161,11 @@ 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,
-               struct udp_hslot *hslot2, unsigned int slot2,
+               struct udp_hslot *hslot2,
                struct sk_buff *skb)
 {
        struct sock *sk, *result;
@@ -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;
@@ -268,17 +224,22 @@ struct sock *__udp6_lib_lookup(struct net *net,
 
                result = udp6_lib_lookup2(net, saddr, sport,
                                          daddr, hnum, dif,
-                                         hslot2, slot2, skb);
+                                         hslot2, skb);
                if (!result) {
+                       unsigned int old_slot2 = slot2;
                        hash2 = udp6_portaddr_hash(net, &in6addr_any, hnum);
                        slot2 = hash2 & udptable->mask;
+                       /* avoid searching the same slot again. */
+                       if (unlikely(slot2 == old_slot2))
+                               return result;
+
                        hslot2 = &udptable->hash2[slot2];
                        if (hslot->count < hslot2->count)
                                goto begin;
 
                        result = udp6_lib_lookup2(net, saddr, sport,
-                                                 &in6addr_any, hnum, dif,
-                                                 hslot2, slot2, skb);
+                                                 daddr, hnum, dif,
+                                                 hslot2, skb);
                }
                return result;
        }
@@ -286,7 +247,7 @@ 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) {