[PATCH] INET : IPV4 UDP lookups converted to a 2 pass algo

Some people want to have many UDP sockets, binded to a single port but
many different addresses. We currently hash all those sockets into a
single chain.  Processing of incoming packets is very expensive,
because the whole chain must be examined to find the best match.

I chose in this patch to hash UDP sockets with a hash function that
take into account both their port number and address : This has a
drawback because we need two lookups : one with a given address, one
with a wildcard (null) address.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 114 insertions, 57 deletions

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index cec0f2cc49b7..144970704c2c 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -114,14 +114,33 @@ DEFINE_RWLOCK(udp_hash_lock);
 
 static int udp_port_rover;
 
-static inline int __udp_lib_lport_inuse(__u16 num, struct hlist_head udptable[])
+/*
+ * Note about this hash function :
+ * Typical use is probably daddr = 0, only dport is going to vary hash
+ */
+static inline unsigned int hash_port_and_addr(__u16 port, __be32 addr)
+{
+        addr ^= addr >> 16;
+        addr ^= addr >> 8;
+        return port ^ addr;
+}
+
+static inline int __udp_lib_port_inuse(unsigned int hash, int port,
+        __be32 daddr, struct hlist_head udptable[])
 {
         struct sock *sk;
         struct hlist_node *node;
+        struct inet_sock *inet;
 
-        sk_for_each(sk, node, &udptable[num & (UDP_HTABLE_SIZE - 1)])
-                if (sk->sk_hash == num)
+        sk_for_each(sk, node, &udptable[hash & (UDP_HTABLE_SIZE - 1)]) {
+                if (sk->sk_hash != hash)
+                        continue;
+                inet = inet_sk(sk);
+                if (inet->num != port)
+                        continue;
+                if (inet->rcv_saddr == daddr)
                         return 1;
+        }
         return 0;
 }
 
@@ -142,6 +161,7 @@ int __udp_lib_get_port(struct sock *sk, unsigned short snum,
         struct hlist_node *node;
         struct hlist_head *head;
         struct sock *sk2;
+        unsigned int hash;
         int    error = 1;
 
         write_lock_bh(&udp_hash_lock);
@@ -156,7 +176,9 @@ int __udp_lib_get_port(struct sock *sk, unsigned short snum,
                 for (i = 0; i < UDP_HTABLE_SIZE; i++, result++) {
                         int size;
 
-                        head = &udptable[result & (UDP_HTABLE_SIZE - 1)];
+                        hash = hash_port_and_addr(result,
+                                        inet_sk(sk)->rcv_saddr);
+                        head = &udptable[hash & (UDP_HTABLE_SIZE - 1)];
                         if (hlist_empty(head)) {
                                 if (result > sysctl_local_port_range[1])
                                         result = sysctl_local_port_range[0] +
@@ -181,7 +203,10 @@ int __udp_lib_get_port(struct sock *sk, unsigned short snum,
                                 result = sysctl_local_port_range[0]
                                         + ((result - sysctl_local_port_range[0]) &
                                            (UDP_HTABLE_SIZE - 1));
-                        if (! __udp_lib_lport_inuse(result, udptable))
+                        hash = hash_port_and_addr(result,
+                                        inet_sk(sk)->rcv_saddr);
+                        if (! __udp_lib_port_inuse(hash, result,
+                                inet_sk(sk)->rcv_saddr, udptable))
                                 break;
                 }
                 if (i >= (1 << 16) / UDP_HTABLE_SIZE)
@@ -189,11 +214,13 @@ int __udp_lib_get_port(struct sock *sk, unsigned short snum,
 gotit:
                 *port_rover = snum = result;
         } else {
-                head = &udptable[snum & (UDP_HTABLE_SIZE - 1)];
+                hash = hash_port_and_addr(snum, inet_sk(sk)->rcv_saddr);
+                head = &udptable[hash & (UDP_HTABLE_SIZE - 1)];
 
                 sk_for_each(sk2, node, head)
-                        if (sk2->sk_hash == snum                             &&
+                        if (sk2->sk_hash == hash                             &&
                             sk2 != sk                                        &&
+                            inet_sk(sk2)->num == snum                        &&
                             (!sk2->sk_reuse        || !sk->sk_reuse)         &&
                             (!sk2->sk_bound_dev_if || !sk->sk_bound_dev_if
                              || sk2->sk_bound_dev_if == sk->sk_bound_dev_if) &&
@@ -201,9 +228,9 @@ gotit:
                                 goto fail;
         }
         inet_sk(sk)->num = snum;
-        sk->sk_hash = snum;
+        sk->sk_hash = hash;
         if (sk_unhashed(sk)) {
-                head = &udptable[snum & (UDP_HTABLE_SIZE - 1)];
+                head = &udptable[hash & (UDP_HTABLE_SIZE - 1)];
                 sk_add_node(sk, head);
                 sock_prot_inc_use(sk->sk_prot);
         }
@@ -242,63 +269,78 @@ static struct sock *__udp4_lib_lookup(__be32 saddr, __be16 sport,
 {
         struct sock *sk, *result = NULL;
         struct hlist_node *node;
-        unsigned short hnum = ntohs(dport);
-        int badness = -1;
+        unsigned int hash, hashwild;
+        int score, best = -1;
+
+        hash = hash_port_and_addr(ntohs(dport), daddr);
+        hashwild = hash_port_and_addr(ntohs(dport), 0);
 
         read_lock(&udp_hash_lock);
-        sk_for_each(sk, node, &udptable[hnum & (UDP_HTABLE_SIZE - 1)]) {
+
+lookup:
+
+        sk_for_each(sk, node, &udptable[hash & (UDP_HTABLE_SIZE - 1)]) {
                 struct inet_sock *inet = inet_sk(sk);
 
-                if (sk->sk_hash == hnum && !ipv6_only_sock(sk)) {
-                        int score = (sk->sk_family == PF_INET ? 1 : 0);
-                        if (inet->rcv_saddr) {
-                                if (inet->rcv_saddr != daddr)
-                                        continue;
-                                score+=2;
-                        }
-                        if (inet->daddr) {
-                                if (inet->daddr != saddr)
-                                        continue;
-                                score+=2;
-                        }
-                        if (inet->dport) {
-                                if (inet->dport != sport)
-                                        continue;
-                                score+=2;
-                        }
-                        if (sk->sk_bound_dev_if) {
-                                if (sk->sk_bound_dev_if != dif)
-                                        continue;
-                                score+=2;
-                        }
-                        if (score == 9) {
-                                result = sk;
-                                break;
-                        } else if (score > badness) {
-                                result = sk;
-                                badness = score;
-                        }
+                if (sk->sk_hash != hash || ipv6_only_sock(sk) ||
+                        inet->num != dport)
+                        continue;
+
+                score = (sk->sk_family == PF_INET ? 1 : 0);
+                if (inet->rcv_saddr) {
+                        if (inet->rcv_saddr != daddr)
+                                continue;
+                        score+=2;
+                }
+                if (inet->daddr) {
+                        if (inet->daddr != saddr)
+                                continue;
+                        score+=2;
+                }
+                if (inet->dport) {
+                        if (inet->dport != sport)
+                                continue;
+                        score+=2;
+                }
+                if (sk->sk_bound_dev_if) {
+                        if (sk->sk_bound_dev_if != dif)
+                                continue;
+                        score+=2;
+                }
+                if (score == 9) {
+                        result = sk;
+                        goto found;
+                } else if (score > best) {
+                        result = sk;
+                        best = score;
                 }
         }
+
+        if (hash != hashwild) {
+                hash = hashwild;
+                goto lookup;
+        }
+found:
         if (result)
                 sock_hold(result);
         read_unlock(&udp_hash_lock);
         return result;
 }
 
-static inline struct sock *udp_v4_mcast_next(struct sock *sk,
-                                             __be16 loc_port, __be32 loc_addr,
-                                             __be16 rmt_port, __be32 rmt_addr,
-                                             int dif)
+static inline struct sock *udp_v4_mcast_next(
+                        struct sock *sk,
+                        unsigned int hnum, __be16 loc_port, __be32 loc_addr,
+                        __be16 rmt_port, __be32 rmt_addr,
+                        int dif)
 {
         struct hlist_node *node;
         struct sock *s = sk;
-        unsigned short hnum = ntohs(loc_port);
 
         sk_for_each_from(s, node) {
                 struct inet_sock *inet = inet_sk(s);
 
                 if (s->sk_hash != hnum                                  ||
+                    inet->num != loc_port                               ||
                     (inet->daddr && inet->daddr != rmt_addr)            ||
                     (inet->dport != rmt_port && inet->dport)            ||
                     (inet->rcv_saddr && inet->rcv_saddr != loc_addr)    ||
@@ -1129,29 +1171,44 @@ static int __udp4_lib_mcast_deliver(struct sk_buff *skb,
                                     __be32 saddr, __be32 daddr,
                                     struct hlist_head udptable[])
 {
-        struct sock *sk;
+        struct sock *sk, *skw, *sknext;
         int dif;
+        unsigned int hash = hash_port_and_addr(ntohs(uh->dest), daddr);
+        unsigned int hashwild = hash_port_and_addr(ntohs(uh->dest), 0);
 
-        read_lock(&udp_hash_lock);
-        sk = sk_head(&udptable[ntohs(uh->dest) & (UDP_HTABLE_SIZE - 1)]);
         dif = skb->dev->ifindex;
-        sk = udp_v4_mcast_next(sk, uh->dest, daddr, uh->source, saddr, dif);
-        if (sk) {
-                struct sock *sknext = NULL;
 
+        read_lock(&udp_hash_lock);
+
+        sk = sk_head(&udptable[hash & (UDP_HTABLE_SIZE - 1)]);
+        skw = sk_head(&udptable[hashwild & (UDP_HTABLE_SIZE - 1)]);
+
+        sk = udp_v4_mcast_next(sk, hash, uh->dest, daddr, uh->source, saddr, dif);
+        if (!sk) {
+                hash = hashwild;
+                sk = udp_v4_mcast_next(skw, hash, uh->dest, daddr, uh->source,
+                        saddr, dif);
+        }
+        if (sk) {
                 do {
                         struct sk_buff *skb1 = skb;
-
-                        sknext = udp_v4_mcast_next(sk_next(sk), uh->dest, daddr,
-                                                   uh->source, saddr, dif);
+                        sknext = udp_v4_mcast_next(sk_next(sk), hash, uh->dest,
+                                daddr, uh->source, saddr, dif);
+                        if (!sknext && hash != hashwild) {
+                                hash = hashwild;
+                                sknext = udp_v4_mcast_next(skw, hash, uh->dest,
+                                        daddr, uh->source, saddr, dif);
+                        }
                         if (sknext)
                                 skb1 = skb_clone(skb, GFP_ATOMIC);
 
                         if (skb1) {
                                 int ret = udp_queue_rcv_skb(sk, skb1);
                                 if (ret > 0)
-                                        /* we should probably re-process instead
-                                         * of dropping packets here. */
+                                        /*
+                                         * we should probably re-process
+                                         * instead of dropping packets here.
+                                         */
                                         kfree_skb(skb1);
                         }
                         sk = sknext;