tcp: bind() use stronger condition for bind_conflict

We must try harder to get unique (addr, port) pairs when
doing port autoselection for sockets with SO_REUSEADDR
option set.

We achieve this by adding a relaxation parameter to
inet_csk_bind_conflict. When 'relax' parameter is off
we return a conflict whenever the current searched
pair (addr, port) is not unique.

This tries to address the problems reported in patch:
	8d238b25b1ec22a73b1c2206f111df2faaff8285
	Revert "tcp: bind() fix when many ports are bound"

Tests where ran for creating and binding(0) many sockets
on 100 IPs. The results are, on average:

	* 60000 sockets, 600 ports / IP:
		* 0.210 s, 620 (IP, port) duplicates without patch
		* 0.219 s, no duplicates with patch
	* 100000 sockets, 1000 ports / IP:
		* 0.371 s, 1720 duplicates without patch
		* 0.373 s, no duplicates with patch
	* 200000 sockets, 2000 ports / IP:
		* 0.766 s, 6900 duplicates without patch
		* 0.768 s, no duplicates with patch
	* 500000 sockets, 5000 ports / IP:
		* 2.227 s, 41500 duplicates without patch
		* 2.284 s, no duplicates with patch

Signed-off-by: Alex Copot <alex.mihai.c@gmail.com>
Signed-off-by: Daniel Baluta <dbaluta@ixiacom.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 18 insertions, 8 deletions

diff --git a/include/net/inet6_connection_sock.h b/include/net/inet6_connection_sock.h
index 3207e58ee019..1866a676c810 100644
--- a/include/net/inet6_connection_sock.h
+++ b/include/net/inet6_connection_sock.h
@@ -23,7 +23,7 @@ struct sock;
 struct sockaddr;
 
 extern int inet6_csk_bind_conflict(const struct sock *sk,
-                                   const struct inet_bind_bucket *tb);
+                                   const struct inet_bind_bucket *tb, bool relax);
 
 extern struct dst_entry* inet6_csk_route_req(struct sock *sk,
                                              const struct request_sock *req);
diff --git a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h
index dbf9aab34c82..46c9e2ccdf02 100644
--- a/include/net/inet_connection_sock.h
+++ b/include/net/inet_connection_sock.h
@@ -60,7 +60,7 @@ struct inet_connection_sock_af_ops {
 #endif
         void        (*addr2sockaddr)(struct sock *sk, struct sockaddr *);
         int         (*bind_conflict)(const struct sock *sk,
-                                     const struct inet_bind_bucket *tb);
+                                     const struct inet_bind_bucket *tb, bool relax);
 };
 
 /** inet_connection_sock - INET connection oriented sock
@@ -245,7 +245,7 @@ extern struct request_sock *inet_csk_search_req(const struct sock *sk,
                                                 const __be32 raddr,
                                                 const __be32 laddr);
 extern int inet_csk_bind_conflict(const struct sock *sk,
-                                  const struct inet_bind_bucket *tb);
+                                  const struct inet_bind_bucket *tb, bool relax);
 extern int inet_csk_get_port(struct sock *sk, unsigned short snum);
 
 extern struct dst_entry* inet_csk_route_req(struct sock *sk,
diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index d19f32aca6ca..14409f111bc2 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -53,7 +53,7 @@ void inet_get_local_port_range(int *low, int *high)
 EXPORT_SYMBOL(inet_get_local_port_range);
 
 int inet_csk_bind_conflict(const struct sock *sk,
-                           const struct inet_bind_bucket *tb)
+                           const struct inet_bind_bucket *tb, bool relax)
 {
         struct sock *sk2;
         struct hlist_node *node;
@@ -79,6 +79,14 @@ int inet_csk_bind_conflict(const struct sock *sk,
                                     sk2_rcv_saddr == sk_rcv_saddr(sk))
                                         break;
                         }
+                        if (!relax && reuse && sk2->sk_reuse &&
+                            sk2->sk_state != TCP_LISTEN) {
+                                const __be32 sk2_rcv_saddr = sk_rcv_saddr(sk2);
+
+                                if (!sk2_rcv_saddr || !sk_rcv_saddr(sk) ||
+                                    sk2_rcv_saddr == sk_rcv_saddr(sk))
+                                        break;
+                        }
                 }
         }
         return node != NULL;
@@ -122,12 +130,13 @@ again:
                                             (tb->num_owners < smallest_size || smallest_size == -1)) {
                                                 smallest_size = tb->num_owners;
                                                 smallest_rover = rover;
-                                                if (atomic_read(&hashinfo->bsockets) > (high - low) + 1) {
+                                                if (atomic_read(&hashinfo->bsockets) > (high - low) + 1 &&
+                                                    !inet_csk(sk)->icsk_af_ops->bind_conflict(sk, tb, false)) {
                                                         snum = smallest_rover;
                                                         goto tb_found;
                                                 }
                                         }
-                                        if (!inet_csk(sk)->icsk_af_ops->bind_conflict(sk, tb)) {
+                                        if (!inet_csk(sk)->icsk_af_ops->bind_conflict(sk, tb, false)) {
                                                 snum = rover;
                                                 goto tb_found;
                                         }
@@ -178,12 +187,13 @@ tb_found:
                         goto success;
                 } else {
                         ret = 1;
-                        if (inet_csk(sk)->icsk_af_ops->bind_conflict(sk, tb)) {
+                        if (inet_csk(sk)->icsk_af_ops->bind_conflict(sk, tb, true)) {
                                 if (sk->sk_reuse && sk->sk_state != TCP_LISTEN &&
                                     smallest_size != -1 && --attempts >= 0) {
                                         spin_unlock(&head->lock);
                                         goto again;
                                 }
+
                                 goto fail_unlock;
                         }
                 }
diff --git a/net/ipv6/inet6_connection_sock.c b/net/ipv6/inet6_connection_sock.c
index 02dd203d9eac..e6cee5292a0b 100644
--- a/net/ipv6/inet6_connection_sock.c
+++ b/net/ipv6/inet6_connection_sock.c
@@ -28,7 +28,7 @@
 #include <net/inet6_connection_sock.h>
 
 int inet6_csk_bind_conflict(const struct sock *sk,
-                            const struct inet_bind_bucket *tb)
+                            const struct inet_bind_bucket *tb, bool relax)
 {
         const struct sock *sk2;
         const struct hlist_node *node;