[PATCH] tcp: Cache inetpeer in timewait socket, and only when necessary.

Since it's guarenteed that we will access the inetpeer if we're trying
to do timewait recycling and TCP options were enabled on the
connection, just cache the peer in the timewait socket.

In the future, inetpeer lookups will be context dependent (per routing
realm), and this helps facilitate that as well.

Signed-off-by: David S. Miller <[e-mail]>

include/linux/tcp.h

···
 	u32			  tw_rcv_wnd;
 	u32			  tw_ts_recent;
 	long			  tw_ts_recent_stamp;
+	struct inet_peer	  *tw_peer;
 #ifdef CONFIG_TCP_MD5SIG
-	struct tcp_md5sig_key	*tw_md5_key;
+	struct tcp_md5sig_key	  *tw_md5_key;
 #endif
 	/* Few sockets in timewait have cookies; in that case, then this
 	 * object holds a reference to them (tw_cookie_values->kref).

include/net/tcp.h

···
 extern int tcp_v4_rcv(struct sk_buff *skb);
 
 extern struct inet_peer *tcp_v4_get_peer(struct sock *sk);
-extern void *tcp_v4_tw_get_peer(struct sock *sk);
 extern int tcp_v4_tw_remember_stamp(struct inet_timewait_sock *tw);
 extern int tcp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 		       size_t size);

include/net/timewait_sock.h

···
 	int		(*twsk_unique)(struct sock *sk,
 				       struct sock *sktw, void *twp);
 	void		(*twsk_destructor)(struct sock *sk);
-	void		*(*twsk_getpeer)(struct sock *sk);
 };
 
 static inline int twsk_unique(struct sock *sk, struct sock *sktw, void *twp)
···
 	BUG_ON(sk->sk_prot->twsk_prot == NULL);
 	if (sk->sk_prot->twsk_prot->twsk_destructor != NULL)
 		sk->sk_prot->twsk_prot->twsk_destructor(sk);
-}
-
-static inline void *twsk_getpeer(struct sock *sk)
-{
-	if (sk->sk_prot->twsk_prot->twsk_getpeer)
-		return sk->sk_prot->twsk_prot->twsk_getpeer(sk);
-	return NULL;
 }
 
 #endif /* _TIMEWAIT_SOCK_H */

net/ipv4/tcp_ipv4.c

···
 }
 EXPORT_SYMBOL(tcp_v4_get_peer);
 
-void *tcp_v4_tw_get_peer(struct sock *sk)
-{
-	const struct inet_timewait_sock *tw = inet_twsk(sk);
-	struct net *net = sock_net(sk);
-
-	return inet_getpeer_v4(net, tw->tw_daddr, 1);
-}
-EXPORT_SYMBOL(tcp_v4_tw_get_peer);
-
 static struct timewait_sock_ops tcp_timewait_sock_ops = {
 	.twsk_obj_size	= sizeof(struct tcp_timewait_sock),
 	.twsk_unique	= tcp_twsk_unique,
 	.twsk_destructor= tcp_twsk_destructor,
-	.twsk_getpeer	= tcp_v4_tw_get_peer,
 };
 
 const struct inet_connection_sock_af_ops ipv4_specific = {

net/ipv4/tcp_minisocks.c

···
 
 static bool tcp_tw_remember_stamp(struct inet_timewait_sock *tw)
 {
+	const struct tcp_timewait_sock *tcptw;
 	struct sock *sk = (struct sock *) tw;
 	struct inet_peer *peer;
 
-	peer = twsk_getpeer(sk);
+	tcptw = tcp_twsk(sk);
+	peer = tcptw->tw_peer;
 	if (peer) {
-		const struct tcp_timewait_sock *tcptw = tcp_twsk(sk);
-
 		if ((s32)(peer->tcp_ts - tcptw->tw_ts_recent) <= 0 ||
 		    ((u32)get_seconds() - peer->tcp_ts_stamp > TCP_PAWS_MSL &&
 		     peer->tcp_ts_stamp <= (u32)tcptw->tw_ts_recent_stamp)) {
 			peer->tcp_ts_stamp = (u32)tcptw->tw_ts_recent_stamp;
 			peer->tcp_ts	   = tcptw->tw_ts_recent;
 		}
-		inet_putpeer(peer);
 		return true;
 	}
 	return false;
···
 	const struct inet_connection_sock *icsk = inet_csk(sk);
 	const struct tcp_sock *tp = tcp_sk(sk);
 	bool recycle_ok = false;
+	bool recycle_on = false;
 
-	if (tcp_death_row.sysctl_tw_recycle && tp->rx_opt.ts_recent_stamp)
+	if (tcp_death_row.sysctl_tw_recycle && tp->rx_opt.ts_recent_stamp) {
 		recycle_ok = tcp_remember_stamp(sk);
+		recycle_on = true;
+	}
 
 	if (tcp_death_row.tw_count < tcp_death_row.sysctl_max_tw_buckets)
 		tw = inet_twsk_alloc(sk, state);
···
 	if (tw != NULL) {
 		struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw);
 		const int rto = (icsk->icsk_rto << 2) - (icsk->icsk_rto >> 1);
+		struct inet_sock *inet = inet_sk(sk);
+		struct inet_peer *peer = NULL;
 
-		tw->tw_transparent	= inet_sk(sk)->transparent;
+		tw->tw_transparent	= inet->transparent;
 		tw->tw_rcv_wscale	= tp->rx_opt.rcv_wscale;
 		tcptw->tw_rcv_nxt	= tp->rcv_nxt;
 		tcptw->tw_snd_nxt	= tp->snd_nxt;
···
 			tw->tw_ipv6only = np->ipv6only;
 		}
 #endif
+
+		if (recycle_on)
+			peer = icsk->icsk_af_ops->get_peer(sk);
+		tcptw->tw_peer = peer;
+		if (peer)
+			atomic_inc(&peer->refcnt);
 
 #ifdef CONFIG_TCP_MD5SIG
 		/*
···
 
 void tcp_twsk_destructor(struct sock *sk)
 {
-#ifdef CONFIG_TCP_MD5SIG
 	struct tcp_timewait_sock *twsk = tcp_twsk(sk);
+
+	if (twsk->tw_peer)
+		inet_putpeer(twsk->tw_peer);
+#ifdef CONFIG_TCP_MD5SIG
 	if (twsk->tw_md5_key) {
 		tcp_free_md5sig_pool();
 		kfree_rcu(twsk->tw_md5_key, rcu);

net/ipv6/tcp_ipv6.c

···
 	return rt6_get_peer_create(rt);
 }
 
-static void *tcp_v6_tw_get_peer(struct sock *sk)
-{
-	const struct inet6_timewait_sock *tw6 = inet6_twsk(sk);
-	const struct inet_timewait_sock *tw = inet_twsk(sk);
-	struct net *net = sock_net(sk);
-
-	if (tw->tw_family == AF_INET)
-		return tcp_v4_tw_get_peer(sk);
-
-	return inet_getpeer_v6(net, &tw6->tw_v6_daddr, 1);
-}
-
 static struct timewait_sock_ops tcp6_timewait_sock_ops = {
 	.twsk_obj_size	= sizeof(struct tcp6_timewait_sock),
 	.twsk_unique	= tcp_twsk_unique,
 	.twsk_destructor= tcp_twsk_destructor,
-	.twsk_getpeer	= tcp_v6_tw_get_peer,
 };
 
 static const struct inet_connection_sock_af_ops ipv6_specific = {