Merge branch 'tcp-listener-fixes-and-improvement'

Eric Dumazet says:

====================
tcp: lockless listener fixes and improvement

This fixes issues with TCP FastOpen vs lockless listeners,
and SYNACK being attached to request sockets.

Then, last patch brings performance improvement for
syncookies generation and validation.

Tested under a 4.3 Mpps SYNFLOOD attack, new perf profile looks
like :
    12.11%  [kernel]  [k] sha_transform
     5.83%  [kernel]  [k] tcp_conn_request
     4.59%  [kernel]  [k] __inet_lookup_listener
     4.11%  [kernel]  [k] ipt_do_table
     3.91%  [kernel]  [k] tcp_make_synack
     3.05%  [kernel]  [k] fib_table_lookup
     2.74%  [kernel]  [k] sock_wfree
     2.66%  [kernel]  [k] memcpy_erms
     2.12%  [kernel]  [k] tcp_v4_rcv
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

11 files changed, 41 insertions, 36 deletions

diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index f1f32af..0ef2a97 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -264,9 +264,9 @@ struct tcp6_timewait_sock {
 };
 
 #if IS_ENABLED(CONFIG_IPV6)
-static inline struct ipv6_pinfo * inet6_sk(const struct sock *__sk)
+static inline struct ipv6_pinfo *inet6_sk(const struct sock *__sk)
 {
-	return inet_sk(__sk)->pinet6;
+	return sk_fullsock(__sk) ? inet_sk(__sk)->pinet6 : NULL;
 }
 
 static inline struct raw6_sock *raw6_sk(const struct sock *sk)
diff --git a/include/net/inet_sock.h b/include/net/inet_sock.h
index 47eb67b..f5bf731 100644
--- a/include/net/inet_sock.h
+++ b/include/net/inet_sock.h
@@ -245,7 +245,8 @@ static inline unsigned int __inet_ehashfn(const __be32 laddr,
 }
 
 struct request_sock *inet_reqsk_alloc(const struct request_sock_ops *ops,
-				      struct sock *sk_listener);
+				      struct sock *sk_listener,
+				      bool attach_listener);
 
 static inline __u8 inet_sk_flowi_flags(const struct sock *sk)
 {
diff --git a/include/net/ip.h b/include/net/ip.h
index 91a6b2c..aa78119 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -323,12 +323,15 @@ static inline unsigned int ip_dst_mtu_maybe_forward(const struct dst_entry *dst,
 
 static inline unsigned int ip_skb_dst_mtu(const struct sk_buff *skb)
 {
-	if (!skb->sk || ip_sk_use_pmtu(skb->sk)) {
+	struct sock *sk = skb->sk;
+
+	if (!sk || !sk_fullsock(sk) || ip_sk_use_pmtu(sk)) {
 		bool forwarding = IPCB(skb)->flags & IPSKB_FORWARDED;
+
 		return ip_dst_mtu_maybe_forward(skb_dst(skb), forwarding);
-	} else {
-		return min(skb_dst(skb)->dev->mtu, IP_MAX_MTU);
 	}
+
+	return min(skb_dst(skb)->dev->mtu, IP_MAX_MTU);
 }
 
 u32 ip_idents_reserve(u32 hash, int segs);
diff --git a/include/net/request_sock.h b/include/net/request_sock.h
index dd423d8..95ab5d7 100644
--- a/include/net/request_sock.h
+++ b/include/net/request_sock.h
@@ -80,7 +80,8 @@ static inline struct sock *req_to_sk(struct request_sock *req)
 }
 
 static inline struct request_sock *
-reqsk_alloc(const struct request_sock_ops *ops, struct sock *sk_listener)
+reqsk_alloc(const struct request_sock_ops *ops, struct sock *sk_listener,
+	    bool attach_listener)
 {
 	struct request_sock *req;
 
@@ -88,10 +89,15 @@ reqsk_alloc(const struct request_sock_ops *ops, struct sock *sk_listener)
 
 	if (req) {
 		req->rsk_ops = ops;
-		sock_hold(sk_listener);
-		req->rsk_listener = sk_listener;
+		if (attach_listener) {
+			sock_hold(sk_listener);
+			req->rsk_listener = sk_listener;
+		} else {
+			req->rsk_listener = NULL;
+		}
 		req_to_sk(req)->sk_prot = sk_listener->sk_prot;
 		sk_node_init(&req_to_sk(req)->sk_node);
+		sk_tx_queue_clear(req_to_sk(req));
 		req->saved_syn = NULL;
 		/* Following is temporary. It is coupled with debugging
 		 * helpers in reqsk_put() & reqsk_free()
diff --git a/net/core/dev.c b/net/core/dev.c
index 323c04e..a229bf0 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2974,6 +2974,7 @@ static u16 __netdev_pick_tx(struct net_device *dev, struct sk_buff *skb)
 			new_index = skb_tx_hash(dev, skb);
 
 		if (queue_index != new_index && sk &&
+		    sk_fullsock(sk) &&
 		    rcu_access_pointer(sk->sk_dst_cache))
 			sk_tx_queue_set(sk, new_index);
 
diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index 8910c95..8e99681 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -595,7 +595,7 @@ int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
 	if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1)
 		goto drop;
 
-	req = inet_reqsk_alloc(&dccp_request_sock_ops, sk);
+	req = inet_reqsk_alloc(&dccp_request_sock_ops, sk, true);
 	if (req == NULL)
 		goto drop;
 
diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c
index 1361a3f..aed314f 100644
--- a/net/dccp/ipv6.c
+++ b/net/dccp/ipv6.c
@@ -319,7 +319,7 @@ static int dccp_v6_conn_request(struct sock *sk, struct sk_buff *skb)
 	if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1)
 		goto drop;
 
-	req = inet_reqsk_alloc(&dccp6_request_sock_ops, sk);
+	req = inet_reqsk_alloc(&dccp6_request_sock_ops, sk, true);
 	if (req == NULL)
 		goto drop;
 
diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index 729ceb5..8113c30 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -326,7 +326,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 		goto out;
 
 	ret = NULL;
-	req = inet_reqsk_alloc(&tcp_request_sock_ops, sk); /* for safety */
+	req = inet_reqsk_alloc(&tcp_request_sock_ops, sk, false); /* for safety */
 	if (!req)
 		goto out;
 
diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c
index 410ac48..93396bf 100644
--- a/net/ipv4/tcp_fastopen.c
+++ b/net/ipv4/tcp_fastopen.c
@@ -168,8 +168,6 @@ static struct sock *tcp_fastopen_create_child(struct sock *sk,
 				  TCP_TIMEOUT_INIT, TCP_RTO_MAX);
 
 	atomic_set(&req->rsk_refcnt, 2);
-	/* Add the child socket directly into the accept queue */
-	inet_csk_reqsk_queue_add(sk, req, child);
 
 	/* Now finish processing the fastopen child socket. */
 	inet_csk(child)->icsk_af_ops->rebuild_header(child);
@@ -178,12 +176,10 @@ static struct sock *tcp_fastopen_create_child(struct sock *sk,
 	tcp_init_metrics(child);
 	tcp_init_buffer_space(child);
 
-	/* Queue the data carried in the SYN packet. We need to first
-	 * bump skb's refcnt because the caller will attempt to free it.
-	 * Note that IPv6 might also have used skb_get() trick
-	 * in tcp_v6_conn_request() to keep this SYN around (treq->pktopts)
-	 * So we need to eventually get a clone of the packet,
-	 * before inserting it in sk_receive_queue.
+	/* Queue the data carried in the SYN packet.
+	 * We used to play tricky games with skb_get().
+	 * With lockless listener, it is a dead end.
+	 * Do not think about it.
 	 *
 	 * XXX (TFO) - we honor a zero-payload TFO request for now,
 	 * (any reason not to?) but no need to queue the skb since
@@ -191,12 +187,7 @@ static struct sock *tcp_fastopen_create_child(struct sock *sk,
 	 */
 	end_seq = TCP_SKB_CB(skb)->end_seq;
 	if (end_seq != TCP_SKB_CB(skb)->seq + 1) {
-		struct sk_buff *skb2;
-
-		if (unlikely(skb_shared(skb)))
-			skb2 = skb_clone(skb, GFP_ATOMIC);
-		else
-			skb2 = skb_get(skb);
+		struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC);
 
 		if (likely(skb2)) {
 			skb_dst_drop(skb2);
@@ -214,12 +205,9 @@ static struct sock *tcp_fastopen_create_child(struct sock *sk,
 		}
 	}
 	tcp_rsk(req)->rcv_nxt = tp->rcv_nxt = end_seq;
-	sk->sk_data_ready(sk);
-	bh_unlock_sock(child);
-	/* Note: sock_put(child) will be done by tcp_conn_request()
-	 * after SYNACK packet is sent.
+	/* tcp_conn_request() is sending the SYNACK,
+	 * and queues the child into listener accept queue.
 	 */
-	WARN_ON(!req->sk);
 	return child;
 }
 
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 2710875..ddadb31 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -6042,9 +6042,11 @@ static void tcp_openreq_init(struct request_sock *req,
 }
 
 struct request_sock *inet_reqsk_alloc(const struct request_sock_ops *ops,
-				      struct sock *sk_listener)
+				      struct sock *sk_listener,
+				      bool attach_listener)
 {
-	struct request_sock *req = reqsk_alloc(ops, sk_listener);
+	struct request_sock *req = reqsk_alloc(ops, sk_listener,
+					       attach_listener);
 
 	if (req) {
 		struct inet_request_sock *ireq = inet_rsk(req);
@@ -6143,7 +6145,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
 		goto drop;
 	}
 
-	req = inet_reqsk_alloc(rsk_ops, sk);
+	req = inet_reqsk_alloc(rsk_ops, sk, !want_cookie);
 	if (!req)
 		goto drop;
 
@@ -6229,12 +6231,16 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
 	tcp_rsk(req)->txhash = net_tx_rndhash();
 	tcp_openreq_init_rwin(req, sk, dst);
 	if (!want_cookie) {
-		fastopen_sk = tcp_try_fastopen(sk, skb, req, &foc, dst);
 		tcp_reqsk_record_syn(sk, req, skb);
+		fastopen_sk = tcp_try_fastopen(sk, skb, req, &foc, dst);
 	}
 	if (fastopen_sk) {
 		af_ops->send_synack(fastopen_sk, dst, &fl, req,
 				    skb_get_queue_mapping(skb), &foc, false);
+		/* Add the child socket directly into the accept queue */
+		inet_csk_reqsk_queue_add(sk, req, fastopen_sk);
+		sk->sk_data_ready(sk);
+		bh_unlock_sock(fastopen_sk);
 		sock_put(fastopen_sk);
 	} else {
 		tcp_rsk(req)->tfo_listener = false;
diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index 7606eba..f610b53 100644
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -170,7 +170,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 		goto out;
 
 	ret = NULL;
-	req = inet_reqsk_alloc(&tcp6_request_sock_ops, sk);
+	req = inet_reqsk_alloc(&tcp6_request_sock_ops, sk, false);
 	if (!req)
 		goto out;