[PATCH net-next 1/2] tcp: remove redundant rcv_nxt update

[PATCH net-next 1/2] tcp: remove redundant rcv_nxt update

[Yafang Shao]

tcp_rcv_nxt_update() is already executed in tcp_data_queue().
This line is redundant.

See bellow,
	tcp_queue_rcv
		tcp_rcv_nxt_update(tcp_sk(sk), TCP_SKB_CB(skb)->end_seq);
	tcp_rcv_nxt_update(tp, TCP_SKB_CB(skb)->end_seq); <<<< redundant

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
 net/ipv4/tcp_input.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 814ea43..3a54faf 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4695,7 +4695,6 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
 		}
 
 		eaten = tcp_queue_rcv(sk, skb, 0, &fragstolen);
-		tcp_rcv_nxt_update(tp, TCP_SKB_CB(skb)->end_seq);
 		if (skb->len)
 			tcp_event_data_recv(sk, skb);
 		if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
-- 
1.8.3.1

[PATCH net-next 2/2] tcp: refactor tcp_queue_rcv

[Yafang Shao]

There're are some code similar to tcp_queue_rcv() in tcp_ofo_queue(),
so refactor tcp_queue_rcv() to make it be used in tcp_ofo_queue().

After this change, skb->sk is set when skb is moved from ofo queue into
receive queue instead of when queued into ofo queue.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
 net/ipv4/tcp_input.c | 52 ++++++++++++++++++++++------------------------------
 1 file changed, 22 insertions(+), 30 deletions(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 3a54faf..92d4499 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4367,6 +4367,21 @@ static void tcp_drop(struct sock *sk, struct sk_buff *skb)
 	__kfree_skb(skb);
 }
 
+static int __must_check
+tcp_queue_rcv(struct sock *sk, struct sk_buff *skb, bool *fragstolen)
+{
+	int eaten;
+	struct sk_buff *tail = skb_peek_tail(&sk->sk_receive_queue);
+
+	eaten = tail && tcp_try_coalesce(sk, tail, skb, fragstolen);
+	tcp_rcv_nxt_update(tcp_sk(sk), TCP_SKB_CB(skb)->end_seq);
+	if (!eaten) {
+		__skb_queue_tail(&sk->sk_receive_queue, skb);
+		skb_set_owner_r(skb, sk);
+	}
+	return eaten;
+}
+
 /* This one checks to see if we can put data from the
  * out_of_order queue into the receive_queue.
  */
@@ -4375,7 +4390,7 @@ static void tcp_ofo_queue(struct sock *sk)
 	struct tcp_sock *tp = tcp_sk(sk);
 	__u32 dsack_high = tp->rcv_nxt;
 	bool fin, fragstolen, eaten;
-	struct sk_buff *skb, *tail;
+	struct sk_buff *skb;
 	struct rb_node *p;
 
 	p = rb_first(&tp->out_of_order_queue);
@@ -4402,13 +4417,9 @@ static void tcp_ofo_queue(struct sock *sk)
 			   tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
 			   TCP_SKB_CB(skb)->end_seq);
 
-		tail = skb_peek_tail(&sk->sk_receive_queue);
-		eaten = tail && tcp_try_coalesce(sk, tail, skb, &fragstolen);
-		tcp_rcv_nxt_update(tp, TCP_SKB_CB(skb)->end_seq);
+		eaten = tcp_queue_rcv(sk, skb, &fragstolen);
 		fin = TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN;
-		if (!eaten)
-			__skb_queue_tail(&sk->sk_receive_queue, skb);
-		else
+		if (eaten)
 			kfree_skb_partial(skb, fragstolen);
 
 		if (unlikely(fin)) {
@@ -4573,28 +4584,9 @@ static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb)
 	if (skb) {
 		tcp_grow_window(sk, skb);
 		skb_condense(skb);
-		skb_set_owner_r(skb, sk);
 	}
 }
 
-static int __must_check tcp_queue_rcv(struct sock *sk, struct sk_buff *skb, int hdrlen,
-		  bool *fragstolen)
-{
-	int eaten;
-	struct sk_buff *tail = skb_peek_tail(&sk->sk_receive_queue);
-
-	__skb_pull(skb, hdrlen);
-	eaten = (tail &&
-		 tcp_try_coalesce(sk, tail,
-				  skb, fragstolen)) ? 1 : 0;
-	tcp_rcv_nxt_update(tcp_sk(sk), TCP_SKB_CB(skb)->end_seq);
-	if (!eaten) {
-		__skb_queue_tail(&sk->sk_receive_queue, skb);
-		skb_set_owner_r(skb, sk);
-	}
-	return eaten;
-}
-
 int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size)
 {
 	struct sk_buff *skb;
@@ -4634,7 +4626,7 @@ int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size)
 	TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq + size;
 	TCP_SKB_CB(skb)->ack_seq = tcp_sk(sk)->snd_una - 1;
 
-	if (tcp_queue_rcv(sk, skb, 0, &fragstolen)) {
+	if (tcp_queue_rcv(sk, skb, &fragstolen)) {
 		WARN_ON_ONCE(fragstolen); /* should not happen */
 		__kfree_skb(skb);
 	}
@@ -4694,7 +4686,7 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
 			goto drop;
 		}
 
-		eaten = tcp_queue_rcv(sk, skb, 0, &fragstolen);
+		eaten = tcp_queue_rcv(sk, skb, &fragstolen);
 		if (skb->len)
 			tcp_event_data_recv(sk, skb);
 		if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
@@ -5529,8 +5521,8 @@ void tcp_rcv_established(struct sock *sk, struct sk_buff *skb)
 			NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPHPHITS);
 
 			/* Bulk data transfer: receiver */
-			eaten = tcp_queue_rcv(sk, skb, tcp_header_len,
-					      &fragstolen);
+			__skb_pull(skb, tcp_header_len);
+			eaten = tcp_queue_rcv(sk, skb, &fragstolen);
 
 			tcp_event_data_recv(sk, skb);
 
-- 
1.8.3.1

Re: [PATCH net-next 2/2] tcp: refactor tcp_queue_rcv

[Eric Dumazet]

Hi Yafang
On Wed, Jul 11, 2018 at 6:17 AM Yafang Shao <laoar.shao@gmail.com> wrote:
>
> There're are some code similar to tcp_queue_rcv() in tcp_ofo_queue(),
> so refactor tcp_queue_rcv() to make it be used in tcp_ofo_queue().
>
> After this change, skb->sk is set when skb is moved from ofo queue into
> receive queue instead of when queued into ofo queue.

Why would you do that ???

I urge you to test this on hosts connected to the wild Internet :/

Re: [PATCH net-next 1/2] tcp: remove redundant rcv_nxt update

[Eric Dumazet]

On 07/11/2018 06:16 AM, Yafang Shao wrote:
> tcp_rcv_nxt_update() is already executed in tcp_data_queue().
> This line is redundant.
> 
> See bellow,
> 	tcp_queue_rcv
> 		tcp_rcv_nxt_update(tcp_sk(sk), TCP_SKB_CB(skb)->end_seq);
> 	tcp_rcv_nxt_update(tp, TCP_SKB_CB(skb)->end_seq); <<<< redundant
> 
> Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
> ---

This patch is fine (but not the following)

Signed-off-by: Eric Dumazet <edumazet@google.com>

Thanks.