PATCH_net_1a.patch

From cd4ffa93f16efea290bb70537f98f518e1927e63 Mon Sep 17 00:00:00 2001
From: Joao Martins <joao.m.martins@oracle.com>
Date: Mon, 10 Jun 2019 23:12:39 +0100
Subject: [PATCH 5/5] tcp: fix fack_count accounting on tcp_shift_skb_data()

v4.15 or since commit 737ff314563 ("tcp: use sequence distance to
detect reordering") had switched from the packet-based FACK tracking
to sequence-based.

v4.14 and older still have the old logic and hence on
tcp_skb_shift_data() needs to retain its original logic and have
@fack_count in sync. In other words, we keep the increment of pcount with
tcp_skb_pcount(skb) to later used that to update fack_count. To make it
more explicit we track the new skb that gets incremented to pcount in
@next_pcount, and we get to avoid the constant invocation of
tcp_skb_pcount(skb) all together.

Fixes: a5f1faa40101 ("tcp: limit payload size of sacked skbs")
Reported-by: Alexey Kodanev <alexey.kodanev@oracle.com>
Reviewed-by: Jack Vogel <jack.vogel@oracle.com>
Reviewed-by: John Haxby <john.haxby@oracle.com>
Reviewed-by: Rao Shoaib rao.shoaib@oracle.com>
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
 net/ipv4/tcp_input.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index fd5c2d2a1d9c..85c09829790b 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1423,6 +1423,7 @@ static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb,
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct sk_buff *prev;
 	int mss;
+	int next_pcount;
 	int pcount = 0;
 	int len;
 	int in_sack;
@@ -1539,9 +1540,11 @@ static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb,
 		goto out;
 
 	len = skb->len;
-	pcount = tcp_skb_pcount(skb);
-	if (tcp_skb_shift(prev, skb, pcount, len))
-		tcp_shifted_skb(sk, skb, state, pcount, len, mss, 0);
+	next_pcount = tcp_skb_pcount(skb);
+	if (tcp_skb_shift(prev, skb, next_pcount, len)) {
+		pcount += next_pcount;
+		tcp_shifted_skb(sk, skb, state, next_pcount, len, mss, 0);
+	}
 out:
 	state->fack_count += pcount;
 	return prev;
-- 
2.21.0