netdev - [PATCH net-next 2/2] tcp: propagate GSO to the new skb built in tcp collapse

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Date:   Sat, 28 Jul 2018 11:01:40 +0800
From:   Yafang Shao <laoar.shao@...il.com>
To:     edumazet@...gle.com, davem@...emloft.net
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Yafang Shao <laoar.shao@...il.com>
Subject: [PATCH net-next 2/2] tcp: propagate GSO to the new skb built in tcp collapse

Currently the collapsed SKB doesn't propagate the GSO information to the
new SKB.
The GSO should be propagated for better tracking, i.e. when this SKB is
dropped we could know how many network segments are dropped.

Signed-off-by: Yafang Shao <laoar.shao@...il.com>
---
 net/ipv4/tcp_input.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 90f83eb..af52e4e 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4893,6 +4893,8 @@ void tcp_rbtree_insert(struct rb_root *root, struct sk_buff *skb)
 		if (!nskb)
 			break;
 
+		skb_shinfo(nskb)->gso_size = skb_shinfo(skb)->gso_size;
+		skb_shinfo(nskb)->gso_type = skb_shinfo(skb)->gso_type;
 		memcpy(nskb->cb, skb->cb, sizeof(skb->cb));
 #ifdef CONFIG_TLS_DEVICE
 		nskb->decrypted = skb->decrypted;
@@ -4906,18 +4908,24 @@ void tcp_rbtree_insert(struct rb_root *root, struct sk_buff *skb)
 
 		/* Copy data, releasing collapsed skbs. */
 		while (copy > 0) {
-			int offset = start - TCP_SKB_CB(skb)->seq;
 			int size = TCP_SKB_CB(skb)->end_seq - start;
+			int offset = start - TCP_SKB_CB(skb)->seq;
 
 			BUG_ON(offset < 0);
 			if (size > 0) {
-				size = min(copy, size);
+				if (copy >= size)
+					skb_shinfo(nskb)->gso_segs +=
+						max_t(u16, 1, skb_shinfo(skb)->gso_segs);
+				else
+					size = copy;
+
 				if (skb_copy_bits(skb, offset, skb_put(nskb, size), size))
 					BUG();
 				TCP_SKB_CB(nskb)->end_seq += size;
 				copy -= size;
 				start += size;
 			}
+
 			if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
 				skb = tcp_collapse_one(sk, skb, list, root);
 				if (!skb ||
-- 
1.8.3.1