netdev - [PATCH] tcp: make retransmitted SKB fit into the send window

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Date:   Thu,  7 Jul 2022 18:19:15 +0800
From:   Yonglong Li <liyonglong@...natelecom.cn>
To:     netdev@...r.kernel.org
Cc:     davem@...emloft.net, dsahern@...nel.org, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com, liyonglong@...natelecom.cn
Subject: [PATCH] tcp: make retransmitted SKB fit into the send window

From: liyonglong <liyonglong@...natelecom.cn>

current code of __tcp_retransmit_skb only check TCP_SKB_CB(skb)->seq
in send window, it will cause retransmit more than send window data.

Signed-off-by: liyonglong <liyonglong@...natelecom.cn>
---
 net/ipv4/tcp_output.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 18c913a..3530d1f 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3176,7 +3176,7 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
 	    TCP_SKB_CB(skb)->seq != tp->snd_una)
 		return -EAGAIN;
 
-	len = cur_mss * segs;
+	len = min_t(int, tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq, cur_mss * segs);
 	if (skb->len > len) {
 		if (tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb, len,
 				 cur_mss, GFP_ATOMIC))
@@ -3190,7 +3190,7 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
 		diff -= tcp_skb_pcount(skb);
 		if (diff)
 			tcp_adjust_pcount(sk, skb, diff);
-		if (skb->len < cur_mss)
+		if (skb->len < cur_mss && len >= cur_mss)
 			tcp_retrans_try_collapse(sk, skb, cur_mss);
 	}
 
-- 
1.8.3.1