netdev - [RFC PATCH 10/28] gro: prevent ACE field corruption & better AccECN handling

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Message-Id: <1584524289-24187-10-git-send-email-ilpo.jarvinen@helsinki.fi>
Date:   Wed, 18 Mar 2020 11:37:51 +0200
From:   Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>
To:     netdev@...r.kernel.org
Cc:     Yuchung Cheng <ycheng@...gle.com>,
        Neal Cardwell <ncardwell@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Olivier Tilmans <olivier.tilmans@...ia-bell-labs.com>
Subject: [RFC PATCH 10/28] gro: prevent ACE field corruption & better AccECN handling

From: Ilpo Järvinen <ilpo.jarvinen@...helsinki.fi>

There are important differences in how the CWR field behaves
in RFC3168 and AccECN.

Thus, it is better to never let anything to receive
a mixed-CWR skb. Set the Accurate ECN GSO flag to
avoid corrupting CWR bits somewhere.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...helsinki.fi>
---
 net/ipv4/tcp_offload.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c
index 7a81cf438010..58ce382c793e 100644
--- a/net/ipv4/tcp_offload.c
+++ b/net/ipv4/tcp_offload.c
@@ -242,7 +242,7 @@ struct sk_buff *tcp_gro_receive(struct list_head *head, struct sk_buff *skb)
 	flush = NAPI_GRO_CB(p)->flush;
 	flush |= (__force int)(flags & TCP_FLAG_CWR);
 	flush |= (__force int)((flags ^ tcp_flag_word(th2)) &
-		  ~(TCP_FLAG_CWR | TCP_FLAG_FIN | TCP_FLAG_PSH));
+		  ~(TCP_FLAG_FIN | TCP_FLAG_PSH));
 	flush |= (__force int)(th->ack_seq ^ th2->ack_seq);
 	for (i = sizeof(*th); i < thlen; i += 4)
 		flush |= *(u32 *)((u8 *)th + i) ^
@@ -300,7 +300,7 @@ int tcp_gro_complete(struct sk_buff *skb)
 	skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
 
 	if (th->cwr)
-		skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
+		skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ACCECN;
 
 	return 0;
 }
-- 
2.20.1