netdev - [PATCH net] gro: take care of DODGY packets

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Message-ID: <20230106142523.1234476-1-edumazet@google.com>
Date:   Fri,  6 Jan 2023 14:25:23 +0000
From:   Eric Dumazet <edumazet@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com,
        Eric Dumazet <edumazet@...gle.com>,
        Jaroslav Pulchart <jaroslav.pulchart@...ddata.com>,
        Coco Li <lixiaoyan@...gle.com>
Subject: [PATCH net] gro: take care of DODGY packets

Jaroslav reported a recent throughput regression with virtio_net
caused by blamed commit.

It is unclear if DODGY GSO packets coming from user space
can be accepted by GRO engine in the future with minimal
changes, and if there is any expected gain from it.

In the meantime, make sure to detect and flush DODGY packets.

Fixes: 5eddb24901ee ("gro: add support of (hw)gro packets to gro stack")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Reported-and-bisected-by: Jaroslav Pulchart <jaroslav.pulchart@...ddata.com>
Cc: Coco Li <lixiaoyan@...gle.com>
Cc: Paolo Abeni <pabeni@...hat.com>
---
 net/core/gro.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/core/gro.c b/net/core/gro.c
index fd8c6a7e8d3e2e6b439109d0089f44a547c7347e..506f83d715f873c9bc3727e28ace71e00fa79d2f 100644
--- a/net/core/gro.c
+++ b/net/core/gro.c
@@ -505,8 +505,9 @@ static enum gro_result dev_gro_receive(struct napi_struct *napi, struct sk_buff
 	NAPI_GRO_CB(skb)->count = 1;
 	if (unlikely(skb_is_gso(skb))) {
 		NAPI_GRO_CB(skb)->count = skb_shinfo(skb)->gso_segs;
-		/* Only support TCP at the moment. */
-		if (!skb_is_gso_tcp(skb))
+		/* Only support TCP and non DODGY users. */
+		if (!skb_is_gso_tcp(skb) ||
+		    (skb_shinfo(skb)->gso_type & SKB_GSO_DODGY))
 			NAPI_GRO_CB(skb)->flush = 1;
 	}
 
-- 
2.39.0.314.g84b9a713c41-goog