netdev - Re: [PATCH net-next] tcp: get rid of sysctl_tcp_adv_win

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Message-ID: <CANn89iKoaTjaK7s_66EOHAYw+drT3XTEhT5xBcFU1iHTYr_aug@mail.gmail.com>
Date: Sat, 6 Apr 2024 08:11:32 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: shironeko@...aguri.club
Cc: Jose Alonso <joalonsof@...il.com>, "David S . Miller" <davem@...emloft.net>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org, 
	Soheil Hassas Yeganeh <soheil@...gle.com>, Neal Cardwell <ncardwell@...gle.com>, 
	Yuchung Cheng <ycheng@...gle.com>, eric.dumazet@...il.com
Subject: Re: [PATCH net-next] tcp: get rid of sysctl_tcp_adv_win_scale

On Sat, Apr 6, 2024 at 2:22 AM <shironeko@...aguri.club> wrote:
>
> The patch seems to be working, no more dmesg errors or network cut-outs. Thank you!
>
> There is however this line printed yesterday afternoon, so seem there's still some weirdness.
> > TCP: eth0: Driver has suspect GRO implementation, TCP performance may be compromised.

This is great, could you add the following to get some details from the skb ?

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 1b6cd384001202df5f8e8e8c73adff0db89ece63..e30895a9cc8627cf423c3c5a783d525db0b2db8e
100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -209,9 +209,11 @@ static __cold void tcp_gro_dev_warn(const struct
sock *sk, const struct sk_buff

        rcu_read_lock();
        dev = dev_get_by_index_rcu(sock_net(sk), skb->skb_iif);
-       if (!dev || len >= READ_ONCE(dev->mtu))
+       if (!dev || len >= READ_ONCE(dev->mtu)) {
+               skb_dump(KERN_ERR, skb, false);
                pr_warn("%s: Driver has suspect GRO implementation,
TCP performance may be compromised.\n",
                        dev ? dev->name : "Unknown driver");
+       }
        rcu_read_unlock();
 }