netdev - Re: [PATCH net] r8169: work around short packet hw bug on RTL8125

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Message-ID: <20201104174521.2a902678@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Wed, 4 Nov 2020 17:45:21 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Heiner Kallweit <hkallweit1@...il.com>
Cc:     David Miller <davem@...emloft.net>,
        Realtek linux nic maintainers <nic_swsd@...ltek.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Maxim Plotnikov <wgh@...lan.ru>
Subject: Re: [PATCH net] r8169: work around short packet hw bug on RTL8125

On Tue, 3 Nov 2020 18:52:18 +0100 Heiner Kallweit wrote:
> Network problems with RTL8125B have been reported [0] and with help
> from Realtek it turned out that this chip version has a hw problem
> with short packets (similar to RTL8168evl). Having said that activate
> the same workaround as for RTL8168evl.
> Realtek suggested to activate the workaround for RTL8125A too, even
> though they're not 100% sure yet which RTL8125 versions are affected.
> 
> [0] https://bugzilla.kernel.org/show_bug.cgi?id=209839
> 
> Fixes: 0439297be951 ("r8169: add support for RTL8125B")
> Reported-by: Maxim Plotnikov <wgh@...lan.ru>
> Tested-by: Maxim Plotnikov <wgh@...lan.ru>
> Signed-off-by: Heiner Kallweit <hkallweit1@...il.com>

Applied, thanks!

> @@ -4125,7 +4133,7 @@ static bool rtl8169_tso_csum_v2(struct rtl8169_private *tp,
>  
>  		opts[1] |= transport_offset << TCPHO_SHIFT;
>  	} else {
> -		if (unlikely(rtl_test_hw_pad_bug(tp, skb)))
> +		if (unlikely(skb->len < ETH_ZLEN && rtl_test_hw_pad_bug(tp)))
>  			return !eth_skb_pad(skb);
>  	}

But looks like we may have another bug here - looks like this function
treas skb_cow_head() and eth_skb_pad() failures the same, but former
doesn't free the skb on error, while the latter does.