netdev - Re: [PATCH net] net: sungem: fix rx checksum support

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Message-Id: <20180620.143050.313454768369559179.davem@davemloft.net>
Date:   Wed, 20 Jun 2018 14:30:50 +0900 (KST)
From:   David Miller <davem@...emloft.net>
To:     edumazet@...gle.com
Cc:     netdev@...r.kernel.org, mroos@...ux.ee, malat@...ian.org,
        schwab@...ux-m68k.org, eric.dumazet@...il.com
Subject: Re: [PATCH net] net: sungem: fix rx checksum support

From: Eric Dumazet <edumazet@...gle.com>
Date: Tue, 19 Jun 2018 19:18:50 -0700

> After commit 88078d98d1bb ("net: pskb_trim_rcsum() and CHECKSUM_COMPLETE
> are friends"), sungem owners reported the infamous "eth0: hw csum failure"
> message.
> 
> CHECKSUM_COMPLETE has in fact never worked for this driver, but this
> was masked by the fact that upper stacks had to strip the FCS, and
> therefore skb->ip_summed was set back to CHECKSUM_NONE before
> my recent change.
> 
> Driver configures a number of bytes to skip when the chip computes
> the checksum, and for some reason only half of the Ethernet header
> was skipped.
> 
> Then a second problem is that we should strip the FCS by default,
> unless the driver is updated to eventually support NETIF_F_RXFCS in
> the future.
> 
> Finally, a driver should check if NETIF_F_RXCSUM feature is enabled
> or not, so that the admin can turn off rx checksum if wanted.
> 
> Many thanks to Andreas Schwab and Mathieu Malaterre for their
> help in debugging this issue.
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: Meelis Roos <mroos@...ux.ee>
> Reported-by: Mathieu Malaterre <malat@...ian.org>
> Reported-by: Andreas Schwab <schwab@...ux-m68k.org>
> Tested-by: Andreas Schwab <schwab@...ux-m68k.org>

Applied and queued up for -stable, thanks Eric.