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Date: Thu, 18 Apr 2013 18:07:32 +0100 From: Ben Hutchings <bhutchings@...arflare.com> To: Jim Baxter <jim_baxter@...tor.com> CC: Eric Dumazet <eric.dumazet@...il.com>, "David S. Miller" <davem@...emloft.net>, Frank Li <Frank.Li@...escale.com>, Fugang Duan <B38611@...escale.com>, <netdev@...r.kernel.org>, Fabio Estevam <festevam@...il.com>, Francois Romieu <romieu@...zoreil.com> Subject: Re: [PATCH net-next v3 1/1] net: fec: Enable imx6 enet checksum acceleration. On Thu, 2013-04-18 at 17:16 +0100, Ben Hutchings wrote: [...] > But you don't actually need to check protocol numbers at all, as the > kernel already specifies where the checksum should be. > > So I think this function should look like: > { > if (skb->ip_summed != CHECKSUM_PARTIAL) > return 0; > > if (unlikely(skb_cow_head(skb, 0))) > return -1; > > *(__sum16 *)(skb->head + skb->csum_start + skb->csum_offset) = 0; > return 0; > } > > The caller needs to check for the failure, and free the skb > (kfree_skb()) rather than transmitting it. Oh, presumably you still need to clear the IPv4 header checksum as well. But it might be better to enable only TCP/UDP checksumming, because Linux always calculates the IPv4 header checksum in software. Ben. -- Ben Hutchings, Staff Engineer, Solarflare Not speaking for my employer; that's the marketing department's job. They asked us to note that Solarflare product names are trademarked. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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