From patchwork Mon Sep 17 07:58:22 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [net] e1000: Small packets may get corrupted during padding by HW Date: Sun, 16 Sep 2012 21:58:22 -0000 From: Eric Dumazet X-Patchwork-Id: 184316 Message-Id: <1347868702.26523.79.camel@edumazet-glaptop> To: "Dave, Tushar N" Cc: "Fastabend, John R" , Michal Miroslaw , "Kirsher, Jeffrey T" , "davem@davemloft.net" , "netdev@vger.kernel.org" , "gospo@redhat.com" , "sassmann@redhat.com" On Mon, 2012-09-17 at 07:33 +0000, Dave, Tushar N wrote: > >-----Original Message----- > >From: netdev-owner@vger.kernel.org [mailto:netdev-owner@vger.kernel.org] > >On Behalf Of John Fastabend > >Also wouldn't you want an unlikely() in your patch? > > No because it is quite normal to have packet < ETH_ZLEN. e.g. ARP packets. ARP packets ? Hardly a performance problem. Or make sure all these packets have enough tailroom, or else you are going to hit the cost of reallocating packets. I would better point TCP pure ACK packets, since their size can be 54 bytes. --- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index cfe6ffe..aefc681 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -3083,8 +3083,9 @@ void tcp_send_ack(struct sock *sk) /* We are not putting this on the write queue, so * tcp_transmit_skb() will set the ownership to this * sock. + * Add 64 bytes of tailroom so that some drivers can use skb_pad() */ - buff = alloc_skb(MAX_TCP_HEADER, sk_gfp_atomic(sk, GFP_ATOMIC)); + buff = alloc_skb(MAX_TCP_HEADER + 64, sk_gfp_atomic(sk, GFP_ATOMIC)); if (buff == NULL) { inet_csk_schedule_ack(sk); inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;