From mboxrd@z Thu Jan 1 00:00:00 1970 From: Shmulik Ladkani Subject: Re: [PATCH net v3] ipv4: allow local fragmentation in ip_finish_output_gso() Date: Fri, 4 Nov 2016 11:24:09 +0200 Message-ID: <20161104112409.6277b7b0@halley> References: <1478118977-19608-1-git-send-email-lrichard@redhat.com> <20161103094239.13ac8ac2@pixies> <274982955.93728733.1478178387534.JavaMail.zimbra@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, fw@strlen.de, jtluka@redhat.com, hannes@stressinduktion.org To: Lance Richardson Return-path: Received: from mail-wm0-f46.google.com ([74.125.82.46]:34819 "EHLO mail-wm0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751294AbcKDJYO (ORCPT ); Fri, 4 Nov 2016 05:24:14 -0400 Received: by mail-wm0-f46.google.com with SMTP id a197so37798353wmd.0 for ; Fri, 04 Nov 2016 02:24:13 -0700 (PDT) In-Reply-To: <274982955.93728733.1478178387534.JavaMail.zimbra@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: Hi, On Thu, 3 Nov 2016 09:06:27 -0400 (EDT) Lance Richardson wrote: > I'm not sure what could be added that would help, was there something > specific you had in mind? How about something like this (preliminary, feel free to massage): @@ -248,10 +248,16 @@ static int ip_finish_output_gso(struct net *net, struct sock *sk, /* Slowpath - GSO segment length is exceeding the dst MTU. * - * This can happen in two cases: - * 1) TCP GRO packet, DF bit not set - * 2) skb arrived via virtio-net, we thus get TSO/GSO skbs directly - * from host network stack. + * This can happen in several cases: + * - Forwarding of TCP GRO packet, DF bit not set + * - Forwarding of skb arrived in a virtualization environment (from + * virtio-net/vhost/tap) with TSO/GSO size set by other's network + * stack + * - Local GSO skb xmitted on an NETIF_F_TSO tunnel stacked over an + * interface with a smaller mtu + * - Arriving GRO skb (or GSO skb in a virtualized env) that gets L2 + * bridged to a NETIF_F_TSO tunnel stacked over an interface with an + * insufficent mtu */ features = netif_skb_features(skb); BUILD_BUG_ON(sizeof(*IPCB(skb)) > SKB_SGO_CB_OFFSET);