| Message ID | 1383756740-7392-2-git-send-email-jiri@resnulli.us |
|---|---|
| State | Awaiting Upstream |
| Headers | show |
From: Jiri Pirko <jiri@resnulli.us> Date: Wed, 6 Nov 2013 17:52:19 +0100 > If reassembled packet would fit into outdev MTU, it is not fragmented > according the original frag size and it is send as single big packet. > > The second case is if skb is gso. In that case fragmentation does not happen > according to the original frag size. > > This patch fixes these. > > Signed-off-by: Jiri Pirko <jiri@resnulli.us> ... > if ((skb->len > ip6_skb_dst_mtu(skb) && !skb_is_gso(skb)) || > - dst_allfrag(skb_dst(skb))) > + dst_allfrag(skb_dst(skb)) || > + (IP6CB(skb)->frag_max_size && skb->len > IP6CB(skb)->frag_max_size)) > return ip6_fragment(skb, ip6_finish_output2); Jiri are you sure that you don't need to take GSO into account in the new part you are adding to the test? -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Fri, Nov 08, 2013 at 12:54:53AM CET, davem@davemloft.net wrote: >From: Jiri Pirko <jiri@resnulli.us> >Date: Wed, 6 Nov 2013 17:52:19 +0100 > >> If reassembled packet would fit into outdev MTU, it is not fragmented >> according the original frag size and it is send as single big packet. >> >> The second case is if skb is gso. In that case fragmentation does not happen >> according to the original frag size. >> >> This patch fixes these. >> >> Signed-off-by: Jiri Pirko <jiri@resnulli.us> > ... > >> if ((skb->len > ip6_skb_dst_mtu(skb) && !skb_is_gso(skb)) || >> - dst_allfrag(skb_dst(skb))) >> + dst_allfrag(skb_dst(skb)) || >> + (IP6CB(skb)->frag_max_size && skb->len > IP6CB(skb)->frag_max_size)) >> return ip6_fragment(skb, ip6_finish_output2); > >Jiri are you sure that you don't need to take GSO into account in the >new part you are adding to the test? For gso skb, we need co cap outgoing fragments by the original frag size as well. So I believe that this code is correct for that case as well. >-- >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 -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
From: Jiri Pirko <jiri@resnulli.us> Date: Fri, 8 Nov 2013 08:52:01 +0100 > Fri, Nov 08, 2013 at 12:54:53AM CET, davem@davemloft.net wrote: >>From: Jiri Pirko <jiri@resnulli.us> >>Date: Wed, 6 Nov 2013 17:52:19 +0100 >> >>> If reassembled packet would fit into outdev MTU, it is not fragmented >>> according the original frag size and it is send as single big packet. >>> >>> The second case is if skb is gso. In that case fragmentation does not happen >>> according to the original frag size. >>> >>> This patch fixes these. >>> >>> Signed-off-by: Jiri Pirko <jiri@resnulli.us> >> ... >> >>> if ((skb->len > ip6_skb_dst_mtu(skb) && !skb_is_gso(skb)) || >>> - dst_allfrag(skb_dst(skb))) >>> + dst_allfrag(skb_dst(skb)) || >>> + (IP6CB(skb)->frag_max_size && skb->len > IP6CB(skb)->frag_max_size)) >>> return ip6_fragment(skb, ip6_finish_output2); >> >>Jiri are you sure that you don't need to take GSO into account in the >>new part you are adding to the test? > > > For gso skb, we need co cap outgoing fragments by the original frag size > as well. So I believe that this code is correct for that case as well. I'm still not so sure I agree, even after having taken a second look at this. Look at ipv4's logic for this same facility: if (skb->len > ip_skb_dst_mtu(skb) && !skb_is_gso(skb)) return ip_fragment(skb, ip_finish_output2); Strictly, we only call ip_fragment() if skb_is_gso() is false. And then in ip_fragment(): if (unlikely(((iph->frag_off & htons(IP_DF)) && !skb->local_df) || (IPCB(skb)->frag_max_size && IPCB(skb)->frag_max_size > dst_mtu(&rt->dst)))) { And that second branch of this test is what you're trying to duplicate into ipv6. Perhaps I don't understand completely the intentions and logic of dst_allfrag() in the ipv6 case, and maybe you can explain it to me. -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Fri, Nov 08, 2013 at 02:49:15PM -0500, David Miller wrote: > Perhaps I don't understand completely the intentions and logic of > dst_allfrag() in the ipv6 case, and maybe you can explain it to me. dst_allfrag gets active if we receive a PMTU packet indicating a MTU smaller than 1280. Of course IPv6 may not go below 1280 but this indicates e.g. a IPv6->IPv4 migration technology is on the path which needs the IPv6 fragment header and its fragment id to generate IPv4 fragment ids out of the IPv6 ones to produce IPv4 fragments just after this migration router which could well be smaller than 1280. Maybe this does help a bit, Hannes -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Fri, Nov 08, 2013 at 08:49:15PM CET, davem@davemloft.net wrote: >From: Jiri Pirko <jiri@resnulli.us> >Date: Fri, 8 Nov 2013 08:52:01 +0100 > >> Fri, Nov 08, 2013 at 12:54:53AM CET, davem@davemloft.net wrote: >>>From: Jiri Pirko <jiri@resnulli.us> >>>Date: Wed, 6 Nov 2013 17:52:19 +0100 >>> >>>> If reassembled packet would fit into outdev MTU, it is not fragmented >>>> according the original frag size and it is send as single big packet. >>>> >>>> The second case is if skb is gso. In that case fragmentation does not happen >>>> according to the original frag size. >>>> >>>> This patch fixes these. >>>> >>>> Signed-off-by: Jiri Pirko <jiri@resnulli.us> >>> ... >>> >>>> if ((skb->len > ip6_skb_dst_mtu(skb) && !skb_is_gso(skb)) || >>>> - dst_allfrag(skb_dst(skb))) >>>> + dst_allfrag(skb_dst(skb)) || >>>> + (IP6CB(skb)->frag_max_size && skb->len > IP6CB(skb)->frag_max_size)) >>>> return ip6_fragment(skb, ip6_finish_output2); >>> >>>Jiri are you sure that you don't need to take GSO into account in the >>>new part you are adding to the test? >> >> >> For gso skb, we need co cap outgoing fragments by the original frag size >> as well. So I believe that this code is correct for that case as well. > >I'm still not so sure I agree, even after having taken a second look >at this. > >Look at ipv4's logic for this same facility: > > if (skb->len > ip_skb_dst_mtu(skb) && !skb_is_gso(skb)) > return ip_fragment(skb, ip_finish_output2); > >Strictly, we only call ip_fragment() if skb_is_gso() is false. And then >in ip_fragment(): > > if (unlikely(((iph->frag_off & htons(IP_DF)) && !skb->local_df) || > (IPCB(skb)->frag_max_size && > IPCB(skb)->frag_max_size > dst_mtu(&rt->dst)))) { > >And that second branch of this test is what you're trying to duplicate >into ipv6. That is a different check and the same one is already in ip6_fragment(). You cannot compare this to ipv4 directly. In ipv4 if frag skbs are reassembled into one, they can be forwarded out in different frag sizes (bigger or smaller) or not in frags at all. Therefore you can lay off the work to offload. But for ipv6, the same frags need to go out as they came in. Offload would not do that as it would try to max the flag sizes to the MTU -> That is exactly why I add the "skb->len > IP6CB(skb)->frag_max_size" check. Imagine scenario: hostA-NIC(MTU1400) ------ NIC(MTU1400)-hostB-NIC(MTU1500) ------ NIC(MTU1500)-hostC And fragmented packets go hostA->hostB->hostC, and we are doing forwadring on hostB. I hope I cleared this out. -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
From: Jiri Pirko <jiri@resnulli.us> Date: Sat, 9 Nov 2013 12:00:53 +0100 > I hope I cleared this out. Thanks for the explanation, I see now. -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" 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/ipv6/ip6_output.c b/net/ipv6/ip6_output.c index 91fb4e8..5e31a90 100644 --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -125,7 +125,8 @@ static int ip6_finish_output2(struct sk_buff *skb) static int ip6_finish_output(struct sk_buff *skb) { if ((skb->len > ip6_skb_dst_mtu(skb) && !skb_is_gso(skb)) || - dst_allfrag(skb_dst(skb))) + dst_allfrag(skb_dst(skb)) || + (IP6CB(skb)->frag_max_size && skb->len > IP6CB(skb)->frag_max_size)) return ip6_fragment(skb, ip6_finish_output2); else return ip6_finish_output2(skb);
If reassembled packet would fit into outdev MTU, it is not fragmented according the original frag size and it is send as single big packet. The second case is if skb is gso. In that case fragmentation does not happen according to the original frag size. This patch fixes these. Signed-off-by: Jiri Pirko <jiri@resnulli.us> --- net/ipv6/ip6_output.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)