Re[2]: [PATCH 05/19] netfilter: nf_conntrack_ipv6: improve fragmentation handling

4 messages, 3 authors, 2012-08-23 · open the first message on its own page

Re[2]: [PATCH 05/19] netfilter: nf_conntrack_ipv6: improve fragmentation handling

From: Hans Schillstrom <hidden>
Date: 2012-08-22 05:01:24

Hi
On Sun, 2012-08-19 at 21:44 +0200, Patrick McHardy wrote:
quoted
On Sun, 19 Aug 2012, Jesper Dangaard Brouer wrote:
quoted
On Sat, 2012-08-18 at 14:26 +0200, Patrick McHardy wrote:
[...]
quoted
quoted
Don't I need to load some of the helper modules, or just the
nf_conntrack_ipv6 module, or perhaps only nf_defrag_ipv6 ?
Not with the entire patchset, just IPv6 conntrack is enough. Aith IPv6 NAT
the first packet of a connection must always be defragemented, independant
of an assigned helper.
When loading "nf_conntrack_ipv6" I run into issues.

When sending a fragmented UDP packet.  With these patches, the IPVS
stack will no longer see the fragmented packets, but instead see one
large SKB.  This will trigger a MTU path check in e.g.
ip_vs_dr_xmit_v6() and an ICMPv6 too big packet is send back.

 IPVS: ip_vs_dr_xmit_v6(): frag needed

Perhaps we could change/fix the MTU check in IPVS?
(This would also solve issues I've seen with TSO/GSO frames, hitting
this code path).
I ran into this as well, 
try this for the mtu check.

       if ((!skb->local_df && skb->len > mtu && !skb_is_gso(skb)) ||
           (IP6CB(skb)->frag_max_size && IP6CB(skb)->frag_max_size > mtu)) {

/Hans

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Re[2]: [PATCH 05/19] netfilter: nf_conntrack_ipv6: improve fragmentation handling

From: Julian Anastasov <ja@ssi.bg>
Date: 2012-08-22 07:07:16

	Hello,

On Wed, 22 Aug 2012, Hans Schillstrom wrote:
quoted
Perhaps we could change/fix the MTU check in IPVS?
(This would also solve issues I've seen with TSO/GSO frames, hitting
this code path).
I ran into this as well, 
try this for the mtu check.

       if ((!skb->local_df && skb->len > mtu && !skb_is_gso(skb)) ||
           (IP6CB(skb)->frag_max_size && IP6CB(skb)->frag_max_size > mtu)) {
	Better without local_df check, it is our job to
set it.

Regards

--
Julian Anastasov [off-list ref]

Re[2]: [PATCH 05/19] netfilter: nf_conntrack_ipv6: improve fragmentation handling

From: Julian Anastasov <ja@ssi.bg>
Date: 2012-08-22 07:15:26

	Hello,

On Wed, 22 Aug 2012, Julian Anastasov wrote:
On Wed, 22 Aug 2012, Hans Schillstrom wrote:
quoted
quoted
Perhaps we could change/fix the MTU check in IPVS?
(This would also solve issues I've seen with TSO/GSO frames, hitting
this code path).
I ran into this as well, 
try this for the mtu check.

       if ((!skb->local_df && skb->len > mtu && !skb_is_gso(skb)) ||
           (IP6CB(skb)->frag_max_size && IP6CB(skb)->frag_max_size > mtu)) {
	Better without local_df check, it is our job to
set it.
	Ops, sorry. It seems now nf_ct_frag6_reasm (Patch 02/18)
will set head->local_df = 1, so we should check local_df
as Hans said.

Regards

--
Julian Anastasov [off-list ref]

Re: Re[2]: [PATCH 05/19] netfilter: nf_conntrack_ipv6: improve fragmentation handling

From: Jesper Dangaard Brouer <hidden>
Date: 2012-08-23 14:49:20

On Wed, 2012-08-22 at 10:16 +0300, Julian Anastasov wrote:
	Hello,

On Wed, 22 Aug 2012, Julian Anastasov wrote:
quoted
On Wed, 22 Aug 2012, Hans Schillstrom wrote:
quoted
quoted
Perhaps we could change/fix the MTU check in IPVS?
(This would also solve issues I've seen with TSO/GSO frames, hitting
this code path).
I ran into this as well, 
try this for the mtu check.

       if ((!skb->local_df && skb->len > mtu && !skb_is_gso(skb)) ||
           (IP6CB(skb)->frag_max_size && IP6CB(skb)->frag_max_size > mtu)) {
	Better without local_df check, it is our job to
set it.
Will the IPVS usage of local_df, conflict with Patrick's usage?


	Ops, sorry. It seems now nf_ct_frag6_reasm (Patch 02/18)
will set head->local_df = 1, so we should check local_df
as Hans said.
With Hans'es version of the MTU check, IPVS seems to work again (with
Patricks patches applied).

(Also spotted the GSO problem I had with IPv6 + DR, and send an upstream
fix...)

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Sr. Network Kernel Developer at Red Hat
  Author of http://www.iptv-analyzer.org
  LinkedIn: http://www.linkedin.com/in/brouer

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