Re: [OpenWrt-Devel] MSS clamping in POSTROUTING instead of FORWARD?

2012-03-02 Thread Ashok Rao
I don't see why moving the clamping to POSTROUTING causes the hiding of issues inside openwrt. The example presented by Etienne is perfectly valid and the suggestion to mpve the clamping to the POSTROUTING chain seems the right way to go when you have multiple interfaces that could be used for a pa

Re: [OpenWrt-Devel] MSS clamping in POSTROUTING instead of FORWARD?

2012-02-22 Thread Philip Prindeville
On 2/22/12 12:24 PM, Oliver wrote: > On Wednesday 22 Feb 2012 10:09:09 Philip Prindeville wrote: >> I actually don't think that. >> >> I'm just pointing out that in corner cases, being overly conservative >> will increase your chances of success. > > Correct, but it does so by essentially alleviat

Re: [OpenWrt-Devel] MSS clamping in POSTROUTING instead of FORWARD?

2012-02-22 Thread Oliver
On Wednesday 22 Feb 2012 10:09:09 Philip Prindeville wrote: > I actually don't think that. > > I'm just pointing out that in corner cases, being overly conservative > will increase your chances of success. Correct, but it does so by essentially alleviating the symptom of an underlying problem; s

Re: [OpenWrt-Devel] MSS clamping in POSTROUTING instead of FORWARD?

2012-02-22 Thread Philip Prindeville
On 2/22/12 7:59 AM, Oliver wrote: > On Tuesday 21 Feb 2012 20:27:19 Philip Prindeville wrote: > >> There are also a lot of routers out there that *still* don't do PMTU >> correct ('still', because I worked on the standard more than 20 years >> ago). > > What we're discussing here is moving TCPMSS

Re: [OpenWrt-Devel] MSS clamping in POSTROUTING instead of FORWARD?

2012-02-22 Thread Oliver
On Tuesday 21 Feb 2012 20:27:19 Philip Prindeville wrote: > There are also a lot of routers out there that *still* don't do PMTU > correct ('still', because I worked on the standard more than 20 years > ago). What we're discussing here is moving TCPMSS such that packets to and from the OpenWRT r

Re: [OpenWrt-Devel] MSS clamping in POSTROUTING instead of FORWARD?

2012-02-22 Thread Etienne Champetier
Le 22/02/2012 04:27, Philip Prindeville a écrit : > On 2/21/12 3:21 PM, Oliver wrote: >> On Tuesday 21 Feb 2012 22:19:19 Etienne Champetier wrote: >>> A plausible example: >>> First default route: optical fiber (MTU 1500) >>> Second default route: pppoe (MTU 1492) (failover link) >>> If the optica

Re: [OpenWrt-Devel] MSS clamping in POSTROUTING instead of FORWARD?

2012-02-21 Thread Philip Prindeville
On 2/21/12 3:21 PM, Oliver wrote: > On Tuesday 21 Feb 2012 22:19:19 Etienne Champetier wrote: >> >> A plausible example: >> First default route: optical fiber (MTU 1500) >> Second default route: pppoe (MTU 1492) (failover link) >> If the optical fiber goes down, the traffic from the router will pas

Re: [OpenWrt-Devel] MSS clamping in POSTROUTING instead of FORWARD?

2012-02-21 Thread Oliver
On Tuesday 21 Feb 2012 22:19:19 Etienne Champetier wrote: > > A plausible example: > First default route: optical fiber (MTU 1500) > Second default route: pppoe (MTU 1492) (failover link) > If the optical fiber goes down, the traffic from the router will pass > through the PPPoE link, but with a M

Re: [OpenWrt-Devel] MSS clamping in POSTROUTING instead of FORWARD?

2012-02-21 Thread Philip Prindeville
Ok, maybe I'm taking an overly simplistic view of this, but if you assume that a packet can go out either interface, you need to assume it can come back via either interface as well, right? In which case don't you want to set the MSS to the minimum value of all interfaces? Assuming you have lo

Re: [OpenWrt-Devel] MSS clamping in POSTROUTING instead of FORWARD?

2012-02-21 Thread Etienne Champetier
Hello TCPMSS is now (since 28669 & 28671, 4 month) in the mangle table I know I can fix it but it's the default behaviour of openwrt to break ICMP (by default it only accept ipv4 icmp echo-request on wan) Here a good schema of netfilter to understand (http://upload.wikimedia.org/wikipedia/comm

Re: [OpenWrt-Devel] MSS clamping in POSTROUTING instead of FORWARD?

2012-02-18 Thread Oliver
On Saturday 18 Feb 2012 19:32:04 Etienne Champetier wrote: > Hello > > Is there a reason why the MSS clamping is done in FORWARD instead of > POSTROUTING ? (it's the exemple in the manpage...) > you shouldn't /need/ to clamp the MSS of packets to and from the router unless you're breaking ICMP,

[OpenWrt-Devel] MSS clamping in POSTROUTING instead of FORWARD?

2012-02-18 Thread Etienne Champetier
Hello Is there a reason why the MSS clamping is done in FORWARD instead of POSTROUTING ? (it's the exemple in the manpage...) I'm asking this question for 2 reasons: -the traffic originating from the router (OUTPUT) is not treated -with the multiwan package (don't know if it's true with every mu