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Opened 4 years ago

Last modified 4 years ago

#14732 new defect

Calculate max frame length properly on TEW-632BRP

Reported by: Nikolay Martynov <mar.kolya@…> Owned by: developers
Priority: normal Milestone: Barrier Breaker 14.07
Component: packages Version: Trunk
Keywords: Cc:

Description

The r39147 commit introduces a regression: at lease on some routers
with ar8216 switch large packets get lost if 802.1q tagged port is
used on the interface connected to the aforementioned switch.

The r39147 changes code in the way so interface is set to accept
packets no longer than max ethernet frame length for a given mtu.

Unfortunately ar8216 has a feature: it sends to additional bytes as a
packet header and those this header needs to be added to the max frame
length. Otherwise long enough packets get lost.

The problem only manuifests itself if interface is used in vlan tagged
mode. If integface is untagged then ar8216's header fits into space
used by 802.1q tag and not packets are lost.

This patch is tested and works with Trendnet TEW-632BRP.

Attachments (5)

0001-Calculate-max-frame-length-properly-on-TEW-632BRP.patch (5.4 KB) - added by Nikolay Martynov <mar.kolya@…> 4 years ago.
0002-Calculate-max-frame-length-properly-on-DIR-615-c1.patch (1.2 KB) - added by Nikolay Martynov <mar.kolya@…> 4 years ago.
0002-Calculate-max-frame-length-properly-on-DIR-615-c1.2.patch (1.2 KB) - added by Nikolay Martynov <mar.kolya@…> 4 years ago.
0002-Calculate-max-frame-length-properly-on-DIR-615-c1.3.patch (1.2 KB) - added by Nikolay Martynov <mar.kolya@…> 4 years ago.
0002-Calculate-max-frame-length-properly-on-DIR-615-c1.4.patch (1.2 KB) - added by Nikolay Martynov <mar.kolya@…> 4 years ago.

Download all attachments as: .zip

Change History (10)

Changed 4 years ago by Nikolay Martynov <mar.kolya@…>

Changed 4 years ago by Nikolay Martynov <mar.kolya@…>

Changed 4 years ago by Nikolay Martynov <mar.kolya@…>

Changed 4 years ago by Nikolay Martynov <mar.kolya@…>

Changed 4 years ago by Nikolay Martynov <mar.kolya@…>

comment:1 Changed 4 years ago by Nikolay Martynov <mar.kolya@…>

Sorry, I didn't intend to add second patch three times. I was getting nginx error in server response and wasn't sure if it was attached or not.

comment:2 follow-up: Changed 4 years ago by anonymous

Dear Nikolay,

I have just compiled OpenWRT for this device:

http://wiki.openwrt.org/toh/astoria/arv752dpw22

everything works except VLANS. Large packets constantly get discarded. I started studying your patches however I am only a beginner and I am having difficulty adapting it to this device. Could you help? Thanks!

Gennady

comment:3 in reply to: ↑ 2 Changed 4 years ago by gennady.uraltsev@…

Replying to anonymous:

Dear Nikolay,

I have just compiled OpenWRT for this device:

http://wiki.openwrt.org/toh/astoria/arv752dpw22

everything works except VLANS. Large packets constantly get discarded. I started studying your patches however I am only a beginner and I am having difficulty adapting it to this device. Could you help? Thanks!

Gennady

Sorry, my email is gennady.uraltsev@… The registration seems broken: I tried to register here on trac but it fails (do you know who I should write to about that?)

comment:4 Changed 4 years ago by mar.kolya@…

As far as I know the bug was fixed in trunk. I think I've verified it after that and it was working fine. At the moment I'm not using VLANs on my device so I cannot really say for sure if it works or not.

The interesting this is that the patch that got committed to trunk is not device dependent, so it should just work now if you are hitting issue described in this ticket.

So, I guess I can suggest the following:

1) Try building latest trunk.

2) Try building version before commit r39147 - this commit introduced the bug.

If that doesn't help I guess you'd have to diagnose the issue deeper since chances are you are seeing a different issue. You may want to check if decreasing MTU actually helps and figure out what maximum properly working MTU (and packet size) is. Also it might help if you verify if there are any relevant errors in logread or dmesg.

Hope this helps.

comment:5 Changed 4 years ago by jow

  • Milestone changed from Attitude Adjustment 12.09 to Barrier Breaker 14.07

Milestone Attitude Adjustment 12.09 deleted

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