netdev - RE: 2.6.20.7 mss negotiation and path mtu discovery mostly broken?

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <7CCD07160348804497EF29E9EA5560D7020F6206@exchtewks2.starentnetworks.com>
Date:	Wed, 25 Apr 2007 10:31:23 -0400
From:	"Ristuccia, Brian" <bristuccia@...rentnetworks.com>
To:	"Andi Kleen" <andi@...stfloor.org>
Cc:	<linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>
Subject: RE: 2.6.20.7 mss negotiation and path mtu discovery mostly broken?

> > 08:39:55.493029 IP 12.33.234.69.35026 > 10.2.10.254.22: S 
> > 2768979373:2768979373(
> > 0) win 5840 <mss 1460,sackOK,timestamp 3873837730 0,nop,wscale 2>
> > 08:39:55.493119 IP 10.2.10.254.22 > 12.33.234.69.35026: S
> > 963242385:963242385(0)
> >  ack 2768979374 win 17896 <mss 8960,sackOK,timestamp 413751
> 
> The MSS clamp for sending to 10.2.10.254.22 is 8960. MSS is 
> only one way -- each uses what the other tells it.
> 

Right - except that 10.2.10.254 keeps sending to 12.33.234.69 with an
increasingly large MSS, even though 12.33.234.69 has asked for no larger
than 1460.

> > In the following dump, the system eventually gets in a 
> state where it 
> > oscillates between sendng undeliverable 2896 byte packets and 
> > deliverable 1448 byte ones.
> 
> This should only happen on PMTU expire, which is normally ~15mins.
> Perhaps you misconfigured it manually using sysctl.
> 

This is /proc/sys/net/ipv4/route/mtu_expires? It's 600.

-- 
Brian Ristuccia

"This email message and any attachments are confidential information of Starent Networks, Corp. The information transmitted may not be used to create or change any contractual obligations of Starent Networks, Corp.  Any review, retransmission, dissemination or other use of, or taking of any action in reliance upon this e-mail and its attachments by persons or entities other than the intended recipient is prohibited. If you are not the intended recipient, please notify the sender immediately -- by replying to this message or by sending an email to postmaster@...rentnetworks.com -- and destroy all copies of this message and any attachments without reading or disclosing their contents. Thank you."
-
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html