Re: Broken PMTUD in FreeBSD?

From: Phil Dibowitz (
Date: 06/12/02

Date: Tue, 11 Jun 2002 23:48:48 -0700
From: Phil Dibowitz <>

I thought I'd update the list:

Mike Silbersack, a FreeBSD developer, had the following to say to me and the
freebsd-net list:
> I did some quick investigation last night, and agree with Phil that this
> is a bug. When the syncache was implemented, only a subset of the normal
> tcp output code was copied over for the purpose of sending syn-acks. One
> part of the code that was not moved over was the part that determines when
> the DF and tos bits are set.
> I also agree with Mikael that this isn't an important issue, given that
> syn-ack packets are quite tiny. Nonetheless, I will commit a fix in the
> next few days. However, it's too late to MFC it in time for 4.6-release.

So it will be fixed, and it was a bug. Thanks to everyone who responded, and
thanks to Mike for the quick response.


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