Re: 2.0.21: TCP hangs solved by disabling Path MTU Discovery

Derrick J. Brashear (
Wed, 25 Sep 1996 09:54:15 -0400 (EDT)

> Greetings,
> I recently reported that HTTP connections were hanging without sending
> any data under 2.0.21. Alan Cox's suggestion of building with Path
> MTU Discovery disabled has resolved that problem. Thanks Alan,
> everything seems to be working fine now. I'll know for sure tonight
> when cron runs the tape backup (which also failed under the old kernel).
> The listing for Path MTU Discovery suggests it's only
> useful for broken PC clients. But many non-local machines including my
> PC running 2.0.20 failed to connect to this machine until I rebuilt it
> as described. The machine is on a TCP/IP network connected via a Cisco
> on a Frame Relay 56k link. Since this is standard technology I'm
> uncertain why we ran into the problem. Should broaden
> it's description of the Path MTU Discovery option or is there still a
> bug hiding somewhere?

I put back a piece of code that had been if 0'd out around 2.0.16 to get this
to work with the path mtu discovery, but when I posted the patch as a possible
fix for the PPP problems I was having, someone else posted that the patch was
in there because it was making something break on his machine. Who knows?

Note to sparclinux people: Perhaps path MTU should default to disabled? (I
recall that it doesn't, but my SparcLinux box is, um, not here at the moment)