tech-net: Re: SIOCIFMTU on lo (faith, ...) -- how to update route MTU?

Subject: Re: SIOCIFMTU on lo (faith, ...) -- how to update route MTU?
To: Jonathan Stone <jonathan@DSG.Stanford.EDU>
From: None <itojun@iijlab.net>
List: tech-net
Date: 04/20/2000 12:12:05

>Last-year-ish, I added SIOCSIFMTU support to the loopback driver.
>Works like a champ, and makes it easy to test MTU-specific hacks over
>a loopback interface. (e.g., looking for spikes in TCP throughput as a
>function of MTU).
>The one gotcha is that if I change the MTU after bringing the interface
>up and ifconfig'ing 127.0.0.1 on it, the route MTU does *not* get updated.
>I tried copying the code from if_faith, and lo and behold, that seems
>broken, too.

	(not a good news) sorry, if_faith.c will not update it for interface
	routes, anyways.  copying code from if_faith.c will not do the right
	thing.  the SIOCSIFMTU part in if_faith.c is not that tested.

itojun