Re: softmac mtu

On 9/23/06, Arnaldo Carvalho de Melo [off-list ref] wrote:

On 9/23/06, Larry Finger [off-list ref] wrote:

quoted

David Miller wrote:

quoted

From: Larry Finger <redacted>
Date: Sat, 23 Sep 2006 16:40:15 -0500

quoted

The maximum value for MTU is set in include/linux/if_ether.h for all
ethernet-type communications, not in softmac or ieee80211. I doubt
that one could easily change the number. It may be that the 802.11
standard allows bigger frames, but it looks to me as if Linux does
not.

Not correct.  Linux is perfectly fine with setting 9000 byte MTU on
ethernet devices that support it, and in fact just about every
gigabit ethernet driver supports it.

That macro you see in if_ether.h is just the value of the base MTU
limit, so larger MTU settings are easily allowable on a per-device
basis.

Where/how does the device allow it? When I tried 'ifconfig eth0 mtu 2000' on my VIA Technologies,
Inc. VT6102 [Rhine-II] wired controller, I got a 'SIOCSIFMTU: Invalid argument' message, which is
the same message I get on my BCM4306 wireless card.

David didn't said 1500 all the way to 9000, he said that some drivers
support 9000, some don't, lemme check for ya which one does...

drivers/net/8139cp.c: max is 4096
drivers/net/acenic.c: 9000

just do a:

vi $(find drivers/net | xargs grep -l change_mtu)

and check the rest :-)

- Arnaldo