From mboxrd@z Thu Jan 1 00:00:00 1970 From: Larry Finger Subject: Re: softmac mtu Date: Sat, 23 Sep 2006 16:59:48 -0500 Message-ID: <4515AE54.4040403@lwfinger.net> References: <4515A9BF.90709@lwfinger.net> <20060923.144757.78710420.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: castet.matthieu@free.fr, netdev@vger.kernel.org Return-path: Received: from mtiwmhc12.worldnet.att.net ([204.127.131.116]:64502 "EHLO mtiwmhc12.worldnet.att.net") by vger.kernel.org with ESMTP id S1750718AbWIWV7v (ORCPT ); Sat, 23 Sep 2006 17:59:51 -0400 To: David Miller In-Reply-To: <20060923.144757.78710420.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org David Miller wrote: > From: Larry Finger > Date: Sat, 23 Sep 2006 16:40:15 -0500 > >> 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. Larry