I'm trying to set the MTU size on my Via Velocity 6122 Gbit adapter from the default of 1500 down to 1492, but I keep getting this error:
[root@osprey ~]# ifconfig eth0 mtu 1492 SIOCSIFMTU: Invalid argument
Turns out that via-velocity.h defines the minimum MTU at 1500 bytes.
#define VELOCITY_MIN_MTU (1514-14) #define VELOCITY_MAX_MTU (9000)
And via-velocity.c enforces the limit.
if ((new_mtu < VELOCITY_MIN_MTU) || new_mtu > (VELOCITY_MAX_MTU)) { VELOCITY_PRT(MSG_LEVEL_ERR, KERN_NOTICE "%s: Invalid MTU.\n", vptr->dev->name); return -EINVAL; }
This is an Abit AV8 motherboard with an Athlon64 3000+ cpu running 2.6.16-1.2111_FC5 x86_64.
Can someone explain why the driver might constrain the NIC to a minimum MTU size of 1500?
Thanks, Jay
On Sun, May 21, 2006 at 02:43:24PM -0500, Jay Cliburn wrote:
I'm trying to set the MTU size on my Via Velocity 6122 Gbit adapter from the default of 1500 down to 1492, but I keep getting this error:
[root@osprey ~]# ifconfig eth0 mtu 1492 SIOCSIFMTU: Invalid argument
Turns out that via-velocity.h defines the minimum MTU at 1500 bytes.
#define VELOCITY_MIN_MTU (1514-14) #define VELOCITY_MAX_MTU (9000)
And via-velocity.c enforces the limit.
if ((new_mtu < VELOCITY_MIN_MTU) || new_mtu > (VELOCITY_MAX_MTU)) { VELOCITY_PRT(MSG_LEVEL_ERR, KERN_NOTICE "%s: Invalid MTU.\n", vptr->dev->name); return -EINVAL; }
This is an Abit AV8 motherboard with an Athlon64 3000+ cpu running 2.6.16-1.2111_FC5 x86_64.
Can someone explain why the driver might constrain the NIC to a minimum MTU size of 1500?
Asking the developers on netdev@vger.kernel.org is going to get you the answer faster than asking here.
Dave
On Sun, 2006-05-21 at 21:57 -0500, Jay Cliburn wrote:
On Sun, 2006-05-21 at 15:48 -0400, Dave Jones wrote:
Can someone explain why the driver might constrain the NIC to a minimum MTU size of 1500?
Asking the developers on netdev@vger.kernel.org is going to get you the answer faster than asking here.
There is a patch: http://bugme.osdl.org/show_bug.cgi?id=4001
Matt
Matt Davey Do not seek to follow in the footsteps of the men of old; mcdavey@mrao.cam.ac.uk seek what they sought. -- Basho
On Mon, May 22, 2006 at 10:06:22AM +0100, Matt Davey wrote:
On Sun, 2006-05-21 at 21:57 -0500, Jay Cliburn wrote:
On Sun, 2006-05-21 at 15:48 -0400, Dave Jones wrote:
Can someone explain why the driver might constrain the NIC to a minimum MTU size of 1500?
Asking the developers on netdev@vger.kernel.org is going to get you the answer faster than asking here.
There is a patch: http://bugme.osdl.org/show_bug.cgi?id=4001
I think this may be a separate issue.
That last comment on 2006-03-01 mentions that it was included in mainline. The patch referenced in the other bug (http://bugzilla.kernel.org/show_bug.cgi?id=4380) does seem to be included in the kernel Jay was running (I just doublechecked the Fedora sources for that version).
Dave
On Mon, 2006-05-22 at 08:46 -0400, Dave Jones wrote:
On Mon, May 22, 2006 at 10:06:22AM +0100, Matt Davey wrote:
On Sun, 2006-05-21 at 21:57 -0500, Jay Cliburn wrote:
On Sun, 2006-05-21 at 15:48 -0400, Dave Jones wrote:
Can someone explain why the driver might constrain the NIC to a minimum MTU size of 1500?
Asking the developers on netdev@vger.kernel.org is going to get you the answer faster than asking here.
There is a patch: http://bugme.osdl.org/show_bug.cgi?id=4001
I think this may be a separate issue.
That last comment on 2006-03-01 mentions that it was included in mainline. The patch referenced in the other bug (http://bugzilla.kernel.org/show_bug.cgi?id=4380) does seem to be included in the kernel Jay was running (I just doublechecked the Fedora sources for that version).
There appear to be two issues in the referenced bug:
(1) VELOCITY_MIN_MTU is hardcoded at 1500 bytes in via-velocity.h, and (2) An earlier version of the via-velocity driver couldn't handle on-the-fly MTU changes.
Number (2) was resolved with a patch. Number (1) was not. I intend to submit a patch to kernel.org, but first, can someone confirm that the proper way to alter MTU size is:
ifconfig <interface> mtu <size> service network restart
I can't get it to work unless I bounce the network service after making the MTU change. I just need to know if that's normal.
Thanks, Jay
On Mon, 2006-05-22 at 19:51 -0500, Jay Cliburn wrote:
can someone confirm that the proper way to alter MTU size is:
ifconfig <interface> mtu <size> service network restart
I can't get it to work unless I bounce the network service after making the MTU change. I just need to know if that's normal.
Apologies for responding to my own post, but just to clarify, "ifconfig eth0 mtu xxx" indeed changes mtu to xxx as displayed by the "ifconfig eth0" command, but ICMP pings to anywhere are unresponsive until after I bounce the network service. That's what I need to confirm as either correct or aberrant behavior.
Thanks.