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SubjectRe: dhcp-based netboot over jumbo-frame network?
Rick Jones wrote:
> Chris Friesen wrote:

>> We have an existing system that loads a bare kernel using tftp, then
>> mounts a rootfs via NFS. The wrinkle is that this is on a jumbo-frame
>> enabled network, so somehow the MTU needs to be set before mounting the
>> rootfs.
>
> Why? Is the NFS mount not TCP? If it is TCP, then the TCP MSS exchange will
> provide you cover as it will (should) cause TCP in the NFS server to segment to
> the MSS option your system with the then-smaller MTU sends.
>
> I would think that only if the NFS mount is UDP that you would have a problem
> with the system initially booting with a small MTU.

Currently it uses the default, which is udp. I might be able to get
them to try TCP. Thanks for the suggestion.

>> In a previous version we patched ipconfig.c to support the DHCP option
>> to specify the MTU value, but I'm wondering about the "proper" way to do
>> this on current kernels.
>
> Was the change submitted to upstream and rejected?

The change was submitted (not by us) back in the 2.6.10 timeframe, and
was rejected with the suggestion to use initramfs.

Chris


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