[Xen-devel] [PATCH] Baby giant / jumbo frames

[Ben McKeegan <ben.mckeegan@xxxxxxxxx>]

Hi,

Here's a patch against XenLinux from 2.0.7 that allows you to use baby
giant frames over vif's.

I've only done minimal testing on it but it should work with MTU's of
up to 3000.  The 3000 limit was arbitrarily chosen due to 4k pagesize
and because I'm not sufficiently knowledgeable about Xen's
architecture to work out exactly how much headroom is needed.  For my
requirements (layer 2 tunnelling) I'm never going to need an MTU of
more than 1600 so I've left this as an exercise for the reader. :-)

Note on bridging:  there seems to be a misconception by some that the
linux bridging code doesn't support jumbo frames.  For the record this
is not true, but it won't allow you to configure an MTU greater than
the smallest MTU on a bridge port.  (If there are no bridge ports the
maximum MTU is 1500.)   The trick is to configure the jumbo MTU on
each member of the bridge first before configuring it on the bridge
itself.

Regards,
Ben.

Attachment: baby-giant-mtu.diff
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