jumbo frame support in bge(4) for BCM5704

[David Newman]

8.0-RELEASE amd64, Tyan S2882-D motherboard, Broadcom BCM5704C gigabit
Ethernet transceivers

Looking for clues on enabling jumbo support on BCM5704 chips.

The bge(4) manpage claims this interface supports jumbo frames, as does
Broadcom's data sheet.

However, 'ifconfig bge0 mtu 9000' returns an error, as does 'ifconfig
bge0 mtu 1500':

ifconfig: ioctl (set mtu): Invalid argument

Also, this thread claims the manpage anddata sheet are in error and that
jumbos aren't supported:

http://lists.freebsd.org/pipermail/freebsd-net/2006-June/010866.html

The Linux tg3 driver for this chip does support jumbos up to 9000 bytes
but that doesn't necessarily answer whether the hardware can get there.

Thanks in advance for any clues on enabling jumbos on this system.

dn