New em driver breaks jumbo frames

[Craig Boston]

Don't have much time right now, but wanted to report that the new em
driver in -STABLE breaks jumbo frame support for me.  With it in the
kernel and this card:

em1: <Intel(R) PRO/1000 Network Connection Version - 6.2.9> port 0xe8c0-0xe8ff mem 0xfe180000-0xfe19ffff irq 18 at device 12.0 on pci2

I'm unable to send an ethernet frame bigger than 2034 bytes, no matter
what the mtu is set to.  No errors, no kernel messages, it just doesn't
go out.  tcpdump on both local and remote side show nothing at all.

Reverting to the previous driver fixed it.

Craig