How to inject fullsize 802.1q-tagged frame through BPF?
Eugene Perevyazko
john at dnepro.net
Thu May 15 16:08:16 UTC 2008
Hello,
I have an ethernet interface with several vlans on it (FreeBSD 6.2-RELEASE #0).
My program opens BPF on the parent device, receives tagged frames and responds
by writing tagged frame to the BPF fd.
It all works good, until size of response frame w/o tag becomes larger than
1496 bytes (1500 with tag inserted) - mtu of parent device.i
I'm a bit confused as mtu is 1500 on both vlanN and it's parent fxp0.
I've tried to "ifconfig fxp0 mtu 1504" to make room for vlan tag, but
the response is
ifconfig: ioctl (set mtu): Invalid argument
Trying "ifconfig fxp0 -vlanmtu" also makes no difference.
Is there a way to inject full-mtu vlan-tagged frame through BPF on parent
device?
I'd like not to open several tenths of BPFs for each vlanN if it's possible.
I've tried on bge also with same results, so that is not connected with fxp
driver.
Eugene Perevyazko
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