On Tue, 2006-Sep-19 15:35:06 -0400, Jung-uk Kim wrote: [VLAN tagging] >Why don't we just fake it up from ether_input() and pass it to >BPF_MTAP() instead of 'teaching' bpf? I think it is more logical >thing to do.
As Andre points out, this negates the benefit of IFCAP_VLAN_HWTAGGING. In addition, the code necessary to correctly re-insert the VLAN tag (to provide a fully valid mbuf chain for further processing) will be larger and slower than the code necessary to kludge a mbuf that is adequate for bpf_filter(). bpf_mtap2() provides an example of kludging an mbuf header to allow data to be pre-pended. The code to kludge up the VLAN tag insertion would be similar (though somewhat more complex). Overall, I believe this approach is probably preferable to just disabling hardware VLAN tagging if there is a bpf filter. -- Peter Jeremy
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