Wed 29 Jul 2009 09:04:49 AM UTC, comment #3:
> The packet delivered from gnumach should have the packet header. NPF returns the packet_header and pfinet always assumes that the packet from gnumach has the packet_header.
OK, I understand that, and it is fine, but is there a specific reason to send package_header to user-space? (That is, if it's not required, then we should perhaps change pfinet and net_filter to not handle it?) If I understand the code correctly, packets that go from pfinet to the kernel to be sent out, do not contain the packet_header, but packets that go from the kernel to pfinet do contain the packet_header. Why this asymmetry? Perhaps I fail to understand what this packet_header is actually good for. (All that is unrelated to this bug report, of course, but while we're at it...)
> For your first question, the return value of net_do_filter is boolean, i.e., it can only be passed or not passed, but bpf_do_filter returns the size of the data that passes the filter.
OK, I see. The code could be written in a way that this is more obvious... (15 years old code, I know.)
My question also was whether net_do_filter should be changed to not handle the packet_header-part of the packet, as that is not related to the actual packet data (as I understand it), and thus should not be involved in deciding whether to allow or deny a given packet. (That's also unrelated to this bug report.)
Given the same instructions as in bug #20612, please install this patch. (And then we can think about the other issues I'm talking above.)
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Wed 29 Jul 2009 08:15:10 AM UTC, comment #2:
The packet delivered from gnumach should have the packet header. NPF returns the packet_header and pfinet always assumes that the packet from gnumach has the packet_header.
For your first question, the return value of net_do_filter is boolean, i.e., it can only be passed or not passed, but bpf_do_filter returns the size of the data that passes the filter.
bpf_do_filter(infp, net_kmsg(kmsg)->packet + sizeof(struct packet_header), count, net_kmsg(kmsg)->header, ifp->if_header_size, &hash_headp, &entp) is simply wrong because the length of the packet data passed to bpf_do_filter isn't 'count' any more.
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