[Bug 222768] ipfw can't distinguish an inbound packets forwarded via if_bridge

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=222768

            Bug ID: 222768
           Summary: ipfw can't distinguish an inbound packets forwarded
                    via if_bridge
           Product: Base System
           Version: 11.1-RELEASE
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Many People
          Priority: ---
         Component: kern
          Assignee: freebsd-bugs at FreeBSD.org
          Reporter: alex at zagrebin.ru

Created attachment 186898
  --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=186898&action=edit
patch

By default (when net.link.bridge.pfil_bridge=1), the packet, forwarded via
if_bridge, has to be processed by ipfw 4 times. Suppose such configuration:

em0 <-> bridge0 <-> em1

ipfw will process packet, forwarded from em0 to em1, in the following sequence:
in[em0], in[bridge0], out[bridge0], out[em1].

We can expect, that inbound packets can be matched with the following ipfw rule
options:

in[em0]     - 'in recv em0' or 'in via em0'
in[bridge0] - 'in via bridge0'

For example,

ipfw add 1 count ip from any to any in via em0
ipfw add 2 count ip from any to any in via bridge0

but this doesn't work as expected: each single packet matches 2 times to the
rule 1 and not matches to the rule 2 at all.

The reason in the following: despite that if_bridge sends information about
corresponding interface to the pfil_run_hooks(), the ipfw doesn't uses it while
processing inbound packets.

The attached patch fixes issue:
If the interface on which ipfw processes packet does not match an 'received'
interface, then this interface saved and used later in the processing of 'via'
rule option.

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