[Bug 238796] ipfilter: failure to detect the same rules when arguments ordered differently

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=238796

--- Comment #40 from commit-hook at freebsd.org ---
A commit references this bug:

Author: cy
Date: Sun Aug 11 23:54:49 UTC 2019
New revision: 350880
URL: https://svnweb.freebsd.org/changeset/base/350880

Log:
  r272552 applied the patch from ipfilter upstream fil.c r1.129 to fix
  broken ipfilter rule matches (upstream bug #554). The upstream patch
  was incomplete, it resolved all but one rule compare issue. The issue
  fixed here is when "{to, reply-to, dup-to} interface" are used in
  conjuncion with "on interface". The match was only made if the on keyword
  was specified in the same order in each case referencing the same rule.
  This commit fixes this.

  The reason for this is that interface name strings and comment keyword
  comments are stored in a a variable length field starting at fr_names
  in the frentry struct. These strings are placed into this variable length
  in the order they are encountered by ipf_y.y and indexed through index
  pointers in fr_ifnames, fr_comment or one of the frdest struct fd_name
  fields. (Three frdest structs are within frentry.) Order matters and
  this patch takes this into account.

  While in here it was discovered that though ipfilter is designed to
  support multiple interface specifiations per rule (up to four), this
  undocumented (the man page makes no mention of it) feature does not work.
  A todo is to fix the multiple interfaces feature at a later date. To
  understand the design decision as to why only four were intended, it is
  suspected that the decision was made because Sun workstations and PCs
  rarely if ever exceeded four NICs at the time, this is not true in 2019.

  PR:           238796
  Reported by:  WHR <msl0000023508 at gmail.com>
  MFC after:    2 weeks

Changes:
  head/sys/contrib/ipfilter/netinet/fil.c
  head/sys/contrib/ipfilter/netinet/ip_fil.h

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