cvs commit: src/sys/contrib/pf/net pf.c

Daniel Hartmeier dhartmei at
Thu Aug 23 02:30:59 PDT 2007

dhartmei    2007-08-23 09:30:58 UTC

  FreeBSD src repository

  Modified files:
    sys/contrib/pf/net   pf.c 
  When checking the sequence number of a TCP header embedded in an
  ICMP error message, do not access th_flags. The field is beyond
  the first eight bytes of the header that are required to be present
  and were pulled up in the mbuf.
  A random value of th_flags can have TH_SYN set, which made the
  sequence number comparison not apply the window scaling factor,
  which led to legitimate ICMP(v6) packets getting blocked with
  "BAD ICMP" debug log messages (if enabled with pfctl -xm), thus
  breaking PMTU discovery.
  Triggering the bug requires TCP window scaling to be enabled
  (sysctl net.inet.tcp.rfc1323, enabled by default) on both end-
  points of the TCP connection. Large scaling factors increase
  the probability of triggering the bug.
  PR:             kern/115413: [ipv6] ipv6 pmtu not working
  Tested by:      Jacek Zapala
  Reviewed by:    mlaier
  Approved by:    re (kensmith)
  Revision  Changes    Path
  1.46      +1 -2      src/sys/contrib/pf/net/pf.c

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