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From: Gleb Smirnoff <glebius@FreeBSD.org>
Date: Thu, 11 Aug 2005 08:25:48 +0000 (UTC)
To: src-committers@FreeBSD.org, cvs-src@FreeBSD.org, cvs-all@FreeBSD.org
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Subject: cvs commit: src/sys/netinet if_ether.c
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glebius     2005-08-11 08:25:48 UTC

  FreeBSD src repository

  Modified files:
    sys/netinet          if_ether.c 
  Log:
  o Fix a race between three threads: output path,
    incoming ARP packet and route request adding/removing
    ARP entries. The root of the problem is that
    struct llinfo_arp was accessed without any locks.
    To close race we will use locking provided by
    rtentry, that references this llinfo_arp:
    - Make arplookup() return a locked rtentry.
    - In arpresolve() hold the lock provided by
      rt_check()/arplookup() until the end of function,
      covering all accesses to the rtentry itself and
      llinfo_arp it refers to.
    - In in_arpinput() do not drop lock provided by
      arplookup() during first part of the function.
    - Simplify logic in the first part of in_arpinput(),
      removing one level of indentation.
    - In the second part of in_arpinput() hold rtentry
      lock while copying address.
  
  o Fix a condition when route entry is destroyed, while
    another thread is contested on its lock:
    - When storing a pointer to rtentry in llinfo_arp list,
      always add a reference to this rtentry, to prevent
      rtentry being destroyed via RTM_DELETE request.
    - Remove this reference when removing entry from
      llinfo_arp list.
  
  o Further cleanup of arptimer():
    - Inline arptfree() into arptimer().
    - Use official queue(3) way to pass LIST.
    - Hold rtentry lock while reading its structure.
    - Do not check that sdl_family is AF_LINK, but
      assert this.
  
  Reviewed by:    sam
  Stress test:    http://www.holm.cc/stress/log/cons141.html
  Stress test:    http://people.freebsd.org/~pho/stress/log/cons144.html
  
  Revision  Changes    Path
  1.139     +183 -157  src/sys/netinet/if_ether.c