cvs commit: src/sys/netinet udp_usrreq.c

[Robert Watson]

rwatson     2004-11-22 15:17:08 UTC

  FreeBSD src repository

  Modified files:        (Branch: RELENG_5)
    sys/netinet          udp_usrreq.c 
  Log:
  Merge udp_usrreq.c:1.168 from HEAD to RELENG_5:
  
    date: 2004/11/04 01:25:23;  author: rwatson;  state: Exp;  lines: +24 -57
    Until this change, the UDP input code used global variables udp_in,
    udp_in6, and udp_ip6 to pass socket address state between udp_input(),
    udp_append(), and soappendaddr_locked().  While fine in the default
    configuration, when running with multiple netisrs or direct ithread
    dispatch, this can result in races wherein user processes using
    recvmsg() get back the wrong source IP/port.  To correct this and
    related races:
  
    - Eliminate udp_ip6, which is believed to be generated but then never
      used.  Eliminate ip_2_ip6_hdr() as it is now unneeded.
  
    - Eliminate setting, testing, and existence of 'init' status fields
      for the IPv6 structures.  While with multiple UDP delivery this
      could lead to amortization of IPv4 -> IPv6 conversion when
      delivering an IPv4 UDP packet to an IPv6 socket, it added
      substantial complexity and side effects.
  
    - Move global structures into the stack, declaring udp_in in
      udp_input(), and udp_in6 in udp_append() to be used if a conversion
      is required.  Pass &udp_in into udp_append().
  
    - Re-annotate comments to reflect updates.
  
    With this change, UDP appears to operate correctly in the presence of
    substantial inbound processing parallelism.  This solution avoids
    introducing additional synchronization, but does increase the
    potential stack depth.
  
    Discovered by:  kris (Bug Magnet)
    MFC after:      3 weeks
  
  Note that this bug does not effect the default configuration, only systems
  running with net.isr.enable=1, or with modified network stacks to increase
  parallelism.
  
  Revision   Changes    Path
  1.162.2.4  +24 -57    src/sys/netinet/udp_usrreq.c