cvs commit: src/sys/netinet udp_usrreq.c

[Robert Watson]

rwatson     2004-11-04 01:25:23 UTC

  FreeBSD src repository

  Modified files:
    sys/netinet          udp_usrreq.c 
  Log:
  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 file 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
  
  Revision  Changes    Path
  1.168     +24 -57    src/sys/netinet/udp_usrreq.c