cvs commit: src/sys/netinet tcp_usrreq.c

Robert Watson rwatson at
Wed Jan 23 15:40:23 PST 2008

rwatson     2008-01-23 23:40:22 UTC

  FreeBSD src repository

  Modified files:        (Branch: RELENG_7)
    sys/netinet          tcp_usrreq.c 
  Merge tcp_usrreq.c:1.167 from HEAD to RELENG_7:
    tcp_usrreq.c:1.313 removed tcbinfo locking from tcp_usr_accept(), which
    while in principle a good idea, opened us up to a race inherrent to
    the syncache's direct insertion of incoming TCP connections into the
    "completed connection" listen queue, as it transpires that the socket
    is inserted before the inpcb is fully filled in by syncache_expand().
    The bug manifested with the occasional returning of in the
    address returned by the accept() system call, which occurred if accept
    managed to execute tcp_usr_accept() before syncache_expand() had copied
    the endpoint addresses into inpcb connection state.
    Re-add tcbinfo locking around the address copyout, which has the effect
    of delaying the copy until syncache_expand() has finished running, as
    it is run while the tcbinfo lock is held.  This is undesirable in that
    it increases contention on tcbinfo further, but a more significant
    change will be required to how the syncache inserts new sockets in
    order to fix this and keep more granular locking here.  In particular,
    either more state needs to be passed into sonewconn() so that
    pru_attach() can fill in the fields *before* the socket is inserted, or
    the socket needs to be inserted in the incomplete connection queue
    until it is actually ready to be used.
    Reported by:    glebius (and kris)
    Tested by:      glebius
  Approved:       re (kensmith)
  Revision   Changes    Path  +2 -0      src/sys/netinet/tcp_usrreq.c

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