Dear SCO Customer,

Support Level Supplement (SLS) PTF7013E, the UnixWare 7 libsocket Patch,
contains a modified socket library and sockmod driver which corrects 
problems with TCP and UNIX domain sockets, UDP performance, and compilation 
of programs that link libsocket when profiling has been turned on.  The 
following list further describes these problems and how this SLS resolves 
them:
 
 - When a TCP socket is set as non-blocking with the O_NDELAY flag, a
   write to the socket (using write(2), send(3sock), sendto(3sock), or
   sendmsg(3sock)) returns the actual number of bytes requested even if
   the socket is blocked and unable to transmit the data.  This SLS
   modifies the sockets implementation to return only the number of 
   bytes actually transmitted when writing to a TCP socket on which 
   O_NDELAY has been set.  A value of 0 is returned if no bytes could be
   transmitted because the socket was blocked.  The behavior of setting
   O_NONBLOCK on a TCP socket is unaffected.  In this case, a value of -1
   is returned and EWOULDBLOCK is set in errno if no bytes could be
   transmitted because the socket was blocked.

 - When one side of a TCP socket connection performs a write followed 
   by a shutdown(3sock), the other side performing a read may incorrectly
   fail with the error EPROTO.  This SLS modifies the sockets
   implementation to prevent this behavior.

 - Data sent by a client immediately before it calls shutdown(3sock) may
   not be received by the server.  This SLS modifies the sockets
   implementation so that outstanding data can be read from a socket if
   the remote side has shut down the connection.  

 - If a socket library call such as select(3sock) is interrupted by a
   signal such as SIGCHLD for which a restartable handler routine has
   been declared, it may incorrectly fail with the error EPROTO.  This
   SLS modifies the sockets implementation so that restartable signals
   are handled correctly within socket routines.

 - A TCP socket connection that makes heavy use of both send(3sock)
   and recv(3sock)-type calls may incorrectly fail with the error EPROTO.
   This SLS modifies the sockets implementation so that heavy use of
   send- and recv-type calls does not cause this error.

 - A UNIX domain socket, on which FASYNC has been set in order to use
   signal-driven I/O, does not generate SIGPOLL when the other end of
   the socket is closed.  This SLS modifies the sockets implementation
   so that SIGPOLL is generated.

 - Occasional "broken pipe" errors are experienced by a web browser
   when it loses its connection to cgi-bin programs that are being run
   on a remote web server.  This SLS modifies the sockets implementation
   to prevent these errors.

 - This SLS modifies the sockets implementation to prevent a panic that
   could occur on a multiprocessor system when using TCP sockets over
   PPP connections. 

 - The TCP stack does not handle out-of-band (MSG_OOB) data correctly.
   A TCP application, such as the telnetd(1Mtcp) server, that uses
   out-of-band data to handle user interrupts (for example, those
   generated by pressing <Del> in the telnet client) will hang.  This
   SLS corrects this behavior.

 - The performance of UDP, which had degraded when compared to previous 
   releases, has been improved.

 - Applications written in C that use the socket library dump core when
   executed if they have been compiled with profiling turned on.  This
   SLS corrects this behavior.
 

SLS PTF7013E contains these files:

        /etc/conf/pack.d/sockmod/Driver_atup.o
        /etc/conf/pack.d/sockmod/Driver_mp.o
        /etc/conf/pack.d/sockmod/space.c
        /usr/lib/libsocket.so
        /usr/lib/libsocket.so.1
        /usr/lib/libsocket.so.2

Notes on the fixes included in this SLS can be found on the FTP server or,
after its installation, in:

    /var/sadm/pkg/ptf7013/install/ptf7013.txt


Software Notes and Recommendations
----------------------------------

SLS PTF7013E should only be installed on: 

    UnixWare 7 with the UnixWare 7 Release Supplement (uw7rs) applied

To find out what release your system is running, use the command:

    uname -sv

The command will return "UnixWare 7" if this release is installed.

To determine if the SCO UnixWare 7 Release Supplement is installed,
run the command:

    pkginfo | grep uw7rs

If the Release Supplement is installed, this command will return
"patch uw7rs uw7rs - SCO UnixWare 7 Release Supplement."

Testing of the modified software contained in this SLS has been
conducted only to the extent necessary to confirm that it resolves
the problem(s) stated above.  Such testing consists of re-creating
the problem conditions (typically in an SCO test laboratory) and
verifying that the problem no longer occurs.  No other testing of
this software has been done.


Hardware Notes and Recommendations
----------------------------------

This SLS is intended for i486, Pentium, Pentium Pro, Pentium II,
and compatible CPUs.


Installation Instructions
-------------------------

1. Download the ptf7013e.Z and ptf7013e.txt files to the /tmp directory 
   on your machine.

2. As root, uncompress the file and add the SLS to your system using 
   these commands:

        $ su
        # uncompress /tmp/ptf7013e.Z
        # pkgadd -d /tmp/ptf7013e

3. Shut down and reboot the system after installing this SLS.

Note: A system reboot is required following installation of this SLS
for the kernel sections to take effect.  However, if you have not
already installed any other SLS that you need, you should do so
before rebooting.


Removal Instructions
--------------------

1. As root, remove the SLS using these commands:

        # pkgrm ptf7013

2. Shut down and reboot the system after removing this SLS.


If you have questions regarding this SLS, or the product on which 
it is installed, please contact your software supplier.

We appreciate your business.

SCO Support Services