sun
   microsystems              Systems Architecture Committee

_________________________________________________________________

Subject:       shmux

Submitted by:  Lily Li

File:          PSARC/2009/150/opinion.ms

Date:          March 11th, 2009

Committee:     James D. Carlson, Kais Belgaied,  Mark  Carl-
               son,  Richard  Matthews, Darren Moffat, Glenn
               Skinner.

Product Approval Committee:

               Solaris PAC
               solaris-pac@sun.com

1.  Summary

This project proposes to integrate "shmux," an  open  source
utility that automates remote shell access, into Solaris and
OpenSolaris.

2.  Decision & Precedence Information

The project is approved as specified in reference  [1],  but
as  modified  by  the  required  technical changes listed in
Appendix A below.

The project may deliver in a patch/micro release of  Solaris
or OpenSolaris via the SFW consolidation.

3.  Interfaces

The project exports the following interfaces.

_________________________________________________________
|                  Interfaces Exported                  |
|______________|________________|_______________________|
|Interface     |  Classification|  Comments             |
|______________|________________|_______________________|
|/usr/bin/shmux|  Uncommitted   |  executable location  |
|shmux         |  Uncommitted   |  command line syntax  |
|commands      |  Volatile      |  interactive mode     |
|exit codes    |  Uncommitted   |                       |
|SHMUX_*       |  Uncommitted   |  environment variables|
|SUNWshmux     |  Uncommitted   |  package name         |
|______________|________________|_______________________|

PSARC/2009/150               Copyright 2009 Sun Microsystems

                           - 2 -

_________________________________________________________
|                  Interfaces Exported                  |
|______________|________________|_______________________|
|Interface     |  Classification|  Comments             |
|______________|________________|_______________________|
|______________|________________|_______________________|

4.  Opinion

The only substantive issue discussed during ARC  review  was
in  regard  to the -p and -P command line options, described
in reference [2].  These  options  are  designed  to  invoke
fping to check for server liveness before attempting connec-
tion.

This design leads to a list of problems.   First,  fping  on
Solaris  cannot  be  used  by  an  ordinary user, because it
requires elevated privileges to use raw sockets.  This means
that  it would not work right by default on Solaris or Open-
Solaris,  even  though  the  same  option  presently   works
correctly on Linux.

This issue led to a discussion of other problems related  to
this  design.   The  success of "ping" (ICMP) bears no rela-
tionship to the success  of  a  subsequent  TCP  connection.
They are different protocols.  Moreover, one can easily test
the success of TCP connections by using non-blocking sockets
and  short  timers.   The  project team did not dispute this
contention and this discussion led to the  technical  change
required, described below.

An ARC member suggested on the mailing list that  advice  be
sent  to  the  management teams regarding the cost of "free"
software, which led to the advice given in section 6 below.

5.  Minority Opinion(s)

None

6.  Advisory Information

The Solaris PAC and the management of project teams involved
in  importing  open  source software are reminded that "free
software" is sometimes "free" in the same  way  a  puppy  is
free.  It may not be sufficient to import the package as-is.

7.  Appendices

7.1.  Appendix A: Technical Changes Required

     1.   The  utility  must  be  modified  to  remove   its

PSARC/2009/150               Copyright 2009 Sun Microsystems

                           - 3 -

          dependence  on  fping  and should (to preserve the
          user interface) re-use the existing "-p" and  "-P"
          options  to  control  the  behavior  of connect(),
          using non-blocking sockets, poll/select for write,
          and short timers as necessary.

7.2.  Appendix B: Technical Changes Advised

None

7.3.  Appendix C: Reference Material

Unless stated otherwise, path names are relative to the case
directory PSARC/2009/150.

1.   Project proposal
     File:  proposal.txt

2.   shmux draft man page
     File:  materials/shmux.1.txt

PSARC/2009/150               Copyright 2009 Sun Microsystems