ITEM: FM5923L

Detail description of socket/ports used by sysback

Question:

Env:
  AIX 4.2.1
  RISC J30
  sysback.obj 3.3.3.x and sysback.rte 4.1.x

Problem:

  Please describe in detail the socket/ports that are used 
  during a sysback client/server backup and/or restore.  We are 
  trying to configure sysback on an IBM Firewall v3 system and 
  the socket numbers that are being used seem to randomize below
  port 1023.  We know that 1239, 1022 and 1023 are being used, 
  but the randomly generated ports fluctuate wildly, making it 
  generally impossible to create secure firewall filter rules 
  to use in the connection/service.

  Alternatively, please specify firewall filter rules that are 
  known to work securely and reliably with sysback client/server.
  The firewall is a sysback client to sysback server on the 
  secure intranet side of the firewall.

Action Taken:

  When the cfgremsvs command is run it does this:
  it will add an entry into the /etc/servers file
  sbnet           1239/tcp         \# Sysback Remote Services

  It will also put an entry in the inetd.conf file
  sbnet   stream  tcp   nowait  root  /usr/sbin/sbserver sbserver

  It creates a user sbnet.  The user will not be able to login 
  using that user.

  The port used is 1239 and it is in a listen state.  When the 
  sbclient is run from the client system
  sbclient \ \

Example:
  sbclient mars echo
  It will then open up two sockets to communicate with the client
  one for standard out and other for standard error.

  Sysback uses two ports, one for standard output and one for 
  standard error.  The first will be IPPORT_RESERVED - 1, and 
  the second will be  IPPORT_RESERVED - 2. If either port is 
  already in use by another application, the number will be 
  decremented up to IPPORT_RESERVED / 2 until
  successful. If all ports between 
  IPPORT_RESERVED / 2 and IPPORT_RESERVED -1 are in use, the 
  connection will fail with the message "all ports in use".

  IPPORT_RESERVED is defined in the /usr/include/netinet/in.h 
  file and is set to 1024. Therefore, the ports will be 1023 
  and 1022 by default. If these ports are in use they may go as 
  low as 514 and 513, since anything under 512 is reserved.




Support Line: Detail description of socket/ports used by sysback ITEM: FM5923L

Dated: April 1998 Category: N/A

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