09-23-2011
Port redirection with exclusions
Hi folks,
I have an application that is acting up. I have another machine with a replacement application on it but because of the naming structure clients are using I cannot change the name to the replacement machine as it is also used to access other applications.
The host OS is Centos 5.6 and iptables is running. I'm familiar with setting it up for firewall purposes but my attempts to use it for redirection thus far have ended up in lost packets.
So, say the primary server is running on 1.1.1.1 and currently accepts SMTP mail.
The secondary server is running on 1.1.1.2 and also accepts SMTP mail.
I have a backup off site mail server running on 2.2.2.2
I need to redirect all connections received on port 25 by 1.1.1.1 to port 25 on 1.1.1.2 but not redirect 2.2.2.2 (and have the ability to exclude other hosts).
I'm sure this is possible, maybe a rule that accepts port 25 from 2.2.2.2 before the rule that redirects port 25 elsewhere?
One caveat, the connections also need to appear to be coming from the original source host otherwise it will stuff up the spam filtering app. I wonder if this will be possible without some trickery at the destination box to make it accept and reply as 1.1.1.1 without actually having the IP..hmm
For reference, there is no NAT involved. All IPs are Internet routable even though 1.1.1.1 and 1.1.1.2 are physically together.
It is probably fairly simple, I tried pulling what I've already tried from .bash_history but I think I did it from a screen session that hasn't kept it.
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LEARN ABOUT DEBIAN
pvmfaddhost
ADDHOSTS(3PVM) PVM Version 3.4 ADDHOSTS(3PVM)
NAME
pvm_addhosts - Add hosts to the virtual machine.
SYNOPSIS
C int info = pvm_addhosts( char **hosts, int nhost, int *infos )
Fortran call pvmfaddhost( host, info )
PARAMETERS
hosts An array of strings naming the hosts to be added. Pvmd must already be installed and the user must have an account on the speci-
fied hosts.
nhost Integer specifying the length of array hosts.
infos Integer array of length nhost which returns the status for each host. Values less than zero indicate an error, while positive val-
ues are TIDs of the new hosts.
host Character string naming the host to be added.
info Integer status code returned by the routine. Values less than nhost indicate partial failure, and values less than 1 indicate
total failure.
DESCRIPTION
The routine pvm_addhosts adds the computers named in hosts to the configuration of computers making up the virtual machine. The names
should have the same syntax as lines of a pvmd hostfile (see man page for pvmd3): A hostname followed by options of the form xx=y.
If pvm_addhosts is successful, info will be equal to nhost. Partial success is indicated by 0 < info < nhost, and total failure by info <
1. The array infos can be checked to determine which host caused the error.
The Fortran routine pvmfaddhost adds a single host to the configuration with each call. info will be 1 if successful or < 0 if error.
The status of hosts can be requested by the application using pvm_mstat and pvm_config. If a host fails it will be automatically deleted
from the configuration. Using pvm_addhosts a replacement host can be added by the application, however it is the responsibility of the
application developer to make his application tolerant of host failure. Another use of this feature would be to add more hosts as they
become available, for example on a weekend, or if the application dynamically determines it could use more computational power.
EXAMPLES
C:
static char *hosts[] = {
"sparky",
"thud.cs.utk.edu",
};
info = pvm_addhosts( hosts, 2, infos );
Fortran:
CALL PVMFADDHOST( 'azure', INFO )
ERRORS
The following error conditions can be returned by pvm_addhosts:
PvmBadParam
giving an invalid argument value.
PvmAlready
another task is currently adding hosts.
PvmSysErr
local pvmd is not responding.
and in the infos vector:
PvmBadParam
bad hostname syntax.
PvmNoHost
no such host.
PvmCantStart
failed to start pvmd on host.
PvmDupHost
host already configured.
PvmBadVersion
pvmd protocol versions don't match.
PvmOutOfRes
PVM has run out of system resources.
SEE ALSO
pvm_pvmd3(1PVM), pvm_delhosts(3PVM), pvm_start_pvmd(3PVM), pvm_config(3PVM), pvm_mstat(3PVM)
22 February, 1994 ADDHOSTS(3PVM)