From owner-freebsd-net  Fri Jan 12  9:58:10 2001
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Date: Fri, 12 Jan 2001 13:08:32 -0500
From: Larry Baird <lab@gta.com>
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To: freebsd-net@freebsd.org
Subject: Strange source address problem
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Hopefully somebody can shed some light in helping me to understand 
something I am seeing on a 4.2 box.  I am experimenting with a daemon 
that implements something very close to the VRRP (Virtual Router 
Redundancy Protocol).   The VRRP portion of the daemon works correctly.  
The problem I am having has to do with the source IP address after a
host
has transitioned from "slave" to "master" mode.  

The problem can be illustrated on a standard 4.2 system not
running the VRRP daemon by the following command line actions:

Script started on Fri Jan 12 12:42:35 2001
sukebe# ifconfig xl0 inet 192.168.23.85
sukebe#
sukebe# ifconfig xl0
xl0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        inet6 fe80::260:8ff:feaf:2bf5%xl0 prefixlen 64 scopeid 0x1 
        inet 192.168.23.85 netmask 0xffffff00 broadcast 192.168.23.255
        ether 00:60:08:af:2b:f5 
        media: autoselect (none) status: no carrier
        supported media: autoselect 100baseTX <full-duplex> 100baseTX
10baseT/UTP <full-duplex> 10baseT/UTP 100baseTX <hw-loopback>
sukebe#
sukebe# ./getLocalIP 192.168.23.90
local = 192.168.23.85:1178
sukebe#
sukebe# ifconfig xl0 inet 192.168.23.86
sukebe#
sukebe# ifconfig xl0
xl0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        inet6 fe80::260:8ff:feaf:2bf5%xl0 prefixlen 64 scopeid 0x1 
        inet 192.168.23.86 netmask 0xffffff00 broadcast 192.168.23.255
        ether 00:60:08:af:2b:f5 
        media: autoselect (none) status: no carrier
        supported media: autoselect 100baseTX <full-duplex> 100baseTX
10baseT/UTP <full-duplex> 10baseT/UTP 100baseTX <hw-loopback>
sukebe#
sukebe# ./getLocalIP 192.168.23.90
local = 192.168.23.85:1179

^^^^ why is 192.168.23.85 still showing up?? This address should be
gone.
sukebe#
sukebe# exit

Script done on Fri Jan 12 12:44:35 2001

I have attached the source code to the getLocalIP program.  Can 
anybody explain this?  Thanks in advance for your help.


-- 
------------------------------------------------------------------------
Larry Baird                             
Global Technology Associates, Inc.  | Orlando, FL
Email: lab@gta.com                  | TEL 407-380-0220, FAX 407-380-6080
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 name="getLocalIP.c"
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 filename="getLocalIP.c"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <sys/types.h>
#include <sys/socket.h>

#include <netinet/in.h>
#include <arpa/inet.h>

int main(int argc, char *argv[])
{
    int s;

    if ( argc != 2 )
	fprintf( stderr, "USAGE: %s destIP[:port]\n", argv[0] );

    else {
	if ( (s = socket( PF_INET, SOCK_DGRAM, 0 )) < 0 )
	    perror( "Unable to create socket" );

	else {
	    struct sockaddr_in servAddr;
	    short              port = 7;
	    char              *p;

	    if ((p = strchr(argv[1], ':')) != NULL) {
		port = atoi(p + 1);
		*p = 0;
	    }

	    bzero(&servAddr, sizeof(servAddr));

	    servAddr.sin_family = AF_INET;
	    servAddr.sin_port   = htons( port );

	    if ( ! inet_aton( argv[1], &servAddr.sin_addr ) )
		fprintf( stderr, "IP address invalid.\n" );
	    else {
		if ( connect( s,
			      (struct sockaddr *)&servAddr,
			      sizeof(servAddr) ) )
		    perror( "connect() failed" );
		else {
		    struct sockaddr_in local;
		    int                local_len = sizeof(local);

		    if ( getsockname( s,
				      (struct sockaddr *)&local,
				      &local_len))
			perror( "getsockname() failed" );
		    else {
			printf( "local = %s:%d\n",
				inet_ntoa(local.sin_addr),
				ntohs(local.sin_port));
			exit( 0 );
		    }
		}
	    }

	    close(s);
	}
    }

    exit( 1 );
}

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