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208 lines
6.5 KiB
Plaintext
208 lines
6.5 KiB
Plaintext
@(#) README.NIS 1.2 96/02/11 17:24:52
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> Problem: I have several [machines] with multiple IP addresses, and
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> when they try to connect to a daemon with tcp wrapper, they are often
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> rejected. I assume this is due to the -DPARANOID option, and depends
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> on which IP address is returned first from the nameserver for a given
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> name. This behavior seems to be random, may depend on ordering in
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> the YP host map?
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[Note: the situation described below no longer exists. Presently, my
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internet gateway uses the same IP address on all interfaces. To avoid
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confusion I have removed the old name wzv-gw.win.tue.nl from the DNS. I
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have kept the discussion below for educational reasons].
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NIS was not designed to handle multi-homed hosts. With NIS, each
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address should have its own hostname. For example, wzv-gw is my
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gateway. It has two interfaces: one connected to the local ethernet,
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the other to a serial link. In the NIS it is registered as:
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131.155.210.23 wzv-gw-ether
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131.155.12.78 wzv-gw-slip
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In principle, wzv-gw could be the official name of one of these
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interfaces, or it could be an alias for both.
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The DNS was designed to handle multi-homed hosts. In the DNS my gateway
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is registered in zone win.tue.nl, with one name that has two A records:
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wzv-gw IN A 131.155.210.23
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IN A 131.155.12.78
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And of course there are PTR records in zones 210.155.131.in-addr.arpa
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and 12.155.131.in-addr.arpa that point to wzv-gw.win.tue.nl.
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This setup does not cause any problems. You can test your name service
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with the two programs below. This is what they say on a local NIS client
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(both client and server running SunOS 4.1.3_U1):
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% gethostbyname wzv-gw
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Hostname: wzv-gw.win.tue.nl
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Aliases:
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Addresses: 131.155.210.23 131.155.12.78
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% gethostbyaddr 131.155.210.23
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Hostname: wzv-gw-ether
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Aliases:
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Addresses: 131.155.210.23
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% gethostbyaddr 131.155.12.78
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Hostname: wzv-gw-slip
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Aliases:
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Addresses: 131.155.12.78
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Things seem less confusing when seen by a NIS client in a different
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domain (both client and server running SunOS 4.1.3_U1):
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% gethostbyname wzv-gw.win.tue.nl
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Hostname: wzv-gw.win.tue.nl
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Aliases:
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Addresses: 131.155.210.23 131.155.12.78
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% gethostbyaddr 131.155.210.23
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Hostname: wzv-gw.win.tue.nl
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Aliases:
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Addresses: 131.155.12.78 131.155.210.23
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% gethostbyaddr 131.155.12.78
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Hostname: wzv-gw.win.tue.nl
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Aliases:
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Addresses: 131.155.210.23 131.155.12.78
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Alas, Solaris 2.4 still has problems. This is what I get on a Solaris
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2.4 NIS client, with a SunOS 4.1.3_U1 NIS server:
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% gethostbyname wzv-gw.win.tue.nl
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Hostname: wzv-gw.win.tue.nl
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Aliases: 131.155.210.23 wzv-gw.win.tue.nl
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Addresses: 131.155.12.78
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The tcpd source comes with a workaround for this problem. The
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workaround is ugly and is not part of the programs attached below.
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#! /bin/sh
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# This is a shell archive. Remove anything before this line, then unpack
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# it by saving it into a file and typing "sh file". To overwrite existing
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# files, type "sh file -c". You can also feed this as standard input via
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# unshar, or by typing "sh <file", e.g.. If this archive is complete, you
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# will see the following message at the end:
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# "End of shell archive."
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# Contents: gethostbyaddr.c gethostbyname.c
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# Wrapped by wietse@wzv on Sun Jan 8 17:08:48 1995
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PATH=/bin:/usr/bin:/usr/ucb ; export PATH
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if test -f gethostbyaddr.c -a "${1}" != "-c" ; then
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echo shar: Will not over-write existing file \"gethostbyaddr.c\"
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else
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echo shar: Extracting \"gethostbyaddr.c\" \(1073 characters\)
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sed "s/^X//" >gethostbyaddr.c <<'END_OF_gethostbyaddr.c'
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X /*
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X * gethostbyaddr tester. compile with:
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X *
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X * cc -o gethostbyaddr gethostbyaddr.c (SunOS 4.x)
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X *
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X * cc -o gethostbyaddr gethostbyaddr.c -lnsl (SunOS 5.x)
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X *
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X * run as: gethostbyaddr address
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X *
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X * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
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X */
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X
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X#include <sys/types.h>
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X#include <sys/socket.h>
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X#include <netinet/in.h>
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X#include <arpa/inet.h>
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X#include <netdb.h>
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X#include <stdio.h>
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X
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Xmain(argc, argv)
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Xint argc;
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Xchar **argv;
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X{
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X struct hostent *hp;
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X long addr;
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X
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X if (argc != 2) {
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X fprintf(stderr, "usage: %s i.p.addres\n", argv[0]);
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X exit(1);
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X }
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X addr = inet_addr(argv[1]);
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X if (hp = gethostbyaddr((char *) &addr, sizeof(addr), AF_INET)) {
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X printf("Hostname:\t%s\n", hp->h_name);
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X printf("Aliases:\t");
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X while (hp->h_aliases[0])
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X printf("%s ", *hp->h_aliases++);
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X printf("\n");
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X printf("Addresses:\t");
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X while (hp->h_addr_list[0])
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X printf("%s ", inet_ntoa(*(struct in_addr *) * hp->h_addr_list++));
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X printf("\n");
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X exit(0);
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X }
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X fprintf(stderr, "host %s not found\n", argv[1]);
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X exit(1);
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X}
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END_OF_gethostbyaddr.c
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if test 1073 -ne `wc -c <gethostbyaddr.c`; then
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echo shar: \"gethostbyaddr.c\" unpacked with wrong size!
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fi
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# end of overwriting check
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fi
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if test -f gethostbyname.c -a "${1}" != "-c" ; then
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echo shar: Will not over-write existing file \"gethostbyname.c\"
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else
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echo shar: Extracting \"gethostbyname.c\" \(999 characters\)
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sed "s/^X//" >gethostbyname.c <<'END_OF_gethostbyname.c'
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X /*
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X * gethostbyname tester. compile with:
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X *
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X * cc -o gethostbyname gethostbyname.c (SunOS 4.x)
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X *
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X * cc -o gethostbyname gethostbyname.c -lnsl (SunOS 5.x)
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X *
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X * run as: gethostbyname hostname
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X *
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X * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
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X */
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X#include <sys/types.h>
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X#include <sys/socket.h>
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X#include <netinet/in.h>
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X#include <arpa/inet.h>
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X#include <netdb.h>
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X#include <stdio.h>
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X
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Xmain(argc, argv)
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Xint argc;
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Xchar **argv;
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X{
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X struct hostent *hp;
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X
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X if (argc != 2) {
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X fprintf(stderr, "usage: %s hostname\n", argv[0]);
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X exit(1);
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X }
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X if (hp = gethostbyname(argv[1])) {
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X printf("Hostname:\t%s\n", hp->h_name);
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X printf("Aliases:\t");
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X while (hp->h_aliases[0])
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X printf("%s ", *hp->h_aliases++);
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X printf("\n");
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X printf("Addresses:\t");
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X while (hp->h_addr_list[0])
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X printf("%s ", inet_ntoa(*(struct in_addr *) * hp->h_addr_list++));
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X printf("\n");
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X exit(0);
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X } else {
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X fprintf(stderr, "host %s not found\n", argv[1]);
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X exit(1);
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X }
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X}
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END_OF_gethostbyname.c
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if test 999 -ne `wc -c <gethostbyname.c`; then
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echo shar: \"gethostbyname.c\" unpacked with wrong size!
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fi
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# end of overwriting check
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fi
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echo shar: End of shell archive.
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exit 0
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