From 33bed8dfd65a9c2a839044747f1d303e1a31da34 Mon Sep 17 00:00:00 2001 From: wollman Date: Mon, 14 Aug 1995 16:08:39 +0000 Subject: Added a copy of my little program to find the IP address of the outgoing interface for a particular remote host. Requested by: Joerg Wunsch --- share/examples/Makefile | 4 +- share/examples/find_interface/Makefile | 6 ++ share/examples/find_interface/README | 9 ++ share/examples/find_interface/find_interface.c | 111 +++++++++++++++++++++++++ 4 files changed, 128 insertions(+), 2 deletions(-) create mode 100644 share/examples/find_interface/Makefile create mode 100644 share/examples/find_interface/README create mode 100644 share/examples/find_interface/find_interface.c (limited to 'share/examples') diff --git a/share/examples/Makefile b/share/examples/Makefile index 180a592..f498e6d 100644 --- a/share/examples/Makefile +++ b/share/examples/Makefile @@ -1,8 +1,8 @@ -# $Id: Makefile,v 1.13 1995/03/30 00:05:58 ache Exp $ +# $Id: Makefile,v 1.14 1995/08/12 16:28:10 joerg Exp $ # # Doing a make install builds /usr/share/examples -DIRS=etc FreeBSD_version ibcs2 lkm sunrpc +DIRS=etc find_interface FreeBSD_version ibcs2 lkm sunrpc DDIR=${DESTDIR}/usr/share/examples diff --git a/share/examples/find_interface/Makefile b/share/examples/find_interface/Makefile new file mode 100644 index 0000000..fcc330c --- /dev/null +++ b/share/examples/find_interface/Makefile @@ -0,0 +1,6 @@ +# $Id$ + +PROG= find_interface +NOMAN= + +.include diff --git a/share/examples/find_interface/README b/share/examples/find_interface/README new file mode 100644 index 0000000..4df4399 --- /dev/null +++ b/share/examples/find_interface/README @@ -0,0 +1,9 @@ +This is a simple program which demonstrates how to query the kernel +routing mechanism using only a UDP socket. Pass it a hostname on +the command line (sorry, it doesn't parse dotted decimal) and it will +print out an IP address which names the interface over which UDP +packets intended for that destination would be sent. +A more sophisticated program might use the list obtained from SIOCGIFCONF +to match the address with an interface name, but applications programmers +much more often need to know the address of the interface rather than +the name. diff --git a/share/examples/find_interface/find_interface.c b/share/examples/find_interface/find_interface.c new file mode 100644 index 0000000..50044d6 --- /dev/null +++ b/share/examples/find_interface/find_interface.c @@ -0,0 +1,111 @@ +/* + * Copyright 1994, 1995 Massachusetts Institute of Technology + * + * Permission to use, copy, modify, and distribute this software and + * its documentation for any purpose and without fee is hereby + * granted, provided that both the above copyright notice and this + * permission notice appear in all copies, that both the above + * copyright notice and this permission notice appear in all + * supporting documentation, and that the name of M.I.T. not be used + * in advertising or publicity pertaining to distribution of the + * software without specific, written prior permission. M.I.T. makes + * no representations about the suitability of this software for any + * purpose. It is provided "as is" without express or implied + * warranty. + * + * THIS SOFTWARE IS PROVIDED BY M.I.T. ``AS IS''. M.I.T. DISCLAIMS + * ALL EXPRESS OR IMPLIED WARRANTIES WITH REGARD TO THIS SOFTWARE, + * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF + * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT + * SHALL M.I.T. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, + * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT + * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF + * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND + * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, + * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT + * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + * + * $Id$ + */ + +/* + * This is a simple program which demonstrates how to query the kernel + * routing mechanism using only a UDP socket. Pass it a hostname on + * the command line (sorry, it doesn't parse dotted decimal) and it will + * print out an IP address which names the interface over which UDP + * packets intended for that destination would be sent. + * A more sophisticated program might use the list obtained from SIOCGIFCONF + * to match the address with an interface name, but applications programmers + * much more often need to know the address of the interface rather than + * the name. + */ +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +int +main(int argc, char **argv) +{ + struct sockaddr_in local, remote; + struct hostent *hp; + int s, rv, namelen; + + argc--, argv++; + + if (!*argv) { + errx(EX_USAGE, "must supply a hostname"); + } + + hp = gethostbyname(*argv); + if (!hp) { + errx(EX_NOHOST, "cannot resolve hostname: %s", *argv); + } + + memcpy(&remote.sin_addr, hp->h_addr_list[0], sizeof remote.sin_addr); + remote.sin_port = htons(60000); + remote.sin_family = AF_INET; + remote.sin_len = sizeof remote; + + local.sin_addr.s_addr = htonl(INADDR_ANY); + local.sin_port = htons(60000); + local.sin_family = AF_INET; + local.sin_len = sizeof local; + + s = socket(PF_INET, SOCK_DGRAM, 0); + if (s < 0) + err(EX_OSERR, "socket"); + + do { + rv = bind(s, (struct sockaddr *)&local, sizeof local); + local.sin_port++; + } while(rv < 0 && errno == EADDRINUSE); + + if (rv < 0) + err(EX_OSERR, "bind"); + + do { + rv = connect(s, (struct sockaddr *)&remote, sizeof remote); + remote.sin_port++; + } while(rv < 0 && errno == EADDRINUSE); + + if (rv < 0) + err(EX_OSERR, "connect"); + + namelen = sizeof local; + rv = getsockname(s, (struct sockaddr *)&local, &namelen); + if (rv < 0) + err(EX_OSERR, "getsockname"); + + printf("Route to %s is out %s\n", *argv, inet_ntoa(local.sin_addr)); + return 0; +} -- cgit v1.1