Build: gcc -o udp_redirect udp_redirect.c
udp_redirect.c
Version 2013-05-30
Copyright (C) 2007 Ivan Tikhonov
Copyright (C) 2013 Stuart Shelton, HP Autonomy
This software is provided 'as-is', without any express or implied
warranty. In no event will the authors be held liable for any damages
arising from the use of this software.
Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it
freely, subject to the following restrictions:
1. The origin of this software must not be misrepresented; you must not
claim that you wrote the original software. If you use this software
in a product, an acknowledgment in the product documentation would be
appreciated but is not required.
2. Altered source versions must be plainly marked as such, and must not be
misrepresented as being the original software.
3. This notice may not be removed or altered from any source distribution.
Ivan Tikhonov, kefeer@brokestream.com
This source has been modified to support sending data to the destination
IP address from a different source-ip to the listen-ip, to enable proxying
on multi-homed hosts
Stuart Shelton, stuart.shelton@hp.com
*/
#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <netinet/in.h>
intbindsocket(char* ip,intport );
intmain(intargc,char* argv[] );
intbindsocket(char* ip,intport ) {
intfd;
structsockaddr_in addr;
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = inet_addr( ip );
addr.sin_port = htons( port );
fd = socket( PF_INET, SOCK_DGRAM, IPPROTO_IP );
if( -1 == bind( fd, (structsockaddr*)&addr,sizeof( addr ) ) ) {
fprintf( stderr,"Cannot bind address (%s:%d)\n", ip, port );
exit( 1 );
}
returnfd;
}
intmain(intargc,char* argv[] ) {
inti, listen, output;
char*inip, *inpt, *srcip, *dstip, *dstpt;
structsockaddr_in src;
structsockaddr_in dst;
structsockaddr_in ret;
if( 3 != argc && 5 != argc && 6 != argc ) {
fprintf( stderr,"Usage: %s <listen-ip> <listen-port> [[source-ip] <destination-ip> <destination-port>]\n", argv[ 0 ] );
exit( 1 );
}
i = 1;
inip = argv[ i++ ]; /* 1 */
inpt = argv[ i++ ]; /* 2 */
if( 6 == argc )
srcip = argv[ i++ ]; /* 3 */
if( 3 != argc ) {
dstip = argv[ i++ ]; /* 3 or 4 */
dstpt = argv[ i++ ]; /* 4 or 5 */
}
listen = bindsocket( inip,atoi( inpt ) );
if( 6 == argc ) {
output = bindsocket( srcip,atoi( inpt ) );
}else{
output = listen;
}
if( 3 != argc ) {
dst.sin_family = AF_INET;
dst.sin_addr.s_addr = inet_addr( dstip );
dst.sin_port = htons(atoi( dstpt ) );
}
ret.sin_addr.s_addr = 0;
while( 1 ) {
charbuffer[65535];
unsignedintsize =sizeof( src );
intlength = recvfrom( listen, buffer,sizeof( buffer ), 0, (structsockaddr*)&src, &size );
if( length <= 0 )
continue;
if( 3 == argc ) {
/* echo, without tracking return packets */
sendto( listen, buffer, length, 0, (structsockaddr*)&src, size );
}elseif( ( src.sin_addr.s_addr == dst.sin_addr.s_addr ) && ( src.sin_port == dst.sin_port ) ) {
/* If we receive a return packet back from our destination ... */
if( ret.sin_addr.s_addr )
/* ... and we've previously remembered having sent packets to this location,
then return them to the original sender */
sendto( output, buffer, length, 0, (structsockaddr*)&ret,sizeof( ret ) );
}else{
sendto( output, buffer, length, 0, (structsockaddr*)&dst,sizeof( dst ) );
/* Remeber original sender to direct return packets towards */
ret = src;
}
}
}
