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/*
* knock.c
*
* Copyright (c) 2004-2012 by Judd Vinet <jvinet@zeroflux.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <netdb.h>
#include <sys/types.h>
#include <sys/socket.h>
#if defined(__FreeBSD__) || defined(__APPLE__)
#include <netinet/in.h>
#endif
#include <arpa/inet.h>
#include <unistd.h>
#include <string.h>
#include <netinet/in.h>
#include <resolv.h>
#include <getopt.h>
#include <fcntl.h>
static char version[] = "0.7";
#define PROTO_TCP 1
#define PROTO_UDP 2
/* function prototypes */
void vprint(char *fmt, ...);
void ver();
void usage();
int o_verbose = 0;
int o_udp = 0;
int o_delay = 0;
int main(int argc, char** argv)
{
int sd;
struct hostent* host;
struct sockaddr_in addr;
int opt, optidx = 1;
static struct option opts[] =
{
{"verbose", no_argument, 0, 'v'},
{"udp", no_argument, 0, 'u'},
{"delay", required_argument, 0, 'd'},
{"help", no_argument, 0, 'h'},
{"version", no_argument, 0, 'V'},
{0, 0, 0, 0}
};
while((opt = getopt_long(argc, argv, "vud:hV", opts, &optidx))) {
if(opt < 0) {
break;
}
switch(opt) {
case 0: break;
case 'v': o_verbose = 1; break;
case 'u': o_udp = 1; break;
case 'd': o_delay = (int)atoi(optarg); break;
case 'V': ver();
case 'h': /* fallthrough */
default: usage();
}
}
if((argc - optind) < 2) {
usage();
}
if(o_delay < 0) {
fprintf(stderr, "error: delay cannot be negative\n");
exit(1);
}
host = gethostbyname(argv[optind++]);
if(host == NULL) {
fprintf(stderr, "Cannot resolve hostname\n");
exit(1);
}
for(; optind < argc; optind++) {
unsigned short port, proto = PROTO_TCP;
char *ptr, *arg = strdup(argv[optind]);
if((ptr = strchr(arg, ':'))) {
*ptr = '\0';
port = atoi(arg);
arg = ++ptr;
if(!strcmp(arg, "udp")) {
proto = PROTO_UDP;
} else {
proto = PROTO_TCP;
}
} else {
port = atoi(arg);
}
if(o_udp || proto == PROTO_UDP) {
sd = socket(PF_INET, SOCK_DGRAM, 0);
if(sd == -1) {
fprintf(stderr, "Cannot open socket\n");
exit(1);
}
} else {
int flags;
sd = socket(PF_INET, SOCK_STREAM, 0);
if(sd == -1) {
fprintf(stderr, "Cannot open socket\n");
exit(1);
}
flags = fcntl(sd, F_GETFL, 0);
fcntl(sd, F_SETFL, flags | O_NONBLOCK);
}
memset(&addr, 0, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = *((long*)host->h_addr_list[0]);
addr.sin_port = htons(port);
if(o_udp || proto == PROTO_UDP) {
vprint("hitting udp %s:%u\n", inet_ntoa(addr.sin_addr), port);
sendto(sd, "", 1, 0, (struct sockaddr*)&addr, sizeof(addr));
} else {
vprint("hitting tcp %s:%u\n", inet_ntoa(addr.sin_addr), port);
connect(sd, (struct sockaddr*)&addr, sizeof(struct sockaddr));
}
close(sd);
usleep(1000*o_delay);
}
return(0);
}
void vprint(char *fmt, ...)
{
va_list args;
if(o_verbose) {
va_start(args, fmt);
vprintf(fmt, args);
va_end(args);
fflush(stdout);
}
}
void usage() {
printf("usage: knock [options] <host> <port[:proto]> [port[:proto]] ...\n");
printf("options:\n");
printf(" -u, --udp make all ports hits use UDP (default is TCP)\n");
printf(" -d, --delay <t> wait <t> milliseconds between port hits\n");
printf(" -v, --verbose be verbose\n");
printf(" -V, --version display version\n");
printf(" -h, --help this help\n");
printf("\n");
printf("example: knock myserver.example.com 123:tcp 456:udp 789:tcp\n");
printf("\n");
exit(1);
}
void ver() {
printf("knock %s\n", version);
printf("Copyright (C) 2004-2012 Judd Vinet <jvinet@zeroflux.org>\n");
exit(0);
}
/* vim: set ts=2 sw=2 noet: */