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111 lines
3.1 KiB
C

#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <stdlib.h>
#include "easysock.h"
#define PROG_NAME "basicproxy"
#define PROG_VER "0.01"
void forward_data(int from_fd, int to_fd) {
int n = 0;
char* buffer = malloc(3000*sizeof(char));
while ((n = recv(from_fd, buffer, 3000, 0)) > 0) { // read data from input socket
send(to_fd, buffer, n, 0); // send data to output socket
}
}
void print_prog_info() {
printf("%s [Local IP address] [local port] [remote IP address] [remote port]\n",PROG_NAME);
}
void print_version_info() {
printf("%s %s\n",PROG_NAME,PROG_VER);
}
void print_help_info() {
printf("\n%s - A simple TCP proxy written in C.\n\n",PROG_NAME);
printf("Syntax - ");
print_prog_info();
printf("[Local IP address] - The local address to bind to\n"
"[local port] - The local port to listen on\n"
"[remote IP address] - The remote IP to connect to\n"
"[remote port] - The remote port to connect to\n");
printf("\nExample: %s 127.0.0.1 3000 1.2.3.4 5000 - Listen on '127.0.0.1:3000', and forward all data from there to '1.2.3.4:5000'\n\n",PROG_NAME);
}
int main(int argc,char* argv[]) {
/* argv[1] = local address
argv[2] = local port
argv[3] = remote address
argv[4] = remote port */
if (argc == 2) {
if (strcmp(argv[1],"-v") == 0 || strcmp(argv[1],"--version") == 0) {
print_version_info();
exit(0);
} else if (strcmp(argv[1],"-h") == 0 || strcmp(argv[1],"--help") == 0) {
print_help_info();
exit(0);
}
}
if (argc != 5) {
print_prog_info();
exit(230);
}
char* local_addr = argv[1];
int local_port = strtol(argv[2],NULL,10);
char* remote_addr = argv[3];
int remote_port = strtol(argv[4],NULL,10);
int preferred_local_network = check_ip_ver(local_addr);
int preferred_remote_network = check_ip_ver(remote_addr);
printf("Using %d for local\nUsing %d for remote\n",preferred_local_network,preferred_remote_network);
if ((preferred_local_network == -1) || (preferred_remote_network == -1)) {
exit(207);
}
char preferred_transport = 'T';
struct sockaddr addr_struct;
int server_sock = create_local(preferred_local_network,preferred_transport,local_addr,local_port,&addr_struct);
int addrlen;
if (check_ip_ver(local_addr) == 4) {
addrlen = sizeof(struct sockaddr_in);
} else if (check_ip_ver(local_addr) == 6) {
addrlen = sizeof(struct sockaddr_in6);
} else {
exit(207);
}
listen(server_sock,50); /* Arbitrary number, change later */
printf("Listening on %s:%d\n",local_addr,local_port);
struct sockaddr remote_addr_struct;
while (1) {
int from_client = accept(server_sock,&addr_struct,(socklen_t *)&addrlen);
int to_server = create_remote(preferred_remote_network,preferred_transport,remote_addr,remote_port,&remote_addr_struct);
printf("Connection established to %s:%d\n",remote_addr,remote_port);
if (fork() == 0) {
/* fork returns 0 for a child, so we're in the child's execution
right now */
close(server_sock);
if (fork() == 0) {
forward_data(from_client,to_server);
exit(0);
}
if (fork() == 0) {
forward_data(to_server,from_client);
exit(0);
}
exit(0);
}
}
}