I have a problem with a proxy server in c. usage: laddr lport rhost rport
Input : ./proxy localhost 8333 localhost 8080
And I get an error: bind localhost 8333 can't assign requested address.
Code:
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <netdb.h>
#include <string.h>
#include <signal.h>
#include <assert.h>
#include <syslog.h>
#include <sys/types.h>
#include <sys/select.h>
#include <sys/file.h>
#include <sys/ioctl.h>
#include <sys/param.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/wait.h>
#include <netinet/in.h>
#include <arpa/ftp.h>
#include <arpa/inet.h>
#include <arpa/telnet.h>
#define BUF_SIZE 4096
extern int sys_nerr, errno;
char client_hostname[64];
void
cleanup(int sig)
{
syslog(LOG_INFO, "Cleaning up...");
exit(0);
}
void
sigreap(int sig)
{
int status;
pid_t p;
while ((p = waitpid(-1, &status, WNOHANG)) > 0) {
syslog(LOG_INFO, "sigreap: pid=%d, status=%d\n", (int) p, status);
}
/* doh! */
signal(SIGCHLD, sigreap);
}
void
set_nonblock(int fd)
{
int fl;
int x;
x = fcntl(fd, F_GETFL, &fl);
if (x < 0) {
syslog(LOG_ERR, "fcntl F_GETFL: FD %d: %s", fd, strerror(errno));
exit(1);
}
fl |= O_NONBLOCK;
x = fcntl(fd, F_SETFL, &fl);
if (x < 0) {
syslog(LOG_ERR, "fcntl F_SETFL: FD %d: %s", fd, strerror(errno));
exit(1);
}
}
int
create_server_sock(char *addr, int port)
{
int addrlen, s, on = 1, x;
static struct sockaddr_in client_addr;
s = socket(AF_INET, SOCK_STREAM, 0);
if (s < 0)
perror("socket"), exit(1);
addrlen = sizeof(client_addr);
memset(&client_addr, '\0', addrlen);
client_addr.sin_family = AF_INET;
client_addr.sin_addr.s_addr = inet_addr(addr);
client_addr.sin_port = htons(port);
setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &on, 4);
x = bind(s, (struct sockaddr *) &client_addr, addrlen);
if (x < 0)
perror("bind"), exit(1);
x = listen(s, 5);
if (x < 0)
perror("listen"), exit(1);
return s;
}
int
open_remote_host(char *host, int port)
{
struct sockaddr_in rem_addr;
int len, s, x;
struct hostent *H;
int on = 1;
H = gethostbyname(host);
if (!H)
return (-2);
len = sizeof(rem_addr);
s = socket(AF_INET, SOCK_STREAM, 0);
if (s < 0)
return s;
setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &on, 4);
len = sizeof(rem_addr);
memset(&rem_addr, '\0', len);
rem_addr.sin_family = AF_INET;
memcpy(&rem_addr.sin_addr, H->h_addr, H->h_length);
rem_addr.sin_port = htons(port);
x = connect(s, (struct sockaddr *) &rem_addr, len);
if (x < 0) {
close(s);
return x;
}
set_nonblock(s);
return s;
}
int
get_hinfo_from_sockaddr(struct sockaddr_in addr, int len, char *fqdn)
{
struct hostent *hostinfo;
hostinfo = gethostbyaddr((char *) &addr.sin_addr.s_addr, len, AF_INET);
if (!hostinfo) {
sprintf(fqdn, "%s", inet_ntoa(addr.sin_addr));
return 0;
}
if (hostinfo && fqdn)
sprintf(fqdn, "%s [%s]", hostinfo->h_name, inet_ntoa(addr.sin_addr));
return 0;
}
int
wait_for_connection(int s)
{
static int newsock, len;
static struct sockaddr_in peer;
len = sizeof(struct sockaddr);
newsock = accept(s, (struct sockaddr *) &peer, &len);
/* dump_sockaddr (peer, len); */
if (newsock < 0) {
if (errno != EINTR)
perror("accept");
}
get_hinfo_from_sockaddr(peer, len, client_hostname);
set_nonblock(newsock);
return (newsock);
}
int
mywrite(int fd, char *buf, int *len)
{
int x = write(fd, buf, *len);
if (x < 0)
return x;
if (x == 0)
return x;
if (x != *len)
memmove(buf, buf+x, (*len)-x);
*len -= x;
return x;
}
void
service_client(int cfd, int sfd)
{
int maxfd;
char *sbuf;
char *cbuf;
int x, n;
int cbo = 0;
int sbo = 0;
fd_set R;
sbuf = malloc(BUF_SIZE);
cbuf = malloc(BUF_SIZE);
maxfd = cfd > sfd ? cfd : sfd;
maxfd++;
while (1) {
struct timeval to;
if (cbo) {
if (mywrite(sfd, cbuf, &cbo) < 0 && errno != EWOULDBLOCK) {
syslog(LOG_ERR, "write %d: %s", sfd, strerror(errno));
exit(1);
}
}
if (sbo) {
if (mywrite(cfd, sbuf, &sbo) < 0 && errno != EWOULDBLOCK) {
syslog(LOG_ERR, "write %d: %s", cfd, strerror(errno));
exit(1);
}
}
FD_ZERO(&R);
if (cbo < BUF_SIZE)
FD_SET(cfd, &R);
if (sbo < BUF_SIZE)
FD_SET(sfd, &R);
to.tv_sec = 0;
to.tv_usec = 1000;
x = select(maxfd+1, &R, 0, 0, &to);
if (x > 0) {
if (FD_ISSET(cfd, &R)) {
n = read(cfd, cbuf+cbo, BUF_SIZE-cbo);
syslog(LOG_INFO, "read %d bytes from CLIENT (%d)", n, cfd);
if (n > 0) {
cbo += n;
} else {
close(cfd);
close(sfd);
_exit(0);
}
}
if (FD_ISSET(sfd, &R)) {
n = read(sfd, sbuf+sbo, BUF_SIZE-sbo);
syslog(LOG_INFO, "read %d bytes from SERVER (%d)\n", n, sfd);
if (n > 0) {
sbo += n;
} else {
close(sfd);
close(cfd);
_exit(0);
}
}
} else if (x < 0 && errno != EINTR) {
close(sfd);
close(cfd);
_exit(0);
}
}
}
int
main(int argc, char *argv[])
{
char *localaddr = strdup(argv[1]);
int localport = atoi(argv[2]);
char *remoteaddr = strdup(argv[3]);
int remoteport = atoi(argv[4]);
int client, server;
int master_sock;
if (5 != argc) {
fprintf(stderr, "usage: %s laddr lport rhost rport\n", argv[0]);
exit(1);
}
assert(localaddr);
assert(localport > 0);
assert(remoteaddr);
assert(remoteport > 0);
openlog(argv[0], LOG_PID, LOG_LOCAL4);
signal(SIGINT, cleanup);
signal(SIGCHLD, sigreap);
master_sock = create_server_sock(localaddr, localport);
for (;;) {
if ((client = wait_for_connection(master_sock)) < 0)
continue;
if ((server = open_remote_host(remoteaddr, remoteport)) < 0)
continue;
if (!fork()) {
syslog(LOG_NOTICE, "connection from %s fd=%d\n", client_hostname, client);
syslog(LOG_INFO, "connected to %s:%d fd=%d\n", remoteaddr, remoteport, server);
service_client(client, server);
}
close(client);
close(server);
}
}
How can I correct the code so that it works?
from man inet(3):
The inet_addr() function converts the Internet host address cp from IPv4 numbers-and-dots notation into binary data in network byte order. If the input is invalid, INADDR_NONE (usually -1) is returned.
problem is in function create_server_sock() where you do client_addr.sin_addr.s_addr = inet_addr("localhost");. obviously "localhost" is not in numbers-and-dots notation. you should use gethostbyname like you do with remoteaddr or preferably getaddrinfo
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