socket accept only specific addresses?

Question

I am writing a small tcp server based on the example listed below , from here.

#include <sys/socket.h>
#include <sys/un.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#define MY_SOCK_PATH "/somepath"
#define LISTEN_BACKLOG 50

#define handle_error(msg) \
    do { perror(msg); exit(EXIT_FAILURE); } while (0)

int
main(int argc, char *argv[])
{
    int sfd, cfd;
    struct sockaddr_un my_addr, peer_addr;
    socklen_t peer_addr_size;

   sfd = socket(AF_UNIX, SOCK_STREAM, 0);
    if (sfd == -1)
        handle_error("socket");

   memset(&my_addr, 0, sizeof(struct sockaddr_un));
                        /* Clear structure */
    my_addr.sun_family = AF_UNIX;
    strncpy(my_addr.sun_path, MY_SOCK_PATH,
            sizeof(my_addr.sun_path) - 1);

   if (bind(sfd, (struct sockaddr *) &my_addr,
            sizeof(struct sockaddr_un)) == -1)
        handle_error("bind");

   if (listen(sfd, LISTEN_BACKLOG) == -1)
        handle_error("listen");

   /* Now we can accept incoming connections one
       at a time using accept(2) */

   peer_addr_size = sizeof(struct sockaddr_un);
    cfd = accept(sfd, (struct sockaddr *) &peer_addr,
                 &peer_addr_size);
    if (cfd == -1)
        handle_error("accept");

   /* Code to deal with incoming connection(s)... */

   /* When no longer required, the socket pathname, MY_SOCK_PATH
       should be deleted using unlink(2) or remove(3) */
}

When using accept() to open a new connection, is it possible to only accept connections from whitelisted IP-addresses OR reject blacklisted IP-addresses somehow?

The only technique I have found so far is to first accept, check the address, and then close() afterwards if its not an approved address.

Any suggestions?

possible duplicate of [Server socket - accept connections only from IP addresses in the whitelist](http://stackoverflow.com/questions/9696618/server-socket-accept-connections-only-from-ip-addresses-in-the-whitelist) — Nick, Mar 21 '13 at 14:10

score 6 · Accepted Answer · answered Mar 21 '13 at 15:19

With the POSIX API and TCP, you have to do accept() to lookup a clients address, and then you are free to close, receive, send or ignore.

Normally you would use the operating systems firewall for a task like this.

And remember just ignoring certain clients will not add security, as you are still susceptible to man in the middle, replay and sniffing attacks.

socket accept only specific addresses?

1 Answers1

Linked