test_getsockname.c   [plain text]

/*
 * test_getsockname.c
 * 
 * This routine demonstrates a bug in the socket emulation library of
 * Solaris and other monstrosities that uses STREAMS.  On other
 * machines with a real networking layer, it prints the local
 * interface address that is used to send a message to a specific
 * host.  On Solaris, it prints out 0.0.0.0.
 */

#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <stdio.h>
#include <string.h>
#include "autoconf.h"

int
main(argc, argv)
    int argc;
    char *argv[];
{
    int sock;
    GETSOCKNAME_ARG3_TYPE i;
    struct hostent *host;
    struct sockaddr_in s_sock;		/* server address */
    struct sockaddr_in c_sock;		/* client address */
    
    char *hostname;

    if (argc == 2) {
	hostname = argv[1];
    } else {
	fprintf(stderr, "Usage: %s hostname\n", argv[0]);
	exit(1);
    }

    /* Look up server host */
    if ((host = gethostbyname(hostname)) == (struct hostent *) 0) {
	fprintf(stderr, "%s: unknown host\n", hostname);
	exit(1);
    }

    /* Set server's address */
    (void) memset((char *)&s_sock, 0, sizeof(s_sock));

    memcpy((char *)&s_sock.sin_addr, host->h_addr, sizeof(s_sock.sin_addr));
#ifdef DEBUG
    printf("s_sock.sin_addr is %s\n", inet_ntoa(s_sock.sin_addr));
#endif
    s_sock.sin_family = AF_INET;
    s_sock.sin_port = htons(5555);
    
    /* Open a socket */
    if ((sock = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
	perror("socket");
	exit(1);
    }

    memset((char *)&c_sock, 0, sizeof(c_sock));
    c_sock.sin_family = AF_INET;

    /* Bind it to set the address; kernel will fill in port # */
    if (bind(sock, (struct sockaddr *)&c_sock, sizeof(c_sock)) < 0) {
	perror("bind");
	exit(1);
    }
	
    /* "connect" the datagram socket; this is necessary to get a local address
       properly bound for getsockname() below. */
    if (connect(sock, (struct sockaddr *)&s_sock, sizeof(s_sock)) == -1) {
	perror("connect");
	exit(1);
    }
    
    /* Get my address */
    memset((char *) &c_sock, 0, sizeof(c_sock));
    i = sizeof(c_sock);
    if (getsockname(sock, (struct sockaddr *)&c_sock, &i) < 0) {
	perror("getsockname");
	exit(1);
    }

    printf("My interface address is: %s\n", inet_ntoa(c_sock.sin_addr));
    
    exit(0);
}