source: vendor/3.5.11/source3/lib/sock_exec.c

/* 
   Unix SMB/CIFS implementation.
   Samba utility functions
   Copyright (C) Andrew Tridgell 1992-1998
   Copyright (C) Tim Potter      2000-2001
   
   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 3 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, see <http://www.gnu.org/licenses/>.
*/

#include "includes.h"

/*******************************************************************
this is like socketpair but uses tcp. It is used by the Samba
regression test code
The function guarantees that nobody else can attach to the socket,
or if they do that this function fails and the socket gets closed
returns 0 on success, -1 on failure
the resulting file descriptors are symmetrical
 ******************************************************************/
static int socketpair_tcp(int fd[2])
{
        int listener;
        struct sockaddr_in sock;
        struct sockaddr_in sock2;
        socklen_t socklen = sizeof(sock);
        int connect_done = 0;
        
        fd[0] = fd[1] = listener = -1;

        memset(&sock, 0, sizeof(sock));
        
        if ((listener = socket(PF_INET, SOCK_STREAM, 0)) == -1) goto failed;

        memset(&sock2, 0, sizeof(sock2));
#ifdef HAVE_SOCK_SIN_LEN
        sock2.sin_len = sizeof(sock2);
#endif
        sock2.sin_family = PF_INET;

        if (bind(listener, (struct sockaddr *)&sock2, sizeof(sock2)) != 0) goto failed;

        if (listen(listener, 1) != 0) goto failed;

        if (getsockname(listener, (struct sockaddr *)&sock, &socklen) != 0) goto failed;

        if ((fd[1] = socket(PF_INET, SOCK_STREAM, 0)) == -1) goto failed;

        set_blocking(fd[1], 0);

        sock.sin_addr.s_addr = htonl(INADDR_LOOPBACK);

        if (sys_connect(fd[1], (struct sockaddr *)&sock) == -1) {
                if (errno != EINPROGRESS) goto failed;
        } else {
                connect_done = 1;
        }

        if ((fd[0] = accept(listener, (struct sockaddr *)&sock, &socklen)) == -1) goto failed;

        close(listener);
        if (connect_done == 0) {
                if (sys_connect(fd[1], (struct sockaddr *)&sock) != 0
                    && errno != EISCONN) goto failed;
        }

        set_blocking(fd[1], 1);

        /* all OK! */
        return 0;

 failed:
        if (fd[0] != -1) close(fd[0]);
        if (fd[1] != -1) close(fd[1]);
        if (listener != -1) close(listener);
        return -1;
}


/*******************************************************************
run a program on a local tcp socket, this is used to launch smbd
when regression testing
the return value is a socket which is attached to a subprocess
running "prog". stdin and stdout are attached. stderr is left
attached to the original stderr
 ******************************************************************/
int sock_exec(const char *prog)
{
        int fd[2];
        if (socketpair_tcp(fd) != 0) {
                DEBUG(0,("socketpair_tcp failed (%s)\n", strerror(errno)));
                return -1;
        }
        if (fork() == 0) {
                close(fd[0]);
                close(0);
                close(1);
                if (dup(fd[1]) == -1) {
                        exit(1);
                }
                if (dup(fd[1]) == -1) {
                        exit(1);
                }
                exit(system(prog));
        }
        close(fd[1]);
        return fd[0];
}