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/*
*****************************************************************************
*
* File: tcp_server.c
*
* Author: Damien Stuart (dstuart@dstuart.org)
*
* Purpose: Spawns off a dummy tcp server for fwknopd. Its purpose is
* to accept a tcp connection, then drop it after the first packet.
*
* Copyright 2010-2013 Damien Stuart (dstuart@dstuart.org)
*
* License (GNU Public License):
*
* 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 2
* 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, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
* USA
*
*****************************************************************************
*/
#include "fwknopd_common.h"
#include "tcp_server.h"
#include "log_msg.h"
#include "utils.h"
#include <errno.h>
#if HAVE_SYS_SOCKET_H
#include <sys/socket.h>
#endif
#if HAVE_ARPA_INET_H
#include <arpa/inet.h>
#endif
#if HAVE_NETDB
#include <netdb.h>
#endif
#include <fcntl.h>
#include <sys/select.h>
/* Fork off and run a "dummy" TCP server. The return value is the PID of
* the child process or -1 if there is a fork error.
*/
int
run_tcp_server(fko_srv_options_t *opts)
{
pid_t pid, ppid;
int s_sock, c_sock, sfd_flags, clen, selval;
int reuse_addr = 1, is_err;
fd_set sfd_set;
struct sockaddr_in saddr, caddr;
struct timeval tv;
char sipbuf[MAX_IPV4_STR_LEN] = {0};
unsigned short port;
port = strtol_wrapper(opts->config[CONF_TCPSERV_PORT],
0, MAX_PORT, NO_EXIT_UPON_ERR, &is_err);
if(is_err != FKO_SUCCESS)
{
log_msg(LOG_ERR, "[*] Invalid max TCPSERV_PORT value.\n");
exit(EXIT_FAILURE);
}
log_msg(LOG_INFO, "Kicking off TCP server to listen on port %i.", port);
/* Fork off a child process to run the command and provide its outputs.
*/
pid = fork();
/* Non-zero pid means we are the parent or there was a fork error.
* in either case we simply return that value to the caller.
*/
if (pid != 0)
{
opts->tcp_server_pid = pid;
return(pid);
}
/* Get our parent PID so we can periodically check for it. We want to
* know when it goes away so we can to.
*/
ppid = getppid();
/* We are the child. The first thing to do is close our copy of the
* parent PID file so we don't end up holding the lock if the parent
* suffers a sudden death that doesn't take us out too.
*/
close(opts->lock_fd);
/* Now, let's make a TCP server
*/
if ((s_sock = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0)
{
log_msg(LOG_ERR, "run_tcp_server: socket() failed: %s",
strerror(errno));
exit(EXIT_FAILURE);
}
/* So that we can re-bind to it without TIME_WAIT problems
*/
if(setsockopt(s_sock, SOL_SOCKET, SO_REUSEADDR, &reuse_addr, sizeof(reuse_addr)) == -1)
{
log_msg(LOG_ERR, "run_tcp_server: setsockopt error: %s",
strerror(errno));
exit(EXIT_FAILURE);
}
/* Make our main socket non-blocking so we don't have to be stuck on
* listening for incoming connections.
*/
if((sfd_flags = fcntl(s_sock, F_GETFL, 0)) < 0)
{
log_msg(LOG_ERR, "run_tcp_server: fcntl F_GETFL error: %s",
strerror(errno));
exit(EXIT_FAILURE);
}
sfd_flags |= O_NONBLOCK;
if(fcntl(s_sock, F_SETFL, sfd_flags) < 0)
{
log_msg(LOG_ERR, "run_tcp_server: fcntl F_SETFL error setting O_NONBLOCK: %s",
strerror(errno));
exit(EXIT_FAILURE);
}
/* Construct local address structure */
memset(&saddr, 0, sizeof(saddr));
saddr.sin_family = AF_INET; /* Internet address family */
saddr.sin_addr.s_addr = htonl(INADDR_ANY); /* Any incoming interface */
saddr.sin_port = htons(port); /* Local port */
/* Bind to the local address */
if (bind(s_sock, (struct sockaddr *) &saddr, sizeof(saddr)) < 0)
{
log_msg(LOG_ERR, "run_tcp_server: bind() failed: %s",
strerror(errno));
exit(EXIT_FAILURE);
}
/* Mark the socket so it will listen for incoming connections
* (but only one at a time)
*/
if (listen(s_sock, 1) < 0)
{
log_msg(LOG_ERR, "run_tcp_server: listen() failed: %s",
strerror(errno));
exit(EXIT_FAILURE);
}
clen = sizeof(caddr);
/* Now loop and accept and drop connections after the first packet or a
* short timeout.
*/
while(1)
{
/* Initialize and setup the socket for select.
*/
FD_ZERO(&sfd_set);
FD_SET(s_sock, &sfd_set);
/* Set our select timeout to 200 ms.
*/
tv.tv_sec = 0;
tv.tv_usec = 200000;
selval = select(s_sock+1, &sfd_set, NULL, NULL, &tv);
if(selval == -1)
{
/* Select error - so kill the child and bail.
*/
log_msg(LOG_ERR, "run_tcp_server: select error socket: %s",
strerror(errno));
exit(EXIT_FAILURE);
}
if(selval == 0)
{
/* Timeout - So we check to make sure our parent is still there by simply
* using kill(ppid, 0) and checking the return value.
*/
if(kill(ppid, 0) != 0 && errno == ESRCH)
exit(EXIT_FAILURE);
continue;
}
/* Wait for a client to connect
*/
if((c_sock = accept(s_sock, (struct sockaddr *) &caddr, (socklen_t *)&clen)) < 0)
{
log_msg(LOG_ERR, "run_tcp_server: accept() failed: %s",
strerror(errno));
exit(EXIT_FAILURE); /* Should this be fatal? */
}
if(opts->verbose)
{
memset(sipbuf, 0x0, MAX_IPV4_STR_LEN);
inet_ntop(AF_INET, &(caddr.sin_addr.s_addr), sipbuf, MAX_IPV4_STR_LEN);
log_msg(LOG_INFO, "tcp_server: Got TCP connection from %s.", sipbuf);
}
/* Though hacky and clunky, we just sleep for a second then
* close the socket. No need to read or write anything. This
* just gives the client a sufficient window to send their
* request on this socket. In any case the socket is closed
* after that time.
*/
usleep(1000000);
shutdown(c_sock, SHUT_RDWR);
close(c_sock);
}
}
/***EOF***/
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