First commit

Makefile

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+first: main.c
+	gcc -o tuninetd main.c -lpthread -lpcap

README.md

@@ -1 +1,44 @@
-# tuninetd
+# Tuninetd
+
+**tuninetd** - is a simple daemon for tun/tap devices, similar to classic inetd by its logic, but for mentioned interfaceces, instead of a ports.
+
+#### How it works:
+First, you create and configure tun/tap device, then run **tuninetd**. It start listening on that interface, until network packet will be received.
+Next, interface will be released and certain command is executed. From now on, daemon in monitoring state.
+After N seconds of interface idle, tuninetd send "stop" command by path, that you define, and start listening interface by its own again.
+
+Since, **tuninetd** based on **libpcap**, you can specify filter to trigging "start" event and monitoring iddle (i.e. cutoff unwanted traffic).
+To test/debug filters rules - use tcpdump, because it built upon the same library.
+
+**tuninetd** allows you deploy "VPN by demand" or any other "by demand" services, which is the main idea of the project.
+
+#### Installation:
+To build tuninetd, you need to have libpcap-dev library (Debian)<br/>
+Download all files and:
+```sh
+# cd /folder/with/sourcefiles
+# make
+```
+
+#### Usage:
+
+tuninetd -i \<ifname> -c \<path> [-m \<iftype>] [-f <filter>] [-t \<ttl>] [-d]
+
+**-i \<ifname>**: interface to use (tun or tap). Must be up and configured.<br/>
+**-c \<path>**: will be executed with 'start' and 'stop' parameter.<br/>
+**-m \<iftype>**: 'tun' or 'tap' mode. By default 'tun', should be set properly.<br/>
+**-f \<filter>**: specify pcap filter, similar to tcpdump<br/>
+**-t \<ttl>**: seconds of interface idle, before 'stop' command (default is 600).<br/>
+**-d**: demonize process<br/>
+**-h**: prints this help text
+
+#### Example:
+```sh
+# tuninetd -i tun0 -c /test/runtunnel.sh -f "! host 1.2.3.4" -t 3600 -d
+```
+
+### License:
+MIT
+### Author:
+Paul aka root4root \<root4root at gmail dot com><br/>
+**Any suggestions will be appreciated.**

main.c

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+//Author: root4root@gmail.com
+
+#include <fcntl.h>
+#include <pthread.h>
+#include <pcap.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <net/if.h>
+#include <linux/if_tun.h>
+#include <sys/ioctl.h>
+#include <stdarg.h>
+#include <syslog.h>
+#include <unistd.h>
+
+#define BUFSIZE 2000
+
+int debug = 0;
+int status = 0;
+long ts = 0;
+long curts = 0;
+
+char progname[] = "tuninetd";
+
+struct globcfg_t {
+    int isdaemon;
+    pid_t pid;
+    char *cmd_path;
+    char *cmd_path_start;
+    char *cmd_path_stop;
+    char *pcap_filter;
+    char *dev_name;
+    int dev_mode;
+    int ttl;
+} globcfg;
+
+#include "utils.c"
+#include "tun.c"
+#include "pcap.c"
+
+int main(int argc, char *argv[])
+{
+    int x, y, opt=0;
+
+    static const char *optString = "i:t:c:f:m:dh";
+
+    curts = time(NULL);
+
+    globcfg.isdaemon = 0;
+    globcfg.pid = 0;
+    globcfg.cmd_path = NULL;
+    globcfg.ttl = 600;
+    globcfg.dev_mode = IFF_TUN;
+
+    opt = getopt( argc, argv, optString);
+
+    while( opt != -1 ) {
+        switch( opt ) {
+            case 'i':
+                globcfg.dev_name = optarg;
+                break;
+            case 't':
+                globcfg.ttl = atoi(optarg);
+                break;
+            case 'c':
+                globcfg.cmd_path = optarg;
+
+                globcfg.cmd_path_start = malloc(strlen(optarg) + 23);
+                strcpy(globcfg.cmd_path_start, optarg);
+                strcat(globcfg.cmd_path_start, " start > /dev/null 2>&1");
+
+                globcfg.cmd_path_stop = malloc(strlen(optarg) + 22);
+                strcpy(globcfg.cmd_path_stop, optarg);
+                strcat(globcfg.cmd_path_stop, " stop > /dev/null 2>&1");
+                break;
+
+            case 'f':
+                globcfg.pcap_filter = optarg;
+                break;
+            case 'm':
+                if (strcmp("tap", optarg)== 0) {
+                    globcfg.dev_mode = IFF_TAP;
+                }
+                break;
+            case 'd':
+                globcfg.isdaemon = 1;
+                break;
+            case 'h':   /* намеренный проход в следующий case-блок */
+            case '?':
+                usage();
+                break;
+            default:
+                exit(1);
+                break;
+        }
+
+        opt = getopt( argc, argv, optString );
+    }
+
+    if (globcfg.dev_name == NULL) {
+        my_err("tun/tap device must be specified with proper type (-m by default tun).");
+        usage();
+        exit(1);
+    }
+
+    if (globcfg.cmd_path == NULL) {
+        my_err("Executable path must be specified");
+        usage();
+        exit(1);
+    }
+
+    if (globcfg.isdaemon == 1) {
+        globcfg.pid = fork();
+
+        if (globcfg.pid < 0) {
+            my_err("Can't fork process. Abort.");
+            exit(1);
+        }
+
+        if (globcfg.pid > 0) {
+            my_info("---");
+            my_info("Success! tuninetd has been started with pid: %i", globcfg.pid);
+            exit(0);
+        }
+
+        chdir("/");
+
+        setsid();
+
+        close(STDIN_FILENO);
+        close(STDOUT_FILENO);
+        close(STDERR_FILENO);
+    }
+
+    pthread_t inc_x_thread;
+    pthread_t tun_x_thread;
+
+    pthread_attr_t attr;
+
+    pthread_attr_init(&attr);
+    pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
+
+    pthread_create(&inc_x_thread, &attr, inc_x, &x);
+    pthread_create(&tun_x_thread, &attr, tun_x, &y);
+
+    while (1) {
+        usleep(1000000);
+        curts = time(NULL);
+
+        if (ts != 0 && status == 1 && ((curts - ts) >= globcfg.ttl) ) {
+           status = 0;
+           my_info("Executing STOP command... Binding again to interface %s", globcfg.dev_name);
+
+            if (system(globcfg.cmd_path_stop) != 0) {
+                my_err("Warning! Executable command doesn't return 0 (%s)", globcfg.cmd_path_stop);
+            }
+
+           pthread_create(&tun_x_thread, &attr, tun_x, &y);
+        }
+    }
+    return 0;
+}

pcap.c

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+//Author: root4root@gmail.com
+
+void got_packet(u_char *args, const struct pcap_pkthdr *header, const u_char *packet)
+{
+    ts = header->ts.tv_sec;
+}
+
+
+void *inc_x(void *x_void_ptr)
+{
+    struct bpf_program filter;
+
+    char errbuf[PCAP_ERRBUF_SIZE];
+    pcap_t *handle;
+
+    handle = pcap_open_live(globcfg.dev_name, BUFSIZ, 0, 10, errbuf);
+
+    if (handle == NULL) {
+        my_err("Pcap: unable to open interface. %s", errbuf);
+        exit(1);
+    }
+
+    if (globcfg.pcap_filter != NULL) {
+        if (pcap_compile(handle, &filter, globcfg.pcap_filter, 0, PCAP_NETMASK_UNKNOWN) != 0) {
+            my_err("Wrong libpcap filter: \"%s\"", globcfg.pcap_filter);
+            exit(1);
+        }
+
+        pcap_setfilter(handle, &filter);
+    }
+
+    pcap_loop(handle, -1, got_packet, NULL);
+
+    pcap_close(handle);
+}

runtunnel.sh

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+#!/bin/bash
+
+#This is just example of how executable script, which run from tuninetd, may looks like.
+#Accepts 'start' or 'stop' parameter.
+#Author: root4root@gmail.com
+
+controlFile='/var/run/ssh-myvpn-tunnel-control'
+remoteHost='1.2.3.4'
+
+function up()
+{
+    if [ ! -S $controlFile ]
+    then
+        /usr/bin/ssh -S $controlFile -M -f -w 0:0 $remoteHost ifconfig tun0 10.10.10.1/30 pointopoint 10.10.10.2
+        exit 0
+    else
+        echo 'Tunnel already up!'
+        exit 1
+    fi
+}
+
+function down()
+{
+    if [ -S $controlFile ]
+    then
+        /usr/bin/ssh -S $controlFile -O exit $remoteHost
+        exit 0
+    else
+        echo 'Tunnel already down!'
+        exit 1
+    fi
+}
+
+case $1 in
+'start')
+    up
+    ;;
+'stop' )
+    down
+    ;;
+*)
+    echo 'Usage: start|stop'
+    ;;
+esac
+
+exit 1

tun.c

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+//Author: root4root@gmail.com
+
+int tun_alloc(char *dev, int flags) 
+{
+    struct ifreq ifr;
+    int fd, err;
+    char *clonedev = "/dev/net/tun";
+
+    if ( (fd = open(clonedev, O_RDWR)) < 0 ) {
+        my_err("Unable to open clonable device %s", clonedev);
+        return fd;
+    }
+
+    memset(&ifr, 0, sizeof(ifr));
+
+    ifr.ifr_flags = flags;
+
+    if (*dev) {
+        strncpy(ifr.ifr_name, dev, IFNAMSIZ);
+    } 
+
+    if ( (err = ioctl(fd, TUNSETIFF, (void *)&ifr)) < 0 ) {
+        close(fd);
+        return err;
+    }
+
+    return fd;
+}
+
+int cread(int fd, char *buf, int n)
+{
+    int nread;
+
+    if ((nread = read(fd, buf, n)) < 0) {
+        my_err("Error, while reading data. Abort.");
+        exit(1);
+    }
+
+    return nread;
+}
+
+void *tun_x(void *x_void_ptr)
+{
+    int tap_fd;
+    int nread;
+    char buffer[BUFSIZE];
+
+
+    if ( (tap_fd = tun_alloc(globcfg.dev_name, globcfg.dev_mode | IFF_NO_PI)) < 0 ) {
+        my_err("Error connecting to tun/tap interface %s. Abort.", globcfg.dev_name);
+        exit(1);
+    }
+
+    while(1) {
+        nread = cread(tap_fd, buffer, BUFSIZE);
+
+        if (globcfg.pcap_filter != NULL) {
+            usleep(15000); //Wait for libpcap time out.
+            if ( (curts - ts) < 2 ) {
+                do_debug("Read %d bytes from the tap interface\n", nread);
+                break;
+            } 
+        } else {
+             break;   
+        }
+    }
+
+    ts = time(NULL);
+
+    status = 1;
+
+    close(tap_fd);
+
+    my_info("Executing START command...");
+
+    if (system(globcfg.cmd_path_start) != 0) {
+        my_err("Warning! Executable command doesn't return 0 (%s)", globcfg.cmd_path_start);
+    }
+
+    return 0;
+}