/*

Copyright (c) 2007 Carl Byington - 510 Software Group, released under
the GPL version 3 or any later version at your choice available at
http://www.gnu.org/licenses/gpl-3.0.txt

*/


// debug levels:
// 4 - show syslog lines that match regex
// 3 - show addresses being dropped/released from the filter
// 2 - show files open/close
// 1 - show config files loading

#include "includes.h"
#include <iostream>
#include <cstdlib>
#include <errno.h>
#include <sysexits.h>
#include <pthread.h>
#include <syslog.h>
#include <sys/wait.h>   /* header for waitpid() and various macros */
#include <signal.h>     /* header for signal functions */

static char* syslog2iptables_version = "$Id$";

extern "C" {
    void sigchld(int sig);
    void sigterm(int sig);
}
int  debug_syslog  = 0;
bool syslog_opened = false;
bool use_syslog    = true;  // false to printf
bool loader_run    = true;  // used to stop the config loader thread
CONFIG   *config = NULL;    // protected by the config_mutex
int   generation = 0;       // protected by the config_mutex
const int maxlen = 1000;    // used for snprintf buffers

pthread_mutex_t  config_mutex;
pthread_mutex_t  syslog_mutex;


////////////////////////////////////////////////
// syslog a message
//
void my_syslog(char *text) {
    if (use_syslog) {
        pthread_mutex_lock(&syslog_mutex);
            if (!syslog_opened) {
                openlog("syslog2iptables", LOG_PID, LOG_AUTHPRIV);
                syslog_opened = true;
            }
            syslog(LOG_NOTICE, "%s", text);
        pthread_mutex_unlock(&syslog_mutex);
    }
    else {
        printf("%s\n", text);
    }
}

////////////////////////////////////////////////
//  reload the config
//
CONFIG* new_conf();
CONFIG* new_conf() {
    CONFIG *newc = new CONFIG;
    pthread_mutex_lock(&config_mutex);
        newc->generation = generation++;
    pthread_mutex_unlock(&config_mutex);
    if (debug_syslog) {
        char buf[maxlen];
        snprintf(buf, sizeof(buf), "loading configuration generation %d", newc->generation);
        my_syslog(buf);
    }
    if (load_conf(*newc, "syslog2iptables.conf")) {
        newc->load_time = time(NULL);
        return newc;
    }
    delete newc;
    return NULL;
}


////////////////////////////////////////////////
//  thread to watch the old config files for changes
//  and reload when needed.
//
void* config_loader(void *arg);
void* config_loader(void *arg) {
    typedef set<CONFIG *> configp_set;
    while (loader_run) {
        sleep(180);  // look for modifications every 3 minutes
        if (!loader_run) break;
        CONFIG &dc = *config;
        time_t then = dc.load_time;
        struct stat st;
        bool reload = false;
        for (string_set::iterator i=dc.config_files.begin(); i!=dc.config_files.end(); i++) {
            char *fn = *i;
            if (stat(fn, &st))           reload = true; // file disappeared
            else if (st.st_mtime > then) reload = true; // file modified
            if (reload) break;
        }
        if (reload) {
            CONFIG *newc = new_conf();
            if (newc) {
                // replace the global config pointer
                pthread_mutex_lock(&config_mutex);
                    config = newc;
                pthread_mutex_unlock(&config_mutex);
            }
            else {
                // failed to load new config
                my_syslog("failed to load new configuration");
                system("echo 'failed to load new /etc/syslog2iptables.conf' | mail -s 'error in /etc/syslog2iptables.conf' root");
                // update the load time on the current config to prevent complaining every 3 minutes
                dc.load_time = time(NULL);
            }
        }
    }
    return NULL;
}


////////////////////////////////////////////////
// The signal handler function for child process terminations,
// called when a child terminates.
//
void sigchld(int sig)
{
    int status;
    /* Wait for any child without blocking */
    while (waitpid(-1, &status, WNOHANG) > 0) {
        // ignore child exit status, we only do this to cleanup zombies
    }
}


////////////////////////////////////////////////
// The termination signal handler function, called to
// request termination of this process.
//
void sigterm(int sig)
{
    loader_run = false;
    signal(sig, SIG_DFL);   // quit on repeated signals
}


void usage(char *prog);
void usage(char *prog)
{
    fprintf(stderr, "Usage: %s  [-d [level]] [-c]\n", prog);
    fprintf(stderr, "-c will load and dump the config to stdout\n");
    fprintf(stderr, "-d will set the syslog message level, currently 0 to 3\n");
}


void worker();
void worker()
{
    time_t t = time(NULL);
    CONFIG *c;
    pthread_mutex_lock(&config_mutex);
        c = config;
        c->reference_count++;
    pthread_mutex_unlock(&config_mutex);
    while (loader_run) {
        if (c != config) {
            pthread_mutex_lock(&config_mutex);
                CONFIG *old = c;    old->reference_count--;
                c = config;         c->reference_count++;
            pthread_mutex_unlock(&config_mutex);
            if (!old->reference_count) {
                if (debug_syslog) {
                    char buf[maxlen];
                    snprintf(buf, sizeof(buf), "freeing memory for old configuration generation %d", old->generation);
                    my_syslog(buf);
                }
                delete old; // destructor does all the work
            }
        }
        c->read();
        c->sleep(2, t);
    }
    // worker shutting down, free all ip addresses
    c->free_all();
}


int main(int argc, char *argv[])
{
    token_init();
    bool check = false;
    int c;
    const char *args = "d:ch";
    extern char *optarg;

    // Process command line options
    while ((c = getopt(argc, argv, args)) != -1) {
        switch (c) {
            case 'c':
                check = true;
                break;

            case 'd':
                if (optarg == NULL || *optarg == '\0') debug_syslog = 1;
                else                                   debug_syslog = atoi(optarg);
                break;

            case 'h':
            default:
                usage(argv[0]);
                exit(EX_USAGE);
        }
    }

    if (check) {
        use_syslog   = false;
        debug_syslog = 10;
        config = new_conf();
        if (config) {
            config->dump();
            delete config;
            return 0;
        }
        else {
            return 1;   // config failed to load
        }
    }

    // switch to background mode
    if (daemon(1,0) < 0) {
        fprintf(stderr, "daemon() call failed\n");
        exit(EX_UNAVAILABLE);
    }

    // write the pid
    const char *pidpath = "/var/run/syslog2iptables.pid";
    unlink(pidpath);
    FILE *f = fopen(pidpath, "w");
    if (f) {
#ifdef linux
        // from a comment in the DCC source code:
        // Linux threads are broken.  Signals given the
        // original process are delivered to only the
        // thread that happens to have that PID.  The
        // sendmail libmilter thread that needs to hear
        // SIGINT and other signals does not, and that breaks
        // scripts that need to stop milters.
        // However, signaling the process group works.
        fprintf(f, "-%d\n", (u_int)getpgrp());
#else
        fprintf(f, "%d\n", (u_int)getpid());
#endif
        fclose(f);
    }

    // setup signal handler for termination signals
    signal(SIGHUP, sigterm);
    signal(SIGTERM, sigterm);
    signal(SIGINT, sigterm);

    // initialize the thread sync objects
    pthread_mutex_init(&config_mutex, 0);
    pthread_mutex_init(&syslog_mutex, 0);

    // load the initial config
    config = new_conf();
    if (!config) {
        my_syslog("failed to load initial configuration, quitting");
        exit(1);
    }

    // setup sigchld handler to prevent zombies
    struct sigaction act;
    act.sa_handler = sigchld;       // Assign sig_chld as our SIGCHLD handler
    sigemptyset(&act.sa_mask);      // We don't want to block any other signals in this example
    act.sa_flags = SA_NOCLDSTOP;    // only want children that have terminated
    if (sigaction(SIGCHLD, &act, NULL) < 0) {
        my_syslog("failed to setup SIGCHLD handler");
        exit(1);
    }

    // only create threads after the fork() in daemon
    pthread_t tid;
    if (pthread_create(&tid, 0, config_loader, 0))
        my_syslog("failed to create config loader thread");
    if (pthread_detach(tid))
        my_syslog("failed to detach config loader thread");

    worker();

    return EXIT_SUCCESS;
}