/*
 * tlsproxy is a transparent TLS proxy for HTTPS connections.
 *
 * Copyright (C) 2011  Simon Ruderich
 *
 * 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 "tlsproxy.h"
#include "sem.h"
#include "connection.h"

/* socket(), bind(), accept(), listen() */
#include <sys/types.h>
#include <sys/socket.h>
/* close() */
#include <unistd.h>
/* htons() */
#include <arpa/inet.h>
/* sigaction() */
#include <signal.h>
/* errno */
#include <errno.h>
/* pthread_*() */
#include <pthread.h>

/* Size of ringbuffer. */
#define RINGBUFFER_SIZE 10


/* Server should shut down. Set by SIGINT handler. */
static volatile int done;

/* Number of threads. */
static size_t thread_count;
/* Synchronized ring buffer storing accept()ed client sockets. */
static int ringbuffer[RINGBUFFER_SIZE];
static int ringbuffer_read;
static int ringbuffer_write;
static SEM *ringbuffer_full; /* At least one element in the buffer? */
static SEM *ringbuffer_free; /* Space for another element in the buffer? */
static SEM *ringbuffer_lock; /* Read lock. */


static void sigint_handler(int signal);

static void parse_arguments(int argc, char **argv);
static void print_usage(const char *argv);

static void worker_thread(void);


int main(int argc, char **argv) {
    int port;
    int client_socket, server_socket;
    struct sockaddr_in6 server_in;

    size_t i;
    pthread_t *threads;

    struct sigaction action;

    parse_arguments(argc, argv);

    port = atoi(argv[argc - 1]);
    if (0 >= port || 0xffff < port) {
        print_usage(argv[0]);
        fprintf(stderr, "\ninvalid port\n");
        return EXIT_FAILURE;
    }

    /* Setup our SIGINT signal handler which allows a "normal" termination of
     * the server. */
    sigemptyset(&action.sa_mask);
    action.sa_handler = sigint_handler;
    action.sa_flags   = 0;
    sigaction(SIGINT, &action, NULL);

    /* Initialize ring buffer. */
    ringbuffer_read  = 0;
    ringbuffer_write = 0;
    ringbuffer_full  = sem_init(0);
    ringbuffer_free  = sem_init(RINGBUFFER_SIZE);
    ringbuffer_lock  = sem_init(1);
    if (NULL == ringbuffer_full
            || NULL == ringbuffer_free
            || NULL == ringbuffer_lock) {
        perror("sem_init()");
        return EXIT_FAILURE;
    }

    /* Spawn worker threads to handle requests. */
    threads = (pthread_t *)malloc(thread_count * sizeof(pthread_t));
    if (NULL == threads) {
        perror("thread malloc failed");
        return EXIT_FAILURE;
    }
    for (i = 0; i < thread_count; i++) {
        int result;
        pthread_t thread;

        result = pthread_create(&thread, NULL,
                                (void * (*)(void *))&worker_thread,
                                NULL);
        if (0 != result) {
            printf("failed to create worker thread: %s\n", strerror(result));
            return EXIT_FAILURE;
        }

        threads[i] = thread;
    }

    server_socket = socket(PF_INET6, SOCK_STREAM, 0);
    if (-1 == server_socket) {
        perror("socket()");
        return EXIT_FAILURE;
    }

#ifdef DEBUG
    /* Fast rebinding for debug mode, could cause invalid packets. */
    {
        int socket_option = 1;
        setsockopt(server_socket, SOL_SOCKET, SO_REUSEADDR,
                   &socket_option, sizeof(socket_option));
    }
#endif

    /* Bind to the listen socket. */
    memset(&server_in, 0, sizeof(server_in));
    server_in.sin6_family = AF_INET6;              /* IPv6 (and IPv4) */
    server_in.sin6_addr   = in6addr_any;           /* bind to any address */
    server_in.sin6_port   = htons((uint16_t)port); /* port to bind to */
    if (-1 == bind(server_socket, (struct sockaddr *)&server_in,
                                  sizeof(server_in))) {
        perror("bind()");
        return EXIT_FAILURE;
    }
    /* And accept connections. */
    if (-1 == listen(server_socket, 5)) {
        perror("listen()");
        return EXIT_FAILURE;
    }

    if (LOG_DEBUG <= global_log_level) {
        printf("Listening for connections on port %d.\n", port);

        if (NULL != global_proxy_host && NULL != global_proxy_port) {
            printf("Using proxy: %s:%s.\n", global_proxy_host,
                                            global_proxy_port);
        }
    }

    while (!done) {
        /* Accept new connection. */
        client_socket = accept(server_socket, NULL, NULL);
        if (-1 == client_socket) {
            perror("accept()");
            break;
        }

        /* No lock, we only have one producer! */
        P(ringbuffer_free);
        ringbuffer[ringbuffer_write] = client_socket;
        ringbuffer_write = (ringbuffer_write + 1) % RINGBUFFER_SIZE;
        V(ringbuffer_full);
    }

    close(server_socket);

    /* Poison all threads and shut them down. */
    for (i = 0; i < thread_count; i++) {
        P(ringbuffer_free);
        ringbuffer[ringbuffer_write] = -1; /* poison */
        ringbuffer_write = (ringbuffer_write + 1) % RINGBUFFER_SIZE;
        V(ringbuffer_full);
    }
    for (i = 0; i < thread_count; i++) {
        errno = pthread_join(threads[i], NULL);
        if (0 != errno) {
            perror("pthread_join()");
            continue;
        }
    }

    free(ringbuffer_full);
    free(ringbuffer_free);
    free(ringbuffer_lock);

    free(threads);

    free(global_proxy_host);
    free(global_proxy_port);

    return EXIT_FAILURE;
}

static void sigint_handler(int signal_number) {
    (void)signal_number;

    done = 1;
}

static void parse_arguments(int argc, char **argv) {
    int option;

    /* Default values. */
    thread_count = 10;
#ifdef DEBUG
    global_log_level = LOG_DEBUG;
#else
    global_log_level = LOG_WARNING;
#endif

    while (-1 != (option = getopt(argc, argv, "d:p:t:h?"))) {
        switch (option) {
            case 'd': {
                if (0 > atoi(optarg)) {
                    print_usage(argv[0]);
                    fprintf(stderr, "\n-d positive number required\n");
                    exit(EXIT_FAILURE);
                }
                global_log_level = atoi(optarg);
                break;
            }
            case 'p': {
                char *position;

                /* -p must have the format host:port. */
                if (NULL == (position = strchr(optarg, ':'))
                        || position == optarg
                        || 0 == strlen(position + 1)
                        || 0 >= atoi(position + 1)
                        || 0xffff < atoi(position + 1)) {
                    print_usage(argv[0]);
                    fprintf(stderr, "\ninvalid -p, format host:port\n");
                    exit(EXIT_FAILURE);
                }

                global_proxy_host = malloc((size_t)(position - optarg) + 1);
                if (NULL == global_proxy_host) {
                    perror("malloc()");
                    exit(EXIT_FAILURE);
                }
                memcpy(global_proxy_host, optarg, (size_t)(position - optarg));
                global_proxy_host[position - optarg] = '\0';

                global_proxy_port = malloc(strlen(position + 1) + 1);
                if (NULL == global_proxy_port) {
                    perror("malloc()");
                    exit(EXIT_FAILURE);
                }
                strcpy(global_proxy_port, position + 1);

                break;
            }
            case 't': {
                if (0 >= atoi(optarg)) {
                    print_usage(argv[0]);
                    fprintf(stderr, "\n-t positive number required\n");
                    exit(EXIT_FAILURE);
                }
                thread_count = (size_t)atoi(optarg);
                break;
            }
            case 'h':
            default: /* '?' */
                print_usage(argv[0]);
                exit(EXIT_FAILURE);
        }
    }

    if (optind >= argc) {
        print_usage(argv[0]);
        fprintf(stderr, "\nport missing\n");
        exit(EXIT_FAILURE);
    }
}
static void print_usage(const char *argv) {
    fprintf(stderr, "Usage: %s [-d level] [-p host:port] [-t count] port\n",
                    argv);
    fprintf(stderr, "\n");
    fprintf(stderr, "-d debug level: 0=errors only, 2=debug [default: 1]\n");
    fprintf(stderr, "-p proxy hostname and port\n");
    fprintf(stderr, "-t number of threads [default: 10]\n");
}

static void worker_thread(void) {
    int client_socket;

    for (;;) {
        /* Get next element from ring buffer. */
        P(ringbuffer_full);
        P(ringbuffer_lock);
        client_socket = ringbuffer[ringbuffer_read];
        ringbuffer_read = (ringbuffer_read + 1) % RINGBUFFER_SIZE;
        V(ringbuffer_lock);
        V(ringbuffer_free);

        /* Negative value indicates we should shut down our thread. */
        if (0 > client_socket) {
            break;
        }

        handle_connection(client_socket);
    }
}