path: root/src/server.c

/*
 *   NetCosm - a MUD server
 *   Copyright (C) 2016 Franklin Wei
 *
 *   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 "netcosm.h"

#define PORT 1234
#define BACKLOG 16

/* global data */
bool are_child = false;
void *child_map = NULL;

/* assume int is atomic */
volatile int num_clients = 0;

/* local data */
static uint16_t port;

static int server_socket;

void __attribute__((noreturn)) error(const char *fmt, ...)
{
    char buf[128];
    memset(buf, 0, sizeof(buf));
    va_list ap;
    va_start(ap, fmt);
    vsnprintf(buf, sizeof(buf), fmt, ap);
    va_end(ap);
    perror(buf);
    exit(EXIT_FAILURE);
}

static void free_child_data(void *ptr)
{
    struct child_data *child = ptr;
    if(child->user)
        free(child->user);
    free(ptr);
}

static void handle_disconnects(void)
{
    int saved_errno = errno;

    pid_t pid;
    while((pid = waitpid(-1, NULL, WNOHANG)) > 0)
    {
        sig_debugf("Client disconnect.\n");
        struct child_data *child = hash_lookup(child_map, &pid);
        ev_io_stop(child->loop, child->io_watcher);
        free(child->io_watcher);

        --num_clients;

        hash_remove(child_map, &pid);
    }

    errno = saved_errno;
}

static void sigchld_handler(int s)
{
    (void) s;
    handle_disconnects();
}

static void handle_client(int fd, struct sockaddr_in *addr,
                          int nclients, int to, int from)
{
    client_main(fd, addr, nclients, to, from);
}

static void __attribute__((noreturn)) serv_cleanup(void)
{
    sig_debugf("Shutdown server.\n");

    if(shutdown(server_socket, SHUT_RDWR) > 0)
        error("shutdown");
    close(server_socket);

    world_free();

    reqmap_free();

    hash_free(child_map);
    child_map = NULL;
    ev_default_destroy();

    userdb_shutdown();

    _exit(0);
}

static void __attribute__((noreturn)) sigint_handler(int s)
{
    (void) s;
    serv_cleanup();
}

static void init_signals(void)
{
    struct sigaction sa;

    sigemptyset(&sa.sa_mask);
    sigaddset(&sa.sa_mask, SIGCHLD);
    sa.sa_handler = sigchld_handler;
    sa.sa_flags = SA_RESTART;
    if(sigaction(SIGCHLD, &sa, NULL) < 0)
        error("sigaction");

    sigemptyset(&sa.sa_mask);
    sigaddset(&sa.sa_mask, SIGINT);
    sa.sa_handler = sigint_handler;
    sa.sa_flags = SA_RESTART;
    if(sigaction(SIGINT, &sa, NULL) < 0)
        error("sigaction");
    if(sigaction(SIGTERM, &sa, NULL) < 0)
        error("sigaction");

    sigemptyset(&sa.sa_mask);
    sigaddset(&sa.sa_mask, SIGRTMIN+1);
    sa.sa_sigaction = master_ack_handler;
    sa.sa_flags = SA_SIGINFO | SA_RESTART;
    if(sigaction(SIGRTMIN+1, &sa, NULL) < 0)
        error("sigaction");

    sigemptyset(&sa.sa_mask);
    sigaddset(&sa.sa_mask, SIGPIPE);
    sa.sa_handler = SIG_IGN;
    sa.sa_flags = SA_RESTART;
    if(sigaction(SIGPIPE, &sa, NULL) < 0)
        error("sigaction");

    /* we set this now so there's no race condition after a fork() */
    sigemptyset(&sa.sa_mask);
    sigaddset(&sa.sa_mask, SIGRTMIN);
    sigaddset(&sa.sa_mask, SIGPIPE);
    sa.sa_sigaction = sig_rt_0_handler;
    sa.sa_flags = SA_RESTART | SA_SIGINFO;
    if(sigaction(SIGRTMIN, &sa, NULL) < 0)
        error("sigaction");
}

static void check_userfile(void)
{
    if(access(USERFILE, F_OK) < 0 || userdb_size() == 0)
        first_run_setup();

    if(access(USERFILE, R_OK | W_OK) < 0)
        error("cannot access "USERFILE);
}

static void load_worldfile(void)
{
    if(access(WORLDFILE, F_OK) < 0)
    {
        world_init(netcosm_world, netcosm_world_sz, netcosm_world_name);

        world_save(WORLDFILE);
    }
    else if(access(WORLDFILE, R_OK | W_OK) < 0)
        error("cannot access "WORLDFILE);
    else
        if(!world_load(WORLDFILE, netcosm_world, netcosm_world_sz, netcosm_world_name))
            error("Failed to load world from disk.\nTry removing "WORLDFILE".\n");
}

static int server_bind(void)
{
    int sock = socket(AF_INET, SOCK_STREAM, 0);

    if(sock<0)
        error("socket");

    int tmp = 1;

    if(setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &tmp, sizeof tmp) < 0)
        error("setsockopt");

    struct sockaddr_in addr;
    addr.sin_family = AF_INET;
    addr.sin_port = htons(port);

    addr.sin_addr.s_addr = htonl(INADDR_ANY);

    if(bind(sock, (struct sockaddr*) &addr, sizeof addr) < 0)
        error("bind");

    if(listen(sock, BACKLOG) < 0)
        error("listen");

    return sock;
}

static SIMP_HASH(pid_t, pid_hash);
static SIMP_EQUAL(pid_t, pid_equal);

static void childreq_cb(EV_P_ ev_io *w, int revents)
{
    (void) EV_A;
    (void) w;
    (void) revents;
    /* data from a child's pipe */
    if(!handle_child_req(w->fd))
    {
        handle_disconnects();
    }
}

static void new_connection_cb(EV_P_ ev_io *w, int revents)
{
    (void) EV_A;
    (void) w;
    (void) revents;
    struct sockaddr_in client;
    socklen_t client_len = sizeof(client);
    int new_sock = accept(server_socket, (struct sockaddr*) &client, &client_len);
    if(new_sock < 0)
        error("accept");

    ++num_clients;

    int readpipe[2]; /* child->parent */
    int outpipe [2]; /* parent->child */

    if(pipe(readpipe) < 0)
        error("pipe");
    if(pipe(outpipe) < 0)
        error("pipe");

    int flags = fcntl(outpipe[0], F_GETFL, 0);
    if(fcntl(outpipe[0], F_SETFL, flags | O_NONBLOCK) < 0)
        error("fcntl");

    pid_t pid = fork();
    if(pid < 0)
        error("fork");

    if(!pid)
    {
        /* child */
        are_child = true;
        close(readpipe[0]);
        close(outpipe[1]);
        close(server_socket);

        /* only the master process controls the world */
        world_free();
        reqmap_free();
        hash_free(child_map);
        child_map = NULL;

        /* we don't need libev anymore */
        ev_default_destroy();

        /* user DB requests go through the master */
        userdb_shutdown();

        debugf("Child with PID %d spawned\n", getpid());

        server_socket = new_sock;

        handle_client(new_sock, &client, num_clients, readpipe[1], outpipe[0]);

        exit(0);
    }
    else
    {
        /* parent */
        close(readpipe[1]);
        close(outpipe[0]);
        close(new_sock);

        /* add the child to the child map */
        struct child_data *new = calloc(1, sizeof(struct child_data));
        memcpy(new->outpipe, outpipe, sizeof(outpipe));
        memcpy(new->readpipe, readpipe, sizeof(readpipe));
        new->addr = client.sin_addr;
        new->pid = pid;
        new->state = STATE_INIT;
        new->user = NULL;

        ev_io *new_io_watcher = calloc(1, sizeof(ev_io));
        ev_io_init(new_io_watcher, childreq_cb, new->readpipe[0], EV_READ);
        ev_io_start(EV_A_ new_io_watcher);
        new->io_watcher = new_io_watcher;

        new->loop = loop;

        pid_t *pidbuf = malloc(sizeof(pid_t));
        *pidbuf = pid;

        hash_insert(child_map, pidbuf, new);
    }
}

int main(int argc, char *argv[])
{
    if(argc != 2)
        port = PORT;
    else
        port = strtol(argv[1], NULL, 0);

    srand(time(0));

    server_socket = server_bind();
    userdb_init(USERFILE);

    check_userfile();

    load_worldfile();

    reqmap_init();

    /* this initial size very low to make iteration faster */
    child_map = hash_init(16, pid_hash, pid_equal);
    hash_setfreedata_cb(child_map, free_child_data);
    hash_setfreekey_cb(child_map, free);

    debugf("Listening on port %d\n", port);

    struct ev_loop *loop = ev_default_loop(0);

    /* set up signal handlers AFTER creating the default loop, because it will grab SIGCHLD */
    init_signals();

    ev_io server_watcher;
    ev_io_init(&server_watcher, new_connection_cb, server_socket, EV_READ);
    ev_io_start(EV_A_ &server_watcher);

    ev_loop(loop, 0);

    /* should never get here */
    error("unexpected termination");
}