/**
 * ddos/server.c
 * Copyright (C) 2008 Markus Broeker
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netdb.h>
#include <netinet/in.h>
#include <signal.h>

int set_proc_limit (int);

#define SVPORT "4000"
#define MAXLEN 1024
#define MAXMEM 200

int server_write (int client_socket, char *s)
{
    if (s == NULL) {
        fprintf (stderr, "Invalid data: s == NULL");
        return -1;
    }

    return write (client_socket, s, strlen (s));
}

int server_init (char *port)
{
    int server_socket, status;
    struct addrinfo hints;
    struct addrinfo *result, *rp;

    int yes = 1, no = 0;

    memset (&hints, 0, sizeof (hints));
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_flags = AI_PASSIVE;

    if (getaddrinfo (NULL, "4000", &hints, &result) < 0) {
        perror ("GETADDRINFO");
        return -1;
    }

    server_socket = -1;
    for (rp = result; rp != NULL; rp = rp->ai_next) {
        if ((server_socket = socket (rp->ai_family, rp->ai_socktype, rp->ai_protocol)) < 0) {
            perror ("SOCKET");
            continue;
        }
        // enable rebinding of the socket
        if (setsockopt (server_socket, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof (int)) == -1) {
            perror ("setsockopt");
            return -1;
        }
        // disable IPV6ONLY, eg enable an hybrid socket
        if (rp->ai_family == AF_INET6)
            if (setsockopt (server_socket, IPPROTO_IPV6, IPV6_V6ONLY, &no, sizeof (int)) == -1)
                perror ("setsockopt");

        if ((bind (server_socket, rp->ai_addr, rp->ai_addrlen)) == -1) {
            perror ("BIND");
            close (server_socket);
            server_socket = -1;
        } else {
            printf ("bound to an %s socket on port %s\n", (rp->ai_family == AF_INET6) ? "IPv6" : "IPv4", port);
        }
    }

    status = listen (server_socket, 10);

    if (status != 0) {
        perror ("LISTEN");
        return -1;
    }

    if (result != NULL)
        freeaddrinfo (result);

    return server_socket;
}

int main (int argc, char **argv)
{
    int server_socket;
    int client_socket;

    char message[MAXLEN + 1];
    int len;

    pid_t pid;
    pid_t parent_pid;

    if ((server_socket = server_init (SVPORT)) < 0)
        return EXIT_FAILURE;

    int links = 0;

    parent_pid = getpid ();

    /*
     * Child quits immediately, father mustn't wait
     */
    signal (SIGCHLD, SIG_IGN);

    if (set_proc_limit (200) != 0) {
        printf ("Cannot set the process limit\n");
        return EXIT_FAILURE;
    }

    for (;;) {
        client_socket = accept (server_socket, NULL, NULL);

        printf ("PARENT PID = %d\n", parent_pid);

        pid = fork ();
        switch (pid) {
        case 0:                /* Child */
            close (server_socket);
            if ((len = read (client_socket, message, MAXLEN)) == -1)
                break;
            message[len] = '\0';

            len = server_write (client_socket, "Please wait...\r\n");
            sleep (10);

            printf ("DELETING LINK [%04d] %04d\n", getpid (), links--);
            shutdown (client_socket, SHUT_RDWR);
            close (client_socket);
            return 1;
        case -1:
            perror ("Fork Error");
            close (client_socket);
            /*
             * server is still alive and will continue when resources are available
             */
            break;
        default:               /* PID > 0 */
            close (client_socket);
            printf ("Starting LINK [%04d] %04d\n", pid, links++);
        }
    }

    return close (server_socket);
}