root/trunk/wifidog/src/centralserver.c

/********************************************************************\
 * 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 2 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   *
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 * You should have received a copy of the GNU General Public License*
 * along with this program; if not, contact:                        *
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 \********************************************************************/

/* $Id$ */
/** @file centralserver.c
  @brief Functions to talk to the central server (auth/send stats/get rules/etc...)
  @author Copyright (C) 2004 Philippe April <papril777@yahoo.com>
 */

#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <errno.h>
#include <unistd.h>
#include <string.h>
#include <syslog.h>

#include "httpd.h"

#include "common.h"
#include "safe.h"
#include "util.h"
#include "auth.h"
#include "conf.h"
#include "debug.h"
#include "centralserver.h"
#include "firewall.h"
#include "../config.h"

extern pthread_mutex_t  config_mutex;

/** Initiates a transaction with the auth server, either to authenticate or to
 * update the traffic counters at the server
@param authresponse Returns the information given by the central server 
@param request_type Use the REQUEST_TYPE_* defines in centralserver.h
@param ip IP adress of the client this request is related to
@param mac MAC adress of the client this request is related to
@param token Authentification token of the client
@param incoming Current counter of the client's total incoming traffic, in bytes 
@param outgoing Current counter of the client's total outgoing traffic, in bytes 
*/
t_authcode
auth_server_request(t_authresponse *authresponse, const char *request_type, const char *ip, const char *mac, const char *token, unsigned long long int incoming, unsigned long long int outgoing)
{
        int sockfd;
        ssize_t numbytes;
        size_t totalbytes;
        char buf[MAX_BUF];
        char *tmp;
        char *safe_token;
        int done, nfds;
        fd_set                  readfds;
        struct timeval          timeout;
        t_auth_serv     *auth_server = NULL;
        auth_server = get_auth_server();
        
        /* Blanket default is error. */
        authresponse->authcode = AUTH_ERROR;
        
        sockfd = connect_auth_server();
        if (sockfd == -1) {
                /* Could not connect to any auth server */
                return (AUTH_ERROR);
        }

        /**
         * TODO: XXX change the PHP so we can harmonize stage as request_type
         * everywhere.
         */
        memset(buf, 0, sizeof(buf));
        safe_token=httpdUrlEncode(token);
        snprintf(buf, (sizeof(buf) - 1),
                "GET %s%sstage=%s&ip=%s&mac=%s&token=%s&incoming=%llu&outgoing=%llu&gw_id=%s HTTP/1.0\r\n"
                "User-Agent: WiFiDog %s\r\n"
                "Host: %s\r\n"
                "\r\n",
                auth_server->authserv_path,
                auth_server->authserv_auth_script_path_fragment,
                request_type,
                ip,
                mac,
                safe_token,
                incoming,
                outgoing,
                config_get_config()->gw_id,
                VERSION,
                auth_server->authserv_hostname
        );

        free(safe_token);

        debug(LOG_DEBUG, "Sending HTTP request to auth server: [%s]\n", buf);
        send(sockfd, buf, strlen(buf), 0);

        debug(LOG_DEBUG, "Reading response");
        numbytes = totalbytes = 0;
        done = 0;
        do {
                FD_ZERO(&readfds);
                FD_SET(sockfd, &readfds);
                timeout.tv_sec = 30; /* XXX magic... 30 second is as good a timeout as any */
                timeout.tv_usec = 0;
                nfds = sockfd + 1;

                nfds = select(nfds, &readfds, NULL, NULL, &timeout);

                if (nfds > 0) {
                        /** We don't have to use FD_ISSET() because there
                         *  was only one fd. */
                        numbytes = read(sockfd, buf + totalbytes, MAX_BUF - (totalbytes + 1));
                        if (numbytes < 0) {
                                debug(LOG_ERR, "An error occurred while reading from auth server: %s", strerror(errno));
                                /* FIXME */
                                close(sockfd);
                                return (AUTH_ERROR);
                        }
                        else if (numbytes == 0) {
                                done = 1;
                        }
                        else {
                                totalbytes += numbytes;
                                debug(LOG_DEBUG, "Read %d bytes, total now %d", numbytes, totalbytes);
                        }
                }
                else if (nfds == 0) {
                        debug(LOG_ERR, "Timed out reading data via select() from auth server");
                        /* FIXME */
                        close(sockfd);
                        return (AUTH_ERROR);
                }
                else if (nfds < 0) {
                        debug(LOG_ERR, "Error reading data via select() from auth server: %s", strerror(errno));
                        /* FIXME */
                        close(sockfd);
                        return (AUTH_ERROR);
                }
        } while (!done);

        close(sockfd);

        buf[totalbytes] = '\0';
        debug(LOG_DEBUG, "HTTP Response from Server: [%s]", buf);
        
        if ((tmp = strstr(buf, "Auth: "))) {
                if (sscanf(tmp, "Auth: %d", (int *)&authresponse->authcode) == 1) {
                        debug(LOG_INFO, "Auth server returned authentication code %d", authresponse->authcode);
                        return(authresponse->authcode);
                } else {
                        debug(LOG_WARNING, "Auth server did not return expected authentication code");
                        return(AUTH_ERROR);
                }
        }
        else {
                return(AUTH_ERROR);
        }

        /* XXX Never reached because of the above if()/else pair. */
        return(AUTH_ERROR);
}

/* Tries really hard to connect to an auth server. Returns a file descriptor, -1 on error
 */
int connect_auth_server() {
        int sockfd;

        LOCK_CONFIG();
        sockfd = _connect_auth_server(0);
        UNLOCK_CONFIG();

        if (sockfd == -1) {
                debug(LOG_ERR, "Failed to connect to any of the auth servers");
                mark_auth_offline();
        }
        else {
                debug(LOG_DEBUG, "Connected to auth server");
                mark_auth_online();
        }
        return (sockfd);
}

/* Helper function called by connect_auth_server() to do the actual work including recursion
 * DO NOT CALL DIRECTLY
 @param level recursion level indicator must be 0 when not called by _connect_auth_server()
 */
int _connect_auth_server(int level) {
        s_config *config = config_get_config();
        t_auth_serv *auth_server = NULL;
        struct in_addr *h_addr;
        int num_servers = 0;
        char * hostname = NULL;
        char * popular_servers[] = {
                  "www.google.com",
                  "www.yahoo.com",
                  NULL
        };
        char ** popularserver;
        char * ip;
        struct sockaddr_in their_addr;
        int sockfd;

        /* XXX level starts out at 0 and gets incremented by every iterations. */
        level++;

        /*
         * Let's calculate the number of servers we have
         */
        for (auth_server = config->auth_servers; auth_server; auth_server = auth_server->next) {
                num_servers++;
        }
        debug(LOG_DEBUG, "Level %d: Calculated %d auth servers in list", level, num_servers);

        if (level > num_servers) {
                /*
                 * We've called ourselves too many times
                 * This means we've cycled through all the servers in the server list
                 * at least once and none are accessible
                 */
                return (-1);
        }

        /*
         * Let's resolve the hostname of the top server to an IP address
         */
        auth_server = config->auth_servers;
        hostname = auth_server->authserv_hostname;
        debug(LOG_DEBUG, "Level %d: Resolving auth server [%s]", level, hostname);
        h_addr = wd_gethostbyname(hostname);
        if (!h_addr) {
                /*
                 * DNS resolving it failed
                 *
                 * Can we resolve any of the popular servers ?
                 */
                debug(LOG_DEBUG, "Level %d: Resolving auth server [%s] failed", level, hostname);

                for (popularserver = popular_servers; *popularserver; popularserver++) {
                        debug(LOG_DEBUG, "Level %d: Resolving popular server [%s]", level, *popularserver);
                        h_addr = wd_gethostbyname(*popularserver);
                        if (h_addr) {
                                debug(LOG_DEBUG, "Level %d: Resolving popular server [%s] succeeded = [%s]", level, *popularserver, inet_ntoa(*h_addr));
                                break;
                        }
                        else {
                                debug(LOG_DEBUG, "Level %d: Resolving popular server [%s] failed", level, *popularserver);
                        }
                }

                /* 
                 * If we got any h_addr buffer for one of the popular servers, in other
                 * words, if one of the popular servers resolved, we'll assume the DNS
                 * works, otherwise we'll deal with net connection or DNS failure.
                 */
                if (h_addr) {
                        free (h_addr);
                        /*
                         * Yes
                         *
                         * The auth server's DNS server is probably dead. Try the next auth server
                         */
                        debug(LOG_DEBUG, "Level %d: Marking auth server [%s] as bad and trying next if possible", level, hostname);
                        if (auth_server->last_ip) {
                                free(auth_server->last_ip);
                                auth_server->last_ip = NULL;
                        }
                        mark_auth_server_bad(auth_server);
                        return _connect_auth_server(level);
                }
                else {
                        /*
                         * No
                         *
                         * It's probably safe to assume that the internet connection is malfunctioning
                         * and nothing we can do will make it work
                         */
                        mark_offline();
                        debug(LOG_DEBUG, "Level %d: Failed to resolve auth server and all popular servers. "
                                        "The internet connection is probably down", level);
                        return(-1);
                }
        }
        else {
                /*
                 * DNS resolving was successful
                 */
                ip = safe_strdup(inet_ntoa(*h_addr));
                debug(LOG_DEBUG, "Level %d: Resolving auth server [%s] succeeded = [%s]", level, hostname, ip);

                if (!auth_server->last_ip || strcmp(auth_server->last_ip, ip) != 0) {
                        /*
                         * But the IP address is different from the last one we knew
                         * Update it
                         */
                        debug(LOG_DEBUG, "Level %d: Updating last_ip IP of server [%s] to [%s]", level, hostname, ip);
                        if (auth_server->last_ip) free(auth_server->last_ip);
                        auth_server->last_ip = ip;

                        /* Update firewall rules */
                        fw_clear_authservers();
                        fw_set_authservers();
                }
                else {
                        /*
                         * IP is the same as last time
                         */
                        free(ip);
                }

                /*
                 * Connect to it
                 */
                debug(LOG_DEBUG, "Level %d: Connecting to auth server %s:%d", level, hostname, auth_server->authserv_http_port);
                their_addr.sin_family = AF_INET;
                their_addr.sin_port = htons(auth_server->authserv_http_port);
                their_addr.sin_addr = *h_addr;
                memset(&(their_addr.sin_zero), '\0', sizeof(their_addr.sin_zero));
                free (h_addr);

                if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
                        debug(LOG_ERR, "Level %d: Failed to create a new SOCK_STREAM socket: %s", strerror(errno));
                        return(-1);
                }

                if (connect(sockfd, (struct sockaddr *)&their_addr, sizeof(struct sockaddr)) == -1) {
                        /*
                         * Failed to connect
                         * Mark the server as bad and try the next one
                         */
                        debug(LOG_DEBUG, "Level %d: Failed to connect to auth server %s:%d (%s). Marking it as bad and trying next if possible", level, hostname, auth_server->authserv_http_port, strerror(errno));
                        close(sockfd);
                        mark_auth_server_bad(auth_server);
                        return _connect_auth_server(level); /* Yay recursion! */
                }
                else {
                        /*
                         * We have successfully connected
                         */
                        debug(LOG_DEBUG, "Level %d: Successfully connected to auth server %s:%d", level, hostname, auth_server->authserv_http_port);
                        return sockfd;
                }
        }
}