RetroArch/network/netplay/netplay_discovery.c

/*  RetroArch - A frontend for libretro.
 *  Copyright (C)      2016 - Gregor Richards
 * 
 *  RetroArch 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 Found-
 *  ation, either version 3 of the License, or (at your option) any later version.
 *
 *  RetroArch 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 RetroArch.
 *  If not, see <http://www.gnu.org/licenses/>.
 */

/*
 * AD PACKET FORMAT:
 *
 * Request:
 *    1 word: RANQ (RetroArch Netplay Query)
 *    1 word: Netplay protocol version
 *
 * Reply:
 *    1 word : RANS (RetroArch Netplay Server)
 *    1 word : Netplay protocol version
 *    1 word : Port
 *    8 words: RetroArch version
 *    8 words: Nick
 *    8 words: Core name
 *    8 words: Core version
 *    8 words: Content name (currently always blank)
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <compat/strl.h>
#include <net/net_compat.h>

#include "../../runloop.h"
#include "../../version.h"
#include "netplay.h"
#include "netplay_discovery.h"
#include "netplay_private.h"

#if defined(AF_INET6) && !defined(HAVE_SOCKET_LEGACY)
#define HAVE_INET6 1
#endif

struct ad_packet
{
   uint32_t header;
   uint32_t protocol_version;
   uint32_t port;
   char retroarch_version[NETPLAY_HOST_STR_LEN];
   char nick[NETPLAY_HOST_STR_LEN];
   char core[NETPLAY_HOST_STR_LEN];
   char core_version[NETPLAY_HOST_STR_LEN];
   char content[NETPLAY_HOST_STR_LEN];
};

bool netplay_lan_ad_client(void);

/* LAN discovery sockets */
static int lan_ad_server_fd = -1;
static int lan_ad_client_fd = -1;

/* Packet buffer for advertisement and responses */
static struct ad_packet ad_packet_buffer;

/* List of discovered hosts */
static struct netplay_host_list discovered_hosts;
static size_t discovered_hosts_allocated;

/** Initialize Netplay discovery (client) */
bool init_netplay_discovery(void)
{
   struct addrinfo *addr = NULL;
   int fd = socket_init((void **) &addr, 0, NULL, SOCKET_TYPE_DATAGRAM);

   if (fd < 0)
      goto error;

   if (!socket_bind(fd, (void*)addr))
   {
      socket_close(fd);
      goto error;
   }

   lan_ad_client_fd = fd;
   freeaddrinfo_retro(addr);
   return true;

error:
   if (addr)
      freeaddrinfo_retro(addr);
   RARCH_ERR("Failed to initialize netplay advertisement client socket.\n");
   return false;
}

/** Deinitialize and free Netplay discovery */
void deinit_netplay_discovery(void)
{
   if (lan_ad_client_fd >= 0)
   {
      socket_close(lan_ad_client_fd);
      lan_ad_client_fd = -1;
   }
}

/** Discovery control */
bool netplay_discovery_driver_ctl(enum rarch_netplay_discovery_ctl_state state, void *data)
{
   char port_str[6];

   if (lan_ad_client_fd < 0)
      return false;

   switch (state)
   {
      case RARCH_NETPLAY_DISCOVERY_CTL_LAN_SEND_QUERY:
      {
         struct addrinfo hints = {0}, *addr;
         int canBroadcast = 1;

         /* Get the broadcast address (IPv4 only for now) */
         snprintf(port_str, 6, "%hu", (unsigned short) RARCH_DEFAULT_PORT);
         if (getaddrinfo_retro("255.255.255.255", port_str, &hints, &addr) < 0)
            return false;

         /* Make it broadcastable */
#if defined(SOL_SOCKET) && defined(SO_BROADCAST)
         if (setsockopt(lan_ad_client_fd, SOL_SOCKET, SO_BROADCAST, (const char *) &canBroadcast, sizeof(canBroadcast)) < 0)
             RARCH_WARN("Failed to set netplay discovery port to broadcast.\n");
#endif

         /* Put together the request */
         memcpy((void *) &ad_packet_buffer, "RANQ", 4);
         ad_packet_buffer.protocol_version = htonl(NETPLAY_PROTOCOL_VERSION);

         /* And send it off */
         if (sendto(lan_ad_client_fd, (const char *) &ad_packet_buffer,
            2*sizeof(uint32_t), 0, addr->ai_addr, addr->ai_addrlen) <
            2*sizeof(uint32_t))
            RARCH_WARN("Failed to send netplay discovery response.\n");

         freeaddrinfo_retro(addr);
         break;
      }

      case RARCH_NETPLAY_DISCOVERY_CTL_LAN_GET_RESPONSES:
         if (!netplay_lan_ad_client())
            return false;
         *((struct netplay_host_list **) data) = &discovered_hosts;
         break;

      case RARCH_NETPLAY_DISCOVERY_CTL_LAN_CLEAR_RESPONSES:
         discovered_hosts.size = 0;
         break;

      default:
         return false;
   }

   return true;
}

static bool init_lan_ad_server_socket(netplay_t *netplay, uint16_t port)
{
   struct addrinfo *addr = NULL;
   int fd = socket_init((void **) &addr, port, NULL, SOCKET_TYPE_DATAGRAM);

   if (fd < 0)
      goto error;

   if (!socket_bind(fd, (void*)addr))
   {
      socket_close(fd);
      goto error;
   }

   lan_ad_server_fd = fd;
   freeaddrinfo_retro(addr);

   return true;

error:
   if (addr)
      freeaddrinfo_retro(addr);
   RARCH_ERR("Failed to initialize netplay advertisement socket.\n");
   return false;
}

/**
 * netplay_lan_ad_server
 *
 * Respond to any LAN ad queries that the netplay server has received.
 */
bool netplay_lan_ad_server(netplay_t *netplay)
{
   fd_set fds;
   struct timeval tmp_tv = {0};
   struct sockaddr their_addr;
   socklen_t addr_size;
   rarch_system_info_t *info = NULL;

   if (lan_ad_server_fd < 0 && !init_lan_ad_server_socket(netplay, RARCH_DEFAULT_PORT))
       return false;

   /* Check for any ad queries */
   while (1)
   {
      FD_ZERO(&fds);
      FD_SET(lan_ad_server_fd, &fds);
      if (socket_select(lan_ad_server_fd + 1, &fds, NULL, NULL, &tmp_tv) <= 0)
         break;
      if (!FD_ISSET(lan_ad_server_fd, &fds))
         break;

      /* Somebody queried, so check that it's valid */
      addr_size = sizeof(their_addr);
      if (recvfrom(lan_ad_server_fd, (char*)&ad_packet_buffer,
            sizeof(struct ad_packet), 0, &their_addr, &addr_size) >=
            (ssize_t) (2*sizeof(uint32_t)))
      {
         /* Make sure it's a valid query */
         if (memcmp((void *) &ad_packet_buffer, "RANQ", 4))
            continue;

         /* For this version */
         if (ntohl(ad_packet_buffer.protocol_version) !=
               NETPLAY_PROTOCOL_VERSION)
            continue;

         runloop_ctl(RUNLOOP_CTL_SYSTEM_INFO_GET, &info);

         /* Now build our response */
         memset(&ad_packet_buffer, 0, sizeof(struct ad_packet));
         memcpy(&ad_packet_buffer, "RANS", 4);
         ad_packet_buffer.protocol_version =
            htonl(NETPLAY_PROTOCOL_VERSION);
         ad_packet_buffer.port = htonl(netplay->tcp_port);
         strlcpy(ad_packet_buffer.retroarch_version, PACKAGE_VERSION,
            NETPLAY_HOST_STR_LEN);
         strlcpy(ad_packet_buffer.nick, netplay->nick, NETPLAY_HOST_STR_LEN);
         if (info)
         {
            strlcpy(ad_packet_buffer.core, info->info.library_name,
               NETPLAY_HOST_STR_LEN);
            strlcpy(ad_packet_buffer.core_version, info->info.library_version,
               NETPLAY_HOST_STR_LEN);
         }

         /* And send it */
         sendto(lan_ad_server_fd, (const char*)&ad_packet_buffer,
            sizeof(struct ad_packet), 0, &their_addr, addr_size);
      }
   }

   return true;
}

#ifdef HAVE_SOCKET_LEGACY
/* The fact that I need to write this is deeply depressing */
static int16_t htons_for_morons(int16_t value)
{
   union {
      int32_t l;
      int16_t s[2];
   } val;
   val.l = htonl(value);
   return val.s[1];
}
#ifndef htons
#define htons htons_for_morons
#endif
#endif

bool netplay_lan_ad_client(void)
{
   fd_set fds;
   struct timeval tmp_tv = {0};
   struct sockaddr their_addr;
   socklen_t addr_size;

   if (lan_ad_client_fd < 0)
       return false;

   /* Check for any ad queries */
   while (1)
   {
      FD_ZERO(&fds);
      FD_SET(lan_ad_client_fd, &fds);
      if (socket_select(lan_ad_client_fd + 1, &fds, NULL, NULL, &tmp_tv) <= 0)
         break;
      if (!FD_ISSET(lan_ad_client_fd, &fds))
         break;

      /* Somebody queried, so check that it's valid */
      addr_size = sizeof(their_addr);
      if (recvfrom(lan_ad_client_fd, (char*)&ad_packet_buffer,
            sizeof(struct ad_packet), 0, &their_addr, &addr_size) >=
            (ssize_t) sizeof(struct ad_packet))
      {
         struct netplay_host *host;

         /* Make sure it's a valid response */
         if (memcmp((void *) &ad_packet_buffer, "RANS", 4))
            continue;

         /* For this version */
         if (ntohl(ad_packet_buffer.protocol_version) != NETPLAY_PROTOCOL_VERSION)
            continue;

         /* And that we know how to handle it */
         if (their_addr.sa_family == AF_INET)
         {
            struct sockaddr_in *sin = (struct sockaddr_in *) &their_addr;
            sin->sin_port = htons(ntohl(ad_packet_buffer.port));

         }
#ifdef HAVE_INET6
         else if (their_addr.sa_family == AF_INET6)
         {
            struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *) &their_addr;
            sin6->sin6_port = htons(ad_packet_buffer.port);

         }
#endif
         else continue;

         /* Allocate space for it */
         if (discovered_hosts.size >= discovered_hosts_allocated)
         {
            size_t allocated = discovered_hosts_allocated;
            struct netplay_host *new_hosts;

            if (allocated == 0) allocated = 2;
            else allocated *= 2;

            if (discovered_hosts.hosts)
               new_hosts = (struct netplay_host *)
                  realloc(discovered_hosts.hosts, allocated * sizeof(struct
                  netplay_host));
            else
               /* Should be equivalent to realloc, but I don't trust screwy libcs */
               new_hosts = (struct netplay_host *)
                  malloc(allocated * sizeof(struct netplay_host));

            if (!new_hosts)
               return false;

            discovered_hosts.hosts = new_hosts;
            discovered_hosts_allocated = allocated;
         }

         /* Get our host structure */
         host = &discovered_hosts.hosts[discovered_hosts.size++];

         /* Copy in the response */
         memset(host, 0, sizeof(struct netplay_host));
         host->addr = their_addr;
         host->addrlen = addr_size;
         strlcpy(host->nick, ad_packet_buffer.nick, NETPLAY_HOST_STR_LEN);
         strlcpy(host->core, ad_packet_buffer.core, NETPLAY_HOST_STR_LEN);
         strlcpy(host->core_version, ad_packet_buffer.core_version,
            NETPLAY_HOST_STR_LEN);
         strlcpy(host->content, ad_packet_buffer.content,
            NETPLAY_HOST_STR_LEN);
         host->nick[NETPLAY_HOST_STR_LEN-1] =
            host->core[NETPLAY_HOST_STR_LEN-1] =
            host->core_version[NETPLAY_HOST_STR_LEN-1] =
            host->content[NETPLAY_HOST_STR_LEN-1] = '\0';
      }
   }

   return true;
}