network.c

   1 /* Utility functions to redirect stdin, stdout, stderr to sockets. */
   2
   3 #define DEBUG
   4 #include <stdio.h>
   5 #include <string.h>
   6 #include <stdlib.h>
   7 #include <stdbool.h>
   8 #include <assert.h>
   9 #include <unistd.h>
  10 #include <errno.h>
  11 #include <pthread.h>
  12 #include <sys/types.h>
  13
  14 #ifdef _WIN32
  15 #include <winsock2.h>
  16 #include <ws2tcpip.h>
  17 #else
  18 #include <sys/socket.h>
  19 #include <netdb.h>
  20 #endif
  21
  22 #include "debug.h"
  23 #include "util.h"
  24
  25 #define STDIN  0
  26 #define STDOUT 1
  27 #define STDERR 2
  28
  29 #define BSIZE 4096
  30
  31 static inline void
  32 die(char *msg)
  33 {
  34         perror(msg);
  35         exit(42);
  36 }
  37
  38 /* Create a socket, bind to it on the given port and listen.
  39  * This function is restricted to server mode (port has
  40  * no hostname). Returns the socket. */
  41 int
  42 port_listen(char *port, int max_connections)
  43 {
  44         int sock = socket(AF_INET, SOCK_STREAM, 0);
  45         if (sock == -1)
  46                 die("socket");
  47
  48         struct sockaddr_in server_addr;
  49         memset(&server_addr, 0, sizeof(server_addr));
  50         server_addr.sin_family = AF_INET;
  51         server_addr.sin_port = htons(atoi(port));
  52         server_addr.sin_addr.s_addr = INADDR_ANY;
  53
  54         const char val = 1;
  55         if (setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val)))
  56                 die("setsockopt");
  57         if (bind(sock, (struct sockaddr *)&server_addr, sizeof(struct sockaddr)) == -1)
  58                 die("bind");
  59         if (listen(sock, max_connections) == -1)
  60                 die("listen");
  61         return sock;
  62 }
  63
  64 /* Returns true if in private address range: 10.0.0.0/8 172.16.0.0/12 192.168.0.0/16 */
  65 static bool
  66 is_private(struct in_addr *in)
  67 {
  68         return (ntohl(in->s_addr) & 0xff000000) >> 24 == 10
  69             || (ntohl(in->s_addr) & 0xfff00000) >> 16 == 172 * 256 + 16
  70             || (ntohl(in->s_addr) & 0xffff0000) >> 16 == 192 * 256 + 168;
  71 }
  72
  73 /* Waits for a connection on the given socket, and returns the file descriptor.
  74  * Updates the client address if it is not null.
  75  * WARNING: the connection is not authenticated. As a weak security measure,
  76  * the connections are limited to a private network. */
  77 int
  78 open_server_connection(int socket, struct in_addr *client)
  79 {
  80         assert(socket >= 0);
  81         for (;;) {
  82                 struct sockaddr_in client_addr;
  83                 int sin_size = sizeof(struct sockaddr_in);
  84                 int fd = accept(socket, (struct sockaddr *)&client_addr, (socklen_t *)&sin_size);
  85                 if (fd == -1) {
  86                         die("accept");
  87                 }
  88                 if (is_private(&client_addr.sin_addr)) {
  89                         if (client)
  90                                 *client = client_addr.sin_addr;
  91                         return fd;
  92                 }
  93                 close(fd);
  94         }
  95 }
  96
  97 /* Opens a new connection to the given port name, which must
  98  * contain a host name. Returns the open file descriptor,
  99  * or -1 if the open fails. */
 100 static int
 101 open_client_connection(char *port_name)
 102 {
 103         char hostname[BSIZE];
 104         strncpy(hostname, port_name, sizeof(hostname));
 105         char *port = strchr(hostname, ':');
 106         assert(port);
 107         *port++ = '\0';
 108
 109         struct hostent *host = gethostbyname(hostname);
 110         if (!host)
 111                 return -1;
 112         int sock = socket(AF_INET, SOCK_STREAM, 0);
 113         if (sock == -1)
 114                 die("socket");
 115         struct sockaddr_in sin;
 116         memcpy(&sin.sin_addr.s_addr, host->h_addr, host->h_length);
 117         sin.sin_family = AF_INET;
 118         sin.sin_port = htons(atoi(port));
 119
 120         if (connect(sock, (struct sockaddr *)&sin, sizeof(sin)) < 0) {
 121                 close(sock);
 122                 return -1;
 123         }
 124         return sock;
 125 }
 126
 127 /* Allow connexion queue > 1 to avoid race conditions. */
 128 #define MAX_CONNEXIONS 5
 129
 130 struct port_info {
 131         int socket;
 132         char *port;
 133 };
 134
 135 /* Wait at most 30s between connection attempts. */
 136 #define MAX_WAIT 30
 137
 138 /* Open a connection on the given socket/port.
 139  * Act as server if the port doesn't contain a hostname,
 140  * as a client otherwise. If socket < 0 or in client mode,
 141  * create the socket from the given port and update socket.
 142  * Block until the connection succeeds.
 143  * Return a file descriptor for the new connection. */
 144 static int
 145 open_connection(struct port_info *info)
 146 {
 147         int conn;
 148         char *p = strchr(info->port, ':');
 149         if (p) {
 150                 for (int try = 1;; ) {
 151                         conn = open_client_connection(info->port);
 152                         if (conn >= 0) break;
 153                         sleep(try);
 154                         if (try < MAX_WAIT) try++;
 155                 }
 156                 info->socket = conn;
 157         } else {
 158                 if (info->socket < 0)
 159                         info->socket = port_listen(info->port, MAX_CONNEXIONS);
 160                 conn = open_server_connection(info->socket, NULL);
 161         }
 162         return conn;
 163 }
 164
 165 /* Open the log connection on the given port, redirect stderr to it. */
 166 static void
 167 open_log_connection(struct port_info *info)
 168 {
 169         int log_conn = open_connection(info);
 170         if (dup2(log_conn, STDERR) < 0)
 171                 die("dup2");
 172         if (DEBUGL(0))
 173                 fprintf(stderr, "log connection opened\n");
 174 }
 175
 176 /* Thread keeping the log connection open and redirecting stderr to it.
 177  * It also echoes its input, which can be used to check if the
 178  * program is alive. As a weak identity check, in server mode the input
 179  * must start with "Pachi" (without the quotes). */
 180 static void *
 181 log_thread(void *arg)
 182 {
 183         struct port_info *info = arg;
 184         assert(info && info->port);
 185         for (;;) {
 186                 char buf[BSIZE];
 187                 int size;
 188                 bool check = !strchr(info->port, ':');
 189                 if (!check)
 190                         write(STDERR, "Pachi\n", 6);
 191                 while ((size = read(STDERR, buf, BSIZE)) > 0) {
 192                         if (check && strncasecmp(buf, "Pachi", 5)) break;
 193                         check = false;
 194                         write(STDERR, buf, size);
 195                 }
 196                 fflush(stderr);
 197                 open_log_connection(info);
 198         }
 199 }
 200
 201 /* Open the log connection on the given port, redirect stderr to it,
 202  * and keep reopening it if the connection is closed. */
 203 void
 204 open_log_port(char *port)
 205 {
 206         pthread_t thread;
 207         static struct port_info log_info = { .socket = -1 };
 208         log_info.port = port;
 209         open_log_connection(&log_info);
 210
 211         /* From now on, log_info may only be modified by the single
 212          * log_thread so static allocation is ok and there is no race. */
 213         pthread_create(&thread, NULL, log_thread, (void *)&log_info);
 214 }
 215
 216 /* Open the gtp connection on the given port, redirect stdin & stdout to it. */
 217 void
 218 open_gtp_connection(int *socket, char *port)
 219 {
 220         static struct port_info gtp_info = { .socket = -1 };
 221         gtp_info.port = port;
 222         int gtp_conn = open_connection(&gtp_info);
 223         for (int d = STDIN; d <= STDOUT; d++) {
 224                 if (dup2(gtp_conn, d) < 0)
 225                         die("dup2");
 226         }
 227         if (DEBUGL(0))
 228                 fprintf(stderr, "gtp connection opened\n");
 229 }