2 * SSH port forwarding.
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18 struct PFwdPrivate {
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19 const struct plug_function_table *fn;
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20 /* the above variable absolutely *must* be the first in this structure */
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21 void *c; /* (channel) data used by ssh.c */
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22 void *backhandle; /* instance of SSH backend itself */
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23 /* Note that backhandle need not be filled in if c is non-NULL */
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25 int throttled, throttle_override;
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28 * `dynamic' does double duty. It's set to 0 for an ordinary
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29 * forwarded port, and nonzero for SOCKS-style dynamic port
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30 * forwarding; but it also represents the state of the SOCKS
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35 * `hostname' and `port' are the real hostname and port, once
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36 * we know what we're connecting to; they're unused for this
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37 * purpose while conducting a local SOCKS exchange, which means
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38 * we can also use them as a buffer and pointer for reading
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39 * data from the SOCKS client.
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41 char hostname[256+8];
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44 * When doing dynamic port forwarding, we can receive
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45 * connection data before we are actually able to send it; so
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46 * we may have to temporarily hold some in a dynamically
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47 * allocated buffer here.
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53 static void pfd_log(Plug plug, int type, SockAddr addr, int port,
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54 const char *error_msg, int error_code)
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56 /* we have to dump these since we have no interface to logging.c */
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59 static int pfd_closing(Plug plug, const char *error_msg, int error_code,
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62 struct PFwdPrivate *pr = (struct PFwdPrivate *) plug;
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65 * We have no way to communicate down the forwarded connection,
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66 * so if an error occurred on the socket, we just ignore it
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67 * and treat it like a proper close.
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70 sshfwd_close(pr->c);
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75 static int pfd_receive(Plug plug, int urgent, char *data, int len)
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77 struct PFwdPrivate *pr = (struct PFwdPrivate *) plug;
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81 * Throughout SOCKS negotiation, "hostname" is re-used as a
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82 * random protocol buffer with "port" storing the length.
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84 if (pr->port >= lenof(pr->hostname)) {
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85 /* Request too long. */
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86 if ((pr->dynamic >> 12) == 4) {
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87 /* Send back a SOCKS 4 error before closing. */
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89 memset(data, 0, sizeof(data));
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90 data[1] = 91; /* generic `request rejected' */
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91 sk_write(pr->s, data, 8);
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96 pr->hostname[pr->port++] = *data++;
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99 * Now check what's in the buffer to see if it's a
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100 * valid and complete message in the SOCKS exchange.
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102 if ((pr->dynamic == 1 || (pr->dynamic >> 12) == 4) &&
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103 pr->hostname[0] == 4) {
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107 if (pr->dynamic == 1)
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108 pr->dynamic = 0x4000;
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109 if (pr->port < 2) continue;/* don't have command code yet */
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110 if (pr->hostname[1] != 1) {
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112 /* Send back a SOCKS 4 error before closing. */
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114 memset(data, 0, sizeof(data));
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115 data[1] = 91; /* generic `request rejected' */
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116 sk_write(pr->s, data, 8);
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120 if (pr->port <= 8) continue; /* haven't started user/hostname */
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121 if (pr->hostname[pr->port-1] != 0)
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122 continue; /* haven't _finished_ user/hostname */
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124 * Now we have a full SOCKS 4 request. Check it to
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125 * see if it's a SOCKS 4A request.
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127 if (pr->hostname[4] == 0 && pr->hostname[5] == 0 &&
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128 pr->hostname[6] == 0 && pr->hostname[7] != 0) {
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130 * It's SOCKS 4A. So if we haven't yet
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131 * collected the host name, we should continue
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132 * waiting for data in order to do so; if we
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133 * have, we can go ahead.
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136 if (pr->dynamic == 0x4000) {
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137 pr->dynamic = 0x4001;
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138 pr->port = 8; /* reset buffer to overwrite name */
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141 pr->hostname[0] = 0; /* reply version code */
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142 pr->hostname[1] = 90; /* request granted */
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143 sk_write(pr->s, pr->hostname, 8);
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145 pr->port = GET_16BIT_MSB_FIRST(pr->hostname+2);
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146 memmove(pr->hostname, pr->hostname + 8, len);
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150 * It's SOCKS 4, which means we should format
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151 * the IP address into the hostname string and
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154 pr->hostname[0] = 0; /* reply version code */
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155 pr->hostname[1] = 90; /* request granted */
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156 sk_write(pr->s, pr->hostname, 8);
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157 pr->port = GET_16BIT_MSB_FIRST(pr->hostname+2);
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158 sprintf(pr->hostname, "%d.%d.%d.%d",
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159 (unsigned char)pr->hostname[4],
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160 (unsigned char)pr->hostname[5],
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161 (unsigned char)pr->hostname[6],
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162 (unsigned char)pr->hostname[7]);
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167 if ((pr->dynamic == 1 || (pr->dynamic >> 12) == 5) &&
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168 pr->hostname[0] == 5) {
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172 if (pr->dynamic == 1)
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173 pr->dynamic = 0x5000;
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175 if (pr->dynamic == 0x5000) {
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179 * We're receiving a set of method identifiers.
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181 if (pr->port < 2) continue;/* no method count yet */
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182 if (pr->port < 2 + (unsigned char)pr->hostname[1])
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183 continue; /* no methods yet */
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184 method = 0xFF; /* invalid */
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185 for (i = 0; i < (unsigned char)pr->hostname[1]; i++)
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186 if (pr->hostname[2+i] == 0) {
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187 method = 0;/* no auth */
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192 sk_write(pr->s, data, 2);
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193 pr->dynamic = 0x5001;
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194 pr->port = 0; /* re-empty the buffer */
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198 if (pr->dynamic == 0x5001) {
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200 * We're receiving a SOCKS request.
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202 unsigned char reply[10]; /* SOCKS5 atyp=1 reply */
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203 int atype, alen = 0;
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206 * Pre-fill reply packet.
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207 * In all cases, we set BND.{HOST,ADDR} to 0.0.0.0:0
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208 * (atyp=1) in the reply; if we succeed, we don't know
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209 * the right answers, and if we fail, they should be
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212 memset(reply, 0, lenof(reply));
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213 reply[0] = 5; /* VER */
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214 reply[3] = 1; /* ATYP = 1 (IPv4, 0.0.0.0:0) */
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216 if (pr->port < 6) continue;
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217 atype = (unsigned char)pr->hostname[3];
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218 if (atype == 1) /* IPv4 address */
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220 if (atype == 4) /* IPv6 address */
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222 if (atype == 3) /* domain name has leading length */
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223 alen = 1 + (unsigned char)pr->hostname[4];
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224 if (pr->port < 6 + alen) continue;
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225 if (pr->hostname[1] != 1 || pr->hostname[2] != 0) {
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226 /* Not CONNECT or reserved field nonzero - error */
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227 reply[1] = 1; /* generic failure */
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228 sk_write(pr->s, (char *) reply, lenof(reply));
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233 * Now we have a viable connect request. Switch
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236 pr->port = GET_16BIT_MSB_FIRST(pr->hostname+4+alen);
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238 /* REP=0 (success) already */
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239 sk_write(pr->s, (char *) reply, lenof(reply));
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240 sprintf(pr->hostname, "%d.%d.%d.%d",
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241 (unsigned char)pr->hostname[4],
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242 (unsigned char)pr->hostname[5],
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243 (unsigned char)pr->hostname[6],
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244 (unsigned char)pr->hostname[7]);
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246 } else if (atype == 3) {
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247 /* REP=0 (success) already */
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248 sk_write(pr->s, (char *) reply, lenof(reply));
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249 memmove(pr->hostname, pr->hostname + 5, alen-1);
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250 pr->hostname[alen-1] = '\0';
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254 * Unknown address type. (FIXME: support IPv6!)
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256 reply[1] = 8; /* atype not supported */
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257 sk_write(pr->s, (char *) reply, lenof(reply));
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265 * If we get here without either having done `continue'
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266 * or `goto connect', it must be because there is no
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267 * sensible interpretation of what's in our buffer. So
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268 * close the connection rudely.
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276 * We come here when we're ready to make an actual
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282 * Freeze the socket until the SSH server confirms the
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285 sk_set_frozen(pr->s, 1);
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287 pr->c = new_sock_channel(pr->backhandle, pr->s);
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288 if (pr->c == NULL) {
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292 /* asks to forward to the specified host/port for this */
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293 ssh_send_port_open(pr->c, pr->hostname, pr->port, "forwarding");
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298 * If there's any data remaining in our current buffer,
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299 * save it to be sent on pfd_confirm().
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302 pr->buffer = snewn(len, char);
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303 memcpy(pr->buffer, data, len);
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308 if (sshfwd_write(pr->c, data, len) > 0) {
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310 sk_set_frozen(pr->s, 1);
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316 static void pfd_sent(Plug plug, int bufsize)
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318 struct PFwdPrivate *pr = (struct PFwdPrivate *) plug;
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321 sshfwd_unthrottle(pr->c, bufsize);
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325 * Called when receiving a PORT OPEN from the server
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327 const char *pfd_newconnect(Socket *s, char *hostname, int port,
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328 void *c, const Config *cfg, int addressfamily)
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330 static const struct plug_function_table fn_table = {
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340 char *dummy_realhost;
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341 struct PFwdPrivate *pr;
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344 * Try to find host.
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346 addr = name_lookup(hostname, port, &dummy_realhost, cfg, addressfamily);
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347 if ((err = sk_addr_error(addr)) != NULL) {
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348 sk_addr_free(addr);
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355 pr = snew(struct PFwdPrivate);
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357 pr->fn = &fn_table;
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358 pr->throttled = pr->throttle_override = 0;
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361 pr->backhandle = NULL; /* we shouldn't need this */
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364 pr->s = *s = new_connection(addr, dummy_realhost, port,
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365 0, 1, 0, 0, (Plug) pr, cfg);
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366 if ((err = sk_socket_error(*s)) != NULL) {
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371 sk_set_private_ptr(*s, pr);
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376 called when someone connects to the local port
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379 static int pfd_accepting(Plug p, OSSocket sock)
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381 static const struct plug_function_table fn_table = {
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388 struct PFwdPrivate *pr, *org;
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392 org = (struct PFwdPrivate *)p;
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393 pr = snew(struct PFwdPrivate);
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395 pr->fn = &fn_table;
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398 pr->backhandle = org->backhandle;
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400 pr->s = s = sk_register(sock, (Plug) pr);
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401 if ((err = sk_socket_error(s)) != NULL) {
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403 return err != NULL;
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406 sk_set_private_ptr(s, pr);
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408 pr->throttled = pr->throttle_override = 0;
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411 if (org->dynamic) {
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413 pr->port = 0; /* "hostname" buffer is so far empty */
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414 sk_set_frozen(s, 0); /* we want to receive SOCKS _now_! */
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417 strcpy(pr->hostname, org->hostname);
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418 pr->port = org->port;
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419 pr->c = new_sock_channel(org->backhandle, s);
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421 if (pr->c == NULL) {
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425 /* asks to forward to the specified host/port for this */
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426 ssh_send_port_open(pr->c, pr->hostname, pr->port, "forwarding");
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434 /* Add a new forwarding from port -> desthost:destport
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435 sets up a listener on the local machine on (srcaddr:)port
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437 const char *pfd_addforward(char *desthost, int destport, char *srcaddr,
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438 int port, void *backhandle, const Config *cfg,
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439 void **sockdata, int address_family)
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441 static const struct plug_function_table fn_table = {
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444 pfd_receive, /* should not happen... */
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445 pfd_sent, /* also should not happen */
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450 struct PFwdPrivate *pr;
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456 pr = snew(struct PFwdPrivate);
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458 pr->fn = &fn_table;
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461 strcpy(pr->hostname, desthost);
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462 pr->port = destport;
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466 pr->throttled = pr->throttle_override = 0;
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468 pr->backhandle = backhandle;
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470 pr->s = s = new_listener(srcaddr, port, (Plug) pr,
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471 !cfg->lport_acceptall, cfg, address_family);
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472 if ((err = sk_socket_error(s)) != NULL) {
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477 sk_set_private_ptr(s, pr);
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479 *sockdata = (void *)s;
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484 void pfd_close(Socket s)
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486 struct PFwdPrivate *pr;
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491 pr = (struct PFwdPrivate *) sk_get_private_ptr(s);
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500 * Terminate a listener.
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502 void pfd_terminate(void *sv)
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504 pfd_close((Socket)sv);
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507 void pfd_unthrottle(Socket s)
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509 struct PFwdPrivate *pr;
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512 pr = (struct PFwdPrivate *) sk_get_private_ptr(s);
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515 sk_set_frozen(s, pr->throttled || pr->throttle_override);
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518 void pfd_override_throttle(Socket s, int enable)
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520 struct PFwdPrivate *pr;
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523 pr = (struct PFwdPrivate *) sk_get_private_ptr(s);
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525 pr->throttle_override = enable;
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526 sk_set_frozen(s, pr->throttled || pr->throttle_override);
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530 * Called to send data down the raw connection.
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532 int pfd_send(Socket s, char *data, int len)
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536 return sk_write(s, data, len);
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540 void pfd_confirm(Socket s)
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542 struct PFwdPrivate *pr;
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547 pr = (struct PFwdPrivate *) sk_get_private_ptr(s);
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549 sk_set_frozen(s, 0);
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550 sk_write(s, NULL, 0);
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552 sshfwd_write(pr->c, pr->buffer, pr->buflen);
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