1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * X.25 Packet Layer release 002 4 * 5 * This is ALPHA test software. This code may break your machine, 6 * randomly fail to work with new releases, misbehave and/or generally 7 * screw up. It might even work. 8 * 9 * This code REQUIRES 2.1.15 or higher 10 * 11 * History 12 * X.25 001 Jonathan Naylor Started coding. 13 * X.25 002 Jonathan Naylor Centralised disconnection code. 14 * New timer architecture. 15 * 2000-03-20 Daniela Squassoni Disabling/enabling of facilities 16 * negotiation. 17 * 2000-11-10 Henner Eisen Check and reset for out-of-sequence 18 * i-frames. 19 */ 20 21 #define pr_fmt(fmt) "X25: " fmt 22 23 #include <linux/slab.h> 24 #include <linux/errno.h> 25 #include <linux/kernel.h> 26 #include <linux/string.h> 27 #include <linux/skbuff.h> 28 #include <net/sock.h> 29 #include <net/tcp_states.h> 30 #include <net/x25.h> 31 32 static int x25_queue_rx_frame(struct sock *sk, struct sk_buff *skb, int more) 33 { 34 struct sk_buff *skbo, *skbn = skb; 35 struct x25_sock *x25 = x25_sk(sk); 36 37 if (more) { 38 x25->fraglen += skb->len; 39 skb_queue_tail(&x25->fragment_queue, skb); 40 skb_set_owner_r(skb, sk); 41 return 0; 42 } 43 44 if (x25->fraglen > 0) { /* End of fragment */ 45 int len = x25->fraglen + skb->len; 46 47 if ((skbn = alloc_skb(len, GFP_ATOMIC)) == NULL){ 48 kfree_skb(skb); 49 return 1; 50 } 51 52 skb_queue_tail(&x25->fragment_queue, skb); 53 54 skb_reset_transport_header(skbn); 55 56 skbo = skb_dequeue(&x25->fragment_queue); 57 skb_copy_from_linear_data(skbo, skb_put(skbn, skbo->len), 58 skbo->len); 59 kfree_skb(skbo); 60 61 while ((skbo = 62 skb_dequeue(&x25->fragment_queue)) != NULL) { 63 skb_pull(skbo, (x25->neighbour->extended) ? 64 X25_EXT_MIN_LEN : X25_STD_MIN_LEN); 65 skb_copy_from_linear_data(skbo, 66 skb_put(skbn, skbo->len), 67 skbo->len); 68 kfree_skb(skbo); 69 } 70 71 x25->fraglen = 0; 72 } 73 74 skb_set_owner_r(skbn, sk); 75 skb_queue_tail(&sk->sk_receive_queue, skbn); 76 if (!sock_flag(sk, SOCK_DEAD)) 77 sk->sk_data_ready(sk); 78 79 return 0; 80 } 81 82 /* 83 * State machine for state 1, Awaiting Call Accepted State. 84 * The handling of the timer(s) is in file x25_timer.c. 85 * Handling of state 0 and connection release is in af_x25.c. 86 */ 87 static int x25_state1_machine(struct sock *sk, struct sk_buff *skb, int frametype) 88 { 89 struct x25_address source_addr, dest_addr; 90 int len; 91 struct x25_sock *x25 = x25_sk(sk); 92 93 switch (frametype) { 94 case X25_CALL_ACCEPTED: { 95 96 x25_stop_timer(sk); 97 x25->condition = 0x00; 98 x25->vs = 0; 99 x25->va = 0; 100 x25->vr = 0; 101 x25->vl = 0; 102 x25->state = X25_STATE_3; 103 sk->sk_state = TCP_ESTABLISHED; 104 /* 105 * Parse the data in the frame. 106 */ 107 if (!pskb_may_pull(skb, X25_STD_MIN_LEN)) 108 goto out_clear; 109 skb_pull(skb, X25_STD_MIN_LEN); 110 111 len = x25_parse_address_block(skb, &source_addr, 112 &dest_addr); 113 if (len > 0) 114 skb_pull(skb, len); 115 else if (len < 0) 116 goto out_clear; 117 118 len = x25_parse_facilities(skb, &x25->facilities, 119 &x25->dte_facilities, 120 &x25->vc_facil_mask); 121 if (len > 0) 122 skb_pull(skb, len); 123 else if (len < 0) 124 goto out_clear; 125 /* 126 * Copy any Call User Data. 127 */ 128 if (skb->len > 0) { 129 if (skb->len > X25_MAX_CUD_LEN) 130 goto out_clear; 131 132 skb_copy_bits(skb, 0, x25->calluserdata.cuddata, 133 skb->len); 134 x25->calluserdata.cudlength = skb->len; 135 } 136 if (!sock_flag(sk, SOCK_DEAD)) 137 sk->sk_state_change(sk); 138 break; 139 } 140 case X25_CALL_REQUEST: 141 /* call collision */ 142 x25->causediag.cause = 0x01; 143 x25->causediag.diagnostic = 0x48; 144 145 x25_write_internal(sk, X25_CLEAR_REQUEST); 146 x25_disconnect(sk, EISCONN, 0x01, 0x48); 147 break; 148 149 case X25_CLEAR_REQUEST: 150 if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2)) 151 goto out_clear; 152 153 x25_write_internal(sk, X25_CLEAR_CONFIRMATION); 154 x25_disconnect(sk, ECONNREFUSED, skb->data[3], skb->data[4]); 155 break; 156 157 default: 158 break; 159 } 160 161 return 0; 162 163 out_clear: 164 x25_write_internal(sk, X25_CLEAR_REQUEST); 165 x25->state = X25_STATE_2; 166 x25_start_t23timer(sk); 167 return 0; 168 } 169 170 /* 171 * State machine for state 2, Awaiting Clear Confirmation State. 172 * The handling of the timer(s) is in file x25_timer.c 173 * Handling of state 0 and connection release is in af_x25.c. 174 */ 175 static int x25_state2_machine(struct sock *sk, struct sk_buff *skb, int frametype) 176 { 177 switch (frametype) { 178 179 case X25_CLEAR_REQUEST: 180 if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2)) 181 goto out_clear; 182 183 x25_write_internal(sk, X25_CLEAR_CONFIRMATION); 184 x25_disconnect(sk, 0, skb->data[3], skb->data[4]); 185 break; 186 187 case X25_CLEAR_CONFIRMATION: 188 x25_disconnect(sk, 0, 0, 0); 189 break; 190 191 default: 192 break; 193 } 194 195 return 0; 196 197 out_clear: 198 x25_write_internal(sk, X25_CLEAR_REQUEST); 199 x25_start_t23timer(sk); 200 return 0; 201 } 202 203 /* 204 * State machine for state 3, Connected State. 205 * The handling of the timer(s) is in file x25_timer.c 206 * Handling of state 0 and connection release is in af_x25.c. 207 */ 208 static int x25_state3_machine(struct sock *sk, struct sk_buff *skb, int frametype, int ns, int nr, int q, int d, int m) 209 { 210 int queued = 0; 211 int modulus; 212 struct x25_sock *x25 = x25_sk(sk); 213 214 modulus = (x25->neighbour->extended) ? X25_EMODULUS : X25_SMODULUS; 215 216 switch (frametype) { 217 218 case X25_RESET_REQUEST: 219 x25_write_internal(sk, X25_RESET_CONFIRMATION); 220 x25_stop_timer(sk); 221 x25->condition = 0x00; 222 x25->vs = 0; 223 x25->vr = 0; 224 x25->va = 0; 225 x25->vl = 0; 226 x25_requeue_frames(sk); 227 break; 228 229 case X25_CLEAR_REQUEST: 230 if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2)) 231 goto out_clear; 232 233 x25_write_internal(sk, X25_CLEAR_CONFIRMATION); 234 x25_disconnect(sk, 0, skb->data[3], skb->data[4]); 235 break; 236 237 case X25_RR: 238 case X25_RNR: 239 if (!x25_validate_nr(sk, nr)) { 240 x25_clear_queues(sk); 241 x25_write_internal(sk, X25_RESET_REQUEST); 242 x25_start_t22timer(sk); 243 x25->condition = 0x00; 244 x25->vs = 0; 245 x25->vr = 0; 246 x25->va = 0; 247 x25->vl = 0; 248 x25->state = X25_STATE_4; 249 } else { 250 x25_frames_acked(sk, nr); 251 if (frametype == X25_RNR) { 252 x25->condition |= X25_COND_PEER_RX_BUSY; 253 } else { 254 x25->condition &= ~X25_COND_PEER_RX_BUSY; 255 } 256 } 257 break; 258 259 case X25_DATA: /* XXX */ 260 x25->condition &= ~X25_COND_PEER_RX_BUSY; 261 if ((ns != x25->vr) || !x25_validate_nr(sk, nr)) { 262 x25_clear_queues(sk); 263 x25_write_internal(sk, X25_RESET_REQUEST); 264 x25_start_t22timer(sk); 265 x25->condition = 0x00; 266 x25->vs = 0; 267 x25->vr = 0; 268 x25->va = 0; 269 x25->vl = 0; 270 x25->state = X25_STATE_4; 271 break; 272 } 273 x25_frames_acked(sk, nr); 274 if (ns == x25->vr) { 275 if (x25_queue_rx_frame(sk, skb, m) == 0) { 276 x25->vr = (x25->vr + 1) % modulus; 277 queued = 1; 278 } else { 279 /* Should never happen */ 280 x25_clear_queues(sk); 281 x25_write_internal(sk, X25_RESET_REQUEST); 282 x25_start_t22timer(sk); 283 x25->condition = 0x00; 284 x25->vs = 0; 285 x25->vr = 0; 286 x25->va = 0; 287 x25->vl = 0; 288 x25->state = X25_STATE_4; 289 break; 290 } 291 if (atomic_read(&sk->sk_rmem_alloc) > 292 (sk->sk_rcvbuf >> 1)) 293 x25->condition |= X25_COND_OWN_RX_BUSY; 294 } 295 /* 296 * If the window is full Ack it immediately, else 297 * start the holdback timer. 298 */ 299 if (((x25->vl + x25->facilities.winsize_in) % modulus) == x25->vr) { 300 x25->condition &= ~X25_COND_ACK_PENDING; 301 x25_stop_timer(sk); 302 x25_enquiry_response(sk); 303 } else { 304 x25->condition |= X25_COND_ACK_PENDING; 305 x25_start_t2timer(sk); 306 } 307 break; 308 309 case X25_INTERRUPT_CONFIRMATION: 310 clear_bit(X25_INTERRUPT_FLAG, &x25->flags); 311 break; 312 313 case X25_INTERRUPT: 314 if (sock_flag(sk, SOCK_URGINLINE)) 315 queued = !sock_queue_rcv_skb(sk, skb); 316 else { 317 skb_set_owner_r(skb, sk); 318 skb_queue_tail(&x25->interrupt_in_queue, skb); 319 queued = 1; 320 } 321 sk_send_sigurg(sk); 322 x25_write_internal(sk, X25_INTERRUPT_CONFIRMATION); 323 break; 324 325 default: 326 pr_warn("unknown %02X in state 3\n", frametype); 327 break; 328 } 329 330 return queued; 331 332 out_clear: 333 x25_write_internal(sk, X25_CLEAR_REQUEST); 334 x25->state = X25_STATE_2; 335 x25_start_t23timer(sk); 336 return 0; 337 } 338 339 /* 340 * State machine for state 4, Awaiting Reset Confirmation State. 341 * The handling of the timer(s) is in file x25_timer.c 342 * Handling of state 0 and connection release is in af_x25.c. 343 */ 344 static int x25_state4_machine(struct sock *sk, struct sk_buff *skb, int frametype) 345 { 346 struct x25_sock *x25 = x25_sk(sk); 347 348 switch (frametype) { 349 350 case X25_RESET_REQUEST: 351 x25_write_internal(sk, X25_RESET_CONFIRMATION); 352 fallthrough; 353 case X25_RESET_CONFIRMATION: { 354 x25_stop_timer(sk); 355 x25->condition = 0x00; 356 x25->va = 0; 357 x25->vr = 0; 358 x25->vs = 0; 359 x25->vl = 0; 360 x25->state = X25_STATE_3; 361 x25_requeue_frames(sk); 362 break; 363 } 364 case X25_CLEAR_REQUEST: 365 if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2)) 366 goto out_clear; 367 368 x25_write_internal(sk, X25_CLEAR_CONFIRMATION); 369 x25_disconnect(sk, 0, skb->data[3], skb->data[4]); 370 break; 371 372 default: 373 break; 374 } 375 376 return 0; 377 378 out_clear: 379 x25_write_internal(sk, X25_CLEAR_REQUEST); 380 x25->state = X25_STATE_2; 381 x25_start_t23timer(sk); 382 return 0; 383 } 384 385 /* 386 * State machine for state 5, Call Accepted / Call Connected pending (X25_ACCPT_APPRV_FLAG). 387 * The handling of the timer(s) is in file x25_timer.c 388 * Handling of state 0 and connection release is in af_x25.c. 389 */ 390 static int x25_state5_machine(struct sock *sk, struct sk_buff *skb, int frametype) 391 { 392 struct x25_sock *x25 = x25_sk(sk); 393 394 switch (frametype) { 395 case X25_CLEAR_REQUEST: 396 if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2)) { 397 x25_write_internal(sk, X25_CLEAR_REQUEST); 398 x25->state = X25_STATE_2; 399 x25_start_t23timer(sk); 400 return 0; 401 } 402 403 x25_write_internal(sk, X25_CLEAR_CONFIRMATION); 404 x25_disconnect(sk, 0, skb->data[3], skb->data[4]); 405 break; 406 407 default: 408 break; 409 } 410 411 return 0; 412 } 413 414 /* Higher level upcall for a LAPB frame */ 415 int x25_process_rx_frame(struct sock *sk, struct sk_buff *skb) 416 { 417 struct x25_sock *x25 = x25_sk(sk); 418 int queued = 0, frametype, ns, nr, q, d, m; 419 420 if (x25->state == X25_STATE_0) 421 return 0; 422 423 frametype = x25_decode(sk, skb, &ns, &nr, &q, &d, &m); 424 425 switch (x25->state) { 426 case X25_STATE_1: 427 queued = x25_state1_machine(sk, skb, frametype); 428 break; 429 case X25_STATE_2: 430 queued = x25_state2_machine(sk, skb, frametype); 431 break; 432 case X25_STATE_3: 433 queued = x25_state3_machine(sk, skb, frametype, ns, nr, q, d, m); 434 break; 435 case X25_STATE_4: 436 queued = x25_state4_machine(sk, skb, frametype); 437 break; 438 case X25_STATE_5: 439 queued = x25_state5_machine(sk, skb, frametype); 440 break; 441 } 442 443 x25_kick(sk); 444 445 return queued; 446 } 447 448 int x25_backlog_rcv(struct sock *sk, struct sk_buff *skb) 449 { 450 int queued = x25_process_rx_frame(sk, skb); 451 452 if (!queued) 453 kfree_skb(skb); 454 455 return 0; 456 } 457