1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * SUCS NET3: 4 * 5 * Generic datagram handling routines. These are generic for all 6 * protocols. Possibly a generic IP version on top of these would 7 * make sense. Not tonight however 8-). 8 * This is used because UDP, RAW, PACKET, DDP, IPX, AX.25 and 9 * NetROM layer all have identical poll code and mostly 10 * identical recvmsg() code. So we share it here. The poll was 11 * shared before but buried in udp.c so I moved it. 12 * 13 * Authors: Alan Cox <alan@lxorguk.ukuu.org.uk>. (datagram_poll() from old 14 * udp.c code) 15 * 16 * Fixes: 17 * Alan Cox : NULL return from skb_peek_copy() 18 * understood 19 * Alan Cox : Rewrote skb_read_datagram to avoid the 20 * skb_peek_copy stuff. 21 * Alan Cox : Added support for SOCK_SEQPACKET. 22 * IPX can no longer use the SO_TYPE hack 23 * but AX.25 now works right, and SPX is 24 * feasible. 25 * Alan Cox : Fixed write poll of non IP protocol 26 * crash. 27 * Florian La Roche: Changed for my new skbuff handling. 28 * Darryl Miles : Fixed non-blocking SOCK_SEQPACKET. 29 * Linus Torvalds : BSD semantic fixes. 30 * Alan Cox : Datagram iovec handling 31 * Darryl Miles : Fixed non-blocking SOCK_STREAM. 32 * Alan Cox : POSIXisms 33 * Pete Wyckoff : Unconnected accept() fix. 34 * 35 */ 36 37 #include <linux/module.h> 38 #include <linux/types.h> 39 #include <linux/kernel.h> 40 #include <linux/uaccess.h> 41 #include <linux/mm.h> 42 #include <linux/interrupt.h> 43 #include <linux/errno.h> 44 #include <linux/sched.h> 45 #include <linux/inet.h> 46 #include <linux/netdevice.h> 47 #include <linux/rtnetlink.h> 48 #include <linux/poll.h> 49 #include <linux/highmem.h> 50 #include <linux/spinlock.h> 51 #include <linux/slab.h> 52 #include <linux/pagemap.h> 53 #include <linux/uio.h> 54 55 #include <net/protocol.h> 56 #include <linux/skbuff.h> 57 58 #include <net/checksum.h> 59 #include <net/sock.h> 60 #include <net/tcp_states.h> 61 #include <trace/events/skb.h> 62 #include <net/busy_poll.h> 63 64 #include "datagram.h" 65 66 /* 67 * Is a socket 'connection oriented' ? 68 */ 69 static inline int connection_based(struct sock *sk) 70 { 71 return sk->sk_type == SOCK_SEQPACKET || sk->sk_type == SOCK_STREAM; 72 } 73 74 static int receiver_wake_function(wait_queue_entry_t *wait, unsigned int mode, int sync, 75 void *key) 76 { 77 /* 78 * Avoid a wakeup if event not interesting for us 79 */ 80 if (key && !(key_to_poll(key) & (EPOLLIN | EPOLLERR))) 81 return 0; 82 return autoremove_wake_function(wait, mode, sync, key); 83 } 84 /* 85 * Wait for the last received packet to be different from skb 86 */ 87 int __skb_wait_for_more_packets(struct sock *sk, int *err, long *timeo_p, 88 const struct sk_buff *skb) 89 { 90 int error; 91 DEFINE_WAIT_FUNC(wait, receiver_wake_function); 92 93 prepare_to_wait_exclusive(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE); 94 95 /* Socket errors? */ 96 error = sock_error(sk); 97 if (error) 98 goto out_err; 99 100 if (READ_ONCE(sk->sk_receive_queue.prev) != skb) 101 goto out; 102 103 /* Socket shut down? */ 104 if (sk->sk_shutdown & RCV_SHUTDOWN) 105 goto out_noerr; 106 107 /* Sequenced packets can come disconnected. 108 * If so we report the problem 109 */ 110 error = -ENOTCONN; 111 if (connection_based(sk) && 112 !(sk->sk_state == TCP_ESTABLISHED || sk->sk_state == TCP_LISTEN)) 113 goto out_err; 114 115 /* handle signals */ 116 if (signal_pending(current)) 117 goto interrupted; 118 119 error = 0; 120 *timeo_p = schedule_timeout(*timeo_p); 121 out: 122 finish_wait(sk_sleep(sk), &wait); 123 return error; 124 interrupted: 125 error = sock_intr_errno(*timeo_p); 126 out_err: 127 *err = error; 128 goto out; 129 out_noerr: 130 *err = 0; 131 error = 1; 132 goto out; 133 } 134 EXPORT_SYMBOL(__skb_wait_for_more_packets); 135 136 static struct sk_buff *skb_set_peeked(struct sk_buff *skb) 137 { 138 struct sk_buff *nskb; 139 140 if (skb->peeked) 141 return skb; 142 143 /* We have to unshare an skb before modifying it. */ 144 if (!skb_shared(skb)) 145 goto done; 146 147 nskb = skb_clone(skb, GFP_ATOMIC); 148 if (!nskb) 149 return ERR_PTR(-ENOMEM); 150 151 skb->prev->next = nskb; 152 skb->next->prev = nskb; 153 nskb->prev = skb->prev; 154 nskb->next = skb->next; 155 156 consume_skb(skb); 157 skb = nskb; 158 159 done: 160 skb->peeked = 1; 161 162 return skb; 163 } 164 165 struct sk_buff *__skb_try_recv_from_queue(struct sock *sk, 166 struct sk_buff_head *queue, 167 unsigned int flags, 168 void (*destructor)(struct sock *sk, 169 struct sk_buff *skb), 170 int *off, int *err, 171 struct sk_buff **last) 172 { 173 bool peek_at_off = false; 174 struct sk_buff *skb; 175 int _off = 0; 176 177 if (unlikely(flags & MSG_PEEK && *off >= 0)) { 178 peek_at_off = true; 179 _off = *off; 180 } 181 182 *last = queue->prev; 183 skb_queue_walk(queue, skb) { 184 if (flags & MSG_PEEK) { 185 if (peek_at_off && _off >= skb->len && 186 (_off || skb->peeked)) { 187 _off -= skb->len; 188 continue; 189 } 190 if (!skb->len) { 191 skb = skb_set_peeked(skb); 192 if (IS_ERR(skb)) { 193 *err = PTR_ERR(skb); 194 return NULL; 195 } 196 } 197 refcount_inc(&skb->users); 198 } else { 199 __skb_unlink(skb, queue); 200 if (destructor) 201 destructor(sk, skb); 202 } 203 *off = _off; 204 return skb; 205 } 206 return NULL; 207 } 208 209 /** 210 * __skb_try_recv_datagram - Receive a datagram skbuff 211 * @sk: socket 212 * @flags: MSG\_ flags 213 * @destructor: invoked under the receive lock on successful dequeue 214 * @off: an offset in bytes to peek skb from. Returns an offset 215 * within an skb where data actually starts 216 * @err: error code returned 217 * @last: set to last peeked message to inform the wait function 218 * what to look for when peeking 219 * 220 * Get a datagram skbuff, understands the peeking, nonblocking wakeups 221 * and possible races. This replaces identical code in packet, raw and 222 * udp, as well as the IPX AX.25 and Appletalk. It also finally fixes 223 * the long standing peek and read race for datagram sockets. If you 224 * alter this routine remember it must be re-entrant. 225 * 226 * This function will lock the socket if a skb is returned, so 227 * the caller needs to unlock the socket in that case (usually by 228 * calling skb_free_datagram). Returns NULL with @err set to 229 * -EAGAIN if no data was available or to some other value if an 230 * error was detected. 231 * 232 * * It does not lock socket since today. This function is 233 * * free of race conditions. This measure should/can improve 234 * * significantly datagram socket latencies at high loads, 235 * * when data copying to user space takes lots of time. 236 * * (BTW I've just killed the last cli() in IP/IPv6/core/netlink/packet 237 * * 8) Great win.) 238 * * --ANK (980729) 239 * 240 * The order of the tests when we find no data waiting are specified 241 * quite explicitly by POSIX 1003.1g, don't change them without having 242 * the standard around please. 243 */ 244 struct sk_buff *__skb_try_recv_datagram(struct sock *sk, unsigned int flags, 245 void (*destructor)(struct sock *sk, 246 struct sk_buff *skb), 247 int *off, int *err, 248 struct sk_buff **last) 249 { 250 struct sk_buff_head *queue = &sk->sk_receive_queue; 251 struct sk_buff *skb; 252 unsigned long cpu_flags; 253 /* 254 * Caller is allowed not to check sk->sk_err before skb_recv_datagram() 255 */ 256 int error = sock_error(sk); 257 258 if (error) 259 goto no_packet; 260 261 do { 262 /* Again only user level code calls this function, so nothing 263 * interrupt level will suddenly eat the receive_queue. 264 * 265 * Look at current nfs client by the way... 266 * However, this function was correct in any case. 8) 267 */ 268 spin_lock_irqsave(&queue->lock, cpu_flags); 269 skb = __skb_try_recv_from_queue(sk, queue, flags, destructor, 270 off, &error, last); 271 spin_unlock_irqrestore(&queue->lock, cpu_flags); 272 if (error) 273 goto no_packet; 274 if (skb) 275 return skb; 276 277 if (!sk_can_busy_loop(sk)) 278 break; 279 280 sk_busy_loop(sk, flags & MSG_DONTWAIT); 281 } while (READ_ONCE(sk->sk_receive_queue.prev) != *last); 282 283 error = -EAGAIN; 284 285 no_packet: 286 *err = error; 287 return NULL; 288 } 289 EXPORT_SYMBOL(__skb_try_recv_datagram); 290 291 struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned int flags, 292 void (*destructor)(struct sock *sk, 293 struct sk_buff *skb), 294 int *off, int *err) 295 { 296 struct sk_buff *skb, *last; 297 long timeo; 298 299 timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT); 300 301 do { 302 skb = __skb_try_recv_datagram(sk, flags, destructor, off, err, 303 &last); 304 if (skb) 305 return skb; 306 307 if (*err != -EAGAIN) 308 break; 309 } while (timeo && 310 !__skb_wait_for_more_packets(sk, err, &timeo, last)); 311 312 return NULL; 313 } 314 EXPORT_SYMBOL(__skb_recv_datagram); 315 316 struct sk_buff *skb_recv_datagram(struct sock *sk, unsigned int flags, 317 int noblock, int *err) 318 { 319 int off = 0; 320 321 return __skb_recv_datagram(sk, flags | (noblock ? MSG_DONTWAIT : 0), 322 NULL, &off, err); 323 } 324 EXPORT_SYMBOL(skb_recv_datagram); 325 326 void skb_free_datagram(struct sock *sk, struct sk_buff *skb) 327 { 328 consume_skb(skb); 329 sk_mem_reclaim_partial(sk); 330 } 331 EXPORT_SYMBOL(skb_free_datagram); 332 333 void __skb_free_datagram_locked(struct sock *sk, struct sk_buff *skb, int len) 334 { 335 bool slow; 336 337 if (!skb_unref(skb)) { 338 sk_peek_offset_bwd(sk, len); 339 return; 340 } 341 342 slow = lock_sock_fast(sk); 343 sk_peek_offset_bwd(sk, len); 344 skb_orphan(skb); 345 sk_mem_reclaim_partial(sk); 346 unlock_sock_fast(sk, slow); 347 348 /* skb is now orphaned, can be freed outside of locked section */ 349 __kfree_skb(skb); 350 } 351 EXPORT_SYMBOL(__skb_free_datagram_locked); 352 353 int __sk_queue_drop_skb(struct sock *sk, struct sk_buff_head *sk_queue, 354 struct sk_buff *skb, unsigned int flags, 355 void (*destructor)(struct sock *sk, 356 struct sk_buff *skb)) 357 { 358 int err = 0; 359 360 if (flags & MSG_PEEK) { 361 err = -ENOENT; 362 spin_lock_bh(&sk_queue->lock); 363 if (skb->next) { 364 __skb_unlink(skb, sk_queue); 365 refcount_dec(&skb->users); 366 if (destructor) 367 destructor(sk, skb); 368 err = 0; 369 } 370 spin_unlock_bh(&sk_queue->lock); 371 } 372 373 atomic_inc(&sk->sk_drops); 374 return err; 375 } 376 EXPORT_SYMBOL(__sk_queue_drop_skb); 377 378 /** 379 * skb_kill_datagram - Free a datagram skbuff forcibly 380 * @sk: socket 381 * @skb: datagram skbuff 382 * @flags: MSG\_ flags 383 * 384 * This function frees a datagram skbuff that was received by 385 * skb_recv_datagram. The flags argument must match the one 386 * used for skb_recv_datagram. 387 * 388 * If the MSG_PEEK flag is set, and the packet is still on the 389 * receive queue of the socket, it will be taken off the queue 390 * before it is freed. 391 * 392 * This function currently only disables BH when acquiring the 393 * sk_receive_queue lock. Therefore it must not be used in a 394 * context where that lock is acquired in an IRQ context. 395 * 396 * It returns 0 if the packet was removed by us. 397 */ 398 399 int skb_kill_datagram(struct sock *sk, struct sk_buff *skb, unsigned int flags) 400 { 401 int err = __sk_queue_drop_skb(sk, &sk->sk_receive_queue, skb, flags, 402 NULL); 403 404 kfree_skb(skb); 405 sk_mem_reclaim_partial(sk); 406 return err; 407 } 408 EXPORT_SYMBOL(skb_kill_datagram); 409 410 static int __skb_datagram_iter(const struct sk_buff *skb, int offset, 411 struct iov_iter *to, int len, bool fault_short, 412 size_t (*cb)(const void *, size_t, void *, 413 struct iov_iter *), void *data) 414 { 415 int start = skb_headlen(skb); 416 int i, copy = start - offset, start_off = offset, n; 417 struct sk_buff *frag_iter; 418 419 /* Copy header. */ 420 if (copy > 0) { 421 if (copy > len) 422 copy = len; 423 n = cb(skb->data + offset, copy, data, to); 424 offset += n; 425 if (n != copy) 426 goto short_copy; 427 if ((len -= copy) == 0) 428 return 0; 429 } 430 431 /* Copy paged appendix. Hmm... why does this look so complicated? */ 432 for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) { 433 int end; 434 const skb_frag_t *frag = &skb_shinfo(skb)->frags[i]; 435 436 WARN_ON(start > offset + len); 437 438 end = start + skb_frag_size(frag); 439 if ((copy = end - offset) > 0) { 440 struct page *page = skb_frag_page(frag); 441 u8 *vaddr = kmap(page); 442 443 if (copy > len) 444 copy = len; 445 n = cb(vaddr + skb_frag_off(frag) + offset - start, 446 copy, data, to); 447 kunmap(page); 448 offset += n; 449 if (n != copy) 450 goto short_copy; 451 if (!(len -= copy)) 452 return 0; 453 } 454 start = end; 455 } 456 457 skb_walk_frags(skb, frag_iter) { 458 int end; 459 460 WARN_ON(start > offset + len); 461 462 end = start + frag_iter->len; 463 if ((copy = end - offset) > 0) { 464 if (copy > len) 465 copy = len; 466 if (__skb_datagram_iter(frag_iter, offset - start, 467 to, copy, fault_short, cb, data)) 468 goto fault; 469 if ((len -= copy) == 0) 470 return 0; 471 offset += copy; 472 } 473 start = end; 474 } 475 if (!len) 476 return 0; 477 478 /* This is not really a user copy fault, but rather someone 479 * gave us a bogus length on the skb. We should probably 480 * print a warning here as it may indicate a kernel bug. 481 */ 482 483 fault: 484 iov_iter_revert(to, offset - start_off); 485 return -EFAULT; 486 487 short_copy: 488 if (fault_short || iov_iter_count(to)) 489 goto fault; 490 491 return 0; 492 } 493 494 /** 495 * skb_copy_and_hash_datagram_iter - Copy datagram to an iovec iterator 496 * and update a hash. 497 * @skb: buffer to copy 498 * @offset: offset in the buffer to start copying from 499 * @to: iovec iterator to copy to 500 * @len: amount of data to copy from buffer to iovec 501 * @hash: hash request to update 502 */ 503 int skb_copy_and_hash_datagram_iter(const struct sk_buff *skb, int offset, 504 struct iov_iter *to, int len, 505 struct ahash_request *hash) 506 { 507 return __skb_datagram_iter(skb, offset, to, len, true, 508 hash_and_copy_to_iter, hash); 509 } 510 EXPORT_SYMBOL(skb_copy_and_hash_datagram_iter); 511 512 static size_t simple_copy_to_iter(const void *addr, size_t bytes, 513 void *data __always_unused, struct iov_iter *i) 514 { 515 return copy_to_iter(addr, bytes, i); 516 } 517 518 /** 519 * skb_copy_datagram_iter - Copy a datagram to an iovec iterator. 520 * @skb: buffer to copy 521 * @offset: offset in the buffer to start copying from 522 * @to: iovec iterator to copy to 523 * @len: amount of data to copy from buffer to iovec 524 */ 525 int skb_copy_datagram_iter(const struct sk_buff *skb, int offset, 526 struct iov_iter *to, int len) 527 { 528 trace_skb_copy_datagram_iovec(skb, len); 529 return __skb_datagram_iter(skb, offset, to, len, false, 530 simple_copy_to_iter, NULL); 531 } 532 EXPORT_SYMBOL(skb_copy_datagram_iter); 533 534 /** 535 * skb_copy_datagram_from_iter - Copy a datagram from an iov_iter. 536 * @skb: buffer to copy 537 * @offset: offset in the buffer to start copying to 538 * @from: the copy source 539 * @len: amount of data to copy to buffer from iovec 540 * 541 * Returns 0 or -EFAULT. 542 */ 543 int skb_copy_datagram_from_iter(struct sk_buff *skb, int offset, 544 struct iov_iter *from, 545 int len) 546 { 547 int start = skb_headlen(skb); 548 int i, copy = start - offset; 549 struct sk_buff *frag_iter; 550 551 /* Copy header. */ 552 if (copy > 0) { 553 if (copy > len) 554 copy = len; 555 if (copy_from_iter(skb->data + offset, copy, from) != copy) 556 goto fault; 557 if ((len -= copy) == 0) 558 return 0; 559 offset += copy; 560 } 561 562 /* Copy paged appendix. Hmm... why does this look so complicated? */ 563 for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) { 564 int end; 565 const skb_frag_t *frag = &skb_shinfo(skb)->frags[i]; 566 567 WARN_ON(start > offset + len); 568 569 end = start + skb_frag_size(frag); 570 if ((copy = end - offset) > 0) { 571 size_t copied; 572 573 if (copy > len) 574 copy = len; 575 copied = copy_page_from_iter(skb_frag_page(frag), 576 skb_frag_off(frag) + offset - start, 577 copy, from); 578 if (copied != copy) 579 goto fault; 580 581 if (!(len -= copy)) 582 return 0; 583 offset += copy; 584 } 585 start = end; 586 } 587 588 skb_walk_frags(skb, frag_iter) { 589 int end; 590 591 WARN_ON(start > offset + len); 592 593 end = start + frag_iter->len; 594 if ((copy = end - offset) > 0) { 595 if (copy > len) 596 copy = len; 597 if (skb_copy_datagram_from_iter(frag_iter, 598 offset - start, 599 from, copy)) 600 goto fault; 601 if ((len -= copy) == 0) 602 return 0; 603 offset += copy; 604 } 605 start = end; 606 } 607 if (!len) 608 return 0; 609 610 fault: 611 return -EFAULT; 612 } 613 EXPORT_SYMBOL(skb_copy_datagram_from_iter); 614 615 int __zerocopy_sg_from_iter(struct sock *sk, struct sk_buff *skb, 616 struct iov_iter *from, size_t length) 617 { 618 int frag = skb_shinfo(skb)->nr_frags; 619 620 while (length && iov_iter_count(from)) { 621 struct page *pages[MAX_SKB_FRAGS]; 622 size_t start; 623 ssize_t copied; 624 unsigned long truesize; 625 int n = 0; 626 627 if (frag == MAX_SKB_FRAGS) 628 return -EMSGSIZE; 629 630 copied = iov_iter_get_pages(from, pages, length, 631 MAX_SKB_FRAGS - frag, &start); 632 if (copied < 0) 633 return -EFAULT; 634 635 iov_iter_advance(from, copied); 636 length -= copied; 637 638 truesize = PAGE_ALIGN(copied + start); 639 skb->data_len += copied; 640 skb->len += copied; 641 skb->truesize += truesize; 642 if (sk && sk->sk_type == SOCK_STREAM) { 643 sk_wmem_queued_add(sk, truesize); 644 sk_mem_charge(sk, truesize); 645 } else { 646 refcount_add(truesize, &skb->sk->sk_wmem_alloc); 647 } 648 while (copied) { 649 int size = min_t(int, copied, PAGE_SIZE - start); 650 skb_fill_page_desc(skb, frag++, pages[n], start, size); 651 start = 0; 652 copied -= size; 653 n++; 654 } 655 } 656 return 0; 657 } 658 EXPORT_SYMBOL(__zerocopy_sg_from_iter); 659 660 /** 661 * zerocopy_sg_from_iter - Build a zerocopy datagram from an iov_iter 662 * @skb: buffer to copy 663 * @from: the source to copy from 664 * 665 * The function will first copy up to headlen, and then pin the userspace 666 * pages and build frags through them. 667 * 668 * Returns 0, -EFAULT or -EMSGSIZE. 669 */ 670 int zerocopy_sg_from_iter(struct sk_buff *skb, struct iov_iter *from) 671 { 672 int copy = min_t(int, skb_headlen(skb), iov_iter_count(from)); 673 674 /* copy up to skb headlen */ 675 if (skb_copy_datagram_from_iter(skb, 0, from, copy)) 676 return -EFAULT; 677 678 return __zerocopy_sg_from_iter(NULL, skb, from, ~0U); 679 } 680 EXPORT_SYMBOL(zerocopy_sg_from_iter); 681 682 /** 683 * skb_copy_and_csum_datagram_iter - Copy datagram to an iovec iterator 684 * and update a checksum. 685 * @skb: buffer to copy 686 * @offset: offset in the buffer to start copying from 687 * @to: iovec iterator to copy to 688 * @len: amount of data to copy from buffer to iovec 689 * @csump: checksum pointer 690 */ 691 static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset, 692 struct iov_iter *to, int len, 693 __wsum *csump) 694 { 695 return __skb_datagram_iter(skb, offset, to, len, true, 696 csum_and_copy_to_iter, csump); 697 } 698 699 /** 700 * skb_copy_and_csum_datagram_msg - Copy and checksum skb to user iovec. 701 * @skb: skbuff 702 * @hlen: hardware length 703 * @msg: destination 704 * 705 * Caller _must_ check that skb will fit to this iovec. 706 * 707 * Returns: 0 - success. 708 * -EINVAL - checksum failure. 709 * -EFAULT - fault during copy. 710 */ 711 int skb_copy_and_csum_datagram_msg(struct sk_buff *skb, 712 int hlen, struct msghdr *msg) 713 { 714 __wsum csum; 715 int chunk = skb->len - hlen; 716 717 if (!chunk) 718 return 0; 719 720 if (msg_data_left(msg) < chunk) { 721 if (__skb_checksum_complete(skb)) 722 return -EINVAL; 723 if (skb_copy_datagram_msg(skb, hlen, msg, chunk)) 724 goto fault; 725 } else { 726 csum = csum_partial(skb->data, hlen, skb->csum); 727 if (skb_copy_and_csum_datagram(skb, hlen, &msg->msg_iter, 728 chunk, &csum)) 729 goto fault; 730 731 if (csum_fold(csum)) { 732 iov_iter_revert(&msg->msg_iter, chunk); 733 return -EINVAL; 734 } 735 736 if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE) && 737 !skb->csum_complete_sw) 738 netdev_rx_csum_fault(NULL, skb); 739 } 740 return 0; 741 fault: 742 return -EFAULT; 743 } 744 EXPORT_SYMBOL(skb_copy_and_csum_datagram_msg); 745 746 /** 747 * datagram_poll - generic datagram poll 748 * @file: file struct 749 * @sock: socket 750 * @wait: poll table 751 * 752 * Datagram poll: Again totally generic. This also handles 753 * sequenced packet sockets providing the socket receive queue 754 * is only ever holding data ready to receive. 755 * 756 * Note: when you *don't* use this routine for this protocol, 757 * and you use a different write policy from sock_writeable() 758 * then please supply your own write_space callback. 759 */ 760 __poll_t datagram_poll(struct file *file, struct socket *sock, 761 poll_table *wait) 762 { 763 struct sock *sk = sock->sk; 764 __poll_t mask; 765 766 sock_poll_wait(file, sock, wait); 767 mask = 0; 768 769 /* exceptional events? */ 770 if (sk->sk_err || !skb_queue_empty_lockless(&sk->sk_error_queue)) 771 mask |= EPOLLERR | 772 (sock_flag(sk, SOCK_SELECT_ERR_QUEUE) ? EPOLLPRI : 0); 773 774 if (sk->sk_shutdown & RCV_SHUTDOWN) 775 mask |= EPOLLRDHUP | EPOLLIN | EPOLLRDNORM; 776 if (sk->sk_shutdown == SHUTDOWN_MASK) 777 mask |= EPOLLHUP; 778 779 /* readable? */ 780 if (!skb_queue_empty_lockless(&sk->sk_receive_queue)) 781 mask |= EPOLLIN | EPOLLRDNORM; 782 783 /* Connection-based need to check for termination and startup */ 784 if (connection_based(sk)) { 785 if (sk->sk_state == TCP_CLOSE) 786 mask |= EPOLLHUP; 787 /* connection hasn't started yet? */ 788 if (sk->sk_state == TCP_SYN_SENT) 789 return mask; 790 } 791 792 /* writable? */ 793 if (sock_writeable(sk)) 794 mask |= EPOLLOUT | EPOLLWRNORM | EPOLLWRBAND; 795 else 796 sk_set_bit(SOCKWQ_ASYNC_NOSPACE, sk); 797 798 return mask; 799 } 800 EXPORT_SYMBOL(datagram_poll); 801