// SPDX-License-Identifier: GPL-2.0 /* * SUCS NET3: * * Generic datagram handling routines. These are generic for all * protocols. Possibly a generic IP version on top of these would * make sense. Not tonight however 8-). * This is used because UDP, RAW, PACKET, DDP, IPX, AX.25 and * NetROM layer all have identical poll code and mostly * identical recvmsg() code. So we share it here. The poll was * shared before but buried in udp.c so I moved it. * * Authors: Alan Cox . (datagram_poll() from old * udp.c code) * * Fixes: * Alan Cox : NULL return from skb_peek_copy() * understood * Alan Cox : Rewrote skb_read_datagram to avoid the * skb_peek_copy stuff. * Alan Cox : Added support for SOCK_SEQPACKET. * IPX can no longer use the SO_TYPE hack * but AX.25 now works right, and SPX is * feasible. * Alan Cox : Fixed write poll of non IP protocol * crash. * Florian La Roche: Changed for my new skbuff handling. * Darryl Miles : Fixed non-blocking SOCK_SEQPACKET. * Linus Torvalds : BSD semantic fixes. * Alan Cox : Datagram iovec handling * Darryl Miles : Fixed non-blocking SOCK_STREAM. * Alan Cox : POSIXisms * Pete Wyckoff : Unconnected accept() fix. * */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* * Is a socket 'connection oriented' ? */ static inline int connection_based(struct sock *sk) { return sk->sk_type == SOCK_SEQPACKET || sk->sk_type == SOCK_STREAM; } static int receiver_wake_function(wait_queue_entry_t *wait, unsigned int mode, int sync, void *key) { /* * Avoid a wakeup if event not interesting for us */ if (key && !(key_to_poll(key) & (EPOLLIN | EPOLLERR))) return 0; return autoremove_wake_function(wait, mode, sync, key); } /* * Wait for the last received packet to be different from skb */ int __skb_wait_for_more_packets(struct sock *sk, struct sk_buff_head *queue, int *err, long *timeo_p, const struct sk_buff *skb) { int error; DEFINE_WAIT_FUNC(wait, receiver_wake_function); prepare_to_wait_exclusive(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE); /* Socket errors? */ error = sock_error(sk); if (error) goto out_err; if (READ_ONCE(queue->prev) != skb) goto out; /* Socket shut down? */ if (sk->sk_shutdown & RCV_SHUTDOWN) goto out_noerr; /* Sequenced packets can come disconnected. * If so we report the problem */ error = -ENOTCONN; if (connection_based(sk) && !(sk->sk_state == TCP_ESTABLISHED || sk->sk_state == TCP_LISTEN)) goto out_err; /* handle signals */ if (signal_pending(current)) goto interrupted; error = 0; *timeo_p = schedule_timeout(*timeo_p); out: finish_wait(sk_sleep(sk), &wait); return error; interrupted: error = sock_intr_errno(*timeo_p); out_err: *err = error; goto out; out_noerr: *err = 0; error = 1; goto out; } EXPORT_SYMBOL(__skb_wait_for_more_packets); static struct sk_buff *skb_set_peeked(struct sk_buff *skb) { struct sk_buff *nskb; if (skb->peeked) return skb; /* We have to unshare an skb before modifying it. */ if (!skb_shared(skb)) goto done; nskb = skb_clone(skb, GFP_ATOMIC); if (!nskb) return ERR_PTR(-ENOMEM); skb->prev->next = nskb; skb->next->prev = nskb; nskb->prev = skb->prev; nskb->next = skb->next; consume_skb(skb); skb = nskb; done: skb->peeked = 1; return skb; } struct sk_buff *__skb_try_recv_from_queue(struct sock *sk, struct sk_buff_head *queue, unsigned int flags, int *off, int *err, struct sk_buff **last) { bool peek_at_off = false; struct sk_buff *skb; int _off = 0; if (unlikely(flags & MSG_PEEK && *off >= 0)) { peek_at_off = true; _off = *off; } *last = queue->prev; skb_queue_walk(queue, skb) { if (flags & MSG_PEEK) { if (peek_at_off && _off >= skb->len && (_off || skb->peeked)) { _off -= skb->len; continue; } if (!skb->len) { skb = skb_set_peeked(skb); if (IS_ERR(skb)) { *err = PTR_ERR(skb); return NULL; } } refcount_inc(&skb->users); } else { __skb_unlink(skb, queue); } *off = _off; return skb; } return NULL; } /** * __skb_try_recv_datagram - Receive a datagram skbuff * @sk: socket * @queue: socket queue from which to receive * @flags: MSG\_ flags * @off: an offset in bytes to peek skb from. Returns an offset * within an skb where data actually starts * @err: error code returned * @last: set to last peeked message to inform the wait function * what to look for when peeking * * Get a datagram skbuff, understands the peeking, nonblocking wakeups * and possible races. This replaces identical code in packet, raw and * udp, as well as the IPX AX.25 and Appletalk. It also finally fixes * the long standing peek and read race for datagram sockets. If you * alter this routine remember it must be re-entrant. * * This function will lock the socket if a skb is returned, so * the caller needs to unlock the socket in that case (usually by * calling skb_free_datagram). Returns NULL with @err set to * -EAGAIN if no data was available or to some other value if an * error was detected. * * * It does not lock socket since today. This function is * * free of race conditions. This measure should/can improve * * significantly datagram socket latencies at high loads, * * when data copying to user space takes lots of time. * * (BTW I've just killed the last cli() in IP/IPv6/core/netlink/packet * * 8) Great win.) * * --ANK (980729) * * The order of the tests when we find no data waiting are specified * quite explicitly by POSIX 1003.1g, don't change them without having * the standard around please. */ struct sk_buff *__skb_try_recv_datagram(struct sock *sk, struct sk_buff_head *queue, unsigned int flags, int *off, int *err, struct sk_buff **last) { struct sk_buff *skb; unsigned long cpu_flags; /* * Caller is allowed not to check sk->sk_err before skb_recv_datagram() */ int error = sock_error(sk); if (error) goto no_packet; do { /* Again only user level code calls this function, so nothing * interrupt level will suddenly eat the receive_queue. * * Look at current nfs client by the way... * However, this function was correct in any case. 8) */ spin_lock_irqsave(&queue->lock, cpu_flags); skb = __skb_try_recv_from_queue(sk, queue, flags, off, &error, last); spin_unlock_irqrestore(&queue->lock, cpu_flags); if (error) goto no_packet; if (skb) return skb; if (!sk_can_busy_loop(sk)) break; sk_busy_loop(sk, flags & MSG_DONTWAIT); } while (READ_ONCE(queue->prev) != *last); error = -EAGAIN; no_packet: *err = error; return NULL; } EXPORT_SYMBOL(__skb_try_recv_datagram); struct sk_buff *__skb_recv_datagram(struct sock *sk, struct sk_buff_head *sk_queue, unsigned int flags, int *off, int *err) { struct sk_buff *skb, *last; long timeo; timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT); do { skb = __skb_try_recv_datagram(sk, sk_queue, flags, off, err, &last); if (skb) return skb; if (*err != -EAGAIN) break; } while (timeo && !__skb_wait_for_more_packets(sk, sk_queue, err, &timeo, last)); return NULL; } EXPORT_SYMBOL(__skb_recv_datagram); struct sk_buff *skb_recv_datagram(struct sock *sk, unsigned int flags, int *err) { int off = 0; return __skb_recv_datagram(sk, &sk->sk_receive_queue, flags, &off, err); } EXPORT_SYMBOL(skb_recv_datagram); void skb_free_datagram(struct sock *sk, struct sk_buff *skb) { consume_skb(skb); } EXPORT_SYMBOL(skb_free_datagram); void __skb_free_datagram_locked(struct sock *sk, struct sk_buff *skb, int len) { bool slow; if (!skb_unref(skb)) { sk_peek_offset_bwd(sk, len); return; } slow = lock_sock_fast(sk); sk_peek_offset_bwd(sk, len); skb_orphan(skb); unlock_sock_fast(sk, slow); /* skb is now orphaned, can be freed outside of locked section */ __kfree_skb(skb); } EXPORT_SYMBOL(__skb_free_datagram_locked); int __sk_queue_drop_skb(struct sock *sk, struct sk_buff_head *sk_queue, struct sk_buff *skb, unsigned int flags, void (*destructor)(struct sock *sk, struct sk_buff *skb)) { int err = 0; if (flags & MSG_PEEK) { err = -ENOENT; spin_lock_bh(&sk_queue->lock); if (skb->next) { __skb_unlink(skb, sk_queue); refcount_dec(&skb->users); if (destructor) destructor(sk, skb); err = 0; } spin_unlock_bh(&sk_queue->lock); } atomic_inc(&sk->sk_drops); return err; } EXPORT_SYMBOL(__sk_queue_drop_skb); /** * skb_kill_datagram - Free a datagram skbuff forcibly * @sk: socket * @skb: datagram skbuff * @flags: MSG\_ flags * * This function frees a datagram skbuff that was received by * skb_recv_datagram. The flags argument must match the one * used for skb_recv_datagram. * * If the MSG_PEEK flag is set, and the packet is still on the * receive queue of the socket, it will be taken off the queue * before it is freed. * * This function currently only disables BH when acquiring the * sk_receive_queue lock. Therefore it must not be used in a * context where that lock is acquired in an IRQ context. * * It returns 0 if the packet was removed by us. */ int skb_kill_datagram(struct sock *sk, struct sk_buff *skb, unsigned int flags) { int err = __sk_queue_drop_skb(sk, &sk->sk_receive_queue, skb, flags, NULL); kfree_skb(skb); return err; } EXPORT_SYMBOL(skb_kill_datagram); INDIRECT_CALLABLE_DECLARE(static size_t simple_copy_to_iter(const void *addr, size_t bytes, void *data __always_unused, struct iov_iter *i)); static int __skb_datagram_iter(const struct sk_buff *skb, int offset, struct iov_iter *to, int len, bool fault_short, size_t (*cb)(const void *, size_t, void *, struct iov_iter *), void *data) { int start = skb_headlen(skb); int i, copy = start - offset, start_off = offset, n; struct sk_buff *frag_iter; /* Copy header. */ if (copy > 0) { if (copy > len) copy = len; n = INDIRECT_CALL_1(cb, simple_copy_to_iter, skb->data + offset, copy, data, to); offset += n; if (n != copy) goto short_copy; if ((len -= copy) == 0) return 0; } /* Copy paged appendix. Hmm... why does this look so complicated? */ for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) { int end; const skb_frag_t *frag = &skb_shinfo(skb)->frags[i]; WARN_ON(start > offset + len); end = start + skb_frag_size(frag); if ((copy = end - offset) > 0) { struct page *page = skb_frag_page(frag); u8 *vaddr = kmap(page); if (copy > len) copy = len; n = INDIRECT_CALL_1(cb, simple_copy_to_iter, vaddr + skb_frag_off(frag) + offset - start, copy, data, to); kunmap(page); offset += n; if (n != copy) goto short_copy; if (!(len -= copy)) return 0; } start = end; } skb_walk_frags(skb, frag_iter) { int end; WARN_ON(start > offset + len); end = start + frag_iter->len; if ((copy = end - offset) > 0) { if (copy > len) copy = len; if (__skb_datagram_iter(frag_iter, offset - start, to, copy, fault_short, cb, data)) goto fault; if ((len -= copy) == 0) return 0; offset += copy; } start = end; } if (!len) return 0; /* This is not really a user copy fault, but rather someone * gave us a bogus length on the skb. We should probably * print a warning here as it may indicate a kernel bug. */ fault: iov_iter_revert(to, offset - start_off); return -EFAULT; short_copy: if (fault_short || iov_iter_count(to)) goto fault; return 0; } /** * skb_copy_and_hash_datagram_iter - Copy datagram to an iovec iterator * and update a hash. * @skb: buffer to copy * @offset: offset in the buffer to start copying from * @to: iovec iterator to copy to * @len: amount of data to copy from buffer to iovec * @hash: hash request to update */ int skb_copy_and_hash_datagram_iter(const struct sk_buff *skb, int offset, struct iov_iter *to, int len, struct ahash_request *hash) { return __skb_datagram_iter(skb, offset, to, len, true, hash_and_copy_to_iter, hash); } EXPORT_SYMBOL(skb_copy_and_hash_datagram_iter); static size_t simple_copy_to_iter(const void *addr, size_t bytes, void *data __always_unused, struct iov_iter *i) { return copy_to_iter(addr, bytes, i); } /** * skb_copy_datagram_iter - Copy a datagram to an iovec iterator. * @skb: buffer to copy * @offset: offset in the buffer to start copying from * @to: iovec iterator to copy to * @len: amount of data to copy from buffer to iovec */ int skb_copy_datagram_iter(const struct sk_buff *skb, int offset, struct iov_iter *to, int len) { trace_skb_copy_datagram_iovec(skb, len); return __skb_datagram_iter(skb, offset, to, len, false, simple_copy_to_iter, NULL); } EXPORT_SYMBOL(skb_copy_datagram_iter); /** * skb_copy_datagram_from_iter - Copy a datagram from an iov_iter. * @skb: buffer to copy * @offset: offset in the buffer to start copying to * @from: the copy source * @len: amount of data to copy to buffer from iovec * * Returns 0 or -EFAULT. */ int skb_copy_datagram_from_iter(struct sk_buff *skb, int offset, struct iov_iter *from, int len) { int start = skb_headlen(skb); int i, copy = start - offset; struct sk_buff *frag_iter; /* Copy header. */ if (copy > 0) { if (copy > len) copy = len; if (copy_from_iter(skb->data + offset, copy, from) != copy) goto fault; if ((len -= copy) == 0) return 0; offset += copy; } /* Copy paged appendix. Hmm... why does this look so complicated? */ for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) { int end; const skb_frag_t *frag = &skb_shinfo(skb)->frags[i]; WARN_ON(start > offset + len); end = start + skb_frag_size(frag); if ((copy = end - offset) > 0) { size_t copied; if (copy > len) copy = len; copied = copy_page_from_iter(skb_frag_page(frag), skb_frag_off(frag) + offset - start, copy, from); if (copied != copy) goto fault; if (!(len -= copy)) return 0; offset += copy; } start = end; } skb_walk_frags(skb, frag_iter) { int end; WARN_ON(start > offset + len); end = start + frag_iter->len; if ((copy = end - offset) > 0) { if (copy > len) copy = len; if (skb_copy_datagram_from_iter(frag_iter, offset - start, from, copy)) goto fault; if ((len -= copy) == 0) return 0; offset += copy; } start = end; } if (!len) return 0; fault: return -EFAULT; } EXPORT_SYMBOL(skb_copy_datagram_from_iter); int __zerocopy_sg_from_iter(struct msghdr *msg, struct sock *sk, struct sk_buff *skb, struct iov_iter *from, size_t length) { int frag; if (msg && msg->msg_ubuf && msg->sg_from_iter) return msg->sg_from_iter(sk, skb, from, length); frag = skb_shinfo(skb)->nr_frags; while (length && iov_iter_count(from)) { struct page *pages[MAX_SKB_FRAGS]; struct page *last_head = NULL; size_t start; ssize_t copied; unsigned long truesize; int refs, n = 0; if (frag == MAX_SKB_FRAGS) return -EMSGSIZE; copied = iov_iter_get_pages2(from, pages, length, MAX_SKB_FRAGS - frag, &start); if (copied < 0) return -EFAULT; length -= copied; truesize = PAGE_ALIGN(copied + start); skb->data_len += copied; skb->len += copied; skb->truesize += truesize; if (sk && sk->sk_type == SOCK_STREAM) { sk_wmem_queued_add(sk, truesize); if (!skb_zcopy_pure(skb)) sk_mem_charge(sk, truesize); } else { refcount_add(truesize, &skb->sk->sk_wmem_alloc); } for (refs = 0; copied != 0; start = 0) { int size = min_t(int, copied, PAGE_SIZE - start); struct page *head = compound_head(pages[n]); start += (pages[n] - head) << PAGE_SHIFT; copied -= size; n++; if (frag) { skb_frag_t *last = &skb_shinfo(skb)->frags[frag - 1]; if (head == skb_frag_page(last) && start == skb_frag_off(last) + skb_frag_size(last)) { skb_frag_size_add(last, size); /* We combined this page, we need to release * a reference. Since compound pages refcount * is shared among many pages, batch the refcount * adjustments to limit false sharing. */ last_head = head; refs++; continue; } } if (refs) { page_ref_sub(last_head, refs); refs = 0; } skb_fill_page_desc_noacc(skb, frag++, head, start, size); } if (refs) page_ref_sub(last_head, refs); } return 0; } EXPORT_SYMBOL(__zerocopy_sg_from_iter); /** * zerocopy_sg_from_iter - Build a zerocopy datagram from an iov_iter * @skb: buffer to copy * @from: the source to copy from * * The function will first copy up to headlen, and then pin the userspace * pages and build frags through them. * * Returns 0, -EFAULT or -EMSGSIZE. */ int zerocopy_sg_from_iter(struct sk_buff *skb, struct iov_iter *from) { int copy = min_t(int, skb_headlen(skb), iov_iter_count(from)); /* copy up to skb headlen */ if (skb_copy_datagram_from_iter(skb, 0, from, copy)) return -EFAULT; return __zerocopy_sg_from_iter(NULL, NULL, skb, from, ~0U); } EXPORT_SYMBOL(zerocopy_sg_from_iter); /** * skb_copy_and_csum_datagram - Copy datagram to an iovec iterator * and update a checksum. * @skb: buffer to copy * @offset: offset in the buffer to start copying from * @to: iovec iterator to copy to * @len: amount of data to copy from buffer to iovec * @csump: checksum pointer */ static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset, struct iov_iter *to, int len, __wsum *csump) { struct csum_state csdata = { .csum = *csump }; int ret; ret = __skb_datagram_iter(skb, offset, to, len, true, csum_and_copy_to_iter, &csdata); if (ret) return ret; *csump = csdata.csum; return 0; } /** * skb_copy_and_csum_datagram_msg - Copy and checksum skb to user iovec. * @skb: skbuff * @hlen: hardware length * @msg: destination * * Caller _must_ check that skb will fit to this iovec. * * Returns: 0 - success. * -EINVAL - checksum failure. * -EFAULT - fault during copy. */ int skb_copy_and_csum_datagram_msg(struct sk_buff *skb, int hlen, struct msghdr *msg) { __wsum csum; int chunk = skb->len - hlen; if (!chunk) return 0; if (msg_data_left(msg) < chunk) { if (__skb_checksum_complete(skb)) return -EINVAL; if (skb_copy_datagram_msg(skb, hlen, msg, chunk)) goto fault; } else { csum = csum_partial(skb->data, hlen, skb->csum); if (skb_copy_and_csum_datagram(skb, hlen, &msg->msg_iter, chunk, &csum)) goto fault; if (csum_fold(csum)) { iov_iter_revert(&msg->msg_iter, chunk); return -EINVAL; } if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE) && !skb->csum_complete_sw) netdev_rx_csum_fault(NULL, skb); } return 0; fault: return -EFAULT; } EXPORT_SYMBOL(skb_copy_and_csum_datagram_msg); /** * datagram_poll - generic datagram poll * @file: file struct * @sock: socket * @wait: poll table * * Datagram poll: Again totally generic. This also handles * sequenced packet sockets providing the socket receive queue * is only ever holding data ready to receive. * * Note: when you *don't* use this routine for this protocol, * and you use a different write policy from sock_writeable() * then please supply your own write_space callback. */ __poll_t datagram_poll(struct file *file, struct socket *sock, poll_table *wait) { struct sock *sk = sock->sk; __poll_t mask; sock_poll_wait(file, sock, wait); mask = 0; /* exceptional events? */ if (sk->sk_err || !skb_queue_empty_lockless(&sk->sk_error_queue)) mask |= EPOLLERR | (sock_flag(sk, SOCK_SELECT_ERR_QUEUE) ? EPOLLPRI : 0); if (sk->sk_shutdown & RCV_SHUTDOWN) mask |= EPOLLRDHUP | EPOLLIN | EPOLLRDNORM; if (sk->sk_shutdown == SHUTDOWN_MASK) mask |= EPOLLHUP; /* readable? */ if (!skb_queue_empty_lockless(&sk->sk_receive_queue)) mask |= EPOLLIN | EPOLLRDNORM; /* Connection-based need to check for termination and startup */ if (connection_based(sk)) { if (sk->sk_state == TCP_CLOSE) mask |= EPOLLHUP; /* connection hasn't started yet? */ if (sk->sk_state == TCP_SYN_SENT) return mask; } /* writable? */ if (sock_writeable(sk)) mask |= EPOLLOUT | EPOLLWRNORM | EPOLLWRBAND; else sk_set_bit(SOCKWQ_ASYNC_NOSPACE, sk); return mask; } EXPORT_SYMBOL(datagram_poll);