1/*
2 *	SUCS NET3:
3 *
4 *	Generic datagram handling routines. These are generic for all
5 *	protocols. Possibly a generic IP version on top of these would
6 *	make sense. Not tonight however 8-).
7 *	This is used because UDP, RAW, PACKET, DDP, IPX, AX.25 and
8 *	NetROM layer all have identical poll code and mostly
9 *	identical recvmsg() code. So we share it here. The poll was
10 *	shared before but buried in udp.c so I moved it.
11 *
12 *	Authors:	Alan Cox <alan@redhat.com>. (datagram_poll() from old
13 *						     udp.c code)
14 *
15 *	Fixes:
16 *		Alan Cox	:	NULL return from skb_peek_copy()
17 *					understood
18 *		Alan Cox	:	Rewrote skb_read_datagram to avoid the
19 *					skb_peek_copy stuff.
20 *		Alan Cox	:	Added support for SOCK_SEQPACKET.
21 *					IPX can no longer use the SO_TYPE hack
22 *					but AX.25 now works right, and SPX is
23 *					feasible.
24 *		Alan Cox	:	Fixed write poll of non IP protocol
25 *					crash.
26 *		Florian  La Roche:	Changed for my new skbuff handling.
27 *		Darryl Miles	:	Fixed non-blocking SOCK_SEQPACKET.
28 *		Linus Torvalds	:	BSD semantic fixes.
29 *		Alan Cox	:	Datagram iovec handling
30 *		Darryl Miles	:	Fixed non-blocking SOCK_STREAM.
31 *		Alan Cox	:	POSIXisms
32 *		Pete Wyckoff    :       Unconnected accept() fix.
33 *
34 */
35
36#include <linux/module.h>
37#include <linux/types.h>
38#include <linux/kernel.h>
39#include <asm/uaccess.h>
40#include <asm/system.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
52#include <net/protocol.h>
53#include <linux/skbuff.h>
54
55#include <net/checksum.h>
56#include <net/sock.h>
57#include <net/tcp_states.h>
58
59/*
60 *	Is a socket 'connection oriented' ?
61 */
62static inline int connection_based(struct sock *sk)
63{
64	return sk->sk_type == SOCK_SEQPACKET || sk->sk_type == SOCK_STREAM;
65}
66
67/*
68 * Wait for a packet..
69 */
70static int wait_for_packet(struct sock *sk, int *err, long *timeo_p)
71{
72	int error;
73	DEFINE_WAIT(wait);
74
75	prepare_to_wait_exclusive(sk->sk_sleep, &wait, TASK_INTERRUPTIBLE);
76
77	/* Socket errors? */
78	error = sock_error(sk);
79	if (error)
80		goto out_err;
81
82	if (!skb_queue_empty(&sk->sk_receive_queue))
83		goto out;
84
85	/* Socket shut down? */
86	if (sk->sk_shutdown & RCV_SHUTDOWN)
87		goto out_noerr;
88
89	/* Sequenced packets can come disconnected.
90	 * If so we report the problem
91	 */
92	error = -ENOTCONN;
93	if (connection_based(sk) &&
94	    !(sk->sk_state == TCP_ESTABLISHED || sk->sk_state == TCP_LISTEN))
95		goto out_err;
96
97	/* handle signals */
98	if (signal_pending(current))
99		goto interrupted;
100
101	error = 0;
102	*timeo_p = schedule_timeout(*timeo_p);
103out:
104	finish_wait(sk->sk_sleep, &wait);
105	return error;
106interrupted:
107	error = sock_intr_errno(*timeo_p);
108out_err:
109	*err = error;
110	goto out;
111out_noerr:
112	*err = 0;
113	error = 1;
114	goto out;
115}
116
117/**
118 *	skb_recv_datagram - Receive a datagram skbuff
119 *	@sk: socket
120 *	@flags: MSG_ flags
121 *	@noblock: blocking operation?
122 *	@err: error code returned
123 *
124 *	Get a datagram skbuff, understands the peeking, nonblocking wakeups
125 *	and possible races. This replaces identical code in packet, raw and
126 *	udp, as well as the IPX AX.25 and Appletalk. It also finally fixes
127 *	the long standing peek and read race for datagram sockets. If you
128 *	alter this routine remember it must be re-entrant.
129 *
130 *	This function will lock the socket if a skb is returned, so the caller
131 *	needs to unlock the socket in that case (usually by calling
132 *	skb_free_datagram)
133 *
134 *	* It does not lock socket since today. This function is
135 *	* free of race conditions. This measure should/can improve
136 *	* significantly datagram socket latencies at high loads,
137 *	* when data copying to user space takes lots of time.
138 *	* (BTW I've just killed the last cli() in IP/IPv6/core/netlink/packet
139 *	*  8) Great win.)
140 *	*			                    --ANK (980729)
141 *
142 *	The order of the tests when we find no data waiting are specified
143 *	quite explicitly by POSIX 1003.1g, don't change them without having
144 *	the standard around please.
145 */
146struct sk_buff *skb_recv_datagram(struct sock *sk, unsigned flags,
147				  int noblock, int *err)
148{
149	struct sk_buff *skb;
150	long timeo;
151	/*
152	 * Caller is allowed not to check sk->sk_err before skb_recv_datagram()
153	 */
154	int error = sock_error(sk);
155
156	if (error)
157		goto no_packet;
158
159	timeo = sock_rcvtimeo(sk, noblock);
160
161	do {
162		/* Again only user level code calls this function, so nothing
163		 * interrupt level will suddenly eat the receive_queue.
164		 *
165		 * Look at current nfs client by the way...
166		 * However, this function was corrent in any case. 8)
167		 */
168		if (flags & MSG_PEEK) {
169			unsigned long cpu_flags;
170
171			spin_lock_irqsave(&sk->sk_receive_queue.lock,
172					  cpu_flags);
173			skb = skb_peek(&sk->sk_receive_queue);
174			if (skb)
175				atomic_inc(&skb->users);
176			spin_unlock_irqrestore(&sk->sk_receive_queue.lock,
177					       cpu_flags);
178		} else
179			skb = skb_dequeue(&sk->sk_receive_queue);
180
181		if (skb)
182			return skb;
183
184		/* User doesn't want to wait */
185		error = -EAGAIN;
186		if (!timeo)
187			goto no_packet;
188
189	} while (!wait_for_packet(sk, err, &timeo));
190
191	return NULL;
192
193no_packet:
194	*err = error;
195	return NULL;
196}
197
198void skb_free_datagram(struct sock *sk, struct sk_buff *skb)
199{
200	kfree_skb(skb);
201}
202
203/**
204 *	skb_kill_datagram - Free a datagram skbuff forcibly
205 *	@sk: socket
206 *	@skb: datagram skbuff
207 *	@flags: MSG_ flags
208 *
209 *	This function frees a datagram skbuff that was received by
210 *	skb_recv_datagram.  The flags argument must match the one
211 *	used for skb_recv_datagram.
212 *
213 *	If the MSG_PEEK flag is set, and the packet is still on the
214 *	receive queue of the socket, it will be taken off the queue
215 *	before it is freed.
216 *
217 *	This function currently only disables BH when acquiring the
218 *	sk_receive_queue lock.  Therefore it must not be used in a
219 *	context where that lock is acquired in an IRQ context.
220 */
221
222void skb_kill_datagram(struct sock *sk, struct sk_buff *skb, unsigned int flags)
223{
224	if (flags & MSG_PEEK) {
225		spin_lock_bh(&sk->sk_receive_queue.lock);
226		if (skb == skb_peek(&sk->sk_receive_queue)) {
227			__skb_unlink(skb, &sk->sk_receive_queue);
228			atomic_dec(&skb->users);
229		}
230		spin_unlock_bh(&sk->sk_receive_queue.lock);
231	}
232
233	kfree_skb(skb);
234}
235
236EXPORT_SYMBOL(skb_kill_datagram);
237
238/**
239 *	skb_copy_datagram_iovec - Copy a datagram to an iovec.
240 *	@skb: buffer to copy
241 *	@offset: offset in the buffer to start copying from
242 *	@to: io vector to copy to
243 *	@len: amount of data to copy from buffer to iovec
244 *
245 *	Note: the iovec is modified during the copy.
246 */
247int skb_copy_datagram_iovec(const struct sk_buff *skb, int offset,
248			    struct iovec *to, int len)
249{
250	int start = skb_headlen(skb);
251	int i, copy = start - offset;
252
253	/* Copy header. */
254	if (copy > 0) {
255		if (copy > len)
256			copy = len;
257		if (memcpy_toiovec(to, skb->data + offset, copy))
258			goto fault;
259		if ((len -= copy) == 0)
260			return 0;
261		offset += copy;
262	}
263
264	/* Copy paged appendix. Hmm... why does this look so complicated? */
265	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
266		int end;
267
268		BUG_TRAP(start <= offset + len);
269
270		end = start + skb_shinfo(skb)->frags[i].size;
271		if ((copy = end - offset) > 0) {
272			int err;
273			u8  *vaddr;
274			skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
275			struct page *page = frag->page;
276
277			if (copy > len)
278				copy = len;
279			vaddr = kmap(page);
280			err = memcpy_toiovec(to, vaddr + frag->page_offset +
281					     offset - start, copy);
282			kunmap(page);
283			if (err)
284				goto fault;
285			if (!(len -= copy))
286				return 0;
287			offset += copy;
288		}
289		start = end;
290	}
291
292	if (skb_shinfo(skb)->frag_list) {
293		struct sk_buff *list = skb_shinfo(skb)->frag_list;
294
295		for (; list; list = list->next) {
296			int end;
297
298			BUG_TRAP(start <= offset + len);
299
300			end = start + list->len;
301			if ((copy = end - offset) > 0) {
302				if (copy > len)
303					copy = len;
304				if (skb_copy_datagram_iovec(list,
305							    offset - start,
306							    to, copy))
307					goto fault;
308				if ((len -= copy) == 0)
309					return 0;
310				offset += copy;
311			}
312			start = end;
313		}
314	}
315	if (!len)
316		return 0;
317
318fault:
319	return -EFAULT;
320}
321
322static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset,
323				      u8 __user *to, int len,
324				      __wsum *csump)
325{
326	int start = skb_headlen(skb);
327	int pos = 0;
328	int i, copy = start - offset;
329
330	/* Copy header. */
331	if (copy > 0) {
332		int err = 0;
333		if (copy > len)
334			copy = len;
335		*csump = csum_and_copy_to_user(skb->data + offset, to, copy,
336					       *csump, &err);
337		if (err)
338			goto fault;
339		if ((len -= copy) == 0)
340			return 0;
341		offset += copy;
342		to += copy;
343		pos = copy;
344	}
345
346	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
347		int end;
348
349		BUG_TRAP(start <= offset + len);
350
351		end = start + skb_shinfo(skb)->frags[i].size;
352		if ((copy = end - offset) > 0) {
353			__wsum csum2;
354			int err = 0;
355			u8  *vaddr;
356			skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
357			struct page *page = frag->page;
358
359			if (copy > len)
360				copy = len;
361			vaddr = kmap(page);
362			csum2 = csum_and_copy_to_user(vaddr +
363							frag->page_offset +
364							offset - start,
365						      to, copy, 0, &err);
366			kunmap(page);
367			if (err)
368				goto fault;
369			*csump = csum_block_add(*csump, csum2, pos);
370			if (!(len -= copy))
371				return 0;
372			offset += copy;
373			to += copy;
374			pos += copy;
375		}
376		start = end;
377	}
378
379	if (skb_shinfo(skb)->frag_list) {
380		struct sk_buff *list = skb_shinfo(skb)->frag_list;
381
382		for (; list; list=list->next) {
383			int end;
384
385			BUG_TRAP(start <= offset + len);
386
387			end = start + list->len;
388			if ((copy = end - offset) > 0) {
389				__wsum csum2 = 0;
390				if (copy > len)
391					copy = len;
392				if (skb_copy_and_csum_datagram(list,
393							       offset - start,
394							       to, copy,
395							       &csum2))
396					goto fault;
397				*csump = csum_block_add(*csump, csum2, pos);
398				if ((len -= copy) == 0)
399					return 0;
400				offset += copy;
401				to += copy;
402				pos += copy;
403			}
404			start = end;
405		}
406	}
407	if (!len)
408		return 0;
409
410fault:
411	return -EFAULT;
412}
413
414__sum16 __skb_checksum_complete_head(struct sk_buff *skb, int len)
415{
416	__sum16 sum;
417
418	sum = csum_fold(skb_checksum(skb, 0, len, skb->csum));
419	if (likely(!sum)) {
420		if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE))
421			netdev_rx_csum_fault(skb->dev);
422		skb->ip_summed = CHECKSUM_UNNECESSARY;
423	}
424	return sum;
425}
426EXPORT_SYMBOL(__skb_checksum_complete_head);
427
428__sum16 __skb_checksum_complete(struct sk_buff *skb)
429{
430	return __skb_checksum_complete_head(skb, skb->len);
431}
432EXPORT_SYMBOL(__skb_checksum_complete);
433
434/**
435 *	skb_copy_and_csum_datagram_iovec - Copy and checkum skb to user iovec.
436 *	@skb: skbuff
437 *	@hlen: hardware length
438 *	@iov: io vector
439 *
440 *	Caller _must_ check that skb will fit to this iovec.
441 *
442 *	Returns: 0       - success.
443 *		 -EINVAL - checksum failure.
444 *		 -EFAULT - fault during copy. Beware, in this case iovec
445 *			   can be modified!
446 */
447int skb_copy_and_csum_datagram_iovec(struct sk_buff *skb,
448				     int hlen, struct iovec *iov)
449{
450	__wsum csum;
451	int chunk = skb->len - hlen;
452
453	/* Skip filled elements.
454	 * Pretty silly, look at memcpy_toiovec, though 8)
455	 */
456	while (!iov->iov_len)
457		iov++;
458
459	if (iov->iov_len < chunk) {
460		if (__skb_checksum_complete(skb))
461			goto csum_error;
462		if (skb_copy_datagram_iovec(skb, hlen, iov, chunk))
463			goto fault;
464	} else {
465		csum = csum_partial(skb->data, hlen, skb->csum);
466		if (skb_copy_and_csum_datagram(skb, hlen, iov->iov_base,
467					       chunk, &csum))
468			goto fault;
469		if (csum_fold(csum))
470			goto csum_error;
471		if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE))
472			netdev_rx_csum_fault(skb->dev);
473		iov->iov_len -= chunk;
474		iov->iov_base += chunk;
475	}
476	return 0;
477csum_error:
478	return -EINVAL;
479fault:
480	return -EFAULT;
481}
482
483/**
484 * 	datagram_poll - generic datagram poll
485 *	@file: file struct
486 *	@sock: socket
487 *	@wait: poll table
488 *
489 *	Datagram poll: Again totally generic. This also handles
490 *	sequenced packet sockets providing the socket receive queue
491 *	is only ever holding data ready to receive.
492 *
493 *	Note: when you _don't_ use this routine for this protocol,
494 *	and you use a different write policy from sock_writeable()
495 *	then please supply your own write_space callback.
496 */
497unsigned int datagram_poll(struct file *file, struct socket *sock,
498			   poll_table *wait)
499{
500	struct sock *sk = sock->sk;
501	unsigned int mask;
502
503	poll_wait(file, sk->sk_sleep, wait);
504	mask = 0;
505
506	/* exceptional events? */
507	if (sk->sk_err || !skb_queue_empty(&sk->sk_error_queue))
508		mask |= POLLERR;
509	if (sk->sk_shutdown & RCV_SHUTDOWN)
510		mask |= POLLRDHUP;
511	if (sk->sk_shutdown == SHUTDOWN_MASK)
512		mask |= POLLHUP;
513
514	/* readable? */
515	if (!skb_queue_empty(&sk->sk_receive_queue) ||
516	    (sk->sk_shutdown & RCV_SHUTDOWN))
517		mask |= POLLIN | POLLRDNORM;
518
519	/* Connection-based need to check for termination and startup */
520	if (connection_based(sk)) {
521		if (sk->sk_state == TCP_CLOSE)
522			mask |= POLLHUP;
523		/* connection hasn't started yet? */
524		if (sk->sk_state == TCP_SYN_SENT)
525			return mask;
526	}
527
528	/* writable? */
529	if (sock_writeable(sk))
530		mask |= POLLOUT | POLLWRNORM | POLLWRBAND;
531	else
532		set_bit(SOCK_ASYNC_NOSPACE, &sk->sk_socket->flags);
533
534	return mask;
535}
536
537EXPORT_SYMBOL(datagram_poll);
538EXPORT_SYMBOL(skb_copy_and_csum_datagram_iovec);
539EXPORT_SYMBOL(skb_copy_datagram_iovec);
540EXPORT_SYMBOL(skb_free_datagram);
541EXPORT_SYMBOL(skb_recv_datagram);
542