- 根目录:
- net
- core
- datagram.c
/*
* 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 <alan@lxorguk.ukuu.org.uk>. (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 <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <asm/uaccess.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/rtnetlink.h>
#include <linux/poll.h>
#include <linux/highmem.h>
#include <linux/spinlock.h>
#include <linux/slab.h>
#include <linux/pagemap.h>
#include <linux/uio.h>
#include <net/protocol.h>
#include <linux/skbuff.h>
#include <net/checksum.h>
#include <net/sock.h>
#include <net/tcp_states.h>
#include <trace/events/skb.h>
#include <net/busy_poll.h>
/*
* 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_t *wait, unsigned int mode, int sync,
void *key)
{
unsigned long bits = (unsigned long)key;
/*
* Avoid a wakeup if event not interesting for us
*/
if (bits && !(bits & (POLLIN | POLLERR)))
return 0;
return autoremove_wake_function(wait, mode, sync, key);
}
/*
* Wait for the last received packet to be different from skb
*/
static int wait_for_more_packets(struct sock *sk, 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 (sk->sk_receive_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;
}
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;
}
/**
* __skb_recv_datagram - Receive a datagram skbuff
* @sk: socket
* @flags: MSG_ flags
* @peeked: returns non-zero if this packet has been seen before
* @off: an offset in bytes to peek skb from. Returns an offset
* within an skb where data actually starts
* @err: error code returned
*
* 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)
*
* * 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_recv_datagram(struct sock *sk, unsigned int flags,
int *peeked, int *off, int *err)
{
struct sk_buff_head *queue = &sk->sk_receive_queue;
struct sk_buff *skb, *last;
unsigned long cpu_flags;
long timeo;
/*
* Caller is allowed not to check sk->sk_err before skb_recv_datagram()
*/
int error = sock_error(sk);
if (error)
goto no_packet;
timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
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)
*/
int _off = *off;
last = (struct sk_buff *)queue;
spin_lock_irqsave(&queue->lock, cpu_flags);
skb_queue_walk(queue, skb) {
last = skb;
*peeked = skb->peeked;
if (flags & MSG_PEEK) {
if (_off >= skb->len && (skb->len || _off ||
skb->peeked)) {
_off -= skb->len;
continue;
}
skb = skb_set_peeked(skb);
error = PTR_ERR(skb);
if (IS_ERR(skb))
goto unlock_err;
atomic_inc(&skb->users);
} else
__skb_unlink(skb, queue);
spin_unlock_irqrestore(&queue->lock, cpu_flags);
*off = _off;
return skb;
}
spin_unlock_irqrestore(&queue->lock, cpu_flags);
if (sk_can_busy_loop(sk) &&
sk_busy_loop(sk, flags & MSG_DONTWAIT))
continue;
/* User doesn't want to wait */
error = -EAGAIN;
if (!timeo)
goto no_packet;
} while (!wait_for_more_packets(sk, err, &timeo, last));
return NULL;
unlock_err:
spin_unlock_irqrestore(&queue->lock, cpu_flags);
no_packet:
*err = error;
return NULL;
}
EXPORT_SYMBOL(__skb_recv_datagram);
struct sk_buff *skb_recv_datagram(struct sock *sk, unsigned int flags,
int noblock, int *err)
{
int peeked, off = 0;
return __skb_recv_datagram(sk, flags | (noblock ? MSG_DONTWAIT : 0),
&peeked, &off, err);
}
EXPORT_SYMBOL(skb_recv_datagram);
void skb_free_datagram(struct sock *sk, struct sk_buff *skb)
{
consume_skb(skb);
sk_mem_reclaim_partial(sk);
}
EXPORT_SYMBOL(skb_free_datagram);
void skb_free_datagram_locked(struct sock *sk, struct sk_buff *skb)
{
bool slow;
if (likely(atomic_read(&skb->users) == 1))
smp_rmb();
else if (likely(!atomic_dec_and_test(&skb->users)))
return;
slow = lock_sock_fast(sk);
skb_orphan(skb);
sk_mem_reclaim_partial(sk);
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);
/**
* 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 = 0;
if (flags & MSG_PEEK) {
err = -ENOENT;
spin_lock_bh(&sk->sk_receive_queue.lock);
if (skb == skb_peek(&sk->sk_receive_queue)) {
__skb_unlink(skb, &sk->sk_receive_queue);
atomic_dec(&skb->users);
err = 0;
}
spin_unlock_bh(&sk->sk_receive_queue.lock);
}
kfree_skb(skb);
atomic_inc(&sk->sk_drops);
sk_mem_reclaim_partial(sk);
return err;
}
EXPORT_SYMBOL(skb_kill_datagram);
/**
* 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)
{
int start = skb_headlen(skb);
int i, copy = start - offset;
struct sk_buff *frag_iter;
trace_skb_copy_datagram_iovec(skb, len);
/* Copy header. */
if (copy > 0) {
if (copy > len)
copy = len;
if (copy_to_iter(skb->data + offset, copy, to) != copy)
goto short_copy;
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) {
if (copy > len)
copy = len;
if (copy_page_to_iter(skb_frag_page(frag),
frag->page_offset + offset -
start, copy, to) != copy)
goto short_copy;
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_iter(frag_iter, offset - start,
to, copy))
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:
return -EFAULT;
short_copy:
if (iov_iter_count(to))
goto fault;
return 0;
}
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),
frag->page_offset + 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);
/**
* 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 len = iov_iter_count(from);
int copy = min_t(int, skb_headlen(skb), len);
int frag = 0;
/* copy up to skb headlen */
if (skb_copy_datagram_from_iter(skb, 0, from, copy))
return -EFAULT;
while (iov_iter_count(from)) {
struct page *pages[MAX_SKB_FRAGS];
size_t start;
ssize_t copied;
unsigned long truesize;
int n = 0;
if (frag == MAX_SKB_FRAGS)
return -EMSGSIZE;
copied = iov_iter_get_pages(from, pages, ~0U,
MAX_SKB_FRAGS - frag, &start);
if (copied < 0)
return -EFAULT;
iov_iter_advance(from, copied);
truesize = PAGE_ALIGN(copied + start);
skb->data_len += copied;
skb->len += copied;
skb->truesize += truesize;
atomic_add(truesize, &skb->sk->sk_wmem_alloc);
while (copied) {
int size = min_t(int, copied, PAGE_SIZE - start);
skb_fill_page_desc(skb, frag++, pages[n], start, size);
start = 0;
copied -= size;
n++;
}
}
return 0;
}
EXPORT_SYMBOL(zerocopy_sg_from_iter);
static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset,
struct iov_iter *to, int len,
__wsum *csump)
{
int start = skb_headlen(skb);
int i, copy = start - offset;
struct sk_buff *frag_iter;
int pos = 0;
int n;
/* Copy header. */
if (copy > 0) {
if (copy > len)
copy = len;
n = csum_and_copy_to_iter(skb->data + offset, copy, csump, to);
if (n != copy)
goto fault;
if ((len -= copy) == 0)
return 0;
offset += copy;
pos = copy;
}
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) {
__wsum csum2 = 0;
struct page *page = skb_frag_page(frag);
u8 *vaddr = kmap(page);
if (copy > len)
copy = len;
n = csum_and_copy_to_iter(vaddr + frag->page_offset +
offset - start, copy,
&csum2, to);
kunmap(page);
if (n != copy)
goto fault;
*csump = csum_block_add(*csump, csum2, pos);
if (!(len -= copy))
return 0;
offset += copy;
pos += 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) {
__wsum csum2 = 0;
if (copy > len)
copy = len;
if (skb_copy_and_csum_datagram(frag_iter,
offset - start,
to, copy,
&csum2))
goto fault;
*csump = csum_block_add(*csump, csum2, pos);
if ((len -= copy) == 0)
return 0;
offset += copy;
pos += copy;
}
start = end;
}
if (!len)
return 0;
fault:
return -EFAULT;
}
__sum16 __skb_checksum_complete_head(struct sk_buff *skb, int len)
{
__sum16 sum;
sum = csum_fold(skb_checksum(skb, 0, len, skb->csum));
if (likely(!sum)) {
if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE) &&
!skb->csum_complete_sw)
netdev_rx_csum_fault(skb->dev);
}
if (!skb_shared(skb))
skb->csum_valid = !sum;
return sum;
}
EXPORT_SYMBOL(__skb_checksum_complete_head);
__sum16 __skb_checksum_complete(struct sk_buff *skb)
{
__wsum csum;
__sum16 sum;
csum = skb_checksum(skb, 0, skb->len, 0);
/* skb->csum holds pseudo checksum */
sum = csum_fold(csum_add(skb->csum, csum));
if (likely(!sum)) {
if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE) &&
!skb->csum_complete_sw)
netdev_rx_csum_fault(skb->dev);
}
if (!skb_shared(skb)) {
/* Save full packet checksum */
skb->csum = csum;
skb->ip_summed = CHECKSUM_COMPLETE;
skb->csum_complete_sw = 1;
skb->csum_valid = !sum;
}
return sum;
}
EXPORT_SYMBOL(__skb_checksum_complete);
/**
* 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))
goto csum_error;
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))
goto csum_error;
if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE))
netdev_rx_csum_fault(skb->dev);
}
return 0;
csum_error:
return -EINVAL;
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.
*/
unsigned int datagram_poll(struct file *file, struct socket *sock,
poll_table *wait)
{
struct sock *sk = sock->sk;
unsigned int mask;
sock_poll_wait(file, sk_sleep(sk), wait);
mask = 0;
/* exceptional events? */
if (sk->sk_err || !skb_queue_empty(&sk->sk_error_queue))
mask |= POLLERR |
(sock_flag(sk, SOCK_SELECT_ERR_QUEUE) ? POLLPRI : 0);
if (sk->sk_shutdown & RCV_SHUTDOWN)
mask |= POLLRDHUP | POLLIN | POLLRDNORM;
if (sk->sk_shutdown == SHUTDOWN_MASK)
mask |= POLLHUP;
/* readable? */
if (!skb_queue_empty(&sk->sk_receive_queue))
mask |= POLLIN | POLLRDNORM;
/* Connection-based need to check for termination and startup */
if (connection_based(sk)) {
if (sk->sk_state == TCP_CLOSE)
mask |= POLLHUP;
/* connection hasn't started yet? */
if (sk->sk_state == TCP_SYN_SENT)
return mask;
}
/* writable? */
if (sock_writeable(sk))
mask |= POLLOUT | POLLWRNORM | POLLWRBAND;
else
sk_set_bit(SOCKWQ_ASYNC_NOSPACE, sk);
return mask;
}
EXPORT_SYMBOL(datagram_poll);