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Commit 869e7c62 authored by Hannes Frederic Sowa's avatar Hannes Frederic Sowa Committed by David S. Miller
Browse files

net: af_unix: implement stream sendpage support 



This patch implements sendpage support for AF_UNIX SOCK_STREAM
sockets. This is also required for a complete splice implementation.

The implementation is a bit tricky because we append to already existing
skbs and so have to hold unix_sk->readlock to protect the reading side
from either advancing UNIXCB.consumed or freeing the skb at the socket
receive tail.

Signed-off-by: default avatarHannes Frederic Sowa <hannes@stressinduktion.org>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent be12a1fe

net/unix/af_unix.c

+98 −1
Original line number Diff line number Diff line
@@ -518,6 +518,8 @@ static int unix_ioctl(struct socket *, unsigned int, unsigned long); 
static int unix_shutdown(struct socket *, int);

static int unix_stream_sendmsg(struct socket *, struct msghdr *, size_t);

static int unix_stream_recvmsg(struct socket *, struct msghdr *, size_t, int);

static ssize_t unix_stream_sendpage(struct socket *, struct page *, int offset,

				    size_t size, int flags);

static int unix_dgram_sendmsg(struct socket *, struct msghdr *, size_t);

static int unix_dgram_recvmsg(struct socket *, struct msghdr *, size_t, int);

static int unix_dgram_connect(struct socket *, struct sockaddr *,
@@ -558,7 +560,7 @@ static const struct proto_ops unix_stream_ops = { 
	.sendmsg =	unix_stream_sendmsg,

	.recvmsg =	unix_stream_recvmsg,

	.mmap =		sock_no_mmap,

	.sendpage =	sock_no_sendpage,

	.sendpage =	unix_stream_sendpage,

	.set_peek_off =	unix_set_peek_off,

};
@@ -1720,6 +1722,101 @@ static int unix_stream_sendmsg(struct socket *sock, struct msghdr *msg, 
	return sent ? : err;

}



static ssize_t unix_stream_sendpage(struct socket *socket, struct page *page,

				    int offset, size_t size, int flags)

{

	int err = 0;

	bool send_sigpipe = true;

	struct sock *other, *sk = socket->sk;

	struct sk_buff *skb, *newskb = NULL, *tail = NULL;



	if (flags & MSG_OOB)

		return -EOPNOTSUPP;



	other = unix_peer(sk);

	if (!other || sk->sk_state != TCP_ESTABLISHED)

		return -ENOTCONN;



	if (false) {

alloc_skb:

		unix_state_unlock(other);

		mutex_unlock(&unix_sk(other)->readlock);

		newskb = sock_alloc_send_pskb(sk, 0, 0, flags & MSG_DONTWAIT,

					      &err, 0);

		if (!newskb)

			return err;

	}



	/* we must acquire readlock as we modify already present

	 * skbs in the sk_receive_queue and mess with skb->len

	 */

	err = mutex_lock_interruptible(&unix_sk(other)->readlock);

	if (err) {

		err = flags & MSG_DONTWAIT ? -EAGAIN : -ERESTARTSYS;

		send_sigpipe = false;

		goto err;

	}



	if (sk->sk_shutdown & SEND_SHUTDOWN) {

		err = -EPIPE;

		goto err_unlock;

	}



	unix_state_lock(other);



	if (sock_flag(other, SOCK_DEAD) ||

	    other->sk_shutdown & RCV_SHUTDOWN) {

		err = -EPIPE;

		goto err_state_unlock;

	}



	skb = skb_peek_tail(&other->sk_receive_queue);

	if (tail && tail == skb) {

		skb = newskb;

	} else if (!skb) {

		if (newskb)

			skb = newskb;

		else

			goto alloc_skb;

	} else if (newskb) {

		/* this is fast path, we don't necessarily need to

		 * call to kfree_skb even though with newskb == NULL

		 * this - does no harm

		 */

		consume_skb(newskb);

	}



	if (skb_append_pagefrags(skb, page, offset, size)) {

		tail = skb;

		goto alloc_skb;

	}



	skb->len += size;

	skb->data_len += size;

	skb->truesize += size;

	atomic_add(size, &sk->sk_wmem_alloc);



	if (newskb)

		__skb_queue_tail(&other->sk_receive_queue, newskb);



	unix_state_unlock(other);

	mutex_unlock(&unix_sk(other)->readlock);



	other->sk_data_ready(other);



	return size;



err_state_unlock:

	unix_state_unlock(other);

err_unlock:

	mutex_unlock(&unix_sk(other)->readlock);

err:

	kfree_skb(newskb);

	if (send_sigpipe && !(flags & MSG_NOSIGNAL))

		send_sig(SIGPIPE, current, 0);

	return err;

}



static int unix_seqpacket_sendmsg(struct socket *sock, struct msghdr *msg,

				  size_t len)

{