Commit cd1df525 authored by Patrick McHardy's avatar Patrick McHardy Committed by David S. Miller
Browse files

netlink: add flow control for memory mapped I/O 



Add flow control for memory mapped RX. Since user-space usually doesn't
invoke recvmsg() when using memory mapped I/O, flow control is performed
in netlink_poll(). Dumps are allowed to continue if at least half of the
ring frames are unused.

Signed-off-by: default avatarPatrick McHardy <kaber@trash.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent f9c22888

net/netlink/af_netlink.c

+61 −27
Original line number Diff line number Diff line
@@ -3,6 +3,7 @@ 
 *

 * 		Authors:	Alan Cox <alan@lxorguk.ukuu.org.uk>

 * 				Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>

 * 				Patrick McHardy <kaber@trash.net>

 *

 *		This program is free software; you can redistribute it and/or

 *		modify it under the terms of the GNU General Public License
@@ -110,6 +111,29 @@ static inline struct hlist_head *nl_portid_hashfn(struct nl_portid_hash *hash, u 
	return &hash->table[jhash_1word(portid, hash->rnd) & hash->mask];

}



static void netlink_overrun(struct sock *sk)

{

	struct netlink_sock *nlk = nlk_sk(sk);



	if (!(nlk->flags & NETLINK_RECV_NO_ENOBUFS)) {

		if (!test_and_set_bit(NETLINK_CONGESTED, &nlk_sk(sk)->state)) {

			sk->sk_err = ENOBUFS;

			sk->sk_error_report(sk);

		}

	}

	atomic_inc(&sk->sk_drops);

}



static void netlink_rcv_wake(struct sock *sk)

{

	struct netlink_sock *nlk = nlk_sk(sk);



	if (skb_queue_empty(&sk->sk_receive_queue))

		clear_bit(NETLINK_CONGESTED, &nlk->state);

	if (!test_bit(NETLINK_CONGESTED, &nlk->state))

		wake_up_interruptible(&nlk->wait);

}



#ifdef CONFIG_NETLINK_MMAP

static bool netlink_skb_is_mmaped(const struct sk_buff *skb)

{
@@ -441,15 +465,48 @@ static void netlink_forward_ring(struct netlink_ring *ring) 
	} while (ring->head != head);

}



static bool netlink_dump_space(struct netlink_sock *nlk)

{

	struct netlink_ring *ring = &nlk->rx_ring;

	struct nl_mmap_hdr *hdr;

	unsigned int n;



	hdr = netlink_current_frame(ring, NL_MMAP_STATUS_UNUSED);

	if (hdr == NULL)

		return false;



	n = ring->head + ring->frame_max / 2;

	if (n > ring->frame_max)

		n -= ring->frame_max;



	hdr = __netlink_lookup_frame(ring, n);



	return hdr->nm_status == NL_MMAP_STATUS_UNUSED;

}



static unsigned int netlink_poll(struct file *file, struct socket *sock,

				 poll_table *wait)

{

	struct sock *sk = sock->sk;

	struct netlink_sock *nlk = nlk_sk(sk);

	unsigned int mask;

	int err;



	if (nlk->cb != NULL && nlk->rx_ring.pg_vec != NULL)

		netlink_dump(sk);

	if (nlk->rx_ring.pg_vec != NULL) {

		/* Memory mapped sockets don't call recvmsg(), so flow control

		 * for dumps is performed here. A dump is allowed to continue

		 * if at least half the ring is unused.

		 */

		while (nlk->cb != NULL && netlink_dump_space(nlk)) {

			err = netlink_dump(sk);

			if (err < 0) {

				sk->sk_err = err;

				sk->sk_error_report(sk);

				break;

			}

		}

		netlink_rcv_wake(sk);

	}



	mask = datagram_poll(file, sock, wait);
@@ -623,8 +680,7 @@ static void netlink_ring_set_copied(struct sock *sk, struct sk_buff *skb) 
	if (hdr == NULL) {

		spin_unlock_bh(&sk->sk_receive_queue.lock);

		kfree_skb(skb);

		sk->sk_err = ENOBUFS;

		sk->sk_error_report(sk);

		netlink_overrun(sk);

		return;

	}

	netlink_increment_head(ring);
@@ -1329,19 +1385,6 @@ static int netlink_getname(struct socket *sock, struct sockaddr *addr, 
	return 0;

}



static void netlink_overrun(struct sock *sk)

{

	struct netlink_sock *nlk = nlk_sk(sk);



	if (!(nlk->flags & NETLINK_RECV_NO_ENOBUFS)) {

		if (!test_and_set_bit(NETLINK_CONGESTED, &nlk_sk(sk)->state)) {

			sk->sk_err = ENOBUFS;

			sk->sk_error_report(sk);

		}

	}

	atomic_inc(&sk->sk_drops);

}



static struct sock *netlink_getsockbyportid(struct sock *ssk, u32 portid)

{

	struct sock *sock;
@@ -1484,16 +1527,6 @@ static struct sk_buff *netlink_trim(struct sk_buff *skb, gfp_t allocation) 
	return skb;

}



static void netlink_rcv_wake(struct sock *sk)

{

	struct netlink_sock *nlk = nlk_sk(sk);



	if (skb_queue_empty(&sk->sk_receive_queue))

		clear_bit(NETLINK_CONGESTED, &nlk->state);

	if (!test_bit(NETLINK_CONGESTED, &nlk->state))

		wake_up_interruptible(&nlk->wait);

}



static int netlink_unicast_kernel(struct sock *sk, struct sk_buff *skb,

				  struct sock *ssk)

{
@@ -1597,6 +1630,7 @@ struct sk_buff *netlink_alloc_skb(struct sock *ssk, unsigned int size, 
err2:

	kfree_skb(skb);

	spin_unlock_bh(&sk->sk_receive_queue.lock);

	netlink_overrun(sk);

err1:

	sock_put(sk);

	return NULL;