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Commit 8e8e2951 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

net/packet: make tp_drops atomic 



Under DDOS, we want to be able to increment tp_drops without
touching the spinlock. This will help readers to drain
the receive queue slightly faster :/

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 0338a145

net/packet/af_packet.c

+11 −9
Original line number Diff line number Diff line
@@ -758,7 +758,7 @@ static void prb_close_block(struct tpacket_kbdq_core *pkc1, 
	struct tpacket_hdr_v1 *h1 = &pbd1->hdr.bh1;

	struct sock *sk = &po->sk;



	if (po->stats.stats3.tp_drops)

	if (atomic_read(&po->tp_drops))

		status |= TP_STATUS_LOSING;



	last_pkt = (struct tpacket3_hdr *)pkc1->prev;
@@ -2128,10 +2128,8 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev, 


drop_n_acct:

	is_drop_n_account = true;

	spin_lock(&sk->sk_receive_queue.lock);

	po->stats.stats1.tp_drops++;

	atomic_inc(&po->tp_drops);

	atomic_inc(&sk->sk_drops);

	spin_unlock(&sk->sk_receive_queue.lock);



drop_n_restore:

	if (skb_head != skb->data && skb_shared(skb)) {
@@ -2265,7 +2263,7 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev, 
	 * Anyways, moving it for V1/V2 only as V3 doesn't need this

	 * at packet level.

	 */

		if (po->stats.stats1.tp_drops)

		if (atomic_read(&po->tp_drops))

			status |= TP_STATUS_LOSING;

	}
@@ -2381,9 +2379,9 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev, 
	return 0;



drop_n_account:

	is_drop_n_account = true;

	po->stats.stats1.tp_drops++;

	spin_unlock(&sk->sk_receive_queue.lock);

	atomic_inc(&po->tp_drops);

	is_drop_n_account = true;



	sk->sk_data_ready(sk);

	kfree_skb(copy_skb);
@@ -3879,6 +3877,7 @@ static int packet_getsockopt(struct socket *sock, int level, int optname, 
	void *data = &val;

	union tpacket_stats_u st;

	struct tpacket_rollover_stats rstats;

	int drops;



	if (level != SOL_PACKET)

		return -ENOPROTOOPT;
@@ -3895,14 +3894,17 @@ static int packet_getsockopt(struct socket *sock, int level, int optname, 
		memcpy(&st, &po->stats, sizeof(st));

		memset(&po->stats, 0, sizeof(po->stats));

		spin_unlock_bh(&sk->sk_receive_queue.lock);

		drops = atomic_xchg(&po->tp_drops, 0);



		if (po->tp_version == TPACKET_V3) {

			lv = sizeof(struct tpacket_stats_v3);

			st.stats3.tp_packets += st.stats3.tp_drops;

			st.stats3.tp_drops = drops;

			st.stats3.tp_packets += drops;

			data = &st.stats3;

		} else {

			lv = sizeof(struct tpacket_stats);

			st.stats1.tp_packets += st.stats1.tp_drops;

			st.stats1.tp_drops = drops;

			st.stats1.tp_packets += drops;

			data = &st.stats1;

		}

net/packet/internal.h

+1 −0
Original line number Diff line number Diff line
@@ -131,6 +131,7 @@ struct packet_sock { 
	struct net_device __rcu	*cached_dev;

	int			(*xmit)(struct sk_buff *skb);

	struct packet_type	prot_hook ____cacheline_aligned_in_smp;

	atomic_t		tp_drops ____cacheline_aligned_in_smp;

};



static struct packet_sock *pkt_sk(struct sock *sk)