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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: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2019-06-12 09:52:30 -07:00 committed by David S. Miller
parent 0338a14523
commit 8e8e2951e3
2 changed files with 12 additions and 9 deletions
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20
net/packet/af_packet.c
View File

@ -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 @@ drop:
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;
}

1
net/packet/internal.h
View File

@ -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)