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net/packet: implement shortcut in tpacket_rcv()

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tpacket_rcv() can be hit under DDOS quite hard, since
it will always grab a socket spinlock, to eventually find
there is no room for an additional packet.

Using tcpdump [1] on a busy host can lead to catastrophic consequences,
because of all cpus spinning on a contended spinlock.

This replicates a similar strategy used in packet_rcv()

[1] Also some applications mistakenly use af_packet socket
bound to ETH_P_ALL only to send packets.
Receive queue is never drained and immediately full.

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 09:52:31 -07:00 committed by David S. Miller
parent 8e8e2951e3
commit 2c51c6273c
1 changed files with 6 additions and 0 deletions
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6
net/packet/af_packet.c
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@ -2193,6 +2193,12 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
if (!res)
goto drop_n_restore;
/* If we are flooded, just give up */
if (__packet_rcv_has_room(po, skb) == ROOM_NONE) {
atomic_inc(&po->tp_drops);
goto drop_n_restore;
}
if (skb->ip_summed == CHECKSUM_PARTIAL)
status |= TP_STATUS_CSUMNOTREADY;
else if (skb->pkt_type != PACKET_OUTGOING &&