packet: add sockopt to ignore outgoing packets
Currently, the only way to ignore outgoing packets on a packet socket is
via the BPF filter. With MSG_ZEROCOPY, packets that are looped into
AF_PACKET are copied in dev_queue_xmit_nit(), and this copy happens even
if the filter run from packet_rcv() would reject them. So the presence
of a packet socket on the interface takes away the benefits of
MSG_ZEROCOPY, even if the packet socket is not interested in outgoing
packets. (Even when MSG_ZEROCOPY is not used, the skb is unnecessarily
cloned, but the cost for that is much lower.)
Add a socket option to allow AF_PACKET sockets to ignore outgoing
packets to solve this. Note that the *BSDs already have something
similar: BIOCSSEESENT/BIOCSDIRECTION and BIOCSDIRFILT.
The first intended user is lldpd.
Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 75c92a8..f85f67b 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -3805,6 +3805,20 @@ packet_setsockopt(struct socket *sock, int level, int optname, char __user *optv
return fanout_set_data(po, optval, optlen);
}
+ case PACKET_IGNORE_OUTGOING:
+ {
+ int val;
+
+ if (optlen != sizeof(val))
+ return -EINVAL;
+ if (copy_from_user(&val, optval, sizeof(val)))
+ return -EFAULT;
+ if (val < 0 || val > 1)
+ return -EINVAL;
+
+ po->prot_hook.ignore_outgoing = !!val;
+ return 0;
+ }
case PACKET_TX_HAS_OFF:
{
unsigned int val;
@@ -3928,6 +3942,9 @@ static int packet_getsockopt(struct socket *sock, int level, int optname,
((u32)po->fanout->flags << 24)) :
0);
break;
+ case PACKET_IGNORE_OUTGOING:
+ val = po->prot_hook.ignore_outgoing;
+ break;
case PACKET_ROLLOVER_STATS:
if (!po->rollover)
return -EINVAL;