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.whitchu...@axis.com>
---
include/linux/netdevice.h | 1 +
include/uapi/linux/if_packet.h | 1 +
net/core/dev.c | 3 +++
net/packet/af_packet.c | 15 +++++++++++++++
4 files changed, 20 insertions(+)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index ca5ab98053c8..8ef14d9edc58 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2317,6 +2317,7 @@ static inline struct sk_buff
*call_gro_receive_sk(gro_receive_sk_t cb,
struct packet_type {
__be16 type; /* This is really htons(ether_type). */
+ bool ignore_outgoing;
struct net_device *dev; /* NULL is wildcarded here */
int (*func) (struct sk_buff *,
struct net_device *,
diff --git a/include/uapi/linux/if_packet.h b/include/uapi/linux/if_packet.h
index 67b61d91d89b..467b654bd4c7 100644
--- a/include/uapi/linux/if_packet.h
+++ b/include/uapi/linux/if_packet.h
@@ -57,6 +57,7 @@ struct sockaddr_ll {
#define PACKET_QDISC_BYPASS 20
#define PACKET_ROLLOVER_STATS 21
#define PACKET_FANOUT_DATA 22
+#define PACKET_IGNORE_OUTGOING 23
#define PACKET_FANOUT_HASH 0
#define PACKET_FANOUT_LB 1
diff --git a/net/core/dev.c b/net/core/dev.c
index 325fc5088370..0addb4f0abfe 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1947,6 +1947,9 @@ static inline bool skb_loop_sk(struct packet_type *ptype,
struct sk_buff *skb)
if (!ptype->af_packet_priv || !skb->sk)
return false;
+ if (ptype->ignore_outgoing)
+ return true;
+
if (ptype->id_match)
return ptype->id_match(ptype, skb->sk);
else if ((struct sock *)ptype->af_packet_priv == skb->sk)
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 5610061e7f2e..37bbafad724a 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -3805,6 +3805,18 @@ 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;
+
+ po->prot_hook.ignore_outgoing = !!val;
+ return 0;
+ }
case PACKET_TX_HAS_OFF:
{
unsigned int val;
@@ -3928,6 +3940,9 @@ 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;
--
2.11.0
