[net-next] net/packet: add PACKET_FANOUT_FLAG_IGNORE_OUTGOING

Commit Message

Willem de Bruijn Oct. 27, 2022, 9:10 p.m. UTC

From: Willem de Bruijn <[e-mail]>

Extend packet socket option PACKET_IGNORE_OUTGOING to fanout groups.

The socket option sets ptype.ignore_outgoing, which makes
dev_queue_xmit_nit skip the socket.

When the socket joins a fanout group, the option is not reflected in
the struct ptype of the group. dev_queue_xmit_nit only tests the
fanout ptype, so the flag is ignored once a socket joins a
fanout group.

Inheriting the option from a socket would change established behavior.
Different sockets in the group can set different flags, and can also
change them at runtime.

Testing in packet_rcv_fanout defeats the purpose of the original
patch, which is to avoid skb_clone in dev_queue_xmit_nit (esp. for
MSG_ZEROCOPY packets).

Instead, introduce a new fanout group flag with the same behavior.

Tested with https://github.com/wdebruij/kerneltools/blob/master/tests/test_psock_fanout_ignore_outgoing.c

Signed-off-by: Willem de Bruijn <[e-mail]>
---
 include/uapi/linux/if_packet.h | 1 +
 net/packet/af_packet.c         | 1 +
 2 files changed, 2 insertions(+)

Comments

Eric Dumazet Oct. 28, 2022, 5:35 p.m. UTC | #1

On Thu, Oct 27, 2022 at 2:10 PM Willem de Bruijn
<[e-mail]> wrote:
>
> From: Willem de Bruijn <[e-mail]>
>
> Extend packet socket option PACKET_IGNORE_OUTGOING to fanout groups.
>
...
> Instead, introduce a new fanout group flag with the same behavior.
>
> Tested with https://github.com/wdebruij/kerneltools/blob/master/tests/test_psock_fanout_ignore_outgoing.c
>
> Signed-off-by: Willem de Bruijn <[e-mail]>

SGTM, thanks.

Reviewed-by: Eric Dumazet <[e-mail]>

[e-mail] Oct. 29, 2022, 6:30 a.m. UTC | #2

Hello:

This patch was applied to netdev/net-next.git (master)
by Jakub Kicinski <[e-mail]>:

On Thu, 27 Oct 2022 17:10:14 -0400 you wrote:
> From: Willem de Bruijn <[e-mail]>
> 
> Extend packet socket option PACKET_IGNORE_OUTGOING to fanout groups.
> 
> The socket option sets ptype.ignore_outgoing, which makes
> dev_queue_xmit_nit skip the socket.
> 
> [...]

Here is the summary with links:
  - [net-next] net/packet: add PACKET_FANOUT_FLAG_IGNORE_OUTGOING
    https://git.kernel.org/netdev/net-next/c/58ba426388d9

You are awesome, thank you!

Patch

diff --git a/include/uapi/linux/if_packet.h b/include/uapi/linux/if_packet.h
index c07caf7b40db6..a8516b3594a44 100644
--- a/include/uapi/linux/if_packet.h
+++ b/include/uapi/linux/if_packet.h
@@ -70,6 +70,7 @@  struct sockaddr_ll {
 #define PACKET_FANOUT_EBPF		7
 #define PACKET_FANOUT_FLAG_ROLLOVER	0x1000
 #define PACKET_FANOUT_FLAG_UNIQUEID	0x2000
+#define PACKET_FANOUT_FLAG_IGNORE_OUTGOING     0x4000
 #define PACKET_FANOUT_FLAG_DEFRAG	0x8000
 
 struct tpacket_stats {
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 8c5b3da0c29f6..44f20cf8a0c0e 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1777,6 +1777,7 @@  static int fanout_add(struct sock *sk, struct fanout_args *args)
 		match->prot_hook.af_packet_net = read_pnet(&match->net);
 		match->prot_hook.id_match = match_fanout_group;
 		match->max_num_members = args->max_num_members;
+		match->prot_hook.ignore_outgoing = type_flags & PACKET_FANOUT_FLAG_IGNORE_OUTGOING;
 		list_add(&match->list, &fanout_list);
 	}
 	err = -EINVAL;