Skip to contentSkip to conversation

net: make dev_xdp_sb_prog_count() see programs attached through a link

PATCH Applied Jakub Kicinski 3 participants 3 messages Oct 1 – Oct 5

Subsystems (3)
Networking Network drivers BPF
lore
Share & tools
lore

Jakub Kicinski

author maintainer
#0 lore raw

PATCH 1/1 net: make dev_xdp_sb_prog_count() see programs attached through a link

ethtool refuses to enable tcp-data-split on a device running a single-buffer XDP program (which can't deal with the payload landing in a separate buffer). dev_xdp_sb_prog_count() only looks at xdp_state[].prog though, ignoring bpf_link integration. Get the prog pointer from dev_xdp_prog(), which will consult both.

bpf_xdp_link_update() needs a bit of a touch-up, too, since ethtool calls dev_xdp_sb_prog_count() with just the instance lock (for ops-locked devices) - we now have to make sure the link updates happen under that lock.

Spotted by AI while reviewing the XDP propagation series, verified and tested on netdevsim with a C test along these lines:

  link = bpf_program__attach_xdp(prog, ifindex);
  system("ethtool -G eth0 tcp-data-split on")
Fixes 197258f0ef68 ("net: ethtool: add hds_config member in ethtool_netdev_state")
Signed-off-by Jakub Kicinski <[email protected]>

---
CC: [email protected]
CC: [email protected]
CC: [email protected]
CC: [email protected]
CC: [email protected]
CC: [email protected]

---
 net/core/dev.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)
net/core/dev.c +7 -4
index 79be99b52f20..030c444aee45 100644
@@ -10367,13 +10367,15 @@ EXPORT_SYMBOL_GPL(dev_xdp_prog_count);
 
 u8 dev_xdp_sb_prog_count(struct net_device *dev)
 {
+	struct bpf_prog *prog;
 	u8 count = 0;
 	int i;
 
-	for (i = 0; i < __MAX_XDP_MODE; i++)
-		if (dev->xdp_state[i].prog &&
-		    !dev->xdp_state[i].prog->aux->xdp_has_frags)
+	for (i = 0; i < __MAX_XDP_MODE; i++) {
+		prog = dev_xdp_prog(dev, i);
+		if (prog && !prog->aux->xdp_has_frags)
 			count++;
+	}
 	return count;
 }
 

@@ -10753,11 +10755,12 @@ static int bpf_xdp_link_update(struct bpf_link *link, struct bpf_prog *new_prog,
 	bpf_op = dev_xdp_bpf_op(xdp_link->dev, mode);
 	err = dev_xdp_install(xdp_link->dev, mode, bpf_op, NULL,
 			      xdp_link->flags, new_prog);
+	if (!err)
+		old_prog = xchg(&link->prog, new_prog);
 	netdev_unlock_ops(xdp_link->dev);
 	if (err)
 		goto out_unlock;
 
-	old_prog = xchg(&link->prog, new_prog);
 	bpf_prog_put(old_prog);
 
 out_unlock:
Signature · 1 line
2.55.0
Acked-by on v1 1/1
#1 lore raw
Quoted 11 lines · Jakub Kicinski

ethtool refuses to enable tcp-data-split on a device running a single-buffer XDP program (which can't deal with the payload landing in a separate buffer). dev_xdp_sb_prog_count() only looks at xdp_state[].prog though, ignoring bpf_link integration. Get the prog pointer from dev_xdp_prog(), which will consult both.

bpf_xdp_link_update() needs a bit of a touch-up, too, since ethtool calls dev_xdp_sb_prog_count() with just the instance lock (for ops-locked devices) - we now have to make sure the link updates happen under that lock.

Quoted 8 lines

Spotted by AI while reviewing the XDP propagation series, verified and tested on netdevsim with a C test along these lines:

  link = bpf_program__attach_xdp(prog, ifindex);
  system("ethtool -G eth0 tcp-data-split on")
Fixes 197258f0ef68 ("net: ethtool: add hds_config member in ethtool_netdev_state")
Signed-off-by Jakub Kicinski <[email protected]>
Acked-by Stanislav Fomichev <[email protected]>
CI Applied
#2 lore raw
In reply to Jakub Kicinski
This patch was applied to netdev/net.git (main) by Jakub Kicinski <[email protected]>:

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <[email protected]>:

Quoted 6 lines · On Wed, 30 Sep 2026 18:25:59 -0700 you wrote:

ethtool refuses to enable tcp-data-split on a device running a single-buffer XDP program (which can't deal with the payload landing in a separate buffer). dev_xdp_sb_prog_count() only looks at xdp_state[].prog though, ignoring bpf_link integration. Get the prog pointer from dev_xdp_prog(), which will consult both.

Quoted 6 lines

bpf_xdp_link_update() needs a bit of a touch-up, too, since ethtool calls dev_xdp_sb_prog_count() with just the instance lock (for ops-locked devices) - we now have to make sure the link updates happen under that lock.

[...]

Here is the summary with links:
- [net] net: make dev_xdp_sb_prog_count() see programs attached through a link

    https://git.kernel.org/netdev/net/c/d333c8bca6dc

You are awesome, thank you!

Signature · 2 lines
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html