linux-kernel - Re: [PATCH bpf-next v2] net: Don't allow to attach xdp if bond slave device's upper already has a program

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Message-ID: <Zsh4vPAPBKdRUq8H@nanopsycho.orion>
Date: Fri, 23 Aug 2024 13:55:40 +0200
From: Jiri Pirko <jiri@...nulli.us>
To: Feng zhou <zhoufeng.zf@...edance.com>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
	pabeni@...hat.com, ast@...nel.org, daniel@...earbox.net,
	hawk@...nel.org, john.fastabend@...il.com, bigeasy@...utronix.de,
	lorenzo@...nel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, bpf@...r.kernel.org,
	yangzhenze@...edance.com, wangdongdong.6@...edance.com,
	Toke Høiland-Jørgensen <toke@...hat.com>
Subject: Re: [PATCH bpf-next v2] net: Don't allow to attach xdp if bond slave
 device's upper already has a program

Fri, Aug 23, 2024 at 10:42:04AM CEST, zhoufeng.zf@...edance.com wrote:
>From: Feng Zhou <zhoufeng.zf@...edance.com>
>
>Cannot attach when an upper device already has a program, This
>restriction is only for bond's slave devices or team port, and
>should not be accidentally injured for devices like eth0 and vxlan0.

What if I attach xdp program to solo netdev and then I enslave it
to bond/team netdev that already has xdp program attached?
What prevents me from doing that?


>
>Reviewed-by: Toke Høiland-Jørgensen <toke@...hat.com>
>Signed-off-by: Feng Zhou <zhoufeng.zf@...edance.com>
>---
>Changelog:
>v1->v2: Addressed comments from Paolo Abeni, Jiri Pirko
>- Use "netif_is_lag_port" relace of "netif_is_bond_slave"
>Details in here:
>https://lore.kernel.org/netdev/3bf84d23-a561-47ae-84a4-e99488fc762b@bytedance.com/T/
>
> net/core/dev.c | 10 ++++++----
> 1 file changed, 6 insertions(+), 4 deletions(-)
>
>diff --git a/net/core/dev.c b/net/core/dev.c
>index f66e61407883..49144e62172e 100644
>--- a/net/core/dev.c
>+++ b/net/core/dev.c
>@@ -9502,10 +9502,12 @@ static int dev_xdp_attach(struct net_device *dev, struct netlink_ext_ack *extack
> 	}
> 
> 	/* don't allow if an upper device already has a program */
>-	netdev_for_each_upper_dev_rcu(dev, upper, iter) {
>-		if (dev_xdp_prog_count(upper) > 0) {
>-			NL_SET_ERR_MSG(extack, "Cannot attach when an upper device already has a program");
>-			return -EEXIST;
>+	if (netif_is_lag_port(dev)) {
>+		netdev_for_each_upper_dev_rcu(dev, upper, iter) {
>+			if (dev_xdp_prog_count(upper) > 0) {
>+				NL_SET_ERR_MSG(extack, "Cannot attach when an upper device already has a program");
>+				return -EEXIST;
>+			}
> 		}
> 	}
> 
>-- 
>2.30.2
>