Subject: Re: [PATCH bpf 4/6] bpf, netkit: Add indirect call wrapper for fetching peer dev

From: Stanislav Fomichev <[email-masked]>
Date: Mon, 6 Nov 2023 09:21:59 -0800

On 11/03, Daniel Borkmann wrote:
> ndo_get_peer_dev is used in tcx BPF fast path, therefore make use of
> indirect call wrapper and therefore optimize the bpf_redirect_peer()
> internal handling a bit. Add a small skb_get_peer_dev() wrapper which
> utilizes the INDIRECT_CALL_1() macro instead of open coding.
> 
> Co-developed-by: Nikolay Aleksandrov <[email-masked]>
> Signed-off-by: Nikolay Aleksandrov <[email-masked]>
> Signed-off-by: Daniel Borkmann <[email-masked]>
> ---
>  drivers/net/netkit.c |  3 ++-
>  include/net/netkit.h |  6 ++++++
>  net/core/filter.c    | 18 +++++++++++++-----
>  3 files changed, 21 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/net/netkit.c b/drivers/net/netkit.c
> index dc51c23b40f0..934c71a73b5c 100644
> --- a/drivers/net/netkit.c
> +++ b/drivers/net/netkit.c
> @@ -7,6 +7,7 @@
>  #include <linux/filter.h>
>  #include <linux/netfilter_netdev.h>
>  #include <linux/bpf_mprog.h>
> +#include <linux/indirect_call_wrapper.h>
>  
>  #include <net/netkit.h>
>  #include <net/dst.h>
> @@ -177,7 +178,7 @@ static void netkit_set_headroom(struct net_device *dev, int headroom)
>  	rcu_read_unlock();
>  }
>  
> -static struct net_device *netkit_peer_dev(struct net_device *dev)
> +INDIRECT_CALLABLE_SCOPE struct net_device *netkit_peer_dev(struct net_device *dev)
>  {
>  	return rcu_dereference(netkit_priv(dev)->peer);
>  }
> diff --git a/include/net/netkit.h b/include/net/netkit.h
> index 0ba2e6b847ca..9ec0163739f4 100644
> --- a/include/net/netkit.h
> +++ b/include/net/netkit.h
> @@ -10,6 +10,7 @@ int netkit_prog_attach(const union bpf_attr *attr, struct bpf_prog *prog);
>  int netkit_link_attach(const union bpf_attr *attr, struct bpf_prog *prog);
>  int netkit_prog_detach(const union bpf_attr *attr, struct bpf_prog *prog);
>  int netkit_prog_query(const union bpf_attr *attr, union bpf_attr __user *uattr);
> +INDIRECT_CALLABLE_DECLARE(struct net_device *netkit_peer_dev(struct net_device *dev));
>  #else
>  static inline int netkit_prog_attach(const union bpf_attr *attr,
>  				     struct bpf_prog *prog)
> @@ -34,5 +35,10 @@ static inline int netkit_prog_query(const union bpf_attr *attr,
>  {
>  	return -EINVAL;
>  }
> +
> +static inline struct net_device *netkit_peer_dev(struct net_device *dev)
> +{
> +	return NULL;
> +}
>  #endif /* CONFIG_NETKIT */
>  #endif /* __NET_NETKIT_H */
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 7aca28b7d0fd..dbf92b272022 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -81,6 +81,7 @@
>  #include <net/xdp.h>
>  #include <net/mptcp.h>
>  #include <net/netfilter/nf_conntrack_bpf.h>
> +#include <net/netkit.h>
>  #include <linux/un.h>
>  
>  #include "dev.h"
> @@ -2468,6 +2469,16 @@ static const struct bpf_func_proto bpf_clone_redirect_proto = {
>  DEFINE_PER_CPU(struct bpf_redirect_info, bpf_redirect_info);
>  EXPORT_PER_CPU_SYMBOL_GPL(bpf_redirect_info);
>  
> +static struct net_device *skb_get_peer_dev(struct net_device *dev)
> +{
> +	const struct net_device_ops *ops = dev->netdev_ops;
> +
> +	if (likely(ops->ndo_get_peer_dev))
> +		return INDIRECT_CALL_1(ops->ndo_get_peer_dev,
> +				       netkit_peer_dev, dev);

nit: why not put both netkit and veth here under INDIRECT_CALL_2 ?
Presumably should help with the veth deployments as well?