Re: [PATCH v3 net-next 2/2] udp_tunnel: use static call for GRO hooks when possible

[Kuniyuki Iwashima <kuniyu@amazon.com>]

From: Paolo Abeni <pabeni@redhat.com>
Date: Mon, 10 Mar 2025 20:09:49 +0100
> diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
> index 054d4d4a8927f..500b2a20053cd 100644
> --- a/net/ipv4/udp_offload.c
> +++ b/net/ipv4/udp_offload.c
> @@ -15,6 +15,39 @@
>  #include <net/udp_tunnel.h>
>  
>  #if IS_ENABLED(CONFIG_NET_UDP_TUNNEL)
> +
> +/*
> + * Dummy GRO tunnel callback; should never be invoked, exists
> + * mainly to avoid dangling/NULL values for the udp tunnel
> + * static call.
> + */
> +static struct sk_buff *dummy_gro_rcv(struct sock *sk,
> +				     struct list_head *head,
> +				     struct sk_buff *skb)
> +{
> +	WARN_ON_ONCE(1);
> +	NAPI_GRO_CB(skb)->flush = 1;
> +	return NULL;
> +}
> +
> +typedef struct sk_buff *(*udp_tunnel_gro_rcv_t)(struct sock *sk,
> +						struct list_head *head,
> +						struct sk_buff *skb);
> +
> +struct udp_tunnel_type_entry {
> +	udp_tunnel_gro_rcv_t gro_receive;
> +	refcount_t count;
> +};
> +
> +#define UDP_MAX_TUNNEL_TYPES (IS_ENABLED(CONFIG_GENEVE) + \
> +			      IS_ENABLED(CONFIG_VXLAN) * 2 + \
> +			      IS_ENABLED(CONFIG_FOE) * 2)

I guess this is CONFIG_NET_FOU ?