Re: [PATCH bpf-next v5 2/8] net: Update an existing TCP congestion control algorithm.

[Martin KaFai Lau <martin.lau@linux.dev>]

On 3/7/23 4:50 PM, Kui-Feng Lee wrote:
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 50cfc2388cbc..00b6e1a2edaf 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -1512,6 +1512,8 @@ struct bpf_struct_ops {
>   			   void *kdata, const void *udata);
>   	int (*reg)(void *kdata);
>   	void (*unreg)(void *kdata);
> +	int (*update)(void *kdata, void *old_kdata);
> +	int (*validate)(void *kdata);
>   	const struct btf_type *type;
>   	const struct btf_type *value_type;
>   	const char *name;
> diff --git a/include/net/tcp.h b/include/net/tcp.h
> index db9f828e9d1e..2abb755e6a3a 100644
> --- a/include/net/tcp.h
> +++ b/include/net/tcp.h
> @@ -1117,6 +1117,9 @@ struct tcp_congestion_ops {
>   
>   int tcp_register_congestion_control(struct tcp_congestion_ops *type);
>   void tcp_unregister_congestion_control(struct tcp_congestion_ops *type);
> +int tcp_update_congestion_control(struct tcp_congestion_ops *type,
> +				  struct tcp_congestion_ops *old_type);
> +int tcp_validate_congestion_control(struct tcp_congestion_ops *ca);
>   
>   void tcp_assign_congestion_control(struct sock *sk);
>   void tcp_init_congestion_control(struct sock *sk);
> diff --git a/net/bpf/bpf_dummy_struct_ops.c b/net/bpf/bpf_dummy_struct_ops.c
> index ff4f89a2b02a..158f14e240d0 100644
> --- a/net/bpf/bpf_dummy_struct_ops.c
> +++ b/net/bpf/bpf_dummy_struct_ops.c
> @@ -222,12 +222,18 @@ static void bpf_dummy_unreg(void *kdata)
>   {
>   }
>   
> +static int bpf_dummy_update(void *kdata, void *old_kdata)
> +{
> +	return -EOPNOTSUPP;
> +}
> +
>   struct bpf_struct_ops bpf_bpf_dummy_ops = {
>   	.verifier_ops = &bpf_dummy_verifier_ops,
>   	.init = bpf_dummy_init,
>   	.check_member = bpf_dummy_ops_check_member,
>   	.init_member = bpf_dummy_init_member,
>   	.reg = bpf_dummy_reg,
> +	.update = bpf_dummy_update,
>   	.unreg = bpf_dummy_unreg,
>   	.name = "bpf_dummy_ops",
>   };
> diff --git a/net/ipv4/bpf_tcp_ca.c b/net/ipv4/bpf_tcp_ca.c
> index 13fc0c185cd9..e8b27826283e 100644
> --- a/net/ipv4/bpf_tcp_ca.c
> +++ b/net/ipv4/bpf_tcp_ca.c
> @@ -239,8 +239,6 @@ static int bpf_tcp_ca_init_member(const struct btf_type *t,
>   		if (bpf_obj_name_cpy(tcp_ca->name, utcp_ca->name,
>   				     sizeof(tcp_ca->name)) <= 0)
>   			return -EINVAL;
> -		if (tcp_ca_find(utcp_ca->name))
> -			return -EEXIST;

This belongs to patch 3 where BPF_F_LINK needs this. move it closer to where it 
is actually used.

>   		return 1;
>   	}
>   
> @@ -266,13 +264,25 @@ static void bpf_tcp_ca_unreg(void *kdata)
>   	tcp_unregister_congestion_control(kdata);
>   }
>   
> +static int bpf_tcp_ca_update(void *kdata, void *old_kdata)
> +{
> +	return tcp_update_congestion_control(kdata, old_kdata);
> +}
> +
> +static int bpf_tcp_ca_validate(void *kdata)
> +{
> +	return tcp_validate_congestion_control(kdata);
> +}
> +
>   struct bpf_struct_ops bpf_tcp_congestion_ops = {
>   	.verifier_ops = &bpf_tcp_ca_verifier_ops,
>   	.reg = bpf_tcp_ca_reg,
>   	.unreg = bpf_tcp_ca_unreg,
> +	.update = bpf_tcp_ca_update,
>   	.check_member = bpf_tcp_ca_check_member,
>   	.init_member = bpf_tcp_ca_init_member,
>   	.init = bpf_tcp_ca_init,
> +	.validate = bpf_tcp_ca_validate,
>   	.name = "tcp_congestion_ops",
>   };

In general, please move "validate" related bpf changes to patch 3 and "update" 
related changes to patch 5. They are bpf specific (including the changes in 
bpf_tcp_ca.c) and closer to where it will be used.

Then patch 2 should only have changes in tcp_cong.c as the preparation work for 
the later bpf needs. Please cc netdev for patch 2 in the next re-spin.