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Date:   Mon, 6 Mar 2023 18:17:32 -0800
MIME-Version: 1.0
Subject: Re: [PATCH bpf-next v3 3/8] net: Update an existing TCP congestion
 control algorithm.
Content-Language: en-US
To:     Kui-Feng Lee <kuifeng@meta.com>
References: <20230303012122.852654-1-kuifeng@meta.com>
 <20230303012122.852654-4-kuifeng@meta.com>
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From:   Martin KaFai Lau <martin.lau@linux.dev>
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On 3/2/23 5:21 PM, Kui-Feng Lee wrote:
> diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
> index db8b4b488c31..981501871609 100644
> --- a/net/ipv4/tcp_cong.c
> +++ b/net/ipv4/tcp_cong.c
> @@ -75,14 +75,8 @@ struct tcp_congestion_ops *tcp_ca_find_key(u32 key)
>   	return NULL;
>   }
>   
> -/*
> - * Attach new congestion control algorithm to the list
> - * of available options.
> - */
> -int tcp_register_congestion_control(struct tcp_congestion_ops *ca)
> +static int tcp_ca_validate(struct tcp_congestion_ops *ca)

It is useful to call tcp_ca_validate() before update_elem transiting a 
struct_ops to BPF_STRUCT_OPS_STATE_READY. Otherwise, the user space will end up 
having a struct_ops that can never be used to create a link.