linux-kernel - Re: [PATCH bpf v8 3/5] bpf: disable non stream socket for strparser

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Message-ID: <87wmeogsaj.fsf@cloudflare.com>
Date: Tue, 21 Jan 2025 15:23:00 +0100
From: Jakub Sitnicki <jakub@...udflare.com>
To: Jiayuan Chen <mrpre@....com>
Cc: bpf@...r.kernel.org,  john.fastabend@...il.com,  netdev@...r.kernel.org,
  martin.lau@...ux.dev,  ast@...nel.org,  edumazet@...gle.com,
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Subject: Re: [PATCH bpf v8 3/5] bpf: disable non stream socket for strparser

On Tue, Jan 21, 2025 at 01:07 PM +08, Jiayuan Chen wrote:
> Currently, only TCP supports strparser, but sockmap doesn't intercept
> non-TCP to attach strparser. For example, with UDP, although the
> read/write handlers are replaced, strparser is not executed due to the
> lack of read_sock operation.
>
> Furthermore, in udp_bpf_recvmsg(), it checks whether psock has data, and
> if not, it falls back to the native UDP read interface, making
> UDP + strparser appear to read correctly. According to it's commit

Nit: typo, "its"

> history, the behavior is unexpected.
>
> Moreover, since UDP lacks the concept of streams, we intercept it
> directly.
>
> Signed-off-by: Jiayuan Chen <mrpre@....com>
> ---
>  net/core/sock_map.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/net/core/sock_map.c b/net/core/sock_map.c
> index f1b9b3958792..3b0f59d9b4db 100644
> --- a/net/core/sock_map.c
> +++ b/net/core/sock_map.c
> @@ -303,7 +303,10 @@ static int sock_map_link(struct bpf_map *map, struct sock *sk)
>  
>  	write_lock_bh(&sk->sk_callback_lock);
>  	if (stream_parser && stream_verdict && !psock->saved_data_ready) {
> -		ret = sk_psock_init_strp(sk, psock);
> +		if (sk_is_tcp(sk))
> +			ret = sk_psock_init_strp(sk, psock);
> +		else
> +			ret = -EOPNOTSUPP;
>  		if (ret) {
>  			write_unlock_bh(&sk->sk_callback_lock);
>  			sk_psock_put(sk, psock);

Reviewed-by: Jakub Sitnicki <jakub@...udflare.com>