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References: <20230113-sockmap-fix-v1-1-d3cad092ee10@cloudflare.com>
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From:   Jakub Sitnicki <jakub@cloudflare.com>
To:     Eric Dumazet <edumazet@google.com>
Cc:     Dan Carpenter <error27@gmail.com>, oe-kbuild@lists.linux.dev,
        netdev@vger.kernel.org, lkp@intel.com,
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        John Fastabend <john.fastabend@gmail.com>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Alexei Starovoitov <ast@kernel.org>,
        Andrii Nakryiko <andrii@kernel.org>,
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Subject: Re: [PATCH bpf 1/3] bpf, sockmap: Check for any of tcp_bpf_prots
 when cloning a listener
Date:   Mon, 16 Jan 2023 12:27:10 +0100
In-reply-to: <CANn89iLanM-OJu8hThK__G_gQj0z39Rnj-5Fk=kQEmbhs2OPfA@mail.gmail.com>
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On Mon, Jan 16, 2023 at 11:39 AM +01, Eric Dumazet wrote:
> We might add a generic helper to make all this a bit more clear ?
>
> +#define is_insidevar(PTR, VAR) (                       \
> +       ((void *)(PTR) <= (void *)(VAR)) &&             \
> +       ((void *)(PTR) <= (void *)(VAR) + sizeof(VAR)))
> +
>
>
> ...
>
> if (is_insidevar(prot, tcp_bpf_prots))
>      newsk->sk_prot = sk->sk_prot_creator;

Sure can do. Thanks for the suggestion. I adjusted it a bit:
 - added cast to char * so we don't offend -Wpointer-arith,
 - fixed the lower and upper bound check.

Final form would look like:

#define is_insidevar(ptr, var)						\
	((void *)(ptr) >= (void *)(var)) &&				\
	((void *)(ptr) <  (void *)((char *)(var) + sizeof(var)))

Not sure where to stuff it. I propose include/linux/util_macros.h.