linux-kernel - Re: [PATCH v2 06/25] tcp: authopt: Compute packet signatures

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Date:   Fri, 5 Nov 2021 02:08:40 +0000
From:   Dmitry Safonov <0x7f454c46@...il.com>
To:     Leonard Crestez <cdleonard@...il.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Kuniyuki Iwashima <kuniyu@...zon.co.jp>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Yuchung Cheng <ycheng@...gle.com>,
        Francesco Ruggeri <fruggeri@...sta.com>,
        Mat Martineau <mathew.j.martineau@...ux.intel.com>,
        Christoph Paasch <cpaasch@...le.com>,
        Ivan Delalande <colona@...sta.com>,
        Priyaranjan Jha <priyarjha@...gle.com>, netdev@...r.kernel.org,
        linux-crypto@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org, Shuah Khan <shuah@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        David Ahern <dsahern@...nel.org>
Subject: Re: [PATCH v2 06/25] tcp: authopt: Compute packet signatures

On 11/1/21 16:34, Leonard Crestez wrote:
[..]
> +/* Find TCP_AUTHOPT in header.
> + *
> + * Returns pointer to TCP_AUTHOPT or NULL if not found.
> + */
> +static u8 *tcp_authopt_find_option(struct tcphdr *th)
> +{
> +	int length = (th->doff << 2) - sizeof(*th);
> +	u8 *ptr = (u8 *)(th + 1);
> +
> +	while (length >= 2) {
> +		int opcode = *ptr++;
> +		int opsize;
> +
> +		switch (opcode) {
> +		case TCPOPT_EOL:
> +			return NULL;
> +		case TCPOPT_NOP:
> +			length--;
> +			continue;
> +		default:
> +			if (length < 2)
> +				return NULL;

^ never true, as checked by the loop condition

> +			opsize = *ptr++;
> +			if (opsize < 2)
> +				return NULL;
> +			if (opsize > length)
> +				return NULL;
> +			if (opcode == TCPOPT_AUTHOPT)
> +				return ptr - 2;
> +		}
> +		ptr += opsize - 2;
> +		length -= opsize;
> +	}
> +	return NULL;
> +}

Why copy'n'pasting tcp_parse_md5sig_option(), rather than adding a new
argument to the function?

Thanks,
            Dmitry