linux-kernel - Re: [PATCH v2 09/25] tcp: authopt: Disable via sysctl by default

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Message-ID: <019e96b5-4047-6458-0cfa-c9ef8f0d0470@gmail.com>
Date:   Tue, 2 Nov 2021 20:39:51 -0600
From:   David Ahern <dsahern@...il.com>
To:     Leonard Crestez <cdleonard@...il.com>,
        David Ahern <dsahern@...nel.org>,
        Shuah Khan <shuah@...nel.org>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Eric Dumazet <edumazet@...gle.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
Subject: Re: [PATCH v2 09/25] tcp: authopt: Disable via sysctl by default

On 11/1/21 10:34 AM, Leonard Crestez wrote:
> diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
> index 97eb54774924..cc34de6e4817 100644
> --- a/net/ipv4/sysctl_net_ipv4.c
> +++ b/net/ipv4/sysctl_net_ipv4.c
> @@ -17,10 +17,11 @@
>  #include <net/udp.h>
>  #include <net/cipso_ipv4.h>
>  #include <net/ping.h>
>  #include <net/protocol.h>
>  #include <net/netevent.h>
> +#include <net/tcp_authopt.h>
>  
>  static int two = 2;
>  static int three __maybe_unused = 3;
>  static int four = 4;
>  static int thousand = 1000;
> @@ -583,10 +584,19 @@ static struct ctl_table ipv4_table[] = {
>  		.mode		= 0644,
>  		.proc_handler	= proc_douintvec_minmax,
>  		.extra1		= &sysctl_fib_sync_mem_min,
>  		.extra2		= &sysctl_fib_sync_mem_max,
>  	},
> +#ifdef CONFIG_TCP_AUTHOPT
> +	{
> +		.procname	= "tcp_authopt",
> +		.data		= &sysctl_tcp_authopt,
> +		.maxlen		= sizeof(int),
> +		.mode		= 0644,
> +		.proc_handler	= proc_dointvec,

Just add it to the namespace set, and this could be a u8 (try to plug a
hole if possible) with min/max specified:

                .maxlen         = sizeof(u8),
                .mode           = 0644,
                .extra1         = SYSCTL_ZERO,
                .extra2         = SYSCTL_ONE


see icmp_echo_enable_probe as an example. And if you are not going to
clean up when toggled off, you need a handler that tells the user it can
not be disabled by erroring out on attempts to disable it.