netdev - Re: [PATCH net] ipv6: set all.accept

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Date:   Mon, 13 Nov 2017 14:21:52 +0000
From:   Erik Kline <ek@...gle.com>
To:     Nicolas Dichtel <nicolas.dichtel@...nd.com>
Cc:     David Miller <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Stefano Brivio <sbrivio@...hat.com>,
        Matteo Croce <mcroce@...hat.com>,
        Maciej Żenczykowski <maze@...gle.com>
Subject: Re: [PATCH net] ipv6: set all.accept_dad to 0 by default

Should we consider rolling back the patch that caused this?
"accept_dad = 1" is the proper IETF-expected default behaviour.

Alternatively, if we really want to make all, default, and ifname
useful perhaps we need to investigate a tristate option (for currently
boolean values, at least).  -1 could mean no preference, for example.

On 13 November 2017 at 13:45, Nicolas Dichtel <nicolas.dichtel@...nd.com> wrote:
> The commit a2d3f3e33853 modifies the way to disable dad on an interface.
> Before the patch, setting <iface>.accept_dad to 0 was enough to disable it.
> Because all.accept_dad is set to 1 by default, after the patch, the user
> needs to set both all.accept_dad and <iface>.accept_dad to 0 to disable it.
>
> This is not backward compatible. When a user updates its kernel, the dad
> may be enabled by error.
>
> Let's set all.accept_dad to 0 by default to restore the previous behavior.
>
> Fixes: a2d3f3e33853 ("ipv6: fix net.ipv6.conf.all.accept_dad behaviour for real")
> CC: Stefano Brivio <sbrivio@...hat.com>
> CC: Matteo Croce <mcroce@...hat.com>
> CC: Erik Kline <ek@...gle.com>
> Signed-off-by: Nicolas Dichtel <nicolas.dichtel@...nd.com>
> ---
>  net/ipv6/addrconf.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
> index 8a1c846d3df9..ef5b61507b9a 100644
> --- a/net/ipv6/addrconf.c
> +++ b/net/ipv6/addrconf.c
> @@ -231,7 +231,7 @@ static struct ipv6_devconf ipv6_devconf __read_mostly = {
>         .proxy_ndp              = 0,
>         .accept_source_route    = 0,    /* we do not accept RH0 by default. */
>         .disable_ipv6           = 0,
> -       .accept_dad             = 1,
> +       .accept_dad             = 0,
>         .suppress_frag_ndisc    = 1,
>         .accept_ra_mtu          = 1,
>         .stable_secret          = {
> --
> 2.13.2
>

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