netdev - Re: [PATCH net 1/2] ipv6: create multicast route with RTPROT

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Date:   Fri, 15 Jan 2021 21:36:51 -0700
From:   David Ahern <dsahern@...il.com>
To:     Matteo Croce <mcroce@...ux.microsoft.com>, netdev@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Jakub Kicinski <kuba@...nel.org>
Subject: Re: [PATCH net 1/2] ipv6: create multicast route with RTPROT_KERNEL

On 1/15/21 11:42 AM, Matteo Croce wrote:
> From: Matteo Croce <mcroce@...rosoft.com>
> 
> The ff00::/8 multicast route is created without specifying the fc_protocol
> field, so the default RTPROT_BOOT value is used:
> 
>   $ ip -6 -d route
>   unicast ::1 dev lo proto kernel scope global metric 256 pref medium
>   unicast fe80::/64 dev eth0 proto kernel scope global metric 256 pref medium
>   unicast ff00::/8 dev eth0 proto boot scope global metric 256 pref medium
> 
> As the documentation says, this value identifies routes installed during
> boot, but the route is created when interface is set up.
> Change the value to RTPROT_KERNEL which is a better value.
> 
> Signed-off-by: Matteo Croce <mcroce@...rosoft.com>
> ---
>  net/ipv6/addrconf.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
> index eff2cacd5209..19bf6822911c 100644
> --- a/net/ipv6/addrconf.c
> +++ b/net/ipv6/addrconf.c
> @@ -2469,6 +2469,7 @@ static void addrconf_add_mroute(struct net_device *dev)
>  		.fc_flags = RTF_UP,
>  		.fc_type = RTN_UNICAST,
>  		.fc_nlinfo.nl_net = dev_net(dev),
> +		.fc_protocol = RTPROT_KERNEL,
>  	};
>  
>  	ipv6_addr_set(&cfg.fc_dst, htonl(0xFF000000), 0, 0, 0);
> 


What's the motivation for changing this? ie., what s/w cares that it is
kernel vs boot?