Re: [PATCH net v2 4/5] net/ipv6: propagate net.ipv6.conf.all.addr_gen_mode to devices

[David Ahern <dsahern@gmail.com>]

On 7/9/18 4:25 AM, Sabrina Dubroca wrote:
> This aligns the addr_gen_mode sysctl with the expected behavior of the
> "all" variant.
> 
> Fixes: d35a00b8e33d ("net/ipv6: allow sysctl to change link-local address generation mode")
> Suggested-by: David Ahern <dsahern@gmail.com>
> Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
> ---
>  net/ipv6/addrconf.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
> index e89bca83e0e4..1659a6b3cf42 100644
> --- a/net/ipv6/addrconf.c
> +++ b/net/ipv6/addrconf.c
> @@ -5926,6 +5926,18 @@ static int addrconf_sysctl_addr_gen_mode(struct ctl_table *ctl, int write,
>  				idev->cnf.addr_gen_mode = new_val;
>  				addrconf_dev_config(idev->dev);
>  			}
> +		} else if (&net->ipv6.devconf_all->addr_gen_mode == ctl->data) {
> +			struct net_device *dev;
> +
> +			net->ipv6.devconf_dflt->addr_gen_mode = new_val;
> +			for_each_netdev(net, dev) {
> +				idev = __in6_dev_get(dev);
> +				if (idev &&
> +				    idev->cnf.addr_gen_mode != new_val) {
> +					idev->cnf.addr_gen_mode = new_val;
> +					addrconf_dev_config(idev->dev);

This call is adding a new LL address without removing the previous one:

# ip -6 addr sh dev eth2
4: eth2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 state UP qlen 1000
    inet6 2001:db8:2::4/64 scope global
       valid_lft forever preferred_lft forever
    inet6 fe80::e0:f9ff:fe45:6480/64 scope link
       valid_lft forever preferred_lft forever

# sysctl -w net.ipv6.conf.eth2.addr_gen_mode=3
net.ipv6.conf.eth2.addr_gen_mode = 3

# ip -6 addr sh dev eth2
4: eth2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 state UP qlen 1000
    inet6 2001:db8:2::4/64 scope global
       valid_lft forever preferred_lft forever
    inet6 fe80::bc31:8009:270d:e019/64 scope link stable-privacy
       valid_lft forever preferred_lft forever
    inet6 fe80::e0:f9ff:fe45:6480/64 scope link
       valid_lft forever preferred_lft forever


> +				}
> +			}
>  		}
>  
>  		*((u32 *)ctl->data) = new_val;
>