Re: [PATCH net] net/ipv6: re-do dad when interface has IFF_NOARP flag change

[David Miller <davem@davemloft.net>]

From: Hangbin Liu <liuhangbin@gmail.com>
Date: Wed, 21 Nov 2018 21:52:33 +0800

> When we add a new IPv6 address, we should also join corresponding solicited-node
> multicast address, unless the interface has IFF_NOARP flag, as function
> addrconf_join_solict() did. But if we remove IFF_NOARP flag later, we do
> not do dad and add the mcast address. So we will drop corresponding neighbour
> discovery message that came from other nodes.
> 
> A typical example is after creating a ipvlan with mode l3, setting up an ipv6
> address and changing the mode to l2. Then we will not be able to ping this
> address as the interface doesn't join related solicited-node mcast address.
> 
> Fix it by re-doing dad when interface changed IFF_NOARP flag. Then we will add
> corresponding mcast group and check if there is a duplicate address on the
> network.
> 
> Reported-by: Jianlin Shi <jishi@redhat.com>
> Reviewed-by: Stefano Brivio <sbrivio@redhat.com>
> Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>

Applied.