gnrc_rpl: add netif_addr to DODAG

[cgundogan]

By storing the netif_addr in the DODAG we can omit values like the prefix_len, preferred_lifetime and valid_lifetime of the IPv6 address configured by RPL PIOs. No need to store the same information at several places.

Depends on #5135

[BytesGalore]

I'm not opposing, but when we use gnrc_ipv6_netif_addr_t and rely on the set ND members, RPL cannot be used without ND.
So we have to be sure if this is what we want.

[cgundogan]

Hmm, I don't see the connection to ND here. There exists a gnrc_ipv6_netif_addr_t element for each ipv6 address that is registered at the interface.

[cgundogan]

rebased

[BytesGalore]

I mean prefix_info->valid_lifetime = dodag->netif_addr->valid; [1]. netif_addr->valid must have been set "somewhere" and I think its in ND

[1] 884663c#diff-7688fe4f626e93c827c7d5b563b80aa5R143

[cgundogan]

I am not sure whether the valid lifetime is set through ND, but it is propagated in PIO which is used in ND, but also in RPL. So there is a common interest in these values even for RPL without ND

[cgundogan]

AFAIU, the preferred and valid lifetime should be set when the ipv6 address is added to the interface. So this may set an administrator or whoever adds that ip address to the interface. RPL is just readeing those values and puts them into the PIO.

[cgundogan]

AFAIU, the preferred and valid lifetime should be set when the ipv6 address is added to the interface.

Although, I think we currently do not support this and the lifetimes are infinite (:

[cgundogan]

there is however one problem that we also have without this PR: If someone deletes the ipv6 address that is used for this DODAG (and with this PR, the same is true for the according gnrc_ipv6_netif_t struct), then we will have undefined behaviour. This is unrelated to this PR, but needs to be addressed soon.

[BytesGalore]

Ok, looks good codewise 👍

[BytesGalore]

we should open an issue for it

[BytesGalore]

works as expected so ACK

[BytesGalore]

then we will have undefined behaviour.

I guess then we will get a nullpointer exception and/or corrupt the memory of others