WWAN, PPP, and IPv6 configuration questions

[Dan Williams <dcbw redhat com>]

Hi Tore!

I'm slowly working on getting all the IPv6 pieces together and had a
question about PPP & IPv6 that you might know.  I'm using the
Icera-based Nokia 21M that you sent me long ago, and (due to some
ModemManager bugs) it's using plain PPP.

1) What should the prefix be for the IPV6CP assigned address?  pppd
hardcodes it as '10' which seems entirely bogus to me:

    memset(&ifr6, 0, sizeof(ifr6));
    IN6_LLADDR_FROM_EUI64(ifr6.ifr6_addr, our_eui64);
    ifr6.ifr6_ifindex = ifr.ifr_ifindex;
    ifr6.ifr6_prefixlen = 10;

    if (ioctl(sock6_fd, SIOCSIFADDR, &ifr6) < 0) {

Should it be 64? Should it 128?

2) Should anything bother to set the peer address on the PPP interface?
For example, I get:

local  LL address fe80::0000:0024:5c9b:0001
remote LL address fe80::9d89:1690:be7b:438d

with IPv4 we would do "ip addr add <local>/32 peer <remote> dev ppp0",
should that same pattern be followed with IPv6?

3) Running RA on the PPP interface gives me yet another gateway:

NetworkManager[21653]: --------- NMIP6Config 0x18d6db0 (WWAN-RA)
NetworkManager[21653]:      gw: fe80::24:5c9b:40
NetworkManager[21653]:     mss: 0
NetworkManager[21653]:  n-dflt: 0

What should be done with that, if anything?  Should that replace the
peer address on ppp0?  Or should we just use it to set the default
route, but leave the peer address the same?

Thanks!
Dan