dhcpcd-discuss

On 06/01/2019 00:51, Raphaël Halimi wrote:
> Hi,
>
> I have a problem with dhcpcd which, even after several days of googling,
> I'm unfortunately unable to solve.
>
> Here's a quick description of my setup:
>
> My LAN is equipped with a DSL modem/switch lent from my ISP, which sends
> IPv6 Router Advertisements to devices connected to its four ports. I
> also have one host which is my "main" server, as it offers DHCP (both
> IPv4/IPv6), DNS, and also hosts virtual machines behind a purely virtual
> bridge (not connected to any physical interface). It also acts as the
> default IPv4 gateway for other LAN hosts. It's not the default IPv6
> gateway though, because the ISP's box still sends RAs even when I enable
> the option supposed to disable them; it seems broken), but it has radvd
> installed nevertheless to send RAs to the virtual machines, and also to
> the physical hosts (to instruct them on how to reach the VMs).
>
> Here's my problem:
>
> I have a Raspberry Pi with Raspbian installed, which uses dhcpcd. All
> other hosts are "pure" Debian, and thus use either ifupdown (on servers)
> or NetworkManager (on desktops) instead.
>
> On the server, radvd is configured like this for the physical interface:
>
> interface mvl1 {
>    AdvSendAdvert on;
>    AdvDefaultLifetime 0;
>    prefix fdxx:y:z:1::/64 { AdvOnLink on; AdvAutonomous off; };
>    route fdxx:y:z:2::/64 { AdvRoutePreference high; };
>    AdvManagedFlag on;
>    AdvOtherConfigFlag on;
> };
>
> dhcpcd's logs show that it does receive RAs from both the ISP's router
> and my server:
>
> dhcpcd[295]: wlan0: Router Advertisement from fe80::a:b:c:d
> dhcpcd[295]: wlan0: adding address 2a01:x:y:z:a:b:c:d/64
> dhcpcd[295]: wlan0: adding route to 2a01:x:y:z::/64
> dhcpcd[295]: wlan0: adding default route via fe80::a:b:c:d
> dhcpcd[295]: wlan0: Router Advertisement from fe80::c:d:e:f
> dhcpcd[295]: wlan0: adding route to fdxx:y:z:1::/64
> ...
> dhcpcd[1049]: wlan0: REPLY6 received from fe80::c:d:e:f
> dhcpcd[1049]: wlan0: adding address fdxx:y:z:1::30/128
>
> (2a01... is the prefix advertised by the ISP's box to reach the outside
> world; fdxx... are ULAs inside my LAN, served by DHCPv6; fe80::a:b:c:d
> is the ISP's box link-local address, and fe80::c:d:e:f is the server's
> link-local address)
>
> As you can see, it only adds the default route from the ISP's router,
> but not the additional route advertised by the server; ip -6 route gives:
>
> 2a01:x:y:z::/64 dev wlan0 proto kernel metric 303  mtu 1480 pref medium
> fdxx:y:z:1::/64 dev wlan0 proto kernel metric 303  pref medium
> fe80::/64 dev wlan0 proto kernel metric 256  pref medium
> default via fe80::a:b:c:d dev wlan0 metric 303  mtu 1480 pref medium
>
> On another host, NetworkManager does the right thing and adds both routes:
>
> 2a01:x:y:z::/64 dev enp4s0 proto ra metric 100 pref medium
> fdxx:y:z:1::100 dev enp4s0 proto kernel metric 100 pref medium
> fdxx:y:z:1::/64 dev enp4s0 proto ra metric 100 pref medium
> fdxx:y:z:2::/64 via fe80::c:d:e:f dev enp4s0 proto ra metric 100 pref high
> fe80::/64 dev enp4s0 proto kernel metric 100 pref medium
> default via fe80::a:b:c:d dev enp4s0 proto ra metric 100 pref medium
>
> I couldn't verify that ifupdown acts like dhcpcd, or does the right
> thing like NetworkManager, since all servers are virtual, and have a
> static network configuration.
>
> I also tried to add ipv6ra_own to /etc/dhcpcd.conf but it didn't work.
>
> Any help would be very much appreciated; as I said, I'm asking here as a
> last resort, having crawled Google for days without success.

This is a bug in dhcpcd and likely most BSD kernels as well.

Fixed here:
https://roy.marples.name/git/dhcpcd.git/commit/?id=12489da256cfd51afb736b278b88510e5e4303e7

Roy