networkd: IPv6 router discovery - follow IPv6AcceptRouterAdvertisemnt=

The previous behavior:
When DHCPv6 was enabled, router discover was performed first, and then DHCPv6 was
enabled only if the relevant flags were passed in the Router Advertisement message.
Moreover, router discovery was performed even if AcceptRouterAdvertisements=false,
moreover, even if router advertisements were accepted (by the kernel) the flags
indicating that DHCPv6 should be performed were ignored.

New behavior:
If RouterAdvertisements are accepted, and either no routers are found, or an
advertisement is received indicating DHCPv6 should be performed, the DHCPv6
client is started. Moreover, the DHCP option now truly enables the DHCPv6
client regardless of router discovery (though it will probably not be
very useful to get a lease withotu any routes, this seems the more consistent
approach).

The recommended default setting should be to set DHCP=ipv4 and to leave
IPv6AcceptRouterAdvertisements unset.

1 files changed, 1 insertions, 0 deletions

diff --git a/src/network/networkd-link.h b/src/network/networkd-link.h
index d915e7c9c0..f453665655 100644
--- a/src/network/networkd-link.h
+++ b/src/network/networkd-link.h
@@ -157,6 +157,7 @@ bool link_ipv6ll_enabled(Link *link);
 bool link_dhcp4_server_enabled(Link *link);
 bool link_dhcp4_enabled(Link *link);
 bool link_dhcp6_enabled(Link *link);
+bool link_ipv6_accept_ra_enabled(Link *link);
 
 const char* link_state_to_string(LinkState s) _const_;
 LinkState link_state_from_string(const char *s) _pure_;