The commit b3762fc61c ("gluon-client-bridge: move IPv4 local subnet route
to br-client (#1312)") moves the IPv4 prefix from the local-port interface
to br-client. A client requesting an IPv4 connection to the IPv4 anycast
address of the node (the device running gluon) will create following
packets:
1. ARP packet from client to get the MAC of the mac address of the anycast
IPv4 address
2. ARP reply from node to client with the anycast MAC address for the IPv4
anycast address
3. IPv4 packet from client which requires reply (for example ICMP echo
request)
4. ARP request for the client MAC address for its IPv4 address in prefix4
(done with the mac address of br-client and transmitted over br-client)
5. IPv4 packet from node (transmitted over br-client with br-client MAC
address) as reply for the client IPv4 packet (for example ICMP echo
reply)
The step 4 and 5 are problematic here because packets use the node specific
MAC addresses from br-client instead of the anycast MAC address. The client
will receive the ARP packet with the node specific MAC address and change
their own neighbor IP (translation) table. This will for example break the
access to the status page to the connected device or the anycast DNS
forwarder implementation when the client roams to a different node.
This reverts commit b3762fc61c and adds an
upgrade code to remove local_node_route on on existing installations.
This patch moves the prefix4 subnet route from the local-node veth
device to br-client (while keeping the next node ipv4 address on the
local node device).
This is in preparation to allow routing over the br-client interface
later.
We always want to prefer the unique node address for outgoing traffic. Note
that this doesn't have an effect with batman-adv, as usually br-client will
be the outgoing interface, so the unique address would be chosen anyways.
macvlan interfaces never directly exchange traffic with the underlying
interface, but only with other hosts behind the interface. In consequence,
router advertisements from the uradvd running on br-client could never
reach local-node, preventing it from getting an IPv6 address without RAs
from an external radvd. Fix this be replacing the macvlan interface with
a veth pair (with the peer interface in br-client).
As a side effect, this saves about 5KB of flash, as the veth module is
simpler than macvlan.
When preparing the migration from macvlan to veth for local-node, MAC
address conflicts occurred as some ports of br-client had the same address
as local-node. Reverting the roles of both interfaces fixes this.
By default, br-client is left as an interface without addresses and
firewall rules that drop everything, so the bridge is used to connect its
ports only. gluon-mesh-batman-adv-core changes this to the usual set
of addresses and firewall rules.
