netavark: dhcp: cannot add default route when using multiple networks with dhcp ipam-driver

[agorgl]

Passing multiple macvlan networks with dhcp ipam-driver in a container, results to:

Error: netavark: unable to obtain lease: dhcp proxy error: status: Unknown, message: "add default route (dest: 0.0.0.0/0 ,gw: 192.168.122.1, metric 100): Netlink error: File exists (os error 17)"

even when we specify to not add a default route in the rest of them.

The problem can be reproduced on a host with 2 network interfaces (in this example enp1s0 and enp7s0) doing the following:

user@test:~$ sudo podman network create --driver macvlan --ipam-driver dhcp --opt parent=enp1s0 macvlan1
macvlan1
user@test:~$ sudo podman network create --driver macvlan --ipam-driver dhcp --opt parent=enp7s0 --opt no_default_route=1 macvlan2
macvlan2
user@test:~$ sudo podman run --name test --replace --rm --network macvlan1 --network macvlan2 caddy:latest
Resolving "caddy" using unqualified-search registries (/etc/containers/registries.conf)
Trying to pull docker.io/library/caddy:latest...
Getting image source signatures
Copying blob 4f4fb700ef54 done   |
Copying blob 6a0ac1617861 done   |
Copying blob 5920de1d55d9 done   |
Copying blob 057c497bda06 done   |
Copying blob 3b55c68e4a0f done   |
Copying config 5190456911 done   |
Writing manifest to image destination
[  651.570571] virtio_net virtio1 enp1s0: entered promiscuous mode
[  654.578605] virtio_net virtio1 enp1s0: left promiscuous mode
[  654.593383] virtio_net virtio6 enp7s0: entered promiscuous mode
[  654.597027] virtio_net virtio6 enp7s0: left promiscuous mode
Error: netavark: unable to obtain lease: dhcp proxy error: status: Unknown, message: "add default route (dest: 0.0.0.0/0 ,gw: 192.168.122.1, metric 100): Netlink error: File exists (os error 17)", details: [], metadata: MetadataMap { headers: {"content-type": "application/grpc", "date": "Sun, 31 May 2026 20:13:17 GMT", "content-length": "0"} }

It also can be reproduced using the more modern --interface-name and --internal flags (instead of --opt parent= and --opt no_default_route=1 respectively):

user@test:~$ sudo podman network create --driver macvlan --ipam-driver dhcp --interface-name=enp1s0 macvlan1
macvlan1
user@test:~$ sudo podman network create --driver macvlan --ipam-driver dhcp --interface-name=enp7s0 --internal macvlan2
macvlan2
user@test:~$ sudo podman run --name test --replace --rm --network macvlan1 --network macvlan2 caddy:latest
Resolving "caddy" using unqualified-search registries (/etc/containers/registries.conf)
Trying to pull docker.io/library/caddy:latest...
Getting image source signatures
Copying blob 4f4fb700ef54 done   |
Copying blob 6a0ac1617861 done   |
Copying blob 5920de1d55d9 done   |
Copying blob 057c497bda06 done   |
Copying blob 3b55c68e4a0f done   |
Copying config 5190456911 done   |
Writing manifest to image destination
[  705.398967] virtio_net virtio1 enp1s0: entered promiscuous mode
[  708.406993] virtio_net virtio1 enp1s0: left promiscuous mode
[  708.420220] virtio_net virtio6 enp7s0: entered promiscuous mode
[  708.423986] virtio_net virtio6 enp7s0: left promiscuous mode
Error: netavark: unable to obtain lease: dhcp proxy error: status: Unknown, message: "add default route (dest: 0.0.0.0/0 ,gw: 192.168.122.1, metric 100): Netlink error: File exists (os error 17)", details: [], metadata: MetadataMap { headers: {"content-type": "application/grpc", "date": "Sun, 31 May 2026 20:14:11 GMT", "content-length": "0"} }

I think that the root cause is that the dhcp ipam-driver possibly doesn't respect the --opt no_default_route=1 (or the more modern --internal) flag at all.