"ip route show dev enp0s9" does not show all routes for enp0s9

[Matt]

NOTE: Originally reported in iproute2 (https://bugs.launchpad.net/ubuntu/+source/iproute2/+bug/2070412). However, netdev mailing list indicates this is a linux kernel problem and not an iproute2 problem, so recreating the report here.

Compare the outputs below:

$ ip -6 route show dev enp0s9
2001:2:0:1000::/64 proto ra metric 1024 expires 65518sec pref medium
fe80::/64 proto kernel metric 256 pref medium

$ ip -6 route
2001:2:0:1000::/64 dev enp0s9 proto ra metric 1024 expires 65525sec pref medium
fe80::/64 dev enp0s3 proto kernel metric 256 pref medium
fe80::/64 dev enp0s9 proto kernel metric 256 pref medium
default proto ra metric 1024 expires 589sec pref medium
 nexthop via fe80::200:10ff:fe10:1060 dev enp0s9 weight 1
 nexthop via fe80::200:10ff:fe10:1061 dev enp0s9 weight 1

The default route is associated with enp0s9, yet the first command above does not show it.

FWIW, the two default route entries were created by two separate routers on the network, each sending their RA.

-----

In case you have trouble creating the condition that reproduces this bug, a simple static networkd configuration will do the job...

Configure systemd-networkd

E.g. assume your interface is called enp0s9 and you already have add a config file in /etc/system/network/10-enp0s9.network. Now add an override.conf as follows:

$ cat /etc/systemd/network/10-enp0s9.network.d/override.conf
[Network]
Address=2001:2:0:1000:a00:27ff:fe5f:f72d/64

[Route]
Gateway=fe80::200:10ff:fe10:1060
GatewayOnLink=true

[Route]
Gateway=fe80::200:10ff:fe10:1061
GatewayOnLink=true

Now reload and reconfigure the interface and you will see two routes.

$ networkctl reload
$ networkctl reconfigure enp0s9
$ ip -6 r
$ ip -6 r show dev enp0s9

NOTE: You can also create the same scenario by having systemd-networkd accept RAs from multiple routers, but that requires more setup.

ProblemType: Bug
DistroRelease: Ubuntu 24.04
Package: linux-image-6.8.0-36-generic 6.8.0-36.36
ProcVersionSignature: Ubuntu 6.8.0-36.36-generic 6.8.4
Uname: Linux 6.8.0-36-generic x86_64
ApportVersion: 2.28.1-0ubuntu3
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/seq: matt 2599 F.... pipewire
 /dev/snd/controlC0: matt 2603 F.... wireplumber
CRDA: N/A
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Fri Jun 28 12:43:28 2024
InstallationDate: Installed on 2024-06-24 (4 days ago)
InstallationMedia: Ubuntu 24.04 LTS "Noble Numbat" - Release amd64 (20240424)
Lsusb:
 Bus 001 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
 Bus 001 Device 002: ID 80ee:0021 VirtualBox USB Tablet
 Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Lsusb-t:
 /: Bus 001.Port 001: Dev 001, Class=root_hub, Driver=ohci-pci/12p, 12M
     |__ Port 001: Dev 002, If 0, Class=Human Interface Device, Driver=usbhid, 12M
 /: Bus 002.Port 001: Dev 001, Class=root_hub, Driver=ehci-pci/12p, 480M
MachineType: innotek GmbH VirtualBox
ProcEnviron:
 LANG=en_US.UTF-8
 PATH=(custom, no user)
 SHELL=/bin/bash
 TERM=xterm-256color
 XDG_RUNTIME_DIR=<set>
ProcFB: 0 vmwgfxdrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-6.8.0-36-generic root=UUID=d3096757-b767-4cf4-8b9c-c65a87bd4f4e ro quiet splash vt.handoff=7
RelatedPackageVersions:
 linux-restricted-modules-6.8.0-36-generic N/A
 linux-backports-modules-6.8.0-36-generic N/A
 linux-firmware 20240318.git3b128b60-0ubuntu2.1
RfKill:

SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 12/01/2006
dmi.bios.vendor: innotek GmbH
dmi.bios.version: VirtualBox
dmi.board.name: VirtualBox
dmi.board.vendor: Oracle Corporation
dmi.board.version: 1.2
dmi.chassis.type: 1
dmi.chassis.vendor: Oracle Corporation
dmi.modalias: dmi:bvninnotekGmbH:bvrVirtualBox:bd12/01/2006:svninnotekGmbH:pnVirtualBox:pvr1.2:rvnOracleCorporation:rnVirtualBox:rvr1.2:cvnOracleCorporation:ct1:cvr:sku:
dmi.product.family: Virtual Machine
dmi.product.name: VirtualBox
dmi.product.version: 1.2
dmi.sys.vendor: innotek GmbH

[Jay Vosburgh (jvosburgh)]

Subsequent upstream discussion aims this back at iproute2 filtering logic:

https://<email address hidden>/

[Matt (livefreeandroam)]

Fixed by netdev team. See:

https://marc.info/?l=linux-netdev&m=171976458316116&w=2