netdev - RE: "ip route show dev enp0s9" does not show all routes for enp0s9

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Message-ID: <SJ0PR84MB20889120746B75792B83693CD8D02@SJ0PR84MB2088.NAMPRD84.PROD.OUTLOOK.COM>
Date: Fri, 28 Jun 2024 02:54:58 +0000
From: "Muggeridge, Matt" <matt.muggeridge2@....com>
To: Stephen Hemminger <stephen@...workplumber.org>
CC: "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: "ip route show dev enp0s9" does not show all routes for enp0s9

> From: Stephen Hemminger <stephen@...workplumber.org>
> Sent: Friday, June 28, 2024 12:37 PM
> 
> On Fri, 28 Jun 2024 00:01:47 +0000
> "Muggeridge, Matt" <matt.muggeridge2@....com> wrote:
> 
> > Hi,
> >
> > This looks like a problem in "iproute2".  This was observed on a fresh install
> of Ubuntu 24.04, with Linux 6.8.0-36-generic.
> >
> > NOTE: I first raised this in
> https://bugs.launchpad.net/ubuntu/+source/iproute2/+bug/2070412, then
> later found https://github.com/iproute2/iproute2/blob/main/README.devel.
> >
> > * PROBLEM
> > Compare the outputs:
> >
> > $ 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.
> >
> > * REPRODUCER
> > Statically Configure systemd-networkd with two route entries, similar to the
> following:
> >
> > $ networkctl cat 10-enp0s9.network
> > # /etc/systemd/network/10-enp0s9.network
> > [Match]
> > Name=enp0s9
> >
> > [Link]
> > RequiredForOnline=no
> >
> > [Network]
> > Description="Internal Network: Private VM-to-VM IPv6 interface"
> > DHCP=no
> > LLDP=no
> > EmitLLDP=no
> >
> >
> > # /etc/systemd/network/10-enp0s9.network.d/address.conf
> > [Network]
> > Address=2001:2:0:1000:a00:27ff:fe5f:f72d/64
> >
> >
> > # /etc/systemd/network/10-enp0s9.network.d/route-1060.conf
> > [Route]
> > Gateway=fe80::200:10ff:fe10:1060
> > GatewayOnLink=true
> >
> >
> > # /etc/systemd/network/10-enp0s9.network.d/route-1061.conf
> > [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 # the routes are not shown
> >
> 
> "Don't blame the messenger", the ip command only reports what the kernel
> sends. So it is likely a route semantics issue in the kernel.

Thanks Stephen.

Ok, I have reported it on my distro in https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2071406.

I guess the kernel netdev folks will see this thread and can comment too?

Cheers,
Matt.