with dnsmasq server setup:
$ ip -4 a show ens8
3: ens8: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP
group default qlen 1000
inet 1.2.3.1/24 scope global ens8
valid_lft forever preferred_lft forever
$ cat /etc/dnsmasq.d/test
interface=ens8
bind-dynamic
no-resolv
no-poll
domain=test,1.2.3.4/24
dhcp-range=test,1.2.3.100,1.2.3.199,1m
dhcp-host=52:54:00:f7:b2:99,1.2.3.50,1m
on the test system:
ubuntu@lp1831787-e:~$ dpkg -l systemd | grep ii
ii systemd 242-7ubuntu3.2 amd64 system and service manager
ubuntu@lp1831787-e:~$ ip -4 a show dev ens8
3: ens8: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP
group default qlen 1000
inet 1.2.3.50/24 brd 1.2.3.255 scope global dynamic ens8
valid_lft 106sec preferred_lft 106sec
ubuntu@lp1831787-e:~$ ip -4 r
default via 1.2.3.1 dev ens8 proto dhcp src 1.2.3.50 metric 1024
1.2.3.0/24 dev ens8 proto kernel scope link src 1.2.3.50
1.2.3.1 dev ens8 proto dhcp scope link src 1.2.3.50 metric 1024
then on dnsmasq server, change the test system addr to .60:
$ cat /etc/dnsmasq.d/test
interface=ens8
bind-dynamic
no-resolv
no-poll
domain=test,1.2.3.4/24
dhcp-range=test,1.2.3.100,1.2.3.199,1m
dhcp-host=52:54:00:f7:b2:99,1.2.3.60,1m
ubuntu@dhcp-test:~$ sudo systemctl restart dnsmasq
on test system, wait for dhcp lease to timeout:
ubuntu@lp1831787-e:~$ ip -4 a show dev ens8
3: ens8: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP
group default qlen 1000
inet 1.2.3.60/24 brd 1.2.3.255 scope global dynamic ens8
valid_lft 114sec preferred_lft 114sec
ubuntu@lp1831787-e:~$ ip -4 r
default via 1.2.3.1 dev ens8 proto dhcp src 1.2.3.60 metric 1024
1.2.3.0/24 dev ens8 proto kernel scope link src 1.2.3.60
1.2.3.1 dev ens8 proto dhcp scope link src 1.2.3.60 metric 1024
** Tags removed: verification-needed verification-needed-eoan
** Tags added: verification-done verification-done-eoan
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https://bugs.launchpad.net/bugs/1831787
Title:
Bogus routes after DHCP lease change
Status in netplan:
Invalid
Status in systemd:
Unknown
Status in systemd package in Ubuntu:
In Progress
Status in systemd source package in Bionic:
In Progress
Status in systemd source package in Disco:
In Progress
Status in systemd source package in Eoan:
Fix Committed
Bug description:
[impact]
networkd does not remove old route(s) after DHCP address change
[test case]
on a system using networkd, that is connected to a network where you
can control the addresses that the DHCP server provides, setup system
with networkd to get address via DHCP, e.g.
[Match]
Name=ens3
[Network]
DHCP=ipv4
(re)start networkd or reboot, so the system gets an ipv4 DHCP address, and
corresponding route to the gateway.
Then on the dhcp server, change the subnet to a different subnet. On the
client, once its renews its DHCP address, the server will provide a new address
in the new subnet, and the client will add a new default route to the new
gateway address. However, the old default route to the old gateway address
isn't removed.
Note this also happens without changing the entire subnet, but is more
subtle as shown in the original description.
[regression potential]
this affects how networkd handles routes, so has the potential to
leave a system with partial or incorrect networking, or no networking
at all. Any regression would most likely occur during networkd
(re)start or during renewal of a DHCP lease, or when an interface is
brought up.
[other info]
original description:
---
Netplan config:
network:
version: 2
renderer: networkd
ethernets:
eno4:
dhcp4: no
eno1np0:
dhcp4: no
addresses:
- 172.16.0.2/24
bridges:
br0:
dhcp4: yes
interfaces:
- eno4
On initial boot, machine got 10.0.15.109 IP address:
May 03 13:09:41 ceph2 systemd-networkd[29349]: br0: Configured
May 03 13:09:41 ceph2 systemd-networkd[29349]: br0: DHCPv4 address
10.0.15.109/23 via 10.0.15.253
At one point, DHCP server reserver this IP address and client
eventually picked up new IP address:
May 03 15:01:12 ceph2 systemd-networkd[1137]: br0: DHCPv4 address
10.0.15.128/23 via 10.0.15.253
This resulted in IP addresses:
# ip -o a
1: lo inet 127.0.0.1/8 scope host lo\ valid_lft forever
preferred_lft forever
1: lo inet6 ::1/128 scope host \ valid_lft forever preferred_lft
forever
2: eno1np0 inet 172.16.0.2/24 brd 172.16.0.255 scope global eno1np0\
valid_lft forever preferred_lft forever
2: eno1np0 inet6 fe80::b226:28ff:fe53:56be/64 scope link \ valid_lft
forever preferred_lft forever
6: br0 inet 10.0.15.128/23 brd 10.0.15.255 scope global dynamic br0\
valid_lft 503sec preferred_lft 503sec
6: br0 inet6 fe80::b8d7:5eff:fe6b:62a/64 scope link \ valid_lft
forever preferred_lft forever
So far, everything is fine. But, the routes on the machine are bogus:
# ip r
default via 10.0.15.253 dev br0 proto dhcp src 10.0.15.109 metric 100
default via 10.0.15.253 dev br0 proto dhcp src 10.0.15.128 metric 100
10.0.14.0/23 dev br0 proto kernel scope link src 10.0.15.128
10.0.15.253 dev br0 proto dhcp scope link src 10.0.15.109 metric 100
10.0.15.253 dev br0 proto dhcp scope link src 10.0.15.128 metric 100
172.16.0.0/24 dev eno1np0 proto kernel scope link src 172.16.0.2
routes with src 10.0.15.109 should have been removed when lease was
renewed. I'm not sure if this is a bug in netplan or systemd. This is
18.04, systemd 37-3ubuntu10.21, netplan 0.40.1~18.04.4.
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