systemd-networkd: UseRoutes behavior change with introduction of UseGateway param
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
netplan.io (Ubuntu) |
Confirmed
|
Undecided
|
Unassigned | ||
Bionic |
Invalid
|
Undecided
|
Unassigned | ||
Eoan |
Invalid
|
Undecided
|
Unassigned | ||
Focal |
Confirmed
|
Undecided
|
Unassigned | ||
Groovy |
Won't Fix
|
Undecided
|
Unassigned | ||
systemd (Ubuntu) |
Fix Released
|
High
|
Dan Streetman | ||
Bionic |
Fix Released
|
Medium
|
Dan Streetman | ||
Eoan |
Fix Released
|
Medium
|
Dan Streetman | ||
Focal |
Fix Released
|
High
|
Dan Streetman | ||
Groovy |
Fix Released
|
High
|
Dan Streetman |
Bug Description
[impact]
the networkd UseRoutes parameter allowed ignoring all routes provided by a dhcp4 server, including the route via the dhcp4-provided gateway. This was the behavior of networkd until recently, and in Focal the UseRoutes parameter does *not* prevent networkd from adding the route via the dhcp4-provided gateway. This is now controlled with a new parameter, UseGateway.
The systemd in Focal unfortunately has part of the upstream code; it no longer ignores the gateway route when UseRoutes=false is specified, but also it does not include the UseGateway parameter.
Before Focal, networkd did not allow ignoring dhcpv4 routes and the gateway separately; the UseRoutes= parameter either used, or ignored, both. This is why upstream added the UseGateway= paramter, which should be backported to allow control of ignoring the dhcpv4 routes and gateway separately.
[test case]
In Focal, bug 1872589 has a good test case netplan config, but a very quick test can be done with the networkd config:
[Match]
Name=eth0
[Network]
DHCP=ipv4
LinkLocalAddres
[DHCP]
RouteMetric=100
UseMTU=true
UseRoutes=false
this results in the system incorrectly setting a route via the default gateway:
root@lp1867375-f:~# ip r
default via 10.202.51.1 dev eth0 proto dhcp src 10.202.51.86 metric 100
10.202.51.0/24 dev eth0 proto kernel scope link src 10.202.51.86
10.202.51.1 dev eth0 proto dhcp scope link src 10.202.51.86 metric 100
Before Focal, the above test case shows "correct" behavior, but there is no way to ignore the dhcpv4 routes but use the dhcpv4 gateway. This pre-Focal, the test case would be to use the UseGateway= parameter, e.g.:
[Match]
Name=eth0
[Network]
DHCP=ipv4
LinkLocalAddres
[DHCP]
RouteMetric=100
UseMTU=true
UseRoutes=false
UseGateway=true
which *should* result in the default gateway being configured:
root@lp1867375-f:~# ip r
default via 10.202.51.1 dev eth0 proto dhcp src 10.202.51.86 metric 100
10.202.51.0/24 dev eth0 proto kernel scope link src 10.202.51.86
10.202.51.1 dev eth0 proto dhcp scope link src 10.202.51.86 metric 100
[regression potential]
Any regression would likely involve incorrect setting, or ignoring, of dhcpv4-provided routes, and/or incorrect setting, or ignoring, of the dhcpv4-provided gateway.
[scope]
This is fixed by these upstream PRs:
https:/
https:/
https:/
Parts of all those PRs are required in Focal, Eoan, and Bionic.
I am not fixing this for Xenial, at this time.
For Debian, I opened this MR:
https:/
For Groovy, I opened this MR:
https:/
[other info]
to properly support separation of 'routes' and 'gateways' received via dhcp4, SRU releases should also support the UseGateway parameter, which is what this bug was originally opened requesting.
[original description]
requesting backport of PR https:/
https:/
summary: |
- systemd-network: Setting UseRoutes to False results in DHCP default + systemd-networkd: Setting UseRoutes to False results in DHCP default gateway not being installed |
tags: | added: ddstreet |
description: | updated |
Changed in netplan.io (Ubuntu Bionic): | |
status: | New → Invalid |
Changed in netplan.io (Ubuntu Eoan): | |
status: | New → Invalid |
description: | updated |
description: | updated |
Changed in systemd (Ubuntu Bionic): | |
assignee: | nobody → Dan Streetman (ddstreet) |
Changed in systemd (Ubuntu Eoan): | |
assignee: | nobody → Dan Streetman (ddstreet) |
Changed in systemd (Ubuntu Focal): | |
assignee: | nobody → Dan Streetman (ddstreet) |
Changed in systemd (Ubuntu Bionic): | |
importance: | Undecided → Medium |
Changed in systemd (Ubuntu Eoan): | |
importance: | Undecided → Medium |
Changed in systemd (Ubuntu Focal): | |
importance: | Undecided → High |
status: | Fix Released → In Progress |
Changed in systemd (Ubuntu Eoan): | |
status: | Confirmed → In Progress |
Changed in systemd (Ubuntu Bionic): | |
status: | Confirmed → In Progress |
description: | updated |
description: | updated |
Fixed in 245