** Description changed:
[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
LinkLocalAddressing=ipv6
[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
LinkLocalAddressing=ipv6
[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://github.com/systemd/systemd/pull/15443
https://github.com/systemd/systemd/pull/15136
https://github.com/systemd/systemd/pull/14983
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://salsa.debian.org/systemd-team/systemd/-/merge_requests/92
+
+ For Groovy, I opened this MR:
+
https://code.launchpad.net/~ddstreet/ubuntu/+source/systemd/+git/systemd/+merge/383661
+
[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://github.com/systemd/systemd/pull/14983 which
fixes the issue described in
https://github.com/systemd/systemd/issues/14982 to 18.04 (bionic)
** Also affects: systemd (Ubuntu Groovy)
Importance: High
Assignee: Dan Streetman (ddstreet)
Status: In Progress
** Also affects: netplan.io (Ubuntu Groovy)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1867375
Title:
systemd-networkd: UseRoutes behavior change with introduction of
UseGateway param
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