Silvio, thanks for the suggestion. I'm not concerned with keeping the lease forever; the system actually experiences a topology change as it's switched from one network to another, and I can catch that from the DBus events that occur. The problem we're trying to solve is to contact some address that we're sure exists on the network, without knowing anything about that network. The default gateway was an obvious choice, but someone wants to cover the case of there being a private LAN with no gateway. The only other choice I could see is the DHCP server that issues the lease.
As my thinking has evolved, I really want to get at more DHCP
lease information when it comes in, like a private DHCP option
code that conveys something about the environment. I came across a
comment somewhere that said the only way is to set the
systemd-networkd client to use debug log level and read from the
journal, but isn't there a more direct way, like with the Dbus
signals that tell subscribers about network interface status?
Bruce A. Johnson | Firmware Engineer Blue Ridge Networks, Inc. 14120 Parke Long Court Suite 103 | Chantilly, VA 20151 Main: 1.800.722.1168 | Direct: 703-633-7332 http://www.blueridgenetworks.com OpenPGP key ID: 296D1CD6F2B84CAB https://keys.openpgp.org/
Am Mittwoch, dem 21.04.2021 um 14:24 -0400 schrieb Bruce A. Johnson:Is there a correct way to obtain information about the DHCP lease received by systemd-networkd's DHCP client functionality? It was easy enough to find SERVER_ADDRESS in /var/run/systemd/netif/leases/4, but there is a big fat warning stamped at the top of the file:# This is private data. Do not parse.I'd like to be able to make a widget that can tell me which DHCP server issued my lease, how much more time I have, etc., mainly because I want to be able to ping something that is known to be on the network. I'm dealing with a lazy sysadmin who doesn't want to put a gateway on this private network, I haven't found a solution using the CLI tools. Thanks in advance.Hi Bruce, IMHO "having a lease" is not a good metric to determine if you can access something. I would suggest something along this line: --- /etc/systemd/system/internal-network-accessable.target [Unit] Description=Internal System Accessable --- --- /etc/systemd/system/check-if-internal-system-is-accessable.service [Unit] Description=Check if internal system can be reached [Service] ExecStart=/usr/local/bin/check-if-internal-system-is-accessable.sh Restart=always [Install] WantedBy=multi-user.target --- --- /usr/local/bin/check-if-internal-system-is-accessable.sh #!/usr/bin/bash while :; do if wget -q --spider $INTERNAL_RESOURCE; then systemctl start internal-network-accessable.target else systemctl stop internal-network-accessable.target fi sleep 600 done --- Than you can check just the status of the .target. You may need to tweak the lifeness probe, YMMV. Also in sd-networkd you can configure a .network to never loose its lease, see man:systemd.network → KeepConfiguration= HTH Silvio
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