The flag is automatically set by kernel when the valid lifetime is infinite. Note that the flag in netlink message for IPv4 address is ignored. See set_ifa_lifetime() in kernel's net/ipv4/devinet.c. But the flag is honored for IPv6 address. And if the flag is set with finite valid lifetime, the address will not removed automatically by the kernel.
System and Service Manager
Details
Most documentation is available on systemd's web site.
Assorted, older, general information about systemd can be found in the systemd Wiki.
Information about build requirements is provided in the README file.
Consult our NEWS file for information about what's new in the most recent systemd versions.
Please see the Hacking guide for information on how to hack on systemd and test your modifications.
Please see our Contribution Guidelines for more information about filing GitHub Issues and posting GitHub Pull Requests.
When preparing patches for systemd, please follow our Coding Style Guidelines.
If you are looking for support, please contact our mailing list or join our IRC channel.
Stable branches with backported patches are available in the stable repo.
