This also relaxes the inode access modes a bit, in case they were set to
0600: we now set the "r" bit too, i.e. use 0644. This is beneficial
since it permits unpriv code to read the xattrs of the entrypoints
(which require read access). Note that in order to be able to connect()
to a socket inode you need write access, hence this shouldn't compromise
security in any way.
Otherwise, it introduces cyclic dependencies:
```
systemd[1]: sockets.target: Found ordering cycle:
systemd-networkd-resolve-hook.socket/start after network-pre.target/start after
iptables.service/start after basic.target/start after sockets.target/start -
after systemd-networkd-resolve-hook.socket
systemd[1]: sockets.target: Job systemd-networkd-resolve-hook.socket/start deleted
to break ordering cycle starting with sockets.target/start
```
Follow-up for 37adb410a2.
Fixes#42353.
Without this, the socket is available well before systemd-networkd.service
is able to start, because of its own After=network-pre.target ordering.
Then, if resolved handles queries before network-pre.target, it will
hang waiting for networkd to reply to hook queries.
This is currently happening in the wild with cloud-init.
Let's synthesize DNS RRs for leases handed out by our DHCP server. This
way local VMs can have resolvable hostnames locally.
This does not implement reverse look ups for now. We can add this
later in similar fashion.
Lennart Poettering
Yu Watanabe
Nick Rosbrook
Lennart Poettering