Add extra logging around network issues (EDE: network error)

[DL6ER]

What does this implement/fix?

This PR adds further error logging concerning (intermittent) network issues. Currently, dnsmasq doesn't provide any further details, making debugging quite hard. This PR was triggered by pi-hole/pi-hole#5608 which, eventually, turned out to be an external issue with other services on the same machine.

Example: Simulating network outage by unplugging the Ethernet cable

UDP

dig google.com

Before:

Apr  2 12:14:43 dnsmasq[3791404]: query[A] 154.google.com from 127.0.0.1
Apr  2 12:14:43 dnsmasq[3791404]: config error is REFUSED (EDE: network error)

Now:

Apr  2 12:14:43 dnsmasq[3791404]: query[A] 154.google.com from 127.0.0.1
Apr  2 12:14:43 dnsmasq[3791404]: failed to send UDP request: Network is unreachable
Apr  2 12:14:43 dnsmasq[3791404]: config error is REFUSED (EDE: network error)

TCP

dig google.com +tcp

Before:

Apr  2 11:53:02 dnsmasq[3801913]: query[A] google.com from 127.0.0.1
(editor's note: nothing else gets printed, the TCP connection silently dies)

Now:

Apr  2 11:53:02 dnsmasq[3801913]: query[A] google.com from 127.0.0.1
Apr  2 11:53:02 dnsmasq[3801913]: failed to send TCP(fast-open) packet: Network is unreachable
Apr  2 11:53:02 dnsmasq[3801913]: failed to send TCP(connect) packet: Network is unreachable

Other possible errors could be Connection reset by peer or No memory available.

These errors are also logged to the diagnosis system (rate-limited to not hammer the database):

These messages are de-duplicated based on the peer address (192.168.2.1#53 in the screenshot).

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Related issue or feature (if applicable): N/A

Pull request in docs with documentation (if applicable): N/A

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Checklist:

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