Some users mentioned that when there is an Internet outage, ctrld fails
to recover, crashing or locks up the router. When requests start
failing, this results in the clients emitting more queries, creating a
resource spiral of death that can brick the device entirely.
To guard against this case, this commit implement an upstream monitor
approach:
- Marking upstream as down after 100 consecutive failed queries.
- Start a goroutine to check when the upstream is back again.
- When upstream is down, answer all queries with SERVFAIL.
- The checking process uses backoff retry to reduce high requests rate.
- As long as the query succeeded, marking the upstream as alive then
start operate normally.
Instead of always doubling the request, first we wrap the request with a
failover timeout, 500ms, which is an average time for a normal request.
If this request failed, trigger re-bootstrapping and retry the request.
When network changes, for example: connect/disconnect VPN, the old
connection will become broken, but still can be re-used for new
requests. That would cause un-necessary delay for ctrld clients:
- Time 0 - do request with broken transport, 5s timeout.
- Time 0.5 - network stack become usable.
- Time 5 - timeout reached.
- Time 5.1 - do request with new transport -> success.
Instead, we can do two requests in parallel, with the failover one using
a fresh new transport. So if the main one is broken, we still can get
the result from the failover one.
This commit add the ability for ctrld to gather client information,
including mac/ip/hostname, and send to Control-D server through a
config per upstream.
- Add send_client_info upstream config.
- Read/Watch dnsmasq leases files on supported platforms.
- Add corresponding client info to DoH query header
All of these only apply for Control-D upstream, though.
This commit adds the ability to start `ctrld` without config file. All
necessary information can be provided via command line flags, either in
base64 encoded config or launch arguments.
Previously, for each DoH query, we use the net/http default transport
with DialContext function re-assigned. This has some problems:
- The first query to server will be slow.
- Using the default transport for all upstreams can have race condition
in case of multiple queries to multiple DoH upstreams
This commit fixes those issues, by initializing a separate transport for
each DoH upstream, the warming up the transport by doing a test query.
Later queries can take the advantage and re-use the connection.
