The bootstrap process has two issues that can make ctrld stop resolving
after restarting machine host.
ctrld uses bootstrap DNS and os nameservers for resolving upstream. On
unix, /etc/resolv.conf content is used to get available nameservers.
This works well when installing ctrld. However, after being installed,
ctrld may modify the content of /etc/resolv.conf itself, to make other
apps use its listener as DNS resolver. So when ctrld starts after OS
restart, it ends up using [bootstrap DNS + ctrld's listener], for
resolving upstream. At this moment, if ctrld could not contact bootstrap
DNS for any reason, upstream domain will not be resolved.
For above reason, an upstream may not have bootstrap IPs after ctrld
starts. When re-bootstrapping, if there's no bootstrap IPs, ctrld should
call the setup bootstrap process again. Currently, it does not, causing
all queries failed.
This commit fixes above issue by adding mechanism for retrieving OS
nameservers properly, by querying routing table information:
- Parsing /proc/net subsystem on Linux.
- For BSD variants, just fetching routing information base from OS.
- On Windows, just include the gateway information when reading iface.
The fixing for second issue is trivial, just kickoff a bootstrap process
if there's no bootstrap IPs when re-boostrapping.
While at it, also ensure that fetching resolver information from
ControlD API is also used the same approach.
Fixes#34
We only need on demand information when re-bootstrapping. On Bootsrap,
this is already checked by ctrldnet.Up, so on demand query will cause
un-necessary slow down if external ipv6 is slow to response.
Instead of re-query DNS record for upstream when re-bootstrapping, just
query all records on startup, then selecting the next bootstrap ip
depends on the current network stack.
For better recovery and dealing with network stack changes, this commit
change the request flow to:
failure of any kind -> recreate transport/re-bootstrap -> retry once
That would make ctrld recover from all scenarios in theory.
At startup, ctrld gathers bootstrap IP information and use this
bootstrap IP for connecting to upstream. However, in case the network
stack changed, for example, dues to VPN connection, ctrld will still use
this old (maybe invalid) bootstrap IP for the current network stack.
This commit rework the discovering process, and re-initializing the
bootstrap IP if connecting to upstream failed.
Supported actions:
- start: install and start ctrld as a system service
- stop: stop the ctrld service
- restart: restart ctrld service
- status: show status of ctrld service
- uninstall: remove ctrld from system service
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.
This commit adds config params to enable local DNS response caching and
control its behavior, allow tweaking the cache size, ttl override and
serving stale response.
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.
