cab0e1a6f7
This updates the syspolicy package to support multiple policy sources in the three policy scopes: user, profile, and device, and provides a merged resultant policy. A policy source is a syspolicy/source.Store that has a name and provides access to policy settings for a given scope. It can be registered with syspolicy/rsop.RegisterStore. Policy sources and policy stores can be either platform-specific or platform-agnostic. On Windows, we have the Registry-based, platform-specific policy store implemented as syspolicy/source.PlatformPolicyStore. This store provides access to the Group Policy and MDM policy settings stored in the Registry. On other platforms, we currently provide a wrapper that converts a syspolicy.Handler into a syspolicy/source.Store. However, we should update them in follow-up PRs. An example of a platform-agnostic policy store would be a policy deployed from the control, a local policy config file, or even environment variables. We maintain the current, most recent version of the resultant policy for each scope in an rsop.Policy. This is done by reading and merging the policy settings from the registered stores the first time the resultant policy is requested, then re-reading and re-merging them if a store implements the source.Changeable interface and reports a policy change. Policy change notifications are debounced to avoid re-reading policy settings multiple times if there are several changes within a short period. The rsop.Policy can notify clients if the resultant policy has changed. However, we do not currently expose this via the syspolicy package and plan to do so differently along with a struct-based policy hierarchy in the next PR. To facilitate this, all policy settings should be registered with the setting.Register function. The syspolicy package does this automatically for all policy settings defined in policy_keys.go. The new functionality is available through the existing syspolicy.Read* set of functions. However, we plan to expose it via a struct-based policy hierarchy, along with policy change notifications that other subsystems can use, in the next PR. We also plan to send the resultant policy back from tailscaled to the clients via the LocalAPI. This is primarily a foundational PR to facilitate future changes, but the immediate observable changes on Windows include: - The service will use the current policy setting values instead of those read at OS boot time. - The GUI has access to policy settings configured on a per-user basis. On Android: - We now report policy setting usage via clientmetrics. Updates #12687 Signed-off-by: Nick Khyl <nickk@tailscale.com>
DERP
This is the code for the Tailscale DERP server.
In general, you should not need to or want to run this code. The overwhelming majority of Tailscale users (both individuals and companies) do not.
In the happy path, Tailscale establishes direct connections between peers and data plane traffic flows directly between them, without using DERP for more than acting as a low bandwidth side channel to bootstrap the NAT traversal. If you find yourself wanting DERP for more bandwidth, the real problem is usually the network configuration of your Tailscale node(s), making sure that Tailscale can get direction connections via some mechanism.
If you've decided or been advised to run your own derper, then read on.
Caveats
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Node sharing and other cross-Tailnet features don't work when using custom DERP servers.
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DERP servers only see encrypted WireGuard packets and thus are not useful for network-level debugging.
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The Tailscale control plane does certain geo-level steering features and optimizations that are not available when using custom DERP servers.
Guide to running cmd/derper
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You must build and update the
cmd/derperbinary yourself. There are no packages. Usego install tailscale.com/cmd/derper@latestwith the latest version of Go. You should update this binary approximately as regularly as you update Tailscale nodes. If using--verify-clients, thederperbinary andtailscaledbinary on the machine must be built from the same git revision. (It might work otherwise, but they're developed and only tested together.) -
The DERP protocol does a protocol switch inside TLS from HTTP to a custom bidirectional binary protocol. It is thus incompatible with many HTTP proxies. Do not put
derperbehind another HTTP proxy. -
The
tailscaledclient does its own selection of the fastest/nearest DERP server based on latency measurements. Do not putderperbehind a global load balancer. -
DERP servers should ideally have both a static IPv4 and static IPv6 address. Both of those should be listed in the DERP map so the client doesn't need to rely on its DNS which might be broken and dependent on DERP to get back up.
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A DERP server should not share an IP address with any other DERP server.
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Avoid having multiple DERP nodes in a region. If you must, they all need to be meshed with each other and monitored. Having two one-node "regions" in the same datacenter is usually easier and more reliable than meshing, at the cost of more required connections from clients in some cases. If your clients aren't mobile (battery constrained), one node regions are definitely preferred. If you really need multiple nodes in a region for HA reasons, two is sufficient.
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Monitor your DERP servers with
cmd/derpprobe. -
If using
--verify-clients, atailscaledmust be running alongside thederper, and all clients must be visible to the derper tailscaled in the ACL. -
If using
--verify-clients, atailscaledmust also be running alongside yourderpprobe, andderpprobeneeds to use--derp-map=local. -
The firewall on the
derpershould permit TCP ports 80 and 443 and UDP port 3478. -
Only LetsEncrypt certs are rotated automatically. Other cert updates require a restart.
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Don't use a firewall in front of
derperthat suppressesRSTs upon receiving traffic to a dead or unknown connection. -
Don't rate-limit UDP STUN packets.
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Don't rate-limit outbound TCP traffic (only inbound).
Diagnostics
This is not a complete guide on DERP diagnostics.
Running your own DERP services requires exeprtise in multi-layer network and application diagnostics. As the DERP runs multiple protocols at multiple layers and is not a regular HTTP(s) server you will need expertise in correlative analysis to diagnose the most tricky problems. There is no "plain text" or "open" mode of operation for DERP.
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The debug handler is accessible at URL path
/debug/. It is only accessible over localhost or from a Tailscale IP address. -
Go pprof can be accessed via the debug handler at
/debug/pprof/ -
Prometheus compatible metrics can be gathered from the debug handler at
/debug/varz. -
cmd/stuncin the Tailscale repository provides a basic tool for diagnosing issues with STUN. -
cmd/derpprobeprovides a service for monitoring DERP cluster health. -
tailscale debug derpandtailscale netcheckprovide additional client driven diagnostic information for DERP communications. -
Tailscale logs may provide insight for certain problems, such as if DERPs are unreachable or peers are regularly not reachable in their DERP home regions. There are many possible misconfiguration causes for these problems, but regular log entries are a good first indicator that there is a problem.