Brad Fitzpatrick
ab4262680b
Nothing reads ipn.Notify.NetMap anymore. The previous commit removed its runtime (non-initial) emission, and every first-party client is also off the initial one: the Win32 and WinUI GUIs and the Apple bridge subscribe with InitialStatus or InitialState plus peer deltas, Android no longer uses it, and the remaining in-tree subscribers that set NotifyInitialNetMap (sniproxy and the kube helpers) only did so to get the initial Notify.SelfChange and discarded the netmap that tailscaled built, encoded, and shipped for them. Delete the Notify.NetMap field and the NotifyInitialNetMap bit. The bit value stays reserved under the name ObsoleteNotifyInitialNetMap and ValidateNotifyWatchOpt rejects subscriptions that set it, like the NotifyRateLimit bit removed in the previous commit. NotifyNoNetMap remains accepted as a no-op because shipping GUIs still set it. The blessed way to seed a watcher's view is NotifyInitialStatus, but it unconditionally built O(peers) status entries, which is exactly the waste this series is deleting for watchers that only care about the self node. Size the initial status to the subscription instead: Status.Peer is only populated when the watcher also set NotifyPeerChanges or NotifyPeerPatches, since only peer-delta subscribers need a peer baseline to apply deltas to. That matches its existing first-party users (containerboot and the WinUI GUI both pair InitialStatus with peer bits). Migrate sniproxy and the kube helpers to NotifyInitialStatus: they seed from InitialStatus.Self and react to the (ungated) runtime Notify.SelfChange messages after that, so their initial message now carries one PeerStatus instead of a full netmap. Also drop doc comment references to LocalClient.NetMap, a method that does not exist; on-demand fetches go through other LocalAPI methods such as LocalClient.Status. Updates #12542 Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com> Change-Id: I242992a744c0ffd0be6f27e8c735aa69d5b23b5e
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
-
Node sharing and other cross-Tailnet features don't work when using custom DERP servers.
-
DERP servers only see encrypted WireGuard packets and thus are not useful for network-level debugging.
-
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
-
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.
-
A DERP server should not share an IP address with any other DERP server.
-
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.
-
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.
-
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.
-
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.
-
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.