tailcfg: add NodeCapMap

Like PeerCapMap, add a field to `tailcfg.Node` which provides
a map of Capability to raw JSON messages which are deferred to be
parsed later by the application code which cares about the specific
capabilities. This effectively allows us to prototype new behavior
without having to commit to a schema in tailcfg, and it also opens up
the possibilities to develop custom behavior in tsnet applications w/o
having to plumb through application specific data in the MapResponse.

Updates #4217

Signed-off-by: Maisem Ali <maisem@tailscale.com>

1 files changed, 18 insertions, 26 deletions

diff --git a/control/controlknobs/controlknobs.go b/control/controlknobs/controlknobs.go
index 50b0298a9..4d57b30a3 100644
--- a/control/controlknobs/controlknobs.go
+++ b/control/controlknobs/controlknobs.go
@@ -6,6 +6,7 @@
 package controlknobs
 
 import (
+	"slices"
 	"sync/atomic"
 
 	"tailscale.com/syncs"
@@ -48,39 +49,30 @@ type Knobs struct {
 
 // UpdateFromNodeAttributes updates k (if non-nil) based on the provided self
 // node attributes (Node.Capabilities).
-func (k *Knobs) UpdateFromNodeAttributes(selfNodeAttrs []tailcfg.NodeCapability) {
+func (k *Knobs) UpdateFromNodeAttributes(selfNodeAttrs []tailcfg.NodeCapability, capMap tailcfg.NodeCapMap) {
 	if k == nil {
 		return
 	}
+	has := func(attr tailcfg.NodeCapability) bool {
+		_, ok := capMap[attr]
+		return ok || slices.Contains(selfNodeAttrs, attr)
+	}
 	var (
-		keepFullWG          bool
-		disableDRPO         bool
-		disableUPnP         bool
-		randomizeClientPort bool
-		disableDeltaUpdates bool
+		keepFullWG          = has(tailcfg.NodeAttrDebugDisableWGTrim)
+		disableDRPO         = has(tailcfg.NodeAttrDebugDisableDRPO)
+		disableUPnP         = has(tailcfg.NodeAttrDisableUPnP)
+		randomizeClientPort = has(tailcfg.NodeAttrRandomizeClientPort)
+		disableDeltaUpdates = has(tailcfg.NodeAttrDisableDeltaUpdates)
 		oneCGNAT            opt.Bool
-		forceBackgroundSTUN bool
+		forceBackgroundSTUN = has(tailcfg.NodeAttrDebugForceBackgroundSTUN)
 	)
-	for _, attr := range selfNodeAttrs {
-		switch attr {
-		case tailcfg.NodeAttrDebugDisableWGTrim:
-			keepFullWG = true
-		case tailcfg.NodeAttrDebugDisableDRPO:
-			disableDRPO = true
-		case tailcfg.NodeAttrDisableUPnP:
-			disableUPnP = true
-		case tailcfg.NodeAttrRandomizeClientPort:
-			randomizeClientPort = true
-		case tailcfg.NodeAttrOneCGNATEnable:
-			oneCGNAT.Set(true)
-		case tailcfg.NodeAttrOneCGNATDisable:
-			oneCGNAT.Set(false)
-		case tailcfg.NodeAttrDebugForceBackgroundSTUN:
-			forceBackgroundSTUN = true
-		case tailcfg.NodeAttrDisableDeltaUpdates:
-			disableDeltaUpdates = true
-		}
+
+	if has(tailcfg.NodeAttrOneCGNATEnable) {
+		oneCGNAT.Set(true)
+	} else if has(tailcfg.NodeAttrOneCGNATDisable) {
+		oneCGNAT.Set(false)
 	}
+
 	k.KeepFullWGConfig.Store(keepFullWG)
 	k.DisableDRPO.Store(disableDRPO)
 	k.DisableUPnP.Store(disableUPnP)