tailcfg: add JSON unmarshal helper for view of node/peer capabilities

Many places that need to work with node/peer capabilities end up with a
something-View and need to either reimplement the helper code or make an
expensive copy. We have the machinery to easily handle this now.

Updates #cleanup

Change-Id: Ic3f55be329f0fc6c178de26b34359d0e8c6ca5fc
Signed-off-by: Adrian Dewhurst <adrian@tailscale.com>

cmd/sniproxy/sniproxy.go

@@ -157,10 +157,8 @@ func run(ctx context.Context, ts *tsnet.Server, wgPort int, hostname string, pro
 
 		// NetMap contains app-connector configuration
 		if nm := msg.NetMap; nm != nil && nm.SelfNode.Valid() {
-			sn := nm.SelfNode.AsStruct()
-
 			var c appctype.AppConnectorConfig
-			nmConf, err := tailcfg.UnmarshalNodeCapJSON[appctype.AppConnectorConfig](sn.CapMap, configCapKey)
+			nmConf, err := tailcfg.UnmarshalNodeCapViewJSON[appctype.AppConnectorConfig](nm.SelfNode.CapMap(), configCapKey)
 			if err != nil {
 				log.Printf("failed to read app connector configuration from coordination server: %v", err)
 			} else if len(nmConf) > 0 {

ipn/ipnlocal/local.go

@@ -4463,10 +4463,7 @@ func (b *LocalBackend) reconfigAppConnectorLocked(nm *netmap.NetworkMap, prefs i
 		return
 	}
 
-	// TODO(raggi): rework the view infrastructure so the large deep clone is no
-	// longer required
-	sn := nm.SelfNode.AsStruct()
-	attrs, err := tailcfg.UnmarshalNodeCapJSON[appctype.AppConnectorAttr](sn.CapMap, appConnectorCapName)
+	attrs, err := tailcfg.UnmarshalNodeCapViewJSON[appctype.AppConnectorAttr](nm.SelfNode.CapMap(), appConnectorCapName)
 	if err != nil {
 		b.logf("[unexpected] error parsing app connector mapcap: %v", err)
 		return

tailcfg/tailcfg.go

@@ -25,6 +25,7 @@ import (
 	"tailscale.com/types/opt"
 	"tailscale.com/types/structs"
 	"tailscale.com/types/tkatype"
+	"tailscale.com/types/views"
 	"tailscale.com/util/dnsname"
 	"tailscale.com/util/slicesx"
 	"tailscale.com/util/vizerror"
@@ -1547,12 +1548,19 @@ func (c NodeCapMap) Equal(c2 NodeCapMap) bool {
 // If cap does not exist in cm, it returns (nil, nil).
 // It returns an error if the values cannot be unmarshaled into the provided type.
 func UnmarshalNodeCapJSON[T any](cm NodeCapMap, cap NodeCapability) ([]T, error) {
-	vals, ok := cm[cap]
+	return UnmarshalNodeCapViewJSON[T](views.MapSliceOf(cm), cap)
+}
+
+// UnmarshalNodeCapViewJSON unmarshals each JSON value in cm.Get(cap) as T.
+// If cap does not exist in cm, it returns (nil, nil).
+// It returns an error if the values cannot be unmarshaled into the provided type.
+func UnmarshalNodeCapViewJSON[T any](cm views.MapSlice[NodeCapability, RawMessage], cap NodeCapability) ([]T, error) {
+	vals, ok := cm.GetOk(cap)
 	if !ok {
 		return nil, nil
 	}
-	out := make([]T, 0, len(vals))
-	for _, v := range vals {
+	out := make([]T, 0, vals.Len())
+	for _, v := range vals.All() {
 		var t T
 		if err := json.Unmarshal([]byte(v), &t); err != nil {
 			return nil, err
@@ -1582,12 +1590,19 @@ type PeerCapMap map[PeerCapability][]RawMessage
 // If cap does not exist in cm, it returns (nil, nil).
 // It returns an error if the values cannot be unmarshaled into the provided type.
 func UnmarshalCapJSON[T any](cm PeerCapMap, cap PeerCapability) ([]T, error) {
-	vals, ok := cm[cap]
+	return UnmarshalCapViewJSON[T](views.MapSliceOf(cm), cap)
+}
+
+// UnmarshalCapViewJSON unmarshals each JSON value in cm.Get(cap) as T.
+// If cap does not exist in cm, it returns (nil, nil).
+// It returns an error if the values cannot be unmarshaled into the provided type.
+func UnmarshalCapViewJSON[T any](cm views.MapSlice[PeerCapability, RawMessage], cap PeerCapability) ([]T, error) {
+	vals, ok := cm.GetOk(cap)
 	if !ok {
 		return nil, nil
 	}
-	out := make([]T, 0, len(vals))
-	for _, v := range vals {
+	out := make([]T, 0, vals.Len())
+	for _, v := range vals.All() {
 		var t T
 		if err := json.Unmarshal([]byte(v), &t); err != nil {
 			return nil, err

types/netmap/netmap.go

@@ -115,7 +115,7 @@ func (nm *NetworkMap) GetVIPServiceIPMap() tailcfg.ServiceIPMappings {
 		return nil
 	}
 
-	ipMaps, err := tailcfg.UnmarshalNodeCapJSON[tailcfg.ServiceIPMappings](nm.SelfNode.CapMap().AsMap(), tailcfg.NodeAttrServiceHost)
+	ipMaps, err := tailcfg.UnmarshalNodeCapViewJSON[tailcfg.ServiceIPMappings](nm.SelfNode.CapMap(), tailcfg.NodeAttrServiceHost)
 	if len(ipMaps) != 1 || err != nil {
 		return nil
 	}