ipn/ipnlocal: add some test accessors

Updates tailscale/corp#12990

Change-Id: I82801ac4c003d2c7e1352c514adb908dbf01be87
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

cmd/tailscaled/depaware.txt

@@ -387,7 +387,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         golang.org/x/crypto/salsa20/salsa                            from golang.org/x/crypto/nacl/box+
   LD    golang.org/x/crypto/ssh                                      from tailscale.com/ssh/tailssh+
         golang.org/x/exp/constraints                                 from github.com/dblohm7/wingoes/pe+
-        golang.org/x/exp/maps                                        from tailscale.com/wgengine/magicsock
+        golang.org/x/exp/maps                                        from tailscale.com/wgengine/magicsock+
         golang.org/x/net/bpf                                         from github.com/mdlayher/genetlink+
         golang.org/x/net/dns/dnsmessage                              from net+
         golang.org/x/net/http/httpguts                               from golang.org/x/net/http2+

ipn/ipnlocal/local.go

@@ -31,6 +31,7 @@ import (
 
 	"go4.org/mem"
 	"go4.org/netipx"
+	xmaps "golang.org/x/exp/maps"
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"tailscale.com/client/tailscale/apitype"
 	"tailscale.com/control/controlclient"
@@ -1335,6 +1336,27 @@ func (b *LocalBackend) SetControlClientGetterForTesting(newControlClient func(co
 	b.ccGen = newControlClient
 }
 
+// NodeViewByIDForTest returns the state of the node with the given ID
+// for integration tests in another repo.
+func (b *LocalBackend) NodeViewByIDForTest(id tailcfg.NodeID) (_ tailcfg.NodeView, ok bool) {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	n, ok := b.peers[id]
+	return n, ok
+}
+
+// PeersForTest returns all the current peers, sorted by Node.ID,
+// for integration tests in another repo.
+func (b *LocalBackend) PeersForTest() []tailcfg.NodeView {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	ret := xmaps.Values(b.peers)
+	slices.SortFunc(ret, func(a, b tailcfg.NodeView) int {
+		return cmpx.Compare(a.ID(), b.ID())
+	})
+	return ret
+}
+
 func (b *LocalBackend) getNewControlClientFunc() clientGen {
 	b.mu.Lock()
 	defer b.mu.Unlock()