macOS: repair network recovery and improve diagnostics

cmd/cli/network_source_error_test.go

@@ -0,0 +1,32 @@
+package cli
+
+import (
+	"errors"
+	"net"
+	"testing"
+
+	ctrld "github.com/Control-D-Inc/ctrld"
+	"tailscale.com/net/netmon"
+)
+
+func TestSourceReadFailureDefersAcceptedWrites(t *testing.T) {
+	sourceTestGlobals(t)
+	dnsIntercept = false
+	oldCurrent, oldRead := networkChangeCurrentStateFn, readNetworkSourceStateFn
+	t.Cleanup(func() { networkChangeCurrentStateFn, readNetworkSourceStateFn = oldCurrent, oldRead })
+	major := sourceTestState("en0", true, "192.0.2.10/24")
+	networkChangeCurrentStateFn = func(*netmon.ChangeDelta) *netmon.State { return major }
+	readNetworkSourceStateFn = func() (*netmon.State, error) { return nil, errors.New("read failed") }
+	ctrld.SetDefaultLocalIPv4(net.ParseIP("192.0.2.1"))
+	ctrld.SetDefaultLocalIPv6(nil)
+	p := &prog{cfg: &ctrld.Config{}, networkSourceEpoch: major}
+	calls := 0
+	networkChangeReconcileFn = func(*prog, uint64) { calls++ }
+	p.handleNetworkChange(&netmon.ChangeDelta{
+		Monitor: netmon.NewStatic(),
+		Old:     sourceTestState("en0", true, "192.0.2.1/24"), New: major,
+	}, true)
+	if calls != 1 || !ctrld.GetDefaultLocalIPv4().Equal(net.ParseIP("192.0.2.1")) {
+		t.Fatal("unknown source validity changed a binding or skipped accepted recovery")
+	}
+}