internal/clientinfo: use default route IP as self client info

cmd/ctrld/dns_proxy.go

@@ -549,6 +549,9 @@ func (p *prog) getClientInfo(ip, mac string) *ctrld.ClientInfo {
 	} else {
 		ci.IP = ip
 		ci.Mac = p.ciTable.LookupMac(ip)
+		if ip == "127.0.0.1" || ip == "::1" {
+			ci.IP = p.ciTable.LookupIP(ci.Mac)
+		}
 	}
 	ci.Hostname = p.ciTable.LookupHostname(ci.IP, ci.Mac)
 	return ci

cmd/ctrld/prog.go

@@ -11,6 +11,7 @@ import (
 	"syscall"
 
 	"github.com/kardianos/service"
+	"tailscale.com/net/interfaces"
 
 	"github.com/Control-D-Inc/ctrld"
 	"github.com/Control-D-Inc/ctrld/internal/clientinfo"
@@ -109,7 +110,7 @@ func (p *prog) run() {
 		go uc.Ping()
 	}
 
-	p.ciTable = clientinfo.NewTable(&cfg)
+	p.ciTable = clientinfo.NewTable(&cfg, defaultRouteIP())
 	if leaseFile := p.cfg.Service.DHCPLeaseFile; leaseFile != "" {
 		mainLog.Debug().Msgf("watching custom lease file: %s", leaseFile)
 		format := ctrld.LeaseFileFormat(p.cfg.Service.DHCPLeaseFileFormat)
@@ -307,3 +308,30 @@ func errAddrInUse(err error) bool {
 	}
 	return errors.Is(opErr.Err, syscall.EADDRINUSE)
 }
+
+// defaultRouteIP returns IP string of the default route if present, prefer IPv4 over IPv6.
+func defaultRouteIP() string {
+	if dr, err := interfaces.DefaultRoute(); err == nil {
+		if netIface, err := netInterface(dr.InterfaceName); err == nil {
+			addrs, _ := netIface.Addrs()
+			do := func(v4 bool) net.IP {
+				for _, addr := range addrs {
+					if netIP, ok := addr.(*net.IPNet); ok && netIP.IP.IsPrivate() {
+						if v4 {
+							return netIP.IP.To4()
+						}
+						return netIP.IP
+					}
+				}
+				return nil
+			}
+			if ip := do(true); ip != nil {
+				return ip.String()
+			}
+			if ip := do(false); ip != nil {
+				return ip.String()
+			}
+		}
+	}
+	return ""
+}