add basic lla

internal/aghnet/net.go

@@ -7,6 +7,7 @@ import (
 	"fmt"
 	"io"
 	"net"
+	"net/netip"
 	"syscall"
 
 	"github.com/AdguardTeam/AdGuardHome/internal/aghos"
@@ -31,6 +32,12 @@ var (
 // the IP being static is available.
 const ErrNoStaticIPInfo errors.Error = "no information about static ip"
 
+// IPv4Localhost returns 127.0.0.1, which returns true for [netip.Addr.Is4].
+func IPv4Localhost() (ip netip.Addr) { return netip.AddrFrom4([4]byte{0: 127, 3: 1}) }
+
+// IPv6Localhost returns ::1, which returns true for [netip.Addr.Is6].
+func IPv6Localhost() (ip netip.Addr) { return netip.AddrFrom16([16]byte{15: 1}) }
+
 // IfaceHasStaticIP checks if interface is configured to have static IP address.
 // If it can't give a definitive answer, it returns false and an error for which
 // errors.Is(err, ErrNoStaticIPInfo) is true.
@@ -47,26 +54,31 @@ func IfaceSetStaticIP(ifaceName string) (err error) {
 //
 // TODO(e.burkov):  Investigate if the gateway address may be fetched in another
 // way since not every machine has the software installed.
-func GatewayIP(ifaceName string) (ip net.IP) {
+func GatewayIP(ifaceName string) (ip netip.Addr) {
 	code, out, err := aghosRunCommand("ip", "route", "show", "dev", ifaceName)
 	if err != nil {
 		log.Debug("%s", err)
 
-		return nil
+		return ip
 	} else if code != 0 {
 		log.Debug("fetching gateway ip: unexpected exit code: %d", code)
 
-		return nil
+		return ip
 	}
 
 	fields := bytes.Fields(out)
 	// The meaningful "ip route" command output should contain the word
 	// "default" at first field and default gateway IP address at third field.
 	if len(fields) < 3 || string(fields[0]) != "default" {
-		return nil
+		return ip
 	}
 
-	return net.ParseIP(string(fields[2]))
+	ip, err = netip.ParseAddr(string(fields[2]))
+	if err != nil {
+		return netip.Addr{}
+	}
+
+	return ip
 }
 
 // CanBindPrivilegedPorts checks if current process can bind to privileged
@@ -78,9 +90,9 @@ func CanBindPrivilegedPorts() (can bool, err error) {
 // NetInterface represents an entry of network interfaces map.
 type NetInterface struct {
 	// Addresses are the network interface addresses.
-	Addresses []net.IP `json:"ip_addresses,omitempty"`
+	Addresses []netip.Addr `json:"ip_addresses,omitempty"`
 	// Subnets are the IP networks for this network interface.
-	Subnets      []*net.IPNet     `json:"-"`
+	Subnets      []netip.Prefix   `json:"-"`
 	Name         string           `json:"name"`
 	HardwareAddr net.HardwareAddr `json:"hardware_address"`
 	Flags        net.Flags        `json:"flags"`
@@ -101,57 +113,78 @@ func (iface NetInterface) MarshalJSON() ([]byte, error) {
 	})
 }
 
+func NetInterfaceFrom(iface *net.Interface) (niface *NetInterface, err error) {
+	niface = &NetInterface{
+		Name:         iface.Name,
+		HardwareAddr: iface.HardwareAddr,
+		Flags:        iface.Flags,
+		MTU:          iface.MTU,
+	}
+
+	addrs, err := iface.Addrs()
+	if err != nil {
+		return nil, fmt.Errorf("failed to get addresses for interface %s: %w", iface.Name, err)
+	}
+
+	// Collect network interface addresses.
+	for _, addr := range addrs {
+		n, ok := addr.(*net.IPNet)
+		if !ok {
+			// Should be net.IPNet, this is weird.
+			return nil, fmt.Errorf("expected %[2]s to be %[1]T, got %[2]T", n, addr)
+		} else if ip4 := n.IP.To4(); ip4 != nil {
+			n.IP = ip4
+		}
+
+		ip, ok := netip.AddrFromSlice(n.IP)
+		if !ok {
+			return nil, fmt.Errorf("bad address %s", n.IP)
+		}
+
+		ip = ip.WithZone(iface.Name)
+
+		// Ignore link-local IPv4.
+		//
+		// TODO(e.burkov):  !! or not??
+		if ip.Is4() && ip.IsLinkLocalUnicast() {
+			continue
+		}
+
+		ones, _ := n.Mask.Size()
+		p := netip.PrefixFrom(ip, ones)
+
+		niface.Addresses = append(niface.Addresses, ip)
+		niface.Subnets = append(niface.Subnets, p)
+	}
+
+	return niface, nil
+}
+
 // GetValidNetInterfacesForWeb returns interfaces that are eligible for DNS and
 // WEB only we do not return link-local addresses here.
 //
 // TODO(e.burkov):  Can't properly test the function since it's nontrivial to
 // substitute net.Interface.Addrs and the net.InterfaceAddrs can't be used.
-func GetValidNetInterfacesForWeb() (netIfaces []*NetInterface, err error) {
+func GetValidNetInterfacesForWeb() (nifaces []*NetInterface, err error) {
 	ifaces, err := net.Interfaces()
 	if err != nil {
-		return nil, fmt.Errorf("couldn't get interfaces: %w", err)
+		return nil, fmt.Errorf("getting interfaces: %w", err)
 	} else if len(ifaces) == 0 {
-		return nil, errors.Error("couldn't find any legible interface")
+		return nil, errors.Error("no legible interfaces")
 	}
 
-	for _, iface := range ifaces {
-		var addrs []net.Addr
-		addrs, err = iface.Addrs()
+	for i := range ifaces {
+		var niface *NetInterface
+		niface, err = NetInterfaceFrom(&ifaces[i])
 		if err != nil {
-			return nil, fmt.Errorf("failed to get addresses for interface %s: %w", iface.Name, err)
-		}
-
-		netIface := &NetInterface{
-			MTU:          iface.MTU,
-			Name:         iface.Name,
-			HardwareAddr: iface.HardwareAddr,
-			Flags:        iface.Flags,
-		}
-
-		// Collect network interface addresses.
-		for _, addr := range addrs {
-			ipNet, ok := addr.(*net.IPNet)
-			if !ok {
-				// Should be net.IPNet, this is weird.
-				return nil, fmt.Errorf("got %s that is not net.IPNet, it is %T", addr, addr)
-			}
-
-			// Ignore link-local.
-			if ipNet.IP.IsLinkLocalUnicast() {
-				continue
-			}
-
-			netIface.Addresses = append(netIface.Addresses, ipNet.IP)
-			netIface.Subnets = append(netIface.Subnets, ipNet)
-		}
-
-		// Discard interfaces with no addresses.
-		if len(netIface.Addresses) != 0 {
-			netIfaces = append(netIfaces, netIface)
+			return nil, err
+		} else if len(niface.Addresses) != 0 {
+			// Discard interfaces with no addresses.
+			nifaces = append(nifaces, niface)
 		}
 	}
 
-	return netIfaces, nil
+	return nifaces, nil
 }
 
 // InterfaceByIP returns the name of the interface bound to ip.
@@ -160,7 +193,7 @@ func GetValidNetInterfacesForWeb() (netIfaces []*NetInterface, err error) {
 // IP address can be shared by multiple interfaces in some configurations.
 //
 // TODO(e.burkov):  See TODO on GetValidNetInterfacesForWeb.
-func InterfaceByIP(ip net.IP) (ifaceName string) {
+func InterfaceByIP(ip netip.Addr) (ifaceName string) {
 	ifaces, err := GetValidNetInterfacesForWeb()
 	if err != nil {
 		return ""
@@ -168,7 +201,7 @@ func InterfaceByIP(ip net.IP) (ifaceName string) {
 
 	for _, iface := range ifaces {
 		for _, addr := range iface.Addresses {
-			if ip.Equal(addr) {
+			if ip == addr {
 				return iface.Name
 			}
 		}
@@ -177,15 +210,16 @@ func InterfaceByIP(ip net.IP) (ifaceName string) {
 	return ""
 }
 
-// GetSubnet returns pointer to net.IPNet for the specified interface or nil if
+// GetSubnet returns the subnet corresponding to the interface of zero prefix if
 // the search fails.
 //
 // TODO(e.burkov):  See TODO on GetValidNetInterfacesForWeb.
-func GetSubnet(ifaceName string) *net.IPNet {
+func GetSubnet(ifaceName string) (p netip.Prefix) {
 	netIfaces, err := GetValidNetInterfacesForWeb()
 	if err != nil {
 		log.Error("Could not get network interfaces info: %v", err)
-		return nil
+
+		return p
 	}
 
 	for _, netIface := range netIfaces {
@@ -194,14 +228,14 @@ func GetSubnet(ifaceName string) *net.IPNet {
 		}
 	}
 
-	return nil
+	return p
 }
 
 // CheckPort checks if the port is available for binding.  network is expected
 // to be one of "udp" and "tcp".
-func CheckPort(network string, ip net.IP, port int) (err error) {
+func CheckPort(network string, ipp netip.AddrPort) (err error) {
 	var c io.Closer
-	addr := netutil.IPPort{IP: ip, Port: port}.String()
+	addr := ipp.String()
 	switch network {
 	case "tcp":
 		c, err = net.Listen(network, addr)