External NAT IP mapping support (#487)

* External NAT IP mapping support

* Ignore blacklisted interfaces, even if in user specified in  mapping

.gitignore

@@ -10,4 +10,5 @@ infrastructure_files/management.json
 infrastructure_files/docker-compose.yml
 *.syso
 client/.distfiles/
-infrastructure_files/setup.env
+infrastructure_files/setup.env
+.vscode

client/internal/config.go

@@ -3,6 +3,9 @@ package internal
 import (
 	"context"
 	"fmt"
+	"net/url"
+	"os"
+
 	"github.com/netbirdio/netbird/client/ssh"
 	"github.com/netbirdio/netbird/iface"
 	mgm "github.com/netbirdio/netbird/management/client"
@@ -11,8 +14,6 @@ import (
 	"golang.zx2c4.com/wireguard/wgctrl/wgtypes"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
-	"net/url"
-	"os"
 )
 
 var managementURLDefault *url.URL
@@ -40,7 +41,24 @@ type Config struct {
 	WgPort         int
 	IFaceBlackList []string
 	// SSHKey is a private SSH key in a PEM format
-	SSHKey string
+	SSHKey         string
+
+	// ExternalIP mappings, if different than the host interface IP
+	//
+	//   External IP must not be behind a CGNAT and port-forwarding for incoming UDP packets from WgPort on ExternalIP
+	//   to WgPort on host interface IP must be present. This can take form of single port-forwarding rule, 1:1 DNAT
+	//   mapping ExternalIP to host interface IP, or a NAT DMZ to host interface IP.
+	//
+	//   A single mapping will take the form of: external[/internal]
+	//    external (required): either the external IP address or "stun" to use STUN to determine the external IP address
+	//    internal (optional): either the internal/interface IP address or an interface name
+	//
+	//   examples:
+	//      "12.34.56.78"          => all interfaces IPs will be mapped to external IP of 12.34.56.78
+	//      "12.34.56.78/eth0"     => IPv4 assigned to interface eth0 will be mapped to external IP of 12.34.56.78
+	//      "12.34.56.78/10.1.2.3" => interface IP 10.1.2.3 will be mapped to external IP of 12.34.56.78
+
+	NATExternalIPs []string
 }
 
 // createNewConfig creates a new config generating a new Wireguard key and saving to file

client/internal/connect.go

@@ -3,11 +3,12 @@ package internal
 import (
 	"context"
 	"fmt"
-	"github.com/netbirdio/netbird/client/ssh"
-	nbStatus "github.com/netbirdio/netbird/client/status"
 	"strings"
 	"time"
 
+	"github.com/netbirdio/netbird/client/ssh"
+	nbStatus "github.com/netbirdio/netbird/client/status"
+
 	"github.com/netbirdio/netbird/client/system"
 
 	"github.com/netbirdio/netbird/iface"
@@ -190,6 +191,7 @@ func createEngineConfig(key wgtypes.Key, config *Config, peerConfig *mgmProto.Pe
 		WgPrivateKey:   key,
 		WgPort:         config.WgPort,
 		SSHKey:         []byte(config.SSHKey),
+		NATExternalIPs:	config.NATExternalIPs,
 	}
 
 	if config.PreSharedKey != "" {

client/internal/engine.go

@@ -3,12 +3,6 @@ package internal
 import (
 	"context"
 	"fmt"
-	"github.com/netbirdio/netbird/client/internal/dns"
-	"github.com/netbirdio/netbird/client/internal/routemanager"
-	nbssh "github.com/netbirdio/netbird/client/ssh"
-	nbstatus "github.com/netbirdio/netbird/client/status"
-	nbdns "github.com/netbirdio/netbird/dns"
-	"github.com/netbirdio/netbird/route"
 	"math/rand"
 	"net"
 	"net/netip"
@@ -18,6 +12,13 @@ import (
 	"sync"
 	"time"
 
+	"github.com/netbirdio/netbird/client/internal/dns"
+	"github.com/netbirdio/netbird/client/internal/routemanager"
+	nbssh "github.com/netbirdio/netbird/client/ssh"
+	nbstatus "github.com/netbirdio/netbird/client/status"
+	nbdns "github.com/netbirdio/netbird/dns"
+	"github.com/netbirdio/netbird/route"
+
 	"github.com/netbirdio/netbird/client/internal/peer"
 	"github.com/netbirdio/netbird/client/internal/proxy"
 	"github.com/netbirdio/netbird/iface"
@@ -66,6 +67,8 @@ type EngineConfig struct {
 
 	// SSHKey is a private SSH key in a PEM format
 	SSHKey []byte
+
+	NATExternalIPs []string
 }
 
 // Engine is a mechanism responsible for reacting on Signal and Management stream events and managing connections to the remote peers.
@@ -825,6 +828,7 @@ func (e Engine) createPeerConn(pubKey string, allowedIPs string) (*peer.Conn, er
 		UDPMuxSrflx:        e.udpMuxSrflx,
 		ProxyConfig:        proxyConfig,
 		LocalWgPort:        e.config.WgPort,
+		NATExternalIPs:		e.parseNATExternalIPMappings(),
 	}
 
 	peerConn, err := peer.NewConn(config, e.statusRecorder)
@@ -918,3 +922,77 @@ func (e *Engine) receiveSignalEvents() {
 
 	e.signal.WaitStreamConnected()
 }
+
+func (e* Engine) parseNATExternalIPMappings() []string {
+	var mappedIPs []string
+	var ignoredIFaces = make(map[string]interface{})
+	for _, iFace := range(e.config.IFaceBlackList) {
+		ignoredIFaces[iFace] = nil
+	}
+	for _, mapping := range e.config.NATExternalIPs {
+		var external, internal string
+		var externalIP, internalIP net.IP
+		var err error
+		split := strings.Split(mapping, "/")
+		if len(split) > 2 {
+			log.Warnf("ignoring invalid external mapping '%s', too many delimiters", mapping)
+			break
+		}
+		if len(split) > 1 {
+			internal = split[1]
+			internalIP = net.ParseIP(internal)
+			if internalIP == nil {
+				// not a properly formatted IP address, maybe it's interface name?
+				if _, present := ignoredIFaces[internal]; present {
+					log.Warnf("internal interface '%s' in blacklist, ignoring external mapping '%s'", internal, mapping)
+					break
+				}
+				internalIP, err = findIPFromInterfaceName(internal)
+				if err != nil {
+					log.Warnf("error finding interface IP for interface '%s', ignoring external mapping '%s': %v", internal, mapping, err)
+					break
+				}
+			}
+		}
+		external = split[0]
+		externalIP = net.ParseIP(external)
+		if externalIP == nil {
+			log.Warnf("invalid external IP, ignoring external IP mapping '%s'", mapping)
+			break
+		}
+		if externalIP != nil {
+			mappedIP := externalIP.String()
+			if internalIP != nil {
+				mappedIP = mappedIP + "/" + internalIP.String()
+			}
+			mappedIPs = append(mappedIPs, mappedIP)
+			log.Infof("parsed external IP mapping of '%s' as '%s'", mapping, mappedIP)
+		}
+	}
+	if len(mappedIPs) != len(e.config.NATExternalIPs) {
+		log.Warnf("one or more external IP mappings failed to parse, ignoring all mappings")
+		return nil
+	}
+	return mappedIPs
+}
+
+func findIPFromInterfaceName(ifaceName string) (net.IP, error) {
+    iface, err := net.InterfaceByName(ifaceName)
+	if err != nil {
+        return nil, err
+    }
+    return findIPFromInterface(iface)
+}
+
+func findIPFromInterface(iface *net.Interface) (net.IP, error) {
+    ifaceAddrs, err := iface.Addrs()
+	if err != nil {
+        return nil, err
+    }
+    for _, addr := range ifaceAddrs {
+        if ipv4Addr := addr.(*net.IPNet).IP.To4(); ipv4Addr != nil {
+			return ipv4Addr, nil
+        }
+    }
+	return nil, fmt.Errorf("interface %s don't have an ipv4 address", iface.Name)
+}

client/internal/peer/conn.go

@@ -2,18 +2,18 @@ package peer
 
 import (
 	"context"
-	nbStatus "github.com/netbirdio/netbird/client/status"
-	"github.com/netbirdio/netbird/client/system"
-	"github.com/netbirdio/netbird/iface"
-	"golang.zx2c4.com/wireguard/wgctrl"
 	"net"
 	"strings"
 	"sync"
 	"time"
 
 	"github.com/netbirdio/netbird/client/internal/proxy"
+	nbStatus "github.com/netbirdio/netbird/client/status"
+	"github.com/netbirdio/netbird/client/system"
+	"github.com/netbirdio/netbird/iface"
 	"github.com/pion/ice/v2"
 	log "github.com/sirupsen/logrus"
+	"golang.zx2c4.com/wireguard/wgctrl"
 )
 
 // ConnConfig is a peer Connection configuration
@@ -39,6 +39,8 @@ type ConnConfig struct {
 	UDPMuxSrflx ice.UniversalUDPMux
 
 	LocalWgPort int
+
+	NATExternalIPs []string
 }
 
 // OfferAnswer represents a session establishment offer or answer
@@ -152,6 +154,7 @@ func (conn *Conn) reCreateAgent() error {
 		InterfaceFilter:  interfaceFilter(conn.config.InterfaceBlackList),
 		UDPMux:           conn.config.UDPMux,
 		UDPMuxSrflx:      conn.config.UDPMuxSrflx,
+		NAT1To1IPs:       conn.config.NATExternalIPs,
 	})
 	if err != nil {
 		return err
@@ -284,7 +287,7 @@ func (conn *Conn) Open() error {
 		host, _, _ := net.SplitHostPort(remoteConn.LocalAddr().String())
 		rhost, _, _ := net.SplitHostPort(remoteConn.RemoteAddr().String())
 		// direct Wireguard connection
-		log.Infof("directly connected to peer %s [laddr <-> raddr] [%s:%d <-> %s:%d]", conn.config.Key, host, iface.DefaultWgPort, rhost, iface.DefaultWgPort)
+		log.Infof("directly connected to peer %s [laddr <-> raddr] [%s:%d <-> %s:%d]", conn.config.Key, host, conn.config.LocalWgPort, rhost, remoteWgPort)
 	} else {
 		log.Infof("connected to peer %s [laddr <-> raddr] [%s <-> %s]", conn.config.Key, remoteConn.LocalAddr().String(), remoteConn.RemoteAddr().String())
 	}
@@ -448,6 +451,7 @@ func (conn *Conn) SetSignalCandidate(handler func(candidate ice.Candidate) error
 // and then signals them to the remote peer
 func (conn *Conn) onICECandidate(candidate ice.Candidate) {
 	if candidate != nil {
+		// TODO: reported port is incorrect for CandidateTypeHost, makes understanding ICE use via logs confusing as port is ignored
 		log.Debugf("discovered local candidate %s", candidate.String())
 		go func() {
 			err := conn.signalCandidate(candidate)