DNS forwarder and common ebpf loader (#1083)

In case the 53 UDP port is not an option to bind then we hijack the DNS traffic with eBPF, and we forward the traffic to the listener on a custom port. With this implementation, we should be able to listen to DNS queries on any address and still set the local host system to send queries to the custom address on port 53.

Because we tried to attach multiple XDP programs to the same interface, I did a refactor in the WG traffic forward code also.

client/internal/dns/service_listener.go

@@ -11,6 +11,9 @@ import (
 
 	"github.com/miekg/dns"
 	log "github.com/sirupsen/logrus"
+
+	"github.com/netbirdio/netbird/client/internal/ebpf"
+	ebpfMgr "github.com/netbirdio/netbird/client/internal/ebpf/manager"
 )
 
 const (
@@ -24,10 +27,11 @@ type serviceViaListener struct {
 	dnsMux            *dns.ServeMux
 	customAddr        *netip.AddrPort
 	server            *dns.Server
-	runtimeIP         string
-	runtimePort       int
+	listenIP          string
+	listenPort        int
 	listenerIsRunning bool
 	listenerFlagLock  sync.Mutex
+	ebpfService       ebpfMgr.Manager
 }
 
 func newServiceViaListener(wgIface WGIface, customAddr *netip.AddrPort) *serviceViaListener {
@@ -43,6 +47,7 @@ func newServiceViaListener(wgIface WGIface, customAddr *netip.AddrPort) *service
 			UDPSize: 65535,
 		},
 	}
+
 	return s
 }
 
@@ -55,13 +60,21 @@ func (s *serviceViaListener) Listen() error {
 	}
 
 	var err error
-	s.runtimeIP, s.runtimePort, err = s.evalRuntimeAddress()
+	s.listenIP, s.listenPort, err = s.evalListenAddress()
 	if err != nil {
 		log.Errorf("failed to eval runtime address: %s", err)
 		return err
 	}
-	s.server.Addr = fmt.Sprintf("%s:%d", s.runtimeIP, s.runtimePort)
+	s.server.Addr = fmt.Sprintf("%s:%d", s.listenIP, s.listenPort)
 
+	if s.shouldApplyPortFwd() {
+		s.ebpfService = ebpf.GetEbpfManagerInstance()
+		err = s.ebpfService.LoadDNSFwd(s.listenIP, s.listenPort)
+		if err != nil {
+			log.Warnf("failed to load DNS port forwarder, custom port may not work well on some Linux operating systems: %s", err)
+			s.ebpfService = nil
+		}
+	}
 	log.Debugf("starting dns on %s", s.server.Addr)
 	go func() {
 		s.setListenerStatus(true)
@@ -69,9 +82,10 @@ func (s *serviceViaListener) Listen() error {
 
 		err := s.server.ListenAndServe()
 		if err != nil {
-			log.Errorf("dns server running with %d port returned an error: %v. Will not retry", s.runtimePort, err)
+			log.Errorf("dns server running with %d port returned an error: %v. Will not retry", s.listenPort, err)
 		}
 	}()
+
 	return nil
 }
 
@@ -90,6 +104,13 @@ func (s *serviceViaListener) Stop() {
 	if err != nil {
 		log.Errorf("stopping dns server listener returned an error: %v", err)
 	}
+
+	if s.ebpfService != nil {
+		err = s.ebpfService.FreeDNSFwd()
+		if err != nil {
+			log.Errorf("stopping traffic forwarder returned an error: %v", err)
+		}
+	}
 }
 
 func (s *serviceViaListener) RegisterMux(pattern string, handler dns.Handler) {
@@ -101,11 +122,18 @@ func (s *serviceViaListener) DeregisterMux(pattern string) {
 }
 
 func (s *serviceViaListener) RuntimePort() int {
-	return s.runtimePort
+	s.listenerFlagLock.Lock()
+	defer s.listenerFlagLock.Unlock()
+
+	if s.ebpfService != nil {
+		return defaultPort
+	} else {
+		return s.listenPort
+	}
 }
 
 func (s *serviceViaListener) RuntimeIP() string {
-	return s.runtimeIP
+	return s.listenIP
 }
 
 func (s *serviceViaListener) setListenerStatus(running bool) {
@@ -136,10 +164,30 @@ func (s *serviceViaListener) getFirstListenerAvailable() (string, int, error) {
 	return "", 0, fmt.Errorf("unable to find an unused ip and port combination. IPs tested: %v and ports %v", ips, ports)
 }
 
-func (s *serviceViaListener) evalRuntimeAddress() (string, int, error) {
+func (s *serviceViaListener) evalListenAddress() (string, int, error) {
 	if s.customAddr != nil {
 		return s.customAddr.Addr().String(), int(s.customAddr.Port()), nil
 	}
 
 	return s.getFirstListenerAvailable()
 }
+
+// shouldApplyPortFwd decides whether to apply eBPF program to capture DNS traffic on port 53.
+// This is needed because on some operating systems if we start a DNS server not on a default port 53, the domain name
+// resolution won't work.
+// So, in case we are running on Linux and picked a non-default port (53) we should fall back to the eBPF solution that will capture
+// traffic on port 53 and forward it to a local DNS server running on 5053.
+func (s *serviceViaListener) shouldApplyPortFwd() bool {
+	if runtime.GOOS != "linux" {
+		return false
+	}
+
+	if s.customAddr != nil {
+		return false
+	}
+
+	if s.listenPort == defaultPort {
+		return false
+	}
+	return true
+}

client/internal/ebpf/ebpf/bpf_bpfeb.go

@@ -54,13 +54,16 @@ type bpfSpecs struct {
 //
 // It can be passed ebpf.CollectionSpec.Assign.
 type bpfProgramSpecs struct {
-	NbWgProxy *ebpf.ProgramSpec `ebpf:"nb_wg_proxy"`
+	NbXdpProg *ebpf.ProgramSpec `ebpf:"nb_xdp_prog"`
 }
 
 // bpfMapSpecs contains maps before they are loaded into the kernel.
 //
 // It can be passed ebpf.CollectionSpec.Assign.
 type bpfMapSpecs struct {
+	NbFeatures           *ebpf.MapSpec `ebpf:"nb_features"`
+	NbMapDnsIp           *ebpf.MapSpec `ebpf:"nb_map_dns_ip"`
+	NbMapDnsPort         *ebpf.MapSpec `ebpf:"nb_map_dns_port"`
 	NbWgProxySettingsMap *ebpf.MapSpec `ebpf:"nb_wg_proxy_settings_map"`
 }
 
@@ -83,11 +86,17 @@ func (o *bpfObjects) Close() error {
 //
 // It can be passed to loadBpfObjects or ebpf.CollectionSpec.LoadAndAssign.
 type bpfMaps struct {
+	NbFeatures           *ebpf.Map `ebpf:"nb_features"`
+	NbMapDnsIp           *ebpf.Map `ebpf:"nb_map_dns_ip"`
+	NbMapDnsPort         *ebpf.Map `ebpf:"nb_map_dns_port"`
 	NbWgProxySettingsMap *ebpf.Map `ebpf:"nb_wg_proxy_settings_map"`
 }
 
 func (m *bpfMaps) Close() error {
 	return _BpfClose(
+		m.NbFeatures,
+		m.NbMapDnsIp,
+		m.NbMapDnsPort,
 		m.NbWgProxySettingsMap,
 	)
 }
@@ -96,12 +105,12 @@ func (m *bpfMaps) Close() error {
 //
 // It can be passed to loadBpfObjects or ebpf.CollectionSpec.LoadAndAssign.
 type bpfPrograms struct {
-	NbWgProxy *ebpf.Program `ebpf:"nb_wg_proxy"`
+	NbXdpProg *ebpf.Program `ebpf:"nb_xdp_prog"`
 }
 
 func (p *bpfPrograms) Close() error {
 	return _BpfClose(
-		p.NbWgProxy,
+		p.NbXdpProg,
 	)
 }
 

client/internal/ebpf/ebpf/bpf_bpfel.go

@@ -54,13 +54,16 @@ type bpfSpecs struct {
 //
 // It can be passed ebpf.CollectionSpec.Assign.
 type bpfProgramSpecs struct {
-	NbWgProxy *ebpf.ProgramSpec `ebpf:"nb_wg_proxy"`
+	NbXdpProg *ebpf.ProgramSpec `ebpf:"nb_xdp_prog"`
 }
 
 // bpfMapSpecs contains maps before they are loaded into the kernel.
 //
 // It can be passed ebpf.CollectionSpec.Assign.
 type bpfMapSpecs struct {
+	NbFeatures           *ebpf.MapSpec `ebpf:"nb_features"`
+	NbMapDnsIp           *ebpf.MapSpec `ebpf:"nb_map_dns_ip"`
+	NbMapDnsPort         *ebpf.MapSpec `ebpf:"nb_map_dns_port"`
 	NbWgProxySettingsMap *ebpf.MapSpec `ebpf:"nb_wg_proxy_settings_map"`
 }
 
@@ -83,11 +86,17 @@ func (o *bpfObjects) Close() error {
 //
 // It can be passed to loadBpfObjects or ebpf.CollectionSpec.LoadAndAssign.
 type bpfMaps struct {
+	NbFeatures           *ebpf.Map `ebpf:"nb_features"`
+	NbMapDnsIp           *ebpf.Map `ebpf:"nb_map_dns_ip"`
+	NbMapDnsPort         *ebpf.Map `ebpf:"nb_map_dns_port"`
 	NbWgProxySettingsMap *ebpf.Map `ebpf:"nb_wg_proxy_settings_map"`
 }
 
 func (m *bpfMaps) Close() error {
 	return _BpfClose(
+		m.NbFeatures,
+		m.NbMapDnsIp,
+		m.NbMapDnsPort,
 		m.NbWgProxySettingsMap,
 	)
 }
@@ -96,12 +105,12 @@ func (m *bpfMaps) Close() error {
 //
 // It can be passed to loadBpfObjects or ebpf.CollectionSpec.LoadAndAssign.
 type bpfPrograms struct {
-	NbWgProxy *ebpf.Program `ebpf:"nb_wg_proxy"`
+	NbXdpProg *ebpf.Program `ebpf:"nb_xdp_prog"`
 }
 
 func (p *bpfPrograms) Close() error {
 	return _BpfClose(
-		p.NbWgProxy,
+		p.NbXdpProg,
 	)
 }
 

client/internal/ebpf/ebpf/dns_fwd_linux.go

@@ -0,0 +1,51 @@
+package ebpf
+
+import (
+	"encoding/binary"
+	"net"
+
+	log "github.com/sirupsen/logrus"
+)
+
+const (
+	mapKeyDNSIP   uint32 = 0
+	mapKeyDNSPort uint32 = 1
+)
+
+func (tf *GeneralManager) LoadDNSFwd(ip string, dnsPort int) error {
+	log.Debugf("load ebpf DNS forwarder: address: %s:%d", ip, dnsPort)
+	tf.lock.Lock()
+	defer tf.lock.Unlock()
+
+	err := tf.loadXdp()
+	if err != nil {
+		return err
+	}
+
+	err = tf.bpfObjs.NbMapDnsIp.Put(mapKeyDNSIP, ip2int(ip))
+	if err != nil {
+		return err
+	}
+
+	err = tf.bpfObjs.NbMapDnsPort.Put(mapKeyDNSPort, uint16(dnsPort))
+	if err != nil {
+		return err
+	}
+
+	tf.setFeatureFlag(featureFlagDnsForwarder)
+	err = tf.bpfObjs.NbFeatures.Put(mapKeyFeatures, tf.featureFlags)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+func (tf *GeneralManager) FreeDNSFwd() error {
+	log.Debugf("free ebpf DNS forwarder")
+	return tf.unsetFeatureFlag(featureFlagDnsForwarder)
+}
+
+func ip2int(ipString string) uint32 {
+	ip := net.ParseIP(ipString)
+	return binary.BigEndian.Uint32(ip.To4())
+}

client/internal/ebpf/ebpf/manager_linux.go

@@ -0,0 +1,116 @@
+package ebpf
+
+import (
+	_ "embed"
+	"net"
+	"sync"
+
+	"github.com/cilium/ebpf/link"
+	"github.com/cilium/ebpf/rlimit"
+	log "github.com/sirupsen/logrus"
+
+	"github.com/netbirdio/netbird/client/internal/ebpf/manager"
+)
+
+const (
+	mapKeyFeatures uint32 = 0
+
+	featureFlagWGProxy      = 0b00000001
+	featureFlagDnsForwarder = 0b00000010
+)
+
+var (
+	singleton     manager.Manager
+	singletonLock = &sync.Mutex{}
+)
+
+// required packages libbpf-dev, libc6-dev-i386-amd64-cross
+
+// GeneralManager is used to load multiple eBPF programs with a custom check (if then) done in prog.c
+// The manager simply adds a feature (byte) of each program to a map that is shared between the userspace and kernel.
+// When packet arrives, the C code checks for each feature (if it is set) and executes each enabled program (e.g., dns_fwd.c and wg_proxy.c).
+//
+//go:generate go run github.com/cilium/ebpf/cmd/bpf2go -cc clang-14 bpf src/prog.c -- -I /usr/x86_64-linux-gnu/include
+type GeneralManager struct {
+	lock         sync.Mutex
+	link         link.Link
+	featureFlags uint16
+	bpfObjs      bpfObjects
+}
+
+// GetEbpfManagerInstance return a static eBpf Manager instance
+func GetEbpfManagerInstance() manager.Manager {
+	singletonLock.Lock()
+	defer singletonLock.Unlock()
+	if singleton != nil {
+		return singleton
+	}
+	singleton = &GeneralManager{}
+	return singleton
+}
+
+func (tf *GeneralManager) setFeatureFlag(feature uint16) {
+	tf.featureFlags = tf.featureFlags | feature
+}
+
+func (tf *GeneralManager) loadXdp() error {
+	if tf.link != nil {
+		return nil
+	}
+	// it required for Docker
+	err := rlimit.RemoveMemlock()
+	if err != nil {
+		return err
+	}
+
+	iFace, err := net.InterfaceByName("lo")
+	if err != nil {
+		return err
+	}
+
+	// load pre-compiled programs into the kernel.
+	err = loadBpfObjects(&tf.bpfObjs, nil)
+	if err != nil {
+		return err
+	}
+
+	tf.link, err = link.AttachXDP(link.XDPOptions{
+		Program:   tf.bpfObjs.NbXdpProg,
+		Interface: iFace.Index,
+	})
+
+	if err != nil {
+		_ = tf.bpfObjs.Close()
+		tf.link = nil
+		return err
+	}
+	return nil
+}
+
+func (tf *GeneralManager) unsetFeatureFlag(feature uint16) error {
+	tf.lock.Lock()
+	defer tf.lock.Unlock()
+	tf.featureFlags &^= feature
+
+	if tf.link == nil {
+		return nil
+	}
+
+	if tf.featureFlags == 0 {
+		return tf.close()
+	}
+
+	return tf.bpfObjs.NbFeatures.Put(mapKeyFeatures, tf.featureFlags)
+}
+
+func (tf *GeneralManager) close() error {
+	log.Debugf("detach ebpf program ")
+	err := tf.bpfObjs.Close()
+	if err != nil {
+		log.Warnf("failed to close eBpf objects: %s", err)
+	}
+
+	err = tf.link.Close()
+	tf.link = nil
+	return err
+}

client/internal/ebpf/ebpf/manager_linux_test.go

@@ -0,0 +1,40 @@
+package ebpf
+
+import (
+	"testing"
+)
+
+func TestManager_setFeatureFlag(t *testing.T) {
+	mgr := GeneralManager{}
+	mgr.setFeatureFlag(featureFlagWGProxy)
+	if mgr.featureFlags != 1 {
+		t.Errorf("invalid faeture state")
+	}
+
+	mgr.setFeatureFlag(featureFlagDnsForwarder)
+	if mgr.featureFlags != 3 {
+		t.Errorf("invalid faeture state")
+	}
+}
+
+func TestManager_unsetFeatureFlag(t *testing.T) {
+	mgr := GeneralManager{}
+	mgr.setFeatureFlag(featureFlagWGProxy)
+	mgr.setFeatureFlag(featureFlagDnsForwarder)
+
+	err := mgr.unsetFeatureFlag(featureFlagWGProxy)
+	if err != nil {
+		t.Errorf("unexpected error: %s", err)
+	}
+	if mgr.featureFlags != 2 {
+		t.Errorf("invalid faeture state, expected: %d, got: %d", 2, mgr.featureFlags)
+	}
+
+	err = mgr.unsetFeatureFlag(featureFlagDnsForwarder)
+	if err != nil {
+		t.Errorf("unexpected error: %s", err)
+	}
+	if mgr.featureFlags != 0 {
+		t.Errorf("invalid faeture state, expected: %d, got: %d", 0, mgr.featureFlags)
+	}
+}

client/internal/ebpf/ebpf/src/dns_fwd.c

@@ -0,0 +1,64 @@
+const __u32 map_key_dns_ip = 0;
+const __u32 map_key_dns_port = 1;
+
+struct bpf_map_def SEC("maps") nb_map_dns_ip = {
+	.type = BPF_MAP_TYPE_ARRAY,
+	.key_size = sizeof(__u32),
+	.value_size = sizeof(__u32),
+	.max_entries = 10,
+};
+
+struct bpf_map_def SEC("maps") nb_map_dns_port = {
+	.type = BPF_MAP_TYPE_ARRAY,
+	.key_size = sizeof(__u32),
+	.value_size = sizeof(__u16),
+	.max_entries = 10,
+};
+
+__be32 dns_ip = 0;
+__be16 dns_port = 0;
+
+// 13568 is 53 in big endian
+__be16 GENERAL_DNS_PORT = 13568;
+
+bool read_settings() {
+    __u16 *port_value;
+    __u32 *ip_value;
+
+    // read dns ip
+    ip_value = bpf_map_lookup_elem(&nb_map_dns_ip, &map_key_dns_ip);
+    if(!ip_value) {
+        return false;
+    }
+    dns_ip = htonl(*ip_value);
+
+    // read dns port
+    port_value = bpf_map_lookup_elem(&nb_map_dns_port, &map_key_dns_port);
+    if (!port_value) {
+        return false;
+    }
+    dns_port = htons(*port_value);
+    return true;
+}
+
+int xdp_dns_fwd(struct iphdr  *ip, struct udphdr *udp) {
+    if (dns_port == 0) {
+        if(!read_settings()){
+            return XDP_PASS;
+        }
+        bpf_printk("dns port: %d", ntohs(dns_port));
+        bpf_printk("dns ip: %d", ntohl(dns_ip));
+    }
+
+    if (udp->dest == GENERAL_DNS_PORT && ip->daddr == dns_ip) {
+        udp->dest = dns_port;
+        return XDP_PASS;
+    }
+
+    if (udp->source == dns_port && ip->saddr == dns_ip) {
+        udp->source = GENERAL_DNS_PORT;
+        return XDP_PASS;
+    }
+
+    return XDP_PASS;
+}

client/internal/ebpf/ebpf/src/prog.c

@@ -0,0 +1,66 @@
+#include <stdbool.h>
+#include <linux/if_ether.h> // ETH_P_IP
+#include <linux/udp.h>
+#include <linux/ip.h>
+#include <netinet/in.h>
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include "dns_fwd.c"
+#include "wg_proxy.c"
+
+#define bpf_printk(fmt, ...)                                                   \
+  ({                                                                           \
+    char ____fmt[] = fmt;                                                      \
+    bpf_trace_printk(____fmt, sizeof(____fmt), ##__VA_ARGS__);                 \
+  })
+
+const __u16 flag_feature_wg_proxy = 0b01;
+const __u16 flag_feature_dns_fwd = 0b10;
+
+const __u32 map_key_features = 0;
+struct bpf_map_def SEC("maps") nb_features = {
+	.type = BPF_MAP_TYPE_ARRAY,
+	.key_size = sizeof(__u32),
+	.value_size = sizeof(__u16),
+	.max_entries = 10,
+};
+
+SEC("xdp")
+int nb_xdp_prog(struct xdp_md *ctx) {
+    __u16 *features;
+    features = bpf_map_lookup_elem(&nb_features, &map_key_features);
+    if (!features) {
+        return XDP_PASS;
+    }
+
+    void *data     = (void *)(long)ctx->data;
+    void *data_end = (void *)(long)ctx->data_end;
+    struct ethhdr *eth = data;
+    struct iphdr  *ip  = (data + sizeof(struct ethhdr));
+    struct udphdr *udp = (data + sizeof(struct ethhdr) + sizeof(struct iphdr));
+
+    // return early if not enough data
+    if (data + sizeof(struct ethhdr) + sizeof(struct iphdr) + sizeof(struct udphdr) > data_end){
+        return XDP_PASS;
+    }
+
+    // skip non IPv4 packages
+    if (eth->h_proto != htons(ETH_P_IP)) {
+       return XDP_PASS;
+    }
+
+    // skip non UPD packages
+    if (ip->protocol != IPPROTO_UDP) {
+       return XDP_PASS;
+    }
+
+    if (*features & flag_feature_dns_fwd) {
+        xdp_dns_fwd(ip, udp);
+    }
+
+    if (*features & flag_feature_wg_proxy) {
+        xdp_wg_proxy(ip, udp);
+    }
+    return XDP_PASS;
+}
+char _license[] SEC("license") = "GPL";

client/internal/ebpf/ebpf/src/wg_proxy.c

@@ -0,0 +1,54 @@
+const __u32 map_key_proxy_port = 0;
+const __u32 map_key_wg_port = 1;
+
+struct bpf_map_def SEC("maps") nb_wg_proxy_settings_map = {
+	.type = BPF_MAP_TYPE_ARRAY,
+	.key_size = sizeof(__u32),
+	.value_size = sizeof(__u16),
+	.max_entries = 10,
+};
+
+__u16 proxy_port = 0;
+__u16 wg_port = 0;
+
+bool read_port_settings() {
+    __u16 *value;
+    value = bpf_map_lookup_elem(&nb_wg_proxy_settings_map, &map_key_proxy_port);
+    if (!value) {
+        return false;
+    }
+
+    proxy_port = *value;
+
+    value = bpf_map_lookup_elem(&nb_wg_proxy_settings_map, &map_key_wg_port);
+    if (!value) {
+        return false;
+    }
+    wg_port = htons(*value);
+
+    return true;
+}
+
+int xdp_wg_proxy(struct iphdr  *ip, struct udphdr *udp) {
+    if (proxy_port == 0 || wg_port == 0) {
+        if (!read_port_settings()){
+            return XDP_PASS;
+        }
+        bpf_printk("proxy port: %d, wg port: %d", proxy_port, wg_port);
+    }
+
+    // 2130706433 = 127.0.0.1
+    if (ip->daddr != htonl(2130706433)) {
+        return XDP_PASS;
+    }
+
+    if (udp->source != wg_port){
+        return XDP_PASS;
+    }
+
+    __be16 new_src_port = udp->dest;
+    __be16 new_dst_port = htons(proxy_port);
+    udp->dest = new_dst_port;
+    udp->source = new_src_port;
+	return XDP_PASS;
+}

client/internal/ebpf/ebpf/wg_proxy_linux.go

@@ -0,0 +1,41 @@
+package ebpf
+
+import log "github.com/sirupsen/logrus"
+
+const (
+	mapKeyProxyPort uint32 = 0
+	mapKeyWgPort    uint32 = 1
+)
+
+func (tf *GeneralManager) LoadWgProxy(proxyPort, wgPort int) error {
+	log.Debugf("load ebpf WG proxy")
+	tf.lock.Lock()
+	defer tf.lock.Unlock()
+
+	err := tf.loadXdp()
+	if err != nil {
+		return err
+	}
+
+	err = tf.bpfObjs.NbWgProxySettingsMap.Put(mapKeyProxyPort, uint16(proxyPort))
+	if err != nil {
+		return err
+	}
+
+	err = tf.bpfObjs.NbWgProxySettingsMap.Put(mapKeyWgPort, uint16(wgPort))
+	if err != nil {
+		return err
+	}
+
+	tf.setFeatureFlag(featureFlagWGProxy)
+	err = tf.bpfObjs.NbFeatures.Put(mapKeyFeatures, tf.featureFlags)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+func (tf *GeneralManager) FreeWGProxy() error {
+	log.Debugf("free ebpf WG proxy")
+	return tf.unsetFeatureFlag(featureFlagWGProxy)
+}

client/internal/ebpf/instantiater_linux.go

@@ -0,0 +1,15 @@
+//go:build !android
+
+package ebpf
+
+import (
+	"github.com/netbirdio/netbird/client/internal/ebpf/ebpf"
+	"github.com/netbirdio/netbird/client/internal/ebpf/manager"
+)
+
+// GetEbpfManagerInstance is a wrapper function. This encapsulation is required because if the code import the internal
+// ebpf package the Go compiler will include the object files. But it is not supported on Android. It can cause instant
+// panic on older Android version.
+func GetEbpfManagerInstance() manager.Manager {
+	return ebpf.GetEbpfManagerInstance()
+}

client/internal/ebpf/instantiater_nonlinux.go

@@ -0,0 +1,10 @@
+//go:build !linux || android
+
+package ebpf
+
+import "github.com/netbirdio/netbird/client/internal/ebpf/manager"
+
+// GetEbpfManagerInstance return error because ebpf is not supported on all os
+func GetEbpfManagerInstance() manager.Manager {
+	panic("unsupported os")
+}

client/internal/ebpf/manager/manager.go

@@ -0,0 +1,9 @@
+package manager
+
+// Manager is used to load multiple eBPF programs. E.g., current DNS programs and WireGuard proxy
+type Manager interface {
+	LoadDNSFwd(ip string, dnsPort int) error
+	FreeDNSFwd() error
+	LoadWgProxy(proxyPort, wgPort int) error
+	FreeWGProxy() error
+}

client/internal/wgproxy/ebpf/loader.go

@@ -1,84 +0,0 @@
-//go:build linux && !android
-
-package ebpf
-
-import (
-	_ "embed"
-	"net"
-
-	"github.com/cilium/ebpf/link"
-	"github.com/cilium/ebpf/rlimit"
-)
-
-const (
-	mapKeyProxyPort uint32 = 0
-	mapKeyWgPort    uint32 = 1
-)
-
-//go:generate go run github.com/cilium/ebpf/cmd/bpf2go -cc clang-14 bpf src/portreplace.c --
-
-// EBPF is a wrapper for eBPF program
-type EBPF struct {
-	link link.Link
-}
-
-// NewEBPF create new EBPF instance
-func NewEBPF() *EBPF {
-	return &EBPF{}
-}
-
-// Load load ebpf program
-func (l *EBPF) Load(proxyPort, wgPort int) error {
-	// it required for Docker
-	err := rlimit.RemoveMemlock()
-	if err != nil {
-		return err
-	}
-
-	ifce, err := net.InterfaceByName("lo")
-	if err != nil {
-		return err
-	}
-
-	// Load pre-compiled programs into the kernel.
-	objs := bpfObjects{}
-	err = loadBpfObjects(&objs, nil)
-	if err != nil {
-		return err
-	}
-	defer func() {
-		_ = objs.Close()
-	}()
-
-	err = objs.NbWgProxySettingsMap.Put(mapKeyProxyPort, uint16(proxyPort))
-	if err != nil {
-		return err
-	}
-
-	err = objs.NbWgProxySettingsMap.Put(mapKeyWgPort, uint16(wgPort))
-	if err != nil {
-		return err
-	}
-
-	defer func() {
-		_ = objs.NbWgProxySettingsMap.Close()
-	}()
-
-	l.link, err = link.AttachXDP(link.XDPOptions{
-		Program:   objs.NbWgProxy,
-		Interface: ifce.Index,
-	})
-	if err != nil {
-		return err
-	}
-
-	return err
-}
-
-// Free ebpf program
-func (l *EBPF) Free() error {
-	if l.link != nil {
-		return l.link.Close()
-	}
-	return nil
-}

client/internal/wgproxy/ebpf/loader_test.go

@@ -1,18 +0,0 @@
-//go:build linux
-
-package ebpf
-
-import (
-	"testing"
-)
-
-func Test_newEBPF(t *testing.T) {
-	ebpf := NewEBPF()
-	err := ebpf.Load(1234, 51892)
-	defer func() {
-		_ = ebpf.Free()
-	}()
-	if err != nil {
-		t.Errorf("%s", err)
-	}
-}

client/internal/wgproxy/ebpf/src/portreplace.c

@@ -1,90 +0,0 @@
-#include <stdbool.h>
-#include <linux/if_ether.h> // ETH_P_IP
-#include <linux/udp.h>
-#include <linux/ip.h>
-#include <netinet/in.h>
-#include <linux/bpf.h>
-#include <bpf/bpf_helpers.h>
-
-#define bpf_printk(fmt, ...)                                                   \
-  ({                                                                           \
-    char ____fmt[] = fmt;                                                      \
-    bpf_trace_printk(____fmt, sizeof(____fmt), ##__VA_ARGS__);                 \
-  })
-
-const __u32 map_key_proxy_port = 0;
-const __u32 map_key_wg_port = 1;
-
-struct bpf_map_def SEC("maps") nb_wg_proxy_settings_map = {
-	.type = BPF_MAP_TYPE_ARRAY,
-	.key_size = sizeof(__u32),
-	.value_size = sizeof(__u16),
-	.max_entries = 10,
-};
-
-__u16 proxy_port = 0;
-__u16 wg_port = 0;
-
-bool read_port_settings() {
-    __u16 *value;
-    value = bpf_map_lookup_elem(&nb_wg_proxy_settings_map, &map_key_proxy_port);
-    if(!value) {
-        return false;
-    }
-
-    proxy_port = *value;
-
-    value = bpf_map_lookup_elem(&nb_wg_proxy_settings_map, &map_key_wg_port);
-    if(!value) {
-        return false;
-    }
-    wg_port = *value;
-
-    return true;
-}
-
-SEC("xdp")
-int nb_wg_proxy(struct xdp_md *ctx) {
-    if(proxy_port == 0 || wg_port == 0) {
-        if(!read_port_settings()){
-            return XDP_PASS;
-        }
-        bpf_printk("proxy port: %d, wg port: %d", proxy_port, wg_port);
-    }
-
-	void *data     = (void *)(long)ctx->data;
-	void *data_end = (void *)(long)ctx->data_end;
-	struct ethhdr *eth = data;
-    struct iphdr  *ip   = (data + sizeof(struct ethhdr));
-    struct udphdr *udp = (data + sizeof(struct ethhdr) + sizeof(struct iphdr));
-
-    // return early if not enough data
-    if (data + sizeof(struct ethhdr) + sizeof(struct iphdr) + sizeof(struct udphdr) > data_end){
-        return XDP_PASS;
-    }
-
-    // skip non IPv4 packages
-    if (eth->h_proto != htons(ETH_P_IP)) {
-       return XDP_PASS;
-    }
-
-    if (ip->protocol != IPPROTO_UDP) {
-       return XDP_PASS;
-    }
-
-    // 2130706433 = 127.0.0.1
-    if (ip->daddr != htonl(2130706433)) {
-        return XDP_PASS;
-    }
-
-    if (udp->source != htons(wg_port)){
-        return XDP_PASS;
-    }
-
-    __be16 new_src_port = udp->dest;
-    __be16 new_dst_port = htons(proxy_port);
-    udp->dest = new_dst_port;
-    udp->source = new_src_port;
-	return XDP_PASS;
-}
-char _license[] SEC("license") = "GPL";

client/internal/wgproxy/proxy_ebpf.go

@@ -12,15 +12,15 @@ import (
 
 	"github.com/google/gopacket"
 	"github.com/google/gopacket/layers"
-
 	log "github.com/sirupsen/logrus"
 
-	ebpf2 "github.com/netbirdio/netbird/client/internal/wgproxy/ebpf"
+	"github.com/netbirdio/netbird/client/internal/ebpf"
+	ebpfMgr "github.com/netbirdio/netbird/client/internal/ebpf/manager"
 )
 
 // WGEBPFProxy definition for proxy with EBPF support
 type WGEBPFProxy struct {
-	ebpf              *ebpf2.EBPF
+	ebpfManager       ebpfMgr.Manager
 	lastUsedPort      uint16
 	localWGListenPort int
 
@@ -36,7 +36,7 @@ func NewWGEBPFProxy(wgPort int) *WGEBPFProxy {
 	log.Debugf("instantiate ebpf proxy")
 	wgProxy := &WGEBPFProxy{
 		localWGListenPort: wgPort,
-		ebpf:              ebpf2.NewEBPF(),
+		ebpfManager:       ebpf.GetEbpfManagerInstance(),
 		lastUsedPort:      0,
 		turnConnStore:     make(map[uint16]net.Conn),
 	}
@@ -56,7 +56,7 @@ func (p *WGEBPFProxy) Listen() error {
 		return err
 	}
 
-	err = p.ebpf.Load(wgPorxyPort, p.localWGListenPort)
+	err = p.ebpfManager.LoadWgProxy(wgPorxyPort, p.localWGListenPort)
 	if err != nil {
 		return err
 	}
@@ -110,7 +110,7 @@ func (p *WGEBPFProxy) Free() error {
 		err1 = p.conn.Close()
 	}
 
-	err2 = p.ebpf.Free()
+	err2 = p.ebpfManager.FreeWGProxy()
 	if p.rawConn != nil {
 		err3 = p.rawConn.Close()
 	}

iface/iface.go

@@ -112,7 +112,7 @@ func (w *WGIface) Close() error {
 	return w.tun.Close()
 }
 
-// SetFilter sets packet filters for the userspace impelemntation
+// SetFilter sets packet filters for the userspace implementation
 func (w *WGIface) SetFilter(filter PacketFilter) error {
 	w.mu.Lock()
 	defer w.mu.Unlock()