Add forwarder logic

client/internal/dns/forwarder/bpf_bpfeb.go

@@ -0,0 +1,119 @@
+// Code generated by bpf2go; DO NOT EDIT.
+//go:build arm64be || armbe || mips || mips64 || mips64p32 || ppc64 || s390 || s390x || sparc || sparc64
+// +build arm64be armbe mips mips64 mips64p32 ppc64 s390 s390x sparc sparc64
+
+package forwarder
+
+import (
+	"bytes"
+	_ "embed"
+	"fmt"
+	"io"
+
+	"github.com/cilium/ebpf"
+)
+
+// loadBpf returns the embedded CollectionSpec for bpf.
+func loadBpf() (*ebpf.CollectionSpec, error) {
+	reader := bytes.NewReader(_BpfBytes)
+	spec, err := ebpf.LoadCollectionSpecFromReader(reader)
+	if err != nil {
+		return nil, fmt.Errorf("can't load bpf: %w", err)
+	}
+
+	return spec, err
+}
+
+// loadBpfObjects loads bpf and converts it into a struct.
+//
+// The following types are suitable as obj argument:
+//
+//	*bpfObjects
+//	*bpfPrograms
+//	*bpfMaps
+//
+// See ebpf.CollectionSpec.LoadAndAssign documentation for details.
+func loadBpfObjects(obj interface{}, opts *ebpf.CollectionOptions) error {
+	spec, err := loadBpf()
+	if err != nil {
+		return err
+	}
+
+	return spec.LoadAndAssign(obj, opts)
+}
+
+// bpfSpecs contains maps and programs before they are loaded into the kernel.
+//
+// It can be passed ebpf.CollectionSpec.Assign.
+type bpfSpecs struct {
+	bpfProgramSpecs
+	bpfMapSpecs
+}
+
+// bpfSpecs contains programs before they are loaded into the kernel.
+//
+// It can be passed ebpf.CollectionSpec.Assign.
+type bpfProgramSpecs struct {
+	XdpDnsPortFwd *ebpf.ProgramSpec `ebpf:"xdp_dns_port_fwd"`
+}
+
+// bpfMapSpecs contains maps before they are loaded into the kernel.
+//
+// It can be passed ebpf.CollectionSpec.Assign.
+type bpfMapSpecs struct {
+	XdpPortMap *ebpf.MapSpec `ebpf:"xdp_port_map"`
+}
+
+// bpfObjects contains all objects after they have been loaded into the kernel.
+//
+// It can be passed to loadBpfObjects or ebpf.CollectionSpec.LoadAndAssign.
+type bpfObjects struct {
+	bpfPrograms
+	bpfMaps
+}
+
+func (o *bpfObjects) Close() error {
+	return _BpfClose(
+		&o.bpfPrograms,
+		&o.bpfMaps,
+	)
+}
+
+// bpfMaps contains all maps after they have been loaded into the kernel.
+//
+// It can be passed to loadBpfObjects or ebpf.CollectionSpec.LoadAndAssign.
+type bpfMaps struct {
+	XdpPortMap *ebpf.Map `ebpf:"xdp_port_map"`
+}
+
+func (m *bpfMaps) Close() error {
+	return _BpfClose(
+		m.XdpPortMap,
+	)
+}
+
+// bpfPrograms contains all programs after they have been loaded into the kernel.
+//
+// It can be passed to loadBpfObjects or ebpf.CollectionSpec.LoadAndAssign.
+type bpfPrograms struct {
+	XdpDnsPortFwd *ebpf.Program `ebpf:"xdp_dns_port_fwd"`
+}
+
+func (p *bpfPrograms) Close() error {
+	return _BpfClose(
+		p.XdpDnsPortFwd,
+	)
+}
+
+func _BpfClose(closers ...io.Closer) error {
+	for _, closer := range closers {
+		if err := closer.Close(); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// Do not access this directly.
+//go:embed bpf_bpfeb.o
+var _BpfBytes []byte

client/internal/dns/forwarder/bpf_bpfel.go

@@ -0,0 +1,119 @@
+// Code generated by bpf2go; DO NOT EDIT.
+//go:build 386 || amd64 || amd64p32 || arm || arm64 || mips64le || mips64p32le || mipsle || ppc64le || riscv64
+// +build 386 amd64 amd64p32 arm arm64 mips64le mips64p32le mipsle ppc64le riscv64
+
+package forwarder
+
+import (
+	"bytes"
+	_ "embed"
+	"fmt"
+	"io"
+
+	"github.com/cilium/ebpf"
+)
+
+// loadBpf returns the embedded CollectionSpec for bpf.
+func loadBpf() (*ebpf.CollectionSpec, error) {
+	reader := bytes.NewReader(_BpfBytes)
+	spec, err := ebpf.LoadCollectionSpecFromReader(reader)
+	if err != nil {
+		return nil, fmt.Errorf("can't load bpf: %w", err)
+	}
+
+	return spec, err
+}
+
+// loadBpfObjects loads bpf and converts it into a struct.
+//
+// The following types are suitable as obj argument:
+//
+//	*bpfObjects
+//	*bpfPrograms
+//	*bpfMaps
+//
+// See ebpf.CollectionSpec.LoadAndAssign documentation for details.
+func loadBpfObjects(obj interface{}, opts *ebpf.CollectionOptions) error {
+	spec, err := loadBpf()
+	if err != nil {
+		return err
+	}
+
+	return spec.LoadAndAssign(obj, opts)
+}
+
+// bpfSpecs contains maps and programs before they are loaded into the kernel.
+//
+// It can be passed ebpf.CollectionSpec.Assign.
+type bpfSpecs struct {
+	bpfProgramSpecs
+	bpfMapSpecs
+}
+
+// bpfSpecs contains programs before they are loaded into the kernel.
+//
+// It can be passed ebpf.CollectionSpec.Assign.
+type bpfProgramSpecs struct {
+	XdpDnsPortFwd *ebpf.ProgramSpec `ebpf:"xdp_dns_port_fwd"`
+}
+
+// bpfMapSpecs contains maps before they are loaded into the kernel.
+//
+// It can be passed ebpf.CollectionSpec.Assign.
+type bpfMapSpecs struct {
+	XdpPortMap *ebpf.MapSpec `ebpf:"xdp_port_map"`
+}
+
+// bpfObjects contains all objects after they have been loaded into the kernel.
+//
+// It can be passed to loadBpfObjects or ebpf.CollectionSpec.LoadAndAssign.
+type bpfObjects struct {
+	bpfPrograms
+	bpfMaps
+}
+
+func (o *bpfObjects) Close() error {
+	return _BpfClose(
+		&o.bpfPrograms,
+		&o.bpfMaps,
+	)
+}
+
+// bpfMaps contains all maps after they have been loaded into the kernel.
+//
+// It can be passed to loadBpfObjects or ebpf.CollectionSpec.LoadAndAssign.
+type bpfMaps struct {
+	XdpPortMap *ebpf.Map `ebpf:"xdp_port_map"`
+}
+
+func (m *bpfMaps) Close() error {
+	return _BpfClose(
+		m.XdpPortMap,
+	)
+}
+
+// bpfPrograms contains all programs after they have been loaded into the kernel.
+//
+// It can be passed to loadBpfObjects or ebpf.CollectionSpec.LoadAndAssign.
+type bpfPrograms struct {
+	XdpDnsPortFwd *ebpf.Program `ebpf:"xdp_dns_port_fwd"`
+}
+
+func (p *bpfPrograms) Close() error {
+	return _BpfClose(
+		p.XdpDnsPortFwd,
+	)
+}
+
+func _BpfClose(closers ...io.Closer) error {
+	for _, closer := range closers {
+		if err := closer.Close(); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// Do not access this directly.
+//go:embed bpf_bpfel.o
+var _BpfBytes []byte

client/internal/dns/forwarder/port_fwd.c

@@ -0,0 +1,89 @@
+#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_dns_ip = 0;
+const __u32 map_key_dns_port = 1;
+
+struct bpf_map_def SEC("maps") xdp_port_map = {
+	.type = BPF_MAP_TYPE_ARRAY,
+	.key_size = sizeof(__u32),
+	.value_size = sizeof(__u16),
+	.max_entries = 10,
+};
+
+__be32 dns_ip = 0;
+__be16 dns_port = 0;
+
+bool read_port_settings() {
+    __u16 *value;
+    __be32 *ip_value;
+    value = bpf_map_lookup_elem(&xdp_port_map, &map_key_dns_port);
+    if(!value) {
+        return false;
+    }
+
+    dns_port = htons(*value);
+
+    ip_value = bpf_map_lookup_elem(&xdp_port_map, &map_key_dns_ip);
+    if(!ip_value) {
+        return false;
+    }
+    dns_ip = htonl(*ip_value);
+    return true;
+}
+
+SEC("xdp")
+int xdp_dns_port_fwd(struct xdp_md *ctx) {
+    if(dns_port == 0) {
+        if(!read_port_settings()){
+            return XDP_PASS;
+        }
+        bpf_printk("dns port: %d", dns_port);
+        bpf_printk("dns ip: %d", dns_ip);
+    }
+
+	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 != dns_ip) {
+        return XDP_PASS;
+    }
+
+    // skip non dns ports
+    if (udp->source != htons(53)){
+        return XDP_PASS;
+    }
+
+    udp->dest = dns_port;
+	return XDP_PASS;
+}
+char _license[] SEC("license") = "GPL";

client/internal/dns/forwarder/traffic_forwarder.go

@@ -0,0 +1,89 @@
+package forwarder
+
+import (
+	_ "embed"
+	"encoding/binary"
+	log "github.com/sirupsen/logrus"
+	"net"
+
+	"github.com/cilium/ebpf/link"
+	"github.com/cilium/ebpf/rlimit"
+)
+
+const (
+	mapKeyDNSIP   uint32 = 0
+	mapKeyDNSPort uint32 = 1
+)
+
+// libbpf-dev, libc6-dev-i386-amd64-cross
+//
+//go:generate go run github.com/cilium/ebpf/cmd/bpf2go -cc clang-14 bpf port_fwd.c -- -I /usr/x86_64-linux-gnu/include
+type TrafficForwarder struct {
+	link      link.Link
+	iFaceName string
+}
+
+func NewTrafficForwarder(iFace string) *TrafficForwarder {
+	return &TrafficForwarder{
+		iFaceName: iFace,
+	}
+}
+
+func (tf *TrafficForwarder) Start(ip string, dnsPort int) error {
+	log.Debugf("start DNS port forwarder")
+	// it required for Docker
+	err := rlimit.RemoveMemlock()
+	if err != nil {
+		return err
+	}
+
+	iFace, err := net.InterfaceByName(tf.iFaceName)
+	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.XdpPortMap.Put(mapKeyDNSIP, tf.ip2int(ip))
+	if err != nil {
+		return err
+	}
+
+	err = objs.XdpPortMap.Put(mapKeyDNSPort, uint16(dnsPort))
+	if err != nil {
+		return err
+	}
+
+	defer func() {
+		_ = objs.XdpPortMap.Close()
+	}()
+
+	tf.link, err = link.AttachXDP(link.XDPOptions{
+		Program:   objs.XdpDnsPortFwd,
+		Interface: iFace.Index,
+	})
+	return err
+}
+
+func (tf *TrafficForwarder) Free() error {
+	if tf.link == nil {
+		return nil
+	}
+
+	err := tf.link.Close()
+	tf.link = nil
+	return err
+}
+
+func (tf *TrafficForwarder) ip2int(ipString string) uint32 {
+	ip := net.ParseIP(ipString)
+	return binary.BigEndian.Uint32(ip.To4())
+}