diff --git a/client/internal/dns/service_listener.go b/client/internal/dns/service_listener.go index 3dc29c4dc..d65a727b1 100644 --- a/client/internal/dns/service_listener.go +++ b/client/internal/dns/service_listener.go @@ -6,6 +6,7 @@ import ( "net" "net/netip" "runtime" + "slices" "strconv" "sync" "time" @@ -17,17 +18,20 @@ import ( nberrors "github.com/netbirdio/netbird/client/errors" firewall "github.com/netbirdio/netbird/client/firewall/manager" - "github.com/netbirdio/netbird/client/internal/ebpf" - ebpfMgr "github.com/netbirdio/netbird/client/internal/ebpf/manager" ) const ( customPort = 5053 + // randomPortAttempts bounds the search for a port free on both protocols. + randomPortAttempts = 5 ) var ( defaultIP = netip.MustParseAddr("127.0.0.1") customIP = netip.MustParseAddr("127.0.0.153") + + // dnatProtocols are the protocols the port 53 redirect covers. + dnatProtocols = []firewall.Protocol{firewall.ProtocolUDP, firewall.ProtocolTCP} ) type serviceViaListener struct { @@ -40,9 +44,20 @@ type serviceViaListener struct { listenPort uint16 listenerIsRunning bool listenerFlagLock sync.Mutex - ebpfService ebpfMgr.Manager firewall Firewall - tcpDNATConfigured bool + // dnatRules holds the port 53 redirects that are installed and not yet + // removed, so a removal that fails can be retried. + dnatRules []dnatRule +} + +// dnatRule is a port 53 redirect as it was installed. The target is kept with +// the rule because the listener can come back on a different address or port, +// and a retried removal has to name the address and port the rule was added +// with, not the ones in use now. +type dnatRule struct { + protocol firewall.Protocol + ip netip.Addr + port uint16 } func newServiceViaListener(wgIface WGIface, customAddr *netip.AddrPort, fw Firewall) *serviceViaListener { @@ -112,34 +127,93 @@ func (s *serviceViaListener) Listen() error { } }() - // When eBPF redirects UDP port 53 to our listen port, TCP still needs - // a DNAT rule because eBPF only handles UDP. - if s.ebpfService != nil && s.firewall != nil && s.listenPort != DefaultPort { - if err := s.firewall.AddOutputDNAT(s.listenIP, firewall.ProtocolTCP, DefaultPort, s.listenPort); err != nil { - log.Warnf("failed to add DNS TCP DNAT rule, TCP DNS on port 53 will not work: %v", err) - } else { - s.tcpDNATConfigured = true - log.Infof("added DNS TCP DNAT rule: %s:%d -> %s:%d", s.listenIP, DefaultPort, s.listenIP, s.listenPort) - } + if s.listenPort != DefaultPort { + s.setupDNAT() } return nil } +// setupDNAT redirects port 53 to the port the DNS server actually listens on. +// Both protocols must be redirected or none: RuntimePort reports port 53 only +// while the full redirect is in place, so a half-configured redirect would +// advertise a resolver that answers over one protocol. +func (s *serviceViaListener) setupDNAT() { + if s.firewall == nil { + log.Errorf("no firewall manager available to redirect DNS port %d to %d, "+ + "clients pointed at %s will not reach the resolver", DefaultPort, s.listenPort, s.listenIP) + return + } + + // Clear whatever an earlier removal left behind first. Those rules can point + // at an address or port this listener no longer uses, and they are matched + // before anything added now, so adding a redirect on top of one would keep + // sending port 53 traffic to the previous listener while reporting the + // redirect as complete. The rules stay recorded for a later attempt. + if err := s.removeDNAT(); err != nil { + log.Errorf("failed to remove stale DNS DNAT rules, leaving port %d redirected to the previous listener: %v", + DefaultPort, err) + return + } + + for _, proto := range dnatProtocols { + if err := s.firewall.AddOutputDNAT(s.listenIP, proto, DefaultPort, s.listenPort); err != nil { + log.Errorf("failed to add DNS %s DNAT rule, DNS on port %d will not work: %v", + proto, DefaultPort, err) + if err := s.removeDNAT(); err != nil { + log.Warnf("failed to roll back DNS DNAT rules, retrying on stop: %v", err) + } + return + } + s.dnatRules = append(s.dnatRules, dnatRule{protocol: proto, ip: s.listenIP, port: s.listenPort}) + } + + log.Infof("added DNS DNAT rules: %s:%d -> %s:%d (UDP + TCP)", s.listenIP, DefaultPort, s.listenIP, s.listenPort) +} + +// removeDNAT removes every installed port 53 redirect. A rule whose removal +// fails stays recorded so a later setup or Stop retries it, rather than leaving +// port 53 pointing at a resolver that is no longer listening. +func (s *serviceViaListener) removeDNAT() error { + if s.firewall == nil { + return nil + } + + var merr *multierror.Error + var remaining []dnatRule + for _, rule := range s.dnatRules { + if err := s.firewall.RemoveOutputDNAT(rule.ip, rule.protocol, DefaultPort, rule.port); err != nil { + merr = multierror.Append(merr, fmt.Errorf("remove DNS %s DNAT rule for %s:%d: %w", + rule.protocol, rule.ip, rule.port, err)) + remaining = append(remaining, rule) + } + } + s.dnatRules = remaining + + return nberrors.FormatErrorOrNil(merr) +} + func (s *serviceViaListener) Stop() error { s.listenerFlagLock.Lock() defer s.listenerFlagLock.Unlock() + var merr *multierror.Error + + // Redirects are removed even when the listener is already stopped, so that + // a removal which failed earlier is retried instead of leaving port 53 + // pointing at a resolver that no longer listens. + if err := s.removeDNAT(); err != nil { + merr = multierror.Append(merr, err) + } + if !s.listenerIsRunning { - return nil + return nberrors.FormatErrorOrNil(merr) } s.listenerIsRunning = false ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second) defer cancel() - var merr *multierror.Error - if err := s.server.ShutdownContext(ctx); err != nil { merr = multierror.Append(merr, fmt.Errorf("stop DNS UDP server: %w", err)) } @@ -148,19 +222,6 @@ func (s *serviceViaListener) Stop() error { merr = multierror.Append(merr, fmt.Errorf("stop DNS TCP server: %w", err)) } - if s.tcpDNATConfigured && s.firewall != nil { - if err := s.firewall.RemoveOutputDNAT(s.listenIP, firewall.ProtocolTCP, DefaultPort, s.listenPort); err != nil { - merr = multierror.Append(merr, fmt.Errorf("remove DNS TCP DNAT rule: %w", err)) - } - s.tcpDNATConfigured = false - } - - if s.ebpfService != nil { - if err := s.ebpfService.FreeDNSFwd(); err != nil { - merr = multierror.Append(merr, fmt.Errorf("stop traffic forwarder: %w", err)) - } - } - return nberrors.FormatErrorOrNil(merr) } @@ -177,11 +238,23 @@ func (s *serviceViaListener) RuntimePort() int { s.listenerFlagLock.Lock() defer s.listenerFlagLock.Unlock() - if s.ebpfService != nil { + if s.redirectInstalled() { return DefaultPort - } else { - return int(s.listenPort) } + return int(s.listenPort) +} + +// redirectInstalled reports whether every protocol is redirected from port 53 +// to the address and port the listener currently serves. Rules left over from +// an earlier listener do not count. +func (s *serviceViaListener) redirectInstalled() bool { + for _, proto := range dnatProtocols { + current := dnatRule{protocol: proto, ip: s.listenIP, port: s.listenPort} + if !slices.Contains(s.dnatRules, current) { + return false + } + } + return true } func (s *serviceViaListener) RuntimeIP() netip.Addr { @@ -190,30 +263,29 @@ func (s *serviceViaListener) RuntimeIP() netip.Addr { // evalListenAddress figures out the listen address for the DNS server. // IPv4-only: all peers have a v4 overlay address, and DNS config points to v4. -// First checks port 53 on WG interface or lo, then tries eBPF on a random port, -// then falls back to port 5053. +// Prefers port 53 on the overlay interface or lo, so no redirect is needed at +// all; when it is taken it falls back to port 5053 and then to a random free +// port, both of which need the port 53 redirect set up by setupDNAT. func (s *serviceViaListener) evalListenAddress() (netip.Addr, uint16, error) { if s.customAddr != nil { return s.customAddr.Addr(), s.customAddr.Port(), nil } - ip, ok := s.testFreePort(DefaultPort) - if ok { + if ip, ok := s.testFreePort(DefaultPort); ok { return ip, DefaultPort, nil } - ebpfSrv, port, ok := s.tryToUseeBPF() - if ok { - s.ebpfService = ebpfSrv - return s.wgInterface.Address().IP, port, nil - } - - ip, ok = s.testFreePort(customPort) - if ok { + if ip, ok := s.testFreePort(customPort); ok { return ip, customPort, nil } - return netip.Addr{}, 0, fmt.Errorf("failed to find a free port for DNS server") + ip := s.wgInterface.Address().IP + port, err := s.randomFreePort(ip) + if err != nil { + return netip.Addr{}, 0, fmt.Errorf("find a free port for DNS server: %w", err) + } + + return ip, port, nil } func (s *serviceViaListener) testFreePort(port int) (netip.Addr, bool) { @@ -260,48 +332,25 @@ func (s *serviceViaListener) tryToBind(ip netip.Addr, port int) bool { return true } -// tryToUseeBPF 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 free -// port 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 the chosen port. -func (s *serviceViaListener) tryToUseeBPF() (ebpfMgr.Manager, uint16, bool) { - if runtime.GOOS != "linux" { - return nil, 0, false +// randomFreePort returns a port that is free on ip for both UDP and TCP, since +// the DNS server binds both. The probe listeners are closed again, so the port +// is only likely, not guaranteed, to still be free when the server binds it. +func (s *serviceViaListener) randomFreePort(ip netip.Addr) (uint16, error) { + for range randomPortAttempts { + probeListener, err := net.ListenUDP("udp4", &net.UDPAddr{}) + if err != nil { + return 0, fmt.Errorf("bind random port: %w", err) + } + + port := uint16(probeListener.LocalAddr().(*net.UDPAddr).Port) + if err := probeListener.Close(); err != nil { + return 0, fmt.Errorf("free up probed port: %w", err) + } + + if s.tryToBind(ip, int(port)) { + return port, nil + } } - port, err := s.generateFreePort() //nolint:staticcheck,unused - if err != nil { - log.Warnf("failed to generate a free port for eBPF DNS forwarder server: %s", err) - return nil, 0, false - } - - ebpfSrv := ebpf.GetEbpfManagerInstance() - err = ebpfSrv.LoadDNSFwd(s.wgInterface.Address().IP, int(port)) - if err != nil { - log.Warnf("failed to load DNS forwarder eBPF program, error: %s", err) - return nil, 0, false - } - - return ebpfSrv, port, true -} - -func (s *serviceViaListener) generateFreePort() (uint16, error) { - ok := s.tryToBind(s.wgInterface.Address().IP, customPort) - if ok { - return customPort, nil - } - - probeListener, err := net.ListenUDP("udp4", &net.UDPAddr{}) - if err != nil { - log.Debugf("failed to bind random port for DNS: %s", err) - return 0, err - } - - port := uint16(probeListener.LocalAddr().(*net.UDPAddr).Port) - if err = probeListener.Close(); err != nil { - log.Debugf("failed to free up DNS port: %s", err) - return 0, err - } - return port, nil + return 0, fmt.Errorf("no port free for UDP and TCP on %s after %d attempts", ip, randomPortAttempts) } diff --git a/client/internal/dns/service_listener_test.go b/client/internal/dns/service_listener_test.go index 90ef71d19..b158a79fd 100644 --- a/client/internal/dns/service_listener_test.go +++ b/client/internal/dns/service_listener_test.go @@ -1,6 +1,7 @@ package dns import ( + "errors" "fmt" "net" "net/netip" @@ -10,6 +11,8 @@ import ( "github.com/miekg/dns" "github.com/stretchr/testify/assert" "github.com/stretchr/testify/require" + + firewall "github.com/netbirdio/netbird/client/firewall/manager" ) func TestServiceViaListener_TCPAndUDP(t *testing.T) { @@ -84,3 +87,133 @@ func TestServiceViaListener_TCPAndUDP(t *testing.T) { require.NotEmpty(t, tcpResp.Answer) assert.Contains(t, tcpResp.Answer[0].String(), "192.0.2.1", "TCP response should contain expected IP") } + +type dnatCall struct { + rule dnatRule + added bool +} + +// fakeFirewall records DNAT calls and fails the ones named in addErrs/removeErrs. +type fakeFirewall struct { + calls []dnatCall + addErrs map[firewall.Protocol]error + removeErrs map[firewall.Protocol]error +} + +func (f *fakeFirewall) AddOutputDNAT(ip netip.Addr, protocol firewall.Protocol, _, translatedPort uint16) error { + if err := f.addErrs[protocol]; err != nil { + return err + } + f.calls = append(f.calls, dnatCall{rule: dnatRule{protocol: protocol, ip: ip, port: translatedPort}, added: true}) + return nil +} + +func (f *fakeFirewall) RemoveOutputDNAT(ip netip.Addr, protocol firewall.Protocol, _, translatedPort uint16) error { + if err := f.removeErrs[protocol]; err != nil { + return err + } + f.calls = append(f.calls, dnatCall{rule: dnatRule{protocol: protocol, ip: ip, port: translatedPort}}) + return nil +} + +func newDNATTestService(fw Firewall) *serviceViaListener { + return &serviceViaListener{ + listenIP: netip.MustParseAddr("100.64.0.1"), + listenPort: customPort, + firewall: fw, + } +} + +func TestSetupDNAT_BothProtocols(t *testing.T) { + svc := newDNATTestService(&fakeFirewall{}) + + svc.setupDNAT() + + assert.Len(t, svc.dnatRules, len(dnatProtocols)) + assert.Equal(t, DefaultPort, svc.RuntimePort(), "port 53 is advertised once both redirects are installed") +} + +func TestSetupDNAT_RollsBackPartialRedirect(t *testing.T) { + fw := &fakeFirewall{addErrs: map[firewall.Protocol]error{firewall.ProtocolTCP: errors.New("nftables busy")}} + svc := newDNATTestService(fw) + + svc.setupDNAT() + + assert.Empty(t, svc.dnatRules, "the UDP redirect installed before the failure must be rolled back") + assert.Equal(t, int(svc.listenPort), svc.RuntimePort(), "an incomplete redirect must not advertise port 53") + udp := dnatRule{protocol: firewall.ProtocolUDP, ip: svc.listenIP, port: svc.listenPort} + assert.Contains(t, fw.calls, dnatCall{rule: udp}, "UDP removal should have been attempted") +} + +// A rollback that fails must keep the rule recorded, so port 53 is not left +// redirected to a resolver that no longer listens. +func TestStop_RetriesFailedDNATRemoval(t *testing.T) { + fw := &fakeFirewall{ + addErrs: map[firewall.Protocol]error{firewall.ProtocolTCP: errors.New("nftables busy")}, + removeErrs: map[firewall.Protocol]error{firewall.ProtocolUDP: errors.New("nftables busy")}, + } + svc := newDNATTestService(fw) + + svc.setupDNAT() + udp := dnatRule{protocol: firewall.ProtocolUDP, ip: svc.listenIP, port: svc.listenPort} + require.Equal(t, []dnatRule{udp}, svc.dnatRules, "a failed rollback keeps the rule for a later retry") + + require.Error(t, svc.Stop(), "the failing removal should be reported") + require.Equal(t, []dnatRule{udp}, svc.dnatRules) + + delete(fw.removeErrs, firewall.ProtocolUDP) + require.NoError(t, svc.Stop(), "a later stop retries the removal") + assert.Empty(t, svc.dnatRules) +} + +// A stale rule that cannot be removed is matched before anything added now, so +// no new redirect may be installed on top of it and port 53 must not be +// advertised as reaching this listener. +func TestSetupDNAT_AbortsWhileStaleRuleRemains(t *testing.T) { + fw := &fakeFirewall{removeErrs: map[firewall.Protocol]error{firewall.ProtocolUDP: errors.New("nftables busy")}} + svc := newDNATTestService(fw) + stalePort := svc.listenPort + + svc.setupDNAT() + require.Error(t, svc.Stop()) + staleUDP := dnatRule{protocol: firewall.ProtocolUDP, ip: svc.listenIP, port: stalePort} + require.Equal(t, []dnatRule{staleUDP}, svc.dnatRules) + + svc.listenPort = stalePort + 1 + fw.calls = nil + + svc.setupDNAT() + + assert.Equal(t, []dnatRule{staleUDP}, svc.dnatRules, "the stale rule stays recorded for a later attempt") + for _, call := range fw.calls { + assert.False(t, call.added, "no redirect may be installed while a stale one is still in place") + } + assert.Equal(t, int(svc.listenPort), svc.RuntimePort(), "port 53 must not be advertised") +} + +// A rule left behind by a failed removal must be removed with the address and +// port it was installed with, even when the listener has since moved to another +// port, and it must not count towards the redirect the new listener advertises. +func TestSetupDNAT_ClearsStaleRuleAfterPortChange(t *testing.T) { + fw := &fakeFirewall{removeErrs: map[firewall.Protocol]error{firewall.ProtocolUDP: errors.New("nftables busy")}} + svc := newDNATTestService(fw) + stalePort := svc.listenPort + + svc.setupDNAT() + require.Error(t, svc.Stop()) + staleUDP := dnatRule{protocol: firewall.ProtocolUDP, ip: svc.listenIP, port: stalePort} + require.Equal(t, []dnatRule{staleUDP}, svc.dnatRules) + + delete(fw.removeErrs, firewall.ProtocolUDP) + svc.listenPort = stalePort + 1 + fw.calls = nil + + svc.setupDNAT() + + assert.Contains(t, fw.calls, dnatCall{rule: staleUDP}, "the stale rule must be removed with its original port") + assert.Len(t, svc.dnatRules, len(dnatProtocols)) + assert.Equal(t, DefaultPort, svc.RuntimePort(), "the new listener is fully redirected") + for _, rule := range svc.dnatRules { + assert.Equal(t, svc.listenPort, rule.port, "only rules for the current listener remain") + } +} diff --git a/client/internal/ebpf/ebpf/bpf_bpfeb.go b/client/internal/ebpf/ebpf/bpf_bpfeb.go index 04b19883b..4b6230217 100644 --- a/client/internal/ebpf/ebpf/bpf_bpfeb.go +++ b/client/internal/ebpf/ebpf/bpf_bpfeb.go @@ -1,5 +1,5 @@ // Code generated by bpf2go; DO NOT EDIT. -//go:build arm64be || armbe || mips || mips64 || mips64p32 || ppc64 || s390 || s390x || sparc || sparc64 +//go:build mips || mips64 || ppc64 || s390x package ebpf @@ -47,9 +47,10 @@ func loadBpfObjects(obj interface{}, opts *ebpf.CollectionOptions) error { type bpfSpecs struct { bpfProgramSpecs bpfMapSpecs + bpfVariableSpecs } -// bpfSpecs contains programs before they are loaded into the kernel. +// bpfProgramSpecs contains programs before they are loaded into the kernel. // // It can be passed ebpf.CollectionSpec.Assign. type bpfProgramSpecs struct { @@ -61,17 +62,28 @@ type bpfProgramSpecs struct { // 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"` } +// bpfVariableSpecs contains global variables before they are loaded into the kernel. +// +// It can be passed ebpf.CollectionSpec.Assign. +type bpfVariableSpecs struct { + FlagFeatureWgProxy *ebpf.VariableSpec `ebpf:"flag_feature_wg_proxy"` + MapKeyFeatures *ebpf.VariableSpec `ebpf:"map_key_features"` + MapKeyProxyPort *ebpf.VariableSpec `ebpf:"map_key_proxy_port"` + MapKeyWgPort *ebpf.VariableSpec `ebpf:"map_key_wg_port"` + ProxyPort *ebpf.VariableSpec `ebpf:"proxy_port"` + WgPort *ebpf.VariableSpec `ebpf:"wg_port"` +} + // 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 + bpfVariables } func (o *bpfObjects) Close() error { @@ -86,20 +98,28 @@ 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, ) } +// bpfVariables contains all global variables after they have been loaded into the kernel. +// +// It can be passed to loadBpfObjects or ebpf.CollectionSpec.LoadAndAssign. +type bpfVariables struct { + FlagFeatureWgProxy *ebpf.Variable `ebpf:"flag_feature_wg_proxy"` + MapKeyFeatures *ebpf.Variable `ebpf:"map_key_features"` + MapKeyProxyPort *ebpf.Variable `ebpf:"map_key_proxy_port"` + MapKeyWgPort *ebpf.Variable `ebpf:"map_key_wg_port"` + ProxyPort *ebpf.Variable `ebpf:"proxy_port"` + WgPort *ebpf.Variable `ebpf:"wg_port"` +} + // bpfPrograms contains all programs after they have been loaded into the kernel. // // It can be passed to loadBpfObjects or ebpf.CollectionSpec.LoadAndAssign. diff --git a/client/internal/ebpf/ebpf/bpf_bpfeb.o b/client/internal/ebpf/ebpf/bpf_bpfeb.o index 7433ad740..b435d4964 100644 Binary files a/client/internal/ebpf/ebpf/bpf_bpfeb.o and b/client/internal/ebpf/ebpf/bpf_bpfeb.o differ diff --git a/client/internal/ebpf/ebpf/bpf_bpfel.go b/client/internal/ebpf/ebpf/bpf_bpfel.go index 03b494aa2..f56efc901 100644 --- a/client/internal/ebpf/ebpf/bpf_bpfel.go +++ b/client/internal/ebpf/ebpf/bpf_bpfel.go @@ -1,5 +1,5 @@ // Code generated by bpf2go; DO NOT EDIT. -//go:build 386 || amd64 || amd64p32 || arm || arm64 || loong64 || mips64le || mips64p32le || mipsle || ppc64le || riscv64 +//go:build 386 || amd64 || arm || arm64 || loong64 || mips64le || mipsle || ppc64le || riscv64 || wasm package ebpf @@ -47,9 +47,10 @@ func loadBpfObjects(obj interface{}, opts *ebpf.CollectionOptions) error { type bpfSpecs struct { bpfProgramSpecs bpfMapSpecs + bpfVariableSpecs } -// bpfSpecs contains programs before they are loaded into the kernel. +// bpfProgramSpecs contains programs before they are loaded into the kernel. // // It can be passed ebpf.CollectionSpec.Assign. type bpfProgramSpecs struct { @@ -61,17 +62,28 @@ type bpfProgramSpecs struct { // 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"` } +// bpfVariableSpecs contains global variables before they are loaded into the kernel. +// +// It can be passed ebpf.CollectionSpec.Assign. +type bpfVariableSpecs struct { + FlagFeatureWgProxy *ebpf.VariableSpec `ebpf:"flag_feature_wg_proxy"` + MapKeyFeatures *ebpf.VariableSpec `ebpf:"map_key_features"` + MapKeyProxyPort *ebpf.VariableSpec `ebpf:"map_key_proxy_port"` + MapKeyWgPort *ebpf.VariableSpec `ebpf:"map_key_wg_port"` + ProxyPort *ebpf.VariableSpec `ebpf:"proxy_port"` + WgPort *ebpf.VariableSpec `ebpf:"wg_port"` +} + // 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 + bpfVariables } func (o *bpfObjects) Close() error { @@ -86,20 +98,28 @@ 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, ) } +// bpfVariables contains all global variables after they have been loaded into the kernel. +// +// It can be passed to loadBpfObjects or ebpf.CollectionSpec.LoadAndAssign. +type bpfVariables struct { + FlagFeatureWgProxy *ebpf.Variable `ebpf:"flag_feature_wg_proxy"` + MapKeyFeatures *ebpf.Variable `ebpf:"map_key_features"` + MapKeyProxyPort *ebpf.Variable `ebpf:"map_key_proxy_port"` + MapKeyWgPort *ebpf.Variable `ebpf:"map_key_wg_port"` + ProxyPort *ebpf.Variable `ebpf:"proxy_port"` + WgPort *ebpf.Variable `ebpf:"wg_port"` +} + // bpfPrograms contains all programs after they have been loaded into the kernel. // // It can be passed to loadBpfObjects or ebpf.CollectionSpec.LoadAndAssign. diff --git a/client/internal/ebpf/ebpf/bpf_bpfel.o b/client/internal/ebpf/ebpf/bpf_bpfel.o index 779f43a00..a388b6d6d 100644 Binary files a/client/internal/ebpf/ebpf/bpf_bpfel.o and b/client/internal/ebpf/ebpf/bpf_bpfel.o differ diff --git a/client/internal/ebpf/ebpf/dns_fwd_linux.go b/client/internal/ebpf/ebpf/dns_fwd_linux.go deleted file mode 100644 index 1e7774573..000000000 --- a/client/internal/ebpf/ebpf/dns_fwd_linux.go +++ /dev/null @@ -1,52 +0,0 @@ -package ebpf - -import ( - "encoding/binary" - "fmt" - "net/netip" - - log "github.com/sirupsen/logrus" -) - -const ( - mapKeyDNSIP uint32 = 0 - mapKeyDNSPort uint32 = 1 -) - -func (tf *GeneralManager) LoadDNSFwd(ip netip.Addr, dnsPort int) error { - log.Debugf("load eBPF DNS forwarder, watching addr: %s:53, redirect to port: %d", ip, dnsPort) - tf.lock.Lock() - defer tf.lock.Unlock() - - err := tf.loadXdp() - if err != nil { - return err - } - - if !ip.Is4() { - return fmt.Errorf("eBPF DNS forwarder only supports IPv4, got %s", ip) - } - ip4 := ip.As4() - err = tf.bpfObjs.NbMapDnsIp.Put(mapKeyDNSIP, binary.BigEndian.Uint32(ip4[:])) - 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) -} - diff --git a/client/internal/ebpf/ebpf/manager_linux.go b/client/internal/ebpf/ebpf/manager_linux.go index 7520a6387..a13f5f19a 100644 --- a/client/internal/ebpf/ebpf/manager_linux.go +++ b/client/internal/ebpf/ebpf/manager_linux.go @@ -15,8 +15,7 @@ import ( const ( mapKeyFeatures uint32 = 0 - featureFlagWGProxy = 0b00000001 - featureFlagDnsForwarder = 0b00000010 + featureFlagWGProxy = 0b00000001 ) var ( @@ -28,9 +27,9 @@ var ( // 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). +// When packet arrives, the C code checks for each feature (if it is set) and executes each enabled program (e.g., 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 +//go:generate go run github.com/cilium/ebpf/cmd/bpf2go -cc clang-14 bpf src/prog.c -- -I /usr/x86_64-linux-gnu/include -include src/bpf_map_def.h type GeneralManager struct { lock sync.Mutex link link.Link diff --git a/client/internal/ebpf/ebpf/manager_linux_test.go b/client/internal/ebpf/ebpf/manager_linux_test.go index 5664a4565..e09fcb977 100644 --- a/client/internal/ebpf/ebpf/manager_linux_test.go +++ b/client/internal/ebpf/ebpf/manager_linux_test.go @@ -7,33 +7,24 @@ import ( func TestManager_setFeatureFlag(t *testing.T) { mgr := GeneralManager{} mgr.setFeatureFlag(featureFlagWGProxy) - if mgr.featureFlags != 1 { + if mgr.featureFlags != featureFlagWGProxy { t.Errorf("invalid feature state") } - mgr.setFeatureFlag(featureFlagDnsForwarder) - if mgr.featureFlags != 3 { - t.Errorf("invalid feature state") + mgr.setFeatureFlag(featureFlagWGProxy) + if mgr.featureFlags != featureFlagWGProxy { + t.Errorf("setting a flag twice must be idempotent, got: %d", mgr.featureFlags) } } 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 feature 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 feature state, expected: %d, got: %d", 0, mgr.featureFlags) } diff --git a/client/internal/ebpf/ebpf/src/bpf_map_def.h b/client/internal/ebpf/ebpf/src/bpf_map_def.h new file mode 100644 index 000000000..9528fb592 --- /dev/null +++ b/client/internal/ebpf/ebpf/src/bpf_map_def.h @@ -0,0 +1,16 @@ +// libbpf 1.0 removed struct bpf_map_def, but the programs here keep the legacy +// map definitions: they load on kernels built without BTF, which BTF-style +// (SEC(".maps")) definitions do not. Define the struct ourselves so the +// programs compile against current libbpf headers. +#ifndef NB_BPF_MAP_DEF_H +#define NB_BPF_MAP_DEF_H + +struct bpf_map_def { + unsigned int type; + unsigned int key_size; + unsigned int value_size; + unsigned int max_entries; + unsigned int map_flags; +}; + +#endif diff --git a/client/internal/ebpf/ebpf/src/dns_fwd.c b/client/internal/ebpf/ebpf/src/dns_fwd.c deleted file mode 100644 index 9f8de2001..000000000 --- a/client/internal/ebpf/ebpf/src/dns_fwd.c +++ /dev/null @@ -1,67 +0,0 @@ -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; - // Clear the now-stale checksum; zero means "not computed" for IPv4. - udp->check = 0; - return XDP_PASS; - } - - if (udp->source == dns_port && ip->saddr == dns_ip) { - udp->source = GENERAL_DNS_PORT; - udp->check = 0; - return XDP_PASS; - } - - return XDP_PASS; -} diff --git a/client/internal/ebpf/ebpf/src/prog.c b/client/internal/ebpf/ebpf/src/prog.c index f32103f28..44ee53458 100644 --- a/client/internal/ebpf/ebpf/src/prog.c +++ b/client/internal/ebpf/ebpf/src/prog.c @@ -5,11 +5,9 @@ #include #include #include -#include "dns_fwd.c" #include "wg_proxy.c" 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 = { @@ -48,10 +46,6 @@ int nb_xdp_prog(struct xdp_md *ctx) { 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); } diff --git a/client/internal/ebpf/ebpf/src/readme.md b/client/internal/ebpf/ebpf/src/readme.md index 0ab393dd4..aa47847da 100644 --- a/client/internal/ebpf/ebpf/src/readme.md +++ b/client/internal/ebpf/ebpf/src/readme.md @@ -1,8 +1,18 @@ -# DNS forwarder +# XDP programs -The agent attach the XDP program to the lo device. We can not use fake address in eBPF because the -traffic does not appear in the eBPF program. The program capture the traffic on wg_ip:53 and -overwrite in it the destination port to 5053. +`prog.c` is attached to the `lo` device and dispatches to the features enabled in the +`nb_features` map. The only feature is the WireGuard proxy (`wg_proxy.c`): it rewrites +loopback UDP sent from the WireGuard listen port so it reaches the userspace relay proxy +port instead, and swaps the peer endpoint port into the source so the proxy can tell +peers apart. + +Maps use the legacy `struct bpf_map_def` form, defined in `bpf_map_def.h` because libbpf +1.0 removed it. They load on kernels built without BTF, which BTF-style (`SEC(".maps")`) +definitions do not. + +Regenerate the objects with `go generate ./client/internal/ebpf/ebpf/`; it needs +`clang-14`. Loading a regenerated object needs root, attaching it needs `bpf_link` +(kernel >= 5.7), and only one XDP program can own `lo` at a time. # Debug diff --git a/client/internal/ebpf/manager/manager.go b/client/internal/ebpf/manager/manager.go index 25a767090..fdc5d8d82 100644 --- a/client/internal/ebpf/manager/manager.go +++ b/client/internal/ebpf/manager/manager.go @@ -1,11 +1,7 @@ package manager -import "net/netip" - -// Manager is used to load multiple eBPF programs. E.g., current DNS programs and WireGuard proxy +// Manager is used to load multiple eBPF programs. E.g., the WireGuard proxy type Manager interface { - LoadDNSFwd(ip netip.Addr, dnsPort int) error - FreeDNSFwd() error LoadWgProxy(proxyPort, wgPort int) error FreeWGProxy() error }