[cllient] Don't track ebpf traffic in conntrack (#5166)

client/firewall/iptables/manager_linux.go

@@ -83,6 +83,10 @@ func (m *Manager) Init(stateManager *statemanager.Manager) error {
 		return fmt.Errorf("acl manager init: %w", err)
 	}
 
+	if err := m.initNoTrackChain(); err != nil {
+		return fmt.Errorf("init notrack chain: %w", err)
+	}
+
 	// persist early to ensure cleanup of chains
 	go func() {
 		if err := stateManager.PersistState(context.Background()); err != nil {
@@ -177,6 +181,10 @@ func (m *Manager) Close(stateManager *statemanager.Manager) error {
 
 	var merr *multierror.Error
 
+	if err := m.cleanupNoTrackChain(); err != nil {
+		merr = multierror.Append(merr, fmt.Errorf("cleanup notrack chain: %w", err))
+	}
+
 	if err := m.aclMgr.Reset(); err != nil {
 		merr = multierror.Append(merr, fmt.Errorf("reset acl manager: %w", err))
 	}
@@ -277,6 +285,125 @@ func (m *Manager) RemoveInboundDNAT(localAddr netip.Addr, protocol firewall.Prot
 	return m.router.RemoveInboundDNAT(localAddr, protocol, sourcePort, targetPort)
 }
 
+const (
+	chainNameRaw = "NETBIRD-RAW"
+	chainOUTPUT  = "OUTPUT"
+	tableRaw     = "raw"
+)
+
+// SetupEBPFProxyNoTrack creates notrack rules for eBPF proxy loopback traffic.
+// This prevents conntrack from tracking WireGuard proxy traffic on loopback, which
+// can interfere with MASQUERADE rules (e.g., from container runtimes like Podman/netavark).
+//
+// Traffic flows that need NOTRACK:
+//
+//  1. Egress: WireGuard -> fake endpoint (before eBPF rewrite)
+//     src=127.0.0.1:wgPort -> dst=127.0.0.1:fakePort
+//     Matched by: sport=wgPort
+//
+//  2. Egress: Proxy -> WireGuard (via raw socket)
+//     src=127.0.0.1:fakePort -> dst=127.0.0.1:wgPort
+//     Matched by: dport=wgPort
+//
+//  3. Ingress: Packets to WireGuard
+//     dst=127.0.0.1:wgPort
+//     Matched by: dport=wgPort
+//
+//  4. Ingress: Packets to proxy (after eBPF rewrite)
+//     dst=127.0.0.1:proxyPort
+//     Matched by: dport=proxyPort
+//
+// Rules are cleaned up when the firewall manager is closed.
+func (m *Manager) SetupEBPFProxyNoTrack(proxyPort, wgPort uint16) error {
+	m.mutex.Lock()
+	defer m.mutex.Unlock()
+
+	wgPortStr := fmt.Sprintf("%d", wgPort)
+	proxyPortStr := fmt.Sprintf("%d", proxyPort)
+
+	// Egress rules: match outgoing loopback UDP packets
+	outputRuleSport := []string{"-o", "lo", "-s", "127.0.0.1", "-d", "127.0.0.1", "-p", "udp", "--sport", wgPortStr, "-j", "NOTRACK"}
+	if err := m.ipv4Client.AppendUnique(tableRaw, chainNameRaw, outputRuleSport...); err != nil {
+		return fmt.Errorf("add output sport notrack rule: %w", err)
+	}
+
+	outputRuleDport := []string{"-o", "lo", "-s", "127.0.0.1", "-d", "127.0.0.1", "-p", "udp", "--dport", wgPortStr, "-j", "NOTRACK"}
+	if err := m.ipv4Client.AppendUnique(tableRaw, chainNameRaw, outputRuleDport...); err != nil {
+		return fmt.Errorf("add output dport notrack rule: %w", err)
+	}
+
+	// Ingress rules: match incoming loopback UDP packets
+	preroutingRuleWg := []string{"-i", "lo", "-s", "127.0.0.1", "-d", "127.0.0.1", "-p", "udp", "--dport", wgPortStr, "-j", "NOTRACK"}
+	if err := m.ipv4Client.AppendUnique(tableRaw, chainNameRaw, preroutingRuleWg...); err != nil {
+		return fmt.Errorf("add prerouting wg notrack rule: %w", err)
+	}
+
+	preroutingRuleProxy := []string{"-i", "lo", "-s", "127.0.0.1", "-d", "127.0.0.1", "-p", "udp", "--dport", proxyPortStr, "-j", "NOTRACK"}
+	if err := m.ipv4Client.AppendUnique(tableRaw, chainNameRaw, preroutingRuleProxy...); err != nil {
+		return fmt.Errorf("add prerouting proxy notrack rule: %w", err)
+	}
+
+	log.Debugf("set up ebpf proxy notrack rules for ports %d,%d", proxyPort, wgPort)
+	return nil
+}
+
+func (m *Manager) initNoTrackChain() error {
+	if err := m.cleanupNoTrackChain(); err != nil {
+		log.Debugf("cleanup notrack chain: %v", err)
+	}
+
+	if err := m.ipv4Client.NewChain(tableRaw, chainNameRaw); err != nil {
+		return fmt.Errorf("create chain: %w", err)
+	}
+
+	jumpRule := []string{"-j", chainNameRaw}
+
+	if err := m.ipv4Client.InsertUnique(tableRaw, chainOUTPUT, 1, jumpRule...); err != nil {
+		if delErr := m.ipv4Client.DeleteChain(tableRaw, chainNameRaw); delErr != nil {
+			log.Debugf("delete orphan chain: %v", delErr)
+		}
+		return fmt.Errorf("add output jump rule: %w", err)
+	}
+
+	if err := m.ipv4Client.InsertUnique(tableRaw, chainPREROUTING, 1, jumpRule...); err != nil {
+		if delErr := m.ipv4Client.DeleteIfExists(tableRaw, chainOUTPUT, jumpRule...); delErr != nil {
+			log.Debugf("delete output jump rule: %v", delErr)
+		}
+		if delErr := m.ipv4Client.DeleteChain(tableRaw, chainNameRaw); delErr != nil {
+			log.Debugf("delete orphan chain: %v", delErr)
+		}
+		return fmt.Errorf("add prerouting jump rule: %w", err)
+	}
+
+	return nil
+}
+
+func (m *Manager) cleanupNoTrackChain() error {
+	exists, err := m.ipv4Client.ChainExists(tableRaw, chainNameRaw)
+	if err != nil {
+		return fmt.Errorf("check chain exists: %w", err)
+	}
+	if !exists {
+		return nil
+	}
+
+	jumpRule := []string{"-j", chainNameRaw}
+
+	if err := m.ipv4Client.DeleteIfExists(tableRaw, chainOUTPUT, jumpRule...); err != nil {
+		return fmt.Errorf("remove output jump rule: %w", err)
+	}
+
+	if err := m.ipv4Client.DeleteIfExists(tableRaw, chainPREROUTING, jumpRule...); err != nil {
+		return fmt.Errorf("remove prerouting jump rule: %w", err)
+	}
+
+	if err := m.ipv4Client.ClearAndDeleteChain(tableRaw, chainNameRaw); err != nil {
+		return fmt.Errorf("clear and delete chain: %w", err)
+	}
+
+	return nil
+}
+
 func getConntrackEstablished() []string {
 	return []string{"-m", "conntrack", "--ctstate", "RELATED,ESTABLISHED", "-j", "ACCEPT"}
 }