Attach conntrack helpers via ct helper objects

Reviewed-on: #23

go.mod

@@ -3,19 +3,18 @@ module git.unkin.net/unkin/tomswall
 go 1.23
 
 require (
-	github.com/google/nftables v0.2.0
-	github.com/mdlayher/netlink v1.7.2
+	github.com/google/nftables v0.3.0
+	github.com/mdlayher/netlink v1.7.3-0.20250113171957-fbb4dce95f42
 	github.com/spf13/cobra v1.8.1
-	golang.org/x/sys v0.18.0
+	golang.org/x/sys v0.28.0
 	gopkg.in/yaml.v3 v3.0.1
 )
 
 require (
 	github.com/google/go-cmp v0.6.0 // indirect
 	github.com/inconshreveable/mousetrap v1.1.0 // indirect
-	github.com/josharian/native v1.1.0 // indirect
 	github.com/mdlayher/socket v0.5.1 // indirect
 	github.com/spf13/pflag v1.0.5 // indirect
-	golang.org/x/net v0.23.0 // indirect
+	golang.org/x/net v0.33.0 // indirect
 	golang.org/x/sync v0.6.0 // indirect
 )

go.sum

@@ -1,14 +1,12 @@
 github.com/cpuguy83/go-md2man/v2 v2.0.4/go.mod h1:tgQtvFlXSQOSOSIRvRPT7W67SCa46tRHOmNcaadrF8o=
 github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
 github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
-github.com/google/nftables v0.2.0 h1:PbJwaBmbVLzpeldoeUKGkE2RjstrjPKMl6oLrfEJ6/8=
-github.com/google/nftables v0.2.0/go.mod h1:Beg6V6zZ3oEn0JuiUQ4wqwuyqqzasOltcoXPtgLbFp4=
+github.com/google/nftables v0.3.0 h1:bkyZ0cbpVeMHXOrtlFc8ISmfVqq5gPJukoYieyVmITg=
+github.com/google/nftables v0.3.0/go.mod h1:BCp9FsrbF1Fn/Yu6CLUc9GGZFw/+hsxfluNXXmxBfRM=
 github.com/inconshreveable/mousetrap v1.1.0 h1:wN+x4NVGpMsO7ErUn/mUI3vEoE6Jt13X2s0bqwp9tc8=
 github.com/inconshreveable/mousetrap v1.1.0/go.mod h1:vpF70FUmC8bwa3OWnCshd2FqLfsEA9PFc4w1p2J65bw=
-github.com/josharian/native v1.1.0 h1:uuaP0hAbW7Y4l0ZRQ6C9zfb7Mg1mbFKry/xzDAfmtLA=
-github.com/josharian/native v1.1.0/go.mod h1:7X/raswPFr05uY3HiLlYeyQntB6OO7E/d2Cu7qoaN2w=
-github.com/mdlayher/netlink v1.7.2 h1:/UtM3ofJap7Vl4QWCPDGXY8d3GIY2UGSDbK+QWmY8/g=
-github.com/mdlayher/netlink v1.7.2/go.mod h1:xraEF7uJbxLhc5fpHL4cPe221LI2bdttWlU+ZGLfQSw=
+github.com/mdlayher/netlink v1.7.3-0.20250113171957-fbb4dce95f42 h1:A1Cq6Ysb0GM0tpKMbdCXCIfBclan4oHk1Jb+Hrejirg=
+github.com/mdlayher/netlink v1.7.3-0.20250113171957-fbb4dce95f42/go.mod h1:BB4YCPDOzfy7FniQ/lxuYQ3dgmM2cZumHbK8RpTjN2o=
 github.com/mdlayher/socket v0.5.1 h1:VZaqt6RkGkt2OE9l3GcC6nZkqD3xKeQLyfleW/uBcos=
 github.com/mdlayher/socket v0.5.1/go.mod h1:TjPLHI1UgwEv5J1B5q0zTZq12A/6H7nKmtTanQE37IQ=
 github.com/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
@@ -16,14 +14,14 @@ github.com/spf13/cobra v1.8.1 h1:e5/vxKd/rZsfSJMUX1agtjeTDf+qv1/JdBF8gg5k9ZM=
 github.com/spf13/cobra v1.8.1/go.mod h1:wHxEcudfqmLYa8iTfL+OuZPbBZkmvliBWKIezN3kD9Y=
 github.com/spf13/pflag v1.0.5 h1:iy+VFUOCP1a+8yFto/drg2CJ5u0yRoB7fZw3DKv/JXA=
 github.com/spf13/pflag v1.0.5/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
-github.com/vishvananda/netns v0.0.0-20180720170159-13995c7128cc h1:R83G5ikgLMxrBvLh22JhdfI8K6YXEPHx5P03Uu3DRs4=
-github.com/vishvananda/netns v0.0.0-20180720170159-13995c7128cc/go.mod h1:ZjcWmFBXmLKZu9Nxj3WKYEafiSqer2rnvPr0en9UNpI=
-golang.org/x/net v0.23.0 h1:7EYJ93RZ9vYSZAIb2x3lnuvqO5zneoD6IvWjuhfxjTs=
-golang.org/x/net v0.23.0/go.mod h1:JKghWKKOSdJwpW2GEx0Ja7fmaKnMsbu+MWVZTokSYmg=
+github.com/vishvananda/netns v0.0.4 h1:Oeaw1EM2JMxD51g9uhtC0D7erkIjgmj8+JZc26m1YX8=
+github.com/vishvananda/netns v0.0.4/go.mod h1:SpkAiCQRtJ6TvvxPnOSyH3BMl6unz3xZlaprSwhNNJM=
+golang.org/x/net v0.33.0 h1:74SYHlV8BIgHIFC/LrYkOGIwL19eTYXQ5wc6TBuO36I=
+golang.org/x/net v0.33.0/go.mod h1:HXLR5J+9DxmrqMwG9qjGCxZ+zKXxBru04zlTvWlWuN4=
 golang.org/x/sync v0.6.0 h1:5BMeUDZ7vkXGfEr1x9B4bRcTH4lpkTkpdh0T/J+qjbQ=
 golang.org/x/sync v0.6.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
-golang.org/x/sys v0.18.0 h1:DBdB3niSjOA/O0blCZBqDefyWNYveAYMNF1Wum0DYQ4=
-golang.org/x/sys v0.18.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/sys v0.28.0 h1:Fksou7UEQUWlKvIdsqzJmUmCX3cZuD2+P3XyyzwMhlA=
+golang.org/x/sys v0.28.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=

internal/nftables/compiler.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"log/slog"
 	"net"
+	"slices"
 	"sort"
 	"strconv"
 	"strings"
@@ -205,16 +206,81 @@ func (c *Compiler) compileBlrules(state *FirewallState) error {
 		}
 		if err := c.compileOneRule(state, tag, rule.Source, rule.Dest,
 			rule.Proto, rule.DPort, rule.SPort,
-			action, rule.Log, "", fwZone, ""); err != nil {
+			action, rule.Log, "", "", fwZone, ""); err != nil {
 			return fmt.Errorf("blrule[%d]: %w", i, err)
 		}
 	}
 	return nil
 }
 
+// helperProtos is each kernel helper's default transport, used when an entry gives no proto.
+var helperProtos = map[string]string{
+	"amanda": "udp", "ftp": "tcp", "irc": "tcp", "netbios-ns": "udp", "pptp": "tcp",
+	"Q.931": "tcp", "RAS": "udp", "sane": "tcp", "sip": "udp", "snmp": "udp", "tftp": "udp",
+}
+
+// compileHelper declares a ct helper object per (helper, proto) and assigns it
+// after conntrack (-200) has created the entry; a raw-priority assignment is a no-op.
+func (c *Compiler) compileHelper(state *FirewallState, tag string, ct config.ConntrackRule) error {
+	if ct.Source != "" || ct.Dest != "" {
+		slog.Warn("conntrack helper source/dest not supported, assigning globally", "rule", tag, "helper", ct.Helper)
+	}
+	chains := []string{"helper_prerouting", "helper_output"}
+	switch ct.Chain {
+	case config.ConntrackPrerouting:
+		chains = chains[:1]
+	case config.ConntrackOutput:
+		chains = chains[1:]
+	}
+
+	proto := ct.Proto
+	if proto == "" {
+		if proto = helperProtos[ct.Helper]; proto == "" {
+			return fmt.Errorf("proto required for helper %q", ct.Helper)
+		}
+	}
+	for _, p := range strings.Split(proto, ",") {
+		p = strings.TrimSpace(p)
+		n, err := protoNumber(p)
+		if err != nil {
+			return err
+		}
+		name := ct.Helper
+		if p != helperProtos[ct.Helper] {
+			name += "-" + p
+		}
+		if !slices.ContainsFunc(state.Helpers, func(h Helper) bool { return h.Name == name }) {
+			state.Helpers = append(state.Helpers, Helper{Name: name,
+				Helper: expr.CtHelper{Name: ct.Helper, L3Proto: unix.NFPROTO_INET, L4Proto: n}})
+		}
+
+		matches, err := l4Matches(p, ct.DPort, ct.SPort)
+		if err != nil {
+			return err
+		}
+		for _, chain := range chains {
+			for _, m := range matches {
+				state.Rules[chain] = append(state.Rules[chain], ManagedRule{
+					Chain: chain,
+					Exprs: append(append([]expr.Any{}, m.exprs...),
+						&expr.Objref{Type: unix.NFT_OBJECT_CT_HELPER, Name: name}),
+					Tag: tag + ":" + chain,
+				})
+			}
+		}
+	}
+	return nil
+}
+
 func (c *Compiler) compileConntrack(state *FirewallState) error {
 	for i, ct := range c.cfg.Conntrack {
 		tag := fmt.Sprintf("conntrack:%d", i)
+		if ct.Action == config.ConntrackHelper {
+			if err := c.compileHelper(state, tag, ct); err != nil {
+				return fmt.Errorf("conntrack[%d]: %w", i, err)
+			}
+			continue
+		}
 
 		chains := []string{"prerouting"}
 		switch ct.Chain {
@@ -236,8 +302,6 @@ func (c *Compiler) compileConntrack(state *FirewallState) error {
 				switch ct.Action {
 				case config.ConntrackNoTrack:
 					exprs = append(exprs, &expr.Notrack{})
-				case config.ConntrackHelper:
-					continue
 				case config.ConntrackDrop:
 					exprs = append(exprs, &expr.Verdict{Kind: expr.VerdictDrop})
 				}
@@ -276,14 +340,14 @@ func (c *Compiler) compileRules(state *FirewallState) error {
 			if err != nil {
 				return fmt.Errorf("rule[%d]: %w", i, err)
 			}
-			if len(matches)*specCount(rule.Source, rule.Dest, rule.Action) > 1 {
+			if len(matches)*specCount(rule.Source, rule.Dest, rule.OrigDest, rule.Action) > 1 {
 				return fmt.Errorf("rule[%d]: ratelimit/connlimit cannot be combined with proto, port, zone or address lists (each expanded rule would get its own limiter)", i)
 			}
 		}
 
 		if err := c.compileOneRule(state, tag, rule.Source, rule.Dest,
 			proto, dports, sport,
-			rule.Action, rule.Log, rule.Dest, fwZone, rule.Section); err != nil {
+			rule.Action, rule.Log, rule.Dest, rule.OrigDest, fwZone, rule.Section); err != nil {
 			return fmt.Errorf("rule[%d]: %w", i, err)
 		}
 
@@ -360,22 +424,24 @@ func (c *Compiler) applyChainExtras(state *FirewallState, chain, tag string, rul
 
 func (c *Compiler) compileOneRule(state *FirewallState, tag, srcSpec, dstSpec, proto string,
 	dports, sports config.PortSpec, action config.RuleAction, logLevel string,
-	dnatDest string, fwZone string, section config.RuleSection) error {
+	dnatDest, origDest string, fwZone string, section config.RuleSection) error {
 
 	for _, src := range zoneSpecs(srcSpec) {
 		for _, srcAddr := range splitAddrs(src.Addr) {
-			if action == config.RuleDNAT || action == config.RuleRedirect {
-				if err := c.compileDNATRule(state, tag, src.Zone, srcAddr, dstSpec, proto, dports, action, logLevel); err != nil {
-					return err
-				}
-				continue
-			}
-			for _, dst := range zoneSpecs(dstSpec) {
-				for _, dstAddr := range splitAddrs(dst.Addr) {
-					if err := c.compileZonePair(state, tag, src.Zone, srcAddr, dst.Zone, dstAddr, proto,
-						dports, sports, action, logLevel, fwZone, section); err != nil {
+			for _, od := range splitAddrs(origDest) {
+				if action == config.RuleDNAT || action == config.RuleRedirect {
+					if err := c.compileDNATRule(state, tag, src.Zone, srcAddr, od, dstSpec, proto, dports, action, logLevel); err != nil {
 						return err
 					}
+					continue
+				}
+				for _, dst := range zoneSpecs(dstSpec) {
+					for _, dstAddr := range splitAddrs(dst.Addr) {
+						if err := c.compileZonePair(state, tag, src.Zone, srcAddr, dst.Zone, dstAddr, od, proto,
+							dports, sports, action, logLevel, fwZone, section); err != nil {
+							return err
+						}
+					}
 				}
 			}
 		}
@@ -384,17 +450,18 @@ func (c *Compiler) compileOneRule(state *FirewallState, tag, srcSpec, dstSpec, p
 }
 
 // specCount is how many zone/address combinations compileOneRule expands src and dst into.
-func specCount(srcSpec, dstSpec string, action config.RuleAction) int {
+func specCount(srcSpec, dstSpec, origDest string, action config.RuleAction) int {
 	count := func(spec string) (n int) {
 		for _, z := range zoneSpecs(spec) {
 			n += len(splitAddrs(z.Addr))
 		}
 		return n
 	}
+	n := count(srcSpec) * len(splitAddrs(origDest))
 	if action == config.RuleDNAT || action == config.RuleRedirect {
-		return count(srcSpec)
+		return n
 	}
-	return count(srcSpec) * count(dstSpec)
+	return n * count(dstSpec)
 }
 
 // zoneSpecs expands a comma zone list; "all"/"any" forms keep their own comma (exclusion) syntax.
@@ -414,12 +481,16 @@ func splitAddrs(addr string) []string {
 	return strings.Split(addr, ",")
 }
 
-func (c *Compiler) compileZonePair(state *FirewallState, tag, srcZone, srcAddr, dstZone, dstAddr, proto string,
+func (c *Compiler) compileZonePair(state *FirewallState, tag, srcZone, srcAddr, dstZone, dstAddr, origDest, proto string,
 	dports, sports config.PortSpec, action config.RuleAction, logLevel string,
 	fwZone string, section config.RuleSection) error {
-	srcIfaces := c.resolveZoneInterfaces(srcZone)
-	dstIfaces := c.resolveZoneInterfaces(dstZone)
+	srcIfaces := c.resolveZoneInterfaces(srcZone, srcAddr)
+	dstIfaces := c.resolveZoneInterfaces(dstZone, dstAddr)
 	chain := c.selectChain(srcZone, dstZone, fwZone)
+	// ponytail: forward daddr is post-DNAT; lift with `ct original daddr` (expr.Ct Direction, google/nftables v0.3.0).
+	if origDest != "" && chain == "forward" {
+		return fmt.Errorf("origdest: ORIGDEST on forwarded rules is not supported yet")
+	}
 
 	for _, srcIface := range srcIfaces {
 		for _, dstIface := range dstIfaces {
@@ -427,6 +498,15 @@ func (c *Compiler) compileZonePair(state *FirewallState, tag, srcZone, srcAddr,
 			if err != nil {
 				return err
 			}
+			if origDest != "" {
+				od, err := matchOrigDest(origDest)
+				if err != nil {
+					return fmt.Errorf("origdest: %w", err)
+				}
+				for i := range matches {
+					matches[i].exprs = append(matches[i].exprs, od...)
+				}
+			}
 
 			for _, m := range matches {
 				exprs := m.exprs
@@ -455,7 +535,7 @@ func (c *Compiler) compileZonePair(state *FirewallState, tag, srcZone, srcAddr,
 	return nil
 }
 
-func (c *Compiler) compileDNATRule(state *FirewallState, tag, srcZone, srcAddr, dstSpec, proto string,
+func (c *Compiler) compileDNATRule(state *FirewallState, tag, srcZone, srcAddr, origDest, dstSpec, proto string,
 	dports config.PortSpec, action config.RuleAction, logLevel string) error {
 	chain := "prerouting"
 
@@ -474,7 +554,15 @@ func (c *Compiler) compileDNATRule(state *FirewallState, tag, srcZone, srcAddr,
 		dnatPort = uint16(p)
 	}
 
-	srcIfaces := c.resolveZoneInterfaces(srcZone)
+	srcIfaces := c.resolveZoneInterfaces(srcZone, srcAddr)
+
+	var odExprs []expr.Any
+	if origDest != "" {
+		var err error
+		if odExprs, err = matchOrigDest(origDest); err != nil {
+			return fmt.Errorf("origdest: %w", err)
+		}
+	}
 
 	matches, err := l4Matches(proto, dports, nil)
 	if err != nil {
@@ -501,6 +589,7 @@ func (c *Compiler) compileDNATRule(state *FirewallState, tag, srcZone, srcAddr,
 				}
 				exprs = append(exprs, src...)
 			}
+			exprs = append(exprs, odExprs...)
 
 			exprs = append(exprs, m.exprs...)
 
@@ -538,6 +627,7 @@ func (c *Compiler) compileDNATRule(state *FirewallState, tag, srcZone, srcAddr,
 						)
 						natExpr.RegProtoMin = 2
 						natExpr.RegProtoMax = 2
+						natExpr.Specified = true
 					}
 					exprs = append(exprs, natExpr)
 				} else {
@@ -558,6 +648,7 @@ func (c *Compiler) compileDNATRule(state *FirewallState, tag, srcZone, srcAddr,
 						)
 						natExpr.RegProtoMin = 2
 						natExpr.RegProtoMax = 2
+						natExpr.Specified = true
 					}
 					exprs = append(exprs, natExpr)
 				}
@@ -589,8 +680,8 @@ func (c *Compiler) compilePolicies(state *FirewallState) error {
 				}
 
 				chain := c.selectChain(sz, dz, fwZone)
-				srcIfaces := c.resolveZoneInterfaces(sz)
-				dstIfaces := c.resolveZoneInterfaces(dz)
+				srcIfaces := c.resolveZoneInterfaces(sz, "")
+				dstIfaces := c.resolveZoneInterfaces(dz, "")
 
 				for _, si := range srcIfaces {
 					for _, di := range dstIfaces {
@@ -599,7 +690,7 @@ func (c *Compiler) compilePolicies(state *FirewallState) error {
 						if si != "" {
 							exprs = append(exprs, matchIfaceName(true, si)...)
 						}
-						if di != "" && chain == "forward" {
+						if di != "" && chain != "input" {
 							exprs = append(exprs, matchIfaceName(false, di)...)
 						}
 
@@ -932,34 +1023,25 @@ func (c *Compiler) selectChain(srcZone, dstZone, fwZone string) string {
 	return "forward"
 }
 
-func (c *Compiler) resolveZoneInterfaces(zone string) []string {
-	if zone == "all" || zone == "" {
+// resolveZoneInterfaces returns nil (fail closed) for a zone with no interfaces unless a non-negated address match narrows the rule.
+func (c *Compiler) resolveZoneInterfaces(zone, addr string) []string {
+	if z, ok := c.cfg.Zones[zone]; !ok || z.Type == config.ZoneFirewall {
 		return []string{""}
 	}
-	ifaces := c.cfg.ZoneInterfaces(zone)
-	if len(ifaces) > 0 {
+	if ifaces := c.cfg.ZoneInterfaces(zone); len(ifaces) > 0 {
 		return ifaces
 	}
-	if z, ok := c.cfg.Zones[zone]; ok && z.Type == config.ZoneIP && !c.zoneHasHosts(zone) {
-		if !c.warned[zone] {
-			if c.warned == nil {
-				c.warned = map[string]bool{}
-			}
-			c.warned[zone] = true
-			slog.Warn("compiler: zone has no interfaces, skipping its rules", "zone", zone)
-		}
-		return nil
+	if addr != "" && !strings.HasPrefix(addr, "!") {
+		return []string{""}
 	}
-	return []string{""}
-}
-
-func (c *Compiler) zoneHasHosts(zone string) bool {
-	for _, h := range c.cfg.Hosts {
-		if h.Zone == zone {
-			return true
+	if !c.warned[zone] {
+		if c.warned == nil {
+			c.warned = map[string]bool{}
 		}
+		c.warned[zone] = true
+		slog.Warn("compiler: zone has no interfaces, skipping its rules", "zone", zone)
 	}
-	return false
+	return nil
 }
 
 func (c *Compiler) expandZoneRef(ref string) []string {
@@ -997,7 +1079,7 @@ func (c *Compiler) buildMatchExprs(srcIface, dstIface, chain, proto string, dpor
 	if srcIface != "" {
 		exprs = append(exprs, matchIfaceName(true, srcIface)...)
 	}
-	if dstIface != "" && chain == "forward" {
+	if dstIface != "" && chain != "input" {
 		exprs = append(exprs, matchIfaceName(false, dstIface)...)
 	}
 
@@ -1386,6 +1468,30 @@ func matchDestCIDR(cidr string) ([]expr.Any, error) {
 	return matchAddrCIDR(cidr, false)
 }
 
+// matchOrigDest guards the daddr match with the address's nfproto so it is family-correct in the inet table.
+func matchOrigDest(addr string) ([]expr.Any, error) {
+	var proto byte
+	for i, a := range strings.Split(strings.TrimPrefix(addr, "!"), ",") {
+		a, _, _ = strings.Cut(a, "/")
+		p := byte(unix.NFPROTO_IPV6)
+		if ip := net.ParseIP(a); ip != nil && ip.To4() != nil {
+			p = unix.NFPROTO_IPV4
+		}
+		if i > 0 && p != proto {
+			return nil, fmt.Errorf("%q mixes IPv4 and IPv6 addresses", addr)
+		}
+		proto = p
+	}
+	dst, err := matchDestCIDR(addr)
+	if err != nil {
+		return nil, err
+	}
+	return append([]expr.Any{
+		&expr.Meta{Key: expr.MetaKeyNFPROTO, Register: 1},
+		&expr.Cmp{Op: expr.CmpOpEq, Register: 1, Data: []byte{proto}},
+	}, dst...), nil
+}
+
 func matchAddrCIDR(cidr string, isSrc bool) ([]expr.Any, error) {
 	negated := false
 	if strings.HasPrefix(cidr, "!") {

internal/nftables/compiler_test.go

@@ -1,8 +1,11 @@
 package nftables
 
 import (
+	"bytes"
 	"encoding/binary"
 	"fmt"
+	"log/slog"
+	"net"
 	"reflect"
 	"strings"
 	"testing"
@@ -141,17 +144,17 @@ func TestCompiler_ResolveZoneInterfaces(t *testing.T) {
 	}
 	c := NewCompiler(cfg)
 
-	ifaces := c.resolveZoneInterfaces("net")
+	ifaces := c.resolveZoneInterfaces("net", "")
 	if len(ifaces) != 1 || ifaces[0] != "eth0" {
 		t.Errorf("resolveZoneInterfaces(net) = %v, want [eth0]", ifaces)
 	}
 
-	ifaces = c.resolveZoneInterfaces("all")
+	ifaces = c.resolveZoneInterfaces("all", "")
 	if len(ifaces) != 1 || ifaces[0] != "" {
 		t.Errorf("resolveZoneInterfaces(all) = %v, want [\"\"]", ifaces)
 	}
 
-	ifaces = c.resolveZoneInterfaces("fw")
+	ifaces = c.resolveZoneInterfaces("fw", "")
 	if len(ifaces) != 1 || ifaces[0] != "" {
 		t.Errorf("resolveZoneInterfaces(fw) = %v, want [\"\"]", ifaces)
 	}
@@ -453,15 +456,19 @@ func TestCompile_DNAT(t *testing.T) {
 		t.Fatalf("Compile() error: %v", err)
 	}
 
-	found := false
+	var nat *expr.NAT
 	for _, r := range state.Rules["prerouting"] {
 		if r.Tag == "rule:0" {
-			found = true
+			nat, _ = r.Exprs[len(r.Exprs)-1].(*expr.NAT)
 			break
 		}
 	}
-	if !found {
-		t.Error("no DNAT rule found in prerouting chain")
+	if nat == nil {
+		t.Fatal("no DNAT rule found in prerouting chain")
+	}
+	// The kernel reports PROTO_SPECIFIED whenever a port register is set.
+	if nat.RegProtoMin != 2 || !nat.Specified {
+		t.Errorf("DNAT with port must set RegProtoMin and Specified to match kernel readback, got %+v", nat)
 	}
 }
 
@@ -1758,6 +1765,83 @@ func TestCompile_PortAndProtoLists(t *testing.T) {
 	}
 }
 
+func TestCompile_OutputPolicyMatchesOif(t *testing.T) {
+	cfg := listCfg(func(c *config.Config) {
+		c.Zones["lan"] = config.Zone{Type: config.ZoneIP}
+		c.Interfaces = append(c.Interfaces, config.Interface{Zone: "lan", Interface: "eth1"})
+		c.Policy = []config.Policy{{Source: "fw", Dest: "lan", Action: config.PolicyAccept}}
+	})
+	got := taggedRules(mustCompile(t, cfg), "output", "policy:0")
+	if len(got) != 1 || describeRule(got[0]) != "oif=eth1" {
+		t.Fatalf("fw->lan policy = %v, want one rule oif=eth1", got)
+	}
+}
+
+func TestCompile_InterfacelessZonesFailClosed(t *testing.T) {
+	ipsec := func(c *config.Config) { c.Zones["ips"] = config.Zone{Type: config.ZoneIPSec} }
+	rule := func(dest string) func(*config.Config) {
+		return func(c *config.Config) {
+			ipsec(c)
+			c.Rules = []config.Rule{{Action: config.RuleAccept, Source: "fw", Dest: dest}}
+		}
+	}
+	tests := []struct {
+		name  string
+		mod   func(*config.Config)
+		tag   string
+		want  int
+		warns []string
+	}{
+		{"ipsec zone without interface", func(c *config.Config) {
+			ipsec(c)
+			c.Policy = []config.Policy{{Source: "fw", Dest: "ips", Action: config.PolicyAccept}}
+		}, "policy:0", 0, []string{"ips"}},
+		{"hosts-only zone", func(c *config.Config) {
+			c.Zones["hst"] = config.Zone{Type: config.ZoneIP}
+			c.Hosts = []config.Host{{Zone: "hst", Interface: "eth0", Addresses: []string{"192.0.2.0/24"}}}
+			c.Policy = []config.Policy{{Source: "fw", Dest: "hst", Action: config.PolicyAccept}}
+		}, "policy:0", 0, []string{"hst"}},
+		{"fw all expansion keeps zones with interfaces", func(c *config.Config) {
+			ipsec(c)
+			c.Zones["hst"] = config.Zone{Type: config.ZoneIP}
+			c.Hosts = []config.Host{{Zone: "hst", Interface: "eth0", Addresses: []string{"192.0.2.0/24"}}}
+			c.Policy = []config.Policy{{Source: "fw", Dest: "all", Action: config.PolicyDrop}}
+		}, "policy:0", 1, []string{"hst", "ips"}},
+		{"negated address does not scope", rule("ips:!192.0.2.1"), "rule:0", 0, []string{"ips"}},
+		{"address scopes", rule("ips:192.0.2.1"), "rule:0", 1, []string{"ips"}},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var logs bytes.Buffer
+			prev := slog.Default()
+			slog.SetDefault(slog.New(slog.NewTextHandler(&logs, nil)))
+			defer slog.SetDefault(prev)
+
+			state := mustCompile(t, listCfg(tt.mod))
+			got := 0
+			for chain := range state.Rules {
+				for _, r := range taggedRules(state, chain, tt.tag) {
+					got++
+					if describeRule(r) == "" {
+						t.Errorf("%s: un-scoped rule", chain)
+					}
+				}
+			}
+			if got != tt.want {
+				t.Errorf("got %d %s rules, want %d", got, tt.tag, tt.want)
+			}
+			if n := strings.Count(logs.String(), "zone has no interfaces"); n != len(tt.warns) {
+				t.Errorf("got %d warnings, want %d:\n%s", n, len(tt.warns), logs.String())
+			}
+			for _, z := range tt.warns {
+				if n := strings.Count(logs.String(), "zone="+z+"\n"); n != 1 {
+					t.Errorf("zone %s warned %d times, want 1", z, n)
+				}
+			}
+		})
+	}
+}
+
 // describeRule renders a rule's iif/oif/saddr/daddr matches, e.g. "iif=eth1 oif=eth2 daddr=192.0.2.1".
 func describeRule(r ManagedRule) string {
 	var parts []string
@@ -1781,12 +1865,12 @@ func describeRule(r ManagedRule) string {
 				parts = append(parts, "oif="+strings.TrimRight(string(cmp.Data), "\x00"))
 			}
 		case *expr.Payload:
-			if m.Base == expr.PayloadBaseNetworkHeader && m.Len == 4 {
-				name := map[uint32]string{12: "saddr", 16: "daddr"}[m.Offset]
+			if m.Base == expr.PayloadBaseNetworkHeader && (m.Len == 4 || m.Len == 16) {
+				name := map[uint32]string{12: "saddr", 16: "daddr", 8: "saddr", 24: "daddr"}[m.Offset]
 				if cmp.Op == expr.CmpOpNeq {
 					name = "!" + name
 				}
-				parts = append(parts, fmt.Sprintf("%s=%d.%d.%d.%d", name, cmp.Data[0], cmp.Data[1], cmp.Data[2], cmp.Data[3]))
+				parts = append(parts, name+"="+net.IP(cmp.Data).String())
 			}
 		}
 	}
@@ -1803,7 +1887,7 @@ func TestCompile_CommaZoneLists(t *testing.T) {
 		{
 			name: "fw in source list goes to output",
 			rule: config.Rule{Action: config.RuleAccept, Source: "fw,lan", Dest: "svr", Proto: "tcp", DPort: config.PortSpec{"22"}},
-			want: map[string][]string{"output": {""}, "forward": {"iif=eth1 oif=eth2"}},
+			want: map[string][]string{"output": {"oif=eth2"}, "forward": {"iif=eth1 oif=eth2"}},
 		},
 		{
 			name: "dest list with fw splits input and forward",
@@ -1846,9 +1930,54 @@ func TestCompile_CommaZoneLists(t *testing.T) {
 			want: map[string][]string{"forward": {"iif=eth1 oif=eth3", "iif=eth1 oif=eth0"}},
 		},
 		{
-			name: "interface-less ipsec zone keeps zone-agnostic rule, ip zone skipped",
+			name: "interface-less zones are skipped",
 			rule: config.Rule{Action: config.RuleAccept, Source: "lan", Dest: "vpn,dmz"},
-			want: map[string][]string{"forward": {"iif=eth1"}},
+			want: map[string][]string{},
+		},
+		{
+			name: "interface-less zone kept when address narrows it",
+			rule: config.Rule{Action: config.RuleAccept, Source: "lan", Dest: "vpn:192.0.2.1"},
+			want: map[string][]string{"forward": {"iif=eth1 daddr=192.0.2.1"}},
+		},
+		{
+			name: "fw source matches dest zone oif",
+			rule: config.Rule{Action: config.RuleAccept, Source: "fw", Dest: "lan,vpn,dmz", Proto: "tcp", DPort: config.PortSpec{"22"}},
+			want: map[string][]string{"output": {"oif=eth1"}},
+		},
+		{
+			name: "fw to all has no oif",
+			rule: config.Rule{Action: config.RuleAccept, Source: "fw", Dest: "all:192.0.2.1"},
+			want: map[string][]string{"output": {"daddr=192.0.2.1"}},
+		},
+		{
+			name: "dnat origdest",
+			rule: config.Rule{Action: config.RuleDNAT, Source: "net", Dest: "svr:192.0.2.17", Proto: "tcp", DPort: config.PortSpec{"80"}, OrigDest: "203.0.113.5"},
+			want: map[string][]string{"prerouting": {"iif=eth0 daddr=203.0.113.5"}},
+		},
+		{
+			name: "dnat origdest list",
+			rule: config.Rule{Action: config.RuleDNAT, Source: "net", Dest: "svr:192.0.2.17", Proto: "tcp", DPort: config.PortSpec{"80"}, OrigDest: "203.0.113.5,203.0.113.6"},
+			want: map[string][]string{"prerouting": {"iif=eth0 daddr=203.0.113.5", "iif=eth0 daddr=203.0.113.6"}},
+		},
+		{
+			name: "dnat negated origdest list",
+			rule: config.Rule{Action: config.RuleDNAT, Source: "net", Dest: "svr:192.0.2.17", Proto: "tcp", DPort: config.PortSpec{"80"}, OrigDest: "!203.0.113.5,203.0.113.6"},
+			want: map[string][]string{"prerouting": {"iif=eth0 !daddr=203.0.113.5 !daddr=203.0.113.6"}},
+		},
+		{
+			name: "accept origdest",
+			rule: config.Rule{Action: config.RuleAccept, Source: "net", Dest: "fw", Proto: "tcp", DPort: config.PortSpec{"22"}, OrigDest: "203.0.113.5"},
+			want: map[string][]string{"input": {"iif=eth0 daddr=203.0.113.5"}},
+		},
+		{
+			name: "origdest does not scope interface-less zone",
+			rule: config.Rule{Action: config.RuleAccept, Source: "vpn", Dest: "fw", Proto: "tcp", DPort: config.PortSpec{"22"}, OrigDest: "203.0.113.5"},
+			want: map[string][]string{},
+		},
+		{
+			name: "accept ipv6 origdest",
+			rule: config.Rule{Action: config.RuleAccept, Source: "net", Dest: "fw", Proto: "tcp", DPort: config.PortSpec{"22"}, OrigDest: "2001:db8::5"},
+			want: map[string][]string{"input": {"iif=eth0 daddr=2001:db8::5"}},
 		},
 		{
 			name:   "blrule zone list",
@@ -2255,3 +2384,96 @@ func TestCompile_ColonRanges(t *testing.T) {
 		})
 	}
 }
+
+func TestMatchOrigDest_FamilyGuard(t *testing.T) {
+	for addr, want := range map[string]byte{
+		"203.0.113.5":               unix.NFPROTO_IPV4,
+		"!203.0.113.0/24,192.0.2.1": unix.NFPROTO_IPV4,
+		"2001:db8::5":               unix.NFPROTO_IPV6,
+	} {
+		e, err := matchOrigDest(addr)
+		if err != nil {
+			t.Fatalf("%s: %v", addr, err)
+		}
+		if m, ok := e[0].(*expr.Meta); !ok || m.Key != expr.MetaKeyNFPROTO || e[1].(*expr.Cmp).Data[0] != want {
+			t.Errorf("%s: missing nfproto %d guard: %v", addr, want, e[:2])
+		}
+	}
+	if _, err := matchOrigDest("!203.0.113.5,2001:db8::5"); err == nil {
+		t.Error("mixed IPv4/IPv6 origdest: want error")
+	}
+}
+
+func TestCompile_OrigDestForwardRejected(t *testing.T) {
+	cfg := &config.Config{
+		Settings:   config.Settings{TableName: "test", AddressFamily: config.FamilyINET},
+		Zones:      map[string]config.Zone{"fw": {Type: config.ZoneFirewall}, "net": {Type: config.ZoneIP}, "svr": {Type: config.ZoneIP}},
+		Interfaces: []config.Interface{{Zone: "net", Interface: "eth0"}, {Zone: "svr", Interface: "eth2"}},
+		Rules:      []config.Rule{{Action: config.RuleAccept, Source: "net", Dest: "svr", Proto: "tcp", DPort: config.PortSpec{"80"}, OrigDest: "203.0.113.5"}},
+		PortGroups: make(map[string]config.PortGroup),
+	}
+	_, err := NewCompiler(cfg).Compile()
+	if err == nil || !strings.Contains(err.Error(), "not supported yet") {
+		t.Fatalf("Compile() error = %v, want forwarded ORIGDEST rejection", err)
+	}
+}
+
+func TestCompile_ConntrackHelper(t *testing.T) {
+	compile := func(rules ...config.ConntrackRule) (*FirewallState, error) {
+		cfg := &config.Config{
+			Settings:   config.Settings{TableName: "test", AddressFamily: config.FamilyINET},
+			Zones:      map[string]config.Zone{"fw": {Type: config.ZoneFirewall}},
+			Conntrack:  rules,
+			PortGroups: map[string]config.PortGroup{},
+		}
+		return NewCompiler(cfg).Compile()
+	}
+
+	state, err := compile(
+		config.ConntrackRule{Action: config.ConntrackHelper, Helper: "ftp", Proto: "tcp", DPort: config.PortSpec{"21"}},
+		config.ConntrackRule{Action: config.ConntrackHelper, Helper: "sip", Proto: "tcp", DPort: config.PortSpec{"5060"}, Chain: config.ConntrackPrerouting},
+		config.ConntrackRule{Action: config.ConntrackHelper, Helper: "tftp", Chain: config.ConntrackOutput},
+	)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	want := []Helper{
+		{"ftp", expr.CtHelper{Name: "ftp", L3Proto: unix.NFPROTO_INET, L4Proto: unix.IPPROTO_TCP}},
+		{"sip-tcp", expr.CtHelper{Name: "sip", L3Proto: unix.NFPROTO_INET, L4Proto: unix.IPPROTO_TCP}},
+		{"tftp", expr.CtHelper{Name: "tftp", L3Proto: unix.NFPROTO_INET, L4Proto: unix.IPPROTO_UDP}},
+	}
+	if !reflect.DeepEqual(state.Helpers, want) {
+		t.Errorf("helpers = %+v, want %+v", state.Helpers, want)
+	}
+
+	refs := func(chain string) []string {
+		var out []string
+		for _, r := range state.Rules[chain] {
+			ref, ok := r.Exprs[len(r.Exprs)-1].(*expr.Objref)
+			if !ok || ref.Type != unix.NFT_OBJECT_CT_HELPER {
+				t.Fatalf("%s: rule %s does not end in a ct helper objref", chain, r.Tag)
+			}
+			out = append(out, r.Tag+"="+ref.Name)
+		}
+		return out
+	}
+	if got := refs("helper_prerouting"); !reflect.DeepEqual(got, []string{
+		"conntrack:0:helper_prerouting=ftp", "conntrack:1:helper_prerouting=sip-tcp"}) {
+		t.Errorf("helper_prerouting = %v", got)
+	}
+	if got := refs("helper_output"); !reflect.DeepEqual(got, []string{
+		"conntrack:0:helper_output=ftp", "conntrack:2:helper_output=tftp"}) {
+		t.Errorf("helper_output = %v", got)
+	}
+
+	ftp := state.Rules["helper_prerouting"][0].Exprs
+	l4, _ := l4Matches("tcp", config.PortSpec{"21"}, nil)
+	if !reflect.DeepEqual(ftp[:len(ftp)-1], l4[0].exprs) {
+		t.Errorf("ftp rule does not match tcp dport 21: %#v", ftp)
+	}
+
+	if _, err := compile(config.ConntrackRule{Action: config.ConntrackHelper, Helper: "nope"}); err == nil {
+		t.Error("expected error for unknown helper without proto")
+	}
+}

internal/nftables/diff.go

@@ -20,15 +20,25 @@ type ManagedRule struct {
 
 type FirewallState struct {
 	Rules map[string][]ManagedRule
+	// Helpers are the ct helper objects in kernel (insertion) order.
+	Helpers []Helper
+}
+
+// Helper is a named ct helper object.
+type Helper struct {
+	Name   string        `json:"name"`
+	Helper expr.CtHelper `json:"helper"`
 }
 
 type ChangeSet struct {
-	Add    []ManagedRule
-	Remove []ManagedRule
+	Add           []ManagedRule
+	Remove        []ManagedRule
+	AddHelpers    []Helper
+	RemoveHelpers []string
 }
 
 func (cs *ChangeSet) Empty() bool {
-	return len(cs.Add) == 0 && len(cs.Remove) == 0
+	return len(cs.Add) == 0 && len(cs.Remove) == 0 && len(cs.AddHelpers) == 0 && len(cs.RemoveHelpers) == 0
 }
 
 func (cs *ChangeSet) Summary() string {
@@ -49,6 +59,12 @@ func (cs *ChangeSet) Summary() string {
 			fmt.Fprintf(&b, "    - [%s] %s (handle %d)\n", r.Chain, r.Tag, r.Handle)
 		}
 	}
+	for _, h := range cs.AddHelpers {
+		fmt.Fprintf(&b, "  + ct helper %q\n", h.Name)
+	}
+	for _, n := range cs.RemoveHelpers {
+		fmt.Fprintf(&b, "  - ct helper %q\n", n)
+	}
 	return b.String()
 }
 
@@ -56,7 +72,7 @@ func (cs *ChangeSet) Summary() string {
 // each chain, replace the middle, and insert the new rules before the first kept
 // suffix rule (or append when there is none).
 func computeDiff(current, desired *FirewallState) *ChangeSet {
-	cs := &ChangeSet{}
+	cs := diffHelpers(current, desired)
 
 	chains := make([]string, 0, len(current.Rules)+len(desired.Rules))
 	for c := range current.Rules {
@@ -109,7 +125,10 @@ func ruleEqual(a, b ManagedRule) bool {
 // restoreChangeSet replaces every managed rule in current with the snapshot's,
 // in snapshot order, so a restore cannot reorder rules.
 func restoreChangeSet(current, snap *FirewallState) *ChangeSet {
-	cs := &ChangeSet{}
+	cs := &ChangeSet{AddHelpers: snap.Helpers}
+	for _, h := range current.Helpers {
+		cs.RemoveHelpers = append(cs.RemoveHelpers, h.Name)
+	}
 	for _, rules := range current.Rules {
 		for _, r := range rules {
 			if r.Tag != "" {
@@ -131,3 +150,29 @@ func restoreChangeSet(current, snap *FirewallState) *ChangeSet {
 	}
 	return cs
 }
+
+// diffHelpers replaces any ct helper object that is missing or differs.
+// L3Proto is ignored: the kernel narrows inet to ip/ip6 for single-family helpers such as pptp.
+func diffHelpers(current, desired *FirewallState) *ChangeSet {
+	cs := &ChangeSet{}
+	same := func(a, b expr.CtHelper) bool { return a.Name == b.Name && a.L4Proto == b.L4Proto }
+	find := func(hs []Helper, name string) (expr.CtHelper, bool) {
+		for _, h := range hs {
+			if h.Name == name {
+				return h.Helper, true
+			}
+		}
+		return expr.CtHelper{}, false
+	}
+	for _, h := range current.Helpers {
+		if want, ok := find(desired.Helpers, h.Name); !ok || !same(want, h.Helper) {
+			cs.RemoveHelpers = append(cs.RemoveHelpers, h.Name)
+		}
+	}
+	for _, h := range desired.Helpers {
+		if have, ok := find(current.Helpers, h.Name); !ok || !same(have, h.Helper) {
+			cs.AddHelpers = append(cs.AddHelpers, h)
+		}
+	}
+	return cs
+}

internal/nftables/diff_test.go

@@ -5,6 +5,7 @@ import (
 	"testing"
 
 	"github.com/google/nftables/expr"
+	"golang.org/x/sys/unix"
 )
 
 func TestRestoreChangeSet(t *testing.T) {
@@ -64,3 +65,42 @@ func TestRestoreChangeSetEmptySnapshotRemovesAll(t *testing.T) {
 		t.Errorf("expected 1 remove 0 add, got %d/%d", len(cs.Remove), len(cs.Add))
 	}
 }
+
+func TestDiffHelpers(t *testing.T) {
+	h := func(name, typ string, l3 uint16, l4 uint8) Helper {
+		return Helper{Name: name, Helper: expr.CtHelper{Name: typ, L3Proto: l3, L4Proto: l4}}
+	}
+	ftp := h("ftp", "ftp", unix.NFPROTO_INET, unix.IPPROTO_TCP)
+	tftp := h("tftp", "tftp", unix.NFPROTO_INET, unix.IPPROTO_UDP)
+	sipUDP := h("sip", "sip", unix.NFPROTO_INET, unix.IPPROTO_UDP)
+	sipTCP := h("sip", "sip", unix.NFPROTO_INET, unix.IPPROTO_TCP)
+
+	current := &FirewallState{Helpers: []Helper{tftp, ftp, sipUDP}}
+	desired := &FirewallState{Helpers: []Helper{ftp, sipTCP}}
+
+	cs := computeDiff(current, desired)
+	if !reflect.DeepEqual(cs.RemoveHelpers, []string{"tftp", "sip"}) {
+		t.Errorf("remove = %v", cs.RemoveHelpers)
+	}
+	if !reflect.DeepEqual(cs.AddHelpers, []Helper{sipTCP}) {
+		t.Errorf("add = %v", cs.AddHelpers)
+	}
+
+	// Restore recreates every helper so kernel listing order matches the snapshot.
+	cs = restoreChangeSet(desired, current)
+	if !reflect.DeepEqual(cs.RemoveHelpers, []string{"ftp", "sip"}) || !reflect.DeepEqual(cs.AddHelpers, current.Helpers) {
+		t.Errorf("restore = -%v +%v", cs.RemoveHelpers, cs.AddHelpers)
+	}
+
+	live := &FirewallState{Helpers: []Helper{h("pptp", "pptp", unix.NFPROTO_IPV4, unix.IPPROTO_TCP)}}
+	want := &FirewallState{Helpers: []Helper{h("pptp", "pptp", unix.NFPROTO_INET, unix.IPPROTO_TCP)}}
+	if cs := computeDiff(live, want); !cs.Empty() {
+		t.Errorf("kernel-narrowed l3proto should not diff: %+v", cs)
+	}
+	if cs := computeDiff(desired, desired); !cs.Empty() {
+		t.Errorf("identical helpers should be empty: %+v", cs)
+	}
+	if cs := computeDiff(&FirewallState{}, desired); cs.Empty() {
+		t.Error("missing helpers should not be empty")
+	}
+}

internal/nftables/engine.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 
 	"github.com/google/nftables"
+	"github.com/google/nftables/expr"
 
 	"git.unkin.net/unkin/tomswall/internal/config"
 )
@@ -69,6 +70,20 @@ func (e *Engine) ensureChains(table *nftables.Table, policies map[string]nftable
 			Hooknum:  nftables.ChainHookPrerouting,
 			Priority: nftables.ChainPriorityNATDest,
 		},
+		"helper_prerouting": {
+			Name:     "helper_prerouting",
+			Table:    table,
+			Type:     nftables.ChainTypeFilter,
+			Hooknum:  nftables.ChainHookPrerouting,
+			Priority: nftables.ChainPriorityMangle,
+		},
+		"helper_output": {
+			Name:     "helper_output",
+			Table:    table,
+			Type:     nftables.ChainTypeFilter,
+			Hooknum:  nftables.ChainHookOutput,
+			Priority: nftables.ChainPriorityMangle,
+		},
 	}
 
 	for name, chain := range chains {
@@ -112,6 +127,13 @@ func (e *Engine) apply(changes *ChangeSet, policies map[string]nftables.ChainPol
 		})
 	}
 
+	for _, n := range changes.RemoveHelpers {
+		e.conn.DeleteObject(helperObj(table, n, expr.CtHelper{}))
+	}
+	for _, h := range changes.AddHelpers {
+		e.conn.AddObj(helperObj(table, h.Name, h.Helper))
+	}
+
 	for _, r := range changes.Add {
 		chain, ok := chains[r.Chain]
 		if !ok {
@@ -172,6 +194,18 @@ func (e *Engine) readCurrentState() (*FirewallState, error) {
 		return state, err
 	}
 
+	objs, err := e.conn.GetNamedObjects(ourTable)
+	if err != nil {
+		return nil, fmt.Errorf("listing objects: %w", err)
+	}
+	for _, o := range objs {
+		if no, ok := o.(*nftables.NamedObj); ok && no.Type == nftables.ObjTypeCtHelper {
+			if h, ok := no.Obj.(*expr.CtHelper); ok {
+				state.Helpers = append(state.Helpers, Helper{Name: no.Name, Helper: *h})
+			}
+		}
+	}
+
 	chains, err := e.conn.ListChainsOfTableFamily(nftables.TableFamilyINet)
 	if err != nil {
 		return nil, fmt.Errorf("listing chains: %w", err)
@@ -205,6 +239,7 @@ type Snapshot struct {
 	Present  bool                            `json:"present"`
 	Policies map[string]nftables.ChainPolicy `json:"policies,omitempty"`
 	Rules    map[string][]SnapshotRule       `json:"rules,omitempty"`
+	Helpers  []Helper                        `json:"helpers,omitempty"`
 }
 
 // SnapshotRule is a managed rule with its expressions in netlink wire format.
@@ -241,6 +276,7 @@ func (e *Engine) Snapshot() (*Snapshot, error) {
 	if err != nil {
 		return nil, err
 	}
+	snap.Helpers = state.Helpers
 	return snap, nil
 }
 
@@ -257,6 +293,7 @@ func (e *Engine) Restore(s *Snapshot) error {
 	if err != nil {
 		return err
 	}
+	want.Helpers = s.Helpers
 	current, err := e.readCurrentState()
 	if err != nil {
 		return err
@@ -264,6 +301,10 @@ func (e *Engine) Restore(s *Snapshot) error {
 	return e.apply(restoreChangeSet(current, want), s.Policies)
 }
 
+func helperObj(table *nftables.Table, name string, h expr.CtHelper) *nftables.NamedObj {
+	return &nftables.NamedObj{Table: table, Name: name, Type: nftables.ObjTypeCtHelper, Obj: &h}
+}
+
 func policyPtr(p nftables.ChainPolicy) *nftables.ChainPolicy {
 	return &p
 }