Merge pull request 'Match zones defined by hosts entries' (#38) from benvin/hosts-zones into main

Reviewed-on: #38

internal/config/config_test.go

@@ -531,6 +531,13 @@ func TestValidateHosts(t *testing.T) {
 			},
 			wantErr: "interface required",
 		},
+		{
+			name:       "invalid exclusion",
+			zones:      map[string]Zone{"fw": {Type: ZoneFirewall}, "net": {Type: ZoneIP}, "loc": {Type: ZoneIP}},
+			interfaces: []Interface{{Zone: "net", Interface: "eth0"}},
+			hosts:      []Host{{Zone: "loc", Interface: "eth0", Addresses: []string{"192.0.2.0/24"}, Exclusions: []string{"192.0.2.0/24!192.0.2.7"}}},
+			wantErr:    "invalid address",
+		},
 	}
 
 	for _, tt := range tests {

internal/config/hosts.go

@@ -1,6 +1,10 @@
 package config
 
-import "fmt"
+import (
+	"fmt"
+	"net/netip"
+	"slices"
+)
 
 type Host struct {
 	Zone       string      `yaml:"zone"`
@@ -52,6 +56,13 @@ func (c *Config) validateHosts() error {
 		if !h.Dynamic && len(h.Addresses) == 0 {
 			return fmt.Errorf("host[%d]: at least one address required (or set dynamic: true)", i)
 		}
+		for _, a := range slices.Concat(h.Addresses, h.Exclusions) {
+			if _, err := netip.ParsePrefix(a); err != nil {
+				if _, err := netip.ParseAddr(a); err != nil {
+					return fmt.Errorf("host[%d]: invalid address %q", i, a)
+				}
+			}
+		}
 	}
 	return nil
 }

internal/nftables/compiler.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"log/slog"
 	"net"
+	"net/netip"
 	"slices"
 	"sort"
 	"strconv"
@@ -345,12 +346,12 @@ func (c *Compiler) compileConntrackPair(state *FirewallState, tag, chain string,
 		(dstAddr == "" || strings.HasPrefix(dstAddr, "!")) {
 		return fmt.Errorf("conntrack DEST zone %q needs an address in prerouting", dstZone)
 	}
-	srcIfaces, dstIfaces := c.resolveZoneInterfaces(srcZone, srcAddr), []string{""}
+	srcIfaces, dstIfaces := c.resolveZone(srcZone, srcAddr), []zoneMatch{{}}
-	if chain == "raw_prerouting" && c.resolveZoneInterfaces(dstZone, dstAddr) == nil {
+	if chain == "raw_prerouting" && c.resolveZone(dstZone, dstAddr) == nil {
 		return nil
 	}
 	if chain == "raw_output" {
-		srcIfaces, dstIfaces = []string{""}, c.resolveZoneInterfaces(dstZone, dstAddr)
+		srcIfaces, dstIfaces = []zoneMatch{{}}, c.resolveZone(dstZone, dstAddr)
 	}
 	out := chain
 	if ct.Action == config.ConntrackHelper {
@@ -674,8 +675,8 @@ func splitAddrs(addr string) []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, srcAddr)
+	srcIfaces := c.resolveZone(srcZone, srcAddr)
-	dstIfaces := c.resolveZoneInterfaces(dstZone, dstAddr)
+	dstIfaces := c.resolveZone(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" {
@@ -744,7 +745,7 @@ func (c *Compiler) compileDNATRule(state *FirewallState, tag, srcZone, srcAddr,
 		dnatPort = uint16(p)
 	}
 
-	srcIfaces := c.resolveZoneInterfaces(srcZone, srcAddr)
+	srcIfaces := c.resolveZone(srcZone, srcAddr)
 
 	var odExprs []expr.Any
 	if origDest != "" {
@@ -765,12 +766,12 @@ func (c *Compiler) compileDNATRule(state *FirewallState, tag, srcZone, srcAddr,
 	}
 
 	for _, srcIface := range srcIfaces {
+		zm, err := zoneMatchExprs(srcIface, true)
+		if err != nil {
+			return err
+		}
 		for _, m := range matches {
-			var exprs []expr.Any
+			exprs := slices.Clone(zm)
-
-			if srcIface != "" {
-				exprs = append(exprs, matchIfaceName(true, srcIface)...)
-			}
 
 			if srcAddr != "" {
 				src, err := matchSourceCIDR(srcAddr)
@@ -857,31 +858,35 @@ func (c *Compiler) compileDNATRule(state *FirewallState, tag, srcZone, srcAddr,
 func (c *Compiler) compilePolicies(state *FirewallState) error {
 	fwZone := c.cfg.FirewallZone()
 
+	overridden := map[string]bool{}
 	for i, pol := range c.cfg.Policy {
 		tag := fmt.Sprintf("policy:%d", i)
+		explicitIntra := pol.Source == pol.Dest && !isGlobalZone(pol.Source)
 
 		srcZones := c.expandZoneRef(pol.Source)
 		dstZones := c.expandZoneRef(pol.Dest)
 
 		for _, sz := range srcZones {
 			for _, dz := range dstZones {
-				if sz == dz && !strings.HasSuffix(pol.Source, "+") {
+				if sz == dz {
-					continue
+					if sz == fwZone || (!explicitIntra && !strings.HasSuffix(pol.Source, "+") && !strings.HasSuffix(pol.Dest, "+")) {
+						continue
+					}
+					overridden[sz] = true
 				}
 
 				chain := c.selectChain(sz, dz, fwZone)
-				srcIfaces := c.resolveZoneInterfaces(sz, "")
+				srcIfaces := c.resolveZone(sz, "")
-				dstIfaces := c.resolveZoneInterfaces(dz, "")
+				dstIfaces := c.resolveZone(dz, "")
 
 				for _, si := range srcIfaces {
 					for _, di := range dstIfaces {
-						var exprs []expr.Any
+						if sz == dz && intraZoneSkip(si, di) {
-
+							continue
-						if si != "" {
-							exprs = append(exprs, matchIfaceName(true, si)...)
 						}
-						if di != "" && chain != "input" {
+						exprs, err := zonePairExprs(si, di, chain)
-							exprs = append(exprs, matchIfaceName(false, di)...)
+						if err != nil {
+							return fmt.Errorf("policy[%d]: %w", i, err)
 						}
 
 						if pol.RateLimit != "" {
@@ -909,9 +914,66 @@ func (c *Compiler) compilePolicies(state *FirewallState) error {
 		}
 	}
 
+	return c.compileImplicitIntraZone(state, overridden)
+}
+
+// compileImplicitIntraZone accepts traffic between different interfaces of one zone, shorewall's implicit intra-zone ACCEPT policy.
+func (c *Compiler) compileImplicitIntraZone(state *FirewallState, overridden map[string]bool) error {
+	fwZone := c.cfg.FirewallZone()
+	zones := make([]string, 0, len(c.cfg.Zones))
+	for z := range c.cfg.Zones {
+		zones = append(zones, z)
+	}
+	sort.Strings(zones)
+	for _, z := range zones {
+		if z == fwZone || overridden[z] {
+			continue
+		}
+		if len(c.cfg.ZoneInterfaces(z)) == 0 && !slices.ContainsFunc(c.cfg.Hosts, func(h config.Host) bool { return h.Zone == z }) {
+			continue
+		}
+		matches := c.resolveZone(z, "")
+		for _, si := range matches {
+			for _, di := range matches {
+				if intraZoneSkip(si, di) {
+					continue
+				}
+				exprs, err := zonePairExprs(si, di, "forward")
+				if err != nil {
+					return fmt.Errorf("zone %s: %w", z, err)
+				}
+				state.Rules["forward"] = append(state.Rules["forward"], ManagedRule{
+					Chain: "forward",
+					Exprs: append(exprs, &expr.Verdict{Kind: expr.VerdictAccept}),
+					Tag:   "intra:" + z,
+				})
+			}
+		}
+	}
 	return nil
 }
 
+// intraZoneSkip drops intra-zone pairs on one interface unless both are routeback hosts entries
+// (interface routeback is compileIntraZone's job), and pairs whose address families can never both match.
+func intraZoneSkip(si, di zoneMatch) bool {
+	if si.iface != "" && si.iface == di.iface && !(si.routeback && di.routeback) {
+		return true
+	}
+	a, b := matchFamily(si), matchFamily(di)
+	return a != 0 && b != 0 && a != b
+}
+
+// matchFamily is the NFPROTO a zoneMatch is guarded by: its host address's family, else fam.
+func matchFamily(m zoneMatch) byte {
+	if p, err := parsePrefix(m.addr); err == nil {
+		if p.Addr().Is4() {
+			return unix.NFPROTO_IPV4
+		}
+		return unix.NFPROTO_IPV6
+	}
+	return m.fam
+}
+
 func (c *Compiler) compileSNAT(state *FirewallState) error {
 	for i, snat := range c.cfg.SNAT {
 		tag := fmt.Sprintf("snat:%d", i)
@@ -1213,11 +1275,23 @@ func (c *Compiler) selectChain(srcZone, dstZone, fwZone string) string {
 	return "forward"
 }
 
-// resolveZoneInterfaces returns nil (fail closed) for an unknown zone, or one with no interfaces unless a non-negated address match narrows the rule.
+// zoneMatch classifies a packet into a zone: an interface (empty: any) and, for a hosts entry, one host
-func (c *Compiler) resolveZoneInterfaces(zone, addr string) []string {
+// address; excl carves out hosts exclusions and the hosts of sub-zones, which shorewall matches first.
+// fam (an NFPROTO; addr's family when set, else 0: any) guards addr and excl so IPv4 offsets are
+// never compared against IPv6 bytes. routeback marks a hosts entry with the routeback option.
+type zoneMatch struct {
+	iface, addr string
+	excl        []string
+	fam         byte
+	routeback   bool
+}
+
+// resolveZone returns nil (fail closed) for an unknown zone, or one with neither interfaces nor hosts
+// unless a non-negated address match narrows the rule.
+func (c *Compiler) resolveZone(zone, addr string) []zoneMatch {
 	switch zone {
 	case "", "all", "all+", "any", "any+":
-		return []string{""}
+		return []zoneMatch{{}}
 	}
 	z, ok := c.cfg.Zones[zone]
 	if !ok {
@@ -1225,24 +1299,151 @@ func (c *Compiler) resolveZoneInterfaces(zone, addr string) []string {
 		return nil
 	}
 	if z.Type == config.ZoneFirewall {
-		return []string{""}
+		return []zoneMatch{{}}
 	}
-	if ifaces := c.cfg.ZoneInterfaces(zone); len(ifaces) > 0 {
+	var out []zoneMatch
-		return ifaces
+	hasHosts := false
+	for _, iface := range c.cfg.ZoneInterfaces(zone) {
+		sub, back := c.subZoneHosts(zone, iface)
+		if len(sub) == 0 {
+			out = append(out, zoneMatch{iface: iface})
+		} else {
+			v4, v6 := splitFamily(sub)
+			out = append(out, zoneMatch{iface: iface, excl: v4, fam: unix.NFPROTO_IPV4},
+				zoneMatch{iface: iface, excl: v6, fam: unix.NFPROTO_IPV6})
+		}
+		for _, b := range back {
+			if addrsOverlap(b, addr) {
+				out = append(out, zoneMatch{iface: iface, addr: b})
+			}
+		}
+	}
+	for _, h := range c.cfg.Hosts {
+		if h.Zone != zone {
+			continue
+		}
+		hasHosts = true
+		sub, _ := c.subZoneHosts(zone, h.Interface)
+		v4, v6 := splitFamily(slices.Concat(h.Exclusions, sub))
+		for _, a := range h.Addresses {
+			if addrsOverlap(a, addr) {
+				m := zoneMatch{iface: h.Interface, addr: a, excl: v6, routeback: h.Options.RouteBack}
+				if p, err := parsePrefix(a); err == nil && p.Addr().Is4() {
+					m.excl = v4
+				}
+				out = append(out, m)
+			}
+		}
+	}
+	if len(out) > 0 || hasHosts {
+		return out
 	}
 	if addr != "" && !strings.HasPrefix(addr, "!") {
-		return []string{""}
+		return []zoneMatch{{}}
 	}
 	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)
+		slog.Warn("compiler: zone has no interfaces or hosts, skipping its rules", "zone", zone)
 	}
 	return nil
 }
 
+// subZoneHosts lists the host addresses on iface that belong to sub-zones of zone, and those
+// sub-zone hosts' exclusions, which fall back to zone.
+func (c *Compiler) subZoneHosts(zone, iface string) (sub, back []string) {
+	for _, h := range c.cfg.Hosts {
+		if h.Interface == iface && c.cfg.IsSubZone(h.Zone, zone) {
+			sub = append(sub, h.Addresses...)
+			back = append(back, h.Exclusions...)
+		}
+	}
+	return sub, back
+}
+
+// addrsOverlap reports whether a host address can match a rule address; unparsable or negated rule addresses keep the host.
+func addrsOverlap(host, rule string) bool {
+	if rule == "" || strings.HasPrefix(rule, "!") {
+		return true
+	}
+	h, err := parsePrefix(host)
+	if err != nil {
+		return true
+	}
+	for _, r := range strings.Split(rule, ",") {
+		if p, err := parsePrefix(r); err != nil || p.Overlaps(h) {
+			return true
+		}
+	}
+	return false
+}
+
+// splitFamily partitions addresses by family; unparsable ones go to v6 so zoneMatchExprs still rejects them.
+func splitFamily(addrs []string) (v4, v6 []string) {
+	for _, a := range addrs {
+		if p, err := parsePrefix(a); err == nil && p.Addr().Is4() {
+			v4 = append(v4, a)
+		} else {
+			v6 = append(v6, a)
+		}
+	}
+	return v4, v6
+}
+
+func parsePrefix(s string) (netip.Prefix, error) {
+	if a, err := netip.ParseAddr(s); err == nil {
+		return netip.PrefixFrom(a, a.BitLen()), nil
+	}
+	return netip.ParsePrefix(s)
+}
+
+// zoneMatchExprs matches a zone on the in (src) or out interface plus its host address and exclusions,
+// all guarded by m.fam so an IPv4 address never matches IPv6 bytes in an inet table.
+func zoneMatchExprs(m zoneMatch, src bool) ([]expr.Any, error) {
+	var out []expr.Any
+	if m.iface != "" {
+		out = matchIfaceName(src, m.iface)
+	}
+	var addr []expr.Any
+	if m.addr != "" {
+		p, err := parsePrefix(m.addr)
+		if err != nil {
+			return nil, fmt.Errorf("invalid host address %q", m.addr)
+		}
+		if addr, err = matchAddrCIDR(m.addr, src); err != nil {
+			return nil, err
+		}
+		m.fam = unix.NFPROTO_IPV6
+		if p.Addr().Is4() {
+			m.fam = unix.NFPROTO_IPV4
+		}
+	}
+	if m.fam != 0 {
+		out = append(out, matchNFProto(m.fam)...)
+	}
+	out = append(out, addr...)
+	if len(m.excl) > 0 {
+		e, err := matchAddrCIDR("!"+strings.Join(m.excl, ","), src)
+		if err != nil {
+			return nil, err
+		}
+		out = append(out, e...)
+	}
+	return out, nil
+}
+
+// zonePairExprs matches the source zone inbound and, outside input, the dest zone outbound.
+func zonePairExprs(src, dst zoneMatch, chain string) ([]expr.Any, error) {
+	out, err := zoneMatchExprs(src, true)
+	if err != nil || chain == "input" {
+		return out, err
+	}
+	d, err := zoneMatchExprs(dst, false)
+	return append(out, d...), err
+}
+
 func (c *Compiler) expandZoneRef(ref string) []string {
 	base := ref
 	var excluded map[string]bool
@@ -1272,14 +1473,10 @@ func (c *Compiler) expandZoneRef(ref string) []string {
 	return []string{base}
 }
 
-func (c *Compiler) buildMatchExprs(srcIface, dstIface, chain, proto string, dports, sports config.PortSpec, srcAddr, dstAddr string) ([]l4Match, error) {
+func (c *Compiler) buildMatchExprs(srcIface, dstIface zoneMatch, chain, proto string, dports, sports config.PortSpec, srcAddr, dstAddr string) ([]l4Match, error) {
-	var exprs []expr.Any
+	exprs, err := zonePairExprs(srcIface, dstIface, chain)
-
+	if err != nil {
-	if srcIface != "" {
+		return nil, err
-		exprs = append(exprs, matchIfaceName(true, srcIface)...)
-	}
-	if dstIface != "" && chain != "input" {
-		exprs = append(exprs, matchIfaceName(false, dstIface)...)
 	}
 
 	if srcAddr != "" {

internal/nftables/compiler_test.go

@@ -7,6 +7,7 @@ import (
 	"log/slog"
 	"net"
 	"reflect"
+	"slices"
 	"strings"
 	"testing"
 
@@ -144,19 +145,17 @@ func TestCompiler_ResolveZoneInterfaces(t *testing.T) {
 	}
 	c := NewCompiler(cfg)
 
-	ifaces := c.resolveZoneInterfaces("net", "")
+	for _, tt := range []struct {
-	if len(ifaces) != 1 || ifaces[0] != "eth0" {
+		zone string
-		t.Errorf("resolveZoneInterfaces(net) = %v, want [eth0]", ifaces)
+		want []zoneMatch
-	}
+	}{
-
+		{"net", []zoneMatch{{iface: "eth0"}}},
-	ifaces = c.resolveZoneInterfaces("all", "")
+		{"all", []zoneMatch{{}}},
-	if len(ifaces) != 1 || ifaces[0] != "" {
+		{"fw", []zoneMatch{{}}},
-		t.Errorf("resolveZoneInterfaces(all) = %v, want [\"\"]", ifaces)
+	} {
-	}
+		if got := c.resolveZone(tt.zone, ""); !reflect.DeepEqual(got, tt.want) {
-
+			t.Errorf("resolveZone(%s) = %v, want %v", tt.zone, got, tt.want)
-	ifaces = c.resolveZoneInterfaces("fw", "")
+		}
-	if len(ifaces) != 1 || ifaces[0] != "" {
-		t.Errorf("resolveZoneInterfaces(fw) = %v, want [\"\"]", ifaces)
 	}
 }
 
@@ -1849,13 +1848,13 @@ func TestCompile_InterfacelessZonesFailClosed(t *testing.T) {
 			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"}},
+		}, "policy:0", 1, nil},
 		{"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"}},
+		}, "policy:0", 2, []string{"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"}},
 	}
@@ -1895,6 +1894,19 @@ func TestCompile_InterfacelessZonesFailClosed(t *testing.T) {
 func describeRule(r ManagedRule) string {
 	var parts []string
 	for i, e := range r.Exprs {
+		if p, ok := e.(*expr.Payload); ok && p.Base == expr.PayloadBaseNetworkHeader && i+2 < len(r.Exprs) {
+			bw, okb := r.Exprs[i+1].(*expr.Bitwise)
+			cmp, okc := r.Exprs[i+2].(*expr.Cmp)
+			if okb && okc {
+				name := map[uint32]string{12: "saddr", 16: "daddr", 8: "saddr", 24: "daddr"}[p.Offset]
+				if cmp.Op == expr.CmpOpNeq {
+					name = "!" + name
+				}
+				ones, _ := net.IPMask(bw.Mask).Size()
+				parts = append(parts, fmt.Sprintf("%s=%s/%d", name, net.IP(cmp.Data), ones))
+				continue
+			}
+		}
 		cmp, ok := func() (*expr.Cmp, bool) {
 			if i+1 >= len(r.Exprs) {
 				return nil, false
@@ -1912,6 +1924,8 @@ func describeRule(r ManagedRule) string {
 				parts = append(parts, "iif="+strings.TrimRight(string(cmp.Data), "\x00"))
 			case expr.MetaKeyOIFNAME:
 				parts = append(parts, "oif="+strings.TrimRight(string(cmp.Data), "\x00"))
+			case expr.MetaKeyNFPROTO:
+				parts = append(parts, map[byte]string{unix.NFPROTO_IPV4: "ip4", unix.NFPROTO_IPV6: "ip6"}[cmp.Data[0]])
 			}
 		case *expr.Payload:
 			if m.Base == expr.PayloadBaseNetworkHeader && (m.Len == 4 || m.Len == 16) {
@@ -2050,25 +2064,25 @@ func TestCompile_CommaZoneLists(t *testing.T) {
 		{
 			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"},
+			want: map[string][]string{"prerouting": {"iif=eth0 ip4 daddr=203.0.113.5"},
 				"forward": {"iif=eth0 oif=eth2 daddr=192.0.2.17"}},
 		},
 		{
 			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"},
+			want: map[string][]string{"prerouting": {"iif=eth0 ip4 daddr=203.0.113.5", "iif=eth0 ip4 daddr=203.0.113.6"},
 				"forward": {"iif=eth0 oif=eth2 daddr=192.0.2.17"}},
 		},
 		{
 			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"},
+			want: map[string][]string{"prerouting": {"iif=eth0 ip4 !daddr=203.0.113.5 !daddr=203.0.113.6"},
 				"forward": {"iif=eth0 oif=eth2 daddr=192.0.2.17"}},
 		},
 		{
 			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"}},
+			want: map[string][]string{"input": {"iif=eth0 ip4 daddr=203.0.113.5"}},
 		},
 		{
 			name: "origdest does not scope interface-less zone",
@@ -2078,7 +2092,7 @@ func TestCompile_CommaZoneLists(t *testing.T) {
 		{
 			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"}},
+			want: map[string][]string{"input": {"iif=eth0 ip6 daddr=2001:db8::5"}},
 		},
 		{
 			name:   "blrule zone list",
@@ -3320,3 +3334,332 @@ func TestCompile_LogLimitSplitsAroundExtrasAndNAT(t *testing.T) {
 		}
 	}
 }
+
+// hostsCfg models a shorewall setup where lan:net is defined by hosts on net's interfaces.
+func hostsCfg(mod func(*config.Config)) *config.Config {
+	cfg := &config.Config{
+		Settings: config.Settings{TableName: "test", AddressFamily: config.FamilyINET},
+		Zones: map[string]config.Zone{
+			"fw": {Type: config.ZoneFirewall}, "net": {Type: config.ZoneIP},
+			"lan": {Type: config.ZoneIP, Parents: []string{"net"}}, "vpn": {Type: config.ZoneIP},
+		},
+		Interfaces: []config.Interface{
+			{Zone: "net", Interface: "wlo1"}, {Zone: "net", Interface: "enp2s0"}, {Zone: "vpn", Interface: "tun0"},
+		},
+		Hosts: []config.Host{
+			{Zone: "lan", Interface: "wlo1", Addresses: []string{"192.0.2.0/24"}},
+			{Zone: "lan", Interface: "enp2s0", Addresses: []string{"198.51.100.0/24"}},
+		},
+		Policy: []config.Policy{
+			{Source: "net", Dest: "all", Action: config.PolicyDrop},
+			{Source: "lan", Dest: "fw", Action: config.PolicyReject},
+			{Source: "all", Dest: "all", Action: config.PolicyReject},
+		},
+		Rules: []config.Rule{
+			{Action: config.RuleAccept, Source: "lan,vpn", Dest: "fw", Proto: "tcp", DPort: config.PortSpec{"6768"}},
+		},
+		PortGroups: make(map[string]config.PortGroup),
+	}
+	if mod != nil {
+		mod(cfg)
+	}
+	return cfg
+}
+
+func describeTagged(state *FirewallState, chain, tag string) []string {
+	var out []string
+	for _, r := range taggedRules(state, chain, tag) {
+		out = append(out, describeRule(r))
+	}
+	return out
+}
+
+func TestCompile_HostsZoneRules(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, hostsCfg(nil))
+	want := []string{"iif=wlo1 ip4 saddr=192.0.2.0/24", "iif=enp2s0 ip4 saddr=198.51.100.0/24", "iif=tun0"}
+	if got := describeTagged(state, "input", "rule:0"); !reflect.DeepEqual(got, want) {
+		t.Errorf("input rule:0 = %q, want %q", got, want)
+	}
+	if strings.Contains(logs.String(), "skipping") {
+		t.Errorf("unexpected warning:\n%s", logs.String())
+	}
+}
+
+func TestCompile_HostsSubZoneBeforeParent(t *testing.T) {
+	state := mustCompile(t, hostsCfg(nil))
+	want := []string{
+		"iif=wlo1 ip4 !saddr=192.0.2.0/24", "iif=wlo1 ip6",
+		"iif=enp2s0 ip4 !saddr=198.51.100.0/24", "iif=enp2s0 ip6",
+	}
+	if got := describeTagged(state, "input", "policy:0"); !reflect.DeepEqual(got, want) {
+		t.Errorf("net->fw policy = %q, want %q", got, want)
+	}
+	want = []string{"iif=wlo1 ip4 saddr=192.0.2.0/24", "iif=enp2s0 ip4 saddr=198.51.100.0/24"}
+	if got := describeTagged(state, "input", "policy:1"); !reflect.DeepEqual(got, want) {
+		t.Errorf("lan->fw policy = %q, want %q", got, want)
+	}
+	for _, r := range taggedRules(state, "input", "policy:1") {
+		if !slices.ContainsFunc(r.Exprs, func(e expr.Any) bool {
+			m, ok := e.(*expr.Meta)
+			return ok && m.Key == expr.MetaKeyNFPROTO
+		}) {
+			t.Errorf("host match lacks an nfproto guard: %v", describeRule(r))
+		}
+	}
+}
+
+func TestCompile_HostsZoneMatches(t *testing.T) {
+	tests := []struct {
+		name  string
+		mod   func(*config.Config)
+		chain string
+		tag   string
+		want  []string
+	}{
+		{"forward to hosts zone", func(c *config.Config) {
+			c.Rules = []config.Rule{{Action: config.RuleAccept, Source: "vpn", Dest: "lan", Proto: "tcp"}}
+		}, "forward", "rule:0", []string{"iif=tun0 oif=wlo1 ip4 daddr=192.0.2.0/24", "iif=tun0 oif=enp2s0 ip4 daddr=198.51.100.0/24"}},
+		{"rule address prunes non-overlapping hosts", func(c *config.Config) {
+			c.Rules = []config.Rule{{Action: config.RuleAccept, Source: "lan:192.0.2.5", Dest: "fw", Proto: "tcp"}}
+		}, "input", "rule:0", []string{"iif=wlo1 ip4 saddr=192.0.2.0/24 saddr=192.0.2.5"}},
+		{"host exclusions and sub-zone exclusions fall back to the parent", func(c *config.Config) {
+			c.Hosts[1].Exclusions = []string{"198.51.100.7"}
+			c.Rules = []config.Rule{{Action: config.RuleAccept, Source: "net", Dest: "fw", Proto: "tcp"}}
+		}, "input", "rule:0", []string{
+			"iif=wlo1 ip4 !saddr=192.0.2.0/24", "iif=wlo1 ip6",
+			"iif=enp2s0 ip4 !saddr=198.51.100.0/24", "iif=enp2s0 ip6",
+			"iif=enp2s0 ip4 saddr=198.51.100.7",
+		}},
+		{"host exclusion", func(c *config.Config) {
+			c.Hosts[1].Exclusions = []string{"198.51.100.7"}
+		}, "input", "policy:1", []string{"iif=wlo1 ip4 saddr=192.0.2.0/24", "iif=enp2s0 ip4 saddr=198.51.100.0/24 !saddr=198.51.100.7"}},
+		{"DNAT from hosts zone", func(c *config.Config) {
+			c.Rules = []config.Rule{{Action: config.RuleDNAT, Source: "lan", Dest: "vpn:203.0.113.10", Proto: "tcp", DPort: config.PortSpec{"80"}}}
+		}, "prerouting", "rule:0", []string{"iif=wlo1 ip4 saddr=192.0.2.0/24", "iif=enp2s0 ip4 saddr=198.51.100.0/24"}},
+		{"conntrack from hosts zone", func(c *config.Config) {
+			c.Conntrack = []config.ConntrackRule{{Action: config.ConntrackNoTrack, Source: "lan", Proto: "udp"}}
+		}, "raw_prerouting", "conntrack:0:raw_prerouting", []string{"iif=wlo1 ip4 saddr=192.0.2.0/24", "iif=enp2s0 ip4 saddr=198.51.100.0/24"}},
+		{"blrule from hosts zone", func(c *config.Config) {
+			c.Blrules = []config.BlruleRule{{Action: config.BlruleDrop, Source: "lan", Dest: "all"}}
+		}, "input", "blrule:0", []string{"iif=wlo1 ip4 saddr=192.0.2.0/24", "iif=enp2s0 ip4 saddr=198.51.100.0/24"}},
+		{"all expansion includes hosts zone", func(c *config.Config) {
+			c.Rules = []config.Rule{{Action: config.RuleAccept, Source: "all!net,vpn", Dest: "fw", Proto: "tcp"}}
+		}, "input", "rule:0", []string{"iif=wlo1 ip4 saddr=192.0.2.0/24", "iif=enp2s0 ip4 saddr=198.51.100.0/24"}},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			state := mustCompile(t, hostsCfg(tt.mod))
+			if got := describeTagged(state, tt.chain, tt.tag); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("%s %s = %q, want %q", tt.chain, tt.tag, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestCompile_IntraZoneMultiInterface(t *testing.T) {
+	tests := []struct {
+		name   string
+		policy []config.Policy
+		tag    string
+		want   []string
+	}{
+		{
+			name:   "implicit accept between distinct interfaces",
+			policy: []config.Policy{{Source: "all", Dest: "all", Action: config.PolicyDrop}},
+			tag:    "intra:lxd",
+			want:   []string{"iif=lxdbr0 oif=docker0", "iif=lxdbr0 oif=br-", "iif=docker0 oif=lxdbr0", "iif=docker0 oif=br-", "iif=br- oif=lxdbr0", "iif=br- oif=docker0"},
+		},
+		{
+			name:   "explicit zone policy overrides",
+			policy: []config.Policy{{Source: "lxd", Dest: "lxd", Action: config.PolicyDrop, Log: "info"}, {Source: "all", Dest: "all", Action: config.PolicyDrop}},
+			tag:    "policy:0",
+			want:   []string{"iif=lxdbr0 oif=docker0", "iif=lxdbr0 oif=br-", "iif=docker0 oif=lxdbr0", "iif=docker0 oif=br-", "iif=br- oif=lxdbr0", "iif=br- oif=docker0"},
+		},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(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},
+					"lxd": {Type: config.ZoneIP},
+				},
+				Interfaces: []config.Interface{
+					{Zone: "net", Interface: "eth0"},
+					{Zone: "lxd", Interface: "lxdbr0"},
+					{Zone: "lxd", Interface: "docker0"},
+					{Zone: "lxd", Interface: "br-+"},
+				},
+				Policy:     tc.policy,
+				PortGroups: map[string]config.PortGroup{},
+			}
+			state, err := NewCompiler(cfg).Compile()
+			if err != nil {
+				t.Fatalf("Compile() error: %v", err)
+			}
+			var got, all []string
+			for _, r := range state.Rules["forward"] {
+				if r.Tag == tc.tag {
+					got = append(got, describeRule(r))
+				}
+				if strings.HasPrefix(r.Tag, "intra:") {
+					all = append(all, r.Tag)
+				}
+			}
+			if !reflect.DeepEqual(got, tc.want) {
+				t.Errorf("%s rules = %q, want %q", tc.tag, got, tc.want)
+			}
+			if tc.tag != "intra:lxd" && len(all) != 0 {
+				t.Errorf("explicit policy must replace implicit accept, got %q", all)
+			}
+			last := taggedRules(state, "forward", tc.tag)
+			if len(last) == 0 {
+				return
+			}
+			if v, ok := last[0].Exprs[len(last[0].Exprs)-1].(*expr.Verdict); !ok || (tc.tag == "intra:lxd") != (v.Kind == expr.VerdictAccept) {
+				t.Errorf("%s verdict = %#v", tc.tag, last[0].Exprs[len(last[0].Exprs)-1])
+			}
+		})
+	}
+}
+
+func TestCompile_HostsAddressMatchesFamilyGuarded(t *testing.T) {
+	state := mustCompile(t, hostsCfg(func(c *config.Config) {
+		c.Hosts[0].Addresses = append(c.Hosts[0].Addresses, "2001:db8::/64")
+		c.Hosts[0].Exclusions = []string{"192.0.2.9"}
+	}))
+	want := []string{
+		"iif=wlo1 ip4 !saddr=192.0.2.0/24", "iif=wlo1 ip6 !saddr=2001:db8::/64",
+		"iif=wlo1 ip4 saddr=192.0.2.9",
+		"iif=enp2s0 ip4 !saddr=198.51.100.0/24", "iif=enp2s0 ip6",
+	}
+	if got := describeTagged(state, "input", "policy:0"); !reflect.DeepEqual(got, want) {
+		t.Errorf("net->fw DROP policy = %q, want %q", got, want)
+	}
+	want = []string{
+		"iif=wlo1 ip4 saddr=192.0.2.0/24 !saddr=192.0.2.9", "iif=wlo1 ip6 saddr=2001:db8::/64",
+		"iif=enp2s0 ip4 saddr=198.51.100.0/24",
+	}
+	if got := describeTagged(state, "input", "policy:1"); !reflect.DeepEqual(got, want) {
+		t.Errorf("lan->fw policy = %q, want %q", got, want)
+	}
+	for chain, rules := range state.Rules {
+		for _, r := range rules {
+			var fam byte
+			for i, e := range r.Exprs {
+				if m, ok := e.(*expr.Meta); ok && m.Key == expr.MetaKeyNFPROTO {
+					fam = r.Exprs[i+1].(*expr.Cmp).Data[0]
+				}
+				p, ok := e.(*expr.Payload)
+				if !ok || p.Base != expr.PayloadBaseNetworkHeader {
+					continue
+				}
+				if p.Len == 4 && fam != unix.NFPROTO_IPV4 || p.Len == 16 && fam != unix.NFPROTO_IPV6 {
+					t.Errorf("%s %s: %d-byte address compare without its family guard: %s", chain, r.Tag, p.Len, describeRule(r))
+				}
+			}
+		}
+	}
+}
+
+func TestCompile_FirewallSelfPolicySkipped(t *testing.T) {
+	for _, action := range []config.PolicyAction{config.PolicyAccept, config.PolicyDrop} {
+		t.Run(string(action), func(t *testing.T) {
+			state := mustCompile(t, listCfg(func(c *config.Config) {
+				c.Policy = []config.Policy{
+					{Source: "fw", Dest: "fw", Action: action},
+					{Source: "net", Dest: "fw", Action: config.PolicyDrop, Log: "info"},
+				}
+			}))
+			for _, chain := range []string{"input", "output", "forward"} {
+				if got := taggedRules(state, chain, "policy:0"); len(got) != 0 {
+					t.Errorf("fw->fw emitted %d rules in %s", len(got), chain)
+				}
+			}
+			got := taggedRules(state, "input", "policy:1")
+			if len(got) != 1 || describeRule(got[0]) != "iif=eth0" {
+				t.Errorf("net->fw input rules = %d, want one scoped to eth0", len(got))
+			}
+		})
+	}
+}
+
+func TestCompile_DestPlusOverridesIntraZone(t *testing.T) {
+	state := mustCompile(t, listCfg(func(c *config.Config) {
+		c.Zones["lxd"] = config.Zone{Type: config.ZoneIP}
+		c.Interfaces = append(c.Interfaces, config.Interface{Zone: "lxd", Interface: "lxdbr0"}, config.Interface{Zone: "lxd", Interface: "docker0"})
+		c.Policy = []config.Policy{{Source: "lxd", Dest: "all+", Action: config.PolicyDrop}}
+	}))
+	if got := taggedRules(state, "forward", "intra:lxd"); len(got) != 0 {
+		t.Errorf("lxd all+ must override implicit intra-zone accept, got %d rules", len(got))
+	}
+	if got := taggedRules(state, "forward", "policy:0"); len(got) == 0 {
+		t.Error("lxd all+ emitted no forward rules")
+	}
+}
+
+func TestCompile_HostsIntraZone(t *testing.T) {
+	state := mustCompile(t, hostsCfg(nil))
+	want := []string{
+		"iif=wlo1 ip4 saddr=192.0.2.0/24 oif=enp2s0 ip4 daddr=198.51.100.0/24",
+		"iif=enp2s0 ip4 saddr=198.51.100.0/24 oif=wlo1 ip4 daddr=192.0.2.0/24",
+	}
+	if got := describeTagged(state, "forward", "intra:lan"); !reflect.DeepEqual(got, want) {
+		t.Errorf("lan intra = %q, want %q", got, want)
+	}
+	want = []string{
+		"iif=wlo1 ip4 !saddr=192.0.2.0/24 oif=enp2s0 ip4 !daddr=198.51.100.0/24",
+		"iif=wlo1 ip6 oif=enp2s0 ip6",
+		"iif=enp2s0 ip4 !saddr=198.51.100.0/24 oif=wlo1 ip4 !daddr=192.0.2.0/24",
+		"iif=enp2s0 ip6 oif=wlo1 ip6",
+	}
+	if got := describeTagged(state, "forward", "intra:net"); !reflect.DeepEqual(got, want) {
+		t.Errorf("net intra = %q, want %q", got, want)
+	}
+
+	state = mustCompile(t, hostsCfg(func(c *config.Config) {
+		c.Policy = append([]config.Policy{{Source: "lan", Dest: "lan", Action: config.PolicyDrop}}, c.Policy...)
+	}))
+	if got := describeTagged(state, "forward", "intra:lan"); len(got) != 0 {
+		t.Errorf("explicit lan lan policy must replace implicit accept, got %q", got)
+	}
+	want = []string{
+		"iif=wlo1 ip4 saddr=192.0.2.0/24 oif=enp2s0 ip4 daddr=198.51.100.0/24",
+		"iif=enp2s0 ip4 saddr=198.51.100.0/24 oif=wlo1 ip4 daddr=192.0.2.0/24",
+	}
+	if got := describeTagged(state, "forward", "policy:0"); !reflect.DeepEqual(got, want) {
+		t.Errorf("lan lan policy = %q, want %q", got, want)
+	}
+}
+
+func TestCompile_HostsRouteBack(t *testing.T) {
+	sameIface := func(routeback bool) func(*config.Config) {
+		return func(c *config.Config) {
+			c.Hosts = []config.Host{
+				{Zone: "lan", Interface: "wlo1", Addresses: []string{"192.0.2.0/24"}, Options: config.HostOptions{RouteBack: routeback}},
+				{Zone: "lan", Interface: "wlo1", Addresses: []string{"198.51.100.0/24"}},
+			}
+		}
+	}
+	if got := describeTagged(mustCompile(t, hostsCfg(sameIface(false))), "forward", "intra:lan"); len(got) != 0 {
+		t.Errorf("same-interface hosts without routeback = %q, want none", got)
+	}
+	want := []string{"iif=wlo1 ip4 saddr=192.0.2.0/24 oif=wlo1 ip4 daddr=192.0.2.0/24"}
+	if got := describeTagged(mustCompile(t, hostsCfg(sameIface(true))), "forward", "intra:lan"); !reflect.DeepEqual(got, want) {
+		t.Errorf("routeback hosts intra = %q, want %q", got, want)
+	}
+
+	state := mustCompile(t, hostsCfg(func(c *config.Config) {
+		sameIface(true)(c)
+		c.Policy = append([]config.Policy{{Source: "lan", Dest: "lan", Action: config.PolicyDrop}}, c.Policy...)
+	}))
+	if got := describeTagged(state, "forward", "policy:0"); !reflect.DeepEqual(got, want) {
+		t.Errorf("routeback hosts lan lan policy = %q, want %q", got, want)
+	}
+}

internal/shorewall/convert.go

@@ -248,6 +248,9 @@ func convertInterfaces(dir string, cfg *config.Config, params map[string]string)
 	for _, row := range rows {
 		zone := subst(field(row, 0), params)
 		iface := subst(field(row, 1), params)
+		if isDash(zone) {
+			zone = ""
+		}
 
 		intf := config.Interface{
 			Zone:      zone,
@@ -392,12 +395,14 @@ func convertHosts(dir string, cfg *config.Config, params map[string]string) erro
 		zone := subst(field(row, 0), params)
 		hostDef := subst(field(row, 1), params)
 
+		hostDef, excl, _ := strings.Cut(hostDef, "!")
 		iface, addrs := splitHostDef(hostDef)
 
 		host := config.Host{
-			Zone:      zone,
+			Zone:       zone,
-			Interface: iface,
+			Interface:  iface,
-			Addresses: addrs,
+			Addresses:  addrs,
+			Exclusions: splitAddrList(excl),
 		}
 
 		optsStr := subst(field(row, 2), params)
@@ -415,16 +420,19 @@ func splitHostDef(s string) (string, []string) {
 	if idx < 0 {
 		return s, nil
 	}
-	iface := s[:idx]
+	return s[:idx], splitAddrList(s[idx+1:])
-	addrPart := s[idx+1:]
+}
+
+// splitAddrList splits a comma address list, unwrapping shorewall6 [addr]/len brackets.
+func splitAddrList(s string) []string {
 	var addrs []string
-	for _, a := range strings.Split(addrPart, ",") {
+	for _, a := range strings.Split(s, ",") {
-		a = strings.TrimSpace(a)
+		a = strings.NewReplacer("[", "", "]", "").Replace(strings.TrimSpace(a))
 		if a != "" {
 			addrs = append(addrs, a)
 		}
 	}
-	return iface, addrs
+	return addrs
 }
 
 func parseHostOptions(s string) config.HostOptions {

internal/shorewall/convert_test.go

@@ -3,6 +3,7 @@ package shorewall
 import (
 	"os"
 	"path/filepath"
+	"reflect"
 	"testing"
 
 	"git.unkin.net/unkin/tomswall/internal/config"
@@ -776,3 +777,30 @@ func TestConvert_LogLimit(t *testing.T) {
 		}
 	}
 }
+
+func TestConvert_HostsExclusions(t *testing.T) {
+	dir := minimalShorewallDir(t)
+	writeFile(t, dir, "interfaces", `
+net eth0
+- eth1
+`)
+	writeFile(t, dir, "hosts", `
+loc eth0:192.0.2.0/24,198.51.100.0/24!192.0.2.7,192.0.2.8 routeback
+loc eth1:[2001:db8::]/64
+`)
+	cfg, err := Convert(dir)
+	if err != nil {
+		t.Fatalf("Convert: %v", err)
+	}
+	want := []config.Host{
+		{Zone: "loc", Interface: "eth0", Addresses: []string{"192.0.2.0/24", "198.51.100.0/24"},
+			Exclusions: []string{"192.0.2.7", "192.0.2.8"}, Options: config.HostOptions{RouteBack: true}},
+		{Zone: "loc", Interface: "eth1", Addresses: []string{"2001:db8::/64"}},
+	}
+	if !reflect.DeepEqual(cfg.Hosts, want) {
+		t.Errorf("hosts = %+v, want %+v", cfg.Hosts, want)
+	}
+	if err := cfg.Validate(); err != nil {
+		t.Errorf("Validate: %v", err)
+	}
+}