Build Housecarl 0.1.0: the nftables firewall manager

Zones, address sets (IPv4 and IPv6 mixed, dynamic sets with timeouts) and
services, ordered rules in the early, input, forward and output chains,
port forwards with hairpin NAT and IPv6 pinholes, source NAT, redirects,
and switchable built-ins (loopback, conntrack, ICMPv6, antispoofing, MSS
clamping, DHCPv6 client, flowtable). Every change is validated, checked
with nft -c and applied in one transaction to Housecarl's own table,
inet housecarl; changes made over the network roll back unless
confirmed, and the confirmed ruleset is loaded at boot by
housecarl-ruleset.service. An empty configuration applies nothing.

Also: hit counters and the drop log (nflog), 'hc import' of an existing
nftables ruleset and 'hc takeover', the hc CLI, the REST API and the web
UI, users, scoped tokens (sets:write:NAME), the audit log, the web UI's
certificate through Jarl, Debian packages, docs, unit tests with real
nft 1.1.3, and an e2e test with real traffic (71 checks).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/model/resolve.go

@@ -0,0 +1,95 @@
+package model
+
+// FamilyRefs are a reference list's part for one address family: names of
+// sets that have entries of the family (dynamic sets always do), and
+// literal entries.
+type FamilyRefs struct {
+	Sets     []string
+	Literals []string
+}
+
+// Empty reports whether nothing of the family was referenced.
+func (f FamilyRefs) Empty() bool { return len(f.Sets) == 0 && len(f.Literals) == 0 }
+
+// SplitRefs splits source or destination references by family. Unknown
+// names are left out (validation reports them).
+func (st *State) SplitRefs(refs []string) (v4, v6 FamilyRefs) {
+	for _, r := range refs {
+		if a, err := ParseAddress(r); err == nil {
+			if a.IsV6() {
+				v6.Literals = append(v6.Literals, a.String())
+			} else {
+				v4.Literals = append(v4.Literals, a.String())
+			}
+			continue
+		}
+		s := st.Set(r)
+		if s == nil {
+			continue
+		}
+		has4, has6 := s.Families()
+		if has4 {
+			v4.Sets = append(v4.Sets, s.Name)
+		}
+		if has6 {
+			v6.Sets = append(v6.Sets, s.Name)
+		}
+	}
+	return v4, v6
+}
+
+// Families reports which families a set holds: a dynamic set may get
+// either at run time.
+func (s *AddressSet) Families() (v4, v6 bool) {
+	if s.Dynamic {
+		return true, true
+	}
+	for _, e := range s.Entries {
+		if a, err := ParseAddress(e); err == nil {
+			if a.IsV6() {
+				v6 = true
+			} else {
+				v4 = true
+			}
+		}
+	}
+	return v4, v6
+}
+
+// FamilyEntries returns a set's static entries of one family.
+func (s *AddressSet) FamilyEntries(v6 bool) []string {
+	var out []string
+	for _, e := range s.Entries {
+		if a, err := ParseAddress(e); err == nil && a.IsV6() == v6 {
+			out = append(out, a.String())
+		}
+	}
+	return out
+}
+
+// ServiceEntries resolves service references (names and entries) to
+// entries, without duplicates. Unknown names are left out.
+func (st *State) ServiceEntries(refs []string) []ServiceEntry {
+	var out []ServiceEntry
+	seen := map[string]bool{}
+	add := func(s string) {
+		e, err := ParseServiceEntry(s)
+		if err != nil || seen[e.String()] {
+			return
+		}
+		seen[e.String()] = true
+		out = append(out, e)
+	}
+	for _, r := range refs {
+		if IsServiceEntry(r) {
+			add(r)
+			continue
+		}
+		if svc := st.Service(r); svc != nil {
+			for _, e := range svc.Entries {
+				add(e)
+			}
+		}
+	}
+	return out
+}