feat(firewall): implement firewall blocklist feature with client management and policy rules

Introduced a comprehensive firewall blocklist feature, allowing for the management of firewall clients and their associated rules. This includes endpoints for enrolling clients, listing clients and rules, and reporting apply statuses. Enhanced the API to support firewall operations, including the ability to handle block/accept policies. Updated the documentation to reflect these changes and added necessary components in the web UI for better user interaction.

Additionally, modified the agent server to support firewall failover and integrated firewall functionality into the existing architecture.

internal/firewall/policy.go

@@ -0,0 +1,127 @@
+// Package firewall evaluates block/accept policy rules into CIDR blocklists.
+package firewall
+
+import (
+	"crypto/sha256"
+	"encoding/hex"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+// Rule is one ordered firewall policy rule for evaluation.
+type Rule struct {
+	ClientID    *string
+	Priority    int
+	Action      string // "block" | "accept"
+	CommunityID *string
+}
+
+// Evaluate returns a deduplicated flat CIDR list to block in the kernel.
+// communityPrefixes maps community ID to prefixes; key "" holds prefixes without community.
+// Default when no rule matches: accept (do not block).
+func Evaluate(clientID string, rules []Rule, communityPrefixes map[string][]string) []string {
+	ordered := mergeRules(clientID, rules)
+	if len(communityPrefixes) == 0 {
+		return nil
+	}
+	keys := make([]string, 0, len(communityPrefixes))
+	for k := range communityPrefixes {
+		keys = append(keys, k)
+	}
+	sort.Strings(keys)
+
+	var out []string
+	seen := make(map[string]struct{})
+	for _, commKey := range keys {
+		if !shouldBlockCommunity(commKey, ordered) {
+			continue
+		}
+		for _, p := range communityPrefixes[commKey] {
+			p = strings.TrimSpace(p)
+			if p == "" {
+				continue
+			}
+			if _, ok := seen[p]; ok {
+				continue
+			}
+			seen[p] = struct{}{}
+			out = append(out, p)
+		}
+	}
+	return out
+}
+
+func mergeRules(clientID string, rules []Rule) []Rule {
+	var clientRules, tenantRules []Rule
+	for _, r := range rules {
+		if r.ClientID != nil && strings.TrimSpace(*r.ClientID) == clientID {
+			clientRules = append(clientRules, r)
+			continue
+		}
+		if r.ClientID == nil {
+			tenantRules = append(tenantRules, r)
+		}
+	}
+	sort.Slice(clientRules, func(i, j int) bool { return clientRules[i].Priority < clientRules[j].Priority })
+	sort.Slice(tenantRules, func(i, j int) bool { return tenantRules[i].Priority < tenantRules[j].Priority })
+	out := make([]Rule, 0, len(clientRules)+len(tenantRules))
+	out = append(out, clientRules...)
+	out = append(out, tenantRules...)
+	return out
+}
+
+func shouldBlockCommunity(communityKey string, ordered []Rule) bool {
+	for _, r := range ordered {
+		if r.CommunityID == nil || strings.TrimSpace(*r.CommunityID) == communityKey {
+			return strings.EqualFold(strings.TrimSpace(r.Action), "block")
+		}
+	}
+	return false
+}
+
+// RulesVersionHash returns a stable fingerprint of rules for cache headers.
+func RulesVersionHash(rules []Rule) string {
+	if len(rules) == 0 {
+		return "sha256:empty"
+	}
+	cp := append([]Rule(nil), rules...)
+	sort.Slice(cp, func(i, j int) bool {
+		a, b := cp[i], cp[j]
+		ac, bc := "", ""
+		if a.ClientID != nil {
+			ac = *a.ClientID
+		}
+		if b.ClientID != nil {
+			bc = *b.ClientID
+		}
+		if ac != bc {
+			return ac < bc
+		}
+		if a.Priority != b.Priority {
+			return a.Priority < b.Priority
+		}
+		return a.Action < b.Action
+	})
+	var b strings.Builder
+	for _, r := range cp {
+		cid := "*"
+		if r.CommunityID != nil {
+			cid = *r.CommunityID
+		}
+		cl := "tenant"
+		if r.ClientID != nil {
+			cl = *r.ClientID
+		}
+		b.WriteString(cl)
+		b.WriteByte('|')
+		b.WriteString(r.Action)
+		b.WriteByte('|')
+		b.WriteString(cid)
+		b.WriteByte('|')
+		b.WriteString(strconv.Itoa(r.Priority))
+		b.WriteByte(';')
+	}
+	sum := sha256.Sum256([]byte(b.String()))
+	return "sha256:" + hex.EncodeToString(sum[:])
+}