plugin: add rdns support

Author: 0xffffharry

docs/plugin/executor/index.md

@@ -22,3 +22,4 @@ workflows:
 - [script](script)
 - [ecs](ecs)
 - [ipset](ipset)
+- [rdns](rdns)

docs/plugin/executor/rdns.md

@@ -0,0 +1,20 @@
+# rDNS IP 反查
+
+rDNS 用于查询 IP 的反向域名，通常用于局域网内
+
+```yaml
+plugin-executors:
+    - tag: plugin
+      type: rdns
+
+workflows:
+    - tag: default
+      rules:
+        - exec:
+            - plugin:
+                tag: plugin
+                args: # 键值对：IP|CIDR: 上游服务器 Tag
+                  '*': upstream-A # '*' 用于匹配任意 IP
+                  '192.168.1.0/24': upstream-Local
+                  'fd00::/8': upstream-Local
+```

mkdocs.yml

@@ -103,4 +103,5 @@ nav:
     - 'rediscache': plugin/executor/rediscache.md
     - 'script': plugin/executor/script.md
     - 'ecs': plugin/executor/ecs.md
-    - 'ipset': plugin/executor/ipset.md
+    - 'ipset': plugin/executor/ipset.md
+    - 'rdns': plugin/executor/rdns.md

plugin/executor/init.go

@@ -4,6 +4,7 @@ import (
 	_ "github.com/rnetx/cdns/plugin/executor/ecs"
 	_ "github.com/rnetx/cdns/plugin/executor/ipset"
 	_ "github.com/rnetx/cdns/plugin/executor/memcache"
+	_ "github.com/rnetx/cdns/plugin/executor/rdns"
 	_ "github.com/rnetx/cdns/plugin/executor/rediscache"
 	_ "github.com/rnetx/cdns/plugin/executor/script"
 )

plugin/executor/rdns/rdns.go

@@ -0,0 +1,186 @@
+package rdns
+
+import (
+	"context"
+	"fmt"
+	"net/netip"
+	"strings"
+
+	"github.com/rnetx/cdns/adapter"
+	"github.com/rnetx/cdns/log"
+	"github.com/rnetx/cdns/plugin"
+	"github.com/rnetx/cdns/utils"
+
+	"github.com/miekg/dns"
+)
+
+const Type = "rdns"
+
+func init() {
+	plugin.RegisterPluginExecutor(Type, NewRDNS)
+}
+
+type rule struct {
+	upstream adapter.Upstream
+	rule     netip.Prefix
+	isAny    bool
+}
+
+var _ adapter.PluginExecutor = (*RDNS)(nil)
+
+type RDNS struct {
+	ctx    context.Context
+	core   adapter.Core
+	tag    string
+	logger log.Logger
+
+	runningArgsMap map[uint16][]rule
+}
+
+func NewRDNS(ctx context.Context, core adapter.Core, logger log.Logger, tag string, _ any) (adapter.PluginExecutor, error) {
+	r := &RDNS{
+		ctx:    ctx,
+		core:   core,
+		tag:    tag,
+		logger: logger,
+	}
+	return r, nil
+}
+
+func (r *RDNS) Tag() string {
+	return r.tag
+}
+
+func (r *RDNS) Type() string {
+	return Type
+}
+
+func (r *RDNS) Exec(ctx context.Context, dnsCtx *adapter.DNSContext, argsID uint16) (adapter.ReturnMode, error) {
+	reqMsg := dnsCtx.ReqMsg()
+	if reqMsg == nil {
+		r.logger.DebugContext(ctx, "request message is nil")
+		return adapter.ReturnModeContinue, nil
+	}
+	q := reqMsg.Question[0]
+	ip := isIPv4rDNS(&q)
+	if !ip.IsValid() {
+		ip = isIPv6rDNS(&q)
+		if !ip.IsValid() {
+			r.logger.DebugContext(ctx, "not a reverse dns query")
+			return adapter.ReturnModeContinue, nil
+		}
+	}
+	rules := r.runningArgsMap[argsID]
+	for _, rule := range rules {
+		if rule.isAny || rule.rule.Contains(ip) {
+			respMsg, err := rule.upstream.Exchange(ctx, reqMsg)
+			if err != nil {
+				return adapter.ReturnModeUnknown, err
+			}
+			dnsCtx.SetRespMsg(respMsg)
+			return adapter.ReturnModeContinue, nil
+		}
+	}
+	return adapter.ReturnModeContinue, nil
+}
+
+func (r *RDNS) LoadRunningArgs(ctx context.Context, args any) (uint16, error) {
+	var rawRuleMap map[string]string
+	err := utils.JsonDecode(args, &rawRuleMap)
+	if err != nil {
+		return 0, err
+	}
+	if len(rawRuleMap) == 0 {
+		return 0, fmt.Errorf("missing rule")
+	}
+	rules := make([]rule, 0, len(rawRuleMap))
+	for ruleStr, upstreamTag := range rawRuleMap {
+		isAny := ruleStr == "*"
+		var prefix netip.Prefix
+		if !isAny {
+			prefix, err = netip.ParsePrefix(ruleStr)
+			if err != nil {
+				ip, err2 := netip.ParseAddr(ruleStr)
+				if err2 != nil {
+					return 0, fmt.Errorf("parse rule failed: %w | %w", err, err2)
+				}
+				bits := 0
+				if ip.Is6() {
+					bits = 128
+				} else {
+					bits = 32
+				}
+				prefix = netip.PrefixFrom(ip, bits)
+			}
+		}
+		u := r.core.GetUpstream(upstreamTag)
+		if u == nil {
+			return 0, fmt.Errorf("upstream [%s] not found", upstreamTag)
+		}
+		rules = append(rules, rule{
+			upstream: u,
+			rule:     prefix,
+			isAny:    isAny,
+		})
+	}
+	if r.runningArgsMap == nil {
+		r.runningArgsMap = make(map[uint16][]rule)
+	}
+	var id uint16
+	for {
+		id = utils.RandomIDUint16()
+		if _, ok := r.runningArgsMap[id]; !ok {
+			break
+		}
+	}
+	r.runningArgsMap[id] = rules
+	return id, nil
+}
+
+func isIPv4rDNS(q *dns.Question) netip.Addr {
+	if q.Qtype == dns.TypePTR && q.Qclass == dns.ClassINET && strings.HasSuffix(q.Name, ".in-addr.arpa.") {
+		name := q.Name[:len(q.Name)-len(".in-addr.arpa.")]
+		ips := strings.Split(name, ".")
+		if len(ips) != 4 {
+			return netip.Addr{}
+		}
+		ipStr := fmt.Sprintf("%s.%s.%s.%s", ips[3], ips[2], ips[1], ips[0])
+		ip, err := netip.ParseAddr(ipStr)
+		if err == nil {
+			if ip.Is4() {
+				return ip
+			}
+		}
+	}
+	return netip.Addr{}
+}
+
+func isIPv6rDNS(q *dns.Question) netip.Addr {
+	if q.Qtype == dns.TypePTR && q.Qclass == dns.ClassINET && strings.HasSuffix(q.Name, ".ip6.arpa.") {
+		name := q.Name[:len(q.Name)-len(".ip6.arpa.")]
+		rawIPStr := ""
+		s := 0
+		m := 0
+		for i := len(name) - 1; i >= 0; i-- {
+			if s == 4 {
+				rawIPStr += ":"
+				m++
+				s = 0
+			}
+			if name[i] != '.' {
+				rawIPStr += string(name[i])
+				s++
+			}
+		}
+		if m != 7 {
+			rawIPStr += "::"
+		}
+		ip, err := netip.ParseAddr(rawIPStr)
+		if err == nil {
+			if ip.Is6() {
+				return ip
+			}
+		}
+	}
+	return netip.Addr{}
+}