add reverse_lookup plugin

plugin/enabled_plugin.go

@@ -36,6 +36,7 @@ import (
 	_ "github.com/IrineSistiana/mosdns/v4/plugin/executable/nftset"
 	_ "github.com/IrineSistiana/mosdns/v4/plugin/executable/padding"
 	_ "github.com/IrineSistiana/mosdns/v4/plugin/executable/redirect"
+	_ "github.com/IrineSistiana/mosdns/v4/plugin/executable/reverse_lookup"
 	_ "github.com/IrineSistiana/mosdns/v4/plugin/executable/sequence"
 	_ "github.com/IrineSistiana/mosdns/v4/plugin/executable/single_flight"
 	_ "github.com/IrineSistiana/mosdns/v4/plugin/executable/sleep"

plugin/executable/reverse_lookup/reverse_lookup.go

@@ -0,0 +1,123 @@
+/*
+ * Copyright (C) 2020-2022, IrineSistiana
+ *
+ * This file is part of mosdns.
+ *
+ * mosdns is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * mosdns is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package reverselookup
+
+import (
+	"context"
+	"fmt"
+	"github.com/IrineSistiana/mosdns/v4/coremain"
+	"github.com/IrineSistiana/mosdns/v4/pkg/executable_seq"
+	"github.com/IrineSistiana/mosdns/v4/pkg/query_context"
+	"github.com/miekg/dns"
+	"net"
+	"net/http"
+	"net/netip"
+	"time"
+)
+
+const (
+	PluginType = "reverse_lookup"
+)
+
+func init() {
+	coremain.RegNewPluginFunc(PluginType, Init, func() interface{} { return new(Args) })
+}
+
+var _ coremain.ExecutablePlugin = (*reverseLookup)(nil)
+
+type Args struct {
+	TTL int // Default is 10.
+}
+
+type reverseLookup struct {
+	*coremain.BP
+	args  *Args
+	store *store
+}
+
+func (p *reverseLookup) ServeHTTP(w http.ResponseWriter, req *http.Request) {
+	ipStr := req.URL.Query().Get("ip")
+	addr, err := netip.ParseAddr(ipStr)
+	if err != nil {
+		w.WriteHeader(http.StatusBadRequest)
+		w.Write([]byte(err.Error()))
+		return
+	}
+
+	d := p.store.lookup(addr)
+	w.Write([]byte(d))
+}
+
+func Init(bp *coremain.BP, args interface{}) (p coremain.Plugin, err error) {
+	return newReverseLookup(bp, args.(*Args)), nil
+}
+
+func newReverseLookup(bp *coremain.BP, args *Args) coremain.Plugin {
+	p := &reverseLookup{
+		BP:    bp,
+		args:  args,
+		store: newStore(),
+	}
+
+	bp.M().GetHTTPAPIMux().Handle("/plugins/"+bp.Tag(), p)
+	return p
+}
+
+func (p *reverseLookup) Exec(ctx context.Context, qCtx *query_context.Context, next executable_seq.ExecutableChainNode) error {
+	if err := executable_seq.ExecChainNode(ctx, qCtx, next); err != nil {
+		return err
+	}
+	r := qCtx.R()
+	if r == nil {
+		return nil
+	}
+
+	for _, rr := range r.Answer {
+		var ip net.IP
+		switch rr := rr.(type) {
+		case *dns.A:
+			ip = rr.A
+		case *dns.AAAA:
+			ip = rr.AAAA
+		default:
+			continue
+		}
+		addr, ok := netip.AddrFromSlice(ip)
+		if !ok {
+			return fmt.Errorf("invalid ip %s", ip)
+		}
+
+		h := rr.Header()
+		ttl := uint32(p.args.TTL)
+		if ttl == 0 {
+			ttl = 10
+		}
+		if h.Ttl > ttl {
+			h.Ttl = ttl
+		}
+		p.store.save(rr.Header().Name, time.Duration(ttl)*time.Second, addr)
+	}
+	return nil
+}
+
+func (p *reverseLookup) Close() error {
+	p.store.close()
+	return nil
+}

plugin/executable/reverse_lookup/store.go

@@ -0,0 +1,107 @@
+/*
+ * Copyright (C) 2020-2022, IrineSistiana
+ *
+ * This file is part of mosdns.
+ *
+ * mosdns is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * mosdns is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package reverselookup
+
+import (
+	"net/netip"
+	"sync"
+	"time"
+)
+
+type store struct {
+	sync.RWMutex
+	m map[netip.Addr]*elem
+
+	closeOnce sync.Once
+	closeChan chan struct{}
+}
+
+type elem struct {
+	expire time.Time
+	d      string
+}
+
+func newStore() *store {
+	s := &store{
+		m:         make(map[netip.Addr]*elem),
+		closeChan: make(chan struct{}),
+	}
+
+	go func() {
+		ticker := time.NewTicker(time.Second * 5)
+		defer ticker.Stop()
+
+		for {
+			select {
+			case <-s.closeChan:
+				return
+			case <-ticker.C:
+				s.clean()
+			}
+		}
+	}()
+
+	return s
+}
+
+func (s *store) save(domain string, ttl time.Duration, ip ...netip.Addr) {
+	if len(ip) == 0 {
+		return
+	}
+
+	e := &elem{
+		expire: time.Now().Add(ttl),
+		d:      domain,
+	}
+
+	s.Lock()
+	for _, addr := range ip {
+		s.m[addr] = e
+	}
+	s.Unlock()
+}
+
+func (s *store) lookup(ip netip.Addr) string {
+	s.RLock()
+	defer s.RUnlock()
+	d := s.m[ip]
+	if d == nil {
+		return ""
+	}
+	return d.d
+}
+
+func (s *store) clean() {
+	now := time.Now()
+	s.Lock()
+	defer s.Unlock()
+
+	for addr, e := range s.m {
+		if e.expire.Before(now) {
+			delete(s.m, addr)
+		}
+	}
+}
+
+func (s *store) close() {
+	s.closeOnce.Do(func() {
+		close(s.closeChan)
+	})
+}