package dns import ( "net" "strings" "time" "github.com/Dreamacro/clash/common/cache" "github.com/Dreamacro/clash/component/fakeip" "github.com/Dreamacro/clash/component/trie" "github.com/Dreamacro/clash/log" D "github.com/miekg/dns" ) type handler func(r *D.Msg) (*D.Msg, error) type middleware func(next handler) handler func withHosts(hosts *trie.DomainTrie) middleware { return func(next handler) handler { return func(r *D.Msg) (*D.Msg, error) { q := r.Question[0] if !isIPRequest(q) { return next(r) } record := hosts.Search(strings.TrimRight(q.Name, ".")) if record == nil { return next(r) } ip := record.Data.(net.IP) msg := r.Copy() if v4 := ip.To4(); v4 != nil && q.Qtype == D.TypeA { rr := &D.A{} rr.Hdr = D.RR_Header{Name: q.Name, Rrtype: D.TypeA, Class: D.ClassINET, Ttl: dnsDefaultTTL} rr.A = v4 msg.Answer = []D.RR{rr} } else if v6 := ip.To16(); v6 != nil && q.Qtype == D.TypeAAAA { rr := &D.AAAA{} rr.Hdr = D.RR_Header{Name: q.Name, Rrtype: D.TypeAAAA, Class: D.ClassINET, Ttl: dnsDefaultTTL} rr.AAAA = v6 msg.Answer = []D.RR{rr} } else { return next(r) } msg.SetRcode(r, D.RcodeSuccess) msg.Authoritative = true msg.RecursionAvailable = true return msg, nil } } } func withMapping(mapping *cache.LruCache) middleware { return func(next handler) handler { return func(r *D.Msg) (*D.Msg, error) { q := r.Question[0] if !isIPRequest(q) { return next(r) } msg, err := next(r) if err != nil { return nil, err } host := strings.TrimRight(q.Name, ".") for _, ans := range msg.Answer { var ip net.IP var ttl uint32 switch a := ans.(type) { case *D.A: ip = a.A ttl = a.Hdr.Ttl case *D.AAAA: ip = a.AAAA ttl = a.Hdr.Ttl default: continue } mapping.SetWithExpire(ip.String(), host, time.Now().Add(time.Second*time.Duration(ttl))) } return msg, nil } } } func withFakeIP(fakePool *fakeip.Pool) middleware { return func(next handler) handler { return func(r *D.Msg) (*D.Msg, error) { q := r.Question[0] if q.Qtype == D.TypeAAAA { msg := &D.Msg{} msg.Answer = []D.RR{} msg.SetRcode(r, D.RcodeSuccess) msg.Authoritative = true msg.RecursionAvailable = true return msg, nil } else if q.Qtype != D.TypeA { return next(r) } host := strings.TrimRight(q.Name, ".") if fakePool.LookupHost(host) { return next(r) } rr := &D.A{} rr.Hdr = D.RR_Header{Name: q.Name, Rrtype: D.TypeA, Class: D.ClassINET, Ttl: dnsDefaultTTL} ip := fakePool.Lookup(host) rr.A = ip msg := r.Copy() msg.Answer = []D.RR{rr} setMsgTTL(msg, 1) msg.SetRcode(r, D.RcodeSuccess) msg.Authoritative = true msg.RecursionAvailable = true return msg, nil } } } func withResolver(resolver *Resolver) handler { return func(r *D.Msg) (*D.Msg, error) { q := r.Question[0] // return a empty AAAA msg when ipv6 disabled if !resolver.ipv6 && q.Qtype == D.TypeAAAA { msg := &D.Msg{} msg.Answer = []D.RR{} msg.SetRcode(r, D.RcodeSuccess) msg.Authoritative = true msg.RecursionAvailable = true return msg, nil } msg, err := resolver.Exchange(r) if err != nil { log.Debugln("[DNS Server] Exchange %s failed: %v", q.String(), err) return msg, err } msg.SetRcode(r, msg.Rcode) msg.Authoritative = true return msg, nil } } func compose(middlewares []middleware, endpoint handler) handler { length := len(middlewares) h := endpoint for i := length - 1; i >= 0; i-- { middleware := middlewares[i] h = middleware(h) } return h } func newHandler(resolver *Resolver, mapper *ResolverEnhancer) handler { middlewares := []middleware{} if resolver.hosts != nil { middlewares = append(middlewares, withHosts(resolver.hosts)) } if mapper.mode == FAKEIP { middlewares = append(middlewares, withFakeIP(mapper.fakePool)) } if mapper.mode != NORMAL { middlewares = append(middlewares, withMapping(mapper.mapping)) } return compose(middlewares, withResolver(resolver)) }