package dns import ( "bytes" "context" "crypto/tls" "io/ioutil" "net" "net/http" "github.com/Dreamacro/clash/component/dialer" D "github.com/miekg/dns" ) const ( // dotMimeType is the DoH mimetype that should be used. dotMimeType = "application/dns-message" ) type dohClient struct { url string transport *http.Transport } func (dc *dohClient) Exchange(m *D.Msg) (msg *D.Msg, err error) { return dc.ExchangeContext(context.Background(), m) } func (dc *dohClient) ExchangeContext(ctx context.Context, m *D.Msg) (msg *D.Msg, err error) { req, err := dc.newRequest(m) if err != nil { return nil, err } req = req.WithContext(ctx) return dc.doRequest(req) } // newRequest returns a new DoH request given a dns.Msg. func (dc *dohClient) newRequest(m *D.Msg) (*http.Request, error) { buf, err := m.Pack() if err != nil { return nil, err } req, err := http.NewRequest(http.MethodPost, dc.url, bytes.NewReader(buf)) if err != nil { return req, err } req.Header.Set("content-type", dotMimeType) req.Header.Set("accept", dotMimeType) return req, nil } func (dc *dohClient) doRequest(req *http.Request) (msg *D.Msg, err error) { client := &http.Client{Transport: dc.transport} resp, err := client.Do(req) if err != nil { return nil, err } defer resp.Body.Close() buf, err := ioutil.ReadAll(resp.Body) if err != nil { return nil, err } msg = &D.Msg{} err = msg.Unpack(buf) return msg, err } func newDoHClient(url string, r *Resolver) *dohClient { return &dohClient{ url: url, transport: &http.Transport{ TLSClientConfig: &tls.Config{ClientSessionCache: globalSessionCache}, ForceAttemptHTTP2: true, DialContext: func(ctx context.Context, network, addr string) (net.Conn, error) { host, port, err := net.SplitHostPort(addr) if err != nil { return nil, err } ip, err := r.ResolveIPv4(host) if err != nil { return nil, err } return dialer.DialContext(ctx, "tcp4", net.JoinHostPort(ip.String(), port)) }, }, } }