Import code, preparing for release

doh.go

@@ -0,0 +1,99 @@
+package ctrld
+
+import (
+	"context"
+	"crypto/tls"
+	"encoding/base64"
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"time"
+
+	"github.com/lucas-clemente/quic-go"
+	"github.com/lucas-clemente/quic-go/http3"
+	"github.com/miekg/dns"
+)
+
+func newDohResolver(uc *UpstreamConfig) *dohResolver {
+	http.DefaultTransport.(*http.Transport).DialContext = func(ctx context.Context, network, addr string) (net.Conn, error) {
+		dialer := &net.Dialer{
+			Timeout:   10 * time.Second,
+			KeepAlive: 10 * time.Second,
+		}
+		Log(ctx, ProxyLog.Debug(), "debug dial context %s - %s - %s", addr, network, bootstrapDNS)
+		// if we have a bootstrap ip set, use it to avoid DNS lookup
+		if uc.BootstrapIP != "" && addr == fmt.Sprintf("%s:443", uc.Domain) {
+			addr = fmt.Sprintf("%s:443", uc.BootstrapIP)
+			Log(ctx, ProxyLog.Debug(), "sending doh request to: %s", addr)
+		}
+		return dialer.DialContext(ctx, network, addr)
+	}
+	r := &dohResolver{endpoint: uc.Endpoint, isDoH3: uc.Type == resolverTypeDOH3}
+	if r.isDoH3 {
+		r.doh3DialFunc = func(ctx context.Context, addr string, tlsCfg *tls.Config, cfg *quic.Config) (quic.EarlyConnection, error) {
+			host := addr
+			Log(ctx, ProxyLog.Debug(), "debug dial context D0H3 %s - %s", addr, bootstrapDNS)
+			// if we have a bootstrap ip set, use it to avoid DNS lookup
+			if uc.BootstrapIP != "" && addr == fmt.Sprintf("%s:443", uc.Domain) {
+				addr = fmt.Sprintf("%s:443", uc.BootstrapIP)
+				Log(ctx, ProxyLog.Debug(), "sending doh3 request to: %s", addr)
+			}
+			remoteAddr, err := net.ResolveUDPAddr("udp", addr)
+			if err != nil {
+				return nil, err
+			}
+			udpConn, err := net.ListenUDP("udp", &net.UDPAddr{IP: net.IPv4zero, Port: 0})
+			if err != nil {
+				return nil, err
+			}
+			return quic.DialEarlyContext(ctx, udpConn, remoteAddr, host, tlsCfg, cfg)
+		}
+	}
+	return r
+}
+
+type dohResolver struct {
+	endpoint     string
+	isDoH3       bool
+	doh3DialFunc func(ctx context.Context, addr string, tlsCfg *tls.Config, cfg *quic.Config) (quic.EarlyConnection, error)
+}
+
+func (r *dohResolver) Resolve(ctx context.Context, msg *dns.Msg) (*dns.Msg, error) {
+	data, err := msg.Pack()
+	if err != nil {
+		return nil, err
+	}
+	enc := base64.RawURLEncoding.EncodeToString(data)
+	url := fmt.Sprintf("%s?dns=%s", r.endpoint, enc)
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+	if err != nil {
+		return nil, fmt.Errorf("could not create request: %w", err)
+	}
+	req.Header.Set("Content-Type", "application/dns-message")
+	req.Header.Set("Accept", "application/dns-message")
+
+	c := http.Client{}
+	if r.isDoH3 {
+		c.Transport = &http3.RoundTripper{}
+		c.Transport.(*http3.RoundTripper).Dial = r.doh3DialFunc
+		defer c.Transport.(*http3.RoundTripper).Close()
+	}
+	resp, err := c.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("could not perform request: %w", err)
+	}
+	defer resp.Body.Close()
+
+	buf, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, fmt.Errorf("could not read message from response: %w", err)
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("wrong response from DOH server, got: %s, status: %d", string(buf), resp.StatusCode)
+	}
+
+	answer := new(dns.Msg)
+	return answer, answer.Unpack(buf)
+}