From 33c8027e0a572a1ebd66d71e41a47380c1973d8a Mon Sep 17 00:00:00 2001
From: Frank Denis <github@pureftpd.org>
Date: Thu, 2 Feb 2023 19:24:40 +0100
Subject: [PATCH] Use a custom dialer for HTTP/3

---
 dnscrypt-proxy/xtransport.go | 36 ++++++++++++++++++++++++++++++++----
 1 file changed, 32 insertions(+), 4 deletions(-)

diff --git a/dnscrypt-proxy/xtransport.go b/dnscrypt-proxy/xtransport.go
index 402ea8ab..e365fa27 100644
--- a/dnscrypt-proxy/xtransport.go
+++ b/dnscrypt-proxy/xtransport.go
@@ -22,8 +22,9 @@ import (
 
 	"github.com/jedisct1/dlog"
 	stamps "github.com/jedisct1/go-dnsstamps"
-	"github.com/quic-go/quic-go/http3"
 	"github.com/miekg/dns"
+	"github.com/quic-go/quic-go"
+	"github.com/quic-go/quic-go/http3"
 	"golang.org/x/net/http2"
 	netproxy "golang.org/x/net/proxy"
 )
@@ -155,7 +156,7 @@ func (xTransport *XTransport) rebuildTransport() {
 					ipOnly = "[" + cachedIP.String() + "]"
 				}
 			} else {
-				dlog.Debugf("[%s] IP address was not cached", host)
+				dlog.Debugf("[%s] IP address was not cached in DialContext", host)
 			}
 			addrStr = ipOnly + ":" + strconv.Itoa(port)
 			if xTransport.proxyDialer == nil {
@@ -223,7 +224,31 @@ func (xTransport *XTransport) rebuildTransport() {
 	}
 	xTransport.transport = transport
 	if xTransport.http3 {
-		h3Transport := &http3.RoundTripper{DisableCompression: true, TLSClientConfig: &tlsClientConfig}
+		h3Transport := &http3.RoundTripper{DisableCompression: true, TLSClientConfig: &tlsClientConfig, Dial: func(ctx context.Context, addrStr string, tlsCfg *tls.Config, cfg *quic.Config) (quic.EarlyConnection, error) {
+			dlog.Debugf("Dialing for H3: [%v]", addrStr)
+			host, port := ExtractHostAndPort(addrStr, stamps.DefaultPort)
+			ipOnly := host
+			cachedIP, _ := xTransport.loadCachedIP(host)
+			if cachedIP != nil {
+				if ipv4 := cachedIP.To4(); ipv4 != nil {
+					ipOnly = ipv4.String()
+				} else {
+					ipOnly = "[" + cachedIP.String() + "]"
+				}
+			} else {
+				dlog.Debugf("[%s] IP address was not cached in H3 DialContext", host)
+			}
+			addrStr = ipOnly + ":" + strconv.Itoa(port)
+			udpAddr, err := net.ResolveUDPAddr("udp", addrStr)
+			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, udpAddr, host, tlsCfg, cfg)
+		}}
 		xTransport.h3Transport = h3Transport
 	}
 }
@@ -401,7 +426,8 @@ func (xTransport *XTransport) Fetch(
 	hasAltSupport := false
 	if xTransport.h3Transport != nil {
 		xTransport.altSupport.RLock()
-		altPort, hasAltSupport := xTransport.altSupport.cache[url.Host]
+		var altPort uint16
+		altPort, hasAltSupport = xTransport.altSupport.cache[url.Host]
 		xTransport.altSupport.RUnlock()
 		if hasAltSupport {
 			if int(altPort) == port {
@@ -456,6 +482,7 @@ func (xTransport *XTransport) Fetch(
 			err = errors.New(resp.Status)
 		}
 	} else {
+		dlog.Debugf("HTTP client error: [%v] - closing idle H3 connections", err)
 		(*xTransport.transport).CloseIdleConnections()
 	}
 	statusCode := 503
@@ -496,6 +523,7 @@ func (xTransport *XTransport) Fetch(
 			}
 			xTransport.altSupport.Lock()
 			xTransport.altSupport.cache[url.Host] = altPort
+			dlog.Debugf("Caching altPort for [%v]", url.Host)
 			xTransport.altSupport.Unlock()
 		}
 	}