From bebdc1b5bc8bcefe4b31743033d45d098a81b0ff Mon Sep 17 00:00:00 2001
From: Simon Zolin <s.zolin@adguard.com>
Date: Wed, 17 Apr 2019 14:53:52 +0300
Subject: [PATCH] + control: use our own DNS resolver instead of system default

---
 control.go |  7 ++++++-
 helpers.go | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 52 insertions(+), 1 deletion(-)

diff --git a/control.go b/control.go
index fe81eaa2..8ded7372 100644
--- a/control.go
+++ b/control.go
@@ -35,8 +35,13 @@ var protocols = []string{"tls://", "https://", "tcp://", "sdns://"}
 const versionCheckURL = "https://adguardteam.github.io/AdGuardHome/version.json"
 const versionCheckPeriod = time.Hour * 8
 
+var transport = &http.Transport{
+	DialContext: customDialContext,
+}
+
 var client = &http.Client{
-	Timeout: time.Minute * 5,
+	Timeout:   time.Minute * 5,
+	Transport: transport,
 }
 
 var controlLock sync.Mutex
diff --git a/helpers.go b/helpers.go
index a304634e..184789d4 100644
--- a/helpers.go
+++ b/helpers.go
@@ -2,6 +2,7 @@ package main
 
 import (
 	"bufio"
+	"context"
 	"errors"
 	"fmt"
 	"io"
@@ -14,7 +15,10 @@ import (
 	"runtime"
 	"strconv"
 	"strings"
+	"time"
 
+	"github.com/AdguardTeam/dnsproxy/upstream"
+	"github.com/AdguardTeam/golibs/log"
 	"github.com/joomcode/errorx"
 )
 
@@ -300,6 +304,48 @@ func checkPacketPortAvailable(host string, port int) error {
 	return err
 }
 
+// Connect to a remote server resolving hostname using our own DNS server
+func customDialContext(ctx context.Context, network, addr string) (net.Conn, error) {
+	log.Tracef("network:%v  addr:%v", network, addr)
+
+	host, port, err := net.SplitHostPort(addr)
+	if err != nil {
+		return nil, err
+	}
+
+	dialer := &net.Dialer{
+		Timeout: time.Minute * 5,
+	}
+
+	if net.ParseIP(host) != nil {
+		con, err := dialer.DialContext(ctx, network, addr)
+		return con, err
+	}
+
+	resolverAddr := fmt.Sprintf("%s:%d", config.DNS.BindHost, config.DNS.Port)
+	r := upstream.NewResolver(resolverAddr, 30*time.Second)
+	addrs, e := r.LookupIPAddr(ctx, host)
+	log.Tracef("LookupIPAddr: %s: %v", host, addrs)
+	if e != nil {
+		return nil, e
+	}
+
+	var firstErr error
+	firstErr = nil
+	for _, a := range addrs {
+		addr = fmt.Sprintf("%s:%s", a.String(), port)
+		con, err := dialer.DialContext(ctx, network, addr)
+		if err != nil {
+			if firstErr == nil {
+				firstErr = err
+			}
+			continue
+		}
+		return con, err
+	}
+	return nil, firstErr
+}
+
 // ---------------------
 // debug logging helpers
 // ---------------------