From 837563dcd50c262af14bc27f91e30b7ebc917fb7 Mon Sep 17 00:00:00 2001
From: Cuong Manh Le <cuong@windscribe.com>
Date: Sat, 21 Jan 2023 13:19:05 +0700
Subject: [PATCH] all: wait for network up before running

If ctrld setup the interface correctly, the interface DNS is set to
ctrld listener address. At boot time, the ctrld is not up yet, so it
would break the processing Control D config fetching.

Fixing this by waiting for network up before doing the query.
---
 cmd/ctrld/cli.go            |  4 ++++
 cmd/ctrld/net.go            | 30 ++++++++++++++++++++++++++++--
 internal/controld/config.go | 25 ++++++++++++++++++++++++-
 3 files changed, 56 insertions(+), 3 deletions(-)

diff --git a/cmd/ctrld/cli.go b/cmd/ctrld/cli.go
index b48813d..173d1f7 100644
--- a/cmd/ctrld/cli.go
+++ b/cmd/ctrld/cli.go
@@ -103,6 +103,10 @@ func initCLI() {
 			if err := v.Unmarshal(&cfg); err != nil {
 				log.Fatalf("failed to unmarshal config: %v", err)
 			}
+			// Wait for network up.
+			if !netUp() {
+				log.Fatal("network is not up yet")
+			}
 			processCDFlags()
 			if err := ctrld.ValidateConfig(validator.New(), &cfg); err != nil {
 				log.Fatalf("invalid config: %v", err)
diff --git a/cmd/ctrld/net.go b/cmd/ctrld/net.go
index f98feb9..96450c0 100644
--- a/cmd/ctrld/net.go
+++ b/cmd/ctrld/net.go
@@ -1,20 +1,41 @@
 package main
 
 import (
+	"context"
+	"fmt"
 	"net"
 	"sync"
+	"time"
+
+	"tailscale.com/logtail/backoff"
 )
 
-const controldIPv6Test = "ipv6.controld.io"
+const (
+	controldIPv6Test = "ipv6.controld.io"
+	controldIPv4Test = "ipv4.controld.io"
+)
 
 var (
 	stackOnce          sync.Once
 	ipv6Enabled        bool
 	canListenIPv6Local bool
+	hasNetworkUp       bool
 )
 
 func probeStack() {
-	if _, err := net.Dial("tcp6", controldIPv6Test); err == nil {
+	logf := func(format string, args ...any) {
+		fmt.Printf(format, args...)
+	}
+	b := backoff.NewBackoff("probeStack", logf, time.Minute)
+	for {
+		if _, err := net.Dial("tcp", net.JoinHostPort(controldIPv4Test, "80")); err == nil {
+			hasNetworkUp = true
+			break
+		} else {
+			b.BackOff(context.Background(), err)
+		}
+	}
+	if _, err := net.Dial("tcp6", net.JoinHostPort(controldIPv6Test, "80")); err == nil {
 		ipv6Enabled = true
 	}
 	if ln, err := net.Listen("tcp6", "[::1]:53"); err == nil {
@@ -23,6 +44,11 @@ func probeStack() {
 	}
 }
 
+func netUp() bool {
+	stackOnce.Do(probeStack)
+	return hasNetworkUp
+}
+
 func supportsIPv6() bool {
 	stackOnce.Do(probeStack)
 	return ipv6Enabled
diff --git a/internal/controld/config.go b/internal/controld/config.go
index 3ca1c5b..51a1353 100644
--- a/internal/controld/config.go
+++ b/internal/controld/config.go
@@ -2,8 +2,10 @@ package controld
 
 import (
 	"bytes"
+	"context"
 	"encoding/json"
 	"fmt"
+	"net"
 	"net/http"
 	"time"
 )
@@ -13,6 +15,20 @@ const (
 	InvalidConfigCode = 40401
 )
 
+const bootstrapDNS = "76.76.2.0:53"
+
+var dialer = &net.Dialer{
+	Resolver: &net.Resolver{
+		PreferGo: true,
+		Dial: func(ctx context.Context, network, address string) (net.Conn, error) {
+			d := net.Dialer{
+				Timeout: 10 * time.Second,
+			}
+			return d.DialContext(ctx, "udp", bootstrapDNS)
+		},
+	},
+}
+
 // ResolverConfig represents Control D resolver data.
 type ResolverConfig struct {
 	DOH     string   `json:"doh"`
@@ -52,7 +68,14 @@ func FetchResolverConfig(uid string) (*ResolverConfig, error) {
 	q.Set("platform", "ctrld")
 	req.URL.RawQuery = q.Encode()
 	req.Header.Add("Content-Type", "application/json")
-	client := http.Client{Timeout: 5 * time.Second}
+	transport := http.DefaultTransport.(*http.Transport).Clone()
+	transport.DialContext = func(ctx context.Context, network, addr string) (net.Conn, error) {
+		return dialer.DialContext(ctx, network, addr)
+	}
+	client := http.Client{
+		Timeout:   10 * time.Second,
+		Transport: transport,
+	}
 	resp, err := client.Do(req)
 	if err != nil {
 		return nil, fmt.Errorf("client.Do: %w", err)