From 10bc49810e484dc963b3ba7a52915b6085ef17c3 Mon Sep 17 00:00:00 2001
From: Audrius Butkevicius <audrius.butkevicius@gmail.com>
Date: Mon, 28 Mar 2016 10:57:42 -0400
Subject: [PATCH] Patch GO's DNS (fixes #593)

---
 make-go.bash                 |  10 +++
 patches/golang/all/dns.patch | 117 +++++++++++++++++++++++++++++++++++
 2 files changed, 127 insertions(+)
 create mode 100644 patches/golang/all/dns.patch

diff --git a/make-go.bash b/make-go.bash
index 266d371f..30279492 100755
--- a/make-go.bash
+++ b/make-go.bash
@@ -60,6 +60,16 @@ mkdir -p "$GOROOT_FINAL"
 
 pushd ext/golang/go/src
 
+# Apply patches to Golang
+for PATCH in $MYDIR/patches/golang/all/*.patch; do
+    if ! patch -R -p1 --dry-run <$PATCH &>/dev/null; then
+        echo "Applying $PATCH"
+        patch -p1 <$PATCH
+    else
+        echo "Patch $PATCH already applied"
+    fi
+done
+
 set +e
 ./clean.bash
 rm -r ../bin
diff --git a/patches/golang/all/dns.patch b/patches/golang/all/dns.patch
new file mode 100644
index 00000000..dff79d66
--- /dev/null
+++ b/patches/golang/all/dns.patch
@@ -0,0 +1,117 @@
+diff --git a/net/dnsconfig_unix.go b/net/dnsconfig_unix.go
+index 6073fdb..9df3cec 100644
+--- a/net/dnsconfig_unix.go
++++ b/net/dnsconfig_unix.go
+@@ -8,18 +8,57 @@
+ 
+ package net
+ 
+-var defaultNS = []string{"127.0.0.1", "::1"}
++import (
++	"fmt"
++	"os/exec"
++	"strings"
++	"sync"
++	"time"
++)
++
++var (
++	logOnce sync.Once
++)
++
++func getDefaultNS() []string {
++	var servers []string
++	for _, prop := range []string{"net.dns", "net.dns1", "net.dns2", "net.dns3", "net.dns4"} {
++		cmd := exec.Command("getprop", prop)
++		if cmd.Run() == nil {
++			outputBytes, err := cmd.Output()
++			if err != nil {
++				continue
++			}
++
++			output := strings.Trim(string(outputBytes), "\n")
++			if ParseIP(output) != nil {
++				servers = append(servers, output)
++			}
++		}
++	}
++
++	if servers == nil {
++		servers = []string{"8.8.8.8", "8.8.4.4", "4.2.2.1"}
++	}
++
++	logOnce.Do(func() {
++		fmt.Println("Using the following DNS servers", servers)
++	})
++
++	return servers
++}
+ 
+ type dnsConfig struct {
+-	servers    []string // servers to use
+-	search     []string // suffixes to append to local name
+-	ndots      int      // number of dots in name to trigger absolute lookup
+-	timeout    int      // seconds before giving up on packet
+-	attempts   int      // lost packets before giving up on server
+-	rotate     bool     // round robin among servers
+-	unknownOpt bool     // anything unknown was encountered
+-	lookup     []string // OpenBSD top-level database "lookup" order
+-	err        error    // any error that occurs during open of resolv.conf
++	servers    []string  // servers to use
++	search     []string  // suffixes to append to local name
++	ndots      int       // number of dots in name to trigger absolute lookup
++	timeout    int       // seconds before giving up on packet
++	attempts   int       // lost packets before giving up on server
++	rotate     bool      // round robin among servers
++	unknownOpt bool      // anything unknown was encountered
++	lookup     []string  // OpenBSD top-level database "lookup" order
++	err        error     // any error that occurs during open of resolv.conf
++	mtime      time.Time // time of resolv.conf modification
+ }
+ 
+ // See resolv.conf(5) on a Linux machine.
+@@ -33,11 +72,20 @@ func dnsReadConfig(filename string) *dnsConfig {
+ 	}
+ 	file, err := open(filename)
+ 	if err != nil {
+-		conf.servers = defaultNS
++		conf.servers = getDefaultNS()
++		conf.mtime = time.Now()
+ 		conf.err = err
+ 		return conf
+ 	}
+ 	defer file.close()
++	if fi, err := file.file.Stat(); err == nil {
++		conf.mtime = fi.ModTime()
++	} else {
++		conf.mtime = time.Now()
++		conf.servers = getDefaultNS()
++		conf.err = err
++		return conf
++	}
+ 	for line, ok := file.readLine(); ok; line, ok = file.readLine() {
+ 		if len(line) > 0 && (line[0] == ';' || line[0] == '#') {
+ 			// comment.
+@@ -51,7 +99,7 @@ func dnsReadConfig(filename string) *dnsConfig {
+ 		case "nameserver": // add one name server
+ 			if len(f) > 1 && len(conf.servers) < 3 { // small, but the standard limit
+ 				// One more check: make sure server name is
+-				// just an IP address.  Otherwise we need DNS
++				// just an IP address. Otherwise we need DNS
+ 				// to look it up.
+ 				if parseIPv4(f[1]) != nil {
+ 					conf.servers = append(conf.servers, f[1])
+@@ -110,7 +158,7 @@ func dnsReadConfig(filename string) *dnsConfig {
+ 		}
+ 	}
+ 	if len(conf.servers) == 0 {
+-		conf.servers = defaultNS
++		conf.servers = getDefaultNS()
+ 	}
+ 	return conf
+ }
+@@ -118,3 +166,4 @@ func dnsReadConfig(filename string) *dnsConfig {
+ func hasPrefix(s, prefix string) bool {
+ 	return len(s) >= len(prefix) && s[:len(prefix)] == prefix
+ }
++