From 7b11142efcc621a8cda21214062289a212e605bb Mon Sep 17 00:00:00 2001
From: Shuhao Wu <shuhao@shuhaowu.com>
Date: Thu, 14 Mar 2019 03:01:37 -0400
Subject: [PATCH] Dynamically determine DNS via getprop net.dns

Statically specifying cloudflare's server maybe problematic if you have internal DNS with internal hostnames. This PR uses android's getprop feature to create the DNS resolv.conf entry dynamically.

The caveat is that if the DNS server changes while during a session (disconnect, reconnect elsewhere), there might be an issue. Could add a fallback DNS to 1.1.1.1 in those cases?
---
 ubuntu.sh | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/ubuntu.sh b/ubuntu.sh
index 893b79a..386c592 100755
--- a/ubuntu.sh
+++ b/ubuntu.sh
@@ -29,8 +29,6 @@ if [ "$first" != 1 ];then
 	cd "$folder"
 	echo "decompressing ubuntu image"
 	proot --link2symlink tar -xf ${cur}/${tarball} --exclude='dev'||:
-	echo "fixing nameserver, otherwise it can't connect to the internet"
-	echo "nameserver 1.1.1.1" > etc/resolv.conf
 	cd "$cur"
 fi
 mkdir -p binds
@@ -39,6 +37,18 @@ echo "writing launch script"
 cat > $bin <<- EOM
 #!/bin/bash
 cd \$(dirname \$0)
+## setup resolv.conf
+currentdns="\$(getprop net.dns1)"
+i=1
+
+rm -f $folder/etc/resolv.conf
+
+while [ ! -z "\$currentdns" ]; do
+    echo "nameserver \$currentdns" >> $folder/etc/resolv.conf
+    i=\$((i+1))
+    currentdns=\$(getprop net.dns\${i})
+done
+
 ## unset LD_PRELOAD in case termux-exec is installed
 unset LD_PRELOAD
 command="proot"