From 635d8b298848ff0e8e634c61d23fc318ab55d8d0 Mon Sep 17 00:00:00 2001
From: Chris Novakovic <chris@chrisn.me.uk>
Date: Sun, 9 Jul 2017 00:04:01 +0100
Subject: [PATCH] initramfs: enable DNS if network is up

In certain situations, it is desirable for hostnames to be resolvable in
the initramfs (e.g., when a hostname is specified as the NFS server in
the "boot" or "disk" kernel parameters). If the network is up when the
init script is executed (e.g., when the "ip" kernel parameter is
specified) and a DNS server is known, write it to /etc/resolv.conf so it
can be used for DNS requests.
---
 packages/devel/glibc/config/nsswitch-init.conf         |  3 +++
 .../config/{nsswitch.conf => nsswitch-target.conf}     |  0
 packages/devel/glibc/package.mk                        | 10 +++++++++-
 packages/sysutils/busybox/scripts/init                 |  4 ++++
 4 files changed, 16 insertions(+), 1 deletion(-)
 create mode 100644 packages/devel/glibc/config/nsswitch-init.conf
 rename packages/devel/glibc/config/{nsswitch.conf => nsswitch-target.conf} (100%)

diff --git a/packages/devel/glibc/config/nsswitch-init.conf b/packages/devel/glibc/config/nsswitch-init.conf
new file mode 100644
index 0000000000..eba159e8fc
--- /dev/null
+++ b/packages/devel/glibc/config/nsswitch-init.conf
@@ -0,0 +1,3 @@
+# This is just enough to get DNS resolution working in the initramfs
+
+hosts:		dns
diff --git a/packages/devel/glibc/config/nsswitch.conf b/packages/devel/glibc/config/nsswitch-target.conf
similarity index 100%
rename from packages/devel/glibc/config/nsswitch.conf
rename to packages/devel/glibc/config/nsswitch-target.conf
diff --git a/packages/devel/glibc/package.mk b/packages/devel/glibc/package.mk
index 31fb59aeda..a9d589f94e 100644
--- a/packages/devel/glibc/package.mk
+++ b/packages/devel/glibc/package.mk
@@ -151,7 +151,7 @@ post_makeinstall_target() {
 
 # create default configs
   mkdir -p $INSTALL/etc
-    cp $PKG_DIR/config/nsswitch.conf $INSTALL/etc
+    cp $PKG_DIR/config/nsswitch-target.conf $INSTALL/etc/nsswitch.conf
     cp $PKG_DIR/config/host.conf $INSTALL/etc
     cp $PKG_DIR/config/gai.conf $INSTALL/etc
 
@@ -176,8 +176,16 @@ makeinstall_init() {
     cp -PR $PKG_BUILD/.$TARGET_NAME/math/libm.so* $INSTALL/usr/lib
     cp -PR $PKG_BUILD/.$TARGET_NAME/nptl/libpthread.so* $INSTALL/usr/lib
     cp -PR $PKG_BUILD/.$TARGET_NAME/rt/librt.so* $INSTALL/usr/lib
+    cp -PR $PKG_BUILD/.$TARGET_NAME/resolv/libnss_dns.so* $INSTALL/usr/lib
+    cp -PR $PKG_BUILD/.$TARGET_NAME/resolv/libresolv.so* $INSTALL/usr/lib
 
     if [ "$TARGET_ARCH" = "arm" -a "$TARGET_FLOAT" = "hard" ]; then
       ln -sf ld.so $INSTALL/usr/lib/ld-linux.so.3
     fi
 }
+
+post_makeinstall_init() {
+# create default configs
+  mkdir -p $INSTALL/etc
+    cp $PKG_DIR/config/nsswitch-init.conf $INSTALL/etc/nsswitch.conf
+}
diff --git a/packages/sysutils/busybox/scripts/init b/packages/sysutils/busybox/scripts/init
index 20f8651fd7..b1bf4a93d6 100755
--- a/packages/sysutils/busybox/scripts/init
+++ b/packages/sysutils/busybox/scripts/init
@@ -1003,6 +1003,10 @@
     [ -f "/sysroot/usr/lib/systemd/systemd" ] || error "final_check" "Could not find systemd!"
   }
 
+  # If the network is up (due to the use of the "ip" kernel parameter) and a DNS
+  # server is known, allow the libc resolver to use it
+  grep '^\(nameserver\|domain\) ' /proc/net/pnp | grep -v '^nameserver 0\.0\.0\.0$' > /etc/resolv.conf
+
   if [ "${boot%%=*}" = "FILE" ]; then
     error "check arguments" "boot argument can't be FILE type..."
   fi