[source] dnsmasq: write atomic host file

[LEDE Commits]

dedeckeh pushed a commit to source.git, branch master:
https://git.lede-project.org/a39ddff4287e760f44a2d7bb44be364a0061d4bf

commit a39ddff4287e760f44a2d7bb44be364a0061d4bf
Author: Hans Dedecker <dedeckeh at gmail.com>
AuthorDate: Thu Dec 7 10:11:50 2017 +0100

    dnsmasq: write atomic host file
    
    Different invocations of the dnsmasq init script (e.g. at startup by procd)
    will rewrite the dhcp host file which might result into dnsmasq reading an
    empty dhcp host file as it is being rewritten by the dnsmasq init script.
    Let the dnsmasq init script first write to a temp dhcp host file so it does
    not overwrite the contents of the existing dhcp host file.
    
    Reported-by: Hartmut Birr <e9hack at gmail.com>
    Signed-off-by: Hans Dedecker <dedeckeh at gmail.com>
---
 package/network/services/dnsmasq/Makefile           | 2 +-
 package/network/services/dnsmasq/files/dnsmasq.init | 8 +++++---
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/package/network/services/dnsmasq/Makefile b/package/network/services/dnsmasq/Makefile
index 480a8a9..59beb98 100644
--- a/package/network/services/dnsmasq/Makefile
+++ b/package/network/services/dnsmasq/Makefile
@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=dnsmasq
 PKG_VERSION:=2.78
-PKG_RELEASE:=5
+PKG_RELEASE:=6
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.xz
 PKG_SOURCE_URL:=http://thekelleys.org.uk/dnsmasq/
diff --git a/package/network/services/dnsmasq/files/dnsmasq.init b/package/network/services/dnsmasq/files/dnsmasq.init
index 8c40f3b..b84f531 100644
--- a/package/network/services/dnsmasq/files/dnsmasq.init
+++ b/package/network/services/dnsmasq/files/dnsmasq.init
@@ -294,7 +294,7 @@ dhcp_host_add() {
 
 	config_get_bool dns "$cfg" dns 0
 	[ "$dns" = "1" -a -n "$ip" -a -n "$name" ] && {
-		echo "$ip $name${DOMAIN:+.$DOMAIN}" >> $HOSTFILE
+		echo "$ip $name${DOMAIN:+.$DOMAIN}" >> $HOSTFILE_TMP
 	}
 
 	config_get mac "$cfg" mac
@@ -635,7 +635,7 @@ dhcp_domain_add() {
 		record="${record:+$record }$name"
 	done
 
-	echo "$ip $record" >> $HOSTFILE
+	echo "$ip $record" >> $HOSTFILE_TMP
 }
 
 dhcp_srv_add() {
@@ -741,6 +741,7 @@ dnsmasq_start()
 	CONFIGFILE="${BASECONFIGFILE}.${cfg}"
 	CONFIGFILE_TMP="${CONFIGFILE}.$$"
 	HOSTFILE="${BASEHOSTFILE}.${cfg}"
+	HOSTFILE_TMP="${HOSTFILE}.$$"
 	BASEDHCPSTAMPFILE_CFG="${BASEDHCPSTAMPFILE}.${cfg}"
 
 	# before we can call xappend
@@ -751,7 +752,7 @@ dnsmasq_start()
 	chown dnsmasq:dnsmasq /var/run/dnsmasq
 
 	echo "# auto-generated config file from /etc/config/dhcp" > $CONFIGFILE_TMP
-	echo "# auto-generated config file from /etc/config/dhcp" > $HOSTFILE
+	echo "# auto-generated config file from /etc/config/dhcp" > $HOSTFILE_TMP
 
 	local dnsmasqconffile="/etc/dnsmasq.${cfg}.conf"
 	if [ ! -r "$dnsmasqconffile" ]; then
@@ -998,6 +999,7 @@ dnsmasq_start()
 
 	echo >> $CONFIGFILE_TMP
 	mv -f $CONFIGFILE_TMP $CONFIGFILE
+	mv -f $HOSTFILE_TMP $HOSTFILE
 
 	[ "$resolvfile" = "/tmp/resolv.conf.auto" ] && {
 		rm -f /tmp/resolv.conf