Add DNS support

Includes:
- IP4LL support for setting link local addresses if no dhcp server is found but dhcp is specified
- configurations explicitly set in cmdline will not be overriden by dhcp supplied values, such as binit_net_nss or binit_net_gw

Author: unqueued

README.rst

@@ -74,6 +74,10 @@ binit_net_route=<addr/cidr>
   Optional static on-link route(s) to add (can be given multiple times).
 binit_net_gw=<addr>
   Optional gateway config, if you want to connect via WAN. If ``binit_net_addr`` is set to ``dhcp``, it will be configured automatically.
+binit_net_ns=<addr>
+  Optional dns servers. (can be given multiple times for multiple dns servers). Will override settings for dhcp assigned nameservers if binit_net_addr is set to dhcp.
+binit_net_domain=<domain>
+  Optional dns search domain. This overrides what is set by dhcp.
 rw
   Mount rootfs in read-write. Default: read-only.
 mdev

sourceroot/bin/autoip-query

@@ -2,11 +2,10 @@
 
 # A simple plug for zcap for better-initramfs.
 # Does what dhcp-query would do if dhcp-query fails
-  
 exec > /dhcp-query-result
 
 case "$1" in
     config)
         printf 'binit_net_addr=%s\n' "${ip}"
-    ;;  
+    ;;
 esac

sourceroot/bin/dhcp-query

@@ -8,12 +8,25 @@ exec > /dhcp-query-result
 case "$1" in
     'renew'|'bound')
         printf 'binit_net_addr=%s\n' "${ip}/${mask}"
-        printf 'binit_net_gw=%s\n' "${router}"
 
-	echo -n > /etc/resolv.conf
-	[ -n "$domain" ] && echo search $domain >> /etc/resolv.conf
-	for i in $dns ; do
-		echo nameserver $i >> /etc/resolv.conf
-	done
+        # binit_net_nss, binit_net_domain, and binit_net_gw override dhcp
+
+        if [ -n "${router}" ]; then
+            if [ -z "${binit_net_gw}" ]; then
+                printf 'binit_net_gw="%s"\n' "${router}"
+            fi
+        fi
+
+        if [ -n "${domain}" ]; then
+            if [ -z "${binit_net_domain}" ]; then
+                printf 'binit_net_domain="%s"\n' "${domain}"
+            fi
+        fi
+
+        if [ -n "${dns}" ]; then
+            if [ -z "${binit_net_nss}" ]; then
+                printf 'binit_net_nss="%s"\n' "${dns}"
+            fi
+        fi
     ;;
 esac

sourceroot/functions.sh

@@ -148,6 +148,10 @@ process_commandline_options() {
 			ro|rw)
 				root_rw_ro=$i
 			;;
+			binit_net_ns\=*)
+				# support multiple binit_net_ns=.
+				binit_net_nss="${binit_net_nss} ${i#*=}"
+			;;
 			binit_net_route\=*)
 				# support multiple binit_net_route=.
 				binit_net_routes="${binit_net_routes} ${i#*=}"
@@ -397,6 +401,21 @@ SetupNetwork() {
 		einfo "Setting default routing via '${binit_net_gw}' ..."
 		run ip route add default via "${binit_net_gw}" dev "${binit_net_if}"
 	fi
+
+	if [ -n "${binit_net_domain}" ]; then
+		einfo "Setting search domain to ${binit_net_domain} ..."
+		printf 'search %s\n' "${binit_net_domain}" >> /etc/resolv.conf
+	fi
+
+	if [ -n "${binit_net_nss}" ]; then
+		einfo "Adding nameservers: ${binit_net_nss} ..."
+		set -f
+		for i in ${binit_net_nss}; do
+			printf 'nameserver %s\n' "${i}" >> /etc/resolv.conf
+		done
+		set +f
+	fi
+
 }
 
 setup_sshd() {