meta-google: gbmc-ncsi-config: Restrict accepted hostnames

We only want to allow valid prod hostnames such as `jtyl0` or `fgh10`
and not hostnames like `ovss`.

Change-Id: I0acf9405ff331a06526a52fe1b410458b122893a
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/meta-google/recipes-google/ncsi/files/gbmc-ncsi-ip-from-ra.sh.in b/meta-google/recipes-google/ncsi/files/gbmc-ncsi-ip-from-ra.sh.in
index bd2f2be..6255f70 100755
--- a/meta-google/recipes-google/ncsi/files/gbmc-ncsi-ip-from-ra.sh.in
+++ b/meta-google/recipes-google/ncsi/files/gbmc-ncsi-ip-from-ra.sh.in
@@ -108,7 +108,7 @@
       pfx="$(ip_bytes_to_str t_pfx_b)"
       (( t_pfx_b[9] &= 0xf0 ))
       stateless_pfx="$(ip_bytes_to_str t_pfx_b)"
-    elif [[ "$line" =~ ^'DNS search list'' '*:' '*([^.-]*)[^.]*[.](.*.google.com)$ ]]; then
+    elif [[ "$line" =~ ^'DNS search list'' '*:' '*([a-z]+[0-9]+)[^.]*[.](.*.google.com)$ ]]; then
       host="${BASH_REMATCH[1]}"
       domain="${BASH_REMATCH[2]}"
     elif [[ "$line" =~ ^from' '(.*)$ ]]; then