dhcp-server: T3544: fix FileNotFoundError on first invokation

The problem of using the move() operation over render() is that render will
silently create the directory tree in the background and move() does not.

This means that on first boot when /run/dhcp-server does not exist, move will
fail with a FileNotFoundError.

Instead of using move() we render() the configuration two times, one for
validating it via dhcpd -t and the other time to really apply it to the service.

The performance impact should be little as the config should still be cached in
the system RAM.

(cherry picked from commit 1f68b69328c961e450ac70b12f7bf073d70355d7)

1 files changed, 3 insertions, 4 deletions

diff --git a/src/conf_mode/dhcp_server.py b/src/conf_mode/dhcp_server.py
index af77c6d43..0ed09e130 100755
--- a/src/conf_mode/dhcp_server.py
+++ b/src/conf_mode/dhcp_server.py
@@ -18,7 +18,6 @@ import os
 
 from ipaddress import ip_address
 from ipaddress import ip_network
-from shutil import move
 from sys import exit
 
 from vyos.config import Config
@@ -289,9 +288,9 @@ def generate(dhcp):
         raise ConfigError('Configuration file errors encountered - check your options!')
 
     # Now that we know that the newly rendered configuration is "good" we can
-    # move the temporary configuration to the "real" configuration - we could
-    # also render it two times but that would not be as fast as a move operation
-    move(tmp_file, config_file)
+    # render the "real" configuration
+    render(config_file, 'dhcp-server/dhcpd.conf.tmpl', dhcp,
+           formater=lambda _: _.replace(""", '"'))
 
     return None