dhcp-server: T2669: do not allow overlapping ranges to be created

set service dhcp-server shared-network-name NET01 authoritative
set service dhcp-server shared-network-name NET01 subnet 10.0.0.0/24 default-router '10.0.0.1'
set service dhcp-server shared-network-name NET01 subnet 10.0.0.0/24 lease '86400'
set service dhcp-server shared-network-name NET01 subnet 10.0.0.0/24 range RNG01 start '10.0.0.60'
set service dhcp-server shared-network-name NET01 subnet 10.0.0.0/24 range RNG01 stop '10.0.0.70'
set service dhcp-server shared-network-name NET01 subnet 10.0.0.0/24 range RNG02 start '10.0.0.55'
set service dhcp-server shared-network-name NET01 subnet 10.0.0.0/24 range RNG02 stop '10.0.0.65'

Will result in a dhcpd.conf:

shared-network NET01 {
    authoritative;
    subnet 10.0.0.0 netmask 255.255.255.0 {
        option routers 10.0.0.1;
        default-lease-time 86400;
        max-lease-time 86400;
        range 10.0.0.60 10.0.0.70;
        range 10.0.0.55 10.0.0.65;
    }
    on commit {
        set shared-networkname = "NET01";

    }
}

This is not allowed by ISC DHCPd:

dhcpd[3307]: /run/dhcp-server/dhcpd.conf line 25: lease 10.0.0.63 is declared twice!
dhcpd[3307]:         range 10.0.0.55 10.0.0.65;

1 files changed, 12 insertions, 13 deletions

diff --git a/src/conf_mode/dhcp_server.py b/src/conf_mode/dhcp_server.py
index 0ed09e130..cdee72e09 100755
--- a/src/conf_mode/dhcp_server.py
+++ b/src/conf_mode/dhcp_server.py
@@ -18,6 +18,8 @@ import os
 
 from ipaddress import ip_address
 from ipaddress import ip_network
+from netaddr import IPAddress
+from netaddr import IPRange
 from sys import exit
 
 from vyos.config import Config
@@ -163,8 +165,7 @@ def verify(dhcp):
 
             # Check if DHCP address range is inside configured subnet declaration
             if 'range' in subnet_config:
-                range_start = []
-                range_stop = []
+                networks = []
                 for range, range_config in subnet_config['range'].items():
                     if not {'start', 'stop'} <= set(range_config):
                         raise ConfigError(f'DHCP range "{range}" start and stop address must be defined!')
@@ -179,18 +180,16 @@ def verify(dhcp):
                         raise ConfigError(f'DHCP range "{range}" stop address must be greater or equal\n' \
                                           'to the ranges start address!')
 
-                    # Range start address must be unique
-                    if range_config['start'] in range_start:
-                        raise ConfigError('Conflicting DHCP lease range: Pool start\n' \
-                                          'address "{start}" defined multipe times!'.format(range_config))
+                    for network in networks:
+                        start = range_config['start']
+                        stop = range_config['stop']
+                        if start in network:
+                            raise ConfigError(f'Range "{range}" start address "{start}" already part of another range!')
+                        if stop in network:
+                            raise ConfigError(f'Range "{range}" stop address "{stop}" already part of another range!')
 
-                    # Range stop address must be unique
-                    if range_config['stop'] in range_start:
-                        raise ConfigError('Conflicting DHCP lease range: Pool stop\n' \
-                                          'address "{stop}" defined multipe times!'.format(range_config))
-
-                    range_start.append(range_config['start'])
-                    range_stop.append(range_config['stop'])
+                    tmp = IPRange(range_config['start'], range_config['stop'])
+                    networks.append(tmp)
 
             if 'failover' in subnet_config:
                 for key in ['local_address', 'peer_address', 'name', 'status']: