[Unit]
Description=ISC DHCP IPv4 relay
Documentation=man:dhcrelay(8)
Wants=network-online.target
After=network-online.target
After=time-sync.target
ConditionPathExists=/etc/default/isc-dhcp-relay

[Service]
Type=forking
User=daemon
Group=daemon

AmbientCapabilities=CAP_NET_RAW CAP_NET_BIND_SERVICE
CapabilityBoundingSet=CAP_NET_RAW CAP_NET_BIND_SERVICE

EnvironmentFile=/etc/default/isc-dhcp-relay

Restart=always
RestartSec=1
RestartPreventExitStatus=1 99 127
ExecStart=/bin/ksh93 -c '\
	if [[ -z ${INTERFACES} || -z ${SERVERS} ]]; then \
		print -u2 "Check /etc/default/isc-dhcp-relay."; \
		exit 99; \
	fi; \
    for I in ${INTERFACES}; do OPTIONS+=" -i $I"; done; \
    /usr/sbin/dhcrelay -4 $OPTIONS $SERVERS'

ExecStop=/bin/kill -s SIGTERM $MAINPID

MemoryLow=4M
MemoryMin=2M

[Install]
WantedBy=multi-user.target
Alias=dhcp-relay.service dhcrelay.service