[Unit]
Description=%i DHCP Client
IgnoreOnIsolate=yes
DefaultDependencies=no
Conflicts=shutdown.target
Requires=dhcp-init.service
After=dhcp-init.service

[Service]
Restart=always
StartLimitBurst=3
StartLimitInterval=30s
RestartPreventExitStatus=0
Type=simple
PIDFile=/tmp/dhcpcd-%i.pid
ExecStartPre=/usr/syno/lib/systemd/scripts/dhclient.sh pre-start %i
ExecStart=/usr/sbin/dhclient -4 -d -q -lf /tmp/dhcpv4.leases.%i -pf /tmp/dhcpcd-%i.pid -cf /etc/dhclient/ipv4/dhclient.conf -sf /var/run/dhclient-script %i
ExecStopPost=/usr/syno/lib/systemd/scripts/dhclient.sh post-stop %i

[X-Synology]