Mine

#!/bin/sh

. /etc/functions.sh
. ../netifd-proto.sh
init_proto "$@"

dhcp_init_config() {
    proto_config_add_string "ipaddr"
    proto_config_add_string "netmask"
    proto_config_add_string "hostname"
    proto_config_add_string "clientid"
    proto_config_add_string "vendorid"
    proto_config_add_boolean "broadcast"
    proto_config_add_string "reqopts"
}

dhcp_setup() {
    local config="$1"
    local iface="$2"

    json_get_var ipaddr ipaddr
    json_get_var hostname hostname
    json_get_var clientid clientid
    json_get_var vendorid vendorid
    json_get_var broadcast broadcast
    json_get_var reqopts reqopts

    local opt dhcpopts
    for opt in $reqopts; do
        append dhcpopts "-O opt"
    done

    [ "$broadcast" = 1 ] && broadcast="-O broadcast" || broadcast=
   
    proto_export "INTERFACE=$config"
    proto_run_command "$config" udhcpc \
        -p /var/run/udhcpc-$iface.pid \
        -s /lib/netifd/dhcp.script \
        -f -t 0 -i "$iface" \
        ${ipaddr:+-r $ipaddr} \
        ${hostname:+-H $hostname} \
        ${clientid:+-c $clientid} \
        ${vendorid:+-V $vendorid} \
        $broadcast $dhcpopts
}

dhcp_teardown() {
    proto_kill_command
}

dhcp_init() {
    return
}

add_protocol dhcp