kdhcp/server/server.go

package server

import (
	"errors"
	"net"

	log "git.wntrmute.dev/kyle/goutils/syslog"
	"git.wntrmute.dev/kyle/kdhcp/config"
	"git.wntrmute.dev/kyle/kdhcp/dhcp"
)

const (
	MaxPacketSize = 512
)

type Server struct {
	Conn   net.PacketConn
	Config *config.Config
}

func (s *Server) Close() error {
	return s.Conn.Close()
}

func (s *Server) Bind() (err error) {
	// In order to read DHCP packets, we'll need to listen on all addresses.
	ip := net.IP([]byte{0, 0, 0, 0})
	s.Conn, err = BindInterface(ip, s.Config.Port, s.Config.Interface)
	return err
}

func (s *Server) ReadFrom() ([]byte, net.Addr, error) {
	b := make([]byte, MaxPacketSize)
	n, addr, err := s.Conn.ReadFrom(b)
	if err != nil {
		return nil, nil, err
	}

	b = b[:n]
	return b, addr, nil
}

func (s *Server) ReadDHCPRequest() (*dhcp.BootRequest, error) {
	pkt, addr, err := s.ReadFrom()
	if err != nil {
		return nil, err
	}

	log.Debugf("server: read %db packet from %s", len(pkt), addr)
	return dhcp.ReadRequest(pkt)
}

func (s *Server) WriteTo(b []byte, addr net.Addr) error {
	return errors.New("server: not implemented")
}

func (s *Server) AcceptPacket() error {
	request, err := s.ReadDHCPRequest()
	if err != nil {
		return err
	}

	log.Debugf("BOOTP request received from %x", request.HardwareAddress)
	return nil
}

func (s *Server) Listen() {
	for {
		if err := s.AcceptPacket(); err != nil {
			log.Errf("server: error reading packet: %s", err)
			continue
		}
		break
	}
}

func New(cfg *config.Config) (*Server, error) {
	srv := &Server{
		Config: cfg,
	}

	err := srv.Bind()
	if err != nil {
		return nil, err
	}

	log.Infof("server: bound to %s:%s", cfg.Interface, srv.Conn.LocalAddr())

	return srv, nil
}