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// Package server4 is a basic, extensible DHCPv4 server.
//
// To use the DHCPv4 server code you have to call NewServer with two arguments:
// - an interface to listen on,
// - an address to listen on, and
// - a handler function, that will be called every time a valid DHCPv4 packet is
// received.
//
// The address to listen on is used to know IP address, port and optionally the
// scope to create and UDP socket to listen on for DHCPv4 traffic.
//
// The handler is a function that takes as input a packet connection, that can
// be used to reply to the client; a peer address, that identifies the client
// sending the request, and the DHCPv4 packet itself. Just implement your
// custom logic in the handler.
//
// Optionally, NewServer can receive options that will modify the server
// object. Some options already exist, for example WithConn. If this option is
// passed with a valid connection, the listening address argument is ignored.
//
// Example program:
//
// package main
//
// import (
// "log"
// "net"
//
// "github.com/insomniacslk/dhcp/dhcpv4"
// "github.com/insomniacslk/dhcp/dhcpv4/server4"
// )
//
// func handler(conn net.PacketConn, peer net.Addr, m *dhcpv4.DHCPv4) {
// // this function will just print the received DHCPv4 message, without replying
// log.Print(m.Summary())
// }
//
// func main() {
// laddr := net.UDPAddr{
// IP: net.ParseIP("127.0.0.1"),
// Port: 67,
// }
// server, err := server4.NewServer("eth0", &laddr, handler)
// if err != nil {
// log.Fatal(err)
// }
//
// // This never returns. If you want to do other stuff, dump it into a
// // goroutine.
// server.Serve()
// }
//
package server4
import (
"log"
"net"
"os"
"github.com/insomniacslk/dhcp/dhcpv4"
)
// Handler is a type that defines the handler function to be called every time a
// valid DHCPv4 message is received
type Handler func(conn net.PacketConn, peer net.Addr, m *dhcpv4.DHCPv4)
// Server represents a DHCPv4 server object
type Server struct {
conn net.PacketConn
Handler Handler
logger Logger
}
// Serve serves requests.
func (s *Server) Serve() error {
s.logger.Printf("Server listening on %s", s.conn.LocalAddr())
s.logger.Printf("Ready to handle requests")
defer s.Close()
for {
rbuf := make([]byte, 4096) // FIXME this is bad
n, peer, err := s.conn.ReadFrom(rbuf)
if err != nil {
s.logger.Printf("Error reading from packet conn: %v", err)
return err
}
s.logger.Printf("Handling request from %v", peer)
m, err := dhcpv4.FromBytes(rbuf[:n])
if err != nil {
s.logger.Printf("Error parsing DHCPv4 request: %v", err)
continue
}
upeer, ok := peer.(*net.UDPAddr)
if !ok {
s.logger.Printf("Not a UDP connection? Peer is %s", peer)
continue
}
// Set peer to broadcast if the client did not have an IP.
if upeer.IP == nil || upeer.IP.To4().Equal(net.IPv4zero) {
upeer = &net.UDPAddr{
IP: net.IPv4bcast,
Port: upeer.Port,
}
}
go s.Handler(s.conn, upeer, m)
}
}
// Close sends a termination request to the server, and closes the UDP listener.
func (s *Server) Close() error {
return s.conn.Close()
}
// ServerOpt adds optional configuration to a server.
type ServerOpt func(s *Server)
// WithConn configures the server with the given connection.
func WithConn(c net.PacketConn) ServerOpt {
return func(s *Server) {
s.conn = c
}
}
// NewServer initializes and returns a new Server object
func NewServer(ifname string, addr *net.UDPAddr, handler Handler, opt ...ServerOpt) (*Server, error) {
s := &Server{
Handler: handler,
logger: EmptyLogger{},
}
for _, o := range opt {
o(s)
}
if s.conn == nil {
var err error
conn, err := NewIPv4UDPConn(ifname, addr)
if err != nil {
return nil, err
}
s.conn = conn
}
return s, nil
}
// WithSummaryLogger logs one-line DHCPv4 message summaries when sent & received.
func WithSummaryLogger() ServerOpt {
return func(s *Server) {
s.logger = ShortSummaryLogger{
Printfer: log.New(os.Stderr, "[dhcpv4] ", log.LstdFlags),
}
}
}
// WithDebugLogger logs multi-line full DHCPv4 messages when sent & received.
func WithDebugLogger() ServerOpt {
return func(s *Server) {
s.logger = DebugLogger{
Printfer: log.New(os.Stderr, "[dhcpv4] ", log.LstdFlags),
}
}
}
// WithLogger set the logger (see interface Logger).
func WithLogger(newLogger Logger) ServerOpt {
return func(s *Server) {
s.logger = newLogger
}
}
|
