dhcpd: added dhcp service (ipv4 only)

feature_linux.go

@@ -2,7 +2,7 @@ package main
 
 import (
 	// comment out the services you don't need to make the compiled binary smaller.
-	// _ "github.com/nadoo/glider/service/xxx"
+	_ "github.com/nadoo/glider/service/dhcpd"
 
 	// comment out the protocols you don't need to make the compiled binary smaller.
 	_ "github.com/nadoo/glider/proxy/redir"

service/dhcpd/dhcpd_linux.go

@@ -0,0 +1,157 @@
+package dhcpd
+
+import (
+	"context"
+	"net"
+	"time"
+
+	"github.com/insomniacslk/dhcp/dhcpv4"
+	"github.com/insomniacslk/dhcp/dhcpv4/nclient4"
+	"github.com/insomniacslk/dhcp/dhcpv4/server4"
+
+	"github.com/nadoo/glider/common/log"
+	"github.com/nadoo/glider/service"
+)
+
+var leaseTime = time.Hour * 12
+
+func init() {
+	service.Register("dhcpd", &dpcpd{})
+}
+
+type dpcpd struct{}
+
+func (*dpcpd) Run(args ...string) {
+	if len(args) < 3 {
+		log.F("[dhcpd] not enough parameters, exiting")
+		return
+	}
+
+	iface, ipStart, ipEnd := args[0], args[1], args[2]
+
+	if detectServer(iface) {
+		log.F("[dhcpd] found existing dhcp server on interface %s, service exiting", iface)
+		return
+	}
+
+	pool, err := NewPool(leaseTime, net.ParseIP(ipStart), net.ParseIP(ipEnd))
+	if err != nil {
+		log.F("[dhcpd] error in pool init: %s", err)
+		return
+	}
+
+	ip, mask := ifaceIPMask4(iface)
+	if ip == nil || mask == nil {
+		log.F("[dhcpd] can not get ip and mask of interface: %s", iface)
+		return
+	}
+
+	server, err := server4.NewServer(
+		iface, &net.UDPAddr{IP: net.IPv4(0, 0, 0, 0), Port: 67}, handleDHCP(ip, mask, pool))
+	if err != nil {
+		log.F("[dhcpd] error in server new: %s", err)
+		return
+	}
+
+	log.F("[dhcpd] listening on interface %s(%s/%d.%d.%d.%d)",
+		iface, ip, mask[0], mask[1], mask[2], mask[3])
+
+	server.Serve()
+}
+
+func handleDHCP(serverIP net.IP, mask net.IPMask, pool *Pool) server4.Handler {
+	return func(conn net.PacketConn, peer net.Addr, m *dhcpv4.DHCPv4) {
+		log.F("[dpcpd] received request from client %v", m.ClientHWAddr)
+
+		var replyType dhcpv4.MessageType
+		switch mt := m.MessageType(); mt {
+		case dhcpv4.MessageTypeDiscover:
+			replyType = dhcpv4.MessageTypeOffer
+		case dhcpv4.MessageTypeRequest:
+			replyType = dhcpv4.MessageTypeAck
+		default:
+			log.F("[dpcpd] can't handle type %v", mt)
+			return
+		}
+
+		replyIp, err := pool.AssignIP(m.ClientHWAddr)
+		if err != nil {
+			log.F("[dpcpd] can not assign IP error %s", err)
+			return
+		}
+
+		reply, err := dhcpv4.NewReplyFromRequest(m,
+			dhcpv4.WithMessageType(replyType),
+			dhcpv4.WithServerIP(serverIP),
+			dhcpv4.WithRouter(serverIP),
+			dhcpv4.WithNetmask(mask),
+			dhcpv4.WithYourIP(replyIp),
+			// RFC 2131, Section 4.3.1. Server Identifier: MUST
+			dhcpv4.WithOption(dhcpv4.OptServerIdentifier(serverIP)),
+			// RFC 2131, Section 4.3.1. IP lease time: MUST
+			dhcpv4.WithOption(dhcpv4.OptIPAddressLeaseTime(leaseTime)),
+			dhcpv4.WithRouter(serverIP),
+			dhcpv4.WithDNS(serverIP),
+		)
+
+		if val := m.Options.Get(dhcpv4.OptionClientIdentifier); len(val) > 0 {
+			reply.UpdateOption(dhcpv4.OptGeneric(dhcpv4.OptionClientIdentifier, val))
+		}
+
+		if _, err := conn.WriteTo(reply.ToBytes(), peer); err != nil {
+			log.F("[dpcpd] could not write %v: %s", reply, err)
+			return
+		}
+
+		log.F("[dpcpd] lease %v to client %v", replyIp, reply.ClientHWAddr)
+	}
+}
+
+func detectServer(iface string) (exists bool) {
+	client, err := nclient4.New(iface)
+	if err != nil {
+		log.F("[dhcpd] failed in dhcp client creation: %s", err)
+		return
+	}
+	defer client.Close()
+
+	ctx, _ := context.WithTimeout(context.Background(), 3*time.Second)
+	_, err = client.Request(ctx)
+	if err != nil {
+		return
+	}
+
+	return true
+}
+
+func ifaceIPMask4(iface string) (net.IP, net.IPMask) {
+	intf, err := net.InterfaceByName(iface)
+	if err != nil {
+		return nil, nil
+	}
+
+	addrs, err := intf.Addrs()
+	if err != nil {
+		return nil, nil
+	}
+
+	for _, addr := range addrs {
+		var ip net.IP
+		var mask net.IPMask
+
+		switch v := addr.(type) {
+		case *net.IPNet:
+			ip = v.IP
+			mask = v.Mask
+		case *net.IPAddr:
+			ip = v.IP
+			mask = ip.DefaultMask()
+		}
+
+		if ip4 := ip.To4(); ip4 != nil {
+			return ip4, mask
+		}
+	}
+
+	return nil, nil
+}

service/dhcpd/pool.go

@@ -0,0 +1,67 @@
+package dhcpd
+
+import (
+	"bytes"
+	"errors"
+	"net"
+	"time"
+)
+
+type Pool struct {
+	lease time.Duration
+	items []*item
+}
+
+func NewPool(lease time.Duration, ipStart, ipEnd net.IP) (*Pool, error) {
+	items := make([]*item, 0)
+	var currentIp = ipStart.To4()
+	for bytes.Compare(currentIp, ipEnd.To4()) <= 0 {
+		ip := make([]byte, 4)
+		copy(ip, currentIp)
+		i := &item{
+			lease: lease,
+			ip:    ip,
+		}
+		items = append(items, i)
+		currentIp[3]++
+	}
+	return &Pool{lease: lease, items: items}, nil
+}
+
+func (p *Pool) AssignIP(mac net.HardwareAddr) (net.IP, error) {
+	var ip net.IP
+	for _, item := range p.items {
+		if mac.String() == item.hardwareAddr.String() {
+			return item.ip, nil
+		}
+	}
+	for _, item := range p.items {
+		if ip = item.take(mac); ip != nil {
+			return ip, nil
+		}
+	}
+	return nil, errors.New("no more ip can be assigned")
+}
+
+type item struct {
+	ip           net.IP
+	lease        time.Duration
+	taken        bool
+	hardwareAddr net.HardwareAddr
+}
+
+func (i *item) take(addr net.HardwareAddr) net.IP {
+	if i.taken {
+		return nil
+	} else {
+		i.taken = true
+		go func() {
+			timer := time.NewTimer(i.lease)
+			<-timer.C
+			i.hardwareAddr = nil
+			i.taken = false
+		}()
+		i.hardwareAddr = addr
+		return i.ip
+	}
+}

systemd/glider@.service

@@ -14,8 +14,9 @@ ExecStart=/usr/bin/glider -config /etc/glider/%i.conf
 # work with systemd v229 or later, so glider can listen on port below 1024 with none-root user
 # CAP_NET_ADMIN: ipset
 # CAP_NET_BIND_SERVICE: bind ports under 1024
-CapabilityBoundingSet=CAP_NET_ADMIN CAP_NET_BIND_SERVICE
-AmbientCapabilities=CAP_NET_ADMIN CAP_NET_BIND_SERVICE
+# CAP_NET_RAW: bind raw socket and broadcasting (used by dhcpd)
+CapabilityBoundingSet=CAP_NET_ADMIN CAP_NET_BIND_SERVICE CAP_NET_RAW
+AmbientCapabilities=CAP_NET_ADMIN CAP_NET_BIND_SERVICE CAP_NET_RAW
 NoNewPrivileges=true
 
 [Install]