dhcpd: added dhcpd-failover service, only keep linux support

README.md

@@ -38,7 +38,7 @@ we can set up local listeners as proxy servers, and forward requests to internet
 - Periodical availability checking for forwarders
 - Send requests from specific local ip/interface
 - Services: 
-  - dhcpd: a simple dhcp server that can detect existing dhcp server and avoid conflicts
+  - dhcpd: a simple dhcp server that can run in failover mode
 
 ## Protocols
 
@@ -84,6 +84,8 @@ we can set up local listeners as proxy servers, and forward requests to internet
 
 ## Usage
 
+#### Run
+
 ```bash
 glider -config CONFIG_PATH
 ```
@@ -94,7 +96,7 @@ glider -verbose -listen :8443 -forward SCHEME://HOST:PORT
 #### Help
 
 <details>
-<summary>`glider -help` (click to see details)</summary>
+<summary>`glider -help` (click)</summary>
 
 ```bash
 Usage: glider [-listen URL]... [-forward URL]... [OPTION]...
@@ -207,6 +209,7 @@ Forwarder Options: FORWARD_URL#OPTIONS
 
 Services:
    dhcpd: service=dhcpd,INTERFACE,START_IP,END_IP,LEASE_MINUTES[,MAC=IP,MAC=IP...]
+          service=dhcpd-failover,INTERFACE,START_IP,END_IP,LEASE_MINUTES[,MAC=IP,MAC=IP...]
      e.g. service=dhcpd,eth1,192.168.1.100,192.168.1.199,720
 
 --
@@ -225,7 +228,7 @@ glider 0.16.0, https://github.com/nadoo/glider
 #### Schemes
 
 <details>
-<summary>`glider -scheme all` (click to see details)</summary>
+<summary>`glider -scheme all` (click)</summary>
 
 ```bash
 KCP scheme:
@@ -340,7 +343,7 @@ TLS and Websocket with a specified proxy protocol:
 #### Examples
 
 <details>
-<summary>`glider -example` (click to see details)</summary>
+<summary>`glider -example` (click)</summary>
 
 ```bash
 Examples:
@@ -391,9 +394,11 @@ Examples:
 
 - dhcpd: 
   - service=dhcpd,INTERFACE,START_IP,END_IP,LEASE_MINUTES[,MAC=IP,MAC=IP...]
-  - e.g.:
+      - service=dhcpd,eth1,192.168.1.100,192.168.1.199,720
-  - service=dhcpd,eth1,192.168.1.100,192.168.1.199,720
+      - service=dhcpd,eth2,192.168.2.100,192.168.2.199,720,fc:23:34:9e:25:01=192.168.2.101
-  - service=dhcpd,eth2,192.168.2.100,192.168.2.199,720,fc:23:34:9e:25:01=192.168.2.101
+
+- dhcpd-failover: only serves requests when there's no other dhcp server exists
+  - service=dhcpd-failover,INTERFACE,START_IP,END_IP,LEASE_MINUTES[,MAC=IP,MAC=IP...]
 
 ## Linux Service
 

config.go

@@ -204,6 +204,7 @@ Forwarder Options: FORWARD_URL#OPTIONS
 
 Services:
    dhcpd: service=dhcpd,INTERFACE,START_IP,END_IP,LEASE_MINUTES[,MAC=IP,MAC=IP...]
+          service=dhcpd-failover,INTERFACE,START_IP,END_IP,LEASE_MINUTES[,MAC=IP,MAC=IP...]
      e.g. service=dhcpd,eth1,192.168.1.100,192.168.1.199,720
 
 --

feature.go

@@ -3,7 +3,6 @@ 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/http"

feature_linux.go

@@ -3,6 +3,7 @@ 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/cilent.go

@@ -3,40 +3,30 @@ package dhcpd
 import (
 	"context"
 	"net"
-	"runtime"
 	"time"
 
 	"github.com/insomniacslk/dhcp/dhcpv4"
 
-	"github.com/nadoo/glider/pkg/log"
 	"github.com/nadoo/glider/pkg/sockopt"
 )
 
-func existsServer(intf *net.Interface) (exists bool) {
+func discovery(intf *net.Interface) (found bool) {
 	lc := &net.ListenConfig{}
 	lc.Control = sockopt.BindControl(intf)
 
-	addr := "0.0.0.0:68"
+	pc, err := lc.ListenPacket(context.Background(), "udp4", "255.255.255.255:68")
-	if runtime.GOOS == "linux" || runtime.GOOS == "android" {
-		addr = "255.255.255.255:68"
-	}
-
-	pc, err := lc.ListenPacket(context.Background(), "udp4", addr)
 	if err != nil {
-		log.F("[dhcpd] failed in dhcp client ListenPacket: %s", err)
 		return
 	}
 	defer pc.Close()
 
 	discovery, err := dhcpv4.NewDiscovery(intf.HardwareAddr, dhcpv4.WithBroadcast(true))
 	if err != nil {
-		log.F("[dhcpd] failed in dhcp client NewDiscovery: %s", err)
 		return
 	}
 
 	_, err = pc.WriteTo(discovery.ToBytes(), &net.UDPAddr{IP: net.IPv4bcast, Port: 67})
 	if err != nil {
-		log.F("[dhcpd] failed in dhcp client WriteTo: %s", err)
 		return
 	}
 

service/dhcpd/dhcpd.go

@@ -1,11 +1,13 @@
 package dhcpd
 
 import (
+	"bytes"
 	"errors"
 	"net"
 	"net/netip"
 	"strconv"
 	"strings"
+	"sync"
 	"time"
 
 	"github.com/insomniacslk/dhcp/dhcpv4"
@@ -18,13 +20,19 @@ import (
 var leaseTime = time.Hour * 12
 
 func init() {
-	service.Register("dhcpd", &dpcpd{})
+	service.Register("dhcpd", &dhcpd{})
+	service.Register("dhcpd-failover", &dhcpd{detect: true})
 }
 
-type dpcpd struct{}
+type dhcpd struct {
+	mu       sync.Mutex
+	detect   bool
+	failover bool
+	intface  *net.Interface
+}
 
 // Run runs the service.
-func (*dpcpd) Run(args ...string) {
+func (d *dhcpd) Run(args ...string) {
 	if len(args) < 4 {
 		log.F("[dhcpd] not enough parameters, exiting")
 		return
@@ -40,10 +48,11 @@ func (*dpcpd) Run(args ...string) {
 		log.F("[dhcpd] get ip of interface '%s' error: %s", iface, err)
 		return
 	}
+	d.intface = intf
 
-	if existsServer(intf) {
+	if d.detect {
-		log.F("[dhcpd] found existing dhcp server on interface %s, service exiting", iface)
+		d.setFailoverMode(discovery(intf))
-		return
+		go d.detectServer(time.Second * 60)
 	}
 
 	startIP, err := netip.ParseAddr(start)
@@ -76,23 +85,23 @@ func (*dpcpd) Run(args ...string) {
 	}
 
 	laddr := net.UDPAddr{IP: net.IPv4(0, 0, 0, 0), Port: 67}
-	server, err := server4.NewServer(iface, &laddr, handleDHCP(ip, mask, pool))
+	server, err := server4.NewServer(iface, &laddr, d.handleDHCP(ip, mask, pool))
 	if err != nil {
 		log.F("[dhcpd] error in server creation: %s", err)
 		return
 	}
 
-	log.F("[dhcpd] Listening on interface %s(%s/%d.%d.%d.%d)",
+	log.F("[dhcpd] Listening on interface %s(%s/%d.%d.%d.%d), server detection: %t",
-		iface, ip, mask[0], mask[1], mask[2], mask[3])
+		iface, ip, mask[0], mask[1], mask[2], mask[3], d.detect)
 
 	server.Serve()
 }
 
-func handleDHCP(serverIP net.IP, mask net.IPMask, pool *Pool) server4.Handler {
+func (d *dhcpd) handleDHCP(serverIP net.IP, mask net.IPMask, pool *Pool) server4.Handler {
 	return func(conn net.PacketConn, peer net.Addr, m *dhcpv4.DHCPv4) {
 
-		var replyType dhcpv4.MessageType
+		var reqType, replyType dhcpv4.MessageType
-		switch mt := m.MessageType(); mt {
+		switch reqType = m.MessageType(); reqType {
 		case dhcpv4.MessageTypeDiscover:
 			replyType = dhcpv4.MessageTypeOffer
 		case dhcpv4.MessageTypeRequest, dhcpv4.MessageTypeInform:
@@ -106,7 +115,11 @@ func handleDHCP(serverIP net.IP, mask net.IPMask, pool *Pool) server4.Handler {
 			log.F("[dpcpd] received decline message from %v", m.ClientHWAddr)
 			return
 		default:
-			log.F("[dpcpd] can't handle type %v", mt)
+			log.F("[dpcpd] can't handle type %v", reqType)
+			return
+		}
+
+		if d.inFailoverMode() || bytes.Equal(d.intface.HardwareAddr, m.ClientHWAddr) {
 			return
 		}
 
@@ -146,6 +159,33 @@ func handleDHCP(serverIP net.IP, mask net.IPMask, pool *Pool) server4.Handler {
 	}
 }
 
+func (d *dhcpd) inFailoverMode() bool {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+	return d.failover
+}
+
+func (d *dhcpd) setFailoverMode(v bool) {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+
+	if d.failover != v {
+		if v {
+			log.F("[dpcpd] existing dhcp server detected, enter failover mode")
+		} else {
+			log.F("[dpcpd] no dhcp server detected, exit failover mode")
+		}
+	}
+	d.failover = v
+}
+
+func (d *dhcpd) detectServer(interval time.Duration) {
+	for {
+		d.setFailoverMode(discovery(d.intface))
+		time.Sleep(interval)
+	}
+}
+
 func ifaceAddr(iface string) (*net.Interface, net.IP, net.IPMask, error) {
 	intf, err := net.InterfaceByName(iface)
 	if err != nil {