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dhcpcd.go
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dhcpcd.go
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// Copyright © 2018-2020 Platina Systems, Inc. All rights reserved.
// Use of this source code is governed by the GPL-2 license described in the
// LICENSE file.
// Package dhcpcd is a simple dhcp client
package dhcpcd
import (
"encoding/binary"
"errors"
"fmt"
"io/ioutil"
"math/bits"
"net"
"os"
"strconv"
"syscall"
"time"
"unsafe"
"github.com/d2g/dhcp4"
"github.com/d2g/dhcp4client"
"github.com/jpillora/backoff"
"github.com/platinasystems/goes"
"github.com/platinasystems/goes/cmd"
"github.com/platinasystems/goes/external/parms"
"github.com/platinasystems/goes/lang"
)
type Command struct {
g *goes.Goes
myIP string
rtrIP string
dnsIP string
lt uint32
ack dhcp4.Packet
cl *dhcp4client.Client
i string
}
func (*Command) String() string { return "dhcpcd" }
func (*Command) Usage() string { return "dhcpcd" }
func (*Command) Apropos() lang.Alt {
return lang.Alt{
lang.EnUS: "dhcp client daemon",
}
}
func (c *Command) Goes(g *goes.Goes) { c.g = g }
func (*Command) Kind() cmd.Kind { return cmd.Daemon }
const IFNAMSIZ = 16
type ifreq struct {
ifrName [IFNAMSIZ]byte
ifrNewname [IFNAMSIZ]byte
}
func (c *Command) parseACK(ack dhcp4.Packet) (err error) {
c.myIP = ack.YIAddr().String()
opt := ack.ParseOptions()
nm := opt[1]
fmt.Printf("Option[1] netmask: %v\n", nm)
if len(nm) == 4 {
c.myIP = c.myIP + "/" + strconv.Itoa(bits.LeadingZeros32(^binary.BigEndian.Uint32(nm)))
}
fmt.Printf("Got address %s\n", c.myIP)
rtr := opt[3]
c.rtrIP = ""
fmt.Printf("Option[3] router: %v\n", rtr)
if len(rtr) == 4 {
ip := net.IP(rtr)
if !ip.Equal(net.IPv4(0, 0, 0, 0)) {
c.rtrIP = ip.String()
}
}
ltOpt := opt[51]
fmt.Printf("Got lease %v\n", ltOpt)
c.lt = uint32(86400)
if len(ltOpt) == 4 {
c.lt = binary.BigEndian.Uint32(ltOpt)
fmt.Printf("Lease time %d\n", c.lt)
}
dns := opt[6]
fmt.Printf("Got DNS %v\n", dns)
c.dnsIP = ""
for i := 0; i < len(dns) && len(dns[i:]) >= 4; i += 4 {
c.dnsIP = c.dnsIP + "nameserver " + net.IP(dns[i:i+4]).String() + "\n"
}
fmt.Printf("DNS resolved to %v\n", c.dnsIP)
return
}
func (c *Command) updateParm(myIP string, myLastIP string, rtrIP string,
rtrLastIP string, dnsIP string, dnsLastIP string) (err error) {
if myIP != myLastIP {
if myIP != "" {
err = c.g.Main("ip", "address", "add", myIP, "dev", c.i)
if err != nil {
return err
}
}
if myLastIP != "" {
err = c.g.Main("ip", "address", "delete", myLastIP, "dev", c.i)
if err != nil {
return err
}
}
}
if rtrIP != rtrLastIP {
if rtrIP != "" {
err := c.g.Main("ip", "route", "add", "0.0.0.0/0", "via", rtrIP)
if err != nil {
return err
}
}
if rtrLastIP != "" {
err := c.g.Main("ip", "route", "delete", "0.0.0.0/0", "via", rtrLastIP)
if err != nil {
return err
}
}
}
if dnsIP != dnsLastIP {
if dnsIP != "" {
err := ioutil.WriteFile("/etc/resolv.conf", []byte(dnsIP), 0644)
if err != nil {
return err
}
}
}
return nil
}
func (c *Command) Main(args ...string) error {
parm, args := parms.New(args, "-i")
c.i = "eth0"
if parm.ByName["-i"] != "" {
c.i = parm.ByName["-i"]
}
if len(c.i) > (IFNAMSIZ)-1 {
return errors.New("Interface name too long")
}
var dev ifreq
copy(dev.ifrName[:], c.i)
s, err := syscall.Socket(syscall.AF_UNIX, syscall.SOCK_DGRAM, 0)
if err != nil {
return err
}
defer syscall.Close(s)
_, _, e := syscall.Syscall(syscall.SYS_IOCTL, uintptr(s),
uintptr(syscall.SIOCGIFHWADDR), uintptr(unsafe.Pointer(&dev)))
if e != 0 {
return e
}
mac := net.HardwareAddr(dev.ifrNewname[2:8])
fmt.Printf("Got %s\n", mac)
err = c.g.Main("ip", "link", "change", c.i, "up")
if err != nil {
return err
}
defer func() {
_ = c.g.Main("ip", "link", "change", c.i, "down")
}()
err = c.g.Main("ip", "route", "add", "255.255.255.255/32", "dev", c.i)
if err != nil {
return err
}
defer func() {
_ = c.g.Main("ip", "route", "delete", "255.255.255.255/32", "dev", c.i)
}()
sock, err := dhcp4client.NewInetSock(dhcp4client.SetLocalAddr(net.UDPAddr{IP: net.IPv4(0, 0, 0, 0), Port: 68}), dhcp4client.SetRemoteAddr(net.UDPAddr{IP: net.IPv4bcast, Port: 67}))
if err != nil {
return err
}
defer sock.Close()
c.cl, err = dhcp4client.New(dhcp4client.HardwareAddr(mac), dhcp4client.Connection(sock))
if err != nil {
return err
}
defer c.cl.Close()
defer func() {
if c.ack != nil && c.myIP != "" {
err := c.cl.Release(c.ack)
if err != nil {
fmt.Fprintf(os.Stderr, "Error in release: %s\n", err)
}
}
c.updateParm("", c.myIP, "", c.rtrIP, "", c.dnsIP)
c.myIP = ""
c.rtrIP = ""
c.dnsIP = ""
}()
b := &backoff.Backoff{
Min: 1 * time.Second,
Max: 60 * time.Second,
Factor: 2,
Jitter: false,
}
for {
myLastIP := c.myIP
rtrLastIP := c.rtrIP
dnsLastIP := c.dnsIP
success := false
done := make(chan struct{}, 1)
goes.WG.Add(1)
go func() {
defer goes.WG.Done()
success, c.ack, err = c.cl.Request()
close(done)
}()
select {
case <-goes.Stop:
return nil
case <-done:
}
if err == nil {
if success {
err := c.parseACK(c.ack)
if err == nil {
if c.myIP != "" {
err := c.updateParm(c.myIP, myLastIP, c.rtrIP, rtrLastIP,
c.dnsIP, dnsLastIP)
if err == nil {
exit, err := c.renew()
if exit {
return nil
}
fmt.Fprintf(os.Stderr, "Error in renew: %s\n", err)
} else {
fmt.Fprintf(os.Stderr, "Error in updateParm: %s\n", err)
}
}
} else {
fmt.Fprintf(os.Stderr, "Error in parseACK: %s\n", err)
}
}
} else {
fmt.Fprintf(os.Stderr, "Error in Request: %s\n", err)
}
if !func() bool {
t := time.NewTicker(b.Duration())
defer t.Stop()
select {
case <-goes.Stop:
return false
case <-t.C:
return true
}
}() {
return nil
}
}
}
func (c *Command) renew() (done bool, err error) {
timeout := time.Now().Add(time.Duration(c.lt) * time.Second)
sleepTime := c.lt / 2
for time.Now().Before(timeout) {
if !func() bool {
t := time.NewTicker(time.Duration(sleepTime) * time.Second)
defer t.Stop()
select {
case <-goes.Stop:
return false
case <-t.C:
return true
}
}() {
return true, nil
}
sleepTime = sleepTime / 2
if sleepTime < 1 {
sleepTime = 1
}
myLastIP := c.myIP
rtrLastIP := c.rtrIP
dnsLastIP := c.dnsIP
success := false
done := make(chan struct{}, 1)
goes.WG.Add(1)
go func() {
defer goes.WG.Done()
success, c.ack, err = c.cl.Request()
close(done)
}()
select {
case <-goes.Stop:
return true, nil
case <-done:
}
if err == nil {
if success {
err := c.parseACK(c.ack)
if err == nil {
if c.myIP == "" {
return false,
fmt.Errorf("Renew did not contain IP address")
}
err = c.updateParm(c.myIP, myLastIP, c.rtrIP, rtrLastIP, c.dnsIP, dnsLastIP)
if err == nil {
timeout = time.Now().Add(time.Duration(c.lt) * time.Second)
sleepTime = c.lt / 2
continue
} else {
return false,
fmt.Errorf("Error in updateParm: %w", err)
}
} else {
return false,
fmt.Errorf("Error in parseACK: %w", err)
}
}
} else {
return false, fmt.Errorf("Error in Renew: %w", err)
}
}
return false, fmt.Errorf("Lease expired without renew")
}