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working on adding lease handouts

This commit is contained in:
Kyle Isom 2023-05-06 05:21:27 +00:00
parent c475287fb1
commit a53d392ed8
15 changed files with 477 additions and 76 deletions
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1
dhcp/BUILD.bazel
View File

@ -5,6 +5,7 @@ go_library(
srcs = [
"options.go",
"packet.go",
"read_options.go",
],
importpath = "git.wntrmute.dev/kyle/kdhcp/dhcp",
visibility = ["//visibility:public"],

85
dhcp/options.go
View File

@ -1,57 +1,72 @@
package dhcp
import (
"errors"
"fmt"
"io"
)
type OptionTag uint8
func (opt OptionTag) String() string {
s, ok := optionStrings[opt]
if !ok {
panic(fmt.Sprintf("no string for option %d", opt))
}
return s
}
type Option func(req *BootRequest, r io.Reader) error
const (
OptionTagPadding OptionTag = 0
OptionTagSubnetMask OptionTag = 1
OptionTagTimeOffset OptionTag = 2
OptionTagRouter OptionTag = 3
OptionTagDomainNameServer OptionTag = 6
OptionTagHostName OptionTag = 12
OptionTagDomainName OptionTag = 15
OptionTagInterfaceMTU OptionTag = 26
OptionTagBroadcastAddress OptionTag = 28
OptionTagNTPServers OptionTag = 42
OptionTagNBNS OptionTag = 44
OptionTagNBScope OptionTag = 47
OptionTagMessageType OptionTag = 53
OptionTagParameterRequestList OptionTag = 55
OptionTagDomainSearch OptionTag = 119
OptionTagClasslessStaticRoute OptionTag = 121
OptionTagEnd OptionTag = 255
)
var optionRegistry = map[OptionTag]Option{
OptionTagPadding: OptionPad,
OptionTagHostName: OptionHostName,
OptionTagMessageType: OptionMessageType,
OptionTagParameterRequestList: OptionParameterRequestList,
OptionTagEnd: OptionEnd,
var optionStrings = map[OptionTag]string{
OptionTagPadding: "pad",
OptionTagSubnetMask: "subnet mask",
OptionTagTimeOffset: "time offset from UTC",
OptionTagRouter: "routers",
OptionTagDomainNameServer: "domain name servers",
OptionTagHostName: "host name",
OptionTagDomainName: "domain name",
OptionTagInterfaceMTU: "interface MTU",
OptionTagBroadcastAddress: "broadcast address",
OptionTagNTPServers: "NTP servers",
OptionTagNBNS: "NetBIOS name servers",
OptionTagNBScope: "NetBIOS scope",
OptionTagMessageType: "message type",
OptionTagParameterRequestList: "parameter request list",
OptionTagDomainSearch: "search domain",
OptionTagClasslessStaticRoute: "classless static route",
OptionTagEnd: "end",
}
func OptionPad(req *BootRequest, r io.Reader) error {
return nil
}
type DHCPMessageType uint8
func OptionHostName(req *BootRequest, r io.Reader) error {
return errors.New("dhcp: option not implemented yet")
}
func OptionMessageType(req *BootRequest, r io.Reader) error {
return errors.New("dhcp: option not implemented yet")
}
func OptionParameterRequestList(req *BootRequest, r io.Reader) error {
return errors.New("dhcp: option not implemented yet")
}
func OptionEnd(req *BootRequest, r io.Reader) error {
return errors.New("dhcp: option not implemented yet")
}
func ReadOption(req *BootRequest, tag byte, r io.Reader) error {
opt := OptionTag(tag)
if f, ok := optionRegistry[opt]; ok {
return f(req, r)
}
return fmt.Errorf("dhcp: unknown/unhandled option %d", opt)
}
const (
DHCPMessageTypeDiscover DHCPMessageType = 1
DHCPMessageTypeOffer DHCPMessageType = 2
DHCPMessageTypeRequest DHCPMessageType = 3
DHCPMessageTypeDecline DHCPMessageType = 4
DHCPMessageTypeAck DHCPMessageType = 5
DHCPMessageTypeNAK DHCPMessageType = 6
DHCPMessageTypeRelease DHCPMessageType = 7
DHCPMessageTypeInform DHCPMessageType = 8
)

26
dhcp/packet.go
View File

@ -44,16 +44,21 @@ type BootRequest struct {
NextIP net.IP
RelayIP net.IP
DHCPType uint8 // option 53
DHCPType DHCPMessageType // option 53
HostName string // option 12
ParameterRequests []string
ParameterRequests []OptionTag
endOptions bool
}
func newPacketReaderFunc(r io.Reader) func(v any) error {
return func(v any) error {
return binary.Read(r, binary.BigEndian, v)
}
}
func (req *BootRequest) Read(packet []byte) error {
buf := bytes.NewBuffer(packet)
read := func(v any) error {
return binary.Read(buf, binary.BigEndian, v)
}
read := newPacketReaderFunc(buf)
if err := read(&req.MessageType); err != nil {
return err
@ -113,7 +118,6 @@ func (req *BootRequest) Read(packet []byte) error {
if _, err := buf.Read(hwaPad); err != nil {
return err
}
log.Debugf("padding: %x", hwaPad)
tempBuf := make([]byte, maxServerName)
if _, err := buf.Read(tempBuf); err != nil {
@ -127,7 +131,15 @@ func (req *BootRequest) Read(packet []byte) error {
}
req.FileName = string(bytes.Trim(tempBuf, "\x00"))
if err := ReadMagicCookie(buf); err != nil {
return err
}
for {
if req.endOptions {
break
}
tag, err := buf.ReadByte()
if err != nil {
if err == io.EOF {
@ -138,6 +150,8 @@ func (req *BootRequest) Read(packet []byte) error {
err = ReadOption(req, tag, buf)
if err != nil {
log.Spew(*req)
log.Spew(packet)
return err
}
}

133
dhcp/read_options.go Normal file
View File

@ -0,0 +1,133 @@
package dhcp
import (
"bytes"
"errors"
"fmt"
"io"
log "git.wntrmute.dev/kyle/goutils/syslog"
)
var optionRegistry = map[OptionTag]Option{
OptionTagPadding: OptionPad,
OptionTagHostName: OptionHostName,
OptionTagMessageType: OptionMessageType,
OptionTagParameterRequestList: OptionParameterRequestList,
OptionTagEnd: OptionEnd,
}
func OptionPad(req *BootRequest, r io.Reader) error {
// The padding option is a single 0 byte octet.
return nil
}
// OptionHostName reads a DHCP host name option.
//
// 3.14. Host Name Option
//
// This option specifies the name of the client. The name may or may
// not be qualified with the local domain name (see section 3.17 for the
// preferred way to retrieve the domain name). See RFC 1035 for
// character set restrictions.
// The code for this option is 12, and its minimum length is 1.
func OptionHostName(req *BootRequest, r io.Reader) error {
read := newPacketReaderFunc(r)
var length uint8
if err := read(&length); err != nil {
return fmt.Errorf("dhcp: reading option length for DHCP Message Type")
} else if length == 0 {
return errors.New("dhcp: read option length 0, but expected option length for DHCP Host Name is >= 1")
}
hostName := make([]byte, int(length))
if n, err := r.Read(hostName); err != nil {
return fmt.Errorf("dhcp: while reading hostname: %w", err)
} else if n != int(length) {
return fmt.Errorf("dhcp: only read %d bytes of hostname, expected %d bytes", n, length)
}
req.HostName = string(hostName)
return nil
}
func OptionMessageType(req *BootRequest, r io.Reader) error {
read := newPacketReaderFunc(r)
var length uint8
if err := read(&length); err != nil {
return fmt.Errorf("dhcp: reading option length for DHCP Message Type")
} else if length != 1 {
return fmt.Errorf("dhcp: read option length %d, but expected option length for DHCP Message Type is 1", length)
}
if err := read(&req.DHCPType); err != nil {
return err
}
return nil
}
func OptionParameterRequestList(req *BootRequest, r io.Reader) error {
read := newPacketReaderFunc(r)
var length uint8
if err := read(&length); err != nil {
return fmt.Errorf("dhcp: reading option length for DHCP Message Type")
} else if length == 0 {
return fmt.Errorf("dhcp: read option length %d, but expected option length for DHCP Parameter Request is >= 1", length)
}
var parameters = make([]byte, int(length))
if n, err := r.Read(parameters); err != nil {
return fmt.Errorf("dhcp: while reading parameters: %w", err)
} else if n != int(length) {
return fmt.Errorf("dhcp: only read %d octets of requested parameters, expected %d octets", n, length)
}
for _, parameter := range parameters {
opt := OptionTag(parameter)
log.Debugf("client is requesting %s", opt)
req.ParameterRequests = append(req.ParameterRequests, opt)
}
return nil
}
func OptionEnd(req *BootRequest, r io.Reader) error {
req.endOptions = true
return nil
}
func ReadOption(req *BootRequest, tag byte, r io.Reader) error {
opt := OptionTag(tag)
if f, ok := optionRegistry[opt]; ok {
log.Debugf("dhcp: reading option=%s", opt)
return f(req, r)
}
return fmt.Errorf("dhcp: unknown/unhandled option %d", opt)
}
const magicCookieLength = 4
var magicCookie = []byte{99, 130, 83, 99}
func ReadMagicCookie(r io.Reader) error {
var cookie = make([]byte, magicCookieLength)
n, err := r.Read(cookie)
if err != nil {
return fmt.Errorf("dhcp: failed to read magic cookie: %w", err)
} else if n != magicCookieLength {
return fmt.Errorf("dhcp: read %d bytes, expected to read %d bytes for the magic cookie",
n, magicCookieLength)
}
if !bytes.Equal(cookie, magicCookie) {
return fmt.Errorf("dhcp: read magic cookie %x, expected %x", cookie, magicCookie)
}
return nil
}

8
iptools/lease_info.go
View File

@ -15,7 +15,7 @@ type LeaseInfo struct {
Expires time.Time `yaml:"expires"`
}
type sortableLease []LeaseInfo
type sortableLease []*LeaseInfo
func (a sortableLease) Len() int { return len(a) }
func (a sortableLease) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
@ -33,14 +33,14 @@ func (li *LeaseInfo) Expire() {
li.Expires = time.Time{}
}
func SortLeases(leases []LeaseInfo) []LeaseInfo {
func SortLeases(leases []*LeaseInfo) []*LeaseInfo {
sortable := sortableLease(leases)
sort.Sort(sortable)
return []LeaseInfo(sortable)
return []*LeaseInfo(sortable)
}
func (lease LeaseInfo) Reset() LeaseInfo {
func (lease *LeaseInfo) Reset() *LeaseInfo {
lease.Expires = time.Time{}
lease.HardwareAddress = nil
return lease

101
iptools/pool.go
View File

@ -1,58 +1,141 @@
package iptools
import (
"fmt"
"net/netip"
"sync"
"time"
"git.wntrmute.dev/kyle/goutils/assert"
)
const DefaultExpiry = 168 * time.Hour
type Pool struct {
Name string `yaml:"name"`
Range *Range `yaml:"range"`
Expiry time.Duration `yaml:"expiry"`
Available []LeaseInfo `yaml:"available"`
Active map[netip.Addr]LeaseInfo `yaml:"active"`
Limbo map[netip.Addr]LeaseInfo `yaml:"limbo"` // leases that are currently being offered
Available []*LeaseInfo `yaml:"available"`
Active map[netip.Addr]*LeaseInfo `yaml:"active"`
Limbo map[netip.Addr]*LeaseInfo `yaml:"limbo"` // leases that are currently being offered
NoHostName bool `yaml:"no_hostname"` // don't set the hostname
mtx *sync.Mutex
}
func (p *Pool) lock() {
if p.lock == nil {
p.mtx = &sync.Mutex{}
}
p.mtx.Lock()
}
func (p *Pool) unlock() {
if p.mtx == nil {
panic("pool: attempted to unlock uninitialized mutex")
}
p.mtx.Unlock()
}
func NewPool(name string, r *Range) (*Pool, error) {
if r.Expiry == 0 {
r.Expiry = DefaultExpiry
}
func NewPool(name string, exp time.Duration, r *Range) (*Pool, error) {
p := &Pool{
Name: name,
Expiry: exp,
Expiry: r.Expiry,
NoHostName: r.NoHostName,
Available: enumerateRange(name, r, true),
}
return p, nil
}
func (p *Pool) Sort() {
func (p *Pool) sort() {
p.Available = SortLeases(p.Available)
}
func (p *Pool) Sort() {
p.lock()
defer p.unlock()
p.sort()
}
func (p *Pool) IsAddressAvailable() bool {
return len(p.Available) > 0
}
func (p *Pool) Peek(t time.Time, waitFor time.Duration) netip.Addr {
// Peek returns the first available address from the pool and moves it
// from available to limbo. When the client is given the address, Accept
// should be called on the address to move it from limbo to active.
func (p *Pool) Peek(t time.Time, waitFor time.Duration) *LeaseInfo {
p.lock()
defer p.unlock()
li := p.peek(t, waitFor)
return li
}
func (p *Pool) peek(t time.Time, waitFor time.Duration) *LeaseInfo {
if len(p.Available) == 0 {
return nil
}
lease := p.Available[0]
p.Available = p.Available[1:]
lease.ResetExpiry(t, waitFor)
p.Limbo[lease.Addr] = lease
return lease.Addr
return lease
}
func (p *Pool) accept(addr netip.Addr) error {
assert.Bool(p.Active[addr] == nil, fmt.Sprintf("limbo address %s is already active: %#v", addr, *p.Active[addr]))
p.Active[addr] = p.Limbo[addr]
delete(p.Limbo, addr)
return nil
}
// Accept will move an address out limbo and mark it as active.
func (p *Pool) Accept(addr netip.Addr, t time.Time) error {
p.lock()
defer p.unlock()
p.update(t)
p.accept(addr)
return nil
}
// Update checks expirations on leases, moving any expired leases back
// to the available pool and removing any limbo leases that are expired.
func (p *Pool) Update(t time.Time) {
p.lock()
defer p.unlock()
p.update(t)
}
func (p *Pool) update(t time.Time) {
evictedHosts := []netip.Addr{}
for k, v := range p.Active {
if v.IsExpired(t) {
delete(p.Active, k)
evictedHosts = append(evictedHosts, k)
v = v.Reset()
p.Available = append(p.Available, v)
}
}
for _, ip := range evictedHosts {
delete(p.Active, ip)
}
for k, v := range p.Limbo {
if v.IsExpired(t) {
delete(p.Limbo, k)

3
iptools/pool_test.go
View File

@ -4,7 +4,6 @@ import (
"fmt"
"net/netip"
"testing"
"time"
)
var (
@ -18,7 +17,7 @@ func TestBasicPool(t *testing.T) {
End: poolTestIP2,
}
p, err := NewPool("cluster", 24*time.Hour, r)
p, err := NewPool("cluster", r)
if err != nil {
t.Fatal(err)
}

5
iptools/range.go
View File

@ -3,6 +3,7 @@ package iptools
import (
"fmt"
"net/netip"
"time"
)
const (
@ -13,6 +14,8 @@ type Range struct {
Start netip.Addr `yaml:"start"`
End netip.Addr `yaml:"end"`
Network netip.Prefix `yaml:"network"`
Expiry time.Duration `yaml:"expiry"`
NoHostName bool `yaml:"no_hostname"` // don't set the hostname
}
func (r *Range) Validate() error {
@ -54,7 +57,7 @@ func (r *Range) numHosts() int {
hosts := 0
for cur.Compare(r.End) < 1 {
hosts++
cur.Next()
cur = cur.Next()
}
return hosts

13
iptools/range_test.go
View File

@ -47,3 +47,16 @@ func TestBasicValidation(t *testing.T) {
t.Fatal("range 4 should be invalid")
}
}
func TestNumHosts(t *testing.T) {
r := &Range{
Start: rangeTestIP1,
End: rangeTestIP2,
}
expected := 15
numHosts := r.numHosts()
if numHosts != expected {
t.Fatalf("have %d hosts, expected %d", numHosts, expected)
}
}

13
iptools/tools.go
View File

@ -1,8 +1,10 @@
package iptools
import "fmt"
import (
"fmt"
)
func enumerateRange(name string, r *Range, startFromOne bool) []LeaseInfo {
func enumerateRange(name string, r *Range, startFromOne bool) []*LeaseInfo {
start := r.Start
cur := start
lenfmt := fmt.Sprintf("%%s%%0%dd", len(fmt.Sprintf("%d", r.numHosts())))
@ -10,11 +12,12 @@ func enumerateRange(name string, r *Range, startFromOne bool) []LeaseInfo {
if startFromOne {
i++
}
leases := []LeaseInfo{}
leases := []*LeaseInfo{}
for r.End.Compare(cur) >= 0 {
leases = append(leases, LeaseInfo{
HostName: fmt.Sprintf(lenfmt, name, i),
hostName := fmt.Sprintf(lenfmt, name, i)
leases = append(leases, &LeaseInfo{
HostName: hostName,
Addr: cur,
})
i++

3
kdhcpd.yaml
View File

@ -1,7 +1,7 @@
kdhcp:
version: 1
lease_file: /tmp/kdhcp_lease.yaml
interface: deveth0
interface: enp89s0
port: 67
network:
address: 192.168.4.250
@ -22,6 +22,7 @@ kdhcp:
default:
start: 192.168.4.128
end: 192.168.4.164
no_hostname: True
statics:
controller: 192.168.4.254
haven: 192.168.4.253

4
server/BUILD.bazel
View File

@ -5,6 +5,8 @@ go_library(
srcs = [
"ifi.go",
"ifi_linux.go",
"lease_state.go",
"pools.go",
"server.go",
],
importpath = "git.wntrmute.dev/kyle/kdhcp/server",
@ -12,6 +14,8 @@ go_library(
deps = [
"//config",
"//dhcp",
"//iptools",
"@dev_wntrmute_git_kyle_goutils//syslog",
"@in_gopkg_yaml_v2//:yaml_v2",
],
)

62
server/lease_state.go Normal file
View File

@ -0,0 +1,62 @@
package server
import (
"fmt"
"os"
log "git.wntrmute.dev/kyle/goutils/syslog"
"git.wntrmute.dev/kyle/kdhcp/iptools"
"gopkg.in/yaml.v2"
)
type LeaseState struct {
Pools map[string]*iptools.Pool `yaml:"pools"`
Static map[string]*iptools.LeaseInfo `yaml:"static"`
}
func (srv *Server) SaveLeases() error {
leaseFile, err := os.Create(srv.Config.LeaseFile)
if err != nil {
return fmt.Errorf("server: while saving leases: %w", err)
}
defer leaseFile.Close()
encoder := yaml.NewEncoder(leaseFile)
state := &LeaseState{
Pools: srv.Pools,
Static: srv.Static,
}
if err = encoder.Encode(state); err != nil {
return fmt.Errorf("server: while saving leases: %w", err)
}
if err = encoder.Close(); err != nil {
return fmt.Errorf("server: while saving leases: %w", err)
}
return nil
}
func (srv *Server) LoadLeases() error {
leaseState := &LeaseState{}
leaseFile, err := os.Open(srv.Config.LeaseFile)
if err != nil {
if os.IsNotExist(err) {
log.Warningf("server: not loading leases from %s: lease file not found", srv.Config.LeaseFile)
return nil
}
return fmt.Errorf("server: while reading leases: %w", err)
}
defer leaseFile.Close()
decoder := yaml.NewDecoder(leaseFile)
if err = decoder.Decode(leaseState); err != nil {
return fmt.Errorf("server: while reading leases: %w", err)
}
srv.Pools = leaseState.Pools
srv.Static = leaseState.Static
return nil
}

37
server/pools.go Normal file
View File

@ -0,0 +1,37 @@
package server
import (
"fmt"
"net/netip"
log "git.wntrmute.dev/kyle/goutils/syslog"
"git.wntrmute.dev/kyle/kdhcp/iptools"
)
// pools.go adds pool functionality to the server.
func (srv *Server) loadPoolsFromConfig() error {
for host, ip := range srv.Config.Statics {
addr, ok := netip.AddrFromSlice(ip.To4())
if !ok {
return fmt.Errorf("server: while instantiating pools, could not load IP %s", ip)
}
log.Debugf("server: added static host entry %s -> %s", host, addr)
srv.Static[host] = &iptools.LeaseInfo{
HostName: host,
Addr: addr,
}
}
for name, ipRange := range srv.Config.Pools {
pool, err := iptools.NewPool(name, ipRange)
if err != nil {
return fmt.Errorf("server: couldn't load pool %s: %w", name, err)
}
log.Debugf("server: added pool %s: %s -> %s", name, ipRange.Start, ipRange.End)
srv.Pools[name] = pool
}
return nil
}

39
server/server.go
View File

@ -3,19 +3,25 @@ package server
import (
"errors"
"net"
"time"
log "git.wntrmute.dev/kyle/goutils/syslog"
"git.wntrmute.dev/kyle/kdhcp/config"
"git.wntrmute.dev/kyle/kdhcp/dhcp"
"git.wntrmute.dev/kyle/kdhcp/iptools"
)
const (
DefaultPool = "default"
MaxPacketSize = 512
MaxResponseWait = 5 * time.Minute
)
type Server struct {
Conn net.PacketConn
Config *config.Config
Pools map[string]*iptools.Pool
Static map[string]*iptools.LeaseInfo
}
func (s *Server) Close() error {
@ -24,6 +30,8 @@ func (s *Server) Close() error {
func (s *Server) Bind() (err error) {
// In order to read DHCP packets, we'll need to listen on all addresses.
// That being said, we also want to limit our listening to the DHCP
// network device.
ip := net.IP([]byte{0, 0, 0, 0})
s.Conn, err = BindInterface(ip, s.Config.Port, s.Config.Interface)
return err
@ -46,7 +54,7 @@ func (s *Server) ReadDHCPRequest() (*dhcp.BootRequest, error) {
return nil, err
}
log.Debugf("server: read %db packet from %s", len(pkt), addr)
log.Debugf("server: read packet from %s", addr)
return dhcp.ReadRequest(pkt)
}
@ -77,10 +85,19 @@ func (s *Server) Listen() {
func New(cfg *config.Config) (*Server, error) {
srv := &Server{
Config: cfg,
Pools: map[string]*iptools.Pool{},
Static: map[string]*iptools.LeaseInfo{},
}
err := srv.Bind()
if err != nil {
if err := srv.loadPoolsFromConfig(); err != nil {
return nil, err
}
if err := srv.LoadLeases(); err != nil {
return nil, err
}
if err := srv.Bind(); err != nil {
return nil, err
}
@ -88,3 +105,19 @@ func New(cfg *config.Config) (*Server, error) {
return srv, nil
}
func (srv *Server) SelectLease(req *dhcp.BootRequest, t time.Time) *iptools.LeaseInfo {
if li, ok := srv.Static[req.HostName]; ok {
return li
}
if pool, ok := srv.Pools[req.HostName]; ok {
return pool.Peek(t, MaxResponseWait)
}
if pool, ok := srv.Pools[DefaultPool]; ok {
return pool.Peek(t, MaxResponseWait)
}
return nil
}