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working on adding lease handouts

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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
)

28
dhcp/packet.go
View File

@@ -44,16 +44,21 @@ type BootRequest struct {
NextIP net.IP
RelayIP net.IP
DHCPType uint8 // option 53
HostName string // option 12
ParameterRequests []string
DHCPType DHCPMessageType // option 53
HostName string // option 12
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
}