README
¶
This package contains helpers to construct simple DHCPv4 clients.
There are currently no stability guarantees around this package. We can revisit this in early 2019, at which point router7 and gokrazy users should have complained in case their DHCP broke :).
Documentation
¶
Overview ¶
Package dhcp4 helps construct and interpret google/gopacket/layers.DHCPv4 messages, as well as reading from and writing to mdlayher/raw.Conns.
Example ¶
package main
import (
"log"
"net"
"syscall"
"time"
"github.com/google/gopacket/layers"
"github.com/mdlayher/packet"
"github.com/rtr7/dhcp4"
)
func main() {
iface, err := net.InterfaceByName("uplink0")
if err != nil {
log.Fatal(err)
}
xidGen := dhcp4.XIDGenerator(iface.HardwareAddr)
conn, err := packet.Listen(iface, packet.Datagram, syscall.ETH_P_IP, nil)
if err != nil {
log.Fatal(err)
}
discover := &layers.DHCPv4{
Operation: layers.DHCPOpRequest,
HardwareType: layers.LinkTypeEthernet,
HardwareLen: uint8(len(layers.EthernetBroadcast)),
Xid: xidGen(),
ClientHWAddr: iface.HardwareAddr,
Options: []layers.DHCPOption{
dhcp4.MessageTypeOpt(layers.DHCPMsgTypeDiscover),
dhcp4.HostnameOpt("dhcpprobe"),
dhcp4.ClientIDOpt(layers.LinkTypeEthernet, iface.HardwareAddr),
},
}
if err := dhcp4.Write(conn, discover); err != nil {
log.Fatal(err)
}
// Display all DHCPOFFER packets received within 5s:
conn.SetDeadline(time.Now().Add(5 * time.Second))
for {
offer, err := dhcp4.Read(conn)
if err != nil {
log.Fatal(err)
}
if offer == nil {
continue // not a DHCPv4 packet
}
if offer.Xid != discover.Xid {
continue // broadcast reply for different DHCP transaction
}
if !dhcp4.HasMessageType(offer.Options, layers.DHCPMsgTypeOffer) {
continue
}
log.Printf("DHCPOFFER: %+v", offer)
}
}
Output:
Index ¶
- func ClientIDOpt(linkType layers.LinkType, hwaddr net.HardwareAddr) layers.DHCPOption
- func HasMessageType(opts []layers.DHCPOption, mt layers.DHCPMsgType) bool
- func HostnameOpt(hostname string) layers.DHCPOption
- func MessageTypeOpt(msgType layers.DHCPMsgType) layers.DHCPOption
- func ParamsRequestOpt(opts ...layers.DHCPOpt) layers.DHCPOption
- func Read(pc net.PacketConn) (*layers.DHCPv4, error)
- func RequestIPOpt(requestIP net.IP) layers.DHCPOption
- func ServerID(opts []layers.DHCPOption) []layers.DHCPOption
- func Write(pc net.PacketConn, pkt *layers.DHCPv4) error
- func XIDGenerator(hwaddr net.HardwareAddr) func() uint32
- type Lease
- type OptBroadcast
- type OptDNS
- type OptDomainName
- type OptLeaseTime
- type OptRouter
- type OptSubnetMask
- type OptT1
- type Option
Examples ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func ClientIDOpt ¶
func ClientIDOpt(linkType layers.LinkType, hwaddr net.HardwareAddr) layers.DHCPOption
ClientIDOpt is a short-hand for constructing a ClientID DHCP option.
func HasMessageType ¶
func HasMessageType(opts []layers.DHCPOption, mt layers.DHCPMsgType) bool
HasMessageType returns true if any of the specified DHCP options declares the DHCP message type to be mt.
func HostnameOpt ¶
func HostnameOpt(hostname string) layers.DHCPOption
HostnameOpt is a short-hand for constructing a Hostname DHCP option.
func MessageTypeOpt ¶
func MessageTypeOpt(msgType layers.DHCPMsgType) layers.DHCPOption
MessageTypeOpt is a short-hand for constructing a MessageType DHCP option.
func ParamsRequestOpt ¶
func ParamsRequestOpt(opts ...layers.DHCPOpt) layers.DHCPOption
ParamsRequestOpt is a short-hand for constructing a ParamsRequest DHCP option.
func Read ¶
func Read(pc net.PacketConn) (*layers.DHCPv4, error)
Read decodes an IPv4 packet from pc, returning its DHCPv4 layer or nil.
func RequestIPOpt ¶
func RequestIPOpt(requestIP net.IP) layers.DHCPOption
RequestIPOpt is a short-hand for constructing a RequestIP DHCP option.
func ServerID ¶
func ServerID(opts []layers.DHCPOption) []layers.DHCPOption
ServerID extracts all ServerID DHCP options. This is convenient when responding to a server.
func Write ¶
func Write(pc net.PacketConn, pkt *layers.DHCPv4) error
Write encodes pkt as an IPv4 packet to pc.
func XIDGenerator ¶
func XIDGenerator(hwaddr net.HardwareAddr) func() uint32
XIDGenerator returns a function which returns DHCP transaction IDs (xid).
Types ¶
type Lease ¶
type Lease struct {
IP net.IP
Netmask net.IPMask
Broadcast net.IP
Router net.IP
DNS []net.IP
Domain string
RenewalTime time.Duration
}
Lease represents a DHCP lease.
func LeaseFromACK ¶
LeaseFromACK constructs a Lease from the specified DHCPACK packet.
type OptBroadcast ¶
OptBroadcast represents a Broadcast DHCP option.
type OptDomainName ¶
type OptDomainName struct {
DomainName string
}
OptDomainName represents a DomainName DHCP option.
type OptLeaseTime ¶
OptLeaseTime represents a LeaseTime DHCP option.
type OptSubnetMask ¶
OptSubnetMask represents a SubnetMask DHCP option.
type Option ¶
Option is an interface implemented by all Opt* DHCP option types.
func ParseOptions ¶
func ParseOptions(opts []layers.DHCPOption) []Option
ParseOptions converts layers.DHCPOption type/byte-slice pairs into Option.
Source Files