dhcp4

Documentation

Overview

Package dhcp4 provides building blocks for DHCP clients and servers.

Index

• type Conn
  • func NewConn(addr string) (*Conn, error)
  • func NewSnooperConn(addr string) (*Conn, error)
  • func (c *Conn) Close() error
  • func (c *Conn) RecvDHCP() (*Packet, *net.Interface, error)
  • func (c *Conn) SendDHCP(pkt *Packet, intf *net.Interface) error
  • func (c *Conn) SetReadDeadline(t time.Time) error
  • func (c *Conn) SetWriteDeadline(t time.Time) error
• type MessageType
  • func (mt MessageType) String() string
• type Option
• type Options
  • func (o Options) Byte(n Option) (byte, error)
  • func (o Options) Bytes(n Option) ([]byte, error)
  • func (o Options) Copy() Options
  • func (o Options) GUID(n Option) (string, error)
  • func (o Options) IP(n Option) (net.IP, error)
  • func (o Options) IPMask(n Option) (net.IPMask, error)
  • func (o Options) IPs(n Option) ([]net.IP, error)
  • func (o Options) Int32(n Option) (int32, error)
  • func (o Options) Marshal() ([]byte, error)
  • func (o Options) String(n Option) (string, error)
  • func (o Options) Uint16(n Option) (uint16, error)
  • func (o Options) Uint32(n Option) (uint32, error)
  • func (o Options) Unmarshal(bs []byte) error
• type Packet
  • func Unmarshal(bs []byte) (*Packet, error)
  • func (p *Packet) DebugString() string
  • func (p *Packet) Marshal() ([]byte, error)

Types

type Conn

type Conn struct {
	// contains filtered or unexported fields
}

Conn is a DHCP-oriented packet socket.

Multiple goroutines may invoke methods on a Conn simultaneously.

func NewConn

func NewConn(addr string) (*Conn, error)

NewConn creates a Conn bound to the given UDP ip:port.

func NewSnooperConn

func NewSnooperConn(addr string) (*Conn, error)

NewSnooperConn creates a Conn that listens on the given UDP ip:port.

Unlike NewConn, NewSnooperConn does not bind to the ip:port, enabling the Conn to coexist with other services on the machine.

func (*Conn) Close

func (c *Conn) Close() error

Close closes the DHCP socket. Any blocked Read or Write operations will be unblocked and return errors.

func (*Conn) RecvDHCP

func (c *Conn) RecvDHCP() (*Packet, *net.Interface, error)

RecvDHCP reads a Packet from the connection. It returns the packet and the interface it was received on.

func (*Conn) SendDHCP

func (c *Conn) SendDHCP(pkt *Packet, intf *net.Interface) error

SendDHCP sends pkt. The precise transmission mechanism depends on pkt.txType(). intf should be the net.Interface returned by RecvDHCP if responding to a DHCP client, or the interface for which configuration is desired if acting as a client.

func (*Conn) SetReadDeadline

func (c *Conn) SetReadDeadline(t time.Time) error

SetReadDeadline sets the deadline for future Read calls. If the deadline is reached, Read will fail with a timeout (see net.Error) instead of blocking. A zero value for t means Read will not time out.

func (*Conn) SetWriteDeadline

func (c *Conn) SetWriteDeadline(t time.Time) error

SetWriteDeadline sets the deadline for future Write calls. If the deadline is reached, Write will fail with a timeout (see net.Error) instead of blocking. A zero value for t means Write will not time out.

type MessageType

type MessageType int

MessageType is the type of a DHCP message.

const (
	MsgDiscover MessageType = iota + 1
	MsgOffer
	MsgRequest
	MsgDecline
	MsgAck
	MsgNack
	MsgRelease
	MsgInform
)

Message types as described in RFC 2131.

func (MessageType) String

func (mt MessageType) String() string

type Option

type Option byte

Option is a DHCP option.

const (
	OptSubnetMask         Option = 1  // IPMask
	OptTimeOffset         Option = 2  // int32
	OptRouters            Option = 3  // IPs
	OptDNSServers         Option = 6  // IPs
	OptHostname           Option = 12 // string
	OptBootFileSize       Option = 13 // uint16
	OptDomainName         Option = 15 // string
	OptInterfaceMTU       Option = 26 // uint16
	OptBroadcastAddr      Option = 28 // IP
	OptNTPServers         Option = 42 // IP
	OptVendorSpecific     Option = 43 // []byte
	OptRequestedIP        Option = 50 // IP
	OptLeaseTime          Option = 51 // uint32
	OptOverload           Option = 52 // byte
	OptServerIdentifier   Option = 54 // IP
	OptRequestedOptions   Option = 55 // []byte
	OptMessage            Option = 56 // string
	OptMaximumMessageSize Option = 57 // uint16
	OptRenewalTime        Option = 58 // uint32
	OptRebindingTime      Option = 59 // uint32
	OptVendorIdentifier   Option = 60 // string
	OptClientIdentifier   Option = 61 // string
	OptFQDN               Option = 81 // string
	OptAgentInformation   Option = 82 // struct

	OptTFTPServer      Option = 66 // string
	OptBootFile        Option = 67 // string
	OptDHCPMessageType Option = 53 // byte
)

Some of the more commonly seen DHCP options. Refer to http://www.iana.org/assignments/bootp-dhcp-parameters/bootp-dhcp-parameters.xhtml for the full authoritative list.

type Options

type Options map[Option][]byte

Options stores DHCP options.

func (Options) Byte

func (o Options) Byte(n Option) (byte, error)

Byte returns the value of option n as a byte.

func (Options) Bytes

func (o Options) Bytes(n Option) ([]byte, error)

Bytes returns the value of option n as a byte slice.

func (Options) Copy

func (o Options) Copy() Options

Copy returns a shallow copy of o.

func (Options) GUID

func (o Options) GUID(n Option) (string, error)

GUID returns the value of option n as a guid string.

func (Options) IP

func (o Options) IP(n Option) (net.IP, error)

IP returns the value of option n as an IPv4 address.

func (Options) IPMask

func (o Options) IPMask(n Option) (net.IPMask, error)

IPMask returns the value of option n as a net.IPMask.

func (Options) IPs

func (o Options) IPs(n Option) ([]net.IP, error)

IPs returns the value of option n as a list of IPv4 addresses.

func (Options) Int32

func (o Options) Int32(n Option) (int32, error)

Int32 returns the value of option n as an int32.

func (Options) Marshal

func (o Options) Marshal() ([]byte, error)

Marshal returns the wire encoding of o.

func (Options) String

func (o Options) String(n Option) (string, error)

String returns the value of option n as a string.

func (Options) Uint16

func (o Options) Uint16(n Option) (uint16, error)

Uint16 returns the value of option n as a uint16.

func (Options) Uint32

func (o Options) Uint32(n Option) (uint32, error)

Uint32 returns the value of option n as a uint32.

func (Options) Unmarshal

func (o Options) Unmarshal(bs []byte) error

Unmarshal parses DHCP options into o.

type Packet

type Packet struct {
	Type          MessageType
	TransactionID []byte // Always 4 bytes
	Broadcast     bool
	HardwareAddr  net.HardwareAddr // Only ethernet supported at the moment

	ClientAddr net.IP // Client's current IP address (it will respond to ARP for this IP)
	YourAddr   net.IP // Client IP address offered/assigned by server
	ServerAddr net.IP // Responding server's IP address
	RelayAddr  net.IP // IP address of DHCP relay agent, if an agent forwarded the request

	BootServerName string
	BootFilename   string

	Options Options
}

Packet represents a DHCP packet.

func Unmarshal

func Unmarshal(bs []byte) (*Packet, error)

Unmarshal parses a DHCP message and returns a Packet.

func (*Packet) DebugString

func (p *Packet) DebugString() string

DebugString prints the contents of a DHCP packet for human consumption.

func (*Packet) Marshal

func (p *Packet) Marshal() ([]byte, error)

Marshal returns the wire encoding of p.