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|
package dhcpv6
import (
"fmt"
"net"
"time"
)
// Client constants
const (
DefaultWriteTimeout = 3 * time.Second // time to wait for write calls
DefaultReadTimeout = 3 * time.Second // time to wait for read calls
DefaultInterfaceUpTimeout = 3 * time.Second // time to wait before a network interface goes up
maxUDPReceivedPacketSize = 8192 // arbitrary size. Theoretically could be up to 65kb
)
// Broadcast destination IP addresses as defined by RFC 3315
var (
AllDHCPRelayAgentsAndServers = net.ParseIP("ff02::1:2")
AllDHCPServers = net.ParseIP("ff05::1:3")
)
// Client implements a DHCPv6 client
type Client struct {
ReadTimeout time.Duration
WriteTimeout time.Duration
LocalAddr net.Addr
RemoteAddr net.Addr
}
// NewClient returns a Client with default settings
func NewClient() *Client {
return &Client{
ReadTimeout: DefaultReadTimeout,
WriteTimeout: DefaultWriteTimeout,
}
}
// Exchange executes a 4-way DHCPv6 request (SOLICIT, ADVERTISE, REQUEST,
// REPLY). If the SOLICIT packet is nil, defaults are used. The modifiers will
// be applied to the Request packet. A common use is to make sure that the
// Request packet has the right options, see modifiers.go
func (c *Client) Exchange(ifname string, solicit DHCPv6, modifiers ...Modifier) ([]DHCPv6, error) {
conversation := make([]DHCPv6, 0)
var err error
// Solicit
solicit, advertise, err := c.Solicit(ifname, solicit)
if solicit != nil {
conversation = append(conversation, solicit)
}
if err != nil {
return conversation, err
}
conversation = append(conversation, advertise)
request, reply, err := c.Request(ifname, advertise, nil)
if request != nil {
conversation = append(conversation, request)
}
for _, mod := range modifiers {
request = mod(request)
}
if err != nil {
return conversation, err
}
conversation = append(conversation, reply)
return conversation, nil
}
func (c *Client) sendReceive(ifname string, packet DHCPv6, expectedType MessageType) (DHCPv6, error) {
if packet == nil {
return nil, fmt.Errorf("Packet to send cannot be nil")
}
if expectedType == MSGTYPE_NONE {
// infer the expected type from the packet being sent
if packet.Type() == SOLICIT {
expectedType = ADVERTISE
} else if packet.Type() == REQUEST {
expectedType = REPLY
} else if packet.Type() == RELAY_FORW {
expectedType = RELAY_REPL
} else if packet.Type() == LEASEQUERY {
expectedType = LEASEQUERY_REPLY
} // and probably more
}
// if no LocalAddr is specified, get the interface's link-local address
var laddr net.UDPAddr
if c.LocalAddr == nil {
llAddr, err := GetLinkLocalAddr(ifname)
if err != nil {
return nil, err
}
laddr = net.UDPAddr{IP: *llAddr, Port: DefaultClientPort, Zone: ifname}
} else {
if addr, ok := c.LocalAddr.(*net.UDPAddr); ok {
laddr = *addr
} else {
return nil, fmt.Errorf("Invalid local address: not a net.UDPAddr: %v", c.LocalAddr)
}
}
// if no RemoteAddr is specified, use AllDHCPRelayAgentsAndServers
var raddr net.UDPAddr
if c.RemoteAddr == nil {
raddr = net.UDPAddr{IP: AllDHCPRelayAgentsAndServers, Port: DefaultServerPort}
} else {
if addr, ok := c.RemoteAddr.(*net.UDPAddr); ok {
raddr = *addr
} else {
return nil, fmt.Errorf("Invalid remote address: not a net.UDPAddr: %v", c.RemoteAddr)
}
}
// prepare the socket to listen on for replies
conn, err := net.ListenUDP("udp6", &laddr)
if err != nil {
return nil, err
}
defer conn.Close()
// send the packet out
conn.SetWriteDeadline(time.Now().Add(c.WriteTimeout))
_, err = conn.WriteTo(packet.ToBytes(), &raddr)
if err != nil {
return nil, err
}
// wait for a reply
oobdata := []byte{} // ignoring oob data
conn.SetReadDeadline(time.Now().Add(c.ReadTimeout))
var (
adv DHCPv6
isMessage bool
)
defer conn.Close()
msg, ok := packet.(*DHCPv6Message)
if ok {
isMessage = true
}
for {
buf := make([]byte, maxUDPReceivedPacketSize)
n, _, _, _, err := conn.ReadMsgUDP(buf, oobdata)
if err != nil {
return nil, err
}
adv, err = FromBytes(buf[:n])
if err != nil {
// skip non-DHCP packets
continue
}
if recvMsg, ok := adv.(*DHCPv6Message); ok && isMessage {
// if a regular message, check the transaction ID first
// XXX should this unpack relay messages and check the XID of the
// inner packet too?
if msg.TransactionID() != recvMsg.TransactionID() {
// different XID, we don't want this packet for sure
continue
}
}
if expectedType == MSGTYPE_NONE {
// just take whatever arrived
break
} else if adv.Type() == expectedType {
break
}
}
return adv, nil
}
// Solicit sends a SOLICIT, return the solicit, an ADVERTISE (if not nil), and
// an error if any
func (c *Client) Solicit(ifname string, solicit DHCPv6) (DHCPv6, DHCPv6, error) {
var err error
if solicit == nil {
solicit, err = NewSolicitForInterface(ifname)
if err != nil {
return nil, nil, err
}
}
advertise, err := c.sendReceive(ifname, solicit, MSGTYPE_NONE)
return solicit, advertise, err
}
// Request sends a REQUEST built from an ADVERTISE if no REQUEST is specified.
// It returns the request, a reply if not nil, and an error if any
func (c *Client) Request(ifname string, advertise, request DHCPv6) (DHCPv6, DHCPv6, error) {
if request == nil {
var err error
request, err = NewRequestFromAdvertise(advertise)
if err != nil {
return nil, nil, err
}
}
reply, err := c.sendReceive(ifname, request, MSGTYPE_NONE)
return request, reply, err
}
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