lbcd/msgaddr.go

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2014-01-09 06:44:08 +01:00
// Copyright (c) 2013-2014 Conformal Systems LLC.
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// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.
package btcwire
import (
"fmt"
"io"
)
// MaxAddrPerMsg is the maximum number of addresses that can be in a single
// bitcoin addr message (MsgAddr).
const MaxAddrPerMsg = 1000
// MsgAddr implements the Message interface and represents a bitcoin
// addr message. It is used to provide a list of known active peers on the
// network. An active peer is considered one that has transmitted a message
// within the last 3 hours. Nodes which have not transmitted in that time
// frame should be forgotten. Each message is limited to a maximum number of
// addresses, which is currently 1000. As a result, multiple messages must
// be used to relay the full list.
//
// Use the AddAddress function to build up the list of known addresses when
// sending an addr message to another peer.
type MsgAddr struct {
AddrList []*NetAddress
}
// AddAddress adds a known active peer to the message.
func (msg *MsgAddr) AddAddress(na *NetAddress) error {
if len(msg.AddrList)+1 > MaxAddrPerMsg {
str := fmt.Sprintf("too many addresses in message [max %v]",
MaxAddrPerMsg)
return messageError("MsgAddr.AddAddress", str)
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}
msg.AddrList = append(msg.AddrList, na)
return nil
}
// AddAddresses adds multiple known active peers to the message.
func (msg *MsgAddr) AddAddresses(netAddrs ...*NetAddress) error {
for _, na := range netAddrs {
err := msg.AddAddress(na)
if err != nil {
return err
}
}
return nil
}
// ClearAddresses removes all addresses from the message.
func (msg *MsgAddr) ClearAddresses() {
msg.AddrList = []*NetAddress{}
}
// BtcDecode decodes r using the bitcoin protocol encoding into the receiver.
// This is part of the Message interface implementation.
func (msg *MsgAddr) BtcDecode(r io.Reader, pver uint32) error {
count, err := readVarInt(r, pver)
if err != nil {
return err
}
// Limit to max addresses per message.
if count > MaxAddrPerMsg {
str := fmt.Sprintf("too many addresses for message "+
"[count %v, max %v]", count, MaxAddrPerMsg)
return messageError("MsgAddr.BtcDecode", str)
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}
msg.AddrList = make([]*NetAddress, 0, count)
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for i := uint64(0); i < count; i++ {
na := NetAddress{}
err := readNetAddress(r, pver, &na, true)
if err != nil {
return err
}
msg.AddAddress(&na)
}
return nil
}
// BtcEncode encodes the receiver to w using the bitcoin protocol encoding.
// This is part of the Message interface implementation.
func (msg *MsgAddr) BtcEncode(w io.Writer, pver uint32) error {
// Protocol versions before MultipleAddressVersion only allowed 1 address
// per message.
count := len(msg.AddrList)
if pver < MultipleAddressVersion && count > 1 {
str := fmt.Sprintf("too many addresses for message of "+
"protocol version %v [count %v, max 1]", pver, count)
return messageError("MsgAddr.BtcEncode", str)
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}
if count > MaxAddrPerMsg {
str := fmt.Sprintf("too many addresses for message "+
"[count %v, max %v]", count, MaxAddrPerMsg)
return messageError("MsgAddr.BtcEncode", str)
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}
err := writeVarInt(w, pver, uint64(count))
if err != nil {
return err
}
for _, na := range msg.AddrList {
err = writeNetAddress(w, pver, na, true)
if err != nil {
return err
}
}
return nil
}
// Command returns the protocol command string for the message. This is part
// of the Message interface implementation.
func (msg *MsgAddr) Command() string {
return cmdAddr
}
// MaxPayloadLength returns the maximum length the payload can be for the
// receiver. This is part of the Message interface implementation.
func (msg *MsgAddr) MaxPayloadLength(pver uint32) uint32 {
if pver < MultipleAddressVersion {
// Num addresses (varInt) + a single net addresses.
return maxVarIntPayload + maxNetAddressPayload(pver)
}
// Num addresses (varInt) + max allowed addresses.
return maxVarIntPayload + (MaxAddrPerMsg * maxNetAddressPayload(pver))
}
// NewMsgAddr returns a new bitcoin addr message that conforms to the
// Message interface. See MsgAddr for details.
func NewMsgAddr() *MsgAddr {
return &MsgAddr{
AddrList: make([]*NetAddress, 0, MaxAddrPerMsg),
}
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}