292 lines
8.4 KiB
Go
292 lines
8.4 KiB
Go
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// Copyright (c) 2013-2016 The btcsuite developers
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// Use of this source code is governed by an ISC
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// license that can be found in the LICENSE file.
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package wire
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import (
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"bytes"
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"fmt"
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"io"
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"net"
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"strings"
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"time"
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)
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// MaxUserAgentLen is the maximum allowed length for the user agent field in a
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// version message (MsgVersion).
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const MaxUserAgentLen = 2000
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// DefaultUserAgent for wire in the stack
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const DefaultUserAgent = "/btcwire:0.4.0/"
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// MsgVersion implements the Message interface and represents a bitcoin version
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// message. It is used for a peer to advertise itself as soon as an outbound
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// connection is made. The remote peer then uses this information along with
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// its own to negotiate. The remote peer must then respond with a version
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// message of its own containing the negotiated values followed by a verack
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// message (MsgVerAck). This exchange must take place before any further
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// communication is allowed to proceed.
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type MsgVersion struct {
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// Version of the protocol the node is using.
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ProtocolVersion int32
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// Bitfield which identifies the enabled services.
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Services ServiceFlag
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// Time the message was generated. This is encoded as an int64 on the wire.
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Timestamp time.Time
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// Address of the remote peer.
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AddrYou NetAddress
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// Address of the local peer.
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AddrMe NetAddress
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// Unique value associated with message that is used to detect self
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// connections.
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Nonce uint64
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// The user agent that generated messsage. This is a encoded as a varString
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// on the wire. This has a max length of MaxUserAgentLen.
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UserAgent string
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// Last block seen by the generator of the version message.
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LastBlock int32
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// Don't announce transactions to peer.
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DisableRelayTx bool
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}
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// HasService returns whether the specified service is supported by the peer
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// that generated the message.
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func (msg *MsgVersion) HasService(service ServiceFlag) bool {
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return msg.Services&service == service
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}
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// AddService adds service as a supported service by the peer generating the
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// message.
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func (msg *MsgVersion) AddService(service ServiceFlag) {
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msg.Services |= service
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}
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// BtcDecode decodes r using the bitcoin protocol encoding into the receiver.
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// The version message is special in that the protocol version hasn't been
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// negotiated yet. As a result, the pver field is ignored and any fields which
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// are added in new versions are optional. This also mean that r must be a
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// *bytes.Buffer so the number of remaining bytes can be ascertained.
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//
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// This is part of the Message interface implementation.
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func (msg *MsgVersion) BtcDecode(r io.Reader, pver uint32) error {
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buf, ok := r.(*bytes.Buffer)
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if !ok {
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return fmt.Errorf("MsgVersion.BtcDecode reader is not a " +
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"*bytes.Buffer")
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}
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err := readElements(buf, &msg.ProtocolVersion, &msg.Services,
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(*int64Time)(&msg.Timestamp))
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if err != nil {
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return err
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}
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err = readNetAddress(buf, pver, &msg.AddrYou, false)
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if err != nil {
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return err
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}
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// Protocol versions >= 106 added a from address, nonce, and user agent
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// field and they are only considered present if there are bytes
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// remaining in the message.
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if buf.Len() > 0 {
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err = readNetAddress(buf, pver, &msg.AddrMe, false)
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if err != nil {
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return err
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}
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}
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if buf.Len() > 0 {
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err = readElement(buf, &msg.Nonce)
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if err != nil {
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return err
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}
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}
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if buf.Len() > 0 {
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userAgent, err := ReadVarString(buf, pver)
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if err != nil {
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return err
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}
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err = validateUserAgent(userAgent)
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if err != nil {
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return err
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}
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msg.UserAgent = userAgent
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}
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// Protocol versions >= 209 added a last known block field. It is only
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// considered present if there are bytes remaining in the message.
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if buf.Len() > 0 {
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err = readElement(buf, &msg.LastBlock)
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if err != nil {
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return err
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}
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}
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// There was no relay transactions field before BIP0037Version, but
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// the default behavior prior to the addition of the field was to always
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// relay transactions.
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if buf.Len() > 0 {
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// It's safe to ignore the error here since the buffer has at
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// least one byte and that byte will result in a boolean value
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// regardless of its value. Also, the wire encoding for the
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// field is true when transactions should be relayed, so reverse
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// it for the DisableRelayTx field.
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var relayTx bool
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readElement(r, &relayTx)
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msg.DisableRelayTx = !relayTx
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}
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return nil
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}
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// BtcEncode encodes the receiver to w using the bitcoin protocol encoding.
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// This is part of the Message interface implementation.
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func (msg *MsgVersion) BtcEncode(w io.Writer, pver uint32) error {
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err := validateUserAgent(msg.UserAgent)
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if err != nil {
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return err
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}
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err = writeElements(w, msg.ProtocolVersion, msg.Services,
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msg.Timestamp.Unix())
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if err != nil {
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return err
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}
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err = writeNetAddress(w, pver, &msg.AddrYou, false)
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if err != nil {
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return err
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}
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err = writeNetAddress(w, pver, &msg.AddrMe, false)
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if err != nil {
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return err
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}
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err = writeElement(w, msg.Nonce)
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if err != nil {
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return err
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}
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err = WriteVarString(w, pver, msg.UserAgent)
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if err != nil {
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return err
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}
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err = writeElement(w, msg.LastBlock)
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if err != nil {
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return err
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}
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// There was no relay transactions field before BIP0037Version. Also,
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// the wire encoding for the field is true when transactions should be
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// relayed, so reverse it from the DisableRelayTx field.
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if pver >= BIP0037Version {
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err = writeElement(w, !msg.DisableRelayTx)
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if err != nil {
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return err
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}
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}
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return nil
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}
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// Command returns the protocol command string for the message. This is part
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// of the Message interface implementation.
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func (msg *MsgVersion) Command() string {
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return CmdVersion
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}
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// MaxPayloadLength returns the maximum length the payload can be for the
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// receiver. This is part of the Message interface implementation.
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func (msg *MsgVersion) MaxPayloadLength(pver uint32) uint32 {
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// XXX: <= 106 different
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// Protocol version 4 bytes + services 8 bytes + timestamp 8 bytes +
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// remote and local net addresses + nonce 8 bytes + length of user
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// agent (varInt) + max allowed useragent length + last block 4 bytes +
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// relay transactions flag 1 byte.
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return 33 + (maxNetAddressPayload(pver) * 2) + MaxVarIntPayload +
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MaxUserAgentLen
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}
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// NewMsgVersion returns a new bitcoin version message that conforms to the
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// Message interface using the passed parameters and defaults for the remaining
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// fields.
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func NewMsgVersion(me *NetAddress, you *NetAddress, nonce uint64,
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lastBlock int32) *MsgVersion {
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// Limit the timestamp to one second precision since the protocol
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// doesn't support better.
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return &MsgVersion{
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ProtocolVersion: int32(ProtocolVersion),
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Services: 0,
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Timestamp: time.Unix(time.Now().Unix(), 0),
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AddrYou: *you,
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AddrMe: *me,
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Nonce: nonce,
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UserAgent: DefaultUserAgent,
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LastBlock: lastBlock,
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DisableRelayTx: false,
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}
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}
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// NewMsgVersionFromConn is a convenience function that extracts the remote
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// and local address from conn and returns a new bitcoin version message that
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// conforms to the Message interface. See NewMsgVersion.
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func NewMsgVersionFromConn(conn net.Conn, nonce uint64,
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lastBlock int32) (*MsgVersion, error) {
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// Don't assume any services until we know otherwise.
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lna, err := NewNetAddress(conn.LocalAddr(), 0)
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if err != nil {
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return nil, err
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}
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// Don't assume any services until we know otherwise.
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rna, err := NewNetAddress(conn.RemoteAddr(), 0)
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if err != nil {
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return nil, err
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}
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return NewMsgVersion(lna, rna, nonce, lastBlock), nil
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}
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// validateUserAgent checks userAgent length against MaxUserAgentLen
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func validateUserAgent(userAgent string) error {
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if len(userAgent) > MaxUserAgentLen {
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str := fmt.Sprintf("user agent too long [len %v, max %v]",
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len(userAgent), MaxUserAgentLen)
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return messageError("MsgVersion", str)
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}
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return nil
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}
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// AddUserAgent adds a user agent to the user agent string for the version
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// message. The version string is not defined to any strict format, although
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// it is recommended to use the form "major.minor.revision" e.g. "2.6.41".
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func (msg *MsgVersion) AddUserAgent(name string, version string,
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comments ...string) error {
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newUserAgent := fmt.Sprintf("%s:%s", name, version)
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if len(comments) != 0 {
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newUserAgent = fmt.Sprintf("%s(%s)", newUserAgent,
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strings.Join(comments, "; "))
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}
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newUserAgent = fmt.Sprintf("%s%s/", msg.UserAgent, newUserAgent)
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err := validateUserAgent(newUserAgent)
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if err != nil {
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return err
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}
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msg.UserAgent = newUserAgent
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return nil
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}
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