config: Add user agent comments flag --uacomment

Just like Core's -uacomment, this flag allows to specify user agent
comments like defined in BIP 14.

config.go

@@ -141,6 +141,7 @@ type config struct {
 	BlockMinSize         uint32        `long:"blockminsize" description:"Mininum block size in bytes to be used when creating a block"`
 	BlockMaxSize         uint32        `long:"blockmaxsize" description:"Maximum block size in bytes to be used when creating a block"`
 	BlockPrioritySize    uint32        `long:"blockprioritysize" description:"Size in bytes for high-priority/low-fee transactions when creating a block"`
+	UserAgentComments    []string      `long:"uacomment" description:"Comment to add to the user agent -- See BIP 14 for more information."`
 	NoPeerBloomFilters   bool          `long:"nopeerbloomfilters" description:"Disable bloom filtering support"`
 	SigCacheMaxSize      uint          `long:"sigcachemaxsize" description:"The maximum number of entries in the signature verification cache"`
 	BlocksOnly           bool          `long:"blocksonly" description:"Do not accept transactions from remote peers."`
@@ -736,6 +737,18 @@ func loadConfig() (*config, []string, error) {
 	cfg.BlockPrioritySize = minUint32(cfg.BlockPrioritySize, cfg.BlockMaxSize)
 	cfg.BlockMinSize = minUint32(cfg.BlockMinSize, cfg.BlockMaxSize)
 
+	// Look for illegal characters in the user agent comments.
+	for _, uaComment := range cfg.UserAgentComments {
+		if strings.ContainsAny(uaComment, "/:()") {
+			err := fmt.Errorf("%s: The following characters must not "+
+				"appear in user agent comments: '/', ':', '(', ')'",
+				funcName)
+			fmt.Fprintln(os.Stderr, err)
+			fmt.Fprintln(os.Stderr, usageMessage)
+			return nil, nil, err
+		}
+	}
+
 	// --txindex and --droptxindex do not mix.
 	if cfg.TxIndex && cfg.DropTxIndex {
 		err := fmt.Errorf("%s: the --txindex and --droptxindex "+

doc.go

@@ -77,6 +77,8 @@ Application Options:
       --addcheckpoint=      Add a custom checkpoint.  Format: '<height>:<hash>'
       --nocheckpoints       Disable built-in checkpoints.  Don't do this unless
                             you know what you're doing.
+      --uacomment=          Comment to add to the user agent --
+                            See BIP 14 for more information.
       --dbtype=             Database backend to use for the Block Chain (ffldb)
       --profile=            Enable HTTP profiling on given port -- NOTE port
                             must be between 1024 and 65536

peer/peer.go

@@ -214,6 +214,11 @@ type Config struct {
 	// form "major.minor.revision" e.g. "2.6.41".
 	UserAgentVersion string
 
+	// UserAgentComments specify the user agent comments to advertise.  These
+	// values must not contain the illegal characters specified in BIP 14:
+	// '/', ':', '(', ')'.
+	UserAgentComments []string
+
 	// ChainParams identifies which chain parameters the peer is associated
 	// with.  It is highly recommended to specify this field, however it can
 	// be omitted in which case the test network will be used.
@@ -799,7 +804,8 @@ func (p *Peer) localVersionMsg() (*wire.MsgVersion, error) {
 
 	// Version message.
 	msg := wire.NewMsgVersion(ourNA, theirNA, nonce, blockNum)
-	msg.AddUserAgent(p.cfg.UserAgentName, p.cfg.UserAgentVersion)
+	msg.AddUserAgent(p.cfg.UserAgentName, p.cfg.UserAgentVersion,
+		p.cfg.UserAgentComments...)
 
 	// XXX: bitcoind appears to always enable the full node services flag
 	// of the remote peer netaddress field in the version message regardless

peer/peer_test.go

@@ -218,13 +218,14 @@ func TestPeerConnection(t *testing.T) {
 				}
 			},
 		},
-		UserAgentName:    "peer",
-		UserAgentVersion: "1.0",
-		ChainParams:      &chaincfg.MainNetParams,
-		Services:         0,
+		UserAgentName:     "peer",
+		UserAgentVersion:  "1.0",
+		UserAgentComments: []string{"comment"},
+		ChainParams:       &chaincfg.MainNetParams,
+		Services:          0,
 	}
 	wantStats := peerStats{
-		wantUserAgent:       wire.DefaultUserAgent + "peer:1.0/",
+		wantUserAgent:       wire.DefaultUserAgent + "peer:1.0(comment)/",
 		wantServices:        0,
 		wantProtocolVersion: peer.MaxProtocolVersion,
 		wantConnected:       true,
@@ -234,8 +235,8 @@ func TestPeerConnection(t *testing.T) {
 		wantLastPingNonce:   uint64(0),
 		wantLastPingMicros:  int64(0),
 		wantTimeOffset:      int64(0),
-		wantBytesSent:       158, // 134 version + 24 verack
-		wantBytesReceived:   158,
+		wantBytesSent:       167, // 143 version + 24 verack
+		wantBytesReceived:   167,
 	}
 	tests := []struct {
 		name  string
@@ -387,10 +388,11 @@ func TestPeerListeners(t *testing.T) {
 				ok <- msg
 			},
 		},
-		UserAgentName:    "peer",
-		UserAgentVersion: "1.0",
-		ChainParams:      &chaincfg.MainNetParams,
-		Services:         wire.SFNodeBloom,
+		UserAgentName:     "peer",
+		UserAgentVersion:  "1.0",
+		UserAgentComments: []string{"comment"},
+		ChainParams:       &chaincfg.MainNetParams,
+		Services:          wire.SFNodeBloom,
 	}
 	inConn, outConn := pipe(
 		&conn{raddr: "10.0.0.1:8333"},
@@ -535,10 +537,11 @@ func TestOutboundPeer(t *testing.T) {
 		NewestBlock: func() (*chainhash.Hash, int32, error) {
 			return nil, 0, errors.New("newest block not found")
 		},
-		UserAgentName:    "peer",
-		UserAgentVersion: "1.0",
-		ChainParams:      &chaincfg.MainNetParams,
-		Services:         0,
+		UserAgentName:     "peer",
+		UserAgentVersion:  "1.0",
+		UserAgentComments: []string{"comment"},
+		ChainParams:       &chaincfg.MainNetParams,
+		Services:          0,
 	}
 
 	r, w := io.Pipe()

sample-btcd.conf

@@ -156,6 +156,9 @@
 ; Add additional checkpoints. Format: '<height>:<hash>'
 ; addcheckpoint=<height>:<hash>
 
+; Add comments to the user agent that is advertised to peers.
+; Must not include characters '/', ':', '(' and ')'.
+; uacomment=
 
 ; ------------------------------------------------------------------------------
 ; RPC server options - The following options control the built-in RPC server

server.go

@@ -1617,15 +1617,16 @@ func newPeerConfig(sp *serverPeer) *peer.Config {
 			// other implementations' alert messages, we will not relay theirs.
 			OnAlert: nil,
 		},
-		NewestBlock:      sp.newestBlock,
-		HostToNetAddress: sp.server.addrManager.HostToNetAddress,
-		Proxy:            cfg.Proxy,
-		UserAgentName:    userAgentName,
-		UserAgentVersion: userAgentVersion,
-		ChainParams:      sp.server.chainParams,
-		Services:         sp.server.services,
-		DisableRelayTx:   cfg.BlocksOnly,
-		ProtocolVersion:  wire.FeeFilterVersion,
+		NewestBlock:       sp.newestBlock,
+		HostToNetAddress:  sp.server.addrManager.HostToNetAddress,
+		Proxy:             cfg.Proxy,
+		UserAgentName:     userAgentName,
+		UserAgentVersion:  userAgentVersion,
+		UserAgentComments: cfg.UserAgentComments,
+		ChainParams:       sp.server.chainParams,
+		Services:          sp.server.services,
+		DisableRelayTx:    cfg.BlocksOnly,
+		ProtocolVersion:   wire.FeeFilterVersion,
 	}
 }