new: allow overriding the user-agent with an option

Instead of using a global variable.

This also:

* Adds an option to the identify service to set the user agent.
* Removes the ability to pass an identify service to NewHost as any reasonable
  Identify service already needs to be constructed with an instance of the host.

config/config.go

@@ -44,6 +44,8 @@ type RoutingC func(host.Host) (routing.PeerRouting, error)
 // This is *not* a stable interface. Use the options defined in the root
 // package.
 type Config struct {
+	UserAgent string
+
 	PeerKey crypto.PrivKey
 
 	Transports         []TptC

options.go

@@ -319,3 +319,11 @@ var NoTransports = func(cfg *Config) error {
 	cfg.Transports = []config.TptC{}
 	return nil
 }
+
+// UserAgent sets the libp2p user-agent sent along with the identify protocol
+func UserAgent(userAgent string) Option {
+	return func(cfg *Config) error {
+		cfg.UserAgent = userAgent
+		return nil
+	}
+}

p2p/host/basic/basic_host.go

@@ -100,10 +100,6 @@ type HostOpts struct {
 	// If below 0, timeouts on streams will be deactivated.
 	NegotiationTimeout time.Duration
 
-	// IdentifyService holds an implementation of the /ipfs/id/ protocol.
-	// If omitted, a new *identify.IDService will be used.
-	IdentifyService *identify.IDService
-
 	// AddrsFactory holds a function which can be used to override or filter the result of Addrs.
 	// If omitted, there's no override or filtering, and the results of Addrs and AllAddrs are the same.
 	AddrsFactory AddrsFactory
@@ -121,6 +117,9 @@ type HostOpts struct {
 
 	// EnablePing indicates whether to instantiate the ping service
 	EnablePing bool
+
+	// UserAgent sets the user-agent for the host. Defaults to ClientVersion.
+	UserAgent string
 }
 
 // NewHost constructs a new *BasicHost and activates it by attaching its stream and connection handlers to the given inet.Network.
@@ -154,12 +153,12 @@ func NewHost(ctx context.Context, net network.Network, opts *HostOpts) (*BasicHo
 		h.mux = opts.MultistreamMuxer
 	}
 
-	if opts.IdentifyService != nil {
-		h.ids = opts.IdentifyService
-	} else {
-		// we can't set this as a default above because it depends on the *BasicHost.
-		h.ids = identify.NewIDService(goprocessctx.WithProcessClosing(ctx, h.proc), h)
-	}
+	// we can't set this as a default above because it depends on the *BasicHost.
+	h.ids = identify.NewIDService(
+		goprocessctx.WithProcessClosing(ctx, h.proc),
+		h,
+		identify.UserAgent(opts.UserAgent),
+	)
 
 	if uint64(opts.NegotiationTimeout) != 0 {
 		h.negtimeout = opts.NegotiationTimeout

p2p/protocol/identify/id.go

@@ -47,7 +47,8 @@ const transientTTL = 10 * time.Second
 //  * Our IPFS Agent Version
 //  * Our public Listen Addresses
 type IDService struct {
-	Host host.Host
+	Host      host.Host
+	UserAgent string
 
 	ctx context.Context
 
@@ -70,9 +71,21 @@ type IDService struct {
 
 // NewIDService constructs a new *IDService and activates it by
 // attaching its stream handler to the given host.Host.
-func NewIDService(ctx context.Context, h host.Host) *IDService {
+func NewIDService(ctx context.Context, h host.Host, opts ...Option) *IDService {
+	var cfg config
+	for _, opt := range opts {
+		opt(&cfg)
+	}
+
+	userAgent := ClientVersion
+	if cfg.userAgent != "" {
+		userAgent = cfg.userAgent
+	}
+
 	s := &IDService{
-		Host:          h,
+		Host:      h,
+		UserAgent: userAgent,
+
 		ctx:           ctx,
 		currid:        make(map[network.Conn]chan struct{}),
 		observedAddrs: NewObservedAddrSet(ctx),
@@ -306,7 +319,7 @@ func (ids *IDService) populateMessage(mes *pb.Identify, c network.Conn) {
 
 	// set protocol versions
 	pv := LibP2PVersion
-	av := ClientVersion
+	av := ids.UserAgent
 	mes.ProtocolVersion = &pv
 	mes.AgentVersion = &av
 }

p2p/protocol/identify/opts.go

@@ -0,0 +1,13 @@
+package identify
+
+type config struct {
+	userAgent string
+}
+
+type Option func(*config)
+
+func UserAgent(ua string) Option {
+	return func(cfg *config) {
+		cfg.userAgent = ua
+	}
+}