feat: replace ProtocolName with AsRef<str>

Previously, a protocol could be any sequence of bytes as long as it started with `/`. Now, we directly parse a protocol as `String` which enforces it to be valid UTF8.

To notify users of this change, we delete the `ProtocolName` trait. The new requirement is that users need to provide a type that implements `AsRef<str>`.

We also add a `StreamProtocol` newtype in `libp2p-swarm` which provides an easy way for users to ensure their protocol strings are compliant. The newtype enforces that protocol strings start with `/`. `StreamProtocol` also implements `AsRef<str>`, meaning users can directly use it in their upgrades.

`multistream-select` by itself only changes marginally with this patch. The only thing we enforce in the type-system is that protocols must implement `AsRef<str>`.

Resolves: #2831.

Pull-Request: #3746.

protocols/relay/src/protocol.rs

@@ -19,14 +19,17 @@
 // DEALINGS IN THE SOFTWARE.
 
 use crate::proto;
+use libp2p_swarm::StreamProtocol;
 use std::time::Duration;
 
 pub(crate) mod inbound_hop;
 pub(crate) mod inbound_stop;
 pub(crate) mod outbound_hop;
 pub(crate) mod outbound_stop;
-pub const HOP_PROTOCOL_NAME: &[u8; 31] = b"/libp2p/circuit/relay/0.2.0/hop";
-pub const STOP_PROTOCOL_NAME: &[u8; 32] = b"/libp2p/circuit/relay/0.2.0/stop";
+pub const HOP_PROTOCOL_NAME: StreamProtocol =
+    StreamProtocol::new("/libp2p/circuit/relay/0.2.0/hop");
+pub const STOP_PROTOCOL_NAME: StreamProtocol =
+    StreamProtocol::new("/libp2p/circuit/relay/0.2.0/stop");
 
 const MAX_MESSAGE_SIZE: usize = 4096;
 

protocols/relay/src/protocol/inbound_hop.rs

@@ -26,7 +26,7 @@ use futures::{future::BoxFuture, prelude::*};
 use instant::{Duration, SystemTime};
 use libp2p_core::{upgrade, Multiaddr};
 use libp2p_identity::PeerId;
-use libp2p_swarm::NegotiatedSubstream;
+use libp2p_swarm::{NegotiatedSubstream, StreamProtocol};
 use std::convert::TryInto;
 use std::iter;
 use thiserror::Error;
@@ -38,7 +38,7 @@ pub struct Upgrade {
 }
 
 impl upgrade::UpgradeInfo for Upgrade {
-    type Info = &'static [u8];
+    type Info = StreamProtocol;
     type InfoIter = iter::Once<Self::Info>;
 
     fn protocol_info(&self) -> Self::InfoIter {

protocols/relay/src/protocol/inbound_stop.rs

@@ -25,14 +25,14 @@ use bytes::Bytes;
 use futures::{future::BoxFuture, prelude::*};
 use libp2p_core::upgrade;
 use libp2p_identity::PeerId;
-use libp2p_swarm::NegotiatedSubstream;
+use libp2p_swarm::{NegotiatedSubstream, StreamProtocol};
 use std::iter;
 use thiserror::Error;
 
 pub struct Upgrade {}
 
 impl upgrade::UpgradeInfo for Upgrade {
-    type Info = &'static [u8];
+    type Info = StreamProtocol;
     type InfoIter = iter::Once<Self::Info>;
 
     fn protocol_info(&self) -> Self::InfoIter {

protocols/relay/src/protocol/outbound_hop.rs

@@ -27,7 +27,7 @@ use futures_timer::Delay;
 use instant::{Duration, SystemTime};
 use libp2p_core::{upgrade, Multiaddr};
 use libp2p_identity::PeerId;
-use libp2p_swarm::NegotiatedSubstream;
+use libp2p_swarm::{NegotiatedSubstream, StreamProtocol};
 use std::convert::TryFrom;
 use std::iter;
 use thiserror::Error;
@@ -38,7 +38,7 @@ pub enum Upgrade {
 }
 
 impl upgrade::UpgradeInfo for Upgrade {
-    type Info = &'static [u8];
+    type Info = StreamProtocol;
     type InfoIter = iter::Once<Self::Info>;
 
     fn protocol_info(&self) -> Self::InfoIter {

protocols/relay/src/protocol/outbound_stop.rs

@@ -25,7 +25,7 @@ use bytes::Bytes;
 use futures::{future::BoxFuture, prelude::*};
 use libp2p_core::upgrade;
 use libp2p_identity::PeerId;
-use libp2p_swarm::NegotiatedSubstream;
+use libp2p_swarm::{NegotiatedSubstream, StreamProtocol};
 use std::convert::TryInto;
 use std::iter;
 use std::time::Duration;
@@ -38,7 +38,7 @@ pub struct Upgrade {
 }
 
 impl upgrade::UpgradeInfo for Upgrade {
-    type Info = &'static [u8];
+    type Info = StreamProtocol;
     type InfoIter = iter::Once<Self::Info>;
 
     fn protocol_info(&self) -> Self::InfoIter {

protocols/relay/src/v2.rs

@@ -154,18 +154,6 @@ pub mod protocol {
         note = "Use libp2p_relay::outbound::stop::FatalUpgradeError instead."
     )]
     pub type OutboundStopFatalUpgradeError = crate::outbound::stop::FatalUpgradeError;
-
-    #[deprecated(
-        since = "0.15.0",
-        note = "Use libp2p_relay::HOP_PROTOCOL_NAME instead."
-    )]
-    pub const HOP_PROTOCOL_NAME: &[u8; 31] = crate::HOP_PROTOCOL_NAME;
-
-    #[deprecated(
-        since = "0.15.0",
-        note = "Use libp2p_relay::STOP_PROTOCOL_NAME instead."
-    )]
-    pub const STOP_PROTOCOL_NAME: &[u8; 32] = crate::STOP_PROTOCOL_NAME;
 }
 
 #[deprecated(