feat: remove Mplex

Mplex does not implement backpressure, our implementation will randomly reset streams if buffers overflow instead of risking deadlocks.

In the past we had a bug where kubo nodes would prefer mplex over yamux. Turning off mplex make our connections to thoses nodes negociate yamux.

Closes #9958

core/node/libp2p/smux.go

@@ -3,13 +3,11 @@ package libp2p
 import (
 	"fmt"
 	"os"
-	"strings"
 
 	"github.com/ipfs/kubo/config"
 
 	"github.com/libp2p/go-libp2p"
 	"github.com/libp2p/go-libp2p/core/network"
-	"github.com/libp2p/go-libp2p/p2p/muxer/mplex"
 	"github.com/libp2p/go-libp2p/p2p/muxer/yamux"
 )
 
@@ -23,45 +21,17 @@ func yamuxTransport() network.Multiplexer {
 }
 
 func makeSmuxTransportOption(tptConfig config.Transports) (libp2p.Option, error) {
-	const yamuxID = "/yamux/1.0.0"
-	const mplexID = "/mplex/6.7.0"
-
 	if prefs := os.Getenv("LIBP2P_MUX_PREFS"); prefs != "" {
-		// Using legacy LIBP2P_MUX_PREFS variable.
-		log.Error("LIBP2P_MUX_PREFS is now deprecated.")
-		log.Error("Use the `Swarm.Transports.Multiplexers' config field.")
-		muxers := strings.Fields(prefs)
-		enabled := make(map[string]bool, len(muxers))
-
-		var opts []libp2p.Option
-		for _, tpt := range muxers {
-			if enabled[tpt] {
-				return nil, fmt.Errorf(
-					"duplicate muxer found in LIBP2P_MUX_PREFS: %s",
-					tpt,
-				)
-			}
-			switch tpt {
-			case yamuxID:
-				opts = append(opts, libp2p.Muxer(tpt, yamuxTransport()))
-			case mplexID:
-				opts = append(opts, libp2p.Muxer(tpt, mplex.DefaultTransport))
-			default:
-				return nil, fmt.Errorf("unknown muxer: %s", tpt)
-			}
-		}
-		return libp2p.ChainOptions(opts...), nil
-	} else {
-		return prioritizeOptions([]priorityOption{{
-			priority:        tptConfig.Multiplexers.Yamux,
-			defaultPriority: 100,
-			opt:             libp2p.Muxer(yamuxID, yamuxTransport()),
-		}, {
-			priority:        tptConfig.Multiplexers.Mplex,
-			defaultPriority: 200,
-			opt:             libp2p.Muxer(mplexID, mplex.DefaultTransport),
-		}}), nil
+		return nil, fmt.Errorf("configuring muxers with LIBP2P_MUX_PREFS is no longer supported")
 	}
+	if tptConfig.Multiplexers.Mplex != 0 {
+		return nil, fmt.Errorf("Swarm.Transports.Multiplexers.Mplex is no longer supported")
+	}
+	if tptConfig.Multiplexers.Yamux < 0 {
+		return nil, fmt.Errorf("Swarm.Transports.Multiplexers.Yamux is disabled even tho it is the only multiplexer available")
+	}
+
+	return libp2p.Muxer(yamux.ID, yamuxTransport()), nil
 }
 
 func SmuxTransport(tptConfig config.Transports) func() (opts Libp2pOpts, err error) {

docs/changelogs/v0.23.md

@@ -6,14 +6,23 @@
 
 - [Overview](#overview)
 - [🔦 Highlights](#-highlights)
+  - [Mplex removal](#mplex-removal)
 - [📝 Changelog](#-changelog)
 - [👨‍👩‍👧‍👦 Contributors](#-contributors)
 
 ### Overview
 
 ### 🔦 Highlights
 
+#### Mplex removal
+
+Support for Mplex was removed, this is because it is unreliable and would
+randomly drop streams when sending data too fast.
+
+New pieces of code rely on backpressure, that means the stream will dynamicaly
+slow down if the sending rate if data is getting backed up.
+Backpressure is provided by Yamux and QUIC.
+
 ### 📝 Changelog
 
 ### 👨‍👩‍👧‍👦 Contributors
-

docs/config.md

@@ -2052,6 +2052,8 @@ Type: `flag`
 Configuration section for libp2p _security_ transports. Transports enabled in
 this section will be used to secure unencrypted connections.
 
+This does not concern all the QUIC transports which use QUIC's builtin encryption.
+
 Security transports are configured with the `priority` type.
 
 When establishing an _outbound_ connection, Kubo will try each security
@@ -2094,11 +2096,13 @@ Type: `priority`
 Configuration section for libp2p _multiplexer_ transports. Transports enabled in
 this section will be used to multiplex duplex connections.
 
-Multiplexer transports are secured the same way security transports are, with
+This does not concern all the QUIC transports which use QUIC's builtin muxing.
+
+Multiplexer transports are configured the same way security transports are, with
 the `priority` type. Like with security transports, the initiator gets their
 first choice.
 
-Supported transports are: Yamux (priority 100) and Mplex (priority 200)
+Supported transport is only: Yamux (priority 100)
 
 No default priority will ever be less than 100.
 
@@ -2112,21 +2116,9 @@ Type: `priority`
 
 ### `Swarm.Transports.Multiplexers.Mplex`
 
-Mplex is the default multiplexer used when communicating between Kubo and all
-other IPFS and libp2p implementations. Unlike Yamux:
-
-* Mplex is a simpler protocol.
-* Mplex is more efficient.
-* Mplex does not have built-in keepalives.
-* Mplex does not support backpressure. Unfortunately, this means that, if a
-  single stream to a peer gets backed up for a period of time, the mplex
-  transport will kill the stream to allow the others to proceed. On the other
-  hand, the lack of backpressure means mplex can be significantly faster on some
-  high-latency connections.
+**DEPRECATED**: See https://github.com/ipfs/kubo/issues/9958
 
-Default: `200`
-
-Type: `priority`
+Support for Mplex has been removed. Please remove this option from your config.
 
 ## `DNS`
 

docs/examples/kubo-as-a-library/go.mod

@@ -110,7 +110,6 @@ require (
 	github.com/libp2p/go-libp2p-record v0.2.0 // indirect
 	github.com/libp2p/go-libp2p-routing-helpers v0.7.1 // indirect
 	github.com/libp2p/go-libp2p-xor v0.1.0 // indirect
-	github.com/libp2p/go-mplex v0.7.0 // indirect
 	github.com/libp2p/go-msgio v0.3.0 // indirect
 	github.com/libp2p/go-nat v0.2.0 // indirect
 	github.com/libp2p/go-netroute v0.2.1 // indirect

docs/examples/kubo-as-a-library/go.sum

@@ -482,8 +482,6 @@ github.com/libp2p/go-libp2p-routing-helpers v0.7.1/go.mod h1:cHStPSRC/wgbfpb5jYd
 github.com/libp2p/go-libp2p-testing v0.12.0 h1:EPvBb4kKMWO29qP4mZGyhVzUyR25dvfUIK5WDu6iPUA=
 github.com/libp2p/go-libp2p-xor v0.1.0 h1:hhQwT4uGrBcuAkUGXADuPltalOdpf9aag9kaYNT2tLA=
 github.com/libp2p/go-libp2p-xor v0.1.0/go.mod h1:LSTM5yRnjGZbWNTA/hRwq2gGFrvRIbQJscoIL/u6InY=
-github.com/libp2p/go-mplex v0.7.0 h1:BDhFZdlk5tbr0oyFq/xv/NPGfjbnrsDam1EvutpBDbY=
-github.com/libp2p/go-mplex v0.7.0/go.mod h1:rW8ThnRcYWft/Jb2jeORBmPd6xuG3dGxWN/W168L9EU=
 github.com/libp2p/go-msgio v0.0.4/go.mod h1:63lBBgOTDKQL6EWazRMCwXsEeEeK9O2Cd+0+6OOuipQ=
 github.com/libp2p/go-msgio v0.3.0 h1:mf3Z8B1xcFN314sWX+2vOTShIE0Mmn2TXn3YCUQGNj0=
 github.com/libp2p/go-msgio v0.3.0/go.mod h1:nyRM819GmVaF9LX3l03RMh10QdOroF++NBbxAb0mmDM=

go.mod

@@ -158,7 +158,6 @@ require (
 	github.com/libp2p/go-libp2p-asn-util v0.3.0 // indirect
 	github.com/libp2p/go-libp2p-gostream v0.6.0 // indirect
 	github.com/libp2p/go-libp2p-xor v0.1.0 // indirect
-	github.com/libp2p/go-mplex v0.7.0 // indirect
 	github.com/libp2p/go-msgio v0.3.0 // indirect
 	github.com/libp2p/go-nat v0.2.0 // indirect
 	github.com/libp2p/go-netroute v0.2.1 // indirect

go.sum

@@ -545,8 +545,6 @@ github.com/libp2p/go-libp2p-testing v0.12.0 h1:EPvBb4kKMWO29qP4mZGyhVzUyR25dvfUI
 github.com/libp2p/go-libp2p-testing v0.12.0/go.mod h1:KcGDRXyN7sQCllucn1cOOS+Dmm7ujhfEyXQL5lvkcPg=
 github.com/libp2p/go-libp2p-xor v0.1.0 h1:hhQwT4uGrBcuAkUGXADuPltalOdpf9aag9kaYNT2tLA=
 github.com/libp2p/go-libp2p-xor v0.1.0/go.mod h1:LSTM5yRnjGZbWNTA/hRwq2gGFrvRIbQJscoIL/u6InY=
-github.com/libp2p/go-mplex v0.7.0 h1:BDhFZdlk5tbr0oyFq/xv/NPGfjbnrsDam1EvutpBDbY=
-github.com/libp2p/go-mplex v0.7.0/go.mod h1:rW8ThnRcYWft/Jb2jeORBmPd6xuG3dGxWN/W168L9EU=
 github.com/libp2p/go-msgio v0.0.4/go.mod h1:63lBBgOTDKQL6EWazRMCwXsEeEeK9O2Cd+0+6OOuipQ=
 github.com/libp2p/go-msgio v0.3.0 h1:mf3Z8B1xcFN314sWX+2vOTShIE0Mmn2TXn3YCUQGNj0=
 github.com/libp2p/go-msgio v0.3.0/go.mod h1:nyRM819GmVaF9LX3l03RMh10QdOroF++NBbxAb0mmDM=

test/cli/transports_test.go

@@ -71,18 +71,6 @@ func TestTransports(t *testing.T) {
 		runTests(nodes)
 	})
 
-	t.Run("tcp with mplex", func(t *testing.T) {
-		t.Parallel()
-		nodes := tcpNodes(t)
-		nodes.ForEachPar(func(n *harness.Node) {
-			n.UpdateConfig(func(cfg *config.Config) {
-				cfg.Swarm.Transports.Multiplexers.Yamux = config.Disabled
-			})
-		})
-		nodes.StartDaemons().Connect()
-		runTests(nodes)
-	})
-
 	t.Run("tcp with NOISE", func(t *testing.T) {
 		t.Parallel()
 		nodes := tcpNodes(t)