feat: allow users to optin again into mplex

This is a partial revert of 7220409394.

Closes #9958

config/swarm.go

@@ -122,7 +122,7 @@ type Transports struct {
 	Multiplexers struct {
 		// Defaults to 100.
 		Yamux Priority `json:",omitempty"`
-		// Defaults to 200.
+		// Defaults to -1.
 		Mplex Priority `json:",omitempty"`
 	}
 }

core/node/libp2p/smux.go

@@ -3,35 +3,52 @@ 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"
 )
 
-func yamuxTransport() network.Multiplexer {
-	tpt := *yamux.DefaultTransport
-	tpt.AcceptBacklog = 512
-	if os.Getenv("YAMUX_DEBUG") != "" {
-		tpt.LogOutput = os.Stderr
-	}
-	return &tpt
-}
-
 func makeSmuxTransportOption(tptConfig config.Transports) (libp2p.Option, error) {
 	if prefs := os.Getenv("LIBP2P_MUX_PREFS"); prefs != "" {
-		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")
-	}
+		// 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))
 
-	return libp2p.Muxer(yamux.ID, yamuxTransport()), nil
+		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 yamux.ID:
+				opts = append(opts, libp2p.Muxer(tpt, yamux.DefaultTransport))
+			case mplex.ID:
+				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(yamux.ID, yamux.DefaultTransport),
+		}, {
+			priority:        tptConfig.Multiplexers.Mplex,
+			defaultPriority: config.Disabled,
+			opt:             libp2p.Muxer(mplex.ID, mplex.DefaultTransport),
+		}}), nil
+	}
 }
 
 func SmuxTransport(tptConfig config.Transports) func() (opts Libp2pOpts, err error) {

docs/changelogs/v0.23.md

@@ -6,7 +6,7 @@
 
 - [Overview](#overview)
 - [🔦 Highlights](#-highlights)
-  - [Mplex removal](#mplex-removal)
+  - [Mplex deprecation](#mplex-deprecation)
 - [📝 Changelog](#-changelog)
 - [👨‍👩‍👧‍👦 Contributors](#-contributors)
 
@@ -14,14 +14,23 @@
 
 ### 🔦 Highlights
 
-#### Mplex removal
+#### Mplex deprecation
 
-Support for Mplex was removed, this is because it is unreliable and would
-randomly drop streams when sending data too fast.
+Mplex is being deprecated, this is because it is unreliable and
+randomly drop streams when sending data *too fast*.
 
 New pieces of code rely on backpressure, that means the stream will dynamicaly
 slow down the sending rate if data is getting backed up.
-Backpressure is provided by Yamux and QUIC.
+Backpressure is provided by **Yamux** and **QUIC**.
+
+In case you need compatibility with older implementations that do not ship with
+Yamux (like default's JS-IPFS) you can turned it back ON in the config with:
+```console
+$ ipfs config --json Swarm.Transports.Multiplexers.Mplex 200
+```
+
+We will completely remove Mplex in v0.24 as it makes protocols very bad to implement,
+if you are in this situation you need to add yamux support to your other implementation.
 
 ### 📝 Changelog
 

docs/config.md

@@ -2118,7 +2118,19 @@ Type: `priority`
 
 **DEPRECATED**: See https://github.com/ipfs/kubo/issues/9958
 
-Support for Mplex has been removed. Please remove this option from your config.
+Mplex is deprecated, this is because it is unreliable and
+randomly drop streams when sending data *too fast*.
+
+New pieces of code rely on backpressure, that means the stream will dynamicaly
+slow down the sending rate if data is getting backed up.
+Backpressure is provided by **Yamux** and **QUIC**.
+
+If you want to turn it back on make sure to have a higher (lower is better)
+priority than `Yamux`, you don't want your Kubo to start defaulting to Mplex.
+
+Default: `200`
+
+Type: `priority`
 
 ## `DNS`
 

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

@@ -110,6 +110,7 @@ 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

@@ -482,6 +482,8 @@ 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

@@ -158,6 +158,7 @@ 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

@@ -545,6 +545,8 @@ 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

@@ -71,6 +71,20 @@ func TestTransports(t *testing.T) {
 		runTests(nodes)
 	})
 
+	t.Run("tcp with mplex", func(t *testing.T) {
+		// FIXME(#10069): we don't want this to exists anymore
+		t.Parallel()
+		nodes := tcpNodes(t)
+		nodes.ForEachPar(func(n *harness.Node) {
+			n.UpdateConfig(func(cfg *config.Config) {
+				cfg.Swarm.Transports.Multiplexers.Yamux = config.Disabled
+				cfg.Swarm.Transports.Multiplexers.Mplex = 200
+			})
+		})
+		nodes.StartDaemons().Connect()
+		runTests(nodes)
+	})
+
 	t.Run("tcp with NOISE", func(t *testing.T) {
 		t.Parallel()
 		nodes := tcpNodes(t)