Tie the NFSv4.1 server into the virtual file system mounting code

Add a 'minorVersion' configuration option that can be used to explicitly
choose between NFSv4.0 or NFSv4.1. Default to NFSv4.0, because that's
what macOS supports.

pkg/filesystem/virtual/configuration/configuration.go

@@ -44,10 +44,18 @@ type nfsv4Mount struct {
 }
 
 func (m *nfsv4Mount) Expose(terminationGroup program.Group, rootDirectory virtual.Directory) error {
-	// Random values that the client can use to detect that the
-	// server has been restarted and lost all state.
-	var verifier nfsv4_xdr.Verifier4
-	random.FastThreadSafeGenerator.Read(verifier[:])
+	// Random values that the client can use to identify the server, or
+	// detect that the server has been restarted and lost all state.
+	var soMajorID [8]byte
+	random.FastThreadSafeGenerator.Read(soMajorID[:])
+	serverOwner := nfsv4_xdr.ServerOwner4{
+		SoMinorId: random.FastThreadSafeGenerator.Uint64(),
+		SoMajorId: soMajorID[:],
+	}
+	var serverScope [8]byte
+	random.FastThreadSafeGenerator.Read(serverScope[:])
+	var rebootVerifier nfsv4_xdr.Verifier4
+	random.FastThreadSafeGenerator.Read(rebootVerifier[:])
 	var stateIDOtherPrefix [4]byte
 	random.FastThreadSafeGenerator.Read(stateIDOtherPrefix[:])
 
@@ -60,22 +68,64 @@ func (m *nfsv4Mount) Expose(terminationGroup program.Group, rootDirectory virtua
 		return util.StatusWrap(err, "Invalid announced lease time")
 	}
 
+	var minorVersion uint32
+	if msg := m.configuration.MinorVersion; msg != nil {
+		minorVersion = msg.Value
+	} else {
+		var err error
+		minorVersion, err = getLatestSupportedNFSv4MinorVersion()
+		if err != nil {
+			return util.StatusWrap(err, "Unable to determine the latest minor version of NFSv4 supported by the operating system")
+		}
+	}
+
+	var program nfsv4_xdr.Nfs4Program
+	switch minorVersion {
+	case 0:
+		// Use NFSv4.0 (RFC 7530).
+		program = nfsv4.NewNFS40Program(
+			rootDirectory,
+			m.handleAllocator.ResolveHandle,
+			random.NewFastSingleThreadedGenerator(),
+			rebootVerifier,
+			stateIDOtherPrefix,
+			clock.SystemClock,
+			enforcedLeaseTime.AsDuration(),
+			announcedLeaseTime.AsDuration(),
+		)
+	case 1:
+		// Use NFSv4.1 (RFC 8881).
+		program = nfsv4.NewNFS41Program(
+			rootDirectory,
+			m.handleAllocator.ResolveHandle,
+			serverOwner,
+			serverScope[:],
+			// TODO: Should any of these parameters be configurable?
+			&nfsv4_xdr.ChannelAttrs4{
+				CaMaxrequestsize:        2 * 1024 * 1024,
+				CaMaxresponsesize:       2 * 1024 * 1024,
+				CaMaxresponsesizeCached: 64 * 1024,
+				CaMaxoperations:         1000,
+				CaMaxrequests:           100,
+			},
+			random.NewFastSingleThreadedGenerator(),
+			rebootVerifier,
+			clock.SystemClock,
+			enforcedLeaseTime.AsDuration(),
+			announcedLeaseTime.AsDuration(),
+		)
+	default:
+		return status.Errorf(codes.Unimplemented, "Unsupported NFSv4 minor version: %d", minorVersion)
+	}
+
 	// Create an RPC server that offers the NFSv4 program.
 	rpcServer := rpcserver.NewServer(map[uint32]rpcserver.Service{
 		nfsv4_xdr.NFS4_PROGRAM_PROGRAM_NUMBER: nfsv4_xdr.NewNfs4ProgramService(
-			nfsv4.NewMetricsProgram(
-				nfsv4.NewNFS40Program(
-					rootDirectory,
-					m.handleAllocator.ResolveHandle,
-					random.NewFastSingleThreadedGenerator(),
-					verifier,
-					stateIDOtherPrefix,
-					clock.SystemClock,
-					enforcedLeaseTime.AsDuration(),
-					announcedLeaseTime.AsDuration()))),
+			nfsv4.NewMetricsProgram(program),
+		),
 	}, m.authenticator)
 
-	return m.mount(terminationGroup, rpcServer)
+	return m.mount(terminationGroup, rpcServer, minorVersion)
 }
 
 // NewMountFromConfiguration creates a new FUSE mount based on options

pkg/filesystem/virtual/configuration/nfsv4_mount_darwin.go

@@ -85,7 +85,12 @@ func (bv macOSBuildVersion) greaterEqual(major int64, minor byte, daily int64) b
 	return bv.major > major || (bv.major == major && (bv.minor > minor || (bv.minor == minor && bv.daily >= daily)))
 }
 
-func (m *nfsv4Mount) mount(terminationGroup program.Group, rpcServer *rpcserver.Server) error {
+func getLatestSupportedNFSv4MinorVersion() (uint32, error) {
+	// macOS only supports NFSv4.0.
+	return 0, nil
+}
+
+func (m *nfsv4Mount) mount(terminationGroup program.Group, rpcServer *rpcserver.Server, minorVersion uint32) error {
 	// Extract the version of macOS used. We need to know this, as
 	// it determines which mount options are supported.
 	buildVersion, err := getMacOSBuildVersion()
@@ -159,11 +164,11 @@ func (m *nfsv4Mount) mount(terminationGroup program.Group, rpcServer *rpcserver.
 	}
 	flags.WriteTo(&attrVals)
 
-	// Explicitly request the use of NFSv4.0.
+	// Request the use of the desired NFSv4 protocol minor version.
 	attrMask[0] |= 1 << nfs_sys_prot.NFS_MATTR_NFS_VERSION
 	nfs_sys_prot.WriteNfsMattrNfsVersion(&attrVals, 4)
 	attrMask[0] |= 1 << nfs_sys_prot.NFS_MATTR_NFS_MINOR_VERSION
-	nfs_sys_prot.WriteNfsMattrNfsMinorVersion(&attrVals, 0)
+	nfs_sys_prot.WriteNfsMattrNfsMinorVersion(&attrVals, minorVersion)
 
 	// Set attribute caching durations. This needs to be set at
 	// mount time, as NFSv4 provides no facilities for conveying

pkg/filesystem/virtual/configuration/nfsv4_mount_disabled.go

@@ -11,6 +11,10 @@ import (
 	"google.golang.org/grpc/status"
 )
 
-func (m *nfsv4Mount) mount(terminationGroup program.Group, rpcServer *rpcserver.Server) error {
+func getLatestSupportedNFSv4MinorVersion() (uint32, error) {
+	return 0, nil
+}
+
+func (m *nfsv4Mount) mount(terminationGroup program.Group, rpcServer *rpcserver.Server, minorVersion uint32) error {
 	return status.Error(codes.Unimplemented, "NFSv4 is not supported on this platform")
 }

pkg/proto/configuration/filesystem/virtual/BUILD.bazel

@@ -9,6 +9,7 @@ proto_library(
     deps = [
         "@com_github_buildbarn_bb_storage//pkg/proto/configuration/eviction:eviction_proto",
         "@protobuf//:duration_proto",
+        "@protobuf//:wrappers_proto",
     ],
 )
 

pkg/proto/configuration/filesystem/virtual/virtual.proto

@@ -3,6 +3,7 @@ syntax = "proto3";
 package buildbarn.configuration.filesystem.virtual;
 
 import "google/protobuf/duration.proto";
+import "google/protobuf/wrappers.proto";
 import "pkg/proto/configuration/eviction/eviction.proto";
 
 option go_package = "github.com/buildbarn/bb-remote-execution/pkg/proto/configuration/filesystem/virtual";
@@ -24,11 +25,6 @@ message MountConfiguration {
     // to expose the mount. This option is supported on macOS starting
     // with Ventura 13.3 (22E252), though the use of Sonoma 14.5
     // (23F79) or later is strongly recommended.
-    //
-    // The NFS server is expected to conform to NFSv4.0 (RFC 7530).
-    // Features provided by newer versions of the protocol, such as
-    // NFSv4.1 (RFC 8881) and NFSv4.2 (RFC 7862), are not supported at
-    // this time. macOS also does not support the latter.
     NFSv4MountConfiguration nfsv4 = 3;
   }
 }
@@ -170,6 +166,18 @@ message NFSv4MountConfiguration {
   //
   // NOTE: This option is only used by bb_virtual_tmp.
   RPCv2SystemAuthenticationConfiguration system_authentication = 4;
+
+  // The minor version of the protocol to use.
+  //
+  // When set to 0, the NFS server is expected to conform to NFSv4.0
+  // (RFC 7530). When set to 1, the NFS server is expected to conform to
+  // NFSv4.1 (RFC 8881). The use of NFSv4.1 is recommended, because it
+  // provides better parallelism.
+  //
+  // When left unset, the latest protocol version is used that is
+  // supported by the currently running operating system. In the case of
+  // macOS, this is NFSv4.0.
+  google.protobuf.UInt32Value minor_version = 5;
 }
 
 message NFSv4DarwinMountConfiguration {