[lisa] lisafs package POC.

This change mainly aims to define the semantics of communication for the LISAFS
(LInux SAndbox Filesystem) protocol. This protocol aims to replace 9P and
intends to bring some performance benefits with it.

Some of the notable differences from the p9 package are:
- Now the server implementations own the handlers.
- As a result, there is no verbose interface like `p9.File` that all servers
  need to implement. Different implementations can extend their File
  implementations to varying degrees without imposing those extensions to other
  server implementations that might not have anything to do with those features.
- If a server implementation adds a new RPC message, other implementations are
  not compelled to support it.

I wrote a benchmark `BenchmarkSendRecv` in connection_test.go which competes
with p9's `BenchmarkSendRecvChannel`. Running these on an AMD Milan machine
shows that lisafs is **45%** faster.

**With 9P**
goos: linux
goarch: amd64
pkg: gvisor/pkg/p9/p9
cpu: AMD EPYC 7B13 64-Core Processor
BenchmarkSendRecvLegacy-256     82830     14053 ns/op     633 B/op     23 allocs/op
BenchmarkSendRecvChannel-256     776971     1551 ns/op     184 B/op     6 allocs/op

**With lisafs**
goos: linux
goarch: amd64
pkg: pkg/lisafs/connection_test
cpu: AMD EPYC 7B13 64-Core Processor
BenchmarkSendRecv-256     1399610     853.5 ns/op     48 B/op     2 allocs/op

Fixes #5464

PiperOrigin-RevId: 397803163

1 files changed, 217 insertions, 0 deletions

diff --git a/pkg/lisafs/sock_test.go b/pkg/lisafs/sock_test.go
new file mode 100644
index 000000000..387f4b7a8
--- /dev/null
+++ b/pkg/lisafs/sock_test.go
@@ -0,0 +1,217 @@
+// Copyright 2021 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package lisafs
+
+import (
+	"bytes"
+	"math/rand"
+	"reflect"
+	"testing"
+
+	"golang.org/x/sys/unix"
+	"gvisor.dev/gvisor/pkg/marshal"
+	"gvisor.dev/gvisor/pkg/sync"
+	"gvisor.dev/gvisor/pkg/unet"
+)
+
+func runSocketTest(t *testing.T, fun1 func(*sockCommunicator), fun2 func(*sockCommunicator)) {
+	sock1, sock2, err := unet.SocketPair(false)
+	if err != nil {
+		t.Fatalf("socketpair got err %v expected nil", err)
+	}
+	defer sock1.Close()
+	defer sock2.Close()
+
+	var testWg sync.WaitGroup
+	testWg.Add(2)
+
+	go func() {
+		fun1(newSockComm(sock1))
+		testWg.Done()
+	}()
+
+	go func() {
+		fun2(newSockComm(sock2))
+		testWg.Done()
+	}()
+
+	testWg.Wait()
+}
+
+func TestReadWrite(t *testing.T) {
+	// Create random data to send.
+	n := 10000
+	data := make([]byte, n)
+	if _, err := rand.Read(data); err != nil {
+		t.Fatalf("rand.Read(data) failed: %v", err)
+	}
+
+	runSocketTest(t, func(comm *sockCommunicator) {
+		// Scatter that data into two parts using Iovecs while sending.
+		mid := n / 2
+		if err := writeTo(comm.sock, [][]byte{data[:mid], data[mid:]}, n, nil); err != nil {
+			t.Errorf("writeTo socket failed: %v", err)
+		}
+	}, func(comm *sockCommunicator) {
+		gotData := make([]byte, n)
+		if _, err := readFrom(comm.sock, gotData, 0); err != nil {
+			t.Fatalf("reading from socket failed: %v", err)
+		}
+
+		// Make sure we got the right data.
+		if res := bytes.Compare(data, gotData); res != 0 {
+			t.Errorf("data received differs from data sent, want = %v, got = %v", data, gotData)
+		}
+	})
+}
+
+func TestFDDonation(t *testing.T) {
+	n := 10
+	data := make([]byte, n)
+	if _, err := rand.Read(data); err != nil {
+		t.Fatalf("rand.Read(data) failed: %v", err)
+	}
+
+	// Try donating FDs to these files.
+	path1 := "/dev/null"
+	path2 := "/dev"
+	path3 := "/dev/random"
+
+	runSocketTest(t, func(comm *sockCommunicator) {
+		devNullFD, err := unix.Open(path1, unix.O_RDONLY, 0)
+		defer unix.Close(devNullFD)
+		if err != nil {
+			t.Fatalf("open(%s) failed: %v", path1, err)
+		}
+		devFD, err := unix.Open(path2, unix.O_RDONLY, 0)
+		defer unix.Close(devFD)
+		if err != nil {
+			t.Fatalf("open(%s) failed: %v", path2, err)
+		}
+		devRandomFD, err := unix.Open(path3, unix.O_RDONLY, 0)
+		defer unix.Close(devRandomFD)
+		if err != nil {
+			t.Fatalf("open(%s) failed: %v", path2, err)
+		}
+		if err := writeTo(comm.sock, [][]byte{data}, n, []int{devNullFD, devFD, devRandomFD}); err != nil {
+			t.Errorf("writeTo socket failed: %v", err)
+		}
+	}, func(comm *sockCommunicator) {
+		gotData := make([]byte, n)
+		fds, err := readFrom(comm.sock, gotData, 3)
+		if err != nil {
+			t.Fatalf("reading from socket failed: %v", err)
+		}
+		defer closeFDs(fds[:])
+
+		if res := bytes.Compare(data, gotData); res != 0 {
+			t.Errorf("data received differs from data sent, want = %v, got = %v", data, gotData)
+		}
+
+		if len(fds) != 3 {
+			t.Fatalf("wanted 3 FD, got %d", len(fds))
+		}
+
+		// Check that the FDs actually point to the correct file.
+		compareFDWithFile(t, fds[0], path1)
+		compareFDWithFile(t, fds[1], path2)
+		compareFDWithFile(t, fds[2], path3)
+	})
+}
+
+func compareFDWithFile(t *testing.T, fd int, path string) {
+	var want unix.Stat_t
+	if err := unix.Stat(path, &want); err != nil {
+		t.Fatalf("stat(%s) failed: %v", path, err)
+	}
+
+	var got unix.Stat_t
+	if err := unix.Fstat(fd, &got); err != nil {
+		t.Fatalf("fstat on donated FD failed: %v", err)
+	}
+
+	if got.Ino != want.Ino || got.Dev != want.Dev {
+		t.Errorf("FD does not point to %s, want = %+v, got = %+v", path, want, got)
+	}
+}
+
+func testSndMsg(comm *sockCommunicator, m MID, msg marshal.Marshallable) error {
+	var payloadLen uint32
+	if msg != nil {
+		payloadLen = uint32(msg.SizeBytes())
+		msg.MarshalUnsafe(comm.PayloadBuf(payloadLen))
+	}
+	return comm.sndPrepopulatedMsg(m, payloadLen, nil)
+}
+
+func TestSndRcvMessage(t *testing.T) {
+	req := &MsgSimple{}
+	req.Randomize()
+	reqM := MID(1)
+
+	// Create a massive random response.
+	var resp MsgDynamic
+	resp.Randomize(100)
+	respM := MID(2)
+
+	runSocketTest(t, func(comm *sockCommunicator) {
+		if err := testSndMsg(comm, reqM, req); err != nil {
+			t.Errorf("writeMessageTo failed: %v", err)
+		}
+		checkMessageReceive(t, comm, respM, &resp)
+	}, func(comm *sockCommunicator) {
+		checkMessageReceive(t, comm, reqM, req)
+		if err := testSndMsg(comm, respM, &resp); err != nil {
+			t.Errorf("writeMessageTo failed: %v", err)
+		}
+	})
+}
+
+func TestSndRcvMessageNoPayload(t *testing.T) {
+	reqM := MID(1)
+	respM := MID(2)
+	runSocketTest(t, func(comm *sockCommunicator) {
+		if err := testSndMsg(comm, reqM, nil); err != nil {
+			t.Errorf("writeMessageTo failed: %v", err)
+		}
+		checkMessageReceive(t, comm, respM, nil)
+	}, func(comm *sockCommunicator) {
+		checkMessageReceive(t, comm, reqM, nil)
+		if err := testSndMsg(comm, respM, nil); err != nil {
+			t.Errorf("writeMessageTo failed: %v", err)
+		}
+	})
+}
+
+func checkMessageReceive(t *testing.T, comm *sockCommunicator, wantM MID, wantMsg marshal.Marshallable) {
+	gotM, payloadLen, err := comm.rcvMsg(0)
+	if err != nil {
+		t.Fatalf("readMessageFrom failed: %v", err)
+	}
+	if gotM != wantM {
+		t.Errorf("got incorrect message ID: got = %d, want = %d", gotM, wantM)
+	}
+	if wantMsg == nil {
+		if payloadLen != 0 {
+			t.Errorf("no payload expect but got %d bytes", payloadLen)
+		}
+	} else {
+		gotMsg := reflect.New(reflect.ValueOf(wantMsg).Elem().Type()).Interface().(marshal.Marshallable)
+		gotMsg.UnmarshalUnsafe(comm.PayloadBuf(payloadLen))
+		if !reflect.DeepEqual(wantMsg, gotMsg) {
+			t.Errorf("msg differs: want = %+v, got = %+v", wantMsg, gotMsg)
+		}
+	}
+}