wasi: non-blocking i/o on files on *nix (#1502)

Signed-off-by: Edoardo Vacchi <evacchi@users.noreply.github.com>

imports/wasi_snapshot_preview1/fs.go

@@ -310,17 +310,20 @@ func fdFdstatSetFlagsFn(_ context.Context, mod api.Module, params []uint64) sysc
 
 	if f, ok := fsc.LookupFile(fd); !ok {
 		return syscall.EBADF
-	} else if isPreopenedStdio(fd, f) {
-		nonblock := wasip1.FD_NONBLOCK&wasiFlag != 0
-		return f.File.SetNonblock(nonblock)
-	} else if _, ok := f.File.(socketapi.TCPConn); ok {
-		nonblock := wasip1.FD_NONBLOCK&wasiFlag != 0
-		return f.File.SetNonblock(nonblock)
 	} else {
-		// For normal files, proceed to apply an append flag.
-		append := wasip1.FD_APPEND&wasiFlag != 0
-		return f.File.SetAppend(append)
+		nonblock := wasip1.FD_NONBLOCK&wasiFlag != 0
+		errno := f.File.SetNonblock(nonblock)
+		if errno != 0 {
+			return errno
+		}
+		if stat, err := f.File.Stat(); err == 0 && stat.Mode.IsRegular() {
+			// For normal files, proceed to apply an append flag.
+			append := wasip1.FD_APPEND&wasiFlag != 0
+			return f.File.SetAppend(append)
+		}
 	}
+
+	return 0
 }
 
 // fdFdstatSetRights will not be implemented as rights were removed from WASI.
@@ -1691,6 +1694,9 @@ func openFlags(dirflags, oflags, fdflags uint16, rights uint32) (openFlags int)
 		openFlags |= syscall.O_CREAT
 		defaultMode = syscall.O_RDWR
 	}
+	if fdflags&wasip1.FD_NONBLOCK != 0 {
+		openFlags |= syscall.O_NONBLOCK
+	}
 	if fdflags&wasip1.FD_APPEND != 0 {
 		openFlags |= syscall.O_APPEND
 		defaultMode = syscall.O_RDWR

imports/wasi_snapshot_preview1/testdata/zig-cc/wasi.c

@@ -162,6 +162,25 @@ void main_sock() {
   }
 }
 
+void main_nonblock(char* fpath) {
+  struct timespec tim, tim2;
+  tim.tv_sec = 0;
+  tim.tv_nsec = 200 * 1000000;
+  int fd = open(fpath, O_RDONLY | O_NONBLOCK);
+  char buf[32];
+  ssize_t newLen = 0;
+  while (newLen == 0) {
+    newLen = read(fd, buf, sizeof(buf));
+    if (errno == EAGAIN || newLen == 0) {
+      printf(".");
+      nanosleep(&tim , &tim2) ;
+      continue;
+    }
+  }
+  printf("\n%s\n", buf);
+  close(fd);
+}
+
 int main(int argc, char** argv) {
   if (strcmp(argv[1],"ls")==0) {
     bool repeat = false;
@@ -193,6 +212,8 @@ int main(int argc, char** argv) {
     main_open_wronly();
   } else if (strcmp(argv[1],"sock")==0) {
     main_sock();
+  } else if (strcmp(argv[1],"nonblock")==0) {
+    main_nonblock(argv[2]);
   } else {
     fprintf(stderr, "unknown command: %s\n", argv[1]);
     return 1;

imports/wasi_snapshot_preview1/wasi_stdlib_unix_test.go

@@ -0,0 +1,47 @@
+//go:build unix || linux || darwin
+
+package wasi_snapshot_preview1_test
+
+import (
+	"os"
+	"strings"
+	"syscall"
+	"testing"
+	"time"
+
+	"github.com/tetratelabs/wazero"
+	"github.com/tetratelabs/wazero/internal/testing/require"
+)
+
+func Test_Nonblock(t *testing.T) {
+	const fifo = "/test-fifo"
+	tempDir := t.TempDir()
+	fifoAbsPath := tempDir + fifo
+
+	moduleConfig := wazero.NewModuleConfig().
+		WithArgs("wasi", "nonblock", fifo).
+		WithFSConfig(wazero.NewFSConfig().WithDirMount(tempDir, "/")).
+		WithSysNanosleep()
+
+	err := syscall.Mkfifo(fifoAbsPath, 0o666)
+	require.NoError(t, err)
+
+	ch := make(chan string, 1)
+	go func() { ch <- compileAndRun(t, testCtx, moduleConfig, wasmZigCc) }()
+
+	// The test writes a few dots on the console until the pipe has data ready for reading,
+	// so we wait for a little to ensure those dots are printed.
+	time.Sleep(500 * time.Millisecond)
+
+	f, err := os.OpenFile(fifoAbsPath, os.O_APPEND|os.O_WRONLY, 0)
+	require.NoError(t, err)
+	n, err := f.Write([]byte("wazero"))
+	require.NoError(t, err)
+	require.NotEqual(t, 0, n)
+	console := <-ch
+	lines := strings.Split(console, "\n")
+
+	// Check if the first line starts with at least one dot.
+	require.True(t, strings.HasPrefix(lines[0], "."))
+	require.Equal(t, "wazero", lines[1])
+}