unix: implement recvmsgRaw and sendmsgN on aix

This allows using RecvmsgBuffers and SendmsgBuffers on aix in x/net.

For golang/go#54099

Change-Id: Ib21c59244c9d74b826f4fc8ba3314e3602fd9a8a
Reviewed-on: https://go-review.googlesource.com/c/sys/+/419396
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

unix/syscall_aix.go

@@ -218,13 +218,62 @@ func Accept(fd int) (nfd int, sa Sockaddr, err error) {
 }
 
 func recvmsgRaw(fd int, iov []Iovec, oob []byte, flags int, rsa *RawSockaddrAny) (n, oobn int, recvflags int, err error) {
-	// Recvmsg not implemented on AIX
+	var msg Msghdr
-	return -1, -1, -1, ENOSYS
+	msg.Name = (*byte)(unsafe.Pointer(rsa))
+	msg.Namelen = uint32(SizeofSockaddrAny)
+	var dummy byte
+	if len(oob) > 0 {
+		// receive at least one normal byte
+		if emptyIovecs(iov) {
+			var iova [1]Iovec
+			iova[0].Base = &dummy
+			iova[0].SetLen(1)
+			iov = iova[:]
+		}
+		msg.Control = (*byte)(unsafe.Pointer(&oob[0]))
+		msg.SetControllen(len(oob))
+	}
+	if len(iov) > 0 {
+		msg.Iov = &iov[0]
+		msg.SetIovlen(len(iov))
+	}
+	if n, err = recvmsg(fd, &msg, flags); n == -1 {
+		return
+	}
+	oobn = int(msg.Controllen)
+	recvflags = int(msg.Flags)
+	return
 }
 
 func sendmsgN(fd int, iov []Iovec, oob []byte, ptr unsafe.Pointer, salen _Socklen, flags int) (n int, err error) {
-	// SendmsgN not implemented on AIX
+	var msg Msghdr
-	return -1, ENOSYS
+	msg.Name = (*byte)(unsafe.Pointer(ptr))
+	msg.Namelen = uint32(salen)
+	var dummy byte
+	var empty bool
+	if len(oob) > 0 {
+		// send at least one normal byte
+		empty := emptyIovecs(iov)
+		if empty {
+			var iova [1]Iovec
+			iova[0].Base = &dummy
+			iova[0].SetLen(1)
+			iov = iova[:]
+		}
+		msg.Control = (*byte)(unsafe.Pointer(&oob[0]))
+		msg.SetControllen(len(oob))
+	}
+	if len(iov) > 0 {
+		msg.Iov = &iov[0]
+		msg.SetIovlen(len(iov))
+	}
+	if n, err = sendmsg(fd, &msg, flags); err != nil {
+		return 0, err
+	}
+	if len(oob) > 0 && empty {
+		n = 0
+	}
+	return n, nil
 }
 
 func anyToSockaddr(fd int, rsa *RawSockaddrAny) (Sockaddr, error) {

unix/syscall_unix_test.go

@@ -957,10 +957,6 @@ func TestSend(t *testing.T) {
 }
 
 func TestSendmsgBuffers(t *testing.T) {
-	if runtime.GOOS == "aix" {
-		t.Skipf("SendmsgBuffers not supported on %s", runtime.GOOS)
-	}
-
 	fds, err := unix.Socketpair(unix.AF_LOCAL, unix.SOCK_STREAM, 0)
 	if err != nil {
 		t.Fatal(err)