net: ensure net.Addr values match the connection type on wasip1

net.FileListener returns values of type *net.TCPListener, which can be
asserted by the application. The (*net.TCPListener).Addr method
documents that the underlying type of its return value is *net.TCPAddr,
which is fixed by this change.

Change-Id: Ife9906716d1b512092024ba50797bf7831536b75
Reviewed-on: https://go-review.googlesource.com/c/go/+/502335
Reviewed-by: Johan Brandhorst-Satzkorn <johan.brandhorst@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Run-TryBot: Johan Brandhorst-Satzkorn <johan.brandhorst@gmail.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Michael Pratt <mpratt@google.com>

2 files changed, 42 insertions, 2 deletions

diff --git a/src/net/fd_wasip1.go b/src/net/fd_wasip1.go
index a3584e82bd..74d0b0b2e8 100644
--- a/src/net/fd_wasip1.go
+++ b/src/net/fd_wasip1.go
@@ -47,11 +47,31 @@ func newFD(net string, sysfd int) *netFD {
 }
 
 func newPollFD(net string, pfd poll.FD) *netFD {
+	var laddr Addr
+	var raddr Addr
+	// WASI preview 1 does not have functions like getsockname/getpeername,
+	// so we cannot get access to the underlying IP address used by connections.
+	//
+	// However, listeners created by FileListener are of type *TCPListener,
+	// which can be asserted by a Go program. The (*TCPListener).Addr method
+	// documents that the returned value will be of type *TCPAddr, we satisfy
+	// the documented behavior by creating addresses of the expected type here.
+	switch net {
+	case "tcp":
+		laddr = new(TCPAddr)
+		raddr = new(TCPAddr)
+	case "udp":
+		laddr = new(UDPAddr)
+		raddr = new(UDPAddr)
+	default:
+		laddr = unknownAddr{}
+		raddr = unknownAddr{}
+	}
 	return &netFD{
 		pfd:   pfd,
 		net:   net,
-		laddr: unknownAddr{},
-		raddr: unknownAddr{},
+		laddr: laddr,
+		raddr: raddr,
 	}
 }
 
diff --git a/src/net/file_wasip1_test.go b/src/net/file_wasip1_test.go
index 137574090f..4f4259069d 100644
--- a/src/net/file_wasip1_test.go
+++ b/src/net/file_wasip1_test.go
@@ -79,14 +79,34 @@ func TestWasip1FileListenNet(t *testing.T) {
 func TestWasip1NewFileListener(t *testing.T) {
 	if l, ok := newFileListener(newFD("tcp", -1)).(*TCPListener); !ok {
 		t.Errorf("newFileListener: tcp listener type mismatch: %T", l)
+	} else {
+		testIsTCPAddr(t, "Addr", l.Addr())
 	}
 }
 
 func TestWasip1NewFileConn(t *testing.T) {
 	if c, ok := newFileConn(newFD("tcp", -1)).(*TCPConn); !ok {
 		t.Errorf("newFileConn: tcp conn type mismatch: %T", c)
+	} else {
+		testIsTCPAddr(t, "LocalAddr", c.LocalAddr())
+		testIsTCPAddr(t, "RemoteAddr", c.RemoteAddr())
 	}
 	if c, ok := newFileConn(newFD("udp", -1)).(*UDPConn); !ok {
 		t.Errorf("newFileConn: udp conn type mismatch: %T", c)
+	} else {
+		testIsUDPAddr(t, "LocalAddr", c.LocalAddr())
+		testIsUDPAddr(t, "RemoteAddr", c.RemoteAddr())
+	}
+}
+
+func testIsTCPAddr(t *testing.T, method string, addr Addr) {
+	if _, ok := addr.(*TCPAddr); !ok {
+		t.Errorf("%s: returned address is not a *TCPAddr: %T", method, addr)
+	}
+}
+
+func testIsUDPAddr(t *testing.T, method string, addr Addr) {
+	if _, ok := addr.(*UDPAddr); !ok {
+		t.Errorf("%s: returned address is not a *UDPAddr: %T", method, addr)
 	}
 }