Revert "net: in (*netFD).dial, use the passed in local address if getsockname fails"

This reverts CL 366536

Reason for revert: may have caused #50033 due to an invalid or partially-populated *TCPAddr

Fixes #50033

Change-Id: Ia29ca4116503dba65d56e89caa46ba1c848d421a
Reviewed-on: https://go-review.googlesource.com/c/go/+/369982
Trust: Bryan Mills <bcmills@google.com>
Run-TryBot: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Author: Bryan Mills

src/net/server_test.go

@@ -200,17 +200,9 @@ func TestUnixAndUnixpacketServer(t *testing.T) {
 				if c == nil {
 					panic("Dial returned a nil Conn")
 				}
-				rc := reflect.ValueOf(c)
-				if rc.IsNil() {
+				if rc := reflect.ValueOf(c); rc.Kind() == reflect.Pointer && rc.IsNil() {
 					panic(fmt.Sprintf("Dial returned a nil %T", c))
 				}
-				fd := rc.Elem().FieldByName("fd")
-				if fd.IsNil() {
-					panic(fmt.Sprintf("Dial returned a %T with a nil fd", c))
-				}
-				if addr := fd.Elem().FieldByName("laddr"); addr.IsNil() {
-					panic(fmt.Sprintf("Dial returned a %T whose fd has a nil laddr", c))
-				}
 				addr := c.LocalAddr()
 				if addr == nil {
 					panic(fmt.Sprintf("(%T).LocalAddr returned a nil Addr", c))

src/net/sock_posix.go

@@ -156,24 +156,18 @@ func (fd *netFD) dial(ctx context.Context, laddr, raddr sockaddr, ctrlFn func(st
 		}
 	}
 	// Record the local and remote addresses from the actual socket.
-	// For the local address, use
-	// 1) the one returned by Getsockname, if that succeeds; or
-	// 2) the one passed to us as the laddr parameter; or
-	// 3) nil.
+	// Get the local address by calling Getsockname.
 	// For the remote address, use
 	// 1) the one returned by the connect method, if any; or
 	// 2) the one from Getpeername, if it succeeds; or
 	// 3) the one passed to us as the raddr parameter.
-	var laddrName Addr = laddr
-	if lsa, err := syscall.Getsockname(fd.pfd.Sysfd); err == nil {
-		laddrName = fd.addrFunc()(lsa)
-	}
+	lsa, _ = syscall.Getsockname(fd.pfd.Sysfd)
 	if crsa != nil {
-		fd.setAddr(laddrName, fd.addrFunc()(crsa))
+		fd.setAddr(fd.addrFunc()(lsa), fd.addrFunc()(crsa))
 	} else if rsa, _ = syscall.Getpeername(fd.pfd.Sysfd); rsa != nil {
-		fd.setAddr(laddrName, fd.addrFunc()(rsa))
+		fd.setAddr(fd.addrFunc()(lsa), fd.addrFunc()(rsa))
 	} else {
-		fd.setAddr(laddrName, raddr)
+		fd.setAddr(fd.addrFunc()(lsa), raddr)
 	}
 	return nil
 }