From 6fa7a7ca2b54b24eb14a320550b80069e435c366 Mon Sep 17 00:00:00 2001
From: Tobias Klauser <tklauser@distanz.ch>
Date: Wed, 28 Sep 2022 12:47:23 +0200
Subject: [PATCH] windows: allow calling WSASendto with nil Sockaddr

Same as CL 434535 did for the syscall package.

For golang/go#55845

Change-Id: I17f30152ae973b64ac65e08cefd5442e9bf19e2c
Reviewed-on: https://go-review.googlesource.com/c/sys/+/435777
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Benny Siegert <bsiegert@gmail.com>
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Benny Siegert <bsiegert@gmail.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
---
 windows/syscall_windows.go | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/windows/syscall_windows.go b/windows/syscall_windows.go
index 3f2cbb63..5f4f0430 100644
--- a/windows/syscall_windows.go
+++ b/windows/syscall_windows.go
@@ -1115,9 +1115,13 @@ func Shutdown(fd Handle, how int) (err error) {
 }
 
 func WSASendto(s Handle, bufs *WSABuf, bufcnt uint32, sent *uint32, flags uint32, to Sockaddr, overlapped *Overlapped, croutine *byte) (err error) {
-	rsa, l, err := to.sockaddr()
-	if err != nil {
-		return err
+	var rsa unsafe.Pointer
+	var l int32
+	if to != nil {
+		rsa, l, err = to.sockaddr()
+		if err != nil {
+			return err
+		}
 	}
 	return WSASendTo(s, bufs, bufcnt, sent, flags, (*RawSockaddrAny)(unsafe.Pointer(rsa)), l, overlapped, croutine)
 }