From 8cfa568d3c25ac0ef41047a62ff55955949726ed Mon Sep 17 00:00:00 2001
From: Tobias Klauser <tklauser@distanz.ch>
Date: Mon, 26 Sep 2022 16:36:19 +0200
Subject: [PATCH] unix: allow calling Sendto with nil Sockaddr

Same as CL 433504 did for the syscall package.

For golang/go#55845

Change-Id: I3ca2d7fab9da77c304487b4c134a9675da99deca
Reviewed-on: https://go-review.googlesource.com/c/sys/+/434515
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
---
 unix/syscall_unix.go | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/unix/syscall_unix.go b/unix/syscall_unix.go
index 9f753560..00bafda8 100644
--- a/unix/syscall_unix.go
+++ b/unix/syscall_unix.go
@@ -423,11 +423,15 @@ func Send(s int, buf []byte, flags int) (err error) {
 }
 
 func Sendto(fd int, p []byte, flags int, to Sockaddr) (err error) {
-	ptr, n, err := to.sockaddr()
-	if err != nil {
-		return err
+	var ptr unsafe.Pointer
+	var salen _Socklen
+	if to != nil {
+		ptr, salen, err = to.sockaddr()
+		if err != nil {
+			return err
+		}
 	}
-	return sendto(fd, p, flags, ptr, n)
+	return sendto(fd, p, flags, ptr, salen)
 }
 
 func SetsockoptByte(fd, level, opt int, value byte) (err error) {