unix: add IoctlSetString on all platforms

Currently, only solaris provides IoctlSetString. However, it might be
useful on other platforms too, e.g. for SIOCBRADDBR on linux.

Change-Id: I19ed47a3e4ed0180ba6777bc193e32bfb61c0506
Reviewed-on: https://go-review.googlesource.com/c/sys/+/720200
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Florian Lehner <lehner.florian86@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>

unix/ioctl_signed.go

diff --git a/unix/ioctl_signed.go b/unix/ioctl_signed.go
index 5b0759b..be0f3fb 100644
--- a/unix/ioctl_signed.go
+++ b/unix/ioctl_signed.go
@@ -6,9 +6,7 @@
 
 package unix
 
-import (
-	"unsafe"
-)
+import "unsafe"
 
 // ioctl itself should not be exposed directly, but additional get/set
 // functions for specific types are permissible.
@@ -28,6 +26,13 @@
 	return ioctlPtr(fd, req, unsafe.Pointer(&v))
 }
 
+// IoctlSetString performs an ioctl operation which sets a string value
+// on fd, using the specified request number.
+func IoctlSetString(fd int, req int, value string) error {
+	bs := append([]byte(value), 0)
+	return ioctlPtr(fd, req, unsafe.Pointer(&bs[0]))
+}
+
 // IoctlSetWinsize performs an ioctl on fd with a *Winsize argument.
 //
 // To change fd's window size, the req argument should be TIOCSWINSZ.

unix/ioctl_unsigned.go

diff --git a/unix/ioctl_unsigned.go b/unix/ioctl_unsigned.go
index 20f470b..f0c2821 100644
--- a/unix/ioctl_unsigned.go
+++ b/unix/ioctl_unsigned.go
@@ -6,9 +6,7 @@
 
 package unix
 
-import (
-	"unsafe"
-)
+import "unsafe"
 
 // ioctl itself should not be exposed directly, but additional get/set
 // functions for specific types are permissible.
@@ -28,6 +26,13 @@
 	return ioctlPtr(fd, req, unsafe.Pointer(&v))
 }
 
+// IoctlSetString performs an ioctl operation which sets a string value
+// on fd, using the specified request number.
+func IoctlSetString(fd int, req uint, value string) error {
+	bs := append([]byte(value), 0)
+	return ioctlPtr(fd, req, unsafe.Pointer(&bs[0]))
+}
+
 // IoctlSetWinsize performs an ioctl on fd with a *Winsize argument.
 //
 // To change fd's window size, the req argument should be TIOCSWINSZ.

unix/syscall_solaris.go

diff --git a/unix/syscall_solaris.go b/unix/syscall_solaris.go
index 18a3d9b..a6a2ea0 100644
--- a/unix/syscall_solaris.go
+++ b/unix/syscall_solaris.go
@@ -1052,14 +1052,6 @@
 	return ioctlRet(fd, req, uintptr(arg))
 }
 
-func IoctlSetString(fd int, req int, val string) error {
-	bs := make([]byte, len(val)+1)
-	copy(bs[:len(bs)-1], val)
-	err := ioctlPtr(fd, req, unsafe.Pointer(&bs[0]))
-	runtime.KeepAlive(&bs[0])
-	return err
-}
-
 // Lifreq Helpers
 
 func (l *Lifreq) SetName(name string) error {