From 0b940a756838efcb90363ad99cb085d077b78e96 Mon Sep 17 00:00:00 2001
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Wed, 18 Apr 2018 07:54:39 +0200
Subject: [PATCH] Use socketcall on x86

---
 conn_linux.go        | 50 +++++------------------------------------
 syscall_linux.go     | 30 +++++++++++++++++++++++++
 syscall_linux_386.go | 53 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 89 insertions(+), 44 deletions(-)
 create mode 100644 syscall_linux.go
 create mode 100644 syscall_linux_386.go

diff --git a/conn_linux.go b/conn_linux.go
index cdba74f..8b60d65 100644
--- a/conn_linux.go
+++ b/conn_linux.go
@@ -391,14 +391,7 @@ func send6(sock int, end *NativeEndpoint, buff []byte) error {
 
 	msghdr.SetControllen(int(unsafe.Sizeof(cmsg)))
 
-	// sendmsg(sock, &msghdr, 0)
-
-	_, _, errno := unix.Syscall(
-		unix.SYS_SENDMSG,
-		uintptr(sock),
-		uintptr(unsafe.Pointer(&msghdr)),
-		0,
-	)
+	_, _, errno := sendmsg(sock, &msghdr, 0)
 
 	if errno == 0 {
 		return nil
@@ -409,12 +402,7 @@ func send6(sock int, end *NativeEndpoint, buff []byte) error {
 	if errno == unix.EINVAL {
 		end.ClearSrc()
 		cmsg.pktinfo = unix.Inet6Pktinfo{}
-		_, _, errno = unix.Syscall(
-			unix.SYS_SENDMSG,
-			uintptr(sock),
-			uintptr(unsafe.Pointer(&msghdr)),
-			0,
-		)
+		_, _, errno = sendmsg(sock, &msghdr, 0)
 	}
 
 	return errno
@@ -455,26 +443,14 @@ func send4(sock int, end *NativeEndpoint, buff []byte) error {
 	}
 	msghdr.SetControllen(int(unsafe.Sizeof(cmsg)))
 
-	// sendmsg(sock, &msghdr, 0)
-
-	_, _, errno := unix.Syscall(
-		unix.SYS_SENDMSG,
-		uintptr(sock),
-		uintptr(unsafe.Pointer(&msghdr)),
-		0,
-	)
+	_, _, errno := sendmsg(sock, &msghdr, 0)
 
 	// clear source and try again
 
 	if errno == unix.EINVAL {
 		end.ClearSrc()
 		cmsg.pktinfo = unix.Inet4Pktinfo{}
-		_, _, errno = unix.Syscall(
-			unix.SYS_SENDMSG,
-			uintptr(sock),
-			uintptr(unsafe.Pointer(&msghdr)),
-			0,
-		)
+		_, _, errno = sendmsg(sock, &msghdr, 0)
 	}
 
 	// errno = 0 is still an error instance
@@ -507,14 +483,7 @@ func receive4(sock int, buff []byte, end *NativeEndpoint) (int, error) {
 	msghdr.Control = (*byte)(unsafe.Pointer(&cmsg))
 	msghdr.SetControllen(int(unsafe.Sizeof(cmsg)))
 
-	// recvmsg(sock, &mskhdr, 0)
-
-	size, _, errno := unix.Syscall(
-		unix.SYS_RECVMSG,
-		uintptr(sock),
-		uintptr(unsafe.Pointer(&msghdr)),
-		0,
-	)
+	size, _, errno := recvmsg(sock, &msghdr, 0)
 
 	if errno != 0 {
 		return 0, errno
@@ -555,14 +524,7 @@ func receive6(sock int, buff []byte, end *NativeEndpoint) (int, error) {
 	msg.Control = (*byte)(unsafe.Pointer(&cmsg))
 	msg.SetControllen(int(unsafe.Sizeof(cmsg)))
 
-	// recvmsg(sock, &mskhdr, 0)
-
-	size, _, errno := unix.Syscall(
-		unix.SYS_RECVMSG,
-		uintptr(sock),
-		uintptr(unsafe.Pointer(&msg)),
-		0,
-	)
+	size, _, errno := recvmsg(sock, &msg, 0)
 
 	if errno != 0 {
 		return 0, errno
diff --git a/syscall_linux.go b/syscall_linux.go
new file mode 100644
index 0000000..3403544
--- /dev/null
+++ b/syscall_linux.go
@@ -0,0 +1,30 @@
+// +build linux,!386
+
+/* Copyright 2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
+package main
+
+import (
+	"golang.org/x/sys/unix"
+	"syscall"
+	"unsafe"
+)
+
+func sendmsg(fd int, msghdr *unix.Msghdr, flags int) (uintptr, uintptr, syscall.Errno) {
+	return unix.Syscall(
+		unix.SYS_SENDMSG,
+		uintptr(fd),
+		uintptr(unsafe.Pointer(msghdr)),
+		uintptr(flags),
+	)
+}
+
+func recvmsg(fd int, msghdr *unix.Msghdr, flags int) (uintptr, uintptr, syscall.Errno) {
+	return unix.Syscall(
+		unix.SYS_RECVMSG,
+		uintptr(fd),
+		uintptr(unsafe.Pointer(msghdr)),
+		uintptr(flags),
+	)
+}
diff --git a/syscall_linux_386.go b/syscall_linux_386.go
new file mode 100644
index 0000000..76d7c7e
--- /dev/null
+++ b/syscall_linux_386.go
@@ -0,0 +1,53 @@
+// +build linux,386
+
+/* Copyright 2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
+package main
+
+import (
+	"golang.org/x/sys/unix"
+	"syscall"
+	"unsafe"
+)
+
+const (
+	_SENDMSG = 16
+	_RECVMSG = 17
+)
+
+func sendmsg(fd int, msghdr *unix.Msghdr, flags int) (uintptr, uintptr, syscall.Errno) {
+	args := struct {
+		fd     uintptr
+		msghdr uintptr
+		flags  uintptr
+	}{
+		uintptr(fd),
+		uintptr(unsafe.Pointer(msghdr)),
+		uintptr(flags),
+	}
+	return unix.Syscall(
+		unix.SYS_SOCKETCALL,
+		_SENDMSG,
+		uintptr(unsafe.Pointer(&args)),
+		0,
+	)
+}
+
+func recvmsg(fd int, msghdr *unix.Msghdr, flags int) (uintptr, uintptr, syscall.Errno) {
+	args := struct {
+		fd     uintptr
+		msghdr uintptr
+		flags  uintptr
+	}{
+		uintptr(fd),
+		uintptr(unsafe.Pointer(msghdr)),
+		uintptr(flags),
+	}
+	return unix.Syscall(
+		unix.SYS_SOCKETCALL,
+		_RECVMSG,
+		uintptr(unsafe.Pointer(&args)),
+		0,
+	)
+}