syscall: add ipv4 ancillary data for darwin

R=golang-dev, dave
CC=golang-dev
https://golang.org/cl/6586044

src/pkg/syscall/types_darwin.go

@@ -150,6 +150,8 @@ type Msghdr C.struct_msghdr
 
 type Cmsghdr C.struct_cmsghdr
 
+type Inet4Pktinfo C.struct_in_pktinfo
+
 type Inet6Pktinfo C.struct_in6_pktinfo
 
 const (
@@ -163,6 +165,7 @@ const (
 	SizeofIPv6Mreq         = C.sizeof_struct_ipv6_mreq
 	SizeofMsghdr           = C.sizeof_struct_msghdr
 	SizeofCmsghdr          = C.sizeof_struct_cmsghdr
+	SizeofInet4Pktinfo     = C.sizeof_struct_in_pktinfo
 	SizeofInet6Pktinfo     = C.sizeof_struct_in6_pktinfo
 )
 

src/pkg/syscall/ztypes_darwin_386.go

@@ -226,6 +226,12 @@ type Cmsghdr struct {
 	Type  int32
 }
 
+type Inet4Pktinfo struct {
+	Ifindex  uint32
+	Spec_dst [4]byte /* in_addr */
+	Addr     [4]byte /* in_addr */
+}
+
 type Inet6Pktinfo struct {
 	Addr    [16]byte /* in6_addr */
 	Ifindex uint32
@@ -242,6 +248,7 @@ const (
 	SizeofIPv6Mreq         = 0x14
 	SizeofMsghdr           = 0x1c
 	SizeofCmsghdr          = 0xc
+	SizeofInet4Pktinfo     = 0xc
 	SizeofInet6Pktinfo     = 0x14
 )
 

src/pkg/syscall/ztypes_darwin_amd64.go

@@ -234,6 +234,12 @@ type Cmsghdr struct {
 	Type  int32
 }
 
+type Inet4Pktinfo struct {
+	Ifindex  uint32
+	Spec_dst [4]byte /* in_addr */
+	Addr     [4]byte /* in_addr */
+}
+
 type Inet6Pktinfo struct {
 	Addr    [16]byte /* in6_addr */
 	Ifindex uint32
@@ -250,6 +256,7 @@ const (
 	SizeofIPv6Mreq         = 0x14
 	SizeofMsghdr           = 0x30
 	SizeofCmsghdr          = 0xc
+	SizeofInet4Pktinfo     = 0xc
 	SizeofInet6Pktinfo     = 0x14
 )