unix: add godoc for Sockaddr* types

Add rudimentary godoc for all existing Sockaddr* types implementing the
Sockaddr interface.

Change-Id: Ida7d1e8756477b54fc773f4bc978002c3d4a376d
Reviewed-on: https://go-review.googlesource.com/89775Reviewed-by: Ian Lance Taylor <iant@golang.org>

unix/syscall_darwin.go

@@ -36,6 +36,7 @@ func Getwd() (string, error) {
 	return "", ENOTSUP
 }
 
+// SockaddrDatalink implements the Sockaddr interface for AF_LINK type sockets.
 type SockaddrDatalink struct {
 	Len    uint8
 	Family uint8

unix/syscall_dragonfly.go

@@ -14,6 +14,7 @@ package unix
 
 import "unsafe"
 
+// SockaddrDatalink implements the Sockaddr interface for AF_LINK type sockets.
 type SockaddrDatalink struct {
 	Len    uint8
 	Family uint8

unix/syscall_freebsd.go

@@ -14,6 +14,7 @@ package unix
 
 import "unsafe"
 
+// SockaddrDatalink implements the Sockaddr interface for AF_LINK type sockets.
 type SockaddrDatalink struct {
 	Len    uint8
 	Family uint8

unix/syscall_linux.go

@@ -420,6 +420,7 @@ func (sa *SockaddrUnix) sockaddr() (unsafe.Pointer, _Socklen, error) {
 	return unsafe.Pointer(&sa.raw), sl, nil
 }
 
+// SockaddrLinklayer implements the Sockaddr interface for AF_PACKET type sockets.
 type SockaddrLinklayer struct {
 	Protocol uint16
 	Ifindex  int
@@ -446,6 +447,7 @@ func (sa *SockaddrLinklayer) sockaddr() (unsafe.Pointer, _Socklen, error) {
 	return unsafe.Pointer(&sa.raw), SizeofSockaddrLinklayer, nil
 }
 
+// SockaddrNetlink implements the Sockaddr interface for AF_NETLINK type sockets.
 type SockaddrNetlink struct {
 	Family uint16
 	Pad    uint16
@@ -462,6 +464,8 @@ func (sa *SockaddrNetlink) sockaddr() (unsafe.Pointer, _Socklen, error) {
 	return unsafe.Pointer(&sa.raw), SizeofSockaddrNetlink, nil
 }
 
+// SockaddrHCI implements the Sockaddr interface for AF_BLUETOOTH type sockets
+// using the HCI protocol.
 type SockaddrHCI struct {
 	Dev     uint16
 	Channel uint16
@@ -475,6 +479,8 @@ func (sa *SockaddrHCI) sockaddr() (unsafe.Pointer, _Socklen, error) {
 	return unsafe.Pointer(&sa.raw), SizeofSockaddrHCI, nil
 }
 
+// SockaddrL2 implements the Sockaddr interface for AF_BLUETOOTH type sockets
+// using the L2CAP protocol.
 type SockaddrL2 struct {
 	PSM      uint16
 	CID      uint16

unix/syscall_netbsd.go

@@ -17,6 +17,7 @@ import (
 	"unsafe"
 )
 
+// SockaddrDatalink implements the Sockaddr interface for AF_LINK type sockets.
 type SockaddrDatalink struct {
 	Len    uint8
 	Family uint8

unix/syscall_openbsd.go

@@ -18,6 +18,7 @@ import (
 	"unsafe"
 )
 
+// SockaddrDatalink implements the Sockaddr interface for AF_LINK type sockets.
 type SockaddrDatalink struct {
 	Len    uint8
 	Family uint8

unix/syscall_solaris.go

@@ -23,6 +23,7 @@ type syscallFunc uintptr
 func rawSysvicall6(trap, nargs, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2 uintptr, err syscall.Errno)
 func sysvicall6(trap, nargs, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2 uintptr, err syscall.Errno)
 
+// SockaddrDatalink implements the Sockaddr interface for AF_LINK type sockets.
 type SockaddrDatalink struct {
 	Family uint16
 	Index  uint16

unix/syscall_unix.go

@@ -149,16 +149,19 @@ func Write(fd int, p []byte) (n int, err error) {
 // creation of IPv6 sockets to return EAFNOSUPPORT.
 var SocketDisableIPv6 bool
 
+// Sockaddr represents a socket address.
 type Sockaddr interface {
 	sockaddr() (ptr unsafe.Pointer, len _Socklen, err error) // lowercase; only we can define Sockaddrs
 }
 
+// SockaddrInet4 implements the Sockaddr interface for AF_INET type sockets.
 type SockaddrInet4 struct {
 	Port int
 	Addr [4]byte
 	raw  RawSockaddrInet4
 }
 
+// SockaddrInet6 implements the Sockaddr interface for AF_INET6 type sockets.
 type SockaddrInet6 struct {
 	Port   int
 	ZoneId uint32
@@ -166,6 +169,7 @@ type SockaddrInet6 struct {
 	raw    RawSockaddrInet6
 }
 
+// SockaddrUnix implements the Sockaddr interface for AF_UNIX type sockets.
 type SockaddrUnix struct {
 	Name string
 	raw  RawSockaddrUnix