net: make UnixAddr implement sockaddr interface

This is in preparation for runtime-integrated network pollster for BSD
variants.

Update #5199

R=golang-dev, dave
CC=golang-dev
https://golang.org/cl/11932044

Author: cixtor

src/pkg/net/sock_posix.go

@@ -11,8 +11,8 @@ import (
 	"time"
 )
 
-// A sockaddr represents a TCP, UDP, IP network endpoint address that
-// can be converted into a syscall.Sockaddr.
+// A sockaddr represents a TCP, UDP, IP or Unix network endpoint
+// address that can be converted into a syscall.Sockaddr.
 type sockaddr interface {
 	Addr
 	family() int

src/pkg/net/unixsock.go

@@ -23,13 +23,6 @@ func (a *UnixAddr) String() string {
 	return a.Name
 }
 
-func (a *UnixAddr) toAddr() Addr {
-	if a == nil { // nil *UnixAddr
-		return nil // nil interface
-	}
-	return a
-}
-
 // ResolveUnixAddr parses addr as a Unix domain socket address.
 // The string net gives the network name, "unix", "unixgram" or
 // "unixpacket".

src/pkg/net/unixsock_posix.go

@@ -13,13 +13,6 @@ import (
 	"time"
 )
 
-func (a *UnixAddr) isUnnamed() bool {
-	if a == nil || a.Name == "" {
-		return true
-	}
-	return false
-}
-
 func unixSocket(net string, laddr, raddr *UnixAddr, mode string, deadline time.Time) (*netFD, error) {
 	var sotype int
 	switch net {
@@ -36,12 +29,12 @@ func unixSocket(net string, laddr, raddr *UnixAddr, mode string, deadline time.T
 	var la, ra syscall.Sockaddr
 	switch mode {
 	case "dial":
-		if !laddr.isUnnamed() {
+		if !laddr.isWildcard() {
 			la = &syscall.SockaddrUnix{Name: laddr.Name}
 		}
 		if raddr != nil {
 			ra = &syscall.SockaddrUnix{Name: raddr.Name}
-		} else if sotype != syscall.SOCK_DGRAM || laddr.isUnnamed() {
+		} else if sotype != syscall.SOCK_DGRAM || laddr.isWildcard() {
 			return nil, &OpError{Op: mode, Net: net, Err: errMissingAddress}
 		}
 	case "listen":
@@ -106,6 +99,29 @@ func sotypeToNet(sotype int) string {
 	}
 }
 
+func (a *UnixAddr) family() int {
+	return syscall.AF_UNIX
+}
+
+// isWildcard reports whether a is a wildcard address.
+func (a *UnixAddr) isWildcard() bool {
+	return a == nil || a.Name == ""
+}
+
+func (a *UnixAddr) sockaddr(family int) (syscall.Sockaddr, error) {
+	if a == nil {
+		return nil, nil
+	}
+	return &syscall.SockaddrUnix{Name: a.Name}, nil
+}
+
+func (a *UnixAddr) toAddr() sockaddr {
+	if a == nil {
+		return nil
+	}
+	return a
+}
+
 // UnixConn is an implementation of the Conn interface for connections
 // to Unix domain sockets.
 type UnixConn struct {