net: check Getsockname error return

    
    Reviewed-on: https://go-review.googlesource.com/64550

From-SVN: r253231

gcc/go/gofrontend/MERGE

-e0c1f0b645b12a544b484c0f477f8fb6f5980550
+cdf1f58c7578980e1d1949680c7e404961b7c153
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

libgo/go/net/sock_posix.go

@@ -182,7 +182,10 @@ func (fd *netFD) listenStream(laddr sockaddr, backlog int) error {
 	if err := fd.init(); err != nil {
 		return err
 	}
-	lsa, _ := syscall.Getsockname(fd.pfd.Sysfd)
+	lsa, err := syscall.Getsockname(fd.pfd.Sysfd)
+	if err != nil {
+		return os.NewSyscallError("getsockname", err)
+	}
 	fd.setAddr(fd.addrFunc()(lsa), nil)
 	return nil
 }
@@ -221,7 +224,10 @@ func (fd *netFD) listenDatagram(laddr sockaddr) error {
 	if err := fd.init(); err != nil {
 		return err
 	}
-	lsa, _ := syscall.Getsockname(fd.pfd.Sysfd)
+	lsa, err := syscall.Getsockname(fd.pfd.Sysfd)
+	if err != nil {
+		return os.NewSyscallError("getsockname", err)
+	}
 	fd.setAddr(fd.addrFunc()(lsa), nil)
 	return nil
 }