FreeBSD xattr support (#3650)

* Support FreeBSD xattr naming

There is a slight compatibilty issue due to FreeBSD disallowing
usage of the `user.` prefix when it comes to xattr names.
Just for FreeBSD this patch removes that `user.` prefix (leaving
`ocis.`) which allows it to run on FreeBSD.

* Cleanup the FreeBSD xattr naming

* Comment for default xattr namespace as per Codacy static analysis

* chore: changelog update for freebsd-xattr-support

---------

Co-authored-by: Jur van den Berg <[email protected]>

changelog/unreleased/freebsd-xattr-support.md

@@ -0,0 +1,5 @@
+Bugfix: FreeBSD xattr support
+
+We now properly handle FreeBSD xattr namespaces by leaving out the `user.` prefix. FreeBSD adds that automatically.
+
+https://github.com/cs3org/reva/pull/3650

pkg/storage/utils/decomposedfs/xattrs/xattrs.go

@@ -36,9 +36,8 @@ import (
 // A non root user can only manipulate the user. namespace, which is what
 // we will use to store ownCloud specific metadata. To prevent name
 // collisions with other apps We are going to introduce a sub namespace
-// "user.ocis."
+// "user.ocis." in the xattrs_prefix*.go files.
 const (
-	OcisPrefix    string = "user.ocis."
 	ParentidAttr  string = OcisPrefix + "parentid"
 	OwnerIDAttr   string = OcisPrefix + "owner.id"
 	OwnerIDPAttr  string = OcisPrefix + "owner.idp"

pkg/storage/utils/decomposedfs/xattrs/xattrs_prefix.go

@@ -0,0 +1,11 @@
+//go:build !freebsd
+
+package xattrs
+
+// The default namespace for ocis. As non root users can only manipulate
+// the user. namespace, which is what is used to store ownCloud specific
+// metadata. To prevent name collisions with other apps, we are going to
+// introduce a sub namespace "user.ocis."
+const (
+	OcisPrefix string = "user.ocis."
+)

pkg/storage/utils/decomposedfs/xattrs/xattrs_prefix_freebsd.go

@@ -0,0 +1,10 @@
+//go:build freebsd
+
+package xattrs
+
+// On FreeBSD the `user` namespace is implied through a separate syscall argument
+// and will fail with invalid argument when you try to start an xattr name with user. or system.
+// For that reason we drop the superfluous user. prefix for FreeBSD specifically.
+const (
+	OcisPrefix string = "ocis."
+)