Simplify choosing the key description prefix

There's no real need to allow users to choose the key description prefix
(a.k.a. the "service"), since on ext4 and f2fs we can just use "ext4"
and "f2fs" for compatibility with all kernels both old and new, and on
other filesystems we can just use "fscrypt".  So, let's do that.

Since this removes the point of the "--legacy" option to 'fscrypt setup'
and the "compatibility" field in /etc/fscrypt.conf, remove those too.

Specifically, we start ignoring the "compatibility" in existing config
files and not writing it to new ones.  The corresponding protobuf field
number and name are reserved.  We stop accepting the "--legacy" option
at all, although since it was default true and there was no real reason
for anyone to change it to false, probably no one will notice.  If
anyone does, they should just stop specifying the option.

Note that this change only affects user keyrings and thus only affects
v1 encryption policies, which are deprecated in favor of v2 anyway.

1 files changed, 4 insertions, 1 deletions

diff --git a/metadata/metadata.proto b/metadata/metadata.proto
index 81b3bf9..8ffb4f6 100644
--- a/metadata/metadata.proto
+++ b/metadata/metadata.proto
@@ -97,7 +97,10 @@ message PolicyData {
 message Config {
   SourceType source = 1;
   HashingCosts hash_costs = 2;
-  string compatibility = 3;
   EncryptionOptions options = 4;
   bool use_fs_keyring_for_v1_policies = 5;
+
+  // reserve the removed field 'string compatibility = 3;'
+  reserved 3;
+  reserved "compatibility";
 }