[Nbd] [PATCH 2/3] NBD proto: document additional error conditions

["Denis V. Lunev" <den@...2317...>]

From: Pavel Borzenkov <pborzenkov@...2319...>

It is unclear what the behaviour of a server should be if it receives
an unknown command. Similar uncertainty exists for command flags.

Make it explicit that the server should return EINVAL in all such cases.

Signed-off-by: Pavel Borzenkov <pborzenkov@...2319...>
Reviewed-by: Roman Kagan <rkagan@...2319...>
Signed-off-by: Denis V. Lunev <den@...2317...>
CC: Wouter Verhelst <w@...112...>
CC: Eric Blake <eblake@...696...>
CC: Alex Bligh <alex@...872...>
---
 doc/proto.md | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/doc/proto.md b/doc/proto.md
index d54ed19..036d6d9 100644
--- a/doc/proto.md
+++ b/doc/proto.md
@@ -512,6 +512,13 @@ return `EINVAL` if it receives a read or trim request including one or
 more sectors beyond the size of the device.  It also SHOULD map the
 `EDQUOT` and `EFBIG` errors to `ENOSPC`.  Finally, it SHOULD return
 `EPERM` if it receives a write or trim request on a read-only export.
+
+The server SHOULD return `EINVAL` if it receives an unknown command.
+
+The server SHOULD return `EINVAL` if it receives an unknown command flag. It
+also SHOULD return `EINVAL` if it receives a request with a flag not explicitly
+documented as applicable to the given request.
+
 Which error to return in any other case is not specified by the NBD
 protocol.
 
-- 
2.1.4