diff options
Diffstat (limited to 'qapi-schema-guest.json')
| -rw-r--r-- | qapi-schema-guest.json | 48 |
1 files changed, 47 insertions, 1 deletions
diff --git a/qapi-schema-guest.json b/qapi-schema-guest.json index 12b5d4fdef..cf18876c57 100644 --- a/qapi-schema-guest.json +++ b/qapi-schema-guest.json @@ -1,6 +1,41 @@ # *-*- Mode: Python -*-* ## +# +# Echo back a unique integer value, and prepend to response a +# leading sentinel byte (0xFF) the client can check scan for. +# +# This is used by clients talking to the guest agent over the +# wire to ensure the stream is in sync and doesn't contain stale +# data from previous client. It must be issued upon initial +# connection, and after any client-side timeouts (including +# timeouts on receiving a response to this command). +# +# After issuing this request, all guest agent responses should be +# ignored until the response containing the unique integer value +# the client passed in is returned. Receival of the 0xFF sentinel +# byte must be handled as an indication that the client's +# lexer/tokenizer/parser state should be flushed/reset in +# preparation for reliably receiving the subsequent response. As +# an optimization, clients may opt to ignore all data until a +# sentinel value is receiving to avoid unecessary processing of +# stale data. +# +# Similarly, clients should also precede this *request* +# with a 0xFF byte to make sure the guest agent flushes any +# partially read JSON data from a previous client connection. +# +# @id: randomly generated 64-bit integer +# +# Returns: The unique integer id passed in by the client +# +# Since: 1.1 +# ## +{ 'command': 'guest-sync-delimited' + 'data': { 'id': 'int' }, + 'returns': 'int' } + +## # @guest-sync: # # Echo back a unique integer value @@ -13,8 +48,19 @@ # partially-delivered JSON text in such a way that this response # can be obtained. # +# In cases where a partial stale response was previously +# received by the client, this cannot always be done reliably. +# One particular scenario being if qemu-ga responses are fed +# character-by-character into a JSON parser. In these situations, +# using guest-sync-delimited may be optimal. +# +# For clients that fetch responses line by line and convert them +# to JSON objects, guest-sync should be sufficient, but note that +# in cases where the channel is dirty some attempts at parsing the +# response may result in a parser error. +# # Such clients should also precede this command -# with a 0xFF byte to make such the guest agent flushes any +# with a 0xFF byte to make sure the guest agent flushes any # partially read JSON data from a previous session. # # @id: randomly generated 64-bit integer |