A ServerMessage is a container used to encapsulate all the possible
message types the server may send to a client.
message ServerMessage {
oneof type {
ServerHello hello = 1;
TimeSpec commit_point = 2;
string log_id = 3;
string error = 4;
string abort = 5;
}
}
The different ServerMessage sub-messages the server may sent to the
client are described below.
ServerHello hello
message ServerHello {
string server_id = 1;
string redirect = 2;
repeated string servers = 3;
bool subcommands = 4;
}
The ServerHello message consists of server information sent when
the client first connects. It contains the following members:
server_id
A free-form server description. Usually this includes the
name and version of the implementation running on the log
server. This member is always present.
redirect
A host and port separated by a colon (''): that the client
should connect to instead. The host may be a host name, an
IPv4 address, or an IPv6 address in square brackets. This
may be used for server load balancing. The server will
disconnect after sending the ServerHello when it includes a
redirect.
servers
A list of other known log servers. This can be used to
implement log server redundancy and allows the client to
discover all other log servers simply by connecting to one
known server. This member may be omitted when there is
only a single log server.
subcommands
If set, the server supports logging additional commands
during a session. The client may send an AcceptMessage or
RejectMessage when sudo is running in intercept mode. In
this mode, commands spawned from the initial command
authorized by sudo are subject to policy restrictions
and/or are logged. If subcommands is false, the client
must not attempt to log additional commands.
TimeSpec commit_point
A periodic time stamp sent by the server to indicate when I/O log
buffers have been committed to storage. This message is not sent
after every IoBuffer but rather at a server-configurable interval.
When the server receives an ExitMessage, it will respond with a
commit_point corresponding to the last received IoBuffer before
closing the connection.
string log_id
The server-side ID of the I/O log being stored, sent in response to
an AcceptMessage where expect_iobufs is true.
string error
A fatal server-side error. The server will close the connection
after sending the error message.
string abort
An abort message from the server indicates that the client should
kill the command and terminate the session. It may be used to
implement simple server-side policy. The server will close the
connection after sending the abort message.
