[1mInter-Client Exchange Library[0m
[1mVersion 1.0[0m
[1mX Consortium Standard[0m
[1mX Version 11, Release 6.4[0m
[4mRalph[24m [4mMor[0m
X Consortium
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[1m1. Overview of ICE[0m
There are numerous possible inter-client protocols, with
many similarities and common needs - authentication, version
negotiation, byte order negotiation, and so on. The Inter-
Client Exchange (ICE) protocol is intended to provide a
framework for building such protocols, allowing them to make
use of common negotiation mechanisms and to be multiplexed
over a single transport connection.
[1m2. The ICE Library - C Language Interface to ICE[0m
A client that wishes to utilize ICE must first register the
protocols it understands with the ICE library. Each proto-
col is dynamically assigned a major opcode ranging from
1-255 (two clients can use different major opcodes for the
same protocol). The next step for the client is either to
open a connection with another client or to wait for connec-
tions made by other clients. Authentication may be
required. A client can both initiate connections with other
clients and be waiting for clients to connect to itself (a
nested session manager is an example). Once an ICE connec-
tion is established between the two clients, one of the
clients needs to initiate a in order to "activate" a given
protocol. Once the other client accepts the (once again,
authentication may be required), the two clients are ready
to start passing messages specific to that protocol to each
other. Multiple protocols may be active on a single ICE
connection. Clients are responsible for notifying the ICE
library when a protocol is no longer active on an ICE con-
nection, although ICE does not define how each subprotocol
triggers a protocol shutdown.
The ICE library utilizes callbacks to process incoming mes-
sages. Using callbacks allows messages and authentication
to happen behind the scenes. An additional benefit is that
messages never need to be buffered up by the library when
the client blocks waiting for a particular message.
[1m3. Intended Audience[0m
This document is intended primarily for implementors of pro-
tocol libraries layered on top of ICE. Typically, applica-
tions that wish to utilize ICE will make calls into individ-
ual protocol libraries rather than directly make calls into
the ICE library. However, some applications will have to
make some initial calls into the ICE library in order to
accept ICE connections (for example, a session manager
accepting connections from clients). But in general, proto-
col libraries should be designed to hide the inner details
of ICE from applications.
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[1m4. Header Files and Library Name[0m
The header file defines all of the ICElib data structures
and function prototypes. includes the header file which
defines all of the ICElib constants. Protocol libraries
that need to read and write messages should include the
header file
Applications should link against ICElib using -lICE.
[1m5. Note on Prefixes[0m
The following name prefixes are used in the library to dis-
tinguish between a client that initiates a and a client that
responds with a
+o - Ice Protocol Originator
+o - Ice Protocol Acceptor
[1m6. Protocol Registration[0m
In order for two clients to exchange messages for a given
protocol, each side must register the protocol with the ICE
library. The purpose of registration is for each side to
obtain a major opcode for the protocol and to provide call-
backs for processing messages and handling authentication.
There are two separate registration functions:
+o One to handle the side that does a
+o One to handle the side that responds with a
It is recommended that protocol registration occur before
the two clients establish an ICE connection. If protocol
registration occurs after an ICE connection is created,
there can be a brief interval of time in which a is
received, but the protocol is not registered. If it is not
possible to register a protocol before the creation of an
ICE connection, proper precautions should be taken to avoid
the above race condition.
The function should be called for the client that initiates
a
__
|| int IceRegisterForProtocolSetup([4mprotocol_name[24m, [4mvendor[24m,
[4mrelease[24m, [4mversion_count[24m, [4mversion_recs[24m,
[4mauth_count[24m, [4mauth_names[24m, [4mauth_procs[24m,
[4mio_error_proc[24m)
char *[4mprotocol_name[24m;
char *[4mvendor[24m;
char *[4mrelease[24m;
int [4mversion_count[24m;
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IcePoVersionRec *[4mversion_recs[24m;
int [4mauth_count[24m;
char **[4mauth_names[24m;
IcePoAuthProc *[4mauth_procs[24m;
IceIOErrorProc [4mio_error_proc[24m;
[4mprotocol_name[0m
A string specifying the name of the protocol to
register.
[4mvendor[24m A vendor string with semantics specified by the
protocol.
[4mrelease[24m A release string with semantics specified by the
protocol.
[4mversion_count[0m
The number of different versions of the protocol
supported.
[4mversion_recs[0m
List of versions and associated callbacks.
[4mauth_count[0m
The number of authentication methods supported.
[4mauth_names[0m
The list of authentication methods supported.
[4mauth_procs[0m
The list of authentication callbacks, one for each
authentication method.
[4mio_error_proc[0m
IO error handler, or NULL.
||__
returns the major opcode reserved or -1 if an error
occurred. In order to actually activate the protocol, the
function needs to be called with this major opcode. Once
the protocol is activated, all messages for the protocol
should be sent using this major opcode.
A protocol library may support multiple versions of the same
protocol. The version_recs argument specifies a list of
supported versions of the protocol, which are prioritized in
decreasing order of preference. Each version record con-
sists of a major and minor version of the protocol as well
as a callback to be used for processing incoming messages.
__
|| typedef struct { int major_version; int minor_ver-
sion; IcePoProcessMsgProc process_msg_proc; } IcePoVer-
sionRec;
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||__
The callback is responsible for processing the set of mes-
sages that can be received by the client that initiated the
For further information, see section 6.1, ``Callbacks for
Processing Messages.''
Authentication may be required before the protocol can
become active. The protocol library must register the
authentication methods that it supports with the ICE
library. The auth_names and auth_procs arguments are a list
of authentication names and callbacks that are prioritized
in decreasing order of preference. For information on the
callback, see section 6.2, ``Authentication Methods.''
The callback is invoked if the ICE connection unexpectedly
breaks. You should pass NULL for io_error_proc if not
interested in being notified. For further information, see
section 13, ``Error Handling.''
The function should be called for the client that responds
to a with a
__
|| int IceRegisterForProtocolReply([4mprotocol_name[24m, [4mvendor[24m,
[4mrelease[24m, [4mversion_count[24m, [4mversion_recs[24m,
[4mauth_count[24m, [4mauth_names[24m, [4mauth_procs[24m,
[4mhost_based_auth_proc[24m, [4mprotocol_setup_proc[24m,
[4mprotocol_activate_proc[24m, [4mio_error_proc[24m)
char *[4mprotocol_name[24m;
char *[4mvendor[24m;
char *[4mrelease[24m;
int [4mversion_count[24m;
IcePaVersionRec *[4mversion_recs[24m;
int [4mauth_count[24m;
char **[4mauth_names[24m;
IcePaAuthProc *[4mauth_procs[24m;
IceHostBasedAuthProc [4mhost_based_auth_proc[24m;
IceProtocolSetupProc [4mprotocol_setup_proc[24m;
IceProtocolActivateProc [4mprotocol_activate_proc[24m;
IceIOErrorProc [4mio_error_proc[24m;
[4mprotocol_name[0m
A string specifying the name of the protocol to
register.
[4mvendor[24m A vendor string with semantics specified by the
protocol.
[4mrelease[24m A release string with semantics specified by the
protocol.
[4mversion_count[0m
The number of different versions of the protocol
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supported.
[4mversion_recs[0m
List of versions and associated callbacks.
[4mauth_count[0m
The number of authentication methods supported.
[4mauth_names[0m
The list of authentication methods supported.
[4mauth_procs[0m
The list of authentication callbacks, one for each
authentication method.
[4mhost_based_auth_proc[0m
Host based authentication callback.
[4mprotocol_setup_proc[0m
A callback to be invoked when authentication has
succeeded for a but before the is sent.
[4mprotocol_activate_proc[0m
A callback to be invoked after the is sent.
[4mio_error_proc[0m
IO error handler, or NULL.
||__
returns the major opcode reserved or -1 if an error
occurred. The major opcode should be used in all subsequent
messages sent for this protocol.
A protocol library may support multiple versions of the same
protocol. The version_recs argument specifies a list of
supported versions of the protocol, which are prioritized in
decreasing order of preference. Each version record con-
sists of a major and minor version of the protocol as well
as a callback to be used for processing incoming messages.
__
|| typedef struct { int major_version; int minor_ver-
sion; IcePaProcessMsgProc process_msg_proc; } IcePaVer-
sionRec;
||__
The callback is responsible for processing the set of mes-
sages that can be received by the client that accepted the
For further information, see section 6.1, ``Callbacks for
Processing Messages.''
Authentication may be required before the protocol can
become active. The protocol library must register the
authentication methods that it supports with the ICE
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library. The auth_names and auth_procs arguments are a list
of authentication names and callbacks that are prioritized
in decreasing order of preference. For information on the
callback, see section 6.2, ``Authentication Methods.''
If authentication fails and the client attempting to initi-
ate the has not required authentication, the callback is
invoked with the host name of the originating client. If
the callback returns the will succeed, even though the orig-
inal authentication failed. Note that authentication can
effectively be disabled by registering an which always
returns If no host based authentication is allowed, you
should pass NULL for host_based_auth_proc.
__
|| typedef Bool (*IceHostBasedAuthProc) ();
Bool HostBasedAuthProc([4mhost_name[24m)
char *[4mhost_name[24m;
[4mhost_name[24m The host name of the client that sent the
||__
The host_name argument is a string of the form [4mproto-[0m
[4mcol[24m/[4mhostname[24m, where [4mprotocol[24m is one of {tcp, decnet, local}.
Because messages and authentication happen behind the scenes
via callbacks, the protocol library needs some way of being
notified when the has completed. This occurs in two phases.
In the first phase, the callback is invoked after authenti-
cation has successfully completed but before the ICE library
sends a Any resources required for this protocol should be
allocated at this time. If the returns a successful status,
the ICE library will send the and then invoke the callback.
Otherwise, an error will be sent to the other client in
response to the
The is an optional callback and should be registered only if
the protocol library intends to generate a message immedi-
ately following the You should pass NULL for protocol_acti-
vate_proc if not interested in this callback.
__
|| typedef Status (*IceProtocolSetupProc) ();
Status ProtocolSetupProc([4mice_conn[24m, [4mmajor_version[24m, [4mminor_ver-[0m
[4msion[24m, [4mvendor[24m, [4mrelease[24m,
[4mclient_data_ret[24m, [4mfailure_reason_ret[24m)
IceConn [4mice_conn[24m;
int [4mmajor_version[24m;
int [4mminor_version[24m;
char *[4mvendor[24m;
char *[4mrelease[24m;
IcePointer *[4mclient_data_ret[24m;
char **[4mfailure_reason_ret[24m;
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[4mice_conn[24m The ICE connection object.
[4mmajor_version[0m
The major version of the protocol.
[4mminor_version[0m
The minor version of the protocol.
[4mvendor[24m The vendor string registered by the protocol orig-
inator.
[4mrelease[24m The release string registered by the protocol
originator.
[4mclient_data_ret[0m
Client data to be set by callback.
[4mfailure_reason_ret[0m
Failure reason returned.
||__
The pointer stored in the client_data_ret argument will be
passed to the callback whenever a message has arrived for
this protocol on the ICE connection.
The vendor and release strings should be freed with when
they are no longer needed.
If a failure occurs, the should return a zero status as well
as allocate and return a failure reason string in fail-
ure_reason_ret. The ICE library will be responsible for
freeing this memory.
The callback is defined as follows:
__
|| typedef void (*IceProtocolActivateProc)();
void ProtocolActivateProc([4mice_conn[24m, [4mclient_data[24m)
IceConn [4mice_conn[24m;
IcePointer [4mclient_data[24m;
[4mice_conn[24m The ICE connection object.
[4mclient_data[0m
The client data set in the callback.
||__
The callback is invoked if the ICE connection unexpectedly
breaks. You should pass NULL for io_error_proc if not
interested in being notified. For further information, see
section 13, ``Error Handling.''
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[1m6.1. Callbacks for Processing Messages[0m
When an application detects that there is new data to read
on an ICE connection (via it calls the function (see section
9, ``Processing Messages''). When reads an ICE message
header with a major opcode other than zero (reserved for the
ICE protocol), it needs to call a function that will read
the rest of the message, unpack it, and process it accord-
ingly.
If the message arrives at the client that initiated the the
callback is invoked.
__
|| typedef void (*IcePoProcessMsgProc)();
void PoProcessMsgProc([4mice_conn[24m, [4mclient_data[24m, [4mopcode[24m, [4mlength[24m,
[4mswap[24m, [4mreply_wait[24m, [4mreply_ready_ret[24m)
IceConn [4mice_conn[24m;
IcePointer [4mclient_data[24m;
int [4mopcode[24m;
unsigned long [4mlength[24m;
Bool [4mswap[24m;
IceReplyWaitInfo *[4mreply_wait[24m;
Bool *[4mreply_ready_ret[24m;
[4mice_conn[24m The ICE connection object.
[4mclient_data[0m
Client data associated with this protocol on the
ICE connection.
[4mopcode[24m The minor opcode of the message.
[4mlength[24m The length (in 8-byte units) of the message beyond
the ICE header.
[4mswap[24m A flag that indicates if byte swapping is neces-
sary.
[4mreply_wait[0m
Indicates if the invoking client is waiting for a
reply.
[4mreply_ready_ret[0m
If set to a reply is ready.
||__
If the message arrives at the client that accepted the the
callback is invoked.
__
|| typedef void (*IcePaProcessMsgProc)();
void PaProcessMsgProc([4mice_conn[24m, [4mclient_data[24m, [4mopcode[24m, [4mlength[24m,
[4mswap[24m)
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IceConn [4mice_conn[24m;
IcePointer [4mclient_data[24m;
int [4mopcode[24m;
unsigned long [4mlength[24m;
Bool [4mswap[24m;
[4mice_conn[24m The ICE connection object.
[4mclient_data[0m
Client data associated with this protocol on the
ICE connection.
[4mopcode[24m The minor opcode of the message.
[4mlength[24m The length (in 8-byte units) of the message beyond
the ICE header.
[4mswap[24m A flag that indicates if byte swapping is neces-
sary.
||__
In order to read the message, both of these callbacks should
use the macros defined for this purpose (see section 12.2,
``Reading ICE Messages''). Note that byte swapping may be
necessary. As a convenience, the length field in the ICE
header will be swapped by ICElib if necessary.
In both of these callbacks, the client_data argument is a
pointer to client data that was registered at time. In the
case of the client data was set in the call to In the case
of the client data was set in the callback.
The callback needs to check the reply_wait argument. If
reply_wait is NULL , the ICE library expects the function to
pass the message to the client via a callback. For example,
if this is a Session Management ``Save Yourself'' message,
this function should notify the client of the ``Save Your-
self'' via a callback. The details of how such a callback
would be defined are implementation-dependent.
However, if reply_wait is not NULL , then the client is
waiting for a reply or an error for a message it previously
sent. The reply_wait is of type
__
|| typedef struct { unsigned long sequence_of_request;
int major_opcode_of_request; int
minor_opcode_of_request; IcePointer reply; } IceReply-
WaitInfo;
||__
contains the major/minor opcodes and sequence number of the
message for which a reply is being awaited. It also con-
tains a pointer to the reply message to be filled in (the
protocol library should cast this to the appropriate reply
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type). In most cases, the reply will have some fixed-size
part, and the client waiting for the reply will have pro-
vided a pointer to a structure to hold this fixed-size data.
If there is variable-length data, it would be expected that
the callback will have to allocate additional memory and
store pointer(s) to that memory in the fixed-size structure.
If the entire data is variable length (for example., a sin-
gle variable-length string), then the client waiting for the
reply would probably just pass a pointer to fixed-size space
to hold a pointer, and the callback would allocate the stor-
age and store the pointer. It is the responsibility of the
client receiving the reply to free any memory allocated on
its behalf.
If reply_wait is not NULL and has a reply or error to return
in response to this reply_wait (that is, no callback was
generated), then the reply_ready_ret argument should be set
to Note that an error should only be returned if it corre-
sponds to the reply being waited for. Otherwise, the should
either handle the error internally or invoke an error han-
dler for its library.
If reply_wait is NULL, then care must be taken not to store
any value in reply_ready_ret, because this pointer may also
be NULL.
The callback, on the other hand, should always pass the mes-
sage to the client via a callback. For example, if this is
a Session Management ``Interact Request'' message, this
function should notify the client of the ``Interact
Request'' via a callback.
The reason the callback does not have a reply_wait, like
does, is because a process that is acting as a server should
never block for a reply (infinite blocking can occur if the
connecting client does not act properly, denying access to
other clients).
[1m6.2. Authentication Methods[0m
As already stated, a protocol library must register the
authentication methods that it supports with the ICE
library. For each authentication method, there are two
callbacks that may be registered:
+o One to handle the side that initiates a
+o One to handle the side that accepts or rejects this
request
is the callback invoked for the client that initiated the
This callback must be able to respond to the initial
``Authentication Required'' message or subsequent ``Authen-
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tication Next Phase'' messages sent by the other client.
__
|| typedef IcePoAuthStatus (*IcePoAuthProc)();
IcePoAuthStatus PoAuthProc([4mice_conn[24m, [4mauth_state_ptr[24m,
[4mclean_up[24m, [4mswap[24m, [4mauth_datalen[24m, [4mauth_data[24m,
[4mreply_datalen_ret[24m, [4mreply_data_ret[24m,
[4merror_string_ret[24m)
IceConn [4mice_conn[24m;
IcePointer *[4mauth_state_ptr[24m;
Bool [4mclean_up[24m;
Bool [4mswap[24m;
int [4mauth_datalen[24m;
IcePointer [4mauth_data[24m;
int *[4mreply_datalen_ret[24m;
IcePointer *[4mreply_data_ret[24m;
char **[4merror_string_ret[24m;
[4mice_conn[24m The ICE connection object.
[4mauth_state_ptr[0m
A pointer to state for use by the authentication
callback procedure.
[4mclean_up[24m If authentication is over, and the function should
clean up any state it was maintaining. The last 6
arguments should be ignored.
[4mswap[24m If the auth_data may have to be byte swapped
(depending on its contents).
[4mauth_datalen[0m
The length (in bytes) of the authenticator data.
[4mauth_data[24m The data from the authenticator.
[4mreply_datalen_ret[0m
The length (in bytes) of the reply data returned.
[4mreply_data_ret[0m
The reply data returned.
[4merror_string_ret[0m
If the authentication procedure encounters an
error during authentication, it should allocate
and return an error string.
||__
Authentication may require several phases, depending on the
authentication method. As a result, the may be called more
than once when authenticating a client, and some state will
have to be maintained between each invocation. At the start
of each *auth_state_ptr is NULL, and the function should
initialize its state and set this pointer. In subsequent
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invocations of the callback, the pointer should be used to
get at any state previously stored by the callback.
If needed, the network ID of the client accepting the can be
obtained by calling the function.
ICElib will be responsible for freeing the reply_data_ret
and error_string_ret pointers with
The auth_data pointer may point to a volatile block of mem-
ory. If the data must be kept beyond this invocation of the
callback, be sure to make a copy of it.
The should return one of four values:
+o - a reply is available.
+o - authentication rejected.
+o - authentication failed.
+o - done cleaning up.
is the callback invoked for the client that received the
__
|| typedef IcePaAuthStatus (*IcePaAuthProc) ();
IcePaAuthStatus PaAuthProc([4mice_conn[24m, [4mauth_state_ptr[24m, [4mswap[24m,
[4mauth_datalen[24m, [4mauth_data[24m,
[4mreply_datalen_ret[24m, [4mreply_data_ret[24m,
[4merror_string_ret[24m)
IceConn [4mice_conn[24m;
IcePointer *[4mauth_state_ptr[24m;
Bool [4mswap[24m;
int [4mauth_datalen[24m;
IcePointer [4mauth_data[24m;
int *[4mreply_datalen_ret[24m;
IcePointer *[4mreply_data_ret[24m;
char **[4merror_string_ret[24m;
[4mice_conn[24m The ICE connection object.
[4mauth_state_ptr[0m
A pointer to state for use by the authentication
callback procedure.
[4mswap[24m If auth_data may have to be byte swapped (depend-
ing on its contents).
[4mauth_datalen[0m
The length (in bytes) of the protocol originator
authentication data.
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[4mauth_data[24m The authentication data from the protocol origina-
tor.
[4mreply_datalen_ret[0m
The length of the authentication data returned.
[4mreply_data_ret[0m
The authentication data returned.
[4merror_string_ret[0m
If authentication is rejected or fails, an error
string is returned.
||__
Authentication may require several phases, depending on the
authentication method. As a result, the may be called more
than once when authenticating a client, and some state will
have to be maintained between each invocation. At the start
of each auth_datalen is zero, *auth_state_ptr is NULL, and
the function should initialize its state and set this
pointer. In subsequent invocations of the callback, the
pointer should be used to get at any state previously stored
by the callback.
If needed, the network ID of the client accepting the can be
obtained by calling the function.
The auth_data pointer may point to a volatile block of mem-
ory. If the data must be kept beyond this invocation of the
callback, be sure to make a copy of it.
ICElib will be responsible for transmitting and freeing the
reply_data_ret and error_string_ret pointers with
The should return one of four values:
+o - continue (or start) authentication.
+o - authentication accepted.
+o - authentication rejected.
+o - authentication failed.
[1m7. ICE Connections[0m
In order for two clients to establish an ICE connection, one
client has to be waiting for connections, and the other
client has to initiate the connection. Most clients will
initiate connections, so we discuss that first.
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[1m7.1. Opening an ICE Connection[0m
To open an ICE connection with another client (that is,
waiting for connections), use
__
|| IceConn IceOpenConnection([4mnetwork_ids_list[24m, [4mcontext[24m,
[4mmust_authenticate[24m, [4mmajor_opcode_check[24m,
[4merror_length[24m, [4merror_string_ret[24m)
char *[4mnetwork_ids_list[24m;
IcePointer [4mcontext[24m;
Bool [4mmust_authenticate[24m;
int [4mmajor_opcode_check[24m;
int [4merror_length[24m;
char *[4merror_string_ret[24m;
[4mnetwork_ids_list[0m
Specifies the network ID(s) of the other client.
[4mcontext[24m A pointer to an opaque object or NULL. Used to
determine if an ICE connection can be shared (see
below).
[4mmust_authenticate[0m
If the other client may not bypass authentication.
[4mmajor_opcode_check[0m
Used to force a new ICE connection to be created
(see below).
[4merror_length[0m
Length of the error_string_ret argument passed in.
[4merror_string_ret[0m
Returns a null-terminated error message, if any.
The error_string_ret argument points to user sup-
plied memory. No more than error_length bytes are
used.
||__
returns an opaque ICE connection object if it succeeds; oth-
erwise, it returns NULL.
The network_ids_list argument contains a list of network IDs
separated by commas. An attempt will be made to use the
first network ID. If that fails, an attempt will be made
using the second network ID, and so on. Each network ID has
the following format:
lw(0.25i) lw(2.5i) lw(1i). tcp/<hostname>:<portnum-
ber> or decnet/<hostname>::<objname> or
local/<hostname>:<path>
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[1mInter-Client Exchange Library X11, Release 6.4[0m
Most protocol libraries will have some sort of open function
that should internally make a call into When is called, it
may be possible to use a previously opened ICE connection
(if the target client is the same). However, there are
cases in which shared ICE connections are not desired.
The context argument is used to determine if an ICE connec-
tion can be shared. If context is NULL, then the caller is
always willing to share the connection. If context is not
NULL, then the caller is not willing to use a previously
opened ICE connection that has a different non-NULL context
associated with it.
In addition, if major_opcode_check contains a nonzero major
opcode value, a previously created ICE connection will be
used only if the major opcode is not active on the connec-
tion. This can be used to force multiple ICE connections
between two clients for the same protocol.
Any authentication requirements are handled internally by
the ICE library. The method by which the authentication
data is obtained is implementation-dependent.
After is called, the client is ready to send a (provided
that was called) or receive a (provided that was called).
[1m7.2. Listening for ICE Connections[0m
Clients wishing to accept ICE connections must first call or
so that they can listen for connections. A list of opaque
"listen" objects are returned, one for each type of trans-
port method that is available (for example, Unix Domain,
TCP, DECnet, and so on).
Normally clients will let ICElib allocate an available name
in each transport and return listen objects. Such a client
will then use to extract the chosen names and make them
available to other clients for opening the connection. In
certain cases it may be necessary for a client to listen for
connections on pre-arranged transport object names. Such a
client may use to specify the names for the listen objects.
__
|| Status IceListenForConnections([4mcount_ret[24m, [4mlisten_objs_ret[24m,
[4merror_length[24m, [4merror_string_ret[24m)
int *[4mcount_ret[24m;
IceListenObj **[4mlisten_objs_ret[24m;
int [4merror_length[24m;
char *[4merror_string_ret[24m;
[4mcount_ret[24m Returns the number of listen objects created.
-----------
The X Consortium's ICElib implementation uses
an .ICEauthority file (see Appendix A).
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[4mlisten_objs_ret[0m
Returns a list of pointers to opaque listen
objects.
[4merror_length[0m
The length of the error_string_ret argument passed
in.
[4merror_string_ret[0m
Returns a null-terminated error message, if any.
The error_string_ret points to user supplied mem-
ory. No more than error_length bytes are used.
||__
The return value of is zero for failure and a positive value
for success.
__
|| Status IceListenForWellKnownConnections([4mport_id[24m, [4mcount_ret[24m,
[4mlisten_objs_ret[24m, [4merror_length[24m, [4merror_string_ret[24m)
char *[4mport_id[24m;
int *[4mcount_ret[24m;
IceListenObj **[4mlisten_objs_ret[24m;
int [4merror_length[24m;
char *[4merror_string_ret[24m;
[4mport_id[24m Specifies the port identification for the
address(es) to be opened. The value must not con-
tain the slash (``/'') or comma (``,'') character;
these are reserved for future use.
[4mcount_ret[24m Returns the number of listen objects created.
[4mlisten_objs_ret[0m
Returns a list of pointers to opaque listen
objects.
[4merror_length[0m
The length of the error_string_ret argument passed
in.
[4merror_string_ret[0m
Returns a null-terminated error message, if any.
The error_string_ret points to user supplied mem-
ory. No more than error_length bytes are used.
||__
constructs a list of network IDs by prepending each known
transport to port_id and then attempts to create listen
objects for the result. Port_id is the portnumber, objname,
or path portion of the ICE network ID. If a listen object
for a particular network ID cannot be created the network ID
is ignored. If no listen objects are created returns fail-
ure.
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[1mInter-Client Exchange Library X11, Release 6.4[0m
The return value of is zero for failure and a positive value
for success.
To close and free the listen objects, use
__
|| void IceFreeListenObjs([4mcount[24m, [4mlisten_objs[24m)
int [4mcount[24m;
IceListenObj *[4mlisten_objs[24m;
[4mcount[24m The number of listen objects.
[4mlisten_objs[0m
The listen objects.
||__
To detect a new connection on a listen object, use on the
descriptor associated with the listen object.
To obtain the descriptor, use
__
|| int IceGetListenConnectionNumber([4mlisten_obj[24m)
IceListenObj [4mlisten_obj[24m;
[4mlisten_obj[0m
The listen object.
||__
To obtain the network ID string associated with a listen
object, use
__
|| char *IceGetListenConnectionString([4mlisten_obj[24m)
IceListenObj [4mlisten_obj[24m;
[4mlisten_obj[0m
The listen object.
||__
A network ID has the following format:
lw(0.25i) lw(2.5i) lw(1i). tcp/<hostname>:<portnum-
ber> or decnet/<hostname>::<objname> or
local/<hostname>:<path>
To compose a string containing a list of network IDs sepa-
rated by commas (the format recognized by use
- 17 -
[1mInter-Client Exchange Library X11, Release 6.4[0m
__
|| char *IceComposeNetworkIdList([4mcount[24m, [4mlisten_objs[24m)
int [4mcount[24m;
IceListenObj *[4mlisten_objs[24m;
[4mcount[24m The number of listen objects.
[4mlisten_objs[0m
The listen objects.
||__
[1m7.3. Host Based Authentication for ICE Connections[0m
If authentication fails when a client attempts to open an
ICE connection and the initiating client has not required
authentication, a host based authentication procedure may be
invoked to provide a last chance for the client to connect.
Each listen object has such a callback associated with it,
and this callback is set using the function.
__
|| void IceSetHostBasedAuthProc([4mlisten_obj[24m,
[4mhost_based_auth_proc[24m)
IceListenObj [4mlisten_obj[24m;
IceHostBasedAuthProc [4mhost_based_auth_proc[24m;
[4mlisten_obj[0m
The listen object.
[4mhost_based_auth_proc[0m
The host based authentication procedure.
||__
By default, each listen object has no host based authentica-
tion procedure associated with it. Passing NULL for
host_based_auth_proc turns off host based authentication if
it was previously set.
__
|| typedef Bool (*IceHostBasedAuthProc) ();
Bool HostBasedAuthProc([4mhost_name[24m)
char *[4mhost_name[24m;
[4mhost_name[24m The host name of the client that tried to open an
ICE connection.
||__
The host_name argument is a string in the form [4mproto-[0m
[4mcol[24m/[4mhostname[24m, where [4mprotocol[24m is one of {tcp, decnet, local}.
If returns access will be granted, even though the original
authentication failed. Note that authentication can effec-
tively be disabled by registering an which always returns
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Host based authentication is also allowed at time. The
callback is specified in the function (see section 6, ``Pro-
tocol Registration'').
[1m7.4. Accepting ICE Connections[0m
After a connection attempt is detected on a listen object
returned by you should call This returns a new opaque ICE
connection object.
__
|| IceConn IceAcceptConnection([4mlisten_obj[24m, [4mstatus_ret[24m)
IceListenObj [4mlisten_obj[24m;
IceAcceptStatus *[4mstatus_ret[24m;
[4mlisten_obj[0m
The listen object on which a new connection was
detected.
[4mstatus_ret[0m
Return status information.
||__
The status_ret argument is set to one of the following val-
ues:
+o - the accept operation succeeded, and the function
returns a new connection object.
+o - the accept operation failed, and the function returns
NULL.
+o - a memory allocation failed, and the function returns
NULL.
In general, to detect new connections, you should call on
the file descriptors associated with the listen objects.
When a new connection is detected, the function should be
called. may return a new ICE connection that is in a pend-
ing state. This is because before the connection can become
valid, authentication may be necessary. Because the ICE
library cannot block and wait for the connection to become
valid (infinite blocking can occur if the connecting client
does not act properly), the application must wait for the
connection status to become valid.
The following pseudo-code demonstrates how connections are
accepted:
new_ice_conn = IceAcceptConnection (listen_obj, &accept_sta-
tus); if (accept_status != IceAcceptSuccess) { close
the file descriptor and return }
status = IceConnectionStatus (new_ice_conn); time_start =
time_now;
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while (status == IceConnectPending) { select() on
{new_ice_conn, all open connections}
for (each ice_conn in the list of open connections)
if (data ready on ice_conn) {
status = IceProcessMessages (ice_conn, NULL,
NULL); if (status == IceProcessMessagesIOEr-
ror) IceCloseConnection (ice_conn);
}
if (data ready on new_ice_conn) { /*
* IceProcessMessages is called until the connec-
tion * is non-pending. Doing so handles the con-
nection * setup request and any authentication
requirements. */
IceProcessMessages (new_ice_conn, NULL, NULL);
status = IceConnectionStatus (new_ice_conn);
} else { if (time_now - time_start
> MAX_WAIT_TIME) status = IceConnectRejected;
} }
if (status == IceConnectAccepted) { Add new_ice_conn to
the list of open connections } else { IceCloseConnec-
tion (new_ice_conn); }
After is called and the connection has been validated, the
client is ready to receive a (provided that was called) or
send a (provided that was called).
[1m7.5. Closing ICE Connections[0m
To close an ICE connection created with or use
__
|| IceCloseStatus IceCloseConnection([4mice_conn[24m)
IceConn [4mice_conn[24m;
[4mice_conn[24m The ICE connection to close.
||__
To actually close an ICE connection, the following condi-
tions must be met:
+o The [4mopen[24m [4mreference[24m [4mcount[24m must have reached zero on this
ICE connection. When is called, it tries to use a pre-
viously opened ICE connection. If it is able to use an
existing connection, it increments the open reference
count on the connection by one. So, to close an ICE
connection, each call to must be matched with a call to
The connection can be closed only on the last call to
+o The [4mactive[24m [4mprotocol[24m [4mcount[24m must have reached zero. Each
time a succeeds on the connection, the active protocol
count is incremented by one. When the client no longer
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[1mInter-Client Exchange Library X11, Release 6.4[0m
expects to use the protocol on the connection, the
function should be called, which decrements the active
protocol count by one (see section 8, ``Protocol Setup
and Shutdown'').
+o If shutdown negotiation is enabled on the connection,
the client on the other side of the ICE connection must
agree to have the connection closed.
returns one of the following values:
+o - the ICE connection was closed at this time. The
watch procedures were invoked and the connection was
freed.
+o - an IO error had occurred on the connection, but is
being called within a nested The watch procedures have
been invoked at this time, but the connection will be
freed as soon as possible (when the nesting level
reaches zero and returns a status of
+o - the connection was not closed at this time, because
it is being used by other active protocols.
+o - the connection was not closed at this time and shut-
down negotiation started with the client on the other
side of the ICE connection. When the connection is
actually closed, will return a status of
When it is known that the client on the other side of the
ICE connection has terminated the connection without initi-
ating shutdown negotiation, the function should be called to
turn off shutdown negotiation. This will prevent from writ-
ing to a broken connection.
__
|| void IceSetShutdownNegotiation([4mice_conn[24m, [4mnegotiate[24m)
IceConn [4mice_conn[24m;
Bool [4mnegotiate[24m;
[4mice_conn[24m A valid ICE connection object.
[4mnegotiate[24m If shutdown negotiating will be turned off.
||__
To check the shutdown negotiation status of an ICE connec-
tion, use
__
|| Bool IceCheckShutdownNegotiation([4mice_conn[24m)
IceConn [4mice_conn[24m;
[4mice_conn[24m A valid ICE connection object.
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||__
returns if shutdown negotiation will take place on the con-
nection; otherwise, it returns Negotiation is on by default
for a connection. It can only be changed with the function.
[1m7.6. Connection Watch Procedures[0m
To add a watch procedure that will be called each time
ICElib opens a new connection via or or closes a connection
via use
__
|| Status IceAddConnectionWatch([4mwatch_proc[24m, [4mclient_data[24m)
IceWatchProc [4mwatch_proc[24m;
IcePointer [4mclient_data[24m;
[4mwatch_proc[0m
The watch procedure to invoke when ICElib opens or
closes a connection.
[4mclient_data[0m
This pointer will be passed to the watch proce-
dure.
||__
The return value of is zero for failure, and a positive
value for success.
Note that several calls to might share the same ICE connec-
tion. In such a case, the watch procedure is only invoked
when the connection is first created (after authentication
succeeds). Similarly, because connections might be shared,
the watch procedure is called only if actually closes the
connection (right before the IceConn is freed).
The watch procedures are very useful for applications that
need to add a file descriptor to a select mask when a new
connection is created and remove the file descriptor when
the connection is destroyed. Because connections are
shared, knowing when to add and remove the file descriptor
from the select mask would be difficult without the watch
procedures.
Multiple watch procedures may be registered with the ICE
library. No assumptions should be made about their order of
invocation.
If one or more ICE connections were already created by the
ICE library at the time the watch procedure is registered,
the watch procedure will instantly be invoked for each of
these ICE connections (with the opening argument set to
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[1mInter-Client Exchange Library X11, Release 6.4[0m
The watch procedure is of type
__
|| typedef void (*IceWatchProc)();
void WatchProc([4mice_conn[24m, [4mclient_data[24m, [4mopening[24m, [4mwatch_data[24m)
IceConn [4mice_conn[24m;
IcePointer [4mclient_data[24m;
Bool [4mopening[24m;
IcePointer *[4mwatch_data[24m;
[4mice_conn[24m The opened or closed ICE connection. Call to get
the file descriptor associated with this connec-
tion.
[4mclient_data[0m
Client data specified in the call to
[4mopening[24m If the connection is being opened. If the connec-
tion is being closed.
[4mwatch_data[0m
Can be used to save a pointer to client data.
||__
If opening is the client should set the *watch_data pointer
to any data it may need to save until the connection is
closed and the watch procedure is invoked again with opening
set to
To remove a watch procedure, use
__
|| void IceRemoveConnectionWatch([4mwatch_proc[24m, [4mclient_data[24m)
IceWatchProc [4mwatch_proc[24m;
IcePointer [4mclient_data[24m;
[4mwatch_proc[0m
The watch procedure that was passed to
[4mclient_data[0m
The client_data pointer that was passed to
||__
[1m8. Protocol Setup and Shutdown[0m
To activate a protocol on a given ICE connection, use
__
|| IceProtocolSetupStatus IceProtocolSetup([4mice_conn[24m, [4mmy_opcode[24m,
[4mclient_data[24m, [4mmust_authenticate[24m,
[4mmajor_version_ret[24m, [4mminor_version_ret[24m,
[4mvendor_ret[24m, [4mrelease_ret[24m, [4merror_length[24m, [4merror_string_ret[24m)
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[1mInter-Client Exchange Library X11, Release 6.4[0m
IceConn [4mice_conn[24m;
int [4mmy_opcode[24m;
IcePointer [4mclient_data[24m;
Bool [4mmust_authenticate[24m;
int *[4mmajor_version_ret[24m;
int *[4mminor_version_ret[24m;
char **[4mvendor_ret[24m;
char **[4mrelease_ret[24m;
int [4merror_length[24m;
char *[4merror_string_ret[24m;
[4mice_conn[24m A valid ICE connection object.
[4mmy_opcode[24m The major opcode of the protocol to be set up, as
returned by
[4mclient_data[0m
The client data stored in this pointer will be
passed to the callback.
[4mmust_authenticate[0m
If the other client may not bypass authentication.
[4mmajor_version_ret[0m
The major version of the protocol to be used is
returned.
[4mminor_version_ret[0m
The minor version of the protocol to be used is
returned.
[4mvendor_ret[0m
The vendor string specified by the protocol accep-
tor.
[4mrelease_ret[0m
The release string specified by the protocol
acceptor.
[4merror_length[0m
Specifies the length of the error_string_ret argu-
ment passed in.
[4merror_string_ret[0m
Returns a null-terminated error message, if any.
The error_string_ret argument points to user sup-
plied memory. No more than error_length bytes are
used.
||__
The vendor_ret and release_ret strings should be freed with
when no longer needed.
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[1mInter-Client Exchange Library X11, Release 6.4[0m
returns one of the following values:
+o - the major_version_ret, minor_version_ret, vendor_ret,
release_ret are set.
+o or - check error_string_ret for failure reason. The
major_version_ret, minor_version_ret, vendor_ret,
release_ret are not set.
+o - this protocol is already active on this connection.
The major_version_ret, minor_version_ret, vendor_ret,
release_ret are not set.
To notify the ICE library when a given protocol will no
longer be used on an ICE connection, use
__
|| Status IceProtocolShutdown([4mice_conn[24m, [4mmajor_opcode[24m)
IceConn [4mice_conn[24m;
int [4mmajor_opcode[24m;
[4mice_conn[24m A valid ICE connection object.
[4mmajor_opcode[0m
The major opcode of the protocol to shut down.
||__
The return value of is zero for failure and a positive value
for success.
Failure will occur if the major opcode was never registered
OR the protocol of the major opcode was never activated on
the connection. By activated, we mean that a succeeded on
the connection. Note that ICE does not define how each sub-
protocol triggers a protocol shutdown.
[1m9. Processing Messages[0m
To process incoming messages on an ICE connection, use
__
|| IceProcessMessagesStatus IceProcessMessages([4mice_conn[24m,
[4mreply_wait[24m, [4mreply_ready_ret[24m)
IceConn [4mice_conn[24m;
IceReplyWaitInfo *[4mreply_wait[24m;
Bool *[4mreply_ready_ret[24m;
[4mice_conn[24m A valid ICE connection object.
[4mreply_wait[0m
Indicates if a reply is being waited for.
[4mreply_ready_ret[0m
If set to on return, a reply is ready.
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[1mInter-Client Exchange Library X11, Release 6.4[0m
||__
is used in two ways:
+o In the first, a client may generate a message and block
by calling repeatedly until it gets its reply.
+o In the second, a client calls with reply_wait set to
NULL in response to showing that there is data to read
on the ICE connection. The ICE library may process
zero or more complete messages. Note that messages
that are not blocked for are always processed by invok-
ing callbacks.
contains the major/minor opcodes and sequence number of the
message for which a reply is being awaited. It also con-
tains a pointer to the reply message to be filled in (the
protocol library should cast this to the appropriate reply
type). In most cases, the reply will have some fixed-size
part, and the client waiting for the reply will have pro-
vided a pointer to a structure to hold this fixed-size data.
If there is variable-length data, it would be expected that
the callback will have to allocate additional memory and
store pointer(s) to that memory in the fixed-size structure.
If the entire data is variable length (for example, a single
variable-length string), then the client waiting for the
reply would probably just pass a pointer to fixed-size space
to hold a pointer, and the callback would allocate the stor-
age and store the pointer. It is the responsibility of the
client receiving the reply to free up any memory allocated
on its behalf.
__
|| typedef struct { unsigned long sequence_of_request;
int major_opcode_of_request; int
minor_opcode_of_request; IcePointer reply; } IceReply-
WaitInfo;
||__
If reply_wait is not NULL and has a reply or error to return
in response to this reply_wait (that is, no callback was
generated), then the reply_ready_ret argument will be set to
If reply_wait is NULL, then the caller may also pass NULL
for reply_ready_ret and be guaranteed that no value will be
stored in this pointer.
returns one of the following values:
+o - no error occurred.
+o - an IO error occurred, and the caller must explicitly
close the connection by calling
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[1mInter-Client Exchange Library X11, Release 6.4[0m
+o - the ICE connection has been closed (closing of the
connection was deferred because of shutdown negotia-
tion, or because the nesting level was not zero). Do
not attempt to access the ICE connection at this point,
since it has been freed.
[1m10. Ping[0m
To send a ``Ping'' message to the client on the other side
of the ICE connection, use
__
|| Status IcePing([4mice_conn[24m, [4mping_reply_proc[24m, [4mclient_data[24m)
IceConn [4mice_conn[24m;
IcePingReplyProc [4mping_reply_proc[24m;
IcePointer [4mclient_data[24m;
[4mice_conn[24m A valid ICE connection object.
[4mping_reply_proc[0m
The callback to invoke when the Ping reply
arrives.
[4mclient_data[0m
This pointer will be passed to the callback.
||__
returns zero for failure and a positive value for success.
When processes the Ping reply, it will invoke the callback.
__
|| typedef void (*IcePingReplyProc)();
void PingReplyProc([4mice_conn[24m, [4mclient_data[24m)
IceConn [4mice_conn[24m;
IcePointer [4mclient_data[24m;
[4mice_conn[24m The ICE connection object.
[4mclient_data[0m
The client data specified in the call to
||__
[1m11. Using ICElib Informational Functions[0m
__
|| IceConnectStatus IceConnectionStatus([4mice_conn[24m)
||__ IceConn [4mice_conn[24m;
returns the status of an ICE connection. The possible
return values are:
+o - the connection is not valid yet (that is, authentica-
tion is taking place). This is only relevant to
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[1mInter-Client Exchange Library X11, Release 6.4[0m
connections created by
+o - the connection has been accepted. This is only rele-
vant to connections created by
+o - the connection had been rejected (that is, authenti-
cation failed). This is only relevant to connections
created by
+o - an IO error has occurred on the connection.
__
|| char *IceVendor([4mice_conn[24m)
||__ IceConn [4mice_conn[24m;
returns the ICE library vendor identification for the other
side of the connection. The string should be freed with a
call to when no longer needed.
__
|| char *IceRelease([4mice_conn[24m)
||__ IceConn [4mice_conn[24m;
returns the release identification of the ICE library on the
other side of the connection. The string should be freed
with a call to when no longer needed.
__
|| int IceProtocolVersion([4mice_conn[24m)
||__ IceConn [4mice_conn[24m;
returns the major version of the ICE protocol on this con-
nection.
__
|| int IceProtocolRevision([4mice_conn[24m)
||__ IceConn [4mice_conn[24m;
returns the minor version of the ICE protocol on this con-
nection.
__
|| int IceConnectionNumber([4mice_conn[24m)
||__ IceConn [4mice_conn[24m;
returns the file descriptor of this ICE connection.
__
|| char *IceConnectionString([4mice_conn[24m)
||__ IceConn [4mice_conn[24m;
returns the network ID of the client that accepted this con-
nection. The string should be freed with a call to when no
longer needed.
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[1mInter-Client Exchange Library X11, Release 6.4[0m
__
|| unsigned long IceLastSentSequenceNumber([4mice_conn[24m)
||__ IceConn [4mice_conn[24m;
returns the sequence number of the last message sent on this
ICE connection.
__
|| unsigned long IceLastReceivedSequenceNumber([4mice_conn[24m)
||__ IceConn [4mice_conn[24m;
returns the sequence number of the last message received on
this ICE connection.
__
|| Bool IceSwapping([4mice_conn[24m)
||__ IceConn [4mice_conn[24m;
returns if byte swapping is necessary when reading messages
on the ICE connection.
__
|| IcePointer IceGetContext([4mice_conn[24m)
||__ IceConn [4mice_conn[24m;
returns the context associated with a connection created by
[1m12. ICE Messages[0m
All ICE messages have a standard 8-byte header. The ICElib
macros that read and write messages rely on the following
naming convention for message headers:
CARD8major_opcode; CARD8minor_opcode;
CARD8data[2]; CARD32length B32;
The 3rd and 4th bytes of the message header can be used as
needed. The length field is specified in units of 8 bytes.
[1m12.1. Sending ICE Messages[0m
The ICE library maintains an output buffer used for generat-
ing messages. Protocol libraries layered on top of ICE may
choose to batch messages together and flush the output
buffer at appropriate times.
If an IO error has occurred on an ICE connection, all write
operations will be ignored. For further information, see
section 13, ``Error Handling.''
To get the size of the ICE output buffer, use
__
|| int IceGetOutBufSize([4mice_conn[24m)
IceConn [4mice_conn[24m;
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[4mice_conn[24m A valid ICE connection object.
||__
To flush the ICE output buffer, use
__
|| IceFlush([4mice_conn[24m)
IceConn [4mice_conn[24m;
[4mice_conn[24m A valid ICE connection object.
||__
Note that the output buffer may be implicitly flushed if
there is insufficient space to generate a message.
The following macros can be used to generate ICE messages:
__
|| IceGetHeader([4mice_conn[24m, [4mmajor_opcode[24m, [4mminor_opcode[24m,
[4mheader_size[24m, [4m<C_data_type>[24m, [4mpmsg[24m)
IceConn [4mice_conn[24m;
int [4mmajor_opcode[24m;
int [4mminor_opcode[24m;
int [4mheader_size[24m;
<C_data_type> *[4mpmsg[24m;
[4mice_conn[24m A valid ICE connection object.
[4mmajor_opcode[0m
The major opcode of the message.
[4mminor_opcode[0m
The minor opcode of the message.
[4mheader_size[0m
The size of the message header (in bytes).
[4m<C_data_type>[0m
The actual C data type of the message header.
[4mpmsg[24m The message header pointer. After this macro is
called, the library can store data in the message
header.
||__
is used to set up a message header on an ICE connection. It
sets the major and minor opcodes of the message, and ini-
tializes the message's length to the length of the header.
If additional variable length data follows, the message's
length field should be updated.
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__
|| IceGetHeaderExtra([4mice_conn[24m, [4mmajor_opcode[24m, [4mminor_opcode[24m,
[4mheader_size[24m, [4mextra[24m, [4m<C_data_type>[24m, [4mpmsg[24m, [4mpdata[24m)
IceConn [4mice_conn[24m;
int [4mmajor_opcode[24m;
int [4mminor_opcode[24m;
int [4mheader_size[24m;
int [4mextra[24m;
<C_data_type> *[4mpmsg[24m;
char *[4mpdata[24m;
[4mice_conn[24m A valid ICE connection object.
[4mmajor_opcode[0m
The major opcode of the message.
[4mminor_opcode[0m
The minor opcode of the message.
[4mheader_size[0m
The size of the message header (in bytes).
[4mextra[24m The size of the extra data beyond the header (in
8-byte units).
[4m<C_data_type>[0m
The actual C data type of the message header.
[4mpmsg[24m The message header pointer. After this macro is
called, the library can store data in the message
header.
[4mpdata[24m Returns a pointer to the ICE output buffer that
points immediately after the message header. The
variable length data should be stored here. If
there was not enough room in the ICE output
buffer, pdata is set to NULL.
||__
is used to generate a message with a fixed (and relatively
small) amount of variable length data. The complete message
must fit in the ICE output buffer.
__
|| IceSimpleMessage([4mice_conn[24m, [4mmajor_opcode[24m, [4mminor_opcode[24m)
IceConn [4mice_conn[24m;
int [4mmajor_opcode[24m;
int [4mminor_opcode[24m;
[4mice_conn[24m A valid ICE connection object.
[4mmajor_opcode[0m
The major opcode of the message.
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[4mminor_opcode[0m
The minor opcode of the message.
||__
is used to generate a message that is identical in size to
the ICE header message, and has no additional data.
__
|| IceErrorHeader([4mice_conn[24m, [4moffending_major_opcode[24m, [4moffend-[0m
[4ming_minor_opcode[24m, [4moffending_sequence_num[24m,
[4mseverity[24m, [4merror_class[24m, [4mdata_length[24m)
IceConn [4mice_conn[24m;
int [4moffending_major_opcode[24m;
int [4moffending_minor_opcode[24m;
int [4moffending_sequence_num[24m;
int [4mseverity[24m;
int [4merror_class[24m;
int [4mdata_length[24m;
[4mice_conn[24m A valid ICE connection object.
[4moffending_major_opcode[0m
The major opcode of the protocol in which an error
was detected.
[4moffending_minor_opcode[0m
The minor opcode of the protocol in which an error
was detected.
[4moffending_sequence_num[0m
The sequence number of the message that caused the
error.
[4mseverity[24m or
[4merror_class[0m
The error class.
[4mdata_length[0m
Length of data (in 8-byte units) to be written
after the header.
||__
sets up an error message header.
Note that the two clients connected by ICE may be using dif-
ferent major opcodes for a given protocol. The offend-
ing_major_opcode passed to this macro is the major opcode of
the protocol for the client sending the error message.
Generic errors, which are common to all protocols, have
classes in the range 0x8000..0xFFFF. See the [4mInter-Client[0m
[4mExchange[24m [4mProtocol[24m standard for more details.
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lw(1i) lw(1i). T{ T} T{ 0x8000 T}
T{ T} T{ 0x8001 T}
T{ T} T{ 0x8002 T}
T{ T} T{ 0x8003 T}
Per-protocol errors have classes in the range 0x0000-0x7fff.
To write data to an ICE connection, use the macro. If the
data fits into the ICE output buffer, it is copied there.
Otherwise, the ICE output buffer is flushed and the data is
directly sent.
This macro is used in conjunction with and
__
|| IceWriteData([4mice_conn[24m, [4mbytes[24m, [4mdata[24m)
IceConn [4mice_conn[24m;
int [4mbytes[24m;
char *[4mdata[24m;
[4mice_conn[24m A valid ICE connection object.
[4mbytes[24m The number of bytes to write.
[4mdata[24m The data to write.
||__
To write data as 16-bit quantities, use
__
|| IceWriteData16([4mice_conn[24m, [4mbytes[24m, [4mdata[24m)
IceConn [4mice_conn[24m;
int [4mbytes[24m;
short *[4mdata[24m;
[4mice_conn[24m A valid ICE connection object.
[4mbytes[24m The number of bytes to write.
[4mdata[24m The data to write.
||__
To write data as 32-bit quantities, use
__
|| IceWriteData32([4mice_conn[24m, [4mbytes[24m, [4mdata[24m)
IceConn [4mice_conn[24m;
int [4mbytes[24m;
long *[4mdata[24m;
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[4mice_conn[24m A valid ICE connection object.
[4mbytes[24m The number of bytes to write.
[4mdata[24m The data to write.
||__
To bypass copying data to the ICE output buffer, use to
directly send data over the network connection. If neces-
sary, the ICE output buffer is first flushed.
__
|| IceSendData([4mice_conn[24m, [4mbytes[24m, [4m(char[24m [4m*)[24m [4mdata[24m)
IceConn [4mice_conn[24m;
int [4mbytes[24m;
char *[4mdata[24m;
[4mice_conn[24m A valid ICE connection object.
[4mbytes[24m The number of bytes to send.
[4mdata[24m The data to send.
||__
To force 32-bit or 64-bit alignment, use A maximum of 7 pad
bytes can be specified.
__
|| IceWritePad([4mice_conn[24m, [4mbytes[24m)
IceConn [4mice_conn[24m;
int [4mbytes[24m;
[4mice_conn[24m A valid ICE connection object.
[4mbytes[24m The number of pad bytes.
||__
[1m12.2. Reading ICE Messages[0m
The ICE library maintains an input buffer used for reading
messages. If the ICE library chooses to perform nonblocking
reads (this is implementation-dependent), then for every
read operation that it makes, zero or more complete messages
may be read into the input buffer. As a result, for all of
the macros described in this section that read messages, an
actual read operation will occur on the connection only if
the data is not already present in the input buffer.
To get the size of the ICE input buffer, use
__
|| int IceGetInBufSize([4mice_conn[24m)
IceConn [4mice_conn[24m;
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[4mice_conn[24m A valid ICE connection object.
||__
When reading messages, care must be taken to check for IO
errors. If any IO error occurs in reading any part of a
message, the message should be thrown out. After using any
of the macros described below for reading messages, the
macro can be used to check if an IO error occurred on the
connection. After an IO error has occurred on an ICE con-
nection, all read operations will be ignored. For further
information, see section 13, ``Error Handling.''
__
|| Bool IceValidIO([4mice_conn[24m)
IceConn [4mice_conn[24m;
||__
The following macros can be used to read ICE messages.
__
|| IceReadSimpleMessage([4mice_conn[24m, [4m<C_data_type>[24m, [4mpmsg[24m)
IceConn [4mice_conn[24m;
<C_data_type> *[4mpmsg[24m;
[4mice_conn[24m A valid ICE connection object.
[4m<C_data_type>[0m
The actual C data type of the message header.
[4mpmsg[24m This pointer is set to the message header.
||__
is used for messages that are identical in size to the
8-byte ICE header, but use the spare 2 bytes in the header
to encode additional data. Note that the ICE library always
reads in these first 8 bytes, so it can obtain the major
opcode of the message. simply returns a pointer to these 8
bytes; it does not actually read any data into the input
buffer.
For a message with variable length data, there are two ways
of reading the message. One method involves reading the
complete message in one pass using The second method
involves reading the message header (note that this may be
larger than the 8-byte ICE header), then reading the vari-
able length data in chunks (see and
__
|| IceReadCompleteMessage([4mice_conn[24m, [4mheader_size[24m, [4m<C_data_type>[24m,
[4mpmsg[24m, [4mpdata[24m)
IceConn [4mice_conn[24m;
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int [4mheader_size[24m;
<C_data_type> *[4mpmsg[24m;
char *[4mpdata[24m;
[4mice_conn[24m A valid ICE connection object.
[4mheader_size[0m
The size of the message header (in bytes).
[4m<C_data_type>[0m
The actual C data type of the message header.
[4mpmsg[24m This pointer is set to the message header.
[4mpdata[24m This pointer is set to the variable length data of
the message.
||__
If the ICE input buffer has sufficient space, will read the
complete message into the ICE input buffer. Otherwise, a
buffer will be allocated to hold the variable length data.
After the call, the pdata argument should be checked against
NULL to make sure that there was sufficient memory to allo-
cate the buffer.
After calling and processing the message, should be called.
__
|| IceDisposeCompleteMessage([4mice_conn[24m, [4mpdata[24m)
IceConn [4mice_conn[24m;
char *[4mpdata[24m;
[4mice_conn[24m A valid ICE connection object.
[4mpdata[24m The pointer to the variable length data returned
in
||__
If a buffer had to be allocated to hold the variable length
data (because it did not fit in the ICE input buffer), it is
freed here by ICElib.
__
|| IceReadMessageHeader([4mice_conn[24m, [4mheader_size[24m, [4m<C_data_type>[24m,
[4mpmsg[24m)
IceConn [4mice_conn[24m;
int [4mheader_size[24m;
<C_data_type> *[4mpmsg[24m;
[4mice_conn[24m A valid ICE connection object.
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[4mheader_size[0m
The size of the message header (in bytes).
[4m<C_data_type>[0m
The actual C data type of the message header.
[4mpmsg[24m This pointer is set to the message header.
||__
reads just the message header. The rest of the data should
be read with the family of macros. This method of reading a
message should be used when the variable length data must be
read in chunks.
To read data directly into a user supplied buffer, use
__
|| IceReadData([4mice_conn[24m, [4mbytes[24m, [4mpdata[24m)
IceConn [4mice_conn[24m;
int [4mbytes[24m;
char *[4mpdata[24m;
[4mice_conn[24m A valid ICE connection object.
[4mbytes[24m The number of bytes to read.
[4mpdata[24m The data is read into this user supplied buffer.
||__
To read data as 16-bit quantities, use
__
|| IceReadData16([4mice_conn[24m, [4mswap[24m, [4mbytes[24m, [4mpdata[24m)
IceConn [4mice_conn[24m;
Bool [4mswap[24m;
int [4mbytes[24m;
short *[4mpdata[24m;
[4mice_conn[24m A valid ICE connection object.
[4mswap[24m If the values will be byte swapped.
[4mbytes[24m The number of bytes to read.
[4mpdata[24m The data is read into this user supplied buffer.
||__
To read data as 32-bit quantities, use
__
|| IceReadData32([4mice_conn[24m, [4mswap[24m, [4mbytes[24m, [4mpdata[24m)
IceConn [4mice_conn[24m;
Bool [4mswap[24m;
int [4mbytes[24m;
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long *[4mpdata[24m;
[4mice_conn[24m A valid ICE connection object.
[4mswap[24m If the values will be byte swapped.
[4mbytes[24m The number of bytes to read.
[4mpdata[24m The data is read into this user supplied buffer.
||__
To force 32-bit or 64-bit alignment, use A maximum of 7 pad
bytes can be specified.
__
|| IceReadPad([4mice_conn[24m, [4mbytes[24m)
IceConn [4mice_conn[24m;
int [4mbytes[24m;
[4mice_conn[24m A valid ICE connection object.
[4mbytes[24m The number of pad bytes.
||__
[1m13. Error Handling[0m
There are two default error handlers in ICElib:
+o One to handle typically fatal conditions (for example,
a connection dying because a machine crashed)
+o One to handle ICE-specific protocol errors
These error handlers can be changed to user-supplied rou-
tines if you prefer your own error handling and can be
changed as often as you like.
To set the ICE error handler, use
__
|| IceErrorHandler IceSetErrorHandler([4mhandler[24m)
IceErrorHandler [4mhandler[24m;
[4mhandler[24m The ICE error handler. You should pass NULL to
restore the default handler.
||__
returns the previous error handler.
The ICE error handler is invoked when an unexpected ICE pro-
tocol error (major opcode 0) is encountered. The action of
the default handler is to print an explanatory message to
and if the severity is fatal, call with a nonzero value. If
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exiting is undesirable, the application should register its
own error handler.
Note that errors in other protocol domains should be handled
by their respective libraries (these libraries should have
their own error handlers).
An ICE error handler has the type of
__
|| typedef void (*IceErrorHandler)();
void ErrorHandler([4mice_conn[24m, [4mswap[24m, [4moffending_minor_opcode[24m,
[4moffending_sequence_num[24m, [4merror_class[24m,
[4mseverity[24m, [4mvalues[24m)
IceConn [4mice_conn[24m;
Bool [4mswap[24m;
int [4moffending_minor_opcode[24m;
unsigned long [4moffending_sequence_num[24m;
int [4merror_class[24m;
int [4mseverity[24m;
IcePointer [4mvalues[24m;
[4mice_conn[24m The ICE connection object.
[4mswap[24m A flag that indicates if the values need byte
swapping.
[4moffending_minor_opcode[0m
The ICE minor opcode of the offending message.
[4moffending_sequence_num[0m
The sequence number of the offending message.
[4merror_class[0m
The error class of the offending message.
[4mseverity[24m or
[4mvalues[24m Any additional error values specific to the minor
opcode and class.
||__
The following error classes are defined at the ICE level:
For further information, see the [4mInter-Client[24m [4mExchange[24m [4mPro-[0m
[4mtocol[24m standard.
To handle fatal I/O errors, use
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__
|| IceIOErrorHandler IceSetIOErrorHandler([4mhandler[24m)
IceIOErrorHandler [4mhandler[24m;
[4mhandler[24m The I/O error handler. You should pass NULL to
restore the default handler.
||__
returns the previous IO error handler.
An ICE I/O error handler has the type of
__
|| typedef void (*IceIOErrorHandler)();
void IOErrorHandler([4mice_conn[24m)
IceConn [4mice_conn[24m;
[4mice_conn[24m The ICE connection object.
||__
There are two ways of handling IO errors in ICElib:
+o In the first, the IO error handler does whatever is
necessary to respond to the IO error and then returns,
but it does not call The ICE connection is given a
``bad IO'' status, and all future reads and writes to
the connection are ignored. The next time is called it
will return a status of At that time, the application
should call
+o In the second, the IO error handler does call and then
uses the call to get back to the application's main
event loop. The and calls may not work properly on all
platforms, and special care must be taken to avoid mem-
ory leaks. Therefore, this second model is less desir-
able.
Before the application I/O error handler is invoked, proto-
col libraries that were interested in being notified of I/O
errors will have their handlers invoked. This handler is
set up in the protocol registration functions (see and and
could be used to clean up state specific to the protocol.
__
|| typedef void (*IceIOErrorProc)();
void IOErrorProc([4mice_conn[24m)
IceConn [4mice_conn[24m;
[4mice_conn[24m The ICE connection object.
||__
Note that every callback must return. This is required
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because each active protocol must be notified of the broken
connection, and the application IO error handler must be
invoked afterwards.
[1m14. Multi-Threading Support[0m
To declare that multiple threads in an application will be
using the ICE library, use
__
|| Status IceInitThreads()
||__
The function must be the first ICElib function a multi-
threaded program calls. It must complete before any other
ICElib call is made. returns a nonzero status if and only
if it was able to initialize the threads package success-
fully. It is safe to call more than once, although the
threads package will only be initialized once.
Protocol libraries layered on top of ICElib will have to
lock critical sections of code that access an ICE connection
(for example, when generating messages). Two calls, which
are generally implemented as macros, are provided:
__
|| IceLockConn([4mice_conn[24m)
IceConn [4mice_conn[24m;
IceUnlockConn([4mice_conn[24m)
IceConn [4mice_conn[24m;
[4mice_conn[24m The ICE connection.
||__
To keep an ICE connection locked across several ICElib
calls, applications use and
__
|| void IceAppLockConn([4mice_conn[24m)
IceConn [4mice_conn[24m;
[4mice_conn[24m The ICE connection to lock.
||__
The function completely locks out other threads using the
connection until is called. Other threads attempting to use
ICElib calls on the connection will block. If the program
has not previously called has no effect.
__
|| void IceAppUnlockConn([4mice_conn[24m)
IceConn [4mice_conn[24m;
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[4mice_conn[24m The ICE connection to unlock.
||__
The function allows other threads to complete ICElib calls
on the connection that were blocked by a previous call to
from this thread. If the program has not previously called
has no effect.
[1m15. Miscellaneous Functions[0m
To allocate scratch space (for example, when generating mes-
sages with variable data), use Each ICE connection has one
scratch space associated with it. The scratch space starts
off as empty and grows as needed. The contents of the
scratch space is not guaranteed to be preserved after any
ICElib function is called.
__
|| char *IceAllocScratch([4mice_conn[24m, [4msize[24m)
IceConn [4mice_conn[24m;
unsigned long [4msize[24m;
[4mice_conn[24m A valid ICE connection object.
[4msize[24m The number of bytes required.
||__
Note that the memory returned by should not be freed by the
caller. The ICE library will free the memory when the ICE
connection is closed.
[1m16. Acknowledgements[0m
Thanks to Bob Scheifler for his thoughtful input on the
design of the ICE library. Thanks also to Jordan Brown,
Larry Cable, Donna Converse, Clive Feather, Stephen Gildea,
Vania Joloboff, Kaleb Keithley, Stuart Marks, Hiro Miyamoto,
Ralph Swick, Jim VanGilder, and Mike Wexler.
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[1mAppendix A[0m
[1mAuthentication Utility Functions[0m
As discussed in this document, the means by which authenti-
cation data is obtained by the ICE library (for messages or
messages) is implementation-dependent.
This appendix describes some utility functions that manipu-
late an ICE authority file. The authority file can be used
to pass authentication data between clients.
The basic operations on the .ICEauthority file are:
+o Get file name
+o Lock
+o Unlock
+o Read entry
+o Write entry
+o Search for entry
These are fairly low-level operations, and it is expected
that a program, like "iceauth", would exist to add, remove,
and display entries in the file.
In order to use these utility functions, the header file
must be included.
An entry in the .ICEauthority file is defined by the follow-
ing data structure:
__
|| typedef struct { char *protocol_name; unsigned
short protocol_data_length; char *protocol_data;
char *network_id; char *auth_name; unsigned
short auth_data_length; char *auth_data; } IceAuth-
FileEntry;
||__
The protocol_name member is either ``ICE'' for connection
setup authentication or the subprotocol name, such as
``XSMP''. For each entry, protocol specific data can be
specified in the protocol_data member. This can be used to
search for old entries that need to be removed from the
file.
-----------
The X Consortium's ICElib implementation
assumes the presence of an ICE authority file.
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The network_id member is the network ID of the client
accepting authentication (for example, the network ID of a
session manager). A network ID has the following form:
lw(0.25i) lw(2.5i) lw(1i). tcp/<hostname>:<portnum-
ber> or decnet/<hostname>::<objname> or
local/<hostname>:<path>
The auth_name member is the name of the authentication
method. The auth_data member is the actual authentication
data, and the auth_data_length member is the number of bytes
in the data.
To obtain the default authorization file name, use
__
|| char *IceAuthFileName()
||__
If the ICEAUTHORITY environment variable if set, this value
is returned. Otherwise, the default authorization file name
is $HOME/.ICEauthority. This name is statically allocated
and should not be freed.
To synchronously update the authorization file, the file
must be locked with a call to This function takes advantage
of the fact that the system call will fail if the name of
the new link already exists.
__
|| int IceLockAuthFile([4mfile_name[24m, [4mretries[24m, [4mtimeout[24m, [4mdead[24m)
char *[4mfile_name[24m;
int [4mretries[24m;
int [4mtimeout[24m;
long [4mdead[24m;
[4mfile_name[24m The authorization file to lock.
[4mretries[24m The number of retries.
[4mtimeout[24m The number of seconds before each retry.
[4mdead[24m If a lock already exists that is the specified
dead seconds old, it is broken. A value of zero
is used to unconditionally break an old lock.
||__
One of three values is returned:
+o - the lock succeeded.
+o - a system error occurred, and may prove useful.
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+o - the specified number of retries failed.
To unlock an authorization file, use
__
|| void IceUnlockAuthFile([4mfile_name[24m)
char *[4mfile_name[24m;
[4mfile_name[24m The authorization file to unlock.
||__
To read the next entry in an authorization file, use
__
|| IceAuthFileEntry *IceReadAuthFileEntry([4mauth_file[24m)
FILE *[4mauth_file[24m;
[4mauth_file[24m The authorization file.
||__
Note that it is the responsibility of the application to
open the file for reading before calling this function. If
an error is encountered, or there are no more entries to
read, NULL is returned.
Entries should be free with a call to
To write an entry in an authorization file, use
__
|| Status IceWriteAuthFileEntry([4mauth_file[24m, [4mentry[24m)
FILE *[4mauth_file[24m;
IceAuthFileEntry *[4mentry[24m;
[4mauth_file[24m The authorization file.
[4mentry[24m The entry to write.
||__
Note that it is the responsibility of the application to
open the file for writing before calling this function. The
function returns a nonzero status if the operation was suc-
cessful.
To search the default authorization file for an entry that
matches a given protocol_name/network_id/auth_name tuple,
use
__
|| IceAuthFileEntry *IceGetAuthFileEntry([4mprotocol_name[24m, [4mnet-[0m
[4mwork_id[24m, [4mauth_name[24m)
char *[4mprotocol_name[24m;
char *[4mnetwork_id[24m;
char *[4mauth_name[24m;
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[1mInter-Client Exchange Library X11, Release 6.4[0m
[4mprotocol_name[0m
The name of the protocol to search on.
[4mnetwork_id[0m
The network ID to search on.
[4mauth_name[24m The authentication method to search on.
||__
If fails to find such an entry, NULL is returned.
To free an entry returned by or use
__
|| void IceFreeAuthFileEntry([4mentry[24m)
IceAuthFileEntry *[4mentry[24m;
[4mentry[24m The entry to free.
||__
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[1mAppendix B[0m
[1mMIT-MAGIC-COOKIE-1 Authentication[0m
The X Consortium's ICElib implementation supports a simple
MIT-MAGIC-COOKIE-1 authentication scheme using the authority
file utilities described in Appendix A.
In this model, an application, such as a session manager,
obtains a magic cookie by calling and then stores it in the
user's local .ICEauthority file so that local clients can
connect. In order to allow remote clients to connect, some
remote execution mechanism should be used to store the magic
cookie in the user's .ICEauthority file on a remote machine.
In addition to storing the magic cookie in the .ICEauthority
file, the application needs to call the function in order to
store the magic cookie in memory. When it comes time for
the MIT-MAGIC-COOKIE-1 authentication procedure to accept or
reject the connection, it will compare the magic cookie pre-
sented by the requestor to the magic cookie in memory.
__
|| char *IceGenerateMagicCookie([4mlength[24m)
int [4mlength[24m;
[4mlength[24m The desired length of the magic cookie.
||__
The magic cookie returned will be null-terminated. If mem-
ory can not be allocated for the magic cookie, the function
will return NULL. Otherwise, the magic cookie should be
freed with a call to
To store the authentication data in memory, use Currently,
this function is only used for MIT-MAGIC-COOKIE-1 authenti-
cation, but it may be used for additional authentication
methods in the future.
__
|| void IceSetPaAuthData([4mnum_entries[24m, [4mentries[24m)
int [4mnum_entries[24m;
IceAuthDataEntry *[4mentries[24m;
[4mnum_entries[0m
The number of authentication data entries.
[4mentries[24m The list of authentication data entries.
||__
Each entry has associated with it a protocol name (for exam-
ple, ``ICE'' for ICE connection setup authentication,
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``XSMP'' for session management authentication), a network
ID for the ``accepting'' client, an authentication name (for
example, MIT-MAGIC-COOKIE-1), and authentication data. The
ICE library will merge these entries with previously set
entries, based on the (protocol_name, network_id, auth_name)
tuple.
__
|| typedef struct { char *protocol_name; char *net-
work_id; char *auth_name; unsigned short
auth_data_length; char *auth_data; } IceAuthDataEntry;
||__
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