saf@CITI.UMICH.EDU (10/07/87)
UDP DRIVER INTERFACE SPECIFICATION (Final Draft, 10/6/87)
ABOUT THE UDP DRIVER
--------------------
The UDP driver layer, one of the CITI MacIP drivers, implements the User Datagram
Protocol [RFC 768]. This document describes the interface to UDP.
UDP DATA STRUCTURES
-------------------
The reader should be familiar with the common C derived types, such as those described in
<sys/types.h>, <sys/time.h>, MPW C, and Inside Macintosh.
Clients are given the option of writing data from a character array or from a Write Data
Structure (WDS). The WDS is a "gather write" structure. It specifies a list and ordering of
buffers to write in a single operation.
Within the WDS, wds_index is an index into an array of buffer descriptors, pointing to the
first buffer to write. UDP clients must pass wds_index as 3 or more, and allocate the
corresponding buffer descriptors. The first three buffer descriptors will be used by lower
level protocols for protocol headers. Terminate the buffer descriptor array with a descriptor
specifying length zero.
typedef struct bd { /* Buffer descriptor */
unsigned short bl; /* Buffer length */
Ptr bp; /* Buffer pointer */
} bd_t, *bd_p;
typedef struct wds { /* Write data structure */
unsigned long wds_index; /* Current descriptor index */
bd_t wds_buffer[]; /* List of descriptors */
} wds_t, *wds_p;
The following is a sample WDS. wds_index is 3, so the first buffer descriptor is
wds_buffer[3]. Descriptors wds_buffer[0], wds_buffer[1], and wds_buffer[2]
will be used for lower layer protocol headers. DATA LEN and DATA PTR are the length
of and a pointer to the client's buffer. This example shows the minimal WDS for UDP
clients.
+-----------------------+
| 3 | wds_index (long)
+-----------------------+
| | buffer length #0 (word)
+-----------------------+
| | buffer pointer #0 (pointer)
+-----------------------+
| | buffer length #1 (word)
+-----------------------+
| | buffer pointer #1 (pointer)
+-----------------------+
| | buffer length #2 (word)
+-----------------------+
| | buffer pointer #2 (pointer)
+-----------------------+
| DATA LEN | buffer length #3 (word)
+-----------------------+
| DATA PTR | buffer pointer #3 (pointer)
+-----------------------+
| 0 | buffer length #4 (word)
+-----------------------+
| UNUSED | buffer pointer #4 (pointer)
+-----------------------+
.
.
.
Version information on the UDP driver is returned in the following
structure:
typedef struct udp_version {
unsigned char version[32]; /* Version number */
unsigned char specdesc[32]; /* Specification description */
unsigned char site[32]; /* Originating site */
} udp_version_t, *udp_version_p;
If UDP is configured to collect statistics, that information is returned in the following
structure (NOTE: this structure is not finalized!):
typedef struct udp_stats { /* Not yet defined */
} udp_stats_t, *udp_stats_p;
UDP FUNCTIONS
-------------
The following functions provide a program interface to the UDP driver layer. Each
function returns success (0) or an error code. Error code identifiers are defined in
net_errno.h. The return type for all functions is long.
UDP may notify clients of asynchronous events by executing a client-supplied notification
routine. Execution of the notification routine is called delivery of notification. Clients are
notified of an event if and only if they have specifically requested notification of that event.
Clients request and cancel notification of events by setting a mask and passing it to
udp_request and udp_cancel, respectively.
Some functions accept io_timeout as a parameter. For these routines, if io_timeout is
NULL, the function blocks forever, or until the call can be completed. If io_timeout is
not NULL, the function blocks until the timeout value expires or the call can be completed.
Implementation-dependent restrictions may apply as to when a client can block. If it is
illegal for a call to block, the error E_CANTBLOCK is returned.
Some functions accept (and in certain cases return) io_flags as a parameter. io_flags is
a long-word bitmask of control flags. A list of all flags is given in "UDPJCONSTANTS."
Right and left arrows indicate values passed to and from the driver functions, respectively.
udp_create (io_stream, io_lport)
<- Ptr *io_stream UDP stream descriptor
-> unsigned short io_lport Local UDP port
udp_create creates a UDP stream. If io_lport is non-zero, the local port is set in
io_stream, otherwise, a subsequent call to udp_setport must set the local port. Once the
local port is set, the stream can be used to send and receive datagrams.
Errors returned are:
E_NOMEM
E_PORTINUSE
udp_delete (io_stream)
-> Ptr io_stream UDP stream descriptor
udp_delete deletes a UDP stream. Outstanding datagram buffers are deallocated and
pending events are flushed.
Errors returned are:
E_BADSTREAM
udp_setport (io_stream, io_lport)
-> Ptr io_stream UDP stream descriptor
-> unsigned short *io_lport Local UDP port
udp_setport sets the port for a UDP stream. The UDP driver retains the binding of a
stream to a port, so that incoming datagrams can be delivered to the proper stream and
outbound datagrams show the correct address. If io_lport is zero, the driver will assign
an unused port.
Errors returned are:
E_BADSTREAM
E_PORTINUSE
udp_request (io_stream, io_nclass, io_notify, io_userdata, io_flags)
-> Ptr io_stream UDP stream descriptor
-> unsigned long io_nclass Set of events to notify on
-> ProcPtr io_notify Notification routine
-> unsigned long io_userdata Passed to notification routine
-> unsigned long io_flags Control flags
udp_request sets up notification for a stream. io_notify is a pointer to the client's
notification routine. io_userdata is passed to the client's notification routine.
io_nclass is the bitwise or of the notification identifiers to notify on. So that clients may
request to add to current notifications, io_nclass is bitwise ored to the existing bits.
Values for io_nclass are defined in the section "UDPJNOTIFICATION." When a UDP
stream is created, the default value for io_nclass is UDP_NT_NONE (i.e., no notification).
Special behavior can be specified with io_flags. The following flags are defined:
UDP_FLAG_NEWNOTIFY io_notify should replace the previous io_notify. Clients
may disable notification by passing NULL for io_notify
and setting this flag. Notification may be re-enabled later by
setting IP_FLAG_NEWNOTIFY and io_notify .
UDP_FLAG_NEWUDATA io_userdata should replace the previous io_userdata.
Errors returned are:
E_BADSTREAM
E_BADNOTIFICATION
E_BADFLAG
udp_cancel (io_stream, io_nclass)
-> Ptr io_stream UDP stream descriptor
-> unsigned long io_nclass Events not to notify on
udp_cancel subtracts from the set of events for which the client accepts notification.
io_nclass is the bitwise or of the notification identifiers to subtract, specified in
"UDPJNOTIFICATION."
Errors returned are:
E_BADSTREAM
E_BADNOTIFICATION
udp_alloc (io_stream, io_buffer, io_buflen)
-> Ptr io_stream UDP stream descriptor
<- Ptr *io_buffer Pointer to a datagram buffer
-> unsigned long io_buflen Requested buffer length
udp_alloc allocates a UDP buffer, returning io_buffer, a pointer to a datagram buffer .
Errors returned are:
E_BADSTREAM
E_NOMEM
udp_free (io_stream, io_buffer)
-> Ptr io_stream UDP stream descriptor
-> Ptr io_buffer Pointer to a datagram buffer
udp_free frees a UDP datagram buffer. io_buffer must point to a datagram buffer
allocated by udp_alloc or udp_get.
Errors returned are:
E_BADSTREAM
E_BADPTR
udp_put (io_stream, io_buffer, io_buflen, io_fhost, io_fport, io_flags)
-> Ptr io_stream UDP stream descriptor
-> Ptr io_buffer Output buffer
-> unsigned long io_buflen Buffer length (bytes)
-> unsigned long io_fhost Destination host
-> unsigned short io_fport UDP port on io_fhost
-> unsigned long io_flags Control flags
udp_put sends a datagram on the stream specified by io_stream. io_buffer is a
datagram buffer. If the flag UDP_FLAG_USEWDS is not set (see below), clients must allocate
io_buffer by calling udp_alloc and free them by calling udp_free.
Before calling udp_put, the client must bind io_lport, either in udp_create or
udp_setport. The destination host and port, passed in io_fhost and io_fport,
respectively, must be non-zero.
Special behavior can be specified with io_flags. The following flags are defined:
UDP_FLAG_MAKESUM If set, a UDP checksum will be computed and included in
the UDP header of the outgoing datagram, otherwise the
checksum will be set to zero.
UDP_FLAG_USEWDS If set, io_buffer is a pointer into a client-allocated WDS
(i.e., type wds_p). The client must allocate the structure,
leaving room for lower layer protocol headers, as specified
in the section "UDPJDATAJSTRUCTURES."
Note that if UDP_FLAG_USEWDS is set, datagram buffers need
not be allocated and freed with udp_alloc and udp_free.
Also, io_buflen is ignored.
Errors returned are:
E_BADSTREAM
E_BADWDS
E_BADFLAG
E_NOMEM
E_DTGTOOBIG
E_CANTRESOLVEADDR
E_HWWRITEERR
udp_get (io_stream, io_buffer, io_buflen, io_fhost, io_lhost io_fport,
io_lhost, io_timeout, io_flags)
-> Ptr io_stream UDP stream descriptor
<- Ptr *io_buffer Input buffer
<> unsigned long io_buflen Input buffer length (bytes)
<- unsigned long *io_fhost Foreign host
<- unsigned short *io_fport UDP port on io_fhost
<- unsigned long *io_lhost Local host
<- unsigned short *io_lport UDP port on io_lhost
-> struct timeval *io_timeout Timeout value
<> unsigned long *io_flags Control flags
udp_get requests a buffer from a UDP stream. Note that io_buffer is allocated by the
driver, but should be freed by the client (see udp_free).
If io_timeout is NULL, udp_get blocks until a datagram arrives. If io_timeout is not
NULL and a datagram is not available within the timeout period, udp_get returns an error.
Before calling udp_get, the client must bind io_lport, either in udp_create or
udp_setport.
For the parameters io_fhost, io_fport, io_lhost, io_lport, and io_flags, the client
may pass NULL if it does not need the returned values.
No values are currently defined for io_flags.
Errors returned are:
E_BADSTREAM
E_TIMEDOUT
E_CANTBLOCK
udp_control (io_stream, io_buffer, io_buflen, io_control)
-> Ptr io_stream UDP stream descriptor
<> Ptr io_buffer Data used by control call
<> unsigned long *io_buflen Size of io_buffer (bytes)
-> unsigned long io_control Specifies control operation
udp_control performs various operations for a UDP stream. io_control selects an
operation and is the only mandatory parameter. Parameters that are not required by
individual control operations may be passed as NULL.
General errors returned by udp_control are:
E_BADSTREAM
E_BADCONTROL
Currently defined control operations are:
UDP_CTL_VERSION
-> io_stream UDP stream descriptor
<> io_buffer Pointer to udp_version_t structure
-> io_control Control operation
Returns version information. Clients pass a pointer to a structure of type
udp_version_t, as defined in the section "UDPJDATAJSTRUCTURES."
No specific errors are returned for this control.
UDP_CTL_STATS
-> io_stream UDP stream descriptor
<> io_buffer Pointer to udp_stats_t structure
-> io_control Control operation
No specific errors are returned for this control.
UDP_CTL_PERM_STREAM
-> io_stream UDP stream descriptor
-> io_control Control operation
This stream should never be deallocated by the system.
No specific errors are returned for this control.
udp_task ()
Clients should call udp_task periodically to allow UDP time for asynchronous
processing (e.g., to process incoming datagrams).
Errors returned are:
E_CANTBLOCK
UDP NOTIFICATION
----------------
Clients may request and cancel notification of asynchronous events by calling
udp_request and udp_cancel, respectively. As asynchronous events occur, the
notification routine io_notify is called with the following parameters:
(*io_notify)(io_stream, io_buffer, io_buflen, io_fhost, io_fport,
io_lhost, io_lport, io_nclass, io_ndata, io_userdata)
-> Ptr io_stream
-> Ptr io_buffer
-> unsigned long io_buflen
-> unsigned long io_fhost
-> unsigned short io_fport
-> unsigned long io_lhost
-> unsigned short io_lport
-> unsigned long io_nclass
-> unsigned long io_ndata
-> unsigned long io_userdata
io_nclass is the type of event that caused this notification. io_userdata was passed to
udp_request by the client. io_ndata contains additional specification for the event.
The following describes the valid notification classes (io_nclass):
UDP_NT_DATA: Data Arrival Notification
-> io_stream
-> io_fhost
-> io_fport
-> io_lhost
-> io_lport
-> io_nclass
-> io_userdata
Data arrival notification is delivered when a datagram arrives on io_stream, from
io_fport on io_fhost.
UDP_NT_ERROR Error Notification
-> io_stream
-> io_buffer
-> io_buflen
-> io_fhost
-> io_fport
-> io_lhost
-> io_lport
-> io_nclass
-> io_ndata
-> io_userdata
The client is notified when an asynchronous error occurs, (e.g., destination unreachable
messages). io_ndata identifies the error. For all errors, an ICMP destination unreachable
datagram is returned in io_buffer. io_buflen is the length of that datagram. For more
information on ICMP, refer to [RFCJ792].
Errors delivered are:
E_NETUN
E_HOSTUN
E_PROTOUN
E_PORTUN
UDP ERROR CODES
---------------
Following is a description of all possible error codes returned by UDP:
E_NOMEM
Not enough memory to perform operation.
E_PORTINUSE
Port number is already in use by another client.
E_BADSTREAM
Stream descriptor was not found in this driver's list of streams.
E_BADNOTIFICATION
Invalid notification class.
E_BADFLAG
Invalid control flag bit is set in io_flags.
E_BADCONTROL
Invalid control identifier.
E_BADPTR
Invalid pointer; could not verify that pointer points to valid data.
E_BADWDS
Invalid WDS structure or pointer.
E_DTGTOOBIG
Datagram is too long to be handled by this driver.
E_CANTRESOLVEADDR
Unable to determine the next destination IP address that leads to the
requested destination IP address.
E_HWWRITEERR
Hardware failed in writing datagram to network.
E_CANTBLOCK
Current context does not allow a blocking call.
E_TIMEDOUT
Could not perform operation within requested timeout period.