saf@CITI.UMICH.EDU (10/07/87)
IP DRIVER INTERFACE SPECIFICATION (Final Draft 10/6/87)
ABOUT THE IP DRIVER
-------------------
The IP driver layer, one of the CITI MacIP drivers, implements the Internet Protocol
[RFCJ791]. This document describes the interface to IP.
IP DATA STRUCTURE
-----------------
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. IP clients must pass wds_index as 2 or more, and allocate the
corresponding buffer descriptors. The first two 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 2, so the first buffer descriptor is
wds_buffer[2]. Descriptors wds_buffer[0] and wds_buffer[1] 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 IP clients.
+-----------------------+
| 2 | wds_index (long)
+-----------------------+
| | buffer length #0 (word)
+-----------------------+
| | buffer pointer #0 (pointer)
+-----------------------+
| | buffer length #1 (word)
+-----------------------+
| | buffer pointer #1 (pointer)
+-----------------------+
| DATA LEN | buffer length #2 (word)
+-----------------------+
| DATA PTR | buffer pointer #2 (pointer)
+-----------------------+
| 0 | buffer length #3 (word)
+-----------------------+
| UNUSED | buffer pointer #3 (pointer)
+-----------------------+
.
.
.
All IP datagrams are described by an IP header [RFCJ791], described below :
typedef struct ip_header {
unsigned char ip_ver:4;
unsigned char ip_ihl:4;
unsigned char ip_tsrv;
unsigned short ip_len;
unsigned short ip_id;
unsigned short ip_flgs:3;
unsigned short ip_foff:13;
unsigned char ip_time;
unsigned char ip_prot;
unsigned short ip_chksum;
unsigned long ip_src;
unsigned long ip_dst
unsigned long ip_options;
} ip_header_t, *ip_header_p;
IP can return a list of all active local IP addresses. The list is a zero-terminated array of the
following structure:
typedef struct ip_addr {
unsigned long addr; /* IP address */
unsigned long mask; /* Net mask for IP address */
} ip_addr_t, *ip_addr_p;
Information on maximum segment size is handled with the following structure:
typedef struct ip_mss {
unsigned long addr; /* IP address */
unsigned long ob_maxpaksz; /* Max outbound IP packet size; */
/* assumes no IP options */
unsigned long ib_maxpaksz; /* Max inbound IP packet size */
unsigned long maxfragsz; /* Maximum fragment size on */
/* network; assumes no IP options */
} ip_mss_t, *ip_mss_p;
Version information on the IP driver is returned in the following structure:
typedef struct ip_version {
unsigned char version[32]; /* Version number */
unsigned char specdesc[32]; /* Specification description */
unsigned char site[32]; /* Originating site */
} ip_version_t, *ip_version_p;
If IP is configured to collect statistics, that information is returned in the following structure
(NOTE: this structure is not finalized!):
typedef struct ip_stats {
short st_drop; /* IP dtgs dropped */
short st_xsum; /* IP dtgs with bad checksums */
short st_len; /* IP dtgs with bad lengths */
short st_dest; /* IP dtgs with bad destinations */
short st_ttl; /* IP dtgs with time to live = 0 */
short st_prot; /* No server for protocol */
short st_ver; /* Bad ip version number */
short st_snd; /* # of ip datagrams sent */
short st_rcv; /* # of ip datagrams received */
short st_frag; /* # of fragments received */
short st_multi; /* # of times > 1 packet on queue */
short st_retry; /* Total # of transmission retries */
short st_retry_fail; /* Number of retry fail errors */
} ip_stats_t, *ip_stats_p;
IP FUNCTIONS
------------
The following functions provide a program interface to the IP 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.
IP 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
ip_request and ip_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 "IPJCONSTANTS."
Right and left arrows indicate values passed to and from the driver functions, respectively.
ip_create (io_stream, io_prot)
<- Ptr *io_stream IP stream descriptor
-> unsigned short io_prot Internet protocol number
ip_create creates an IP stream. On success, ip_create prepares io_stream, which
carries the private, protocol-specific description of the stream. io_prot is a protocol
number as defined in [RFCJ997].
Errors returned are:
E_NOMEM
E_PROTOINUSE
ip_delete (io_stream)
-> Ptr io_stream IP stream descriptor
ip_delete destroys an IP stream. Outstanding datagram buffers are freed and pending
events are flushed.
Errors returned are:
E_BADSTREAM
ip_request (io_stream, io_nclass, io_notify, io_userdata, io_flags)
-> Ptr io_stream IP 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
ip_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 "IPJNOTIFICATION." When an IP
stream is created, the default value for io_nclass is IP_NT_NONE (i.e., no notification).
Special behavior can be specified with io_flags. The following flags are defined:
IP_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 .
IP_FLAG_NEWUDATA io_userdata should replace the previous io_userdata.
Errors returned are:
E_BADSTREAM
E_BADNOTIFICATION
E_BADFLAG
ip_cancel (io_stream, io_nclass)
-> Ptr io_stream IP stream descriptor
-> unsigned long io_nclass Events not to notify on
ip_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 under
"IPJNOTIFICATION."
Errors returned are:
E_BADSTREAM
E_BADNOTIFICATION
ip_alloc (io_stream, io_buffer, io_buflen)
-> Ptr io_stream IP stream descriptor
<- Ptr *io_buffer Pointer to a datagram buffer
-> unsigned long io_buflen Requested buffer length
ip_alloc allocates an IP datagram buffer of length io_buflen.
Errors returned are:
E_BADSTREAM
E_NOMEM
ip_free (io_stream, io_buffer)
-> Ptr io_stream IP stream descriptor
-> Ptr io_buffer Pointer to a datagram buffer
ip_free releases an IP datagram buffer. io_buffer must point to a datagram buffer
allocated by ip_alloc or ip_get.
Errors returned are:
E_BADSTREAM
E_BADPTR
ip_put (io_stream, io_buffer, io_buflen, io_fhost, io_lhost, io_options,
io_optlen, io_flags)
-> Ptr io_stream IP stream descriptor
-> Ptr io_buffer Output buffer
-> unsigned long io_buflen Buffer length (bytes)
-> unsigned long io_fhost Destination host
-> unsigned long io_lhost Local host
-> Ptr io_options IP options
-> unsigned long io_optlen Length of options (bytes)
-> unsigned long io_flags Control flags
ip_put sends data to the address specified by io_fhost. io_buffer and io_buflen
specify the data to send. If the flag IP_FLAG_USEWDS is not set (see below), clients must
allocate io_buffer by calling ip_alloc and free them by calling ip_free.
If io_lhost is zero IP will route the packet and use the IP address of the selected interface
as the source address. If io_lhost is a valid IP address (one of the interfaces) IP will use
io_lhost as the source address for the packet. Routing will still be done as above.
io_options is a pointer to an array of ip_options, as specified in [RFCJ791].
io_optlen specifies the length of the options, in bytes (maximum 44). To specify no
options, pass io_options as NULL.
Special behavior can be specified with io_flags. The following flags are defined:
IP_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 "IPJDATAJSTRUCTURES."
Note that if IP_FLAG_USEWDS is set, datagram buffers need
not be allocated and freed with ip_alloc and ip_free.
Also, io_buflen is ignored.
Errors returned are:
E_BADSTREAM
E_BADWDS
E_BADFLAG
E_BADIPADDR
E_NOMEM
E_DTGTOOBIG
E_CANTRESOLVEADDR
E_HWWRITEERR
ip_get (io_stream, io_buffer, io_buflen, io_fhost, io_lhost, io_iph,
io_options, io_timeout, io_flags)
-> Ptr io_stream IP stream descriptor
<- Ptr *io_buffer Datagram from foreign host
<> unsigned long *io_buflen Length of datagram
<- unsigned long *io_fhost Foreign host
<- unsigned long *io_lhost Local host
<- ip_header_p *io_iph Pointer to raw IP header
<- Ptr io_options IP options
-> struct timeval *io_timeout Timeout value
<> unsigned long *io_flags Flags
ip_get requests a buffer from an IP stream. Note that io_buffer is allocated by the
driver, but should be freed by the client (see ip_free).
If io_timeout is NULL, ip_get blocks until a datagram arrives. If io_timeout is not
NULL and a datagram is not available within the timeout period, ip_get returns an error.
If io_iph is not NULL, a pointer is returned to the IP header for the datagram. However,
after io_buffer is deallocated (with ip_free), *io_iph is no longer guaranteed to be
valid. io_options must either be a NULL pointer or be preallocated by the client. If
NULL, no options are returned.
For the parameters io_fhost, io_lhost, 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
ip_control (io_stream, io_buffer, io_buflen,io_control)
-> Ptr io_stream IP 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
ip_control performs various operations for IP. 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 ip_control are:
E_BADSTREAM
E_BADCONTROL
Currently defined control operations are:
IP_CTL_VERSION
<> io_buffer Pointer to ip_version_t structure
-> io_control Control operation
Returns version information. Clients pass a pointer to a preallocated structure
of type ip_version_t, as defined in the section "IPJDATAJSTRUCTURES."
No specific errors are returned for this control.
IP_CTL_STATS
<> io_buffer Pointer to ip_stats_t structure
-> io_control Control operation
Returns statistics for IP. Clients pass a pointer to a preallocated structure of
type ip_stats_t, as defined in the section "IPJDATAJSTRUCTURES." This
is a preliminary version of the final structure, and is subject to change in the
near future.
No specific errors are returned for this control.
IP_CTL_GETADDR
<> io_buffer Pointer to array of ip_addr_t structures
-> *io_buflen Size of array (bytes)
-> io_control Control operation
Returns a zero-terminated list of local IP addresses (net numbers and net
masks). Clients pass a pointer to a preallocated array of elements of type
ip_addr_t, as defined in the section "IPJDATAJSTRUCTURES."
No specific errors are returned for this control.
IP_CTL_LHOST
<> io_buffer Points to IP address
-> io_control Control operation
Returns, through io_buffer, the local IP address that leads to the foreign IP
address specified at input.
Specific errors returned by this control are:
E_BADIPADDR
IP_CTL_MSS
<> io_buffer Pointer to ip_mss_t structure
-> io_control Control operation
Returns the maximum segment size for an IP address. Clients pass a pointer to
a preallocated structure of type ip_mss_t, as defined in the section
"IPJDATAJSTRUCTURES." Clients should specify an IP address in the
addr field of the ip_mss_t structure. If it is local, IP will return maximum
segment size information for the network interface on that local address. If it is
foreign, IP first determines the appropriate local IP address.
Specific errors returned by this control are:
E_BADIPADDR
ip_task ()
Clients should call ip_task periodically to allow IP time for asynchronous processing
(e.g., to process incoming datagrams).
Errors returned are:
E_CANTBLOCK
IP NOTIFICATION
---------------
Clients may request and cancel notification of asynchronous events by calling ip_request
and ip_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_lhost, io_prot,
io_nclass, io_ndata, io_userdata)
-> Ptr io_stream
-> Ptr io_buffer
-> unsigned long io_buflen
-> unsigned long io_fhost
-> unsigned long io_lhost
-> 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
ip_request by the client. io_ndata contains additional specification for the event.
The following describes the valid notification classes (io_nclass):
IP_NT_DATA: Data Arrival Notification
-> io_stream
-> io_fhost
-> io_lhost
-> io_nclass
-> io_userdata
Data arrival notification is delivered when a datagram arrives from io_fhost on
io_stream.
IP_NT_DELIVERY: Data Delivery Notification
-> io_stream
-> io_buffer
-> io_buflen
-> io_fhost
-> io_lhost
-> io_nclass
-> io_userdata
The client is notified of delivery of data from io_fhost on io_stream. io_buffer points
to a datagram of length io_buflen. This enables the client to immediately capture the data
without calling ip_get. The client is still responsible for calling ip_free when it no
longer requires the delivered datagram.
IP_NT_ERROR: Error Notification
-> io_stream
-> io_buffer
-> io_buflen
-> io_fhost
-> io_lhost
-> 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
IP ERROR CODES
--------------
Following is a description of all possible error codes returned by IP:
E_NOMEM
Not enough memory to perform operation.
E_PROTOINUSE
Protocol 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_BADIPADDR
Either destination IP address is invalid, or source IP address is not on one
of the interfaces.
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.