Revision 1.09 September-14-1989
Developed by: FTP Software, Inc. 26 Princess St. Wakefield, MA 01880-3004 (617) 246-0900Copyright (c) 1986, 1989 by FTP Software Inc. Permission is granted to reproduce and distribute this document without restriction or fee. This document may be re-formatted or translated, but the functional specification of the programming interface described herein may not be changed without FTP Software's permission. FTP Software's name and this notice must appear on any reproduction of this document. This specification was originally developed at FTP Software by John Romkey.
Support of a hardware interface, or mention of an interface manufacturer, by the Packet Driver specification does not necessarily indicate that the manufacturer endorses this specification.
The intent of this specification is to allow protocol stack implementations to be independent of the actual brand or model of the network interface in use on a particular machine. Different versions of various protocol stacks still must exist for different network media (Ethernet, 802.5 ring, serial lines), because of differences in protocol-to-physical address mapping, header formats, maximum transmission units (MTUs) and so forth.
The packet driver provides calls to initiate access to a specific packet type, to end access to it, to send a packet, to get statistics on the network interface and to get information about the interface.
Protocol implementations that use the packet driver can completely coexist on a PC and can make use of one another's services, whereas multiple applications which do not use the driver do not coexist on one machine properly. Through use of the packet driver, a user could run TCP/IP, XNS, and a proprietary protocol implementation such as DECnet, Banyan's, LifeNet's, Novell's or 3Com's without the difficulties associated with pre-empting the network interface.
Applications which use the packet driver can also run on new network hardware of the same class without being modified; only a new packet driver need be supplied.
Several levels of packet drivers are described in this specification. The first is the basic packet driver, which provides minimal functionality but should be simple to implement and which uses very few host resources. The basic driver provides operations to broadcast and receive packets. The second driver is the extended packet driver, which is a superset of the basic driver. The extended driver supports less commonly used functions of the network interface such as multicast, and also gathers statistics on use of the interface and makes these available to the application. The third level, the high-performance functions, support performance improvements and tuning.
Functions which are available in only the extended packet driver are noted as such in their descriptions. All basic packet driver functions are available in the extended driver. The high-performance functions may be available with either basic or extended drivers.
The second number is the type of interface: this specifies a particular instance of an interface supporting a class of network medium. Interface types for Ethernet might name these interfaces: 3Com 3C503 or 3C505, Interlan NI5210, Univation, BICC Data Networks ISOLAN, Ungermann-Bass NIC, etc. Interface types for IEEE 802.5 might name these interfaces: IBM Token Ring adapter, Proteon p1340, etc.
The last number is the interface number. If a machine is equipped with more than one interface of a class and type, the interfaces must be numbered to distinguish between them.
An appendix details constants for classes and types. The class of an interface is an 8-bit integer, and its type is a 16 bit integer. Class and type constants are managed by FTP Software. Contact FTP to register a new class or type number.
The type 0xFFFF is a wildcard type which matches any interface in the specified class. It is unnecessary to wildcard interface numbers, as 0 will always correspond to the first interface of the specified class and type.
This specification has no provision for the support of multiple network interfaces (with similar or different characteristics) via a single Packet Driver and associated interrupt. We feel that this issue is best addressed by loading several Packet Drivers, one per interface, with different interrupts (although all may be included in a single TSR software module). Applications software must check the class and type returned from a driver_info() call in any case, to make sure that the Packet Driver is for the correct media and packet format. This can easily be generalized by searching for another Packet Driver if the first is not of the right kind.
The handler for the interrupt is assumed to start with 3 bytes of executable code; this can either be a 3-byte jump instruction, or a 2-byte jump followed by a NOP (do not specify "jmp short" unless you also specify an explicit NOP). This must be followed by the null-terminated ASCII text string "PKT DRVR". To find the interrupt being used by the driver, an application should scan through the handlers for vectors 0x60 through 0x80 until it finds one with the text string "PKT DRVR" in the 12 bytes immediately following the entry point.
Our access_type() function provides access to this link-layer demultiplexing. Each call establishes a destination for a particular type of link-layer packet, which remains in effect until release_type() is called with the handle returned by that particular access_type(). The link-layer demultiplexing information is passed via the type and typelen fields, but values and interpretation depend on the class of packet driver (and thus on the media in use).
A class 1 driver (DIX Ethernet) should expect type to point at an "ethertype" value (in network byte order, and greater than 0x05EE), and might reasonably require typelen to equal 2. A class 2 driver could require 4 bytes. However, a class 3 (802.5) or 11 (Ethernet with 802.2 headers) driver should be prepared for typelen values between 2 (for the DSAP/SSAP fields only) and 8 (3 byte 802.2 header plus 3-byte Sub-Network Access Protocol extension header plus 2-byte "ethertype" as defined in RFC 1042).
The handle is an arbitrary integer value associated with each MAC-level demultiplexing type that has been established via the access_type call. Internally to the packet driver, it will probably be a pointer, or a table offset. The application calling the packet driver cannot depend on it assuming any particular range, or any other characteristics. In particular, if an application uses two or more packet drivers, handles returned by different drivers for the same or different types may have the same value.
Note that some of the functions defined below are labelled as extended driver functions and high-performance functions. Because these are not required for basic network operations, their implementation may be considered optional. Programs wishing to use these functions should use the driver_info() function to determine if they are available in a given packet driver.
Note that some older versions of PC/TCP may enable interrupts during the upcall, and leave them enabled on return to the Packet Driver.
When using a class 1 driver, PC/TCP will normally make 5 access_type() calls for IP, ARP and 3 kinds of Berkeley Trailer encapsulation packets. On other media, the number of handles we open will vary, but it is usually at least two (IP and ARP). Implementors should make their tables large enough to allow two protocol stacks to co-exist. We recommend support for at least 10 open handles simultaneously.
driver_info(handle) AH == 1, AL == 255 int handle; BX /* Optional */ error return: carry flag set error code DH possible errors: BAD_HANDLE /* older drivers only */ non-error return: carry flag clear version BX class CH type DX number CL name DS:SI functionality AL 1 == basic functions present. 2 == basic and extended present. 5 == basic and high-performance. 6 == basic, high-performance, extended. 255 == not installed.This function returns information about the interface. The version is assumed to be an internal hardware driver identifier. In earlier versions of this spec, the handle argument (which must have been obtained via access_type()) was required. It is now optional, but drivers developed according to versions of this spec previous to 1.07 may require it, so implementers should take care.
int access_type(if_class, if_type, if_number, type, typelen, receiver) AH == 2 int if_class; AL int if_type; BX int if_number; DL char far *type; DS:SI unsigned typelen; CX int (far *receiver)(); ES:DI error return: carry flag set error code DH possible errors: NO_CLASS NO_TYPE NO_NUMBER BAD_TYPE NO_SPACE TYPE_INUSE non-error return: carry flag clear handle AX receiver call: (*receiver)(handle, flag, len [, buffer]) int handle; BX int flag; AX unsigned len; CX if AX == 1, char far *buffer; DS:SIInitiates access to packets of the specified type. The argument type is a pointer to a packet type specification. The argument typelen is the length in bytes of the type field. The argument receiver is a pointer to a subroutine which is called when a packet is received. If the typelen argument is 0, this indicates that the caller wants to match all packets (match all requests may be refused by packet drivers developed to conform to versions of this spec previous to 1.07).
When a packet is received, receiver is called twice by the packet driver. The first time it is called to request a buffer from the application to copy the packet into. AX == 0 on this call. The application should return a pointer to the buffer in ES:DI. If the application has no buffers, it may return 0:0 in ES:DI, and the driver should throw away the packet and not perform the second call.
It is important that the packet length (CX) be valid on the AX == 0 call, so that the receiver can allocate a buffer of the proper size. This length (as well as the copy performed prior to the AX == 1 call) must include the MAC header and all received data, but not the trailing Frame Check Sequence (if any).
On the second call, AX == 1. This call indicates that the copy has been completed, and the application may do as it wishes with the buffer. The buffer that the packet was copied into is pointed to by DS:SI.
int release_type(handle) AH == 3 int handle; BX error return: carry flag set error code DH possible errors: BAD_HANDLE non-error return: carry flag clearThis function ends access to packets associated with a handle returned by access_type(). The handle is no longer valid.
int send_pkt(buffer, length) AH == 4 char far *buffer; DS:SI unsigned length; CX error return: carry flag set error code DH possible errors: CANT_SEND non-error return: carry flag clearTransmits length bytes of data, starting at buffer. The application must supply the entire packet, including local network headers. Any MAC or LLC information in use for packet demultiplexing (e.g. the DEC-Intel-Xerox Ethertype) must be filled in by the application as well. This cannot be performed by the driver, as no handle is specified in a call to the send_packet() function.
terminate(handle) AH == 5 int handle; BX error return: carry flag set error code DH possible errors: BAD_HANDLE CANT_TERMINATE non-error return: carry flag clearTerminates the driver associated with handle. If possible, the driver will exit and allow MS-DOS to reclaim the memory it was using.
get_address(handle, buf, len) AH == 6 int handle; BX char far *buf; ES:DI int len; CX error return: carry flag set error code DH possible errors: BAD_HANDLE NO_SPACE non-error return: carry flag clear length CXCopies the current local net address of the interface into buf. The buffer buf is len bytes long. The actual number of bytes copied is returned in CX. If the NO_SPACE error is returned, this indicates that len was insufficient to hold the local net address. If the address has been changed by set_address(), the new address should be returned.
reset_interface(handle) AH == 7 int handle; BX error return: carry flag set error code DH possible errors: BAD_HANDLE CANT_RESET non-error return: carry flag clearResets the interface associated with handle to a known state, aborting any transmits in process and reinitializing the receiver. The local net address is reset to the default (from ROM), the multicast list is cleared, and the receive mode is set to 3 (own address & broadcasts). If multiple handles are open, these actions might seriously disrupt other applications using the interface, so CANT_RESET should be returned.
high-performance driver function
get_parameters() AH = 10
error return:
carry flag set
error code DH
possible errors:
BAD_COMMAND /* No high-performance support */
non error return:
carry flag clear
struct param far *; ES:DI
struct param {
unsigned char major_rev; /* Revision of Packet Driver spec */
unsigned char minor_rev; /* this driver conforms to. */
unsigned char length; /* Length of structure in bytes */
unsigned char addr_len; /* Length of a MAC-layer address */
unsigned short mtu; /* MTU, including MAC headers */
unsigned short multicast_aval; /* Buffer size for multicast addr */
unsigned short rcv_bufs; /* (# of back-to-back MTU rcvs) - 1 */
unsigned short xmt_bufs; /* (# of successive xmits) - 1 */
unsigned short int_num; /* Interrupt # to hook for post-EOI
processing, 0 == none */
};
The performance of an application may benefit from using
get_parameters() to obtain a number of driver parameters. This
function was added to v1.09 of this specification, and may not be
implemented by all drivers (see driver_info()).
The major_rev and minor_rev fields are the major and minor revision numbers of the version of this specification the driver conforms to. For this document, major_rev is 1 and minor_rev is 9. The length field may be used to determine which values are valid, should a later revision of this specification add more values at the end of this structure. For this document, length is 14. The addr_len field is the length of a MAC address, in bytes. Note the param structure is assumed to be packed, such that these fields occupy four consecutive bytes of storage.
In the param structure, the mtu is the maximum MAC-level packet the driver can handle (on Ethernet this number is fixed, but it may vary on other media, e.g. 802.5 or FDDI). The multicast_aval field is the number of bytes required to store all the multicast addresses supported by any "perfect filter" mechanism in the hardware. Calling set_multicast_list() with its len argument equal to this value should not fail with a NO_SPACE error. A value of zero implies no multicast support.
The rcv_bufs and xmt_bufs indicate the number of back-to-back receives or transmits the card/driver combination can accomodate, minus 1. The application can use this information to adjust flow-control or transmit strategies. A single-buffered card (for example, an Interlan NI5010) would normally return 0 in both fields. A value of 0 in rcv_bufs could also be used by a driver author to indicate that the hardware has limitations which prevent it from receiving as fast as other systems can send, and to recommend that the upper-layer protocols invoke lock-step flow control to avoid packet loss.
The int_num field should be set to a hardware interrupt that the application can hook in order to perform interrupt-time protocol processing after the EOI has been sent to the 8259 interrupt controller and the card is ready for more interrupts. A value of zero indicates that there is no such interrupt. Any application hooking this interrupt and finding a non-zero value in the vector must pass the interrupt down the chain and wait for its predecessors to return before performing any processing or stack switches. Any driver which implements this function via a separate INT instruction and vector, instead of just using the hardware interrupt, must prevent any saved context from being overwritten by a later interrupt. In other words, if the driver switches to its own stack, it must allow re-entrancy.
high-performance driver function int as_send_pkt(buffer, length, upcall) AH == 11 char far *buffer; DS:SI unsigned length; CX int (far *upcall)(); ES:DI error return: carry flag set error code DH possible errors: CANT_SEND /* transmit error, re-entered, etc. */ BAD_COMMAND /* Level 0 or 1 driver */ non-error return: carry flag clear buffer available upcall: (*upcall)(buffer, result) int result; AX /* 0 for copy ok */ char far *buffer; ES:DI /* from as_send_pkt() call */as_send_pkt() differs from send_pkt() in that the upcall() routine is called when the application's data has been copied out of the buffer, and the application can safely modify or re-use the buffer. The driver may pass a non-zero error code to upcall() if the copy failed, or some other error was detected, otherwise it should indicate success, even if the packet hasn't actually been transmitted yet. Note that the buffer passed to send_pkt() is assumed to be modifiable when that call returns, whereas with as_send_pkt(), the buffer may be queued by the driver and dealt with later. If an error is returned on the initial call, the upcall will not be executed. This function was added in v1.09 of this specification, and may not be implemented by all drivers (see driver_info()).
extended driver function set_rcv_mode(handle, mode) AH == 20 int handle; BX int mode; CX error return: carry flag set error code DH possible errors: BAD_HANDLE BAD_MODE non-error return: carry flag clearSets the receive mode on the interface associated with handle. The following values are accepted for mode:
1 turn off receiver 2 receive only packets sent to this interface 3 mode 2 plus broadcast packets 4 mode 3 plus limited multicast packets 5 mode 3 plus all multicast packets 6 all packetsNote that not all interfaces support all modes. The receive mode affects all packets received by this interface, not just packets associated with the handle argument. See the extended driver functions get_multicast_list() and set_multicast_list() for programming "perfect filters" to receive specific multicast addresses.
Note that mode 3 is the default, and if the set_rcv_mode() function is not implemented, mode 3 is assumed to be in force as long as any handles are open (from the first access_type() to the last release_type()).
extended driver function get_rcv_mode(handle, mode) AH == 21 int handle; BX error return: carry flag set error code DH possible errors: BAD_HANDLE non-error return: carry flag clear mode AXReturns the current receive mode of the interface associated with handle.
extended driver function set_multicast_list(addrlst, len) AH == 22 char far *addrlst; ES:DI int len; CX error return: carry flag set error code DH possible errors: NO_MULTICAST NO_SPACE BAD_ADDRESS non-error return: carry flag clearThe addrlst argument is assumed to point to an len-byte buffer containing a number of multicast addresses. BAD_ADDRESS is returned if len modulo the size of an address is not equal to 0, or the data is unacceptable for some reason. NO_SPACE is returned (and no addresses are set) if there are more addresses than the hardware supports directly.
The recommended procedure for setting multicast addresses is to issue a get_multicast_list(), copy the information to a local buffer, add any addresses desired, and issue a set_multicast_list(). This should be reversed when the application exits. If the set_multicast_list() fails due to NO_SPACE, use set_rcv_mode() to set mode 5 instead.
extended driver function get_multicast_list() AH == 23 error return: carry flag set error code DH possible errors: NO_MULTICAST NO_SPACE non-error return: carry flag clear char far *addrlst; ES:DI int len; CXOn a successful return, addrlst points to len bytes of multicast addresses currently in use. The application program must not modify this information in-place. A NO_SPACE error indicates that there wasn't enough room for all active multicast addresses.
extended driver function
get_statistics(handle) AH == 24
int handle; BX
error return:
carry flag set
error code DH
possible errors:
BAD_HANDLE
non-error return:
carry flag clear
char far *stats; DS:SI
struct statistics {
unsigned long packets_in; /* Totals across all handles */
unsigned long packets_out;
unsigned long bytes_in; /* Including MAC headers */
unsigned long bytes_out;
unsigned long errors_in; /* Totals across all error types */
unsigned long errors_out;
unsigned long packets_lost; /* No buffer from receiver(), card */
/* out of resources, etc. */
};
Returns a pointer to a statistics structure for the interface. The values are
stored as to be normal 80xx 32-bit integers.
extended driver function set_address(addr, len) AH == 25 char far *addr; ES:DI int len; CX error return: carry flag set error code DH possible errors: CANT_SET BAD_ADDRESS non-error return: carry flag clear length CXThis call is used when the application or protocol stack needs to use a specific LAN address. For instance, DECnet protocols on Ethernet encode the protocol address in the Ethernet address, requiring that it be set when the protocol stack is loaded. A BAD_ADDRESS error indicates that the Packet Driver doesn't like the len (too short or too long), or the data itself. Note that packet drivers should refuse to change the address (with a CANT_SET error) if more than one handle is open (lest it be changed out from under another protocol stack).
3COM 3C500/3C501 1 3COM 3C505 2 Interlan Ni5010 3 BICC Data Networks 4110 4 BICC Data Networks 4117 5 MICOM-Interlan NP600 6 Ungermann-Bass PC-NIC 8 Univation NC-516 9 TRW PC-2000 10 Interlan Ni5210 11 3COM 3C503 12 3COM 3C523 13 Western Digital WD8003 14 Spider Systems S4 15 Torus Frame Level 16 10NET Communications 17 Gateway PC-bus 18 Gateway AT-bus 19 Gateway MCA-bus 20 IMC PCnic 21 IMC PCnic II 22 IMC PCnic 8bit 23 Tigan Communications 24 Micromatic Research 25 Clarkson "Multiplexor" 26 D-Link 8-bit 27 D-Link 16-bit 28 D-Link PS/2 29 Research Machines 8 30 Research Machines 16 31 Research Machines MCA 32 Radix Microsys. EXM1 16-bit 33 Interlan Ni9210 34 Interlan Ni6510 35 Vestra LANMASTER 16-bit 36 Vestra LANMASTER 8-bit 37 Allied Telesis PC/XT/AT 38 Allied Telesis NEC PC-98 39 Allied Telesis Fujitsu FMR 40 Ungermann-Bass NIC/PS2 41 Tiara LANCard/E AT 42 Tiara LANCard/E MC 43 Tiara LANCard/E TP 44 Spider Comm. SpiderComm 8 45 Spider Comm. SpiderComm 16 46 AT&T Starlan NAU 47 AT&T Starlan-10 NAU 48 AT&T Ethernet NAU 49 Intel smart card 50
Proteon p1300 1 Proteon p1800 2
IBM Token ring adapter 1 Proteon p1340 2 Proteon p1344 3 Gateway PC-bus 4 Gateway AT-bus 5 Gateway MCA-bus 6
Clarkson 8250-SLIP 1 Clarkson "Multiplexor" 2
(NOTE: Class has been subsumed by Ethernet)
Datapoint RIM 1
Types as given under DIX Ethernet See Appendix D.
Western Digital 1 Frontier Technology 2
NT LANSTAR/8 1 NT LANSTAR/MC 2
driver_info 1 access_type 2 release_type 3 send_pkt 4 terminate 5 get_address 6 reset_interface 7 +get_parameters 10 +as_send_pkt 11 *set_rcv_mode 20 *get_rcv_mode 21 *set_multicast_list 22 *get_multicast_list 23 *get_statistics 24 *set_address 25 + indicates a high-performance packet driver function * indicates an extended packet driver function
AH values from 128 through 255 (0x80 through 0xFF) are reserved for user-developed extensions to this specification. While FTP Software cannot support user extensions, we are willing to act as a clearing house for information about them. For more information, contact us.
1 BAD_HANDLE Invalid handle number, 2 NO_CLASS No interfaces of specified class found, 3 NO_TYPE No interfaces of specified type found, 4 NO_NUMBER No interfaces of specified number found, 5 BAD_TYPE Bad packet type specified, 6 NO_MULTICAST This interface does not support multicast, 7 CANT_TERMINATE This packet driver cannot terminate, 8 BAD_MODE An invalid receiver mode was specified, 9 NO_SPACE Operation failed because of insufficient space, 10 TYPE_INUSE The type had previously been accessed, and not released, 11 BAD_COMMAND The command was out of range, or not implemented, 12 CANT_SEND The packet couldn't be sent (usually hardware error), 13 CANT_SET Hardware address couldn't be changed (more than 1 handle open), 14 BAD_ADDRESS Hardware address has bad length or format, 15 CANT_RESET Couldn't reset interface (more than 1 handle open).
One solution is to redefine class 1 as Blue Book Ethernet, and define a parallel class for 802.3 with 802.2 packet headers. This requires that a 2nd Packet Driver (as defined by its interrupt) be implemented where it is necessary to handle both kinds of packets, although they could both be part of the same TSR module.
As of v1.07 of this specification, class 11 was assigned to 802.3 using 802.2 headers, to implement the above.
Note: According to this scheme, an application wishing to receive IP encapsulated with an 802.2 SNAP header and "ethertype" of 0x800, per RFC 1042, would specify an typelen argument of 8, and type would point to:
char iee_ip[] = {0xAA, 0xAA, 3, 0, 0, 0, 0x00, 0x08};
James B. VanBokkelen jbvb@@ftp.com ...!ftp!jbvb