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PC/TCP Version 1.08 Packet Driver Specification 1 FTP Software, Inc. PC/TCP Packet Driver Specification Revision 1.08 December-12-1988 Developed by: FTP Software, Inc. P.O. Box 150 Kendall Sq. Branch Boston, MA 02142 (617) 868-4878 Note: this document is public domain and may be distributed freely and without fee or permission. FTP Software's name and this notice must appear on any reproduction of this document. 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. 1 Introduction and Motivation This document describes the programming interface to PC/TCP packet drivers. Packet drivers provide a simple, common programming interface that allows multiple applications to share a network interface at the data link level. The packet drivers demultiplex incoming packets amongst the applications by using the network media type field. Different versions of PC/TCP exist for different network media (Ethernet, 802.5 ring, serial lines), but through the use of the packet driver, the actual brand or model of the network interface can be hidden from the application. 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 2 PC/TCP Version 1.08 Packet Driver Specification FTP Software, Inc. of the packet driver, a user could run TCP/IP, DECnet, and a proprietary protocol implementation such as Banyan's, LifeNet's, Novell's or 3COM's without the difficulties associated with preempting 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. Two 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. 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. 2 Identifying network interfaces Network interfaces are named by a triplet of integers, <class, type, number>. The first is the class of interface. The class tells what kind of media the interface is for: DEC/Intel/Xerox/Ethernet, IEEE 802.3 Ethernet, IEEE 802.5/Token Ring, ProNET-10, Broadband Ethernet, Appletalk, serial line, etc. The second number is the type of interface: this specifies a particular instance of an interface supporting a class of medium. Interface types for Ethernet might name these interfaces: 3COM 3C501 or 3C505, Interlan NI5010, 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. PC/TCP Version 1.08 Packet Driver Specification 3 FTP Software, Inc. 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 already, 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. 3 Initiating driver operations The packet driver is invoked via a software interrupt in the range 0x60 through 0x80. This document does not specify a particular interrupt, but describes a mechanism for locating which interrupt the driver uses. The interrupt must be configurable to avoid conflicts with other pieces of software that also use software interrupts. The program which installs the packet driver should provide some mechanism for the user to specify the interrupt. The handler for the interrupt is assumed to start with 3 bytes of exectuable 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 it. 4 Programming interface All functions are accessed via the software interrupt determined to be the driver's via the mechanism described earlier. On entry, register AH contains the code of the function desired. 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, 4 PC/TCP Version 1.08 Packet Driver Specification FTP Software, Inc. 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. Note that some of the functions defined below are labelled as extended driver 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. 4.1 Entry conditions FTP Software applications which call the packet driver are coded in Microsoft C and assembly language. All necessary registers are saved by FTP's routines before the INT instruction to call the packet driver is executed. Our current receiver() functions behave as follows: DS and the flags are saved and restored. All other registers may be modified, and should be saved by the packet driver, if necessary. Processor interrupts may be enabled while in the upcall, but the upcall doesn't assume interrupts are disabled on entry. On entry, receiver() switches to a local stack. Current FTP Software receiver() routines may modify all registers except DS, so the caller must save and restore any that must be preserved across the call. Note that some older versions of PC/TCP may enable interrupts during the upcall, and leave them enabled on return to the Packet Driver. 4.2 Byte ordering Developers should note that, on many networks and protocol families, the byte-ordering of 16-bit quantities on the network is opposite to the native byte-order of the PC. (802.5 Token Ring is an exception). This means that DEC- Intel-Xerox ethertype values passed to access_type() must be swapped (passed in network order). The IEE 802.3 length field needs similar handling, and care should be taken with packets passed to send_pkt(), so they are in the proper order. 4.3 driver_info() driver_info(handle) AH == 1 AL == FF int handle; BX /* Optional */ error return: PC/TCP Version 1.08 Packet Driver Specification 5 FTP Software, Inc. 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 basic/extended AL 1 == basic, 2 == extended, FF == 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. 4.4 access_type() 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: 6 PC/TCP Version 1.08 Packet Driver Specification FTP Software, Inc. (*receiver)(handle, flag, len [, buffer]) int handle; BX int flag; AX unsigned len; CX if AX == 1, char far *buffer; DS:SI Initiates 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 is 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 Ethernet header and all received data, but not the trailing checksum. 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. 4.5 release_type() 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 clear PC/TCP Version 1.08 Packet Driver Specification 7 FTP Software, Inc. This function ends access to packets associated with a handle returned by access_type(). The handle is no longer valid. 4.6 send_pkt() 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 clear Transmits 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. 4.7 terminate() 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 clear Terminates the driver associated with handle. If possible, the driver will exit and allow MS-DOS to reclaim the memory it was using. 4.8 get_address() get_address(handle, buf, len) AH == 6 int handle; BX 8 PC/TCP Version 1.08 Packet Driver Specification FTP Software, Inc. 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 CX Copies the local net address associated with handle 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. 4.9 reset_interface() reset_interface(handle) AH == 7 int handle; BX error return: carry flag set error code DH possible errors: BAD_HANDLE non-error return: carry flag clear Resets the interface associated with handle to a known state, aborting any transmits in process and reinitializing the receiver. This call has been included primarily for circumstances where a high-level protocol has detected what it thinks may be an interface failure or hang. If the packet driver implementer has a high level of confidence in the hardware, or the action would seriously disrupt other users of the interface, this can be treated as a no-op. 4.10 set_rcv_mode() extended driver function set_rcv_mode(handle, mode) AH == 20 int handle; BX int mode; CX PC/TCP Version 1.08 Packet Driver Specification 9 FTP Software, Inc. error return: carry flag set error code DH possible errors: BAD_HANDLE BAD_MODE non-error return: carry flag clear Sets the receive mode on the interface associated with handle. The following values are accepted for mode: mode meaning 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 packets Note 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()). 4.11 get_rcv_mode() 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 AX 10 PC/TCP Version 1.08 Packet Driver Specification FTP Software, Inc. Returns the current receive mode of the interface associated with handle. 4.12 set_multicast_list() 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 clear The 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. 4.13 get_multicast_list() extended driver function get_multicast_list() AH == 23 error return: carry flag set error code DH possible errors: NO_MULTICAST non-error return: carry flag clear char far *addrlst; ES:DI int len; CX PC/TCP Version 1.08 Packet Driver Specification 11 FTP Software, Inc. On a successful return, addrlst points to len bytes of multicast addresses currently in use. The application program must not modify this information in-place. 4.14 get_statistics() 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 statistics structure: field byte length packets in 4 packets out 4 bytes in 4 bytes out 4 errors in 4 errors out 4 packets dropped 4 Returns a pointer to a statistics structure for this handle. 4.15 set_address() 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 CX PC/TCP Version 1.08 Packet Driver Specification 1 FTP Software, Inc. This 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). PC/TCP Version 1.08 Packet Driver Specification A.1 FTP Software, Inc. Appendix A Interface classes and types The following are defined as network interface classes, with their individual types listed immediately following the class. DEC/Intel/Xerox "Bluebook" Ethernet 1 3COM 3C500/3C501 1 3COM 3C505 2 MICOM-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 MICOM-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 ProNET-10 2 Proteon p1300 1 IEEE 802.5/ProNET-4 3 IBM Token ring adapter 1 Proteon p1340 2 Proteon p1344 3 Gateway PC-bus 4 Gateway AT-bus 5 Gateway MCA-bus 6 Omninet 4 A.2 PC/TCP Version 1.08 Packet Driver Specification FTP Software, Inc. Appletalk 5 Serial line 6 Starlan 7 (NOTE: This has been subsumed by Ethernet) ArcNet 8 Datapoint RIM 1 AX.25 9 KISS 10 IEE 802.3 w/802.2 hdrs 11 Types as given under DIX Ethernet See Appendix D. PC/TCP Version 1.08 Packet Driver Specification B.1 FTP Software, Inc. Appendix B Function call numbers The following numbers are used to specify which operation the packet driver should perform. The number is stored in register AH on call to the packet driver. driver_info 1 access_type 2 release_type 3 send_pkt 4 terminate 5 get_address 6 reset_interface 7 *set_rcv_mode 20 *get_rcv_mode 21 *set_multicast_list 22 *get_multicast_list 23 *get_statistics 24 *set_address 25 * indicates an extended packet driver function PC/TCP Version 1.08 Packet Driver Specification C.1 FTP Software, Inc. Appendix C Error codes Packet driver calls indicate error by setting the carry flag on return. The error code is returned in register DH (a register not used to pass values to functions must be used to return the error code). The following error codes are defined: 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 PC/TCP Version 1.08 Packet Driver Specification D.1 FTP Software, Inc. Appendix D 802.3 vs. Blue Book Ethernet One weakness of the present specification is that there is no provision for simultaneous support of 802.3 and Blue Book (the old DEC-Intel-Xerox standard) Ethernet headers via a single Packet Driver (as defined by its interrupt). The problem is that the Ethertype of Blue Book packets is in bytes 12 and 13 of the header, and in 802.3 the corresponding bytes are interpreted as a length. In 802.3, the field which would appear to be most useful to begin the type check in is the 802.2 header, starting at byte 14. This is only a problem on Ethernet and variants (e.g. Starlan), where 802.3 headers and Blue Book headers are likely to need co-exist for many years to come. 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 this draft, class 11 has been assigned to 802.3 using 802.2 headers, to implement the above. Note: According to this scheme, an application wishing to receive IP encapsulated per RFC 1042 would specify an typelen argument of 8, and type would point to: char iee_ip[] = {0xAA, 0xAA, 3, 0, 0, 0, 0x08, 0x00}; James B. VanBokkelen jbvb@ftp.com ...!ftp!jbvb Table of Contents 1 Introduction and Motivation . . . . . . . 1 2 Identifying network interfaces . . . . . 2 3 Initiating driver operations . . . . . . 3 4 Programming interface . . . . . . . . . . 3 4.1 Entry conditions . . . . . . . . . . 4 4.2 Byte ordering . . . . . . . . . . . 4 4.3 driver_info() . . . . . . . . . . . 4 4.4 access_type() . . . . . . . . . . . 5 4.5 release_type() . . . . . . . . . . . 6 4.6 send_pkt() . . . . . . . . . . . . . 7 4.7 terminate() . . . . . . . . . . . . 7 4.8 get_address() . . . . . . . . . . . 7 4.9 reset_interface() . . . . . . . . . 8 4.10 set_rcv_mode() . . . . . . . . . . 8 4.11 get_rcv_mode() . . . . . . . . . . 9 4.12 set_multicast_list() . . . . . . . 10 4.13 get_multicast_list() . . . . . . . 10 4.14 get_statistics() . . . . . . . . . 11 4.15 set_address() . . . . . . . . . . . 11 Appendix A Interface classes and types A-1 Appendix B Function call numbers B-1 Appendix C Error codes C-1 Appendix D 802.3 vs. Blue Book Ethernet D-1 i