OS/2 RCB Device Driver Interface


                      Avnish Aggarwal






_1.  _I_n_t_r_o_d_u_c_t_i_o_n

     The OS/2 RCB driver supports the RCB  (Request  Control
Block)  abstraction  -  the  kernel  interface to the TCP/IP
transport.  A RCB driver installs as a standard OS/2  device
driver.  It  gets called by client drivers (such as a socket
driver, NFS Installable File System) via a direct  call,  as
opposed  to  going through the standard device driver inter-
face. More than one client may be using the  RCB  driver  at
one time.

     A client device driver performs a standard  DosDevIoctl
to  the RCB driver to get the far address of a "RCB Handler"
routine.  This routine is then passed RCBs for processing by
the  RCB  stack.   At  present,  the RCB handler can only be
called from protected mode.

_2.  _R_C_B _D_r_i_v_e_r _C_o_n_f_i_g_u_r_a_t_i_o_n

     The RCB  driver  gets  configuration  information  from
NET.CFG.  The only item of interest to client drivers should
be number of sockets supported. This is passed  back  during
initialization. No information is passed from client drivers
to the RCB driver.

_3.  _R_C_B _D_r_i_v_e_r _I_n_t_i_a_l_i_z_a_t_i_o_n

     The RCB driver will support a DosDevIoctl command  that
is issued from a client driver during system initialization.
The client does a DosOpen, DosDevIoctl(RcbLinkage), DosClose
to  get  the  RCB  Handler  address   back  from the the RCB
driver. (See below for details on RCBLinkage.)

_4.  _R_C_B _H_a_n_d_l_e_r _i_n_t_e_r_f_a_c_e

     The RCB handler is entered via a direct far  call.  The
calling conventions are as follows:







                        May 4, 1990





                           - 2 -



Entry
=====

ES:SI       Virtual address of RCB
DS          DS of RCB driver

Exit
====

AX:         immediate return code

            0   - ok
            1   - error



     The RCB driver will exit via a far return only when the
requested   operation has finished.  Depending on the opera-
tion, it may block for an indefinite time.  If the immediate
return code is not zero, an error is indicated.

     All addresses in the RCB must be virtual addresses that
are: a) locked down, and b) are GDT entries.  The RCB itself
must be a valid virtual address that has been locked down.

     The RCB driver does not distinguish   between  synchro-
nous  and  asynchronous calls - it is upto the client driver
to handle this feature.

_5.  _R_c_b_L_i_n_k_a_g_e


























                        May 4, 1990





                           - 3 -




Purpose:    Get RCB direct address
            Get config. info (# of sockets supported)
            Get DS (protect mode)

Return Codes:
            Standard codes returned by :

            DosOpen()
            DosDevIoctl()
            DosClose()


Request Packet:  (as sent by client driver)
            Request header
            Category (byte)         = 82h
            Code (byte)             = 70h
            Param Buffer Ptr (dword)= buffer must be 8 bytes long
            Data Buffer Ptr (dword) = NULL


Param Buffer : (as returned by the RCB driver)
            WORD    - # of sessions supported by RCB driver
            WORD    - RCB driver DS (protect mode)
            DWORD   - RCB Handler address  (ring 0 protect mode address)


_6.  _N_o_t_e_s

1    Name of RCB driver  - TCPIP.OS2

2    The client driver must be loaded after the RCB driver.
























                        May 4, 1990