NAME

internet − IP-level Internet interface pseudo-device driver (types dgm, dg)

SYNOPSIS

#include <network.h>
read(device buffer, length)
write(device, buffer, length)
open(device, name)
close(device)
control(device, function, arg1)
init(device)

DESCRIPTION

The dgm and dg device drivers, which operate as a related pair, provide a network interface at the IP datagram level.  They accept datagrams from user processes and send them out on the DARPA Internet, or receive datagrams from the Internet and deliver them to user processes.  The standard Xinu device name for the datagram master pseudo-device is INTERNET, and the standard name for individual connection pseudo-devices is DGRAM. 

The drivers cooperate so that users can initiate connection by calling OPEN(2) on the datagram master device.  If successful, the call to OPEN(2) returns the device descriptor of a dg pseudo-device that can be used with READ(2) or WRITE(2) to transfer data.  Finally, when finished with the connection, the user process calls CLOSE(2) on the dg device. 

The dgm driver consists of routines that implement OPEN(2) and CONTROL(2), while the dg driver consists of routines for READ(2), WRITE(2), CLOSE(2), and CONTROL(2).  Primitives READ(2) and WRITE(2) operate in one of two basic modes.  Either they transfer data in Xinugram format complete with an address header, or they transfer just the data portion of the datagram. 

open(device,name,mode)
Used with the master device to open a datagram pseudo-device. Name is a string that gives an IP address and UDP port number in the form i1.i2.i3.i4:u. 

control(device,function,arg1)
Used with master device to set the default gateway for nonlocal IP datagram traffic.  The only function supported is DGM_GATE which takes an IP address as an argument and sets the default gateway to that address. 

Used with a dg pseudo-device to set the transfer mode.  The valid operations include DG_CLEAR, which clears any UDP datagrams that happen to be in the receive queue, and DG_SETMODE, which sets the pseudo-device mode.  The mode argument composed of a word in which the first two bits control the transfer mode and sixth bit controls timeout.  The symbolic constants for these bits are:

DG_NMODE (001) − Normal mode
DG_DMODE (002) − Data-only mode
DG_TMODE (040) − Timeout all reads

Note that timeout can be applied to either transfer mode.

read(device buffer, length)
Used with a dg pseudo-device to await the arrival of a UDP datagram and transfer it to the user in the form of a Xinugram. 

write(device, buffer, length)
Used with a dg pseudo-device to transfer a xinugram into a UDP datagram and send it on the Internet. 

close(device)
Closes a dg pseudo-device. 

init(device)
When applied to dg pseudo-devices initializes each to mark it not in use. 

December 01, 1986  —  Xinu Programmer’s Manual