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cnet's datatypes, event types, and error types
cnet's provides a number of datatypes,
necessary to identify node types, link types, events, and errors.
Each datatype is defined in the <cnet.h> header file.
The datatypes are:
- The CnetNodeType enumerated type
-
Each node is either a host (such as a workstation),
a router,
a mobile node (such as a mobile phone), or
a wireless accesspoint.
The type of a node may be determined by examining its value of
OS->nodetype.
For example:
if(OS->nodetype == NT_HOST) {
CNET_set_handler(EV_APPLICATIONREADY, appl_ready, 0);
}
| CnetNodeType |
meaning |
| NT_HOST |
this node is a host with an Application Layer and keyboard |
| NT_ROUTER |
this node is a router without an Application Layer or keyboard |
| NT_MOBILE |
this node may move, may only have WLAN links,
maintains a record of its battery level,
and has an Application Layer and keyboard |
| NT_ACCESSPOINT |
this node is a wireless accesspoint, must have at least one
WLAN link,
and has no Application Layer or keyboard |
Note that calls to the functions
CNET_write_application,
CNET_read_application,
CNET_enable_application,
CNET_disable_application,
CNET_set_handler(EV_APPLICATIONLAYER,...), and
CNET_set_handler(EV_KEYBOARDREADY,...)
are only valid if called from a node of
type NT_HOST or NT_MOBILE.
Calls to the functions
CNET_set_position, and
CNET_set_battery
are only valid if called from a node of type NT_MOBILE.
- The CnetLinkType enumerated type
-
Each node's links provide either a loopback service,
wide-area-networking,
local-area-networking, or
wireless-local-area-networking.
The type of a link may be determined by examining the value of
OS->links[link].linktype.
For example:
if(OS->links[link].linktype == LT_LAN) {
if(CNET_lan_busy(link)) {
..........
}
}
| CnetLinkType |
meaning |
| LT_LOOPBACK |
this link (which will always be link 0) is used to quickly
transmit data from a node to itself |
| LT_WAN |
this link connects this node to one other node via a dedicated,
point-to-point wide-area network link |
| LT_LAN |
this link connects this node to other nodes via a simulation of
an IEEE-802.3 shared segment |
| LT_WLAN |
this link provides a wireless "connection"
to all other WLAN links that can receive its transmission |
Calls to the function
CNET_set_nicaddr
may only be made for links of type LT_LAN or LT_WLAN.
- The CnetError enumerated type
-
Most cnet API functions return the integer 0 on success
and the integer -1 on failure.
The most recent error status is stored in
the global variable cnet_errno.
All values of cnet_errno will be instances of the
enumerated type CnetError.
Functions do not set the value of cnet_errno to
ER_OK if their execution was successful.
Errors may be reported to stderr with
CNET_perror() and their error message string accessed from
cnet_errstr[(int)cnet_errno].
For example:
if(CNET_write_application(msgbuffer, &msglength) != 0) {
// an error has occured
if(cnet_errno == ER_BADSESSION) {
// handle this special case
....
}
else {
CNET_perror("writing to application");
}
}
| CnetError |
meaning |
| ER_OK |
No error |
| ER_BADALLOC |
Allocation of dynamic memory failed |
| ER_BADARG |
Invalid argument passed to a function |
| ER_BADEVENT |
Invalid event passed to a function |
| ER_BADLINK |
Invalid link number passed to a function |
| ER_BADNODE |
Invalid node passed to a function |
| ER_BADPOSITION |
Attempt to move mobile node off the map |
| ER_BADSENDER |
Application Layer given message from an unknown node |
| ER_BADSESSION |
Application Layer given message from incorrect session |
| ER_BADSIZE |
Indicated length is of incorrect size |
| ER_BADTIMER |
Invalid CnetTimerID passed to a function |
| ER_CORRUPTFRAME |
Attempt to transfer corrupt data
(only seen if -e provided) |
| ER_DUPLICATEMSG |
Application Layer given a duplicate message |
| ER_LINKDOWN |
Attempt to transmit on a link which is down |
| ER_MISSINGMSG |
Application Layer given a message before all previous ones |
| ER_NOBATTERY |
Battery exhaused on a mobile node |
| ER_NOTFORME |
Application Layer given a message for another node |
| ER_NOTREADY |
Function called when service not available |
| ER_NOTSUPPORTED |
Invalid operation for this node or link type |
| ER_TOOBUSY |
Link is too busy/congested to handle request |
- The CnetEvent enumerated type
-
All events in cnet are of type CnetEvent.
Events are raised when a number of important things occur
that (possibly) require action from your protocols.
Interest may be registered in each event by calling the function
CNET_set_handler
and passing to it a function, an event handler,
to be called when the event is raised.
By default, no events are of interest (all are ignored).
When an event of interest is raised, its event handler is called,
with the event (an instance of CnetEvent)
passed as the first parameter.
| CnetEvent |
meaning |
| EV_NULL |
this event is used internally and is never seen by your protocols |
| EV_REBOOT |
raised as reboot_node(EV_REBOOT, ... , ...) |
| EV_SHUTDOWN |
raised before cnet is (cleanly) terminated |
| EV_APPLICATIONREADY |
raised when there is a message ready for delivery |
| EV_PHYSICALREADY |
raised when a frame arrives at one of the links |
| EV_FRAMECOLLISION |
raised when a frame collides on LT_LAN or LT_WLAN |
| EV_KEYBOARDREADY |
raised when an input line is entered from the keyboard |
| EV_LINKSTATE |
raised when a link changes state (either up or down) |
| EV_DRAWFRAME |
raised when a frame is to be drawn in 2-node world |
| EV_PERIODIC |
raised periodically if the
-f option provided |
| EV_DEBUG0..EV_DEBUG4 |
raised when one of the debug buttons is pressed |
| EV_TIMER0..EV_TIMER9 |
raised when a timer on any of the 10 timer queues expires |
- The CnetNICaddr datatype
-
Each Physical Layer link of type LT_WAN,
LT_LAN, or
LT_WLAN
has a specific Network Interface Card (NIC) address.
cnet provides the CnetNICaddr datatype to represent the
addresses of its NICs,
as an array of LEN_NICADDR (=6) unsigned characters.
Although cnet does not require it,
it is anticipated that frames will carry the address of their source and
destination Network Interface Cards (NIC) near the beginning of the frame.
cnet provides the functions
CNET_parse_nicaddr and
CNET_format_nicaddr
to convert between character strings and the CnetNICaddr datatype.
- The CnetTime datatype
-
All times and periods in cnet are stored as an integral number
of microsconds.
This requires a sufficiently long integer representation to
avoid values "wrapping around" in most simulations.
cnet employs ISO-C99's standard int64_t datatype
to represent time:
typedef int64_t CnetTime;
and all function arguments and structure fields
requiring a number of microseconds,
employ the CnetTime type.
Standard integer arithmetic, such as addition and subtraction,
and comparisons may be performed on CnetTime values,
and they may be formatted with
printf("time taken %" PRIi64 "usecs\n", taken);
- The WLANRESULT enumerated type
-
A simulation needing to define its own WLAN signal propagation model,
will call
CNET_set_wlan_model
to register a function that determines the
extent and success of wireless signal propagation.
This function must return one of the values of WLANRESULT:
| WLANRESULT |
meaning |
| WLAN_TOOWEAK |
the receiver cannot hear the WLAN signal at all |
| WLAN_TOONOISY |
the receiver can hear the WLAN signal, but cannot discern its
contents from the background noise |
| WLAN_RECEIVED |
the WLAN signal is both heard and decodable |
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