wipllang - Description of the wipl programming language

This manual page describes the wipl programming language as implemented by the two programs wipld and wiplcExec. Look at the pages for these programs for examples of programs usable in practice.

The programs always have access to the shared memory area maintained by the wipld daemon and the purpose of the programs are to update and/or print information about the counters in this area. Only a single program at a time can access the shared memory area maintained by a wipld daemon, so a program can assume that the counters are not changed by others while it executes.

The following program will print the numbers from 1 to 10:

int a=1;
while(a<=10) {
  prints(a); print("\n");
  a=a+1;
}

When executed by wiplcExec they will be printed on stdout. When executed by wipld they will be written to the logfile. Note that the language does not have traditional lexical scoping. So the following program is not valid:

if(false) { 
  int a;
}
int a; // Error - variable a already declared

A variable of type int should be at least a 64 bit signed number and thus has more bits than the C type int has on most current platforms. An integer literal on more than 32 bits can be written in the form a:b. This is equivalent to (but more efficient to evaluate than) the expression: (a<<32)+b.

The language has a bool type which can be either true or false. You need an explicit cast to convert values between these two types. For example:

int a=42;
bool b=false;
b=bool(a); // Ok, b will now be true
a=int(b); // Ok, a will now be 1
b=a; // Error
a=b; // Error

Besides the types int and bool the language also has the types maca and ipa. A variable of type maca can contain a MAC address (like 11:22:33:44:55:66) and a variable of type ipa can contain an IP version 4 address (like 1.2.3.4).

With our new terminology we can say that wipld creates a shared memory area. This area contains an array. Depending on the addressing mode selected by wipld the array is indexed either by the maca or the ipa type. Each element in this array has a list of counters of type int.

If the daemon is in MAC addressing mode you can access counter 2 of the MAC address 11:22:33:44:55:66 by the expression 11:22:33:44:55:66[2]. To set the value of this counter to 10 use:

11:22:33:44:55:66[2]=10;

The following code will have the same effect:

maca a=11:22:33:44:55:66;
a[2]=10;

If the daemon is in IP addressing mode you should use IP instead of MAC addresses.

A rich set of operators on int arguments is available. For example one can use +, -, * and / for addition, subtraction, multiplication and division respectively. The operators << and >> can be used for bitwise left and right shifting.

Note that the / operator has a special meaning when used in the form ip/number: it gives the network part of the IP address, with the network mask given by the number. For example: 192.168.22.103/24 is the same as 192.168.22.0, and 192.168.22.103/16 is the same as 192.168.0.0

For a complete reference of the grammar of the language look in the module parseprg.y in the source code of wipl.

Several functions are available for the programs and these will will be described below.

print, prints These functions can be used to print variables or strings as the in the example above. print is defined for all build in types described above. It can also be used to print strings, like: print(" Hello World" ); The prints function is only defined for integer arguments. On most platforms it will print the 64 bit signed parameter as an unsigned 32 bit number.

TBLcardcnt The expression TBLcardcnt() evaluates to the number of entries (i.e. MAC/IP addresses) in the table in the shared memory area. These are numbered from 0.

TBLcntcnt The expression TBLcntcnt() evaluates to the number of counters defined for each entry in the table.

TBLgetidx The expression TBLidxget(a) will return the index the given address has in the table. If the daemon is in MAC addressing mode a must be a MAC address. If it is in IP addressing mode it must be an IP address. If no entry in the table exists for the given address an entry is created with all counters set to 0.

TBLgetmacaddr The expression MACgetmacaddr(i) will return the MAC address of the i'th entry in the table.

TBLgetipaddr The expression MACgetipaddr(i) will return the IP address of the i'th entry in the table.

TBLidxdel The expression TBLidxdel(i) will delete the i'th entry from the table.

All programs have access to the following predefined variables:

time This is the current time in number of seconds since 1. January 1970 GMT.

hour, min, wday, mday Evaluate to an integer representation of the hour, minute, weekday and day in month.

Besides these variables programs executed from wipld have access other variables reflecting the current packet being handled:

srcmac, srcip, srcport, dstmac, dstip, dstport The source and destination of the packet. srcport and dstport will evaluate to 0 if the packet is not a TCP or UDP packet.

size The size of the IP part of the packet

The error messages for wrong programs are not always very informative.

wipl(1), wiplc(1), wipld(8)