Enumerating IP valid addresses

[Michael Burns]

I posted a variant of this question on a thread earlier today, but it got lost in the shuffle and so far the messages posted after mine were orthogonal to my question.

I realize everyone knows this, but I'll go through it to set up the problem.

In a "HOST ADDR TO Temp" statement, you get the primary IP address of the machine placed in Temp. If you have more than one IP address assigned to the machine, you'll only get the first one with that version of the HOST ADDR statement. OK, fine. We all know that if you have two ethernet cards, or say one and have an active modem, there will be two IP addresses, and you can get them by doing:

HOST ADDR 1 TO Temp1
HOST ADDR 2 TO Temp2

The "1" and "2" are the index. The index is the key.

Here is my question: How do you enumerate the valid range of the index if you need to know ALL of the IP addresses for the machine, but your application will not have a clue ahead of time how many the machine it is running on might have?

I did a simple experiment hoping I could simply advance the index until a trappable error occurred. No such luck.. If you exceed the index's valid range, you get a bunch of nonvalid IP addresses (as far as I can tell), and then a General Protection Fault.

For example, in my machine right now I have two ethernet cards and a (inactive) modem.

If I run this code (suitably inserted in the correct PB trappings):

FOR Index& = 1 TO 10
HOST ADDR (Index&) TO Temp
IF ERR THEN GOTO Outloop
#DEBUG PRINT IpToString(Temp)
NEXT Index&
Outloop:


I trigger a General Protection Fault when Index&=6.

The DEBUG window displays

24.13.211.16
192.168.0.1
107.98.46.110
101.46.109.101
100.105.97.111

The first two IP addressess (24.13.211.16, 192.168.0.1) are correct. That last 3 are junk as far as I can tell.

So does anyone know how if I have no prior knowledge of how many IP addresses the machine my application will be running in should have, but I need to know ALL of them, how can I ascertain the valid range for Index& ?

(As an aside, I do know how to enumerate & list all the valid MAC addresses in a machine, but aside from doing all that work to just to get an index range for enumerating all the IP addresses, the number of valid MAC addresses won't always match the number of valid IP addresses.)


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[Florent Heyworth]

hi michael

you'll find what you're looking for at: http://www.powerbasic.com/support/pb...ead.php?t=3747

cheers

florent

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[Lance Edmonds]

I trigger a General Protection Fault when Index&=6.

That is an unfortunate bug in HOST ADDR which will be corrected in the next update to the compiler.

Note that when HOST ADDR(Index&) returns zero, there are no further IP addresses to enumerate. I'm not sure if the addresses you receive are vaklid or not, but on my DEV PC I can locate only 2 IP addresses with HOST ADDR. (disclaimer, I wrote the last part of this based on my recollection of my tests, so I'll recheck that result when I get back to my DEV PC).



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Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>

[Scott Turchin]

If you want to index you COULD try this, it's cheap but it may work:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Class\NetTrans\0001

Start with 0001, go through to about 12, the key you are looking for first is:

DriverDesc

If it says TCP/IP Then call the same key for:

IPAddress


My code would loop through that in about half a second or better...

Again it's cheap, the other method appears to work better and be the RIGHT way to do it....


Scott

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Scott
mailto:[email protected][email protected]</A>

[Michael Burns]

Thanks Florent. Your code snippet works just fine.


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[Michael Burns]

Woops! Here's a puzzler. When I tested that code in the following
manner, it worked just fine.

#COMPILE EXE
#DIM ALL
#INCLUDE "WIN32API.INC"
#INCLUDE "WSOCK32.INC"

FUNCTION EnumerateIPs () AS STRING
DIM wd AS WSAData
DIM ret AS LONG
DIM hostname AS ASCIIZ * 256
DIM hent AS hostentStru PTR
DIM i AS LONG
DIM ptrIP AS ASCIIZ PTR
DIM temp AS STRING
ret = WSAStartup(&H101, wd)
IF ret <> 0 THEN
EnumerateIPs=""
EXIT FUNCTION
END IF
' Set hostname to your machine name...
HOST NAME TO hostname
hent = gethostbyname(hostname)
IF hent = 0 THEN
EnumerateIPs=""
WSACleanup
EXIT FUNCTION
END IF
temp = "All IP addresses found assigned to this machine:" +CHR$(13) +CHR$(10)
DO
INCR i
ptrIP = inet_ntoa(@[email protected]@h_list)
temp = temp + @ptrIP +CHR$(13) +CHR$(10)
@hent.h_list = @hent.h_list + @hent.h_len
IF @[email protected]_list = 0 THEN EXIT DO
LOOP
WSACleanup
EnumerateIPs=temp
END FUNCTION

FUNCTION PBMAIN()

MSGBOX EnumerateIPs

END FUNCTION


However when I cut & pasted the subroutine "EnumerateIPs" into the
program I want to use it in (which has the same compiler
switches,
#COMPILE EXE
#DIM ALL
#INCLUDE "WIN32API.INC"
#INCLUDE "WSOCK32.INC"
and has no globals with the same name as any of the local
variables), it gives a
Error 480: Parameter mismatch, may need ByCopy...
ret = WSAStartup(&H101, wd)

I tried declaring the local variables explicitly by adding LOCAL
to their declarations in case the compiler was confused, as well
as (on a lark) passing them using ByCopy. All I can imagine is
that somehow its still thinking ret = WSAStartup(&H101, wd) refers
to something else...



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[Michael Burns]

Found the problem. There *WAS* a duplicate declaration of the
data type WSAData in my applicaton. Thanks again for the solution.

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