Bitwise operator

gmadarm · 2014-07-21T03:00:48+00:00

Hello! I've done2014-07-21 9:51 GMT+06:00 Yichun Zhang (agentzh) <age...@gmail.com>: Hello! On Sun, Jul 20, 2014 at 8:47 PM, Vitaly Kosenko wro...

Bitwise operator

gmadarm

I am trying to convert IP addresses to their ASN. I grabbed a network to ASN mapping from:

http://thyme.apnic.net/current/data-raw-table

and converted the following PHP script to Lua for use in OpenResty:

http://quaxio.com/bgp/

My probelm is that the script works for some IPs, but not for others, for example:
# curl -s localhost/asn?ip=8.8.8.8
IP is: 134744072
ASN: 15169
# curl -s localhost/asn?ip=222.242.105.93
IP is: 3740428637

The actual code was a bit long for an email so I posted it here: http://pastebin.com/Kfwa1nYY

For testing you can simply add the following to redis:
redis-cli SET 134744064 15169
redis-cli SET 3740270592 4134

I believe I have a bug in the bitwise conversion of the long IP. Can someone help explain why the script sometimes returns the correct ASN and sometimes does not?

thanks!
- G

lordnynex

Hello,

At first glance this appears to be a bug in Lua Bitlib. I don't want to give you the impression that I know technically why it's a bug or if it is 'by design'. In a vague way, I guess when a bit is lost during the shift you end up with non-whole numbers. This causes your conversion for the second IP to look like this in your current function:

IP: 3740428637

0: -554538659

1: -554538660

2: -554538660

3: -554538664

4: -554538672

5: -554538688

6: -554538688

7: -554538752

8: -554538752

9: -554539008

10: -554539008

11: -554539008

12: -554541056

13: -554541056

14: -554549248

15: -554565632

16: -554565632

17: -554565632

18: -554696704

19: -554696704

20: -554696704

21: -555745280

22: -557842432

23: -562036736

24: -570425344

25: -570425344

26: -603979776

27: -671088640

28: -805306368

29: -1073741824

30: -1073741824

31: -2147483648

32: -554538659

The solution I've arrived at is to abandon Bitlib all together. Here is my solution: http://pastebin.com/uQV3gZrQ

Also note,

- Your query function does not close your redis connection or return the socket to the connection pool. Please see https://github.com/openresty/lua-resty-redis#set_keepalive

- Your query function does not check the value of err. There may be useful information here.

On Sun, Jul 20, 2014 at 12:00 PM, Gordon Madarm <gma...@gmail.com> wrote:

I am trying to convert IP addresses to their ASN. I grabbed a network to ASN mapping from:

http://thyme.apnic.net/current/data-raw-table

and converted the following PHP script to Lua for use in OpenResty:

http://quaxio.com/bgp/

My probelm is that the script works for some IPs, but not for others, for example:
# curl -s localhost/asn?ip=8.8.8.8
IP is: 134744072
ASN: 15169
# curl -s localhost/asn?ip=222.242.105.93
IP is: 3740428637

The actual code was a bit long for an email so I posted it here: http://pastebin.com/Kfwa1nYY

For testing you can simply add the following to redis:
redis-cli SET 134744064 15169
redis-cli SET 3740270592 4134

I believe I have a bug in the bitwise conversion of the long IP. Can someone help explain why the script sometimes returns the correct ASN and sometimes does not?

thanks!
- G

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