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how to read a specific octet from the dest IP in Lua

0

What's the Lua to get a specific octet out of the destination IP address of a packet?

asked 14 Feb '12, 01:32

Leena's gravatar image

Leena
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accept rate: 0%

edited 15 Feb '12, 06:06

helloworld's gravatar image

helloworld
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By "check", do you mean "get the value of"?

Where is this IP from? The source IP address of a packet? A buffer? An Address variable?

(14 Feb '12, 09:35) bstn

I get the ip address from wireshark using lua and then I want to be free in making any process I want in each octet in the destination ip address with Lua.

(14 Feb '12, 23:34) Leena

One Answer:

1

The packet's IP destination is contained in pinfo.dst, which is an Address, which only gives the string representation of the IP address. You can use Lua patterns (similar to regular expressions) to parse the individual octets from the IP address, as shown in the following example:

function tap.packet(pinfo, buffer)
    local ip = tostring(pinfo.dst)
    local o1,o2,o3,o4 = ip:match("(%d%d?%d?)%.(%d%d?%d?)%.(%d%d?%d?)%.(%d%d?%d?)" )
    print(o1,o2,o3,o4)
end

Note that the values (o1, o2, etc.) are of string type. Use number conversion if necessary (i.e., tonumber(o1), tonumber(o2), etc.).

answered 15 Feb '12, 14:58

helloworld's gravatar image

helloworld
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accept rate: 28%

Thanks very much Helloworld, you always helps me a lot.

(15 Feb '12, 23:00) Leena

Please accept the answer by clicking on the "tick" if it solves your issue.

(16 Feb '12, 03:31) grahamb ♦