Linux Kernel Module program to obtain domain name from IP

[Sudip Mukherjee]

On Tue, Jul 8, 2014 at 4:52 PM, shhuiw <shhuiw at 163.com> wrote:
> Hi,
>
> I think you need refer to some open source DNS client utilities, e.g
> http://en.wikipedia.org/wiki/Nslookup.
>
> - shhuiw

just have a look at the source code of nslookup command ... it does
the same thing as what u want ...

but in many cases it will not work , as many domain names have shared
ip address .


>
>
> At 2014-07-08 06:26:23, "Hettiarachchige Hasitha Shan" <hh_shan at live.com>
> wrote:
>
> I have a requirement to obtain the domain name from the destination IP from
> an outgoing packet. I am successful in capturing and obtaining the
> destination IP  packets using the `netfilter` hook as shown below.
>
>     unsigned int hook_func_out(unsigned int hooknum, struct sk_buff * skb,
> const struct net_device *in, const struct net_device *out, int
> (*okfn)(struct sk_buff*))
>     {
>
>         ofs = 20;    // Set theoffset to skip over the IP header.
>
>         {
>                 struct iphdr *ip_header = (struct iphdr
> *)skb_network_header(skb);
>                 struct udphdr *udp_header;
>                 struct tcphdr * tcp_header;
>
>             //Ican obtain the destination IP address of the packet
>             //like this
>             unsigned int dest_ip = (unsigned int)ip_header->daddr;
>
>             //or like this
>             char pkt_tbuf[16];
>             snprintf(pkt_tbuf, 16, "%pI4", &ip_header->daddr);
>
>             //here I need to obtain the domain name of the obtained
> destination address
>         }
>     }
>
> However, I have no idea on how to use that IP to obtain the domain name of
> the obtained IP.
>
> I tried many sources
> (https://www.google.com/search?client=ubuntu&channel=fs&q=linux+kernel+programming+domain+name+from+IP+&ie=utf-8&oe=utf-8)
> but did find any related information on the subject and will be really
> grateful if you experts would provide any sample code/ references to perform
> this task :)
>
> Thank you very much :)
>
>
>
>
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