kernel module acquiring virtual ip's

kernel module acquiring virtual ip's

[Sachin Shelar]

Hi,

    I have a kernel module which "acquires" virtual ips ( not assigned to  
anyone in n/w )
and then respond to any future packets coming to this virtual ip.
    I am handling ARP, TCP, UDP protocols in my module.
To get the arp stuff working I handle all the ARP requests for virtual IP  
and reply to
them with my local hardware address. I can now receive all the packets  
destined to virtual IP.
    E.g Local IP is 192.168.1.2
        Virtual ip is 192.168.1.244 ( Not existing in network )

        I catch every arp request for .244 and reply with my mac. I can now
recive all IP packets ( handled in my netfilter hooks ) destined for .244.
According to the natting rules in my module I nat the packets for .244 and  
redirect them to
some listening port on 192.168.1.2
Also I handle all the outgoing packet from 192.168.1.2 and replace the  
source to 192.168.1.244
So that the client machine recives reply from virual IP, as expected.

         192.168.1.21[32774] -> 192.168.1.244[123]

                          Nat Destination   192.168.1.21[32774] ->  
192.168.1.2[23]

(Reply) 192.168.1.2[23] -> 192.168.1.21[32774]
                          Nat Source        192.168.1.244[123] ->  
192.168.1.21[32774].



    Module works perfectly and I can establish any tcp connection ( E.g  
telnet ) with a non exitsing
IP ( 192.168.1.244) from any machine in the network.

    Problem is :-
    I want the same behaviour from the module if I try to connect from the  
same machine (local machine )
to the virtual IP.

     E.g 192.168.1.2[32772] -> 192.168.1.244[123]

                         Nat Destination   192.168.1.2[32772] ->  
192.168.1.2[23]

***** But somehow this packet after natting is dropped be the kernel and  
never reaches 192.168.1.2[23]
       Is this because the source and destination ip of this packet is same  
?????

     Hoping to get good reponse for this loooong mail :)

Thanks,
Sachin

kernel module acquiring virtual ip's

[Sachin Shelar]

Hi,

    I have a kernel module which "acquires" virtual ips ( not assigned to   
anyone in n/w )
and then respond to any future packets coming to this virtual ip.
    I am handling ARP, TCP, UDP protocols in my module.
To get the arp stuff working I handle all the ARP requests for virtual IP   
and reply to
them with my local hardware address. I can now receive all the packets   
destined to virtual IP.
    E.g Local IP is 192.168.1.2
        Virtual ip is 192.168.1.244 ( Not existing in network )

    I catch every arp request for .244 and reply with my mac. I can now
recive all IP packets ( handled in my netfilter hooks ) destined for .244.
According to the natting rules in my module I nat the packets for .244  
and  redirect them to
some listening port on 192.168.1.2
Also I handle all the outgoing packet from 192.168.1.2 and replace the   
source to 192.168.1.244
So that the client machine recives reply from virual IP, as expected.

         192.168.1.21[32774] -> 192.168.1.244[123]

                          Nat Destination   192.168.1.21[32774] ->   
192.168.1.2[23]

(Reply) 192.168.1.2[23] -> 192.168.1.21[32774]
                          Nat Source        192.168.1.244[123] ->   
192.168.1.21[32774].



    Module works perfectly and I can establish any tcp connection ( E.g   
telnet ) with a
non exitsing IP ( 192.168.1.244) from any machine in the network.

Problem is :-
===========
    I want the same behaviour from the module if I try to connect from the   
same machine (local machine )
to the virtual IP.

     E.g 192.168.1.2[32772] -> 192.168.1.244[123]

                         Nat Destination   192.168.1.2[32772] ->   
192.168.1.2[23]

***** But somehow this packet after natting is dropped by the kernel and   
never reaches
192.168.1.2[23]
       Is this because the source and destination ip of this packet is  
same  ?????
       Whats the solution for sending a packet with local ip as its src and  
dst
to local from POSTROUTING hook


Thanks,
Sachin