Modify the sock Structure!!

Modify the sock Structure!!

[Benjamin]

Hello! I try to modify the sock Structure in sock.h in order to record 
some data!
I just add a unsigned short in the end of the structure. such as:

struct sock {
    /* Socket demultiplex comparisons on incoming packets. */
    __u32            daddr;        /* Foreign IPv4 addr            */
    __u32            rcv_saddr;    /* Bound local IPv4 addr        */

         ...................................................................
        ....................................................................



  void                    (*destruct)(struct sock *sk);
  unsigned short        data;                 /*I put the unsigned short 
here*/
};



 I re-complied the kernel.  The kernel and network functions work 
normally so far.
However, I am a new guy for the kernel programming. I just wonder this 
modification is
safe or not. Is there any side-effect? Or I need to add additional code 
to avoid some unexpected
situation?  Thank you very much!
 

Re: Modify the sock Structure!!

[Jan Engelhardt]

> Hello! I try to modify the sock Structure in sock.h in order to record some
> data!
> I just add a unsigned short in the end of the structure. such as:
>
> struct sock {

> safe or not. Is there any side-effect? Or I need to add additional code to
> avoid some unexpected
> situation?  Thank you very much!


Should be ok. For example, ipt_TPROXY/ipt_tproxy also adds something to 
struct sock (including enlarging fields in the middle of the struct);
I have not experienced any problem with it.


Jan Engelhardt
-- 

Re: Modify the sock Structure!!

[Benjamin]

Cool! Thanks for the answer!

Best Regards,

Benjamin Chu

Jan Engelhardt wrote:
>> Hello! I try to modify the sock Structure in sock.h in order to record some
>> data!
>> I just add a unsigned short in the end of the structure. such as:
>>
>> struct sock {
>>     
>
>   
>> safe or not. Is there any side-effect? Or I need to add additional code to
>> avoid some unexpected
>> situation?  Thank you very much!
>>     
>
>
> Should be ok. For example, ipt_TPROXY/ipt_tproxy also adds something to 
> struct sock (including enlarging fields in the middle of the struct);
> I have not experienced any problem with it.
>
>
> Jan Engelhardt
>