linux-kernel - RE: IP options IP_RECVOPTS on Linux 2.6

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Message-ID: <402249329CEF3E49AACD14423D8386EE03C6B60D@SACEXCMBX03-PRD.hq.netapp.com>
Date:	Fri, 27 Apr 2012 05:34:33 +0000
From:	"S, Sreeram" <Sreeram.S@...app.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	Ravishankar <cyberax82@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andy Lutomirski <luto@....edu>
Subject: RE: IP options IP_RECVOPTS on Linux 2.6 - Kindly comment

Thanks Eric.
I shall try that and I will reply. Thanks for the hint.

Regards,
Sreeram

-----Original Message-----
From: Eric Dumazet [mailto:eric.dumazet@...il.com] 
Sent: Friday, April 27, 2012 11:02 AM
To: S, Sreeram
Cc: Ravishankar; linux-kernel@...r.kernel.org; Andy Lutomirski
Subject: RE: IP options IP_RECVOPTS on Linux 2.6 - Kindly comment

On Fri, 2012-04-27 at 05:25 +0000, S, Sreeram wrote:
> Thanks a lot Ravi for the response.
> 
> But, the IP header is 40 bytes and so I think I should expect all 
> those 40 bytes to be returned to my program when I enable this option.
> Isnt that correct ?
> 
> Here, TTL and TOS are getting returned because I have explicitly 
> enabled the returns of IP_RECVTTL and IP_RECVTOS to my program using 
> setsockopt. Otherwise even they wouldn’t have been returned.
> 
> I still think that the kernel is not returning what it should return 
> when I enable IP_RECVOPTS. Please correct me if you think I am wrong.
> 
>  
> 
> Also, what are the other ways of getting the IP header other than RAW 
> sockets, if the current approach does not work?
> 
>  

IP options are not IP header.

Try to send an IP packets with options, and your program will work.