linux-kernel - Re: UDP requires 2 reads to obtain vital information

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Message-ID: <4E42C4B5.7010201@mit.edu>
Date:	Wed, 10 Aug 2011 13:49:41 -0400
From:	Andy Lutomirski <luto@....EDU>
To:	Sreeram B S <sreeramb@...app.com>
CC:	linux-kernel@...r.kernel.org
Subject: Re: UDP requires 2 reads to obtain vital information - Kindly comment

On 08/10/2011 12:57 PM, Sreeram B S wrote:
> Respected people,
> I am Sreeram. I work on TCP/IP network applications.
> This mail is regarding UDP.
> Whenever a UDP datagram arrives, the receiver may wish to know the
> sender's IP address and also the destination address of that datagram.
> The recvfrom() function will return the sender's IP address. If the
> destination address of the datagram is required, then the user has to
> set the IP_PKTINFO socket option for the UDP socket and get the
> address as ancillary data in recvmsg(). So, the point here is that the
> user has to issue 2 reads on the same datagram (with the flag MSG_PEEK
> in first read call enabled) in order to obtain the sender's IP and the
> destination IP of the datagram.

Does the msg_name field of struct msghdr not work?

--Andy
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