linux-kernel - Re: how to read one udp packet with more than one recvfrom() calls?

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 8 Nov 2010 15:12:00 +0800
From:	Changli Gao <xiaosuo@...il.com>
To:	ranjith kumar <ranjithproxy@...il.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: how to read one udp packet with more than one recvfrom() calls?

On Mon, Nov 8, 2010 at 3:08 PM, ranjith kumar <ranjithproxy@...il.com> wrote:
> Hi,
>
> I  have implemented client and server programs using udp
> protocol(files are attached).
> UDP packet size is 500bytes.
>
> I want to read these 500bytes in two calls to recvfrom(). First time
> reading 100bytes and second time 400bytes.
> How to do this?
>
> When I tried to change the third argument of recvfrom(size_t len),
> from 500 to 100, first 100bytes are read correctly.
> But when I call recvfrom() second time with len=400, it is reading the
> first 400bytes of "next udp packet".
> Why? Isn't it possible to read one udp packet in two calls to
> recvfrom()/read()????
>

recvmsg(2):

       MSG_PEEK
              This  flag  causes the receive operation to return data from the
              beginning of the receive queue without removing that  data  from
              the queue.  Thus, a subsequent receive call will return the same
              data.

-- 
Regards,
Changli Gao(xiaosuo@...il.com)
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/