From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: sock_get_timestamp() ktime_to_timeval returns -2? Date: Sat, 05 Apr 2008 14:38:31 +0200 Message-ID: <47F772C7.6020700@cosmosbay.com> References: <013101c89683$1bd00940$0a00a8c0@Andrew> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="------------060809020002040004020002" Cc: netdev@vger.kernel.org To: Andrew Brampton , "David S. Miller" Return-path: Received: from neuf-infra-smtp-out-sp604007av.neufgp.fr ([84.96.92.120]:40527 "EHLO neuf-infra-smtp-out-sp604007av.neufgp.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751725AbYDEMif (ORCPT ); Sat, 5 Apr 2008 08:38:35 -0400 In-Reply-To: <013101c89683$1bd00940$0a00a8c0@Andrew> Sender: netdev-owner@vger.kernel.org List-ID: This is a multi-part message in MIME format. --------------060809020002040004020002 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit Andrew Brampton a écrit : > Hi, > I'm using the following piece of code to record the received time of my > packets. > > struct timeval tv = {0,0}; > if ( ioctl(s, SIOCGSTAMP, &tv) ) > return 0; > > When I use UDP this is all great, but when I use TCP this stops working. > I have since found out that I can't use this for TCP packets[1], but the > reason I'm writing this email is because ioctl returns zero when using > TCP and tv has a odd value in it. tv.tv_sec = -2, and tv.tv_usec = 999999. > > Now I assume -2 is some kind of error code, so I dug into the linux code > to try and figure out what it means. The ioctl eventually calls > sock_get_timestamp() which in turn calls ktime_to_timeval. I can see in > sock_get_timestamp() that tv_sec is compared to -1 and ioctl returns an > error, however I can not find where tv_sec is set to -2. If -2 is > another error code then it should be checked inside sock_get_timestamp(). > > So I'm wondering if this is a bug in the kernel somewhere, or should I > just expect ioctl to fail yet return 0? I have not included a test app, > but if you want I'll be happy to code a short app to show this problem, > but the critital lines are the ioctl call and that a TCP socket is used. > This occurs on both the 2.6.22-3-amd64 kernel as well as on 2.6.24. I believe the following patch should make sure ENOENT is delivered to the application. And yes, SIOCGSTAMP has a meaning only for UDP or other packet protocols. Thank you Andrew for spotting this bug. [SOCK] sk_stamp: should be initialized to ktime_set(-1L, 0) Problem spotted by Andrew Brampton Signed-off-by: Eric Dumazet --------------060809020002040004020002 Content-Type: text/plain; name="sk_stamp.patch" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="sk_stamp.patch" diff --git a/net/core/sock.c b/net/core/sock.c index 2654c14..7a0567b 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -1725,7 +1725,7 @@ void sock_init_data(struct socket *sock, struct sock *sk) sk->sk_rcvtimeo = MAX_SCHEDULE_TIMEOUT; sk->sk_sndtimeo = MAX_SCHEDULE_TIMEOUT; - sk->sk_stamp = ktime_set(-1L, -1L); + sk->sk_stamp = ktime_set(-1L, 0); atomic_set(&sk->sk_refcnt, 1); atomic_set(&sk->sk_drops, 0); --------------060809020002040004020002--