From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:59019) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UHccS-0003im-CN for qemu-devel@nongnu.org; Mon, 18 Mar 2013 12:09:07 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UHcc7-0006Va-5r for qemu-devel@nongnu.org; Mon, 18 Mar 2013 12:09:04 -0400 Received: from mail-we0-x236.google.com ([2a00:1450:400c:c03::236]:35482) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UHcc6-0006VR-U5 for qemu-devel@nongnu.org; Mon, 18 Mar 2013 12:08:43 -0400 Received: by mail-we0-f182.google.com with SMTP id t57so5105125wey.13 for ; Mon, 18 Mar 2013 09:08:42 -0700 (PDT) Date: Mon, 18 Mar 2013 17:08:39 +0100 From: Stefan Hajnoczi Message-ID: <20130318160839.GD13065@stefanha-thinkpad.redhat.com> References: <1363392758-15228-1-git-send-email-sfeldma@cumulusnetworks.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1363392758-15228-1-git-send-email-sfeldma@cumulusnetworks.com> Subject: Re: [Qemu-devel] [PATCH] net: increase buffer size to accommodate Jumbo frame pkts over netdev UDP socket List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: sfeldma@cumulusnetworks.com Cc: aliguori@us.ibm.com, stephanha@redhat.com, qemu-devel@nongnu.org On Fri, Mar 15, 2013 at 05:12:38PM -0700, sfeldma@cumulusnetworks.com wrote: > From: Scott Feldman > > Socket buffer sizes were hard-coded to 4K. Bump this up to 12K to handle typical > MTU=9000 Jumbo frame pkt. Ran into this limitation when using -netdev UDP sockets > to connect VM-to-VM, where VM interface is configure with MTU=9000. Using > virtio_net NIC model. Test is simple: ping -M do -s 8500 . This test > will attempt to ping with unfragmented packet of given size. Without patch, > size is limited to < 4K (minus protocol hdrs). With patch, ping test works > with pkt size up to 9000 (again, minus protocol hdrs). > > Signed-off-by: Scott Feldman > --- > net/net.c | 2 +- > net/socket.c | 4 ++-- > 2 files changed, 3 insertions(+), 3 deletions(-) grep reveals that VDE is limited in a similar way. tap-win32 may be affected too. I noticed that Linux tap goes straight for: net/tap.c:#define TAP_BUFSIZE (4096 + 65536) The 4096 is reserved for network/virtio headers. Please move TAP_BUFSIZE to include/net/net.h and rename it to NET_BUFSIZE. Then socket, vde, and tap-win32 can use it. Stefan