From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Frederic Sowa Subject: Re: Does IPv6 support Jumbograms ? Date: Wed, 9 Apr 2014 22:35:15 +0200 Message-ID: <20140409203515.GF27255@order.stressinduktion.org> References: <5345A2B3.7040602@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Cc: netdev@vger.kernel.org To: Francois WELLENREITER Return-path: Received: from order.stressinduktion.org ([87.106.68.36]:33413 "EHLO order.stressinduktion.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933885AbaDIUfR (ORCPT ); Wed, 9 Apr 2014 16:35:17 -0400 Content-Disposition: inline In-Reply-To: <5345A2B3.7040602@gmail.com> Sender: netdev-owner@vger.kernel.org List-ID: Hi! On Wed, Apr 09, 2014 at 09:42:43PM +0200, Francois WELLENREITER wrote: > I've been recently running performance tests with the loopback interface > increasing the MTU over the 65535 byte limit. > I was really surprised to see that a simple scp onto the ::1 address > systematically blocked after transferring about 2,4 MB. > My interpretation of this behavior is that the current IPv6 kernel layer > does not support Jumbograms at all. Am I wrong ? > If that's not the case, what could then the right interpretation of this > issue ? > And whenever I'm right, is there any plan to support this feature in a > near future ? IPv6 should handle the reception of jumbo frames quite fine, even the UDP size override IIRC. But there is no support for large outgoing UDP frames, and I currently don't know about TCP-MSS override works. I guess you should be able to send jumbos with rawsocket if you attach the dsthop header manually, but I have never tried it (maybe it will get blocked by some check in ip6_output, HDRINCL and H-b-H option setsockopt could work also). I currently don't see the need for that option if no one also takes care about UDP and TCP paths, so I guess support is coming as soon as someone cares. ;) Greetings, Hannes