From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rick Jones Subject: Re: TCP_MAXSEG option with TSO enabled Date: Fri, 30 Mar 2012 10:38:00 -0700 Message-ID: <4F75EF78.4060402@hp.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org To: Daniel Baluta Return-path: Received: from g1t0026.austin.hp.com ([15.216.28.33]:6714 "EHLO g1t0026.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751741Ab2C3RiD (ORCPT ); Fri, 30 Mar 2012 13:38:03 -0400 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On 03/30/2012 04:33 AM, Daniel Baluta wrote: > Hello, > > I am using TCP_MAXSEG option on an interface which has TSO enabled. > > strace output for connection looks as follows: > > socket(PF_INET, SOCK_STREAM, IPPROTO_IP) = 26 > setsockopt(26, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0 > setsockopt(26, SOL_TCP, TCP_NODELAY, [1], 4) = 0 > setsockopt(26, SOL_TCP, TCP_MAXSEG, [300], 4) = 0 > connect(26, {sa_family=AF_INET, sin_port=htons(1935), > sin_addr=inet_addr("10.10.0.1")}, 16) = -1 EINPROGRESS (Operation now > in progress) > > I can see that MSS (300) is advertised in SYN packet, anyhow capturing > the traffic > I notice that are some TCP segments with length greater than MSS. > > Is this normal taking in consideration that TSO is enabled? I would think so. What do the netstat stats suggest for segments and bytes per segment when you are running your test? You could always look for an on-the-wire packet trace. Not sure that a trace on a receiver would give you that though - the inbound promiscuous tap may be above GRO (and almost certainly will be above LRO) rick jones > > thanks, > Daniel. > -- > To unsubscribe from this list: send the line "unsubscribe netdev" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html