Date: Tue, 22 Oct 2013 10:01:07 +0200 From: Andre Oppermann <andre@freebsd.org> To: Colin Percival <cperciva@freebsd.org>, Julian Elischer <julian@freebsd.org>, freebsd-net@freebsd.org Subject: Re: LRO causing stretch ACK violations interacts badly with delayed ACKing Message-ID: <526630C3.4090008@freebsd.org> In-Reply-To: <52659569.8090301@freebsd.org> References: <52605EC9.6090406@freebsd.org> <526478D0.1000601@freebsd.org> <5264869E.4000308@freebsd.org> <5265450C.1060601@freebsd.org> <526558D2.3010505@freebsd.org> <52658726.4030106@freebsd.org> <52658A79.6070705@freebsd.org> <52659569.8090301@freebsd.org>
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On 21.10.2013 22:58, Colin Percival wrote: > On 10/21/13 13:11, Andre Oppermann wrote: >> On 21.10.2013 21:57, Andre Oppermann wrote: >>> This is an excellent observation! Our tcp doesn't know about LRO >>> and I prepared the mbuf header to carry information about the number >>> of merged LRO segments. That's not done yet again. However a small >>> heuristic in tcp_input looking for segment > mss should be sufficient >>> for now. Let me have a look at patching it into a suitable place. >> >> Please check out the patch below. Haven't tested it myself yet though. > > Yes, this works: >> 00:00:00.000000 IP 10.148.229.78.24405 > 176.32.98.166.443: Flags [S], seq 3220740500, win 65535, options [mss 1460,nop,wscale 6,sackOK,TS val 350742 ecr 0], length 0 >> 00:00:00.000613 IP 176.32.98.166.443 > 10.148.229.78.24405: Flags [S.], seq 1783557911, ack 3220740501, win 8190, options [mss 1460,nop,wscale 6], length 0 >> 00:00:00.000657 IP 10.148.229.78.24405 > 176.32.98.166.443: Flags [.], ack 1, win 1026, length 0 >> 00:00:00.001842 IP 176.32.98.166.443 > 10.148.229.78.24405: Flags [.], ack 1, win 127, length 0 >> 00:00:00.032269 IP 10.148.229.78.24405 > 176.32.98.166.443: Flags [P.], seq 1:318, ack 1, win 1026, length 317 >> 00:00:00.033080 IP 176.32.98.166.443 > 10.148.229.78.24405: Flags [.], ack 318, win 108, length 0 >> 00:00:00.033115 IP 176.32.98.166.443 > 10.148.229.78.24405: Flags [.], seq 1:4097, ack 318, win 108, length 4096 >> 00:00:00.033129 IP 10.148.229.78.24405 > 176.32.98.166.443: Flags [.], ack 4097, win 962, length 0 > > Please commit this fix and get it merged for 10.0-RELEASE! I committed it to my staging branch pending review: http://svnweb.freebsd.org/changeset/base/256879 It should go into HEAD later this week and the MFC to 10.x then depends on re@'s take on it. -- Andre
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