Date: Wed, 20 Jan 2016 00:47:55 +0100 From: Luigi Rizzo <rizzo@iet.unipi.it> To: Garrett Wollman <wollman@freebsd.org>, Giuseppe Lettieri <g.lettieri@iet.unipi.it> Cc: "freebsd-net@freebsd.org" <freebsd-net@freebsd.org> Subject: Re: Another issue with ixl(4) with netmap Message-ID: <CA%2BhQ2%2BiGaHS_8PJiXyKu1kUiFuono-T-TAUAyK7v7BnkV4iR6Q@mail.gmail.com> In-Reply-To: <22174.51361.2022.984959@hergotha.csail.mit.edu> References: <22174.51361.2022.984959@hergotha.csail.mit.edu>
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Interesting report, thanks. My colleague Giuseppe can have a look at this. While not sure about the actual issue I can tell you that generally we try to include checksums in drivers that support netmap, because PCIe bus transactions are faster for transfers that are multiple of 64 bytes and aligned to those boundaries. Keeping the CRC (and doing the stripping in software) makes the requirement for min-sized packets, which are a common test case. The symptoms you see suggest a mismatch on who is doing the CRC stripping, which seems to occur twice; what is strange is that in case i would expect the opposite error, i.e. disable stripping in the hardware and forget to enable it in the software. cheers luigi On Wed, Jan 20, 2016 at 12:37 AM, Garrett Wollman <wollman@freebsd.org> wrote: > I noticed that a large number -- but by no means all -- of the packets > captured using libpcap on a netmap'ified ixl(4) interface show up as > truncated -- usually by exactly four bytes. They show up in tcpdump > like this: > > 18:10:05.348735 IP truncated-ip - 4 bytes missing! 128.30.xxx.xxx.443 > yyy.yyy.yyy.yyy.54711: Flags [P.], seq 3151716053:3151716112, ack 3109956633, win 31, length 59 > 18:10:05.348735 IP truncated-ip - 4 bytes missing! zzz.zzz.zzz.zzz.17376 > 128.30.aaa.aaa.80: Flags [.], ack 1771224170, win 12775, options [nop,nop,sack 1 [|tcp]> > 18:10:05.348735 IP truncated-ip - 4 bytes missing! zzz.zzz.zzz.zzz.17376 > 128.30.aaa.aaa.80: Flags [.], ack 1, win 12775, options [nop,nop,sack 1 [|tcp]> > > This does not occur when the same interface is used with BPF (but > libpcap can't keep up with the traffic when using BPF). Has anyone > see this before, and if so, what was the solution? (This is on 10.2 > with the ixl(4) updates merged from 10-stable.) > > -GAWollman > _______________________________________________ > freebsd-net@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-net > To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org" -- -----------------------------------------+------------------------------- Prof. Luigi RIZZO, rizzo@iet.unipi.it . Dip. di Ing. dell'Informazione http://www.iet.unipi.it/~luigi/ . Universita` di Pisa TEL +39-050-2217533 . via Diotisalvi 2 Mobile +39-338-6809875 . 56122 PISA (Italy) -----------------------------------------+-------------------------------
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