Date: Sun, 6 Feb 2011 16:22:36 -0800 From: Pyun YongHyeon <pyunyh@gmail.com> To: Ronald Klop <ronald-freebsd8@klop.yi.org> Cc: freebsd-net@freebsd.org, rmacklem@uoguelph.ca, sthaug@nethelp.no Subject: Re: bogus 0 len IP packet, was: Hang in VOP_LOCK1_APV on 8-STABLE with NFS. Message-ID: <20110207002235.GA1244@michelle.cdnetworks.com> In-Reply-To: <op.vqh69nx08527sy@212-123-145-58.ip.telfort.nl> References: <op.vpekz9uz8527sy@212-123-145-58.ip.telfort.nl> <708793006.292748.1295186099577.JavaMail.root@erie.cs.uoguelph.ca> <20110117005524.GA1305@michelle.cdnetworks.com> <20110118.093804.74673434.sthaug@nethelp.no> <op.vpokw9c58527sy@pinky> <op.vqh69nx08527sy@212-123-145-58.ip.telfort.nl>
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On Sun, Feb 06, 2011 at 11:54:49PM +0100, Ronald Klop wrote: > On Sat, 22 Jan 2011 00:01:47 +0100, Ronald Klop > <ronald-freebsd8@klop.yi.org> wrote: > > >On Tue, 18 Jan 2011 09:38:04 +0100, <sthaug@nethelp.no> wrote: > > > >>>> So, does anyone have an idea why the IP length field would be set to > >>>0 > >>>> for these TCP/IP packets? > >>>> > >>>> Here's some info from Ronald w.r.t. his hardware. (All I can think > >>>of is > >>>> that he could try disabling TSO, etc?) > >>>> > >>>> Thanks in advance for any help with this, rick > >>>> > >>> > >>>It seems that issue came from TSO. Driver will set ip_len and > >>>ip_sum field to 0 before passing the TCP segment to controller. > >>>The failed length were 4446, 5858, 3034 and 4310 and the total > >>>number of such frames are more than 35k within 90 seconds. Since > >>>failed length 4310 is continuously repeated I guess there is edge > >>>case where em(4) didn't free failed TCP segment for TSO. > >>>I remember there was commit to HEAD(r217295) which could be related > >>>with this issue. > >> > >>I'm seeing the same problem with Broadcom NetXtreme (bce) cards: > >> > >>bce0@pci0:3:0:0: class=0x020000 card=0x03421014 chip=0x164c14e4 > >>rev=0x12 hdr=0x00 > >> vendor = 'Broadcom Corporation' > >> device = 'Broadcom NetXtreme II Gigabit Ethernet Adapter > >>(BCM5708)' > >> class = network > >> subclass = ethernet > >> > >>This is with 8.2-PRERELEASE. Turning off TSO (ifconfig bce0 -tso) > >>removes the problem. > >> > >>Steinar Haug, Nethelp consulting, sthaug@nethelp.no > >>_______________________________________________ > >>freebsd-net@freebsd.org mailing list > >>http://lists.freebsd.org/mailman/listinfo/freebsd-net > >>To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org" > > > >I tried -tso and -txcsum in various combinations, but it didn't solve > >the problem. I wil look for another brand of network card to try. But > >this has to wait till monday when I'm at the office again. > > I also used another network card (rl0) and it has the same problem with > NFS. I'm going to change some network cables to see if that helps. I have > some hints that there might be something wrong with that. > Hmm, given that rl(4) also shows the issue it seems the issue could be in TCP/IP stack, not in driver side. rl(4) is dumb device so network stack should do segmentation and checksum computation. I highly doubt the issue came from faulty cable since other users also reported the same issue. Unfortunately I have no clue yet and I was not able to reproduce it on my box. I vaguely guess some code in kernel changed the ip_len to 0 in the middle of transmission. Rick's captured traffic looks normal except 0 ip_len given that controller is computing checksum on the fly. If mbuf chain was corrupted(e.g. m_len == 0) driver would have failed to send those frames. > Ronald.
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