Date: Tue, 11 Sep 2012 22:13:53 -0400 From: George Neville-Neil <gnn@neville-neil.com> To: John-Mark Gurney <jmg@funkthat.com> Cc: freebsd-arm@FreeBSD.org, Tim Kientzle <kientzle@FreeBSD.org> Subject: Re: -current on BeableBone successful Message-ID: <D3516FBB-4617-4C6B-A805-B50E7CC88154@neville-neil.com> In-Reply-To: <20120910064532.GP58312@funkthat.com> References: <20120910014813.GL58312@funkthat.com> <4448530B-7916-4642-BD32-6A96AD5DB22B@FreeBSD.org> <20120910064532.GP58312@funkthat.com>
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On Sep 10, 2012, at 02:45 , John-Mark Gurney <jmg@funkthat.com> wrote: > Tim Kientzle wrote this message on Sun, Sep 09, 2012 at 20:16 -0700: >>> Third is that I get this error: >>> ip length 328 disagrees with bytes received 330. >>> accepting packet with data after udp payload. >>> >>> This appeard to be from sbin/dhclient/packet.c... Not sure exactly why >>> we are returning a large packet to userland? >> >> I haven't seen this one. > > Looks like this is a BeagleBone issue. I haven't tracked it down, but > I did a tcpdump on the server (my other arm board), and the packet has > the correct length of 342 bytes to match the 328 ip length (plus 14 > bytes of ethernet header)... tcpdump on the BeagleBone receives a > 344 byte frame with a couple of stray bytes at the end of the frame... > > Could this be an miscalculation when we are copying around the frame > to deal the fact our IP stack can't deal w/ misaligned headers? Just > a thought.. > > Hmm... Just ran some experiments... > > ping -s sent received > 1 0x2b 0x3e > 10 0x34 0x3e > 18 0x3c 0x3e > 19 0x3d 0x3f > 20 0x3e 0x40 > 21 0x3f 0x41 > 99 0x8d 0x8f > 100 0x8e 0x90 > 101 0x8f 0x91 > 999 0x411 0x413 > 1000 0x412 0x414 > 1001 0x413 0x415 > > and 0x3e is 62, which is two short of the min frame length of 64... > > Hope this helps. My take is the following. The minimum packet is 60, not including the preamble or the CRC, so with a CRC it's 64. It might be that there is some alignment issue as well. The difference between all the sent/received is 2 bytes and that's consistent so either something isn't being stripped or there is an alignment issue all the way round. Best, Georgehome | help
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