[Cerowrt-devel] Cerowrt 3.7.2-4 released, multicast (PIM and IGMP) fixed, kernel matches 3.3.8 again

Dave Taht dave.taht at gmail.com
Thu Jan 17 14:28:08 EST 2013

On Thu, Jan 17, 2013 at 2:10 PM, Maciej Soltysiak <maciej at soltysiak.com>wrote:

> On Thu, Jan 17, 2013 at 2:41 PM, Dave Taht <dave.taht at gmail.com> wrote:
>> It turned out the igmp entries in /proc ARE being  stripped out by a
>> openwrt patch... which I killed... so I built it again....
> What was the purpose of the patch, do you know?

A somewhat misguided attempt at "saving space"

>> Hopefully this will resolve the dlna issue and others.
> It does, my wired TV and my wireless client work without a single change
> of config!


> However I got hit by the DNS / polipo bug with things like:
> Jan 17 18:41:43 OpenWrt user.err polipo[2765]: Host mail.soltysiak.comlookup failed: Timeout (131072).
> Jan 17 18:41:43 OpenWrt user.info sysinit: Host mail.soltysiak.com lookup
> failed: Timeout (131072).
> Jan 17 18:41:44 OpenWrt user.err polipo[2765]: Host notify5.dropbox.comlookup failed: Timeout (131072).
> Jan 17 18:41:44 OpenWrt user.info sysinit: Host notify5.dropbox.comlookup failed: Timeout (131072).
> Jan 17 18:43:27 OpenWrt user.err polipo[2765]: Host notify5.dropbox.comlookup failed: Timeout (131072).
> Jan 17 18:43:27 OpenWrt user.info sysinit: Host notify5.dropbox.comlookup failed: Timeout (131072).
> Funny is that I didn't see them with 3.7.1-1.

As I keep noting, it seems to take time to occur. Try usednsgethostbyname =
true for a while. (can't remember the capitalization)

I'd love to nail this bug one one day because proxies really help on wifi
in particular.... but next up on my todo list this week
is nailing the last few traps and then thoroughly exercising ipv6. (in
addition to a bunch of ns2 based sim work,
which is actually my primary task)

Some full packet captures from localhost when it starts failing would be
useful. Also try it talking to localhost via ::1.

>> BTW:
>> I had a little fun with uftp and uftpd with this (which are capable
>> of thoroughly exercising multicast and igmp)
>> http://www.tcnj.edu/~bush/uftp.html
>> Basically setting up a uftpd client on a couple of machines and
>> initiating uftp from the router, or vice versa, I was able to transfer
>> multiple files around at the same time to multiple machines
>> over wifi and wired.
>> I've long yearned to have time to truly benchmark multicast
>> at scale, and that's why uftp has been in there so long...
>> To setup uftpd on cero (the file receiving deamon)
>> uftpd -I se00,sw00,sw10,gw00,gw10 -D /tmp # or somewhere
> uftp and uftpd don't seem to be in cero repository.
> downloads.openwrt.org/snapshot/trunk/... has version 3.6.1, the latest
> version is 3.7.1; the best thing would be to update upstream openwrt.

It's there.

opkg update
opkg install uftpd uftp

I uypdated my version to 3.7.1, will push the patches out to openwrt as
soon as I get a few more cleanups.

>> To send a file from somewhere to a listening uftpd
>> uftp -I the_interface thefile
> To be super weird, I used a 3.7.1 win32 client and 3.6.1 openwrt
> daemon. speed I got wasn't very high, example:
> D:\TEMP>uftp DSC00160.JPG
> UFTP version 3.7.1  Copyright (C) 2001-2012  Dennis A. Bush
> Starting at Thu Jan 17 20:06:33 2013
> Transfer rate: 1000 Kbps (125 KB/s)
> Wait between packets: 11718 us
> Using private multicast address  Group ID: 033D43BF
> Initializing group
> Sending ANNOUNCE 1
> Received REGISTER from client
> Received REGISTER+ from client
> Sending REG_CONF 2.1
> Sending ANNOUNCE 2
> ----- DSC00160.JPG -----
> File ID: 0001  Name: DSC00160.JPG
>   sending as: DSC00160.JPG
> Bytes: 869125  Blocks: 602  Sections: 1
> Sending FILEINFO 1.1
> Received INFO_ACK from client
> Maximum file transfer time: 20 seconds
> Sending file...pass 1
> Sending DONE 1.1
> Got COMPLETE from client
> Average wait time = 11738.89 us
> Received 0 distinct NAKs for pass 1
> Transfer status:
> Host:     Status: Completed   time:   7.082 seconds    NAKs: 0
> Total elapsed time: 7.082 seconds
> Overall throughput: 119.84 KB/s
> -----------------------------
> Finishing group
> Sending DONE 1.1
> Got COMPLETE from client
> Late completions:
> Sending DONE_CONF 2.1
> Group complete
> uftp: Finishing at Thu Jan 17 20:06:56 2013
> Regards,
> Maciej

uftp is a VERY interesting protocol. For starters it defaults to a very low
rate, which you can change,
which is what I think you just saw here. If you aren't getting NAKs you
aren't saturating your network.
Try a gigabit. :)

if you want to blow up your wifi, feel free to set it high. I have high
hopes that fq_codel will
still do something of the right thing with it, but as multicast packets
have a high "weight",
am not particularly hopeful. Need to script a test or three with it, now
that it works.

Secondly, it has a user configurable congestion control algorithm which is
also very interesting,
and yet very primitive.

Thirdly, it can multicast encrypted it's content. That's a pretty unique

The web page describes its primary use case (distributing articles over
satellite), I have a ton of

1) Keeping core files in sync across a network (think dns)
2) generating varying loads to route across wired and wifi with the
to test stuff with
3) blowing up igmp on bridges and elsewhere
4) sharing dns caches
5) co-existing with ccnx
6) video content (well, this is better done via vlc)
7) synchronized distributed audio content (linux's sound daemons can do

I always liked multicast's promise, going back 2 decades now. I'll try not
to fool with it too much,
but I have to admit it can be like wet paint once you get it working right.

Dave Täht

Fixing bufferbloat with cerowrt:
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