lime-dev January 2014

lime-dev@lists.libremesh.org

7 participants
11 discussions

Issue: asymmetric bmx6 tunnels break PMTUD

by Gui Iribarren

Hey axel! so, we've scratching our heads today, facing some MTU issues on our shiny new libre-mesh network, and after a few hours debugging, tcpdumping and discussing, we came to these conclusions: * the invented src-addr in the bmxOut tunnel makes it impossible for hops along the path to return "Packet Too Big" to the originating node. So, if a particular link has a smaller MTU than the first link (say, a VPN is involved), the packet will be silently dropped. A==1500==B---1400---C===1500===D A wants to send a packet to a network announced by D; so it creates a tunnel with D as destination, and a "D-derived" fake address as src, that matches the bmxIn "catchall" tunnel peer-addr in D Then sends a 1460 + 40 = 1500 bytes packet through that tunnel, B cannot push that packet to C, then tries to send back a ICMPv6 PTB... but the src-addr it finds in the encapsulation is not A, but instead the "D-derived" fake addr. Then, the ICMPv6 PTB is lost and A can never find out about the smaller MTU. This fundamentally breaks PMTUD which is a bad idea in IPv6 to avoid this there are 3 options: * set mtu=1280 on every bmxOut tunnel (yuck! :( ) * probe before establishing each tunnel, with the real src-addr so that PMTUD can happen correctly, until it reaches the desired endpoint node. Then, use discovered PMTU for new tunnel. (*downside*: this will only work as long as path doesn't change to pass through some thinner link. In that case, PMTU will not be rediscovered, and packets will be dropped again.) * use the current bmxIn "catchall" tunnels only for sending special bmx6 control packets, that ask for a symmetric tunnel. i.e. 1) A sends to D (2001:db8::D) a packet (encapsulated with a fake src-addr, to be catched by the catchall @ D) with content "I'm A and this is my real address 2001:db8::A; please make a dedicated tunnel for me" 2) D gets that packet and creates a tunnel with "peer 2001:db8::A", then sends back an ACK to A, again using "A-derived" fake-addr as src 3) A gets the ACK and creates the tunnel with "peer 2001:db8::D" *** now both ends have a symmetric tunnel between them, with real src and dest address *** 4) A finally sends the real payload through the symmetric tunnel, this payload (may be bigger than 1280, say... 1450) will be encapsulated with the real src-addr of A, so if any node in the path needs to send back a Packet-too-big, will be able to, and PMTUD will happen correctly. (at the cost of a full RTT latency before the first payload packet, but with a reasonable tunnel expire time as it has currently, that shouldn't be terrible) back in April, i remember we discussed the idea of symmetric tunnels, and you brought up this "control connection" idea which i'm simply redescribing here. But that discussion was in another context, more like a 'feature', and finally didn't really solve the idea we had originally, yet, this PMTUD issue was not taken into account AFAIR, so the "symmetric tunnel" idea now becomes more like a bugfix (i.e. don't create PMTUD blackholes) what do you think? Cheers!! gui

10 years, 7 months

Telefonica reinventing the wheel ?

by Gioacchino Mazzurco

http://arstechnica.com/business/2014/01/bewifi-lets-you-steal-your-neighbor…

10 years, 10 months

How to update local git repo

by Ilario GELMETTI

Hi all! Some times ago I downloaded and compiled LiMe as suggested on your site: git clone https://github.com/libre-mesh/lime-build.git cd lime-build make T=ar71xx J=4 Now I would like to build an updated image, how should I update all the repositories (openwrt, libre-mesh, luci...)? Is there something like a "make update" ? Thanks 'n' bye, Ilario

10 years, 10 months

Some thoughts about libremap

by Pau

Hello. Some thoughts about my experience with libremap. 1. Routers -> Cluster should be disabled by default IMO 2. Same for filter links, since it is quite common to have "not perfect" links in a wifi community 3. Would be very useful to have more view levels. When there are some routers close you cannot see the specific position. In the other hand, Altermap allows to make quite more zoom, so this should be possible in OSM. 4. Would be nice to have a "LuCi" web plugin to manage the /etc/config/libremap agent. Is there something developed? If not I can do so. 5. I would like to create some specific plugins, for instance to send bmx6 information to the server. I see how the plugins work in the node, but I miss the web page part. Is there some "easy way" to add new plugins in the web page? Cheers! [1] http://libremap.net/#bbox/41.38757144743988,2.108720541000366,41.3898373021… -- ./p4u

10 years, 10 months

some lua libraries and useful code

by Gui Iribarren

some months ago in a sprint, we finally both sat down together with Nico to fight with lua, and at some point stumbled upon this https://github.com/rrthomas/lua-stdlib --[[ This is a collection of Lua libraries for Lua 5.1 and 5.2. You can load the standard set with require "std" ]]--- then i found out about luarocks, which is analog to ruby gems and python pips http://luarocks.org/repositories/rocks/ and from there, other interesting libraries * https://github.com/kikito/inspect.lua This function transform any Lua table into a human-readable representation of that table. The objective here is human understanding (i.e. for debugging), not serialization or compactness. (Dedicated to Nico, a python programmer horrified by lua being unable to print(table)) * https://code.google.com/p/luno/ O projeto Luno tem o objetivo de prover API's para uso com a linguagem de programação Lua que visem a facilitar a execução de tarefas corriqueiras mas que não estão diretamente implementadas pela biblioteca padrão do Lua. Luno conta com os módulos luno.string, luno.table e luno.io. Esses módulos provêem funções extras para manipular strings (trim, split, join, charAt, ...), io (getTextFromFile, ...), tabelas (imprimir tabelas, concatenar, ...). O módulo luno.util provê funções de uso geral como cópia (deep copy) e impressão (deep print) de variáveis. finally, i found the following blogpost enlightening, it's a thorough summary of differences and unexpected things, very helpful for me, dealing with lua for the first time http://notebook.kulchenko.com/programming/lua-good-different-bad-and-ugly-p… hope that helps someone,

10 years, 10 months

Copy an exact firmware from one router to other

by al

Hello, I remember first times with Freifunk firmware (OpenWrt White Russian): They put in main web page a link with a direct download of image that was working in same router. I suposse that it was generated from binaries when you click on. I think is a very good tool to make network bigger with same routers (you don't need to connect to any place to get firmware). Do you know about that? I think we can put it on libre-mesh (and also I need it now to make easy an exact copy from one of our libre-mesh routers here in Garraf).

10 years, 11 months

BattleMesh v7

by Pau

Hi. I've added a news entry in the libre-mesh page to endorse the WBMv7: http://libre-mesh.org/projects/libre-mesh/news Who is interested on going there? Do you have funding? Any idea about where can we find funding to bring some of you there? Cheers -- ./p4u

10 years, 11 months

libremap: wireless plugin?

by Pau

Hi. I've added the libre-map agent to Wibed [1] and now some nodes appear to the libremap.net web interface (in Barcelona). However the wireless plugin is not available, at least in the libremap-agent I'm using [2]. I wonder if this plugin exists and if not which are the plans to implement it. That would be a key point for wibed! So let me know if I can do something. Cheers. [1] http://wiki.confine-project/wibed:start [2] https://github.com/libremap/libremap-agent-openwrt -- ./p4u

10 years, 11 months

Fwd: Re: [OpenWrt-Devel] is anybody working on supporting Linksys WRT1900ac ?

by Gioacchino Mazzurco

Seems an interesting device, maybe we could receive someone if we ask as Libre-Mesh ? ---------- Forwarded Message ---------- Subject: Re: [OpenWrt-Devel] is anybody working on supporting Linksys WRT1900ac ? Date: Thursday 16 January 2014, 10:37:12 From: Peter Lawler <openwrt-devel(a)bleeter.id.au> To: openwrt-devel(a)lists.openwrt.org On 16/01/14 10:06, Peter Lawler wrote: > Oh, bad me for replying to myself... but from the press release page: > > http://www.linksys.com/en-us/press/releases/2014-01-06_Linksys_wrt_revoluti… > > Even worse, replying to my own reply Further down that page is commentary about OpenWRT, DDWRT etc. It also mentions they're planning to release devboards to developers. It also gives a name, email address and phone number for a contact about the product. I'm not in the same TZ as the contact, by ~15 hours. Maybe someone on this list who is a little closer could call up and ask what's what ;) Pete. _______________________________________________ openwrt-devel mailing list openwrt-devel(a)lists.openwrt.org https://lists.openwrt.org/cgi-bin/mailman/listinfo/openwrt-devel -----------------------------------------

10 years, 11 months

Flashing Ubiquiti Devices

by Ilario Gelmetti

Hi all! I compiled libre-mesh encountering only a small problem: subversion is needed but missing in the dependencies list. I was planning to flash libre-mesh on Ubiquiti PicoStation and Ubiquiti NanoStation. Can I safely flash using libre-mesh/images/bin/openwrt-ar71xx-generic-ubnt-bullet-m-squashfs-sysupgrade.bin and openwrt-ar71xx-generic-ubnt-nano-m-squashfs-sysupgrade.bin or some configuration is needed before compilation or after flashing? Thanks and bye, Ilario, Ninux Verona. -- Ilario Gelmetti iochesonome(a)gmail.com ilario.gelmetti(a)sns.it

10 years, 11 months

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lime-dev January 2014