From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stas Sergeev Subject: Re: Q: bad routing table cache entries Date: Tue, 12 Jan 2016 19:42:41 +0300 Message-ID: <56952D01.6070204@list.ru> References: <5682665A.7090102@list.ru> <56951D1D.5080602@stressinduktion.org> <56952147.80201@stressinduktion.org> <569523C0.5040504@list.ru> <56952593.8040409@stressinduktion.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: netdev To: Hannes Frederic Sowa Return-path: Received: from smtp1.mail.ru ([94.100.179.111]:38686 "EHLO smtp1.mail.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752185AbcALQmr (ORCPT ); Tue, 12 Jan 2016 11:42:47 -0500 In-Reply-To: <56952593.8040409@stressinduktion.org> Sender: netdev-owner@vger.kernel.org List-ID: 12.01.2016 19:10, Hannes Frederic Sowa =D0=BF=D0=B8=D1=88=D0=B5=D1=82: > On 12.01.2016 17:03, Stas Sergeev wrote: >> 12.01.2016 18:52, Hannes Frederic Sowa =D0=BF=D0=B8=D1=88=D0=B5=D1=82= : >>> On 12.01.2016 16:34, Hannes Frederic Sowa wrote: >>>> On 29.12.2015 11:54, Stas Sergeev wrote: >>>>> Hello. >>>>> >>>>> I was hitting a strange problem when some internet hosts >>>>> suddenly stops responding until I reboot. ping to these >>>>> host gives "Destination Host Unreachable". After the >>>>> initial confusion, I've finally got to >>>>> ip route get >>>>> and got something quite strange. >>>>> >>>>> >>>>> Example for GOOD address (the one that I can ping): >>>>> >>>>> ip route get 91.189.89.237 >>>>> 91.189.89.237 via 192.168.8.1 dev eth0 src 192.168.10.202 >>>>> cache >>>>> >>>>> >>>>> Example for BAD address (the one that stopped responding): >>>>> >>>>> ip route get 91.189.89.238 >>>>> 91.189.89.238 via 192.168.0.1 dev eth0 src 192.168.10.202 >>>>> cache >>>> >>>> I tried to understand this thread and now wonder why this redirect= route >>>> isn't there always. Can you please summarize again why this should= n't >>>> happen? It looks totally fine to me from the configuration of your >>>> router and the subnet masks. >>> >>> Just an addendum: >>> >>> In IPv6 a redirect is seen as a notification telling hosts, this ne= w address is on the same link as you. I think this semantic is the same= for IPv4, so we are informing you that in essence you are >>> getting a /32 route installed to your new interface and can do link= layer resolving of the new host. >>> >>> I do think this is valid and fine. >> You can't call "valid and fine" something that doesn't >> work, at first place. Why and where does it fail, was the >> subject of this thread. >=20 > In terms of the shared media specification it is valid and fine. Good luck sending users to RFC without giving any explanations. :) Well, yes, an interesting reading, but: https://tools.ietf.org/html/rfc1812 --- Routers MUST NOT generate a Redirect Message unless all the followin= g conditions are met: o The packet is being forwarded out the same physical interface that it was received from, o The IP source address in the packet is on the same Logical IP (sub)network as the next-hop IP address, and o The packet does not contain an IP source route option. The source address used in the ICMP Redirect MUST belong to the same logical (sub)net as the destination address. --- Could you please explain why the above does not apply? > You can also disable shared_media on the client and it won't accept s= uch redirects anymore. Only "such" redirects, or any redirects? >> If you think router did the right thing, then please explain >> the breakage from that point of view. > Hope it makes sense. No, because it still doesn't work for me. What should I do to get such redirects to work? What should I do to at least list them? Even if this is with accordance to some RFC (which it seems not, though= ), this doesn't help me a tiny bit, unless it also works. :)