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Date: Sat, 14 Aug 2010 16:59:13 +0200 From: Marek Lindner <lindner_marek@...oo.de> To: Vasiliy Kulikov <segooon@...il.com>, Linus Lüssing <linus.luessing@....de> Cc: "Greg Kroah-Hartman" <gregkh@...e.de>, Andrew Lunn <andrew@...n.ch>, Sven Eckelmann <sven.eckelmann@....de>, Simon Wunderlich <siwu@....tu-chemnitz.de>, devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org Subject: Re: batman-adv: design suggestions On Friday 13 August 2010 20:18:33 Vasiliy Kulikov wrote: > d) Why do you send icmp TTL exceeded for the icmp itself? E.g. in case > of loop or/and small default TTL you'll probably get a storm of icmps. > Exactly in this case IP silently drops TTL exceeded icmps ;) These layer2 icmp packets are not ordinary icmp packets. We needed to provide a mechanism to make the network topology visible to debug tools like ping or traceroute which normally "see" no more than one hop as they operate on layer3. Hence, batman-adv does not send an icmp packet for each payload TTL exceeded but for traceroute only. I recommend reviewing the traceroute code to understand how this is supposed to work: http://www.open-mesh.org/browser/trunk/batctl/traceroute.c I'd be interested to learn about a problematic scenario in which this mechanism breaks. Regards, Marek -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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