linux-kernel - Re: [PATCH 4.9 27/75] net: igmp: Use correct source address on IGMPv3 reports

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Date:   Tue, 16 Jan 2018 10:18:13 +0100
From:   Sebastian Gottschall <s.gottschall@...wrt.com>
To:     Kevin Cernekee <cernekee@...omium.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, stable <stable@...r.kernel.org>,
        Andrew Lunn <andrew@...n.ch>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 4.9 27/75] net: igmp: Use correct source address on IGMPv3
 reports


> According to my understanding of igmpv3_newpack(), the destination
> address should always be IGMPV3_ALL_MCR = 224.0.0.22.  That is what I
> see in my testing.
>
> However, your packet trace says 239.35.100.8.  I don't know how the
> code that we touched would be generating an IGMPv2 packet with that
> destination address.
easy answer from wikipedia. 224.0.x.x is not the only multicast block

224.0.0.0 to 224.0.0.255 Local subnetwork
224.0.1.0 to 224.0.1.255 Internetwork control
224.0.2.0 to 224.0.255.255 AD-HOC block 1
224.3.0.0 to 224.4.255.255 AD-HOC block 2
232.0.0.0 to 232.255.255.255 Source-specific multicas
233.0.0.0 to 233.251.255.255 GLOP addressing
233.252.0.0 to 233.255.255.255 AD-HOC block 3
234.0.0.0 to 234.255.255.255 Unicast-prefix-based
239.0.0.0 to 239.255.255.255 Administratively scoped


> Would it be possible to get a stack trace for the case where the
> source address is being cleared to 0.0.0.0 in your configuration?
you mean something like dumpstack and watching the flood comes over me?


-- 
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Sebastian Gottschall / CTO

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