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

From: Sebastian Gottschall
Date: Tue Jan 16 2018 - 04:18:30 EST



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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