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I found that linux kernel had had a bug in the implementation of IGMP
membership report packet generation. the RFC documents for IGMP version 2
and 3 says that you must ignore the reports with a source ip address that
you can't identify as belonging to a network assigned to the interface on
which the packet was received. and the networking OS in the ToR switch,
Force10 OS 9 does ignore it.

I've also figured out a patch has been made for this bug in Linus's Github.
and there was a mark on Github that reads "v4.16-rc1". (
https://github.com/torvalds/linux/commit/a46182b00290839fa3fa159d54fd3237bd8669f0
 )

I honestly have no idea how Ubuntu LTS team works with regard to this kind
of patches from the fresh new upstream version of linux kernel. hope you
guys will easily fix it for people like me who has no experience at
building and distributing custom built kernels over a few servers.

Test environment:
I used two ToR switches and one linux machine for this test.
I only used 2 ethernet ports on the linux machine.
There was a recent version of Ubuntu with HWE kernel. I'm not sure if
no-HWE one would be the same case - the version of linux-generic-hwe-16.04
was 4.13.0.32.52 -
To test networking router stuff, I used the quagga from Cumulus Routing on
the Host 3.3.2 (
https://cumulusnetworks.com/products/cumulus-routing-on-the-host/#roh-download-section
 )

What I did and saw in my case:
1. set a network interface (A) so it gets an IPv4 address, but also in vain
issue "ip link set ${if_name} multicast off"
2. assign an IPv4 address to another network interface (B), but in this
case with a 31-bit-long subnet mask length.
3. install quagga from cumulus, launch zebra and pimd, issue "ip pim sm" in
the interface configuration mode for the interface (B) with a 31-bit-long
subnet mask length
4. I checked that the source IP address part of the IGMP membership report
packets from the linux machine is the address I assigned to the network
interface (A) with 27-bit-long subnet mask -using dumpcap and tshark-, and
that the PIM service on the switch ignored the Reports printing debugging
messages including : "Invalid sender address"

 affects ubuntu

Regards,
Gunwoo
-- 
You can find my PGP public key here: https://google.com/+DewrKim/about

** Affects: linux (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: bot-comment
-- 
incorrect source address in IGMP Membership Report messages
https://bugs.launchpad.net/bugs/1749058
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