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SubjectRe: [PATCH 4.9 27/75] net: igmp: Use correct source address on IGMPv3 reports
Am 16.01.2018 um 05:32 schrieb Kevin Cernekee:
> On Mon, Jan 15, 2018 at 8:26 PM, Sebastian Gottschall
> <> wrote:
>> havent check the source addresses right now. i basicly discovered that this
>> patch breaks the igmp routing and all traffic stops
>> this here is from a working system with the reverted patch. if you really
>> need that i break it again using the patch you need to wait a little bit
>> 05:14:22.697962 IP > igmp v2 report
> The patch should only affect IGMPv3 behavior. I did not intend to
> change IGMPv2 behavior. If it does, that might be a bug.
it does change the behaviour indeed. i dont know the reason. but i while
discovering the issue on 4.14 last week and newly on 4.9 this week while
(my latest firmware i builded was from 30. december and worked) i got
tracked it down to this small patch and it immediatly worked after
reverting it
> Is it possible that the kernel is using a source IP of, but
> another host does not recognize it because it does not comply with RFC
> 3376?
this is possible yes, but i cannot look into the "deutsche telekom" host
> Before/after packet traces would be the best way to see if the kernel
> change is causing it to violate the standard.
let me just take a look into our patch
+ for_ifa(in_dev) {
+ if (inet_ifa_match(fl4->saddr, ifa))
+ return fl4->saddr;
+ } endfor_ifa(in_dev);
this looks like you're checking if the source address matches to a local
interface, if not you return instead of the source address

(,    Iif: ppp0       Oifs: briptv

our first source address here is from a remote network.
so your patch also will change the behaviour since the source address
will get ignored

Mit freundlichen Grüssen / Regards

Sebastian Gottschall / CTO

NewMedia-NET GmbH - DD-WRT
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