Hi Urs,

On ti, 2015-05-12 at 09:34 +0000, Urs Ritzmann wrote:
> Hi connman devs,
> 
> We're running connman on a system using PTP (IEEE1588). The problem is that 
> connman is fiddling with the rp_filter settings and activating loose mode 
> routing (value 2) if two or more services are present. We cannot have 
> ip_filter activated because it blocks certain PTP frames. According to this I 
> have two questions:
> 
> 
> 1) I currently do not understand the following: Rp_filter is just a 
> recommended security practice (RFC3704). But the connman commit message 
> sounds like rp_filter is needed to ensure proper functionality with two or 
> more interfaces.
> 
> commit cb3e78500a2539a61d73ecb9708a2b06ea1f356d
> Author: Jukka Rissanen 
> <[email protected]<mailto:[email protected]>>
> Date:   Fri Oct 21 11:16:55 2011 +0300
> 
>     service: Activate loose mode routing
> 
>     If more than one service is connected at the same time,
>     then activate loose mode routing by setting the
>     /proc/sys/net/ipv4/conf/all/rp_filter to value 2
>     If the loose mode routing is not activated, then packets
>     are not routed properly if services are connected to same
>     subnet.
> 
>     The original value of rp_filter is restored when the other
>     services are disconnected and only one service is connected.
> 
>     For details of rp_filter setting, see Linux kernel file
>     Documentation/networking/ip-sysctl.txt
> 
>     Fixes BMC#23606
> 
> What means "not routed properly"? Can we run into any problems when disabling 
> rp_filter but having multiple interfaces/services (e.g. Ethernet and WiFi)? 
> Is the actual reason that connman sets rp_filter because of security or are 
> there any other reasons?

See these two bug reports for details for this change:

https://01.org/jira/browse/CM-360
https://01.org/jira/browse/CM-375


> 
> 2) What is your opinion about a submitting patch which introduces a config 
> option to never change rp_filter settings? Are there good changes to have 
> this integrated in the main sources.
> 
> Thanks,
> Urs
> 
> 

Cheers,
Jukka


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