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?


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


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