Re: The SO_BINDTODEVICE was set to the desired interface, but packets are received from all interfaces.

[Ben Greear <greearb@candelatech.com>]

On 05/07/2018 03:19 AM, Damir Mansurov wrote:
>
> Greetings,
>
> After successful call of the setsockopt(SO_BINDTODEVICE) function to set data reception from only one interface, the data is still received from all interfaces.
> Function setsockopt() returns 0 but then recv() receives data from all available network interfaces.
>
> The problem is reproducible on linux kernels 4.14 - 4.16, but it does not on linux kernels 4.4, 4.13.
>
> I have written C-code to reproduce this issue (see attached files b2d_send.c and b2d_recv.c). See below explanation of tested configuration.

Hello,

I am not sure if this is your problem or not, but if you are using VRF, then you need
to call SO_BINDTODEVICE before you do the 'normal' bind() call.

Thanks,
Ben

>
>
>         PC-1                              PC-2
>  -------------------               -------------------
>  | b2d_send        |               | b2d_recv        |
>  |                 |               |                 |
>  |           ------|               |------           |
>  |          | eth0 |---------------| eth0 |          |
>  |           ------|               |------           |
>  |                 |               |                 |
>  |           ------|               |------           |
>  |          | eth1 |---------------| eth1 |          |
>  |           ------|               |------           |
>  |                 |               |                 |
>  -------------------               -------------------
>
> Steps:
> 1. Copy b2d_recv.c to PC-2, compile it ("gcc -o b2d_recv b2d_recv.c") and run "./b2d_recv eth0 23777" to get derived data only from eth0 interface. Port number
> in this example is 23777 only for sample.
>
> 2. Copy b2d_send.c to PC-1, compile it ("gcc -o b2d_send b2d_send.c") and run "./b2d_send ip1 ip2 23777" where ip1 and ip2 are ip addresses of interfaces eth0
> and eth1 of PC-2.
>
> 3. Result:
> - b2d_recv prints out data from eth0 and eth1 on linux kernels from 4.14 up to 4.16.
> - b2d_recv prints out data from only eth0 on linux kernels below 4.14.
>
>
> ******************
> Thanks,
> Damir Mansurov
> dnman@oktetlabs.ru


-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com