Re: [lwip-users] IPv6 porting, need help in netif->mld _mac_filter

[Ivan Delamer]

Hi,

Like Zach said, you can do with mld_mac_filter set to NULL and making 
sure your MAC implementation lets those packets through. Link-local 
all-nodes address is accepted by default so you can receive those RA 
packets.

The easiest way to do it is to set up your MAC to accept all multicast 
packets. In most networks this works well.

In really large networks with lots of multicast packets, it can become 
inefficient as TCP/IP stack needs to process and drop lots of packets. 
In that case, you can implement mld_mac_filter to tell your MAC which 
packets to let through and which ones to ignore.

What I do is something in between: I know in advance which Multicast 
addresses my application uses and I hard code into the MAC code which 
ones to let through. Implementing mld_mac_filter would be better but 
this works for me.

Cheers
IVan


> Date: Fri, 10 Jan 2014 15:59:47 +0000
> From: Zach Smith <address@hidden>
> To: Mailing list for lwIP users <address@hidden>
> Subject: Re: [lwip-users] IPv6 porting, need help in
>         netif->mld_mac_filter
> Message-ID:
>         <address@hidden>
>
> Content-Type: text/plain; charset="us-ascii"
>
> In my IP6 implementation I did not do anything with the
> mld_mac_filter parameter. It is just set to null in netif_add. FF02::1
> is the all nodes multicast group so I think by default you are already
> joined to that group.
>
> The only thing I can think of that you haven't mentioned is to make
> sure your MAC is set up to accept multicast packets. It may be set to
> receive broadcast already but IP6 won't work if it is not set to
> receive multicast.
>
> -Zach
>
> From: address@hidden
> [mailto:address@hidden On
> Behalf Of address@hidden
> Sent: Thursday, January 09, 2014 10:05 PM
> To: address@hidden
> Subject: [lwip-users] IPv6 porting, need help in netif->mld_mac_filter
>
> Hi,
>
> I am new to LWIP IPv6 implementation.
> I am trying to port it for my device, I have set below netif param
> and #define to respective values
>
> #define LWIP_IPV6                             1
> #define LWIP_IPV6_DHCP6             1
> #define LWIP_ICMP6                          1
> #define LWIP_IPV6_AUTOCONFIG              1
> #define LWIP_IPV6_NUM_ADDRESSES     6
>
> netif->ip6_autoconfig_enabled = 1;
> netif->output_ip6 = ethip6_output;
>
> With this setting I could see LWIP is sending
>
> a>     "Multicast Listner Report"
>
> b>    Neighbour solicitation
>
> c>     Router Solicitation (to ff02::2)
>
> Also I can see my router is sending me Router advertisement (to
> ff02::1) which I am not able to receive. I feel this is because I
> haven't set below parameter in netif
> netif->mld_mac_filter = ?????;
>
> I am not sure what this function should be, As I know I have to join
> this multicast group to receive the advertisement packet.
>
> Can someone help me in what this function should point to and is some
> example already  available?
>
> Thanks and  Regards,
> Manoj
>
>
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