Re: Question on DSA switches, IGMP forwarding and switchdev

[Andrew Lunn <andrew@lunn.ch>]

> I've run into the same issue. To resolve it,  In my case, in the same file, I've had to send all IGMP control traffic to the CPU:
> 	skb->offload_fwd_mark = 1;
> 	switch (ih->type) {
> 		case IGMP_HOST_MEMBERSHIP_REPORT:
> 		case IGMPV2_HOST_MEMBERSHIP_REPORT:
> 		case IGMPV3_HOST_MEMBERSHIP_REPORT:
> 		case IGMP_HOST_MEMBERSHIP_QUERY:
> 		case IGMP_HOST_LEAVE_MESSAGE:
> 			skb->offload_fwd_mark = 0;
> 		break;
> 	}
> 
> I'd be interested if there is a better way.

It might depend on the switch generation, but i think some switches
indicate the sort of packet in the DSA header. For 6390, Octet 3 of
the header, bits 3-5 contains a code.

0=BDPU
1=Frame2Reg
2=IGMP/MLD
3=Policy
4=ARP Mirror
5=Policy Mirror

We can look at these bits and not set skb->offload_fwd_mark depending
on its value.

The 6352 family has the same bits. 6161 has a few less bits, but does
have IGMP/MLD. I don't know about the 6085. Do you have the datasheet?

     Andrew