netdev - Re: Question on DSA switches, IGMP forwarding and switchdev

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Date:   Sat, 20 Jun 2020 00:36:06 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Jason Cobham <jcobham@...stertangent.com>
Cc:     Daniel Mack <daniel@...que.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Ido Schimmel <idosch@...sch.org>,
        Jiri Pirko <jiri@...nulli.us>,
        Ivan Vecera <ivecera@...hat.com>,
        Florian Fainelli <f.fainelli@...il.com>
Subject: Re: Question on DSA switches, IGMP forwarding and switchdev

> 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