Re: [PATCH] netfilter: nft_paylaod: add base type NFT_PAYLOAD_LL_HEADER_NO_TAG

[wenxu <wenxu@ucloud.cn>]

On 6/18/2019 6:42 AM, Florian Westphal wrote:
> Pablo Neira Ayuso <pablo@netfilter.org> wrote:
>>> Subject: Change bridge l3 dependency to meta protocol
>>>
>>> This examines skb->protocol instead of ethernet header type, which
>>> might be different when vlan is involved.
>>>  
>>> +	if (ctx->pctx.family == NFPROTO_BRIDGE && desc == &proto_eth) {
>>> +		if (expr->payload.desc == &proto_ip ||
>>> +		    expr->payload.desc == &proto_ip6)
>>> +			desc = &proto_metaeth;
>>> +	}i
>> Is this sufficient to restrict the matching? Is this still buggy from
>> ingress?
> This is what netdev family uses as well (skb->protocol i mean).
> I'm not sure it will work for output however (haven't checked).
>
>> I wonder if an explicit NFT_PAYLOAD_CHECK_VLAN flag would be useful in
>> the kernel, if so we could rename NFTA_PAYLOAD_CSUM_FLAGS to
>> NFTA_PAYLOAD_FLAGS and place it there. Just an idea.
>
> Another unresolved issue is presence of multiple vlan tags, so we might
> have to add yet another meta key to retrieve the l3 protocol in use

Maybe add a l3proto meta key can handle the multiple vlan tags case with the l3proto dependency.  It

should travese all the vlan tags and find the real l3 proto.


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