netdev - Re: [PATCH net-next v2] net: pppoe: implement GRO support

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Message-ID: <0861d960-d1e7-4b51-b320-c2e033b49f12@nbd.name>
Date: Tue, 22 Jul 2025 10:56:10 +0200
From: Felix Fietkau <nbd@....name>
To: Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
 Michal Ostrowski <mostrows@...thlink.net>,
 Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>
Cc: linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v2] net: pppoe: implement GRO support

On 22.07.25 10:36, Paolo Abeni wrote:
> On 7/16/25 10:14 AM, Felix Fietkau wrote:
>> +static struct sk_buff *pppoe_gro_receive(struct list_head *head,
>> +					 struct sk_buff *skb)
>> +{
>> +	const struct packet_offload *ptype;
>> +	unsigned int hlen, off_pppoe;
>> +	struct sk_buff *pp = NULL;
>> +	struct pppoe_hdr *phdr;
>> +	struct sk_buff *p;
>> +	__be16 type;
>> +	int flush = 1;
> 
> Minor nit: please respect the reverse christmas tree order above

Will do

>> +	off_pppoe = skb_gro_offset(skb);
>> +	hlen = off_pppoe + sizeof(*phdr) + 2;
>> +	phdr = skb_gro_header(skb, hlen, off_pppoe);
>> +	if (unlikely(!phdr))
>> +		goto out;
>> +
>> +	/* ignore packets with padding or invalid length */
>> +	if (skb_gro_len(skb) != be16_to_cpu(phdr->length) + hlen - 2)
>> +		goto out;
>> +
>> +	NAPI_GRO_CB(skb)->network_offsets[NAPI_GRO_CB(skb)->encap_mark] = hlen;
>> +
>> +	type = pppoe_hdr_proto(phdr);
>> +	if (!type)
>> +		goto out;
>> +
>> +	ptype = gro_find_receive_by_type(type);
>> +	if (!ptype)
>> +		goto out;
>> +
>> +	flush = 0;
>> +
>> +	list_for_each_entry(p, head, list) {
>> +		struct pppoe_hdr *phdr2;
>> +
>> +		if (!NAPI_GRO_CB(p)->same_flow)
>> +			continue;
>> +
>> +		phdr2 = (struct pppoe_hdr *)(p->data + off_pppoe);
>> +		if (compare_pppoe_header(phdr, phdr2))
>> +			NAPI_GRO_CB(p)->same_flow = 0;
>> +	}
>> +
>> +	skb_gro_pull(skb, sizeof(*phdr) + 2);
>> +	skb_gro_postpull_rcsum(skb, phdr, sizeof(*phdr) + 2);
>> +
>> +	pp = ptype->callbacks.gro_receive(head, skb);
> 
> Here you can use INDIRECT_CALL_INET()

I did that in the initial version, but then I got reports of build 
failures with the patch:

ERROR: modpost: "inet_gro_receive" [drivers/net/ppp/pppoe.ko] undefined!
ERROR: modpost: "inet_gro_complete" [drivers/net/ppp/pppoe.ko] undefined!

Should I leave it out, or export inet_gro_receive/complete?
>> +
>> +out:
>> +	skb_gro_flush_final(skb, pp, flush);
>> +
>> +	return pp;
>> +}
>> +
>> +static int pppoe_gro_complete(struct sk_buff *skb, int nhoff)
>> +{
>> +	struct pppoe_hdr *phdr = (struct pppoe_hdr *)(skb->data + nhoff);
>> +	__be16 type = pppoe_hdr_proto(phdr);
>> +	struct packet_offload *ptype;
>> +	int err = -ENOENT;
>> +
>> +	ptype = gro_find_complete_by_type(type);
>> +	if (ptype)
>> +		err = ptype->callbacks.gro_complete(skb, nhoff +
>> +						    sizeof(*phdr) + 2);
> 
> Possibly even here but it's less relevant.
> 
>> +
>> +	return err;
>> +}
>> +
>> +static struct packet_offload pppoe_packet_offload __read_mostly = {
>> +	.type = cpu_to_be16(ETH_P_PPP_SES),
>> +	.priority = 10,
> 
> The priority value should be IMHO greater then the exiting ones to avoid
> possible regressions on other protocols. i.e. 20 should do.
I'll fix it in v3.

Thanks,

- Felix