Re: [PATCH net-next v7 1/2] net: pppoe: implement GRO/GSO support

[Paolo Abeni <pabeni@redhat.com>]

On 4/28/26 8:47 AM, Qingfang Deng wrote:
> diff --git a/drivers/net/ppp/pppoe.c b/drivers/net/ppp/pppoe.c
> index bdd61c504a1c..363204e0c49a 100644
> --- a/drivers/net/ppp/pppoe.c
> +++ b/drivers/net/ppp/pppoe.c
> @@ -77,6 +77,7 @@
>  #include <net/net_namespace.h>
>  #include <net/netns/generic.h>
>  #include <net/sock.h>
> +#include <net/gro.h>
>  
>  #include <linux/uaccess.h>
>  
> @@ -409,7 +410,7 @@ static int pppoe_rcv(struct sk_buff *skb, struct net_device *dev,
>  	if (ppp_skb_is_compressed_proto(skb))
>  		goto drop;
>  
> -	if (pskb_trim_rcsum(skb, len))
> +	if (!skb_is_gso(skb) && pskb_trim_rcsum(skb, len))
>  		goto drop;
>  
>  	ph = pppoe_hdr(skb);
> @@ -1103,6 +1104,164 @@ static struct pernet_operations pppoe_net_ops = {
>  	.size = sizeof(struct pppoe_net),
>  };
>  
> +static u16
> +compare_pppoe_header(const struct pppoe_hdr *phdr,
> +		     const struct pppoe_hdr *phdr2)
> +{
> +	__be16 proto = *(const __be16 *)(phdr + 1);
> +	__be16 proto2 = *(const __be16 *)(phdr2 + 1);
> +
> +	return (__force u16)((phdr->sid ^ phdr2->sid) | (proto ^ proto2));
> +}
> +
> +static __be16 pppoe_hdr_proto(const struct pppoe_hdr *phdr)
> +{
> +	__be16 proto = *(const __be16 *)(phdr + 1);
> +
> +	switch (proto) {
> +	case cpu_to_be16(PPP_IP):
> +		return cpu_to_be16(ETH_P_IP);
> +#if IS_ENABLED(CONFIG_IPV6)
> +	case cpu_to_be16(PPP_IPV6):
> +		return cpu_to_be16(ETH_P_IPV6);
> +#endif
> +	default:
> +		return 0;
> +	}
> +}
> +
> +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;
> +	const struct pppoe_hdr *phdr;
> +	struct sk_buff *pp = NULL;
> +	struct sk_buff *p;
> +	int flush = 1;
> +	__be16 type;
> +
> +	off_pppoe = skb_gro_offset(skb);
> +	hlen = off_pppoe + PPPOE_SES_HLEN;
> +	phdr = skb_gro_header(skb, hlen, off_pppoe);
> +	if (unlikely(!phdr))
> +		goto out;
> +
> +	/* filter for session packets (type:1, ver:1, code:0) */
> +	if (*(const __be16 *)phdr != cpu_to_be16(0x1100))
> +		goto out;
> +
> +	/* ignore packets with padding or invalid length */
> +	if (skb_gro_len(skb) != be16_to_cpu(phdr->length) + sizeof(*phdr))
> +		goto out;
> +
> +	type = pppoe_hdr_proto(phdr);
> +	ptype = gro_find_receive_by_type(type);
> +	if (!ptype)
> +		goto out;
> +
> +	flush = 0;
> +
> +	list_for_each_entry(p, head, list) {
> +		const struct pppoe_hdr *phdr2;
> +
> +		if (!NAPI_GRO_CB(p)->same_flow)
> +			continue;
> +
> +		phdr2 = (const struct pppoe_hdr *)(p->data + off_pppoe);
> +		if (compare_pppoe_header(phdr, phdr2))
> +			NAPI_GRO_CB(p)->same_flow = 0;
> +	}
> +
> +	skb_gro_pull(skb, PPPOE_SES_HLEN);
> +	skb_gro_postpull_rcsum(skb, phdr, PPPOE_SES_HLEN);
> +
> +	pp = indirect_call_gro_receive_inet(ptype->callbacks.gro_receive,
> +					    ipv6_gro_receive, inet_gro_receive,
> +					    head, skb);
> +
> +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;
> +	unsigned int len;
> +
> +	ptype = gro_find_complete_by_type(type);
> +	if (!ptype)
> +		return -ENOENT;
> +
> +	len = skb->len - (nhoff + sizeof(*phdr));
> +	len = min(len, 0xFFFFU);
> +	phdr->length = cpu_to_be16(len);

Whoops, I wrongly replied to v6, but comments still apply here:

https://lore.kernel.org/netdev/9d7f1bbc-155d-4c18-bcf7-732ebe4cbf67@redhat.com/T/#m6c92ba4367355abf1bdb001f102c4847853ac4f3


/P