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Message-ID: <68be885c-f3ea-48aa-91c9-673f9c67fe28@gmail.com>
Date: Thu, 14 Aug 2025 16:30:16 +0200
From: Richard Gobert <richardbgobert@...il.com>
To: Felix Fietkau <nbd@....name>, 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>, Paolo Abeni <pabeni@...hat.com>,
David Ahern <dsahern@...nel.org>, Simon Horman <horms@...nel.org>
Cc: linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v3] net: pppoe: implement GRO/GSO support
Felix Fietkau wrote:
> Only handles packets where the pppoe header length field matches the exact
> packet length. Significantly improves rx throughput.
>
> When running NAT traffic through a MediaTek MT7621 devices from a host
> behind PPPoE to a host directly connected via ethernet, the TCP throughput
> that the device is able to handle improves from ~130 Mbit/s to ~630 Mbit/s,
> using fraglist GRO.
>
> Signed-off-by: Felix Fietkau <nbd@....name>
> ---
> v2: fix compile error
> v3:
> - increase priority value
> - implement GSO support
> - use INDIRECT_CALL_INET
> - update pppoe length field
> - remove unnecessary network_offsets update
>
> drivers/net/ppp/pppoe.c | 160 +++++++++++++++++++++++++++++++++++++++-
> net/ipv4/af_inet.c | 2 +
> net/ipv6/ip6_offload.c | 2 +
> 3 files changed, 163 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/ppp/pppoe.c b/drivers/net/ppp/pppoe.c
> index 410effa42ade..a8d8eb870bce 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>
>
> @@ -435,7 +436,7 @@ static int pppoe_rcv(struct sk_buff *skb, struct net_device *dev,
> if (skb->len < len)
> goto drop;
>
> - if (pskb_trim_rcsum(skb, len))
> + if (!skb_is_gso(skb) && pskb_trim_rcsum(skb, len))
> goto drop;
>
> ph = pppoe_hdr(skb);
> @@ -1173,6 +1174,161 @@ static struct pernet_operations pppoe_net_ops = {
> .size = sizeof(struct pppoe_net),
> };
>
> +static u16
> +compare_pppoe_header(struct pppoe_hdr *phdr, struct pppoe_hdr *phdr2)
> +{
> + return (__force __u16)((phdr->sid ^ phdr2->sid) |
> + (phdr->tag[0].tag_type ^ phdr2->tag[0].tag_type));
> +}
> +
> +static __be16 pppoe_hdr_proto(struct pppoe_hdr *phdr)
> +{
> + switch (phdr->tag[0].tag_type) {
> + case cpu_to_be16(PPP_IP):
> + return cpu_to_be16(ETH_P_IP);
> + case cpu_to_be16(PPP_IPV6):
> + return cpu_to_be16(ETH_P_IPV6);
> + 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;
> + struct sk_buff *pp = NULL;
> + struct pppoe_hdr *phdr;
> + struct sk_buff *p;
> + int flush = 1;
> + __be16 type;
> +
> + off_pppoe = skb_gro_offset(skb);
> + hlen = off_pppoe + sizeof(*phdr);
> + phdr = skb_gro_header(skb, hlen + 2, 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)
> + goto out;
> +
> + 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 = 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;
> + int len, err;
> +
> + ptype = gro_find_complete_by_type(type);
> + if (!ptype)
> + return -ENOENT;
> +
> + err = INDIRECT_CALL_INET(ptype->callbacks.gro_complete,
> + ipv6_gro_complete, inet_gro_complete,
> + skb, nhoff + sizeof(*phdr) + 2);
> + if (err)
> + return err;
> +
> + len = skb->len - (nhoff + sizeof(*phdr));
> + phdr->length = cpu_to_be16(len);
> +
> + return 0;
> +}
> +
> +static struct sk_buff *pppoe_gso_segment(struct sk_buff *skb,
> + netdev_features_t features)
> +{
I don't think this will be called for PPPoE over GRE packets,
since gre_gso_segment skips everything up to the network header.
> + unsigned int pppoe_hlen = sizeof(struct pppoe_hdr) + 2;
> + struct sk_buff *segs = ERR_PTR(-EINVAL);
> + u16 mac_offset = skb->mac_header;
> + struct packet_offload *ptype;
> + u16 mac_len = skb->mac_len;
> + struct pppoe_hdr *phdr;
> + __be16 orig_type, type;
> + int len, nhoff;
> +
> + skb_reset_network_header(skb);
> + nhoff = skb_network_header(skb) - skb_mac_header(skb);
> +
> + if (unlikely(!pskb_may_pull(skb, pppoe_hlen)))
> + goto out;
> +
> + phdr = (struct pppoe_hdr *)skb_network_header(skb);
> + type = pppoe_hdr_proto(phdr);
> + ptype = gro_find_complete_by_type(type);
> + if (!ptype)
> + goto out;
> +
> + orig_type = skb->protocol;
> + __skb_pull(skb, pppoe_hlen);
> + segs = ptype->callbacks.gso_segment(skb, features);
> + if (IS_ERR_OR_NULL(segs)) {
> + skb_gso_error_unwind(skb, orig_type, pppoe_hlen, mac_offset,
> + mac_len);
> + goto out;
> + }
> +
> + skb = segs;
> + do {
> + phdr = (struct pppoe_hdr *)(skb_mac_header(skb) + nhoff);
> + len = skb->len - (nhoff + sizeof(*phdr));
> + phdr->length = cpu_to_be16(len);
> + skb->network_header = (u8 *)phdr - skb->head;
> + skb->protocol = orig_type;
> + skb_reset_mac_len(skb);
> + } while ((skb = skb->next));
> +
> +out:
> + return segs;
> +}
> +
> +static struct packet_offload pppoe_packet_offload __read_mostly = {
> + .type = cpu_to_be16(ETH_P_PPP_SES),
> + .priority = 20,
> + .callbacks = {
> + .gro_receive = pppoe_gro_receive,
> + .gro_complete = pppoe_gro_complete,
> + .gso_segment = pppoe_gso_segment,
> + },
> +};
> +
> static int __init pppoe_init(void)
> {
> int err;
> @@ -1189,6 +1345,7 @@ static int __init pppoe_init(void)
> if (err)
> goto out_unregister_pppoe_proto;
>
> + dev_add_offload(&pppoe_packet_offload);
> dev_add_pack(&pppoes_ptype);
> dev_add_pack(&pppoed_ptype);
> register_netdevice_notifier(&pppoe_notifier);
> @@ -1208,6 +1365,7 @@ static void __exit pppoe_exit(void)
> unregister_netdevice_notifier(&pppoe_notifier);
> dev_remove_pack(&pppoed_ptype);
> dev_remove_pack(&pppoes_ptype);
> + dev_remove_offload(&pppoe_packet_offload);
> unregister_pppox_proto(PX_PROTO_OE);
> proto_unregister(&pppoe_sk_proto);
> unregister_pernet_device(&pppoe_net_ops);
> diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
> index 76e38092cd8a..0480a6d4f203 100644
> --- a/net/ipv4/af_inet.c
> +++ b/net/ipv4/af_inet.c
> @@ -1533,6 +1533,7 @@ struct sk_buff *inet_gro_receive(struct list_head *head, struct sk_buff *skb)
>
> return pp;
> }
> +EXPORT_INDIRECT_CALLABLE(inet_gro_receive);
>
> static struct sk_buff *ipip_gro_receive(struct list_head *head,
> struct sk_buff *skb)
> @@ -1618,6 +1619,7 @@ int inet_gro_complete(struct sk_buff *skb, int nhoff)
> out:
> return err;
> }
> +EXPORT_INDIRECT_CALLABLE(inet_gro_complete);
>
> static int ipip_gro_complete(struct sk_buff *skb, int nhoff)
> {
> diff --git a/net/ipv6/ip6_offload.c b/net/ipv6/ip6_offload.c
> index fce91183797a..9e3640b018a4 100644
> --- a/net/ipv6/ip6_offload.c
> +++ b/net/ipv6/ip6_offload.c
> @@ -306,6 +306,7 @@ INDIRECT_CALLABLE_SCOPE struct sk_buff *ipv6_gro_receive(struct list_head *head,
>
> return pp;
> }
> +EXPORT_INDIRECT_CALLABLE(ipv6_gro_receive);
>
> static struct sk_buff *sit_ip6ip6_gro_receive(struct list_head *head,
> struct sk_buff *skb)
> @@ -388,6 +389,7 @@ INDIRECT_CALLABLE_SCOPE int ipv6_gro_complete(struct sk_buff *skb, int nhoff)
> out:
> return err;
> }
> +EXPORT_INDIRECT_CALLABLE(ipv6_gro_complete);
>
> static int sit_gro_complete(struct sk_buff *skb, int nhoff)
> {
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