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

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

[Qingfang Deng]

From: Felix Fietkau <nbd@nbd.name>

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@nbd.name>
Signed-off-by: Qingfang Deng <qingfang.deng@linux.dev>
---
v7:
 - Use PPPOE_SES_HLEN macro instead of +2 magic number
v6: https://lore.kernel.org/netdev/20260326081127.61229-1-dqfext@gmail.com
 - avoid phdr->length field overflow 
 - restore skb_is_gso() check
 - do not register GRO if INET=n
 - do not check for PPP_IPV6 if IPV6=n
 - tail call gro_complete

 drivers/net/ppp/pppoe.c | 165 +++++++++++++++++++++++++++++++++++++++-
 net/ipv4/af_inet.c      |   2 +
 net/ipv6/ip6_offload.c  |   2 +
 3 files changed, 168 insertions(+), 1 deletion(-)

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);
+
+	return INDIRECT_CALL_INET(ptype->callbacks.gro_complete,
+				  ipv6_gro_complete, inet_gro_complete,
+				  skb, nhoff + PPPOE_SES_HLEN);
+}
+
+static struct sk_buff *pppoe_gso_segment(struct sk_buff *skb,
+					 netdev_features_t features)
+{
+	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_SES_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_SES_HLEN);
+	segs = ptype->callbacks.gso_segment(skb, features);
+	if (IS_ERR_OR_NULL(segs)) {
+		skb_gso_error_unwind(skb, orig_type, PPPOE_SES_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;
@@ -1119,6 +1278,8 @@ static int __init pppoe_init(void)
 	if (err)
 		goto out_unregister_pppoe_proto;
 
+	if (IS_ENABLED(CONFIG_INET))
+		dev_add_offload(&pppoe_packet_offload);
 	dev_add_pack(&pppoes_ptype);
 	dev_add_pack(&pppoed_ptype);
 	register_netdevice_notifier(&pppoe_notifier);
@@ -1138,6 +1299,8 @@ static void __exit pppoe_exit(void)
 	unregister_netdevice_notifier(&pppoe_notifier);
 	dev_remove_pack(&pppoed_ptype);
 	dev_remove_pack(&pppoes_ptype);
+	if (IS_ENABLED(CONFIG_INET))
+		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 0e62032e76b1..cbac072633bb 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1540,6 +1540,7 @@ 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)
@@ -1625,6 +1626,7 @@ 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 d8072ad6b8c4..78f50c93c536 100644
--- a/net/ipv6/ip6_offload.c
+++ b/net/ipv6/ip6_offload.c
@@ -297,6 +297,7 @@ 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)
@@ -359,6 +360,7 @@ 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)
 {
-- 
2.43.0

[PATCH net-next v7 2/2] selftests: net: test PPPoE packets in gro.sh

[Qingfang Deng]

Add PPPoE test-cases to the GRO selftest. Only run a subset of
common_tests to avoid changing the hardcoded L3 offsets everywhere.
Add a new "pppoe_sid" test case to verify that packets with different
PPPoE session IDs are correctly identified as separate flows and not
coalesced.

Signed-off-by: Qingfang Deng <qingfang.deng@linux.dev>
---
v7:
 - Do not run all the tests for PPPoE
 - Add a new test for PPPoE
v6: https://lore.kernel.org/netdev/20260326081127.61229-2-dqfext@gmail.com

 tools/testing/selftests/drivers/net/config |  2 +
 tools/testing/selftests/drivers/net/gro.py | 11 +++
 tools/testing/selftests/net/lib/gro.c      | 99 ++++++++++++++++++----
 3 files changed, 96 insertions(+), 16 deletions(-)

diff --git a/tools/testing/selftests/drivers/net/config b/tools/testing/selftests/drivers/net/config
index fd16994366f4..07e386895b94 100644
--- a/tools/testing/selftests/drivers/net/config
+++ b/tools/testing/selftests/drivers/net/config
@@ -8,5 +8,7 @@ CONFIG_NETCONSOLE=m
 CONFIG_NETCONSOLE_DYNAMIC=y
 CONFIG_NETCONSOLE_EXTENDED_LOG=y
 CONFIG_NETDEVSIM=m
+CONFIG_PPP=y
+CONFIG_PPPOE=y
 CONFIG_VLAN_8021Q=m
 CONFIG_XDP_SOCKETS=y
diff --git a/tools/testing/selftests/drivers/net/gro.py b/tools/testing/selftests/drivers/net/gro.py
index 221f27e57147..ad7c80f7ba96 100755
--- a/tools/testing/selftests/drivers/net/gro.py
+++ b/tools/testing/selftests/drivers/net/gro.py
@@ -313,6 +313,12 @@ def _gro_variants():
         "ip_frag6", "ip_v6ext_same", "ip_v6ext_diff",
     ]
 
+    # Tests specific to PPPoE
+    pppoe_tests = [
+        "data_same", "data_lrg_sml", "data_sml_lrg", "data_lrg_1byte",
+        "data_burst", "pppoe_sid",
+    ]
+
     for mode in ["sw", "hw", "lro"]:
         for protocol in ["ipv4", "ipv6", "ipip", "ip6ip6"]:
             for test_name in common_tests:
@@ -325,6 +331,11 @@ def _gro_variants():
                 for test_name in ipv6_tests:
                     yield mode, protocol, test_name
 
+    for mode in ["sw"]:
+        for protocol in ["pppoev4", "pppoev6"]:
+            for test_name in pppoe_tests:
+                yield mode, protocol, test_name
+
 
 @ksft_variants(_gro_variants())
 def test(cfg, mode, protocol, test_name):
diff --git a/tools/testing/selftests/net/lib/gro.c b/tools/testing/selftests/net/lib/gro.c
index 11b16ae5f0e8..0da55b757bcc 100644
--- a/tools/testing/selftests/net/lib/gro.c
+++ b/tools/testing/selftests/net/lib/gro.c
@@ -67,12 +67,14 @@
 #include <errno.h>
 #include <error.h>
 #include <getopt.h>
+#include <net/ethernet.h>
+#include <net/if.h>
 #include <linux/filter.h>
 #include <linux/if_packet.h>
+#include <linux/if_pppox.h>
 #include <linux/ipv6.h>
 #include <linux/net_tstamp.h>
-#include <net/ethernet.h>
-#include <net/if.h>
+#include <linux/ppp_defs.h>
 #include <netinet/in.h>
 #include <netinet/ip.h>
 #include <netinet/ip6.h>
@@ -134,6 +136,7 @@ static int total_hdr_len = -1;
 static int ethhdr_proto = -1;
 static bool ipip;
 static bool ip6ip6;
+static bool pppoe;
 static uint64_t txtime_ns;
 static int num_flows = 4;
 static bool order_check;
@@ -171,6 +174,22 @@ static void vlog(const char *fmt, ...)
 	}
 }
 
+static void fill_pppoelayer(void *buf, int payload_len, uint16_t sid)
+{
+	struct pppoe_ppp_hdr {
+		struct pppoe_hdr eh;
+		__be16 proto;
+	} *ph = buf;
+
+	payload_len += sizeof(struct tcphdr);
+	ph->eh.type = 1;
+	ph->eh.ver = 1;
+	ph->eh.code = 0;
+	ph->eh.sid = htons(sid);
+	ph->eh.length = htons(payload_len + sizeof(ph->proto));
+	ph->proto = htons(proto == PF_INET ? PPP_IP : PPP_IPV6);
+}
+
 static void setup_sock_filter(int fd)
 {
 	const int dport_off = tcp_offset + offsetof(struct tcphdr, dest);
@@ -412,11 +431,15 @@ static void create_packet(void *buf, int seq_offset, int ack_offset,
 
 	fill_networklayer(buf + inner_ip_off, payload_len, IPPROTO_TCP);
 	if (inner_ip_off > ETH_HLEN) {
-		int encap_proto = (proto == PF_INET) ?
-				  IPPROTO_IPIP : IPPROTO_IPV6;
+		if (pppoe) {
+			fill_pppoelayer(buf + ETH_HLEN, payload_len + ip_hdr_len, 0x1234);
+		} else {
+			int encap_proto = (proto == PF_INET) ?
+					  IPPROTO_IPIP : IPPROTO_IPV6;
 
-		fill_networklayer(buf + ETH_HLEN,
-				  payload_len + ip_hdr_len, encap_proto);
+			fill_networklayer(buf + ETH_HLEN,
+					  payload_len + ip_hdr_len, encap_proto);
+		}
 	}
 
 	fill_datalinklayer(buf);
@@ -526,7 +549,7 @@ static void send_flags(int fd, struct sockaddr_ll *daddr, int psh, int syn,
 static void send_data_pkts(int fd, struct sockaddr_ll *daddr,
 			   int payload_len1, int payload_len2)
 {
-	static char buf[ETH_HLEN + IP_MAXPACKET];
+	static char buf[MAX_HDR_LEN + IP_MAXPACKET];
 
 	create_packet(buf, 0, 0, payload_len1, 0);
 	write_packet(fd, buf, total_hdr_len + payload_len1, daddr);
@@ -1071,6 +1094,20 @@ static void send_fragment6(int fd, struct sockaddr_ll *daddr)
 	write_packet(fd, buf, bufpkt_len, daddr);
 }
 
+static void send_changed_pppoe_sid(int fd, struct sockaddr_ll *daddr)
+{
+	static char buf[MAX_HDR_LEN + PAYLOAD_LEN];
+	int pkt_size = total_hdr_len + PAYLOAD_LEN;
+	struct pppoe_hdr *hdr = (struct pppoe_hdr *)(buf + ETH_HLEN);
+
+	create_packet(buf, 0, 0, PAYLOAD_LEN, 0);
+	write_packet(fd, buf, pkt_size, daddr);
+
+	create_packet(buf, PAYLOAD_LEN, 0, PAYLOAD_LEN, 0);
+	hdr->sid = htons(0x4321);
+	write_packet(fd, buf, pkt_size, daddr);
+}
+
 static void bind_packetsocket(int fd)
 {
 	struct sockaddr_ll daddr = {};
@@ -1121,9 +1158,10 @@ static void recv_error(int fd, int rcv_errno)
 static void check_recv_pkts(int fd, int *correct_payload,
 			    int correct_num_pkts)
 {
-	static char buffer[IP_MAXPACKET + ETH_HLEN + 1];
-	struct iphdr *iph = (struct iphdr *)(buffer + ETH_HLEN);
-	struct ipv6hdr *ip6h = (struct ipv6hdr *)(buffer + ETH_HLEN);
+	static char buffer[IP_MAXPACKET + MAX_HDR_LEN + 1];
+	int nhoff = ETH_HLEN + (pppoe ? PPPOE_SES_HLEN : 0);
+	struct iphdr *iph = (struct iphdr *)(buffer + nhoff);
+	struct ipv6hdr *ip6h = (struct ipv6hdr *)(buffer + nhoff);
 	struct tcphdr *tcph;
 	bool bad_packet = false;
 	int tcp_ext_len = 0;
@@ -1140,7 +1178,7 @@ static void check_recv_pkts(int fd, int *correct_payload,
 
 	while (1) {
 		ip_ext_len = 0;
-		pkt_size = recv(fd, buffer, IP_MAXPACKET + ETH_HLEN + 1, 0);
+		pkt_size = recv(fd, buffer, sizeof(buffer), 0);
 		if (pkt_size < 0)
 			recv_error(fd, errno);
 
@@ -1183,9 +1221,10 @@ static void check_recv_pkts(int fd, int *correct_payload,
 
 static void check_capacity_pkts(int fd)
 {
-	static char buffer[IP_MAXPACKET + ETH_HLEN + 1];
-	struct iphdr *iph = (struct iphdr *)(buffer + ETH_HLEN);
-	struct ipv6hdr *ip6h = (struct ipv6hdr *)(buffer + ETH_HLEN);
+	static char buffer[IP_MAXPACKET + MAX_HDR_LEN + 1];
+	int nhoff = ETH_HLEN + (pppoe ? PPPOE_SES_HLEN : 0);
+	struct iphdr *iph = (struct iphdr *)(buffer + nhoff);
+	struct ipv6hdr *ip6h = (struct ipv6hdr *)(buffer + nhoff);
 	int num_pkt = 0, num_coal = 0, pkt_idx;
 	const char *fail_reason = NULL;
 	int flow_order[num_flows * 2];
@@ -1203,7 +1242,7 @@ static void check_capacity_pkts(int fd)
 
 	while (1) {
 		ip_ext_len = 0;
-		pkt_size = recv(fd, buffer, IP_MAXPACKET + ETH_HLEN + 1, 0);
+		pkt_size = recv(fd, buffer, sizeof(buffer), 0);
 		if (pkt_size < 0)
 			recv_error(fd, errno);
 
@@ -1499,6 +1538,12 @@ static void gro_sender(void)
 		usleep(fin_delay_us);
 		write_packet(txfd, fin_pkt, total_hdr_len, &daddr);
 
+	/* PPPoE sub-tests */
+	} else if (strcmp(testname, "pppoe_sid") == 0) {
+		send_changed_pppoe_sid(txfd, &daddr);
+		usleep(fin_delay_us);
+		write_packet(txfd, fin_pkt, total_hdr_len, &daddr);
+
 	} else {
 		error(1, 0, "Unknown testcase: %s", testname);
 	}
@@ -1716,6 +1761,12 @@ static void gro_receiver(void)
 	} else if (strcmp(testname, "capacity") == 0) {
 		check_capacity_pkts(rxfd);
 
+	} else if (strcmp(testname, "pppoe_sid") == 0) {
+		correct_payload[0] = PAYLOAD_LEN;
+		correct_payload[1] = PAYLOAD_LEN;
+		printf("different PPPoE session ID doesn't coalesce: ");
+		check_recv_pkts(rxfd, correct_payload, 2);
+
 	} else {
 		error(1, 0, "Test case error: unknown testname %s", testname);
 	}
@@ -1734,6 +1785,8 @@ static void parse_args(int argc, char **argv)
 		{ "ipv6", no_argument, NULL, '6' },
 		{ "ipip", no_argument, NULL, 'e' },
 		{ "ip6ip6", no_argument, NULL, 'E' },
+		{ "pppoev4", no_argument, NULL, 'p' },
+		{ "pppoev6", no_argument, NULL, 'P' },
 		{ "num-flows", required_argument, NULL, 'n' },
 		{ "rx", no_argument, NULL, 'r' },
 		{ "saddr", required_argument, NULL, 's' },
@@ -1745,7 +1798,7 @@ static void parse_args(int argc, char **argv)
 	};
 	int c;
 
-	while ((c = getopt_long(argc, argv, "46d:D:eEi:n:rs:S:t:ov", opts, NULL)) != -1) {
+	while ((c = getopt_long(argc, argv, "46d:D:eEi:n:pPrs:S:t:ov", opts, NULL)) != -1) {
 		switch (c) {
 		case '4':
 			proto = PF_INET;
@@ -1765,6 +1818,16 @@ static void parse_args(int argc, char **argv)
 			proto = PF_INET6;
 			ethhdr_proto = htons(ETH_P_IPV6);
 			break;
+		case 'p':
+			pppoe = true;
+			proto = PF_INET;
+			ethhdr_proto = htons(ETH_P_PPP_SES);
+			break;
+		case 'P':
+			pppoe = true;
+			proto = PF_INET6;
+			ethhdr_proto = htons(ETH_P_PPP_SES);
+			break;
 		case 'd':
 			addr4_dst = addr6_dst = optarg;
 			break;
@@ -1812,6 +1875,10 @@ int main(int argc, char **argv)
 	} else if (ip6ip6) {
 		tcp_offset = ETH_HLEN + sizeof(struct ipv6hdr) * 2;
 		total_hdr_len = tcp_offset + sizeof(struct tcphdr);
+	} else if (pppoe) {
+		tcp_offset = ETH_HLEN + PPPOE_SES_HLEN +
+			(proto == PF_INET ? sizeof(struct iphdr) : sizeof(struct ipv6hdr));
+		total_hdr_len = tcp_offset + sizeof(struct tcphdr);
 	} else if (proto == PF_INET) {
 		tcp_offset = ETH_HLEN + sizeof(struct iphdr);
 		total_hdr_len = tcp_offset + sizeof(struct tcphdr);
-- 
2.43.0