[PATCH net-next v5 0/2] udp_tunnel: GRO optimizations

[PATCH net-next v5 0/2] udp_tunnel: GRO optimizations

[Paolo Abeni]

The UDP tunnel GRO stage is source of measurable overhead for workload
based on UDP-encapsulated traffic: each incoming packets requires a full
UDP socket lookup and an indirect call.

In the most common setups a single UDP tunnel device is used. In such
case we can optimize both the lookup and the indirect call.

Patch 1 tracks per netns the active UDP tunnels and replaces the socket
lookup with a single destination port comparison when possible.

Patch 2 tracks the different types of UDP tunnels and replaces the
indirect call with a static one when there is a single UDP tunnel type
active.

I measure ~10% performance improvement in TCP over UDP tunnel stream
tests on top of this series.
---
v4 -> v5:
 - incorporated the follow-up fixes:
   https://lore.kernel.org/netdev/cover.1742557254.git.pabeni@redhat.com/
 - more accurate benchmarking
 v4: https://lore.kernel.org/netdev/cover.1741718157.git.pabeni@redhat.com/

v3 -> v4:
 - cleanup lookup in patch 2
 - more RCU_INIT_POINTER usage in patch 1
 (see the individual patches changelog for more details)
 v3: https://lore.kernel.org/netdev/cover.1741632298.git.pabeni@redhat.com

v2 -> v3:
 - avoid unneeded checks in udp_tunnel_update_gro_rcv()
 - use RCU_INIT_POINTER() when possible
 - drop 'inline' from c file
 v2: https://lore.kernel.org/netdev/cover.1741338765.git.pabeni@redhat.com/

v1 -> v2:
 - fixed a couple of typos
 - fixed UDP_TUNNEL=n build
 - clarified design choices 
 (see the individual patches changelog for more details)
 v1: https://lore.kernel.org/netdev/cover.1741275846.git.pabeni@redhat.com/

Paolo Abeni (2):
  udp_tunnel: create a fastpath GRO lookup.
  udp_tunnel: use static call for GRO hooks when  possible

 include/linux/udp.h        |  16 ++++
 include/net/netns/ipv4.h   |  11 +++
 include/net/udp.h          |   1 +
 include/net/udp_tunnel.h   |  16 ++++
 net/ipv4/udp.c             |  13 ++-
 net/ipv4/udp_offload.c     | 172 ++++++++++++++++++++++++++++++++++++-
 net/ipv4/udp_tunnel_core.c |  13 +++
 net/ipv6/udp.c             |   2 +
 net/ipv6/udp_offload.c     |   5 ++
 9 files changed, 247 insertions(+), 2 deletions(-)

-- 
2.49.0

[PATCH net-next v5 1/2] udp_tunnel: create a fastpath GRO lookup.

[Paolo Abeni]

Most UDP tunnels bind a socket to a local port, with ANY address, no
peer and no interface index specified.
Additionally it's quite common to have a single tunnel device per
namespace.

Track in each namespace the UDP tunnel socket respecting the above.
When only a single one is present, store a reference in the netns.

When such reference is not NULL, UDP tunnel GRO lookup just need to
match the incoming packet destination port vs the socket local port.

The tunnel socket never sets the reuse[port] flag[s]. When bound to no
address and interface, no other socket can exist in the same netns
matching the specified local port.

Matching packets with non-local destination addresses will be
aggregated, and eventually segmented as needed - no behavior changes
intended.

Restrict the optimization to kernel sockets only: it covers all the
relevant use-cases, and user-space owned sockets could be disconnected
and rebound after setup_udp_tunnel_sock(), breaking the uniqueness
assumption

Note that the UDP tunnel socket reference is stored into struct
netns_ipv4 for both IPv4 and IPv6 tunnels. That is intentional to keep
all the fastpath-related netns fields in the same struct and allow
cacheline-based optimization. Currently both the IPv4 and IPv6 socket
pointer share the same cacheline as the `udp_table` field.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
v4 -> v5:
 - deal with races at removal time moving the list check under the
   tunnel gro lock
 - restrict to kernel socket only.
---
 include/linux/udp.h        | 16 ++++++++++++++++
 include/net/netns/ipv4.h   | 11 +++++++++++
 include/net/udp.h          |  1 +
 include/net/udp_tunnel.h   | 12 ++++++++++++
 net/ipv4/udp.c             | 13 ++++++++++++-
 net/ipv4/udp_offload.c     | 37 +++++++++++++++++++++++++++++++++++++
 net/ipv4/udp_tunnel_core.c | 13 +++++++++++++
 net/ipv6/udp.c             |  2 ++
 net/ipv6/udp_offload.c     |  5 +++++
 9 files changed, 109 insertions(+), 1 deletion(-)

diff --git a/include/linux/udp.h b/include/linux/udp.h
index 0807e21cfec95..895240177f4f4 100644
--- a/include/linux/udp.h
+++ b/include/linux/udp.h
@@ -101,6 +101,13 @@ struct udp_sock {
 
 	/* Cache friendly copy of sk->sk_peek_off >= 0 */
 	bool		peeking_with_offset;
+
+	/*
+	 * Accounting for the tunnel GRO fastpath.
+	 * Unprotected by compilers guard, as it uses space available in
+	 * the last UDP socket cacheline.
+	 */
+	struct hlist_node	tunnel_list;
 };
 
 #define udp_test_bit(nr, sk)			\
@@ -219,4 +226,13 @@ static inline void udp_allow_gso(struct sock *sk)
 
 #define IS_UDPLITE(__sk) (__sk->sk_protocol == IPPROTO_UDPLITE)
 
+static inline struct sock *udp_tunnel_sk(const struct net *net, bool is_ipv6)
+{
+#if IS_ENABLED(CONFIG_NET_UDP_TUNNEL)
+	return rcu_dereference(net->ipv4.udp_tunnel_gro[is_ipv6].sk);
+#else
+	return NULL;
+#endif
+}
+
 #endif	/* _LINUX_UDP_H */
diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h
index 650b2dc9199f4..6373e3f17da84 100644
--- a/include/net/netns/ipv4.h
+++ b/include/net/netns/ipv4.h
@@ -47,6 +47,11 @@ struct sysctl_fib_multipath_hash_seed {
 };
 #endif
 
+struct udp_tunnel_gro {
+	struct sock __rcu *sk;
+	struct hlist_head list;
+};
+
 struct netns_ipv4 {
 	/* Cacheline organization can be found documented in
 	 * Documentation/networking/net_cachelines/netns_ipv4_sysctl.rst.
@@ -85,6 +90,11 @@ struct netns_ipv4 {
 	struct inet_timewait_death_row tcp_death_row;
 	struct udp_table *udp_table;
 
+#if IS_ENABLED(CONFIG_NET_UDP_TUNNEL)
+	/* Not in a pernet subsys because need to be available at GRO stage */
+	struct udp_tunnel_gro udp_tunnel_gro[2];
+#endif
+
 #ifdef CONFIG_SYSCTL
 	struct ctl_table_header	*forw_hdr;
 	struct ctl_table_header	*frags_hdr;
@@ -277,4 +287,5 @@ struct netns_ipv4 {
 	struct hlist_head	*inet_addr_lst;
 	struct delayed_work	addr_chk_work;
 };
+
 #endif
diff --git a/include/net/udp.h b/include/net/udp.h
index 6e89520e100dc..a772510b2aa58 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -290,6 +290,7 @@ static inline void udp_lib_init_sock(struct sock *sk)
 	struct udp_sock *up = udp_sk(sk);
 
 	skb_queue_head_init(&up->reader_queue);
+	INIT_HLIST_NODE(&up->tunnel_list);
 	up->forward_threshold = sk->sk_rcvbuf >> 2;
 	set_bit(SOCK_CUSTOM_SOCKOPT, &sk->sk_socket->flags);
 }
diff --git a/include/net/udp_tunnel.h b/include/net/udp_tunnel.h
index a93dc51f6323e..1bb2b852e90eb 100644
--- a/include/net/udp_tunnel.h
+++ b/include/net/udp_tunnel.h
@@ -191,6 +191,18 @@ static inline int udp_tunnel_handle_offloads(struct sk_buff *skb, bool udp_csum)
 }
 #endif
 
+#if IS_ENABLED(CONFIG_NET_UDP_TUNNEL)
+void udp_tunnel_update_gro_lookup(struct net *net, struct sock *sk, bool add);
+#else
+static inline void udp_tunnel_update_gro_lookup(struct net *net,
+						struct sock *sk, bool add) {}
+#endif
+
+static inline void udp_tunnel_cleanup_gro(struct sock *sk)
+{
+	udp_tunnel_update_gro_lookup(sock_net(sk), sk, false);
+}
+
 static inline void udp_tunnel_encap_enable(struct sock *sk)
 {
 	if (udp_test_and_set_bit(ENCAP_ENABLED, sk))
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 2742cc7602bb5..04cd3353f1d46 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -2897,8 +2897,10 @@ void udp_destroy_sock(struct sock *sk)
 			if (encap_destroy)
 				encap_destroy(sk);
 		}
-		if (udp_test_bit(ENCAP_ENABLED, sk))
+		if (udp_test_bit(ENCAP_ENABLED, sk)) {
 			static_branch_dec(&udp_encap_needed_key);
+			udp_tunnel_cleanup_gro(sk);
+		}
 	}
 }
 
@@ -3810,6 +3812,15 @@ static void __net_init udp_set_table(struct net *net)
 
 static int __net_init udp_pernet_init(struct net *net)
 {
+#if IS_ENABLED(CONFIG_NET_UDP_TUNNEL)
+	int i;
+
+	/* No tunnel is configured */
+	for (i = 0; i < ARRAY_SIZE(net->ipv4.udp_tunnel_gro); ++i) {
+		INIT_HLIST_HEAD(&net->ipv4.udp_tunnel_gro[i].list);
+		RCU_INIT_POINTER(net->ipv4.udp_tunnel_gro[i].sk, NULL);
+	}
+#endif
 	udp_sysctl_init(net);
 	udp_set_table(net);
 
diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
index 2c0725583be39..69fc4eae82509 100644
--- a/net/ipv4/udp_offload.c
+++ b/net/ipv4/udp_offload.c
@@ -12,6 +12,38 @@
 #include <net/udp.h>
 #include <net/protocol.h>
 #include <net/inet_common.h>
+#include <net/udp_tunnel.h>
+
+#if IS_ENABLED(CONFIG_NET_UDP_TUNNEL)
+static DEFINE_SPINLOCK(udp_tunnel_gro_lock);
+
+void udp_tunnel_update_gro_lookup(struct net *net, struct sock *sk, bool add)
+{
+	bool is_ipv6 = sk->sk_family == AF_INET6;
+	struct udp_sock *tup, *up = udp_sk(sk);
+	struct udp_tunnel_gro *udp_tunnel_gro;
+
+	spin_lock(&udp_tunnel_gro_lock);
+	udp_tunnel_gro = &net->ipv4.udp_tunnel_gro[is_ipv6];
+	if (add)
+		hlist_add_head(&up->tunnel_list, &udp_tunnel_gro->list);
+	else if (up->tunnel_list.pprev)
+		hlist_del_init(&up->tunnel_list);
+
+	if (udp_tunnel_gro->list.first &&
+	    !udp_tunnel_gro->list.first->next) {
+		tup = hlist_entry(udp_tunnel_gro->list.first, struct udp_sock,
+				  tunnel_list);
+
+		rcu_assign_pointer(udp_tunnel_gro->sk, (struct sock *)tup);
+	} else {
+		RCU_INIT_POINTER(udp_tunnel_gro->sk, NULL);
+	}
+
+	spin_unlock(&udp_tunnel_gro_lock);
+}
+EXPORT_SYMBOL_GPL(udp_tunnel_update_gro_lookup);
+#endif
 
 static struct sk_buff *__skb_udp_tunnel_segment(struct sk_buff *skb,
 	netdev_features_t features,
@@ -635,8 +667,13 @@ static struct sock *udp4_gro_lookup_skb(struct sk_buff *skb, __be16 sport,
 {
 	const struct iphdr *iph = skb_gro_network_header(skb);
 	struct net *net = dev_net_rcu(skb->dev);
+	struct sock *sk;
 	int iif, sdif;
 
+	sk = udp_tunnel_sk(net, false);
+	if (sk && dport == htons(sk->sk_num))
+		return sk;
+
 	inet_get_iif_sdif(skb, &iif, &sdif);
 
 	return __udp4_lib_lookup(net, iph->saddr, sport,
diff --git a/net/ipv4/udp_tunnel_core.c b/net/ipv4/udp_tunnel_core.c
index 619a53eb672da..3d1214e6df0ea 100644
--- a/net/ipv4/udp_tunnel_core.c
+++ b/net/ipv4/udp_tunnel_core.c
@@ -58,6 +58,15 @@ int udp_sock_create4(struct net *net, struct udp_port_cfg *cfg,
 }
 EXPORT_SYMBOL(udp_sock_create4);
 
+static bool sk_saddr_any(struct sock *sk)
+{
+#if IS_ENABLED(CONFIG_IPV6)
+	return ipv6_addr_any(&sk->sk_v6_rcv_saddr);
+#else
+	return !sk->sk_rcv_saddr;
+#endif
+}
+
 void setup_udp_tunnel_sock(struct net *net, struct socket *sock,
 			   struct udp_tunnel_sock_cfg *cfg)
 {
@@ -80,6 +89,10 @@ void setup_udp_tunnel_sock(struct net *net, struct socket *sock,
 	udp_sk(sk)->gro_complete = cfg->gro_complete;
 
 	udp_tunnel_encap_enable(sk);
+
+	if (!sk->sk_dport && !sk->sk_bound_dev_if && sk_saddr_any(sk) &&
+	    sk->sk_kern_sock)
+		udp_tunnel_update_gro_lookup(net, sk, true);
 }
 EXPORT_SYMBOL_GPL(setup_udp_tunnel_sock);
 
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 024458ef163c9..7317f8e053f1c 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -46,6 +46,7 @@
 #include <net/tcp_states.h>
 #include <net/ip6_checksum.h>
 #include <net/ip6_tunnel.h>
+#include <net/udp_tunnel.h>
 #include <net/xfrm.h>
 #include <net/inet_hashtables.h>
 #include <net/inet6_hashtables.h>
@@ -1825,6 +1826,7 @@ void udpv6_destroy_sock(struct sock *sk)
 		if (udp_test_bit(ENCAP_ENABLED, sk)) {
 			static_branch_dec(&udpv6_encap_needed_key);
 			udp_encap_disable();
+			udp_tunnel_cleanup_gro(sk);
 		}
 	}
 }
diff --git a/net/ipv6/udp_offload.c b/net/ipv6/udp_offload.c
index 404212dfc99ab..d8445ac1b2e43 100644
--- a/net/ipv6/udp_offload.c
+++ b/net/ipv6/udp_offload.c
@@ -118,8 +118,13 @@ static struct sock *udp6_gro_lookup_skb(struct sk_buff *skb, __be16 sport,
 {
 	const struct ipv6hdr *iph = skb_gro_network_header(skb);
 	struct net *net = dev_net_rcu(skb->dev);
+	struct sock *sk;
 	int iif, sdif;
 
+	sk = udp_tunnel_sk(net, true);
+	if (sk && dport == htons(sk->sk_num))
+		return sk;
+
 	inet6_get_iif_sdif(skb, &iif, &sdif);
 
 	return __udp6_lib_lookup(net, &iph->saddr, sport,
-- 
2.49.0

[PATCH net-next v5 2/2] udp_tunnel: use static call for GRO hooks when possible

[Paolo Abeni]

It's quite common to have a single UDP tunnel type active in the
whole system. In such a case we can replace the indirect call for
the UDP tunnel GRO callback with a static call.

Add the related accounting in the control path and switch to static
call when possible. To keep the code simple use a static array for
the registered tunnel types, and size such array based on the kernel
config.

Note that there are valid kernel configurations leading to
UDP_MAX_TUNNEL_TYPES == 0 even with IS_ENABLED(CONFIG_NET_UDP_TUNNEL),
Explicitly skip the accounting in such a case, to avoid compile warning
when accessing "udp_tunnel_gro_types".

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
v4 -> v5:
 - move the add hook in udp_tunnel_encap_enable() to deal with xfrm
 - avoid warnings when UDP_MAX_TUNNEL_TYPES == 0
---
 include/net/udp_tunnel.h |   4 ++
 net/ipv4/udp_offload.c   | 135 ++++++++++++++++++++++++++++++++++++++-
 2 files changed, 138 insertions(+), 1 deletion(-)

diff --git a/include/net/udp_tunnel.h b/include/net/udp_tunnel.h
index 1bb2b852e90eb..288f06f23a804 100644
--- a/include/net/udp_tunnel.h
+++ b/include/net/udp_tunnel.h
@@ -193,13 +193,16 @@ static inline int udp_tunnel_handle_offloads(struct sk_buff *skb, bool udp_csum)
 
 #if IS_ENABLED(CONFIG_NET_UDP_TUNNEL)
 void udp_tunnel_update_gro_lookup(struct net *net, struct sock *sk, bool add);
+void udp_tunnel_update_gro_rcv(struct sock *sk, bool add);
 #else
 static inline void udp_tunnel_update_gro_lookup(struct net *net,
 						struct sock *sk, bool add) {}
+static inline void udp_tunnel_update_gro_rcv(struct sock *sk, bool add) {}
 #endif
 
 static inline void udp_tunnel_cleanup_gro(struct sock *sk)
 {
+	udp_tunnel_update_gro_rcv(sk, false);
 	udp_tunnel_update_gro_lookup(sock_net(sk), sk, false);
 }
 
@@ -212,6 +215,7 @@ static inline void udp_tunnel_encap_enable(struct sock *sk)
 	if (READ_ONCE(sk->sk_family) == PF_INET6)
 		ipv6_stub->udpv6_encap_enable();
 #endif
+	udp_tunnel_update_gro_rcv(sk, true);
 	udp_encap_enable();
 }
 
diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
index 69fc4eae82509..787b2947d3a04 100644
--- a/net/ipv4/udp_offload.c
+++ b/net/ipv4/udp_offload.c
@@ -15,6 +15,38 @@
 #include <net/udp_tunnel.h>
 
 #if IS_ENABLED(CONFIG_NET_UDP_TUNNEL)
+
+/*
+ * Dummy GRO tunnel callback, exists mainly to avoid dangling/NULL
+ * values for the udp tunnel static call.
+ */
+static struct sk_buff *dummy_gro_rcv(struct sock *sk,
+				     struct list_head *head,
+				     struct sk_buff *skb)
+{
+	NAPI_GRO_CB(skb)->flush = 1;
+	return NULL;
+}
+
+typedef struct sk_buff *(*udp_tunnel_gro_rcv_t)(struct sock *sk,
+						struct list_head *head,
+						struct sk_buff *skb);
+
+struct udp_tunnel_type_entry {
+	udp_tunnel_gro_rcv_t gro_receive;
+	refcount_t count;
+};
+
+#define UDP_MAX_TUNNEL_TYPES (IS_ENABLED(CONFIG_GENEVE) + \
+			      IS_ENABLED(CONFIG_VXLAN) * 2 + \
+			      IS_ENABLED(CONFIG_NET_FOU) * 2 + \
+			      IS_ENABLED(CONFIG_XFRM) * 2)
+
+DEFINE_STATIC_CALL(udp_tunnel_gro_rcv, dummy_gro_rcv);
+static DEFINE_STATIC_KEY_FALSE(udp_tunnel_static_call);
+static struct mutex udp_tunnel_gro_type_lock;
+static struct udp_tunnel_type_entry udp_tunnel_gro_types[UDP_MAX_TUNNEL_TYPES];
+static unsigned int udp_tunnel_gro_type_nr;
 static DEFINE_SPINLOCK(udp_tunnel_gro_lock);
 
 void udp_tunnel_update_gro_lookup(struct net *net, struct sock *sk, bool add)
@@ -43,6 +75,105 @@ void udp_tunnel_update_gro_lookup(struct net *net, struct sock *sk, bool add)
 	spin_unlock(&udp_tunnel_gro_lock);
 }
 EXPORT_SYMBOL_GPL(udp_tunnel_update_gro_lookup);
+
+void udp_tunnel_update_gro_rcv(struct sock *sk, bool add)
+{
+	struct udp_tunnel_type_entry *cur = NULL;
+	struct udp_sock *up = udp_sk(sk);
+	int i, old_gro_type_nr;
+
+	if (!UDP_MAX_TUNNEL_TYPES || !up->gro_receive)
+		return;
+
+	mutex_lock(&udp_tunnel_gro_type_lock);
+
+	/* Check if the static call is permanently disabled. */
+	if (udp_tunnel_gro_type_nr > UDP_MAX_TUNNEL_TYPES)
+		goto out;
+
+	for (i = 0; i < udp_tunnel_gro_type_nr; i++)
+		if (udp_tunnel_gro_types[i].gro_receive == up->gro_receive)
+			cur = &udp_tunnel_gro_types[i];
+
+	old_gro_type_nr = udp_tunnel_gro_type_nr;
+	if (add) {
+		/*
+		 * Update the matching entry, if found, or add a new one
+		 * if needed
+		 */
+		if (cur) {
+			refcount_inc(&cur->count);
+			goto out;
+		}
+
+		if (unlikely(udp_tunnel_gro_type_nr == UDP_MAX_TUNNEL_TYPES)) {
+			pr_err_once("Too many UDP tunnel types, please increase UDP_MAX_TUNNEL_TYPES\n");
+			/* Ensure static call will never be enabled */
+			udp_tunnel_gro_type_nr = UDP_MAX_TUNNEL_TYPES + 1;
+		} else {
+			cur = &udp_tunnel_gro_types[udp_tunnel_gro_type_nr++];
+			refcount_set(&cur->count, 1);
+			cur->gro_receive = up->gro_receive;
+		}
+	} else {
+		/*
+		 * The stack cleanups only successfully added tunnel, the
+		 * lookup on removal should never fail.
+		 */
+		if (WARN_ON_ONCE(!cur))
+			goto out;
+
+		if (!refcount_dec_and_test(&cur->count))
+			goto out;
+
+		/* Avoid gaps, so that the enable tunnel has always id 0 */
+		*cur = udp_tunnel_gro_types[--udp_tunnel_gro_type_nr];
+	}
+
+	if (udp_tunnel_gro_type_nr == 1) {
+		static_call_update(udp_tunnel_gro_rcv,
+				   udp_tunnel_gro_types[0].gro_receive);
+		static_branch_enable(&udp_tunnel_static_call);
+	} else if (old_gro_type_nr == 1) {
+		static_branch_disable(&udp_tunnel_static_call);
+		static_call_update(udp_tunnel_gro_rcv, dummy_gro_rcv);
+	}
+
+out:
+	mutex_unlock(&udp_tunnel_gro_type_lock);
+}
+EXPORT_SYMBOL_GPL(udp_tunnel_update_gro_rcv);
+
+static void udp_tunnel_gro_init(void)
+{
+	mutex_init(&udp_tunnel_gro_type_lock);
+}
+
+static struct sk_buff *udp_tunnel_gro_rcv(struct sock *sk,
+					  struct list_head *head,
+					  struct sk_buff *skb)
+{
+	if (static_branch_likely(&udp_tunnel_static_call)) {
+		if (unlikely(gro_recursion_inc_test(skb))) {
+			NAPI_GRO_CB(skb)->flush |= 1;
+			return NULL;
+		}
+		return static_call(udp_tunnel_gro_rcv)(sk, head, skb);
+	}
+	return call_gro_receive_sk(udp_sk(sk)->gro_receive, sk, head, skb);
+}
+
+#else
+
+static void udp_tunnel_gro_init(void) {}
+
+static struct sk_buff *udp_tunnel_gro_rcv(struct sock *sk,
+					  struct list_head *head,
+					  struct sk_buff *skb)
+{
+	return call_gro_receive_sk(udp_sk(sk)->gro_receive, sk, head, skb);
+}
+
 #endif
 
 static struct sk_buff *__skb_udp_tunnel_segment(struct sk_buff *skb,
@@ -654,7 +785,7 @@ struct sk_buff *udp_gro_receive(struct list_head *head, struct sk_buff *skb,
 
 	skb_gro_pull(skb, sizeof(struct udphdr)); /* pull encapsulating udp header */
 	skb_gro_postpull_rcsum(skb, uh, sizeof(struct udphdr));
-	pp = call_gro_receive_sk(udp_sk(sk)->gro_receive, sk, head, skb);
+	pp = udp_tunnel_gro_rcv(sk, head, skb);
 
 out:
 	skb_gro_flush_final(skb, pp, flush);
@@ -804,5 +935,7 @@ int __init udpv4_offload_init(void)
 			.gro_complete =	udp4_gro_complete,
 		},
 	};
+
+	udp_tunnel_gro_init();
 	return inet_add_offload(&net_hotdata.udpv4_offload, IPPROTO_UDP);
 }
-- 
2.49.0

Re: [PATCH net-next v5 1/2] udp_tunnel: create a fastpath GRO lookup.

[Willem de Bruijn]

Paolo Abeni wrote:
> Most UDP tunnels bind a socket to a local port, with ANY address, no
> peer and no interface index specified.
> Additionally it's quite common to have a single tunnel device per
> namespace.
> 
> Track in each namespace the UDP tunnel socket respecting the above.
> When only a single one is present, store a reference in the netns.
> 
> When such reference is not NULL, UDP tunnel GRO lookup just need to
> match the incoming packet destination port vs the socket local port.
> 
> The tunnel socket never sets the reuse[port] flag[s]. When bound to no
> address and interface, no other socket can exist in the same netns
> matching the specified local port.
> 
> Matching packets with non-local destination addresses will be
> aggregated, and eventually segmented as needed - no behavior changes
> intended.
> 
> Restrict the optimization to kernel sockets only: it covers all the
> relevant use-cases, and user-space owned sockets could be disconnected
> and rebound after setup_udp_tunnel_sock(), breaking the uniqueness
> assumption
> 
> Note that the UDP tunnel socket reference is stored into struct
> netns_ipv4 for both IPv4 and IPv6 tunnels. That is intentional to keep
> all the fastpath-related netns fields in the same struct and allow
> cacheline-based optimization. Currently both the IPv4 and IPv6 socket
> pointer share the same cacheline as the `udp_table` field.
> 
> Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Reviewed-by: Willem de Bruijn <willemb@google.com>

Re: [PATCH net-next v5 2/2] udp_tunnel: use static call for GRO hooks when possible

[Willem de Bruijn]

Paolo Abeni wrote:
> It's quite common to have a single UDP tunnel type active in the
> whole system. In such a case we can replace the indirect call for
> the UDP tunnel GRO callback with a static call.
> 
> Add the related accounting in the control path and switch to static
> call when possible. To keep the code simple use a static array for
> the registered tunnel types, and size such array based on the kernel
> config.
> 
> Note that there are valid kernel configurations leading to
> UDP_MAX_TUNNEL_TYPES == 0 even with IS_ENABLED(CONFIG_NET_UDP_TUNNEL),
> Explicitly skip the accounting in such a case, to avoid compile warning
> when accessing "udp_tunnel_gro_types".
> 
> Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Reviewed-by: Willem de Bruijn <willemb@google.com>

Re: [PATCH net-next v5 0/2] udp_tunnel: GRO optimizations

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Mon,  7 Apr 2025 17:45:40 +0200 you wrote:
> The UDP tunnel GRO stage is source of measurable overhead for workload
> based on UDP-encapsulated traffic: each incoming packets requires a full
> UDP socket lookup and an indirect call.
> 
> In the most common setups a single UDP tunnel device is used. In such
> case we can optimize both the lookup and the indirect call.
> 
> [...]

Here is the summary with links:
  - [net-next,v5,1/2] udp_tunnel: create a fastpath GRO lookup.
    https://git.kernel.org/netdev/net-next/c/a36283e2b683
  - [net-next,v5,2/2] udp_tunnel: use static call for GRO hooks when possible
    https://git.kernel.org/netdev/net-next/c/5d7f5b2f6b93

You are awesome, thank you!
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