Merge branch 'mptcp-refactor-token-container'

Paolo Abeni says:

====================
mptcp: refactor token container

Currently the msk sockets are stored in a single radix tree, protected by a
global spin_lock. This series moves to an hash table, allocated at boot time,
with per bucker spin_lock - alike inet_hashtables, but using a different key:
the token itself.

The above improves scalability, as write operations will have a far later chance
to compete for lock acquisition, allows lockless lookup, and will allow
easier msk traversing - e.g. for diag interface implementation's sake.

This also introduces trivial, related, kunit tests and move the existing in
kernel's one to kunit.

v1 -> v2:
 - fixed a few extra and sparse warns
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

11 files changed, 487 insertions, 190 deletions

diff --git a/net/mptcp/Kconfig b/net/mptcp/Kconfig
index a9ed3bf1d93f..af84fce70bb0 100644
--- a/net/mptcp/Kconfig
+++ b/net/mptcp/Kconfig
@@ -18,12 +18,20 @@ config MPTCP_IPV6
 	select IPV6
 	default y
 
-config MPTCP_HMAC_TEST
-	bool "Tests for MPTCP HMAC implementation"
+endif
+
+config MPTCP_KUNIT_TESTS
+	tristate "This builds the MPTCP KUnit tests" if !KUNIT_ALL_TESTS
+	select MPTCP
+	depends on KUNIT
+	default KUNIT_ALL_TESTS
 	help
-	  This option enable boot time self-test for the HMAC implementation
-	  used by the MPTCP code
+	  Currently covers the MPTCP crypto and token helpers.
+	  Only useful for kernel devs running KUnit test harness and are not
+	  for inclusion into a production build.
 
-	  Say N if you are unsure.
+	  For more information on KUnit and unit tests in general please refer
+	  to the KUnit documentation in Documentation/dev-tools/kunit/.
+
+	  If unsure, say N.
 
-endif
diff --git a/net/mptcp/Makefile b/net/mptcp/Makefile
index baa0640527c7..c53f9b845523 100644
--- a/net/mptcp/Makefile
+++ b/net/mptcp/Makefile
@@ -3,3 +3,7 @@ obj-$(CONFIG_MPTCP) += mptcp.o
 
 mptcp-y := protocol.o subflow.o options.o token.o crypto.o ctrl.o pm.o diag.o \
 	   mib.o pm_netlink.o
+
+mptcp_crypto_test-objs := crypto_test.o
+mptcp_token_test-objs := token_test.o
+obj-$(CONFIG_MPTCP_KUNIT_TESTS) += mptcp_crypto_test.o mptcp_token_test.o
diff --git a/net/mptcp/crypto.c b/net/mptcp/crypto.c
index 3d980713a9e2..6c4ea979dfd4 100644
--- a/net/mptcp/crypto.c
+++ b/net/mptcp/crypto.c
@@ -87,65 +87,6 @@ void mptcp_crypto_hmac_sha(u64 key1, u64 key2, u8 *msg, int len, void *hmac)
 	sha256_final(&state, (u8 *)hmac);
 }
 
-#ifdef CONFIG_MPTCP_HMAC_TEST
-struct test_cast {
-	char *key;
-	char *msg;
-	char *result;
-};
-
-/* we can't reuse RFC 4231 test vectors, as we have constraint on the
- * input and key size.
- */
-static struct test_cast tests[] = {
-	{
-		.key = "0b0b0b0b0b0b0b0b",
-		.msg = "48692054",
-		.result = "8385e24fb4235ac37556b6b886db106284a1da671699f46db1f235ec622dcafa",
-	},
-	{
-		.key = "aaaaaaaaaaaaaaaa",
-		.msg = "dddddddd",
-		.result = "2c5e219164ff1dca1c4a92318d847bb6b9d44492984e1eb71aff9022f71046e9",
-	},
-	{
-		.key = "0102030405060708",
-		.msg = "cdcdcdcd",
-		.result = "e73b9ba9969969cefb04aa0d6df18ec2fcc075b6f23b4d8c4da736a5dbbc6e7d",
-	},
-};
-
-static int __init test_mptcp_crypto(void)
-{
-	char hmac[32], hmac_hex[65];
-	u32 nonce1, nonce2;
-	u64 key1, key2;
-	u8 msg[8];
-	int i, j;
-
-	for (i = 0; i < ARRAY_SIZE(tests); ++i) {
-		/* mptcp hmap will convert to be before computing the hmac */
-		key1 = be64_to_cpu(*((__be64 *)&tests[i].key[0]));
-		key2 = be64_to_cpu(*((__be64 *)&tests[i].key[8]));
-		nonce1 = be32_to_cpu(*((__be32 *)&tests[i].msg[0]));
-		nonce2 = be32_to_cpu(*((__be32 *)&tests[i].msg[4]));
-
-		put_unaligned_be32(nonce1, &msg[0]);
-		put_unaligned_be32(nonce2, &msg[4]);
-
-		mptcp_crypto_hmac_sha(key1, key2, msg, 8, hmac);
-		for (j = 0; j < 32; ++j)
-			sprintf(&hmac_hex[j << 1], "%02x", hmac[j] & 0xff);
-		hmac_hex[64] = 0;
-
-		if (memcmp(hmac_hex, tests[i].result, 64))
-			pr_err("test %d failed, got %s expected %s", i,
-			       hmac_hex, tests[i].result);
-		else
-			pr_info("test %d [ ok ]", i);
-	}
-	return 0;
-}
-
-late_initcall(test_mptcp_crypto);
+#if IS_MODULE(CONFIG_MPTCP_KUNIT_TESTS)
+EXPORT_SYMBOL_GPL(mptcp_crypto_hmac_sha);
 #endif
diff --git a/net/mptcp/crypto_test.c b/net/mptcp/crypto_test.c
new file mode 100644
index 000000000000..017248dea038
--- /dev/null
+++ b/net/mptcp/crypto_test.c
@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <kunit/test.h>
+
+#include "protocol.h"
+
+struct test_case {
+	char *key;
+	char *msg;
+	char *result;
+};
+
+/* we can't reuse RFC 4231 test vectors, as we have constraint on the
+ * input and key size.
+ */
+static struct test_case tests[] = {
+	{
+		.key = "0b0b0b0b0b0b0b0b",
+		.msg = "48692054",
+		.result = "8385e24fb4235ac37556b6b886db106284a1da671699f46db1f235ec622dcafa",
+	},
+	{
+		.key = "aaaaaaaaaaaaaaaa",
+		.msg = "dddddddd",
+		.result = "2c5e219164ff1dca1c4a92318d847bb6b9d44492984e1eb71aff9022f71046e9",
+	},
+	{
+		.key = "0102030405060708",
+		.msg = "cdcdcdcd",
+		.result = "e73b9ba9969969cefb04aa0d6df18ec2fcc075b6f23b4d8c4da736a5dbbc6e7d",
+	},
+};
+
+static void mptcp_crypto_test_basic(struct kunit *test)
+{
+	char hmac[32], hmac_hex[65];
+	u32 nonce1, nonce2;
+	u64 key1, key2;
+	u8 msg[8];
+	int i, j;
+
+	for (i = 0; i < ARRAY_SIZE(tests); ++i) {
+		/* mptcp hmap will convert to be before computing the hmac */
+		key1 = be64_to_cpu(*((__be64 *)&tests[i].key[0]));
+		key2 = be64_to_cpu(*((__be64 *)&tests[i].key[8]));
+		nonce1 = be32_to_cpu(*((__be32 *)&tests[i].msg[0]));
+		nonce2 = be32_to_cpu(*((__be32 *)&tests[i].msg[4]));
+
+		put_unaligned_be32(nonce1, &msg[0]);
+		put_unaligned_be32(nonce2, &msg[4]);
+
+		mptcp_crypto_hmac_sha(key1, key2, msg, 8, hmac);
+		for (j = 0; j < 32; ++j)
+			sprintf(&hmac_hex[j << 1], "%02x", hmac[j] & 0xff);
+		hmac_hex[64] = 0;
+
+		KUNIT_EXPECT_STREQ(test, &hmac_hex[0], tests[i].result);
+	}
+}
+
+static struct kunit_case mptcp_crypto_test_cases[] = {
+	KUNIT_CASE(mptcp_crypto_test_basic),
+	{}
+};
+
+static struct kunit_suite mptcp_crypto_suite = {
+	.name = "mptcp-crypto",
+	.test_cases = mptcp_crypto_test_cases,
+};
+
+kunit_test_suite(mptcp_crypto_suite);
+
+MODULE_LICENSE("GPL");
diff --git a/net/mptcp/pm.c b/net/mptcp/pm.c
index 977d9c8b1453..7de09fdd42a3 100644
--- a/net/mptcp/pm.c
+++ b/net/mptcp/pm.c
@@ -234,7 +234,7 @@ void mptcp_pm_close(struct mptcp_sock *msk)
 		sock_put((struct sock *)msk);
 }
 
-void mptcp_pm_init(void)
+void __init mptcp_pm_init(void)
 {
 	pm_wq = alloc_workqueue("pm_wq", WQ_UNBOUND | WQ_MEM_RECLAIM, 8);
 	if (!pm_wq)
diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index b78edf237ba0..c8820c4156e6 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -851,7 +851,7 @@ static struct pernet_operations mptcp_pm_pernet_ops = {
 	.size = sizeof(struct pm_nl_pernet),
 };
 
-void mptcp_pm_nl_init(void)
+void __init mptcp_pm_nl_init(void)
 {
 	if (register_pernet_subsys(&mptcp_pm_pernet_ops) < 0)
 		panic("Failed to register MPTCP PM pernet subsystem.\n");
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 3980fbb6f31e..be09fd525f8f 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1448,20 +1448,6 @@ struct sock *mptcp_sk_clone(const struct sock *sk,
 	msk->token = subflow_req->token;
 	msk->subflow = NULL;
 
-	if (unlikely(mptcp_token_new_accept(subflow_req->token, nsk))) {
-		nsk->sk_state = TCP_CLOSE;
-		bh_unlock_sock(nsk);
-
-		/* we can't call into mptcp_close() here - possible BH context
-		 * free the sock directly.
-		 * sk_clone_lock() sets nsk refcnt to two, hence call sk_free()
-		 * too.
-		 */
-		sk_common_release(nsk);
-		sk_free(nsk);
-		return NULL;
-	}
-
 	msk->write_seq = subflow_req->idsn + 1;
 	atomic64_set(&msk->snd_una, msk->write_seq);
 	if (mp_opt->mp_capable) {
@@ -1547,7 +1533,7 @@ static void mptcp_destroy(struct sock *sk)
 {
 	struct mptcp_sock *msk = mptcp_sk(sk);
 
-	mptcp_token_destroy(msk->token);
+	mptcp_token_destroy(msk);
 	if (msk->cached_ext)
 		__skb_ext_put(msk->cached_ext);
 
@@ -1636,6 +1622,20 @@ static void mptcp_release_cb(struct sock *sk)
 	}
 }
 
+static int mptcp_hash(struct sock *sk)
+{
+	/* should never be called,
+	 * we hash the TCP subflows not the master socket
+	 */
+	WARN_ON_ONCE(1);
+	return 0;
+}
+
+static void mptcp_unhash(struct sock *sk)
+{
+	/* called from sk_common_release(), but nothing to do here */
+}
+
 static int mptcp_get_port(struct sock *sk, unsigned short snum)
 {
 	struct mptcp_sock *msk = mptcp_sk(sk);
@@ -1679,7 +1679,6 @@ void mptcp_finish_connect(struct sock *ssk)
 	 */
 	WRITE_ONCE(msk->remote_key, subflow->remote_key);
 	WRITE_ONCE(msk->local_key, subflow->local_key);
-	WRITE_ONCE(msk->token, subflow->token);
 	WRITE_ONCE(msk->write_seq, subflow->idsn + 1);
 	WRITE_ONCE(msk->ack_seq, ack_seq);
 	WRITE_ONCE(msk->can_ack, 1);
@@ -1761,8 +1760,8 @@ static struct proto mptcp_prot = {
 	.sendmsg	= mptcp_sendmsg,
 	.recvmsg	= mptcp_recvmsg,
 	.release_cb	= mptcp_release_cb,
-	.hash		= inet_hash,
-	.unhash		= inet_unhash,
+	.hash		= mptcp_hash,
+	.unhash		= mptcp_unhash,
 	.get_port	= mptcp_get_port,
 	.sockets_allocated	= &mptcp_sockets_allocated,
 	.memory_allocated	= &tcp_memory_allocated,
@@ -1771,6 +1770,7 @@ static struct proto mptcp_prot = {
 	.sysctl_wmem_offset	= offsetof(struct net, ipv4.sysctl_tcp_wmem),
 	.sysctl_mem	= sysctl_tcp_mem,
 	.obj_size	= sizeof(struct mptcp_sock),
+	.slab_flags	= SLAB_TYPESAFE_BY_RCU,
 	.no_autobind	= true,
 };
 
@@ -1800,6 +1800,7 @@ static int mptcp_stream_connect(struct socket *sock, struct sockaddr *uaddr,
 				int addr_len, int flags)
 {
 	struct mptcp_sock *msk = mptcp_sk(sock->sk);
+	struct mptcp_subflow_context *subflow;
 	struct socket *ssock;
 	int err;
 
@@ -1812,19 +1813,23 @@ static int mptcp_stream_connect(struct socket *sock, struct sockaddr *uaddr,
 		goto do_connect;
 	}
 
+	mptcp_token_destroy(msk);
 	ssock = __mptcp_socket_create(msk, TCP_SYN_SENT);
 	if (IS_ERR(ssock)) {
 		err = PTR_ERR(ssock);
 		goto unlock;
 	}
 
+	subflow = mptcp_subflow_ctx(ssock->sk);
 #ifdef CONFIG_TCP_MD5SIG
 	/* no MPTCP if MD5SIG is enabled on this socket or we may run out of
 	 * TCP option space.
 	 */
 	if (rcu_access_pointer(tcp_sk(ssock->sk)->md5sig_info))
-		mptcp_subflow_ctx(ssock->sk)->request_mptcp = 0;
+		subflow->request_mptcp = 0;
 #endif
+	if (subflow->request_mptcp && mptcp_token_new_connect(ssock->sk))
+		subflow->request_mptcp = 0;
 
 do_connect:
 	err = ssock->ops->connect(ssock, uaddr, addr_len, flags);
@@ -1888,6 +1893,7 @@ static int mptcp_listen(struct socket *sock, int backlog)
 	pr_debug("msk=%p", msk);
 
 	lock_sock(sock->sk);
+	mptcp_token_destroy(msk);
 	ssock = __mptcp_socket_create(msk, TCP_LISTEN);
 	if (IS_ERR(ssock)) {
 		err = PTR_ERR(ssock);
@@ -2077,7 +2083,7 @@ static struct inet_protosw mptcp_protosw = {
 	.flags		= INET_PROTOSW_ICSK,
 };
 
-void mptcp_proto_init(void)
+void __init mptcp_proto_init(void)
 {
 	mptcp_prot.h.hashinfo = tcp_prot.h.hashinfo;
 
@@ -2086,6 +2092,7 @@ void mptcp_proto_init(void)
 
 	mptcp_subflow_init();
 	mptcp_pm_init();
+	mptcp_token_init();
 
 	if (proto_register(&mptcp_prot, 1) != 0)
 		panic("Failed to register MPTCP proto.\n");
@@ -2139,7 +2146,7 @@ static struct inet_protosw mptcp_v6_protosw = {
 	.flags		= INET_PROTOSW_ICSK,
 };
 
-int mptcp_proto_v6_init(void)
+int __init mptcp_proto_v6_init(void)
 {
 	int err;
 
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 482f53aed30a..c05552e5fa23 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -250,6 +250,7 @@ struct mptcp_subflow_request_sock {
 	u32	local_nonce;
 	u32	remote_nonce;
 	struct mptcp_sock	*msk;
+	struct hlist_nulls_node token_node;
 };
 
 static inline struct mptcp_subflow_request_sock *
@@ -337,7 +338,7 @@ mptcp_subflow_get_mapped_dsn(const struct mptcp_subflow_context *subflow)
 
 int mptcp_is_enabled(struct net *net);
 bool mptcp_subflow_data_available(struct sock *sk);
-void mptcp_subflow_init(void);
+void __init mptcp_subflow_init(void);
 
 /* called with sk socket lock held */
 int __mptcp_subflow_connect(struct sock *sk, int ifindex,
@@ -355,9 +356,9 @@ static inline void mptcp_subflow_tcp_fallback(struct sock *sk,
 	inet_csk(sk)->icsk_af_ops = ctx->icsk_af_ops;
 }
 
-void mptcp_proto_init(void);
+void __init mptcp_proto_init(void);
 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
-int mptcp_proto_v6_init(void);
+int __init mptcp_proto_v6_init(void);
 #endif
 
 struct sock *mptcp_sk_clone(const struct sock *sk,
@@ -372,12 +373,19 @@ bool mptcp_finish_join(struct sock *sk);
 void mptcp_data_acked(struct sock *sk);
 void mptcp_subflow_eof(struct sock *sk);
 
+void __init mptcp_token_init(void);
+static inline void mptcp_token_init_request(struct request_sock *req)
+{
+	mptcp_subflow_rsk(req)->token_node.pprev = NULL;
+}
+
 int mptcp_token_new_request(struct request_sock *req);
-void mptcp_token_destroy_request(u32 token);
+void mptcp_token_destroy_request(struct request_sock *req);
 int mptcp_token_new_connect(struct sock *sk);
-int mptcp_token_new_accept(u32 token, struct sock *conn);
+void mptcp_token_accept(struct mptcp_subflow_request_sock *r,
+			struct mptcp_sock *msk);
 struct mptcp_sock *mptcp_token_get_sock(u32 token);
-void mptcp_token_destroy(u32 token);
+void mptcp_token_destroy(struct mptcp_sock *msk);
 
 void mptcp_crypto_key_sha(u64 key, u32 *token, u64 *idsn);
 static inline void mptcp_crypto_key_gen_sha(u64 *key, u32 *token, u64 *idsn)
@@ -394,7 +402,7 @@ static inline void mptcp_crypto_key_gen_sha(u64 *key, u32 *token, u64 *idsn)
 
 void mptcp_crypto_hmac_sha(u64 key1, u64 key2, u8 *msg, int len, void *hmac);
 
-void mptcp_pm_init(void);
+void __init mptcp_pm_init(void);
 void mptcp_pm_data_init(struct mptcp_sock *msk);
 void mptcp_pm_close(struct mptcp_sock *msk);
 void mptcp_pm_new_connection(struct mptcp_sock *msk, int server_side);
@@ -428,7 +436,7 @@ bool mptcp_pm_addr_signal(struct mptcp_sock *msk, unsigned int remaining,
 			  struct mptcp_addr_info *saddr);
 int mptcp_pm_get_local_id(struct mptcp_sock *msk, struct sock_common *skc);
 
-void mptcp_pm_nl_init(void);
+void __init mptcp_pm_nl_init(void);
 void mptcp_pm_nl_data_init(struct mptcp_sock *msk);
 void mptcp_pm_nl_fully_established(struct mptcp_sock *msk);
 void mptcp_pm_nl_subflow_established(struct mptcp_sock *msk);
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 3838a0b3a21f..102db8c88e97 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -32,12 +32,9 @@ static void SUBFLOW_REQ_INC_STATS(struct request_sock *req,
 static int subflow_rebuild_header(struct sock *sk)
 {
 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
-	int local_id, err = 0;
+	int local_id;
 
-	if (subflow->request_mptcp && !subflow->token) {
-		pr_debug("subflow=%p", sk);
-		err = mptcp_token_new_connect(sk);
-	} else if (subflow->request_join && !subflow->local_nonce) {
+	if (subflow->request_join && !subflow->local_nonce) {
 		struct mptcp_sock *msk = (struct mptcp_sock *)subflow->conn;
 
 		pr_debug("subflow=%p", sk);
@@ -57,9 +54,6 @@ static int subflow_rebuild_header(struct sock *sk)
 	}
 
 out:
-	if (err)
-		return err;
-
 	return subflow->icsk_af_ops->rebuild_header(sk);
 }
 
@@ -72,8 +66,7 @@ static void subflow_req_destructor(struct request_sock *req)
 	if (subflow_req->msk)
 		sock_put((struct sock *)subflow_req->msk);
 
-	if (subflow_req->mp_capable)
-		mptcp_token_destroy_request(subflow_req->token);
+	mptcp_token_destroy_request(req);
 	tcp_request_sock_ops.destructor(req);
 }
 
@@ -135,6 +128,7 @@ static void subflow_init_req(struct request_sock *req,
 	subflow_req->mp_capable = 0;
 	subflow_req->mp_join = 0;
 	subflow_req->msk = NULL;
+	mptcp_token_init_request(req);
 
 #ifdef CONFIG_TCP_MD5SIG
 	/* no MPTCP if MD5SIG is enabled on this socket or we may run out of
@@ -250,7 +244,7 @@ static void subflow_finish_connect(struct sock *sk, const struct sk_buff *skb)
 		subflow->remote_nonce = mp_opt.nonce;
 		pr_debug("subflow=%p, thmac=%llu, remote_nonce=%u", subflow,
 			 subflow->thmac, subflow->remote_nonce);
-	} else if (subflow->request_mptcp) {
+	} else {
 		tp->is_mptcp = 0;
 	}
 
@@ -386,7 +380,7 @@ static void mptcp_sock_destruct(struct sock *sk)
 		sock_orphan(sk);
 	}
 
-	mptcp_token_destroy(mptcp_sk(sk)->token);
+	mptcp_token_destroy(mptcp_sk(sk));
 	inet_sock_destruct(sk);
 }
 
@@ -505,6 +499,7 @@ create_child:
 			 */
 			new_msk->sk_destruct = mptcp_sock_destruct;
 			mptcp_pm_new_connection(mptcp_sk(new_msk), 1);
+			mptcp_token_accept(subflow_req, mptcp_sk(new_msk));
 			ctx->conn = new_msk;
 			new_msk = NULL;
 
@@ -1255,7 +1250,7 @@ static int subflow_ops_init(struct request_sock_ops *subflow_ops)
 	return 0;
 }
 
-void mptcp_subflow_init(void)
+void __init mptcp_subflow_init(void)
 {
 	subflow_request_sock_ops = tcp_request_sock_ops;
 	if (subflow_ops_init(&subflow_request_sock_ops) != 0)
diff --git a/net/mptcp/token.c b/net/mptcp/token.c
index 33352dd99d4d..66a4990bd897 100644
--- a/net/mptcp/token.c
+++ b/net/mptcp/token.c
@@ -24,7 +24,7 @@
 
 #include <linux/kernel.h>
 #include <linux/module.h>
-#include <linux/radix-tree.h>
+#include <linux/memblock.h>
 #include <linux/ip.h>
 #include <linux/tcp.h>
 #include <net/sock.h>
@@ -33,10 +33,55 @@
 #include <net/mptcp.h>
 #include "protocol.h"
 
-static RADIX_TREE(token_tree, GFP_ATOMIC);
-static RADIX_TREE(token_req_tree, GFP_ATOMIC);
-static DEFINE_SPINLOCK(token_tree_lock);
-static int token_used __read_mostly;
+#define TOKEN_MAX_RETRIES	4
+#define TOKEN_MAX_CHAIN_LEN	4
+
+struct token_bucket {
+	spinlock_t		lock;
+	int			chain_len;
+	struct hlist_nulls_head	req_chain;
+	struct hlist_nulls_head	msk_chain;
+};
+
+static struct token_bucket *token_hash __read_mostly;
+static unsigned int token_mask __read_mostly;
+
+static struct token_bucket *token_bucket(u32 token)
+{
+	return &token_hash[token & token_mask];
+}
+
+/* called with bucket lock held */
+static struct mptcp_subflow_request_sock *
+__token_lookup_req(struct token_bucket *t, u32 token)
+{
+	struct mptcp_subflow_request_sock *req;
+	struct hlist_nulls_node *pos;
+
+	hlist_nulls_for_each_entry_rcu(req, pos, &t->req_chain, token_node)
+		if (req->token == token)
+			return req;
+	return NULL;
+}
+
+/* called with bucket lock held */
+static struct mptcp_sock *
+__token_lookup_msk(struct token_bucket *t, u32 token)
+{
+	struct hlist_nulls_node *pos;
+	struct sock *sk;
+
+	sk_nulls_for_each_rcu(sk, pos, &t->msk_chain)
+		if (mptcp_sk(sk)->token == token)
+			return mptcp_sk(sk);
+	return NULL;
+}
+
+static bool __token_bucket_busy(struct token_bucket *t, u32 token)
+{
+	return !token || t->chain_len >= TOKEN_MAX_CHAIN_LEN ||
+	       __token_lookup_req(t, token) || __token_lookup_msk(t, token);
+}
 
 /**
  * mptcp_token_new_request - create new key/idsn/token for subflow_request
@@ -52,30 +97,32 @@ static int token_used __read_mostly;
 int mptcp_token_new_request(struct request_sock *req)
 {
 	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
-	int err;
-
-	while (1) {
-		u32 token;
-
-		mptcp_crypto_key_gen_sha(&subflow_req->local_key,
-					 &subflow_req->token,
-					 &subflow_req->idsn);
-		pr_debug("req=%p local_key=%llu, token=%u, idsn=%llu\n",
-			 req, subflow_req->local_key, subflow_req->token,
-			 subflow_req->idsn);
-
-		token = subflow_req->token;
-		spin_lock_bh(&token_tree_lock);
-		if (!radix_tree_lookup(&token_req_tree, token) &&
-		    !radix_tree_lookup(&token_tree, token))
-			break;
-		spin_unlock_bh(&token_tree_lock);
+	int retries = TOKEN_MAX_RETRIES;
+	struct token_bucket *bucket;
+	u32 token;
+
+again:
+	mptcp_crypto_key_gen_sha(&subflow_req->local_key,
+				 &subflow_req->token,
+				 &subflow_req->idsn);
+	pr_debug("req=%p local_key=%llu, token=%u, idsn=%llu\n",
+		 req, subflow_req->local_key, subflow_req->token,
+		 subflow_req->idsn);
+
+	token = subflow_req->token;
+	bucket = token_bucket(token);
+	spin_lock_bh(&bucket->lock);
+	if (__token_bucket_busy(bucket, token)) {
+		spin_unlock_bh(&bucket->lock);
+		if (!--retries)
+			return -EBUSY;
+		goto again;
 	}
 
-	err = radix_tree_insert(&token_req_tree,
-				subflow_req->token, &token_used);
-	spin_unlock_bh(&token_tree_lock);
-	return err;
+	hlist_nulls_add_head_rcu(&subflow_req->token_node, &bucket->req_chain);
+	bucket->chain_len++;
+	spin_unlock_bh(&bucket->lock);
+	return 0;
 }
 
 /**
@@ -97,48 +144,56 @@ int mptcp_token_new_request(struct request_sock *req)
 int mptcp_token_new_connect(struct sock *sk)
 {
 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
-	struct sock *mptcp_sock = subflow->conn;
-	int err;
+	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
+	int retries = TOKEN_MAX_RETRIES;
+	struct token_bucket *bucket;
 
-	while (1) {
-		u32 token;
+	pr_debug("ssk=%p, local_key=%llu, token=%u, idsn=%llu\n",
+		 sk, subflow->local_key, subflow->token, subflow->idsn);
 
-		mptcp_crypto_key_gen_sha(&subflow->local_key, &subflow->token,
-					 &subflow->idsn);
+again:
+	mptcp_crypto_key_gen_sha(&subflow->local_key, &subflow->token,
+				 &subflow->idsn);
 
-		pr_debug("ssk=%p, local_key=%llu, token=%u, idsn=%llu\n",
-			 sk, subflow->local_key, subflow->token, subflow->idsn);
-
-		token = subflow->token;
-		spin_lock_bh(&token_tree_lock);
-		if (!radix_tree_lookup(&token_req_tree, token) &&
-		    !radix_tree_lookup(&token_tree, token))
-			break;
-		spin_unlock_bh(&token_tree_lock);
+	bucket = token_bucket(subflow->token);
+	spin_lock_bh(&bucket->lock);
+	if (__token_bucket_busy(bucket, subflow->token)) {
+		spin_unlock_bh(&bucket->lock);
+		if (!--retries)
+			return -EBUSY;
+		goto again;
 	}
-	err = radix_tree_insert(&token_tree, subflow->token, mptcp_sock);
-	spin_unlock_bh(&token_tree_lock);
 
-	return err;
+	WRITE_ONCE(msk->token, subflow->token);
+	__sk_nulls_add_node_rcu((struct sock *)msk, &bucket->msk_chain);
+	bucket->chain_len++;
+	spin_unlock_bh(&bucket->lock);
+	return 0;
 }
 
 /**
- * mptcp_token_new_accept - insert token for later processing
- * @token: the token to insert to the tree
- * @conn: the just cloned socket linked to the new connection
+ * mptcp_token_accept - replace a req sk with full sock in token hash
+ * @req: the request socket to be removed
+ * @msk: the just cloned socket linked to the new connection
  *
  * Called when a SYN packet creates a new logical connection, i.e.
  * is not a join request.
  */
-int mptcp_token_new_accept(u32 token, struct sock *conn)
+void mptcp_token_accept(struct mptcp_subflow_request_sock *req,
+			struct mptcp_sock *msk)
 {
-	int err;
+	struct mptcp_subflow_request_sock *pos;
+	struct token_bucket *bucket;
 
-	spin_lock_bh(&token_tree_lock);
-	err = radix_tree_insert(&token_tree, token, conn);
-	spin_unlock_bh(&token_tree_lock);
+	bucket = token_bucket(req->token);
+	spin_lock_bh(&bucket->lock);
 
-	return err;
+	/* pedantic lookup check for the moved token */
+	pos = __token_lookup_req(bucket, req->token);
+	if (!WARN_ON_ONCE(pos != req))
+		hlist_nulls_del_init_rcu(&req->token_node);
+	__sk_nulls_add_node_rcu((struct sock *)msk, &bucket->msk_chain);
+	spin_unlock_bh(&bucket->lock);
 }
 
 /**
@@ -152,45 +207,112 @@ int mptcp_token_new_accept(u32 token, struct sock *conn)
  */
 struct mptcp_sock *mptcp_token_get_sock(u32 token)
 {
-	struct sock *conn;
-
-	spin_lock_bh(&token_tree_lock);
-	conn = radix_tree_lookup(&token_tree, token);
-	if (conn) {
-		/* token still reserved? */
-		if (conn == (struct sock *)&token_used)
-			conn = NULL;
-		else
-			sock_hold(conn);
+	struct hlist_nulls_node *pos;
+	struct token_bucket *bucket;
+	struct mptcp_sock *msk;
+	struct sock *sk;
+
+	rcu_read_lock();
+	bucket = token_bucket(token);
+
+again:
+	sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) {
+		msk = mptcp_sk(sk);
+		if (READ_ONCE(msk->token) != token)
+			continue;
+		if (!refcount_inc_not_zero(&sk->sk_refcnt))
+			goto not_found;
+		if (READ_ONCE(msk->token) != token) {
+			sock_put(sk);
+			goto again;
+		}
+		goto found;
 	}
-	spin_unlock_bh(&token_tree_lock);
+	if (get_nulls_value(pos) != (token & token_mask))
+		goto again;
 
-	return mptcp_sk(conn);
+not_found:
+	msk = NULL;
+
+found:
+	rcu_read_unlock();
+	return msk;
 }
 
 /**
  * mptcp_token_destroy_request - remove mptcp connection/token
- * @token: token of mptcp connection to remove
+ * @req: mptcp request socket dropping the token
  *
- * Remove not-yet-fully-established incoming connection identified
- * by @token.
+ * Remove the token associated to @req.
  */
-void mptcp_token_destroy_request(u32 token)
+void mptcp_token_destroy_request(struct request_sock *req)
 {
-	spin_lock_bh(&token_tree_lock);
-	radix_tree_delete(&token_req_tree, token);
-	spin_unlock_bh(&token_tree_lock);
+	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
+	struct mptcp_subflow_request_sock *pos;
+	struct token_bucket *bucket;
+
+	if (hlist_nulls_unhashed(&subflow_req->token_node))
+		return;
+
+	bucket = token_bucket(subflow_req->token);
+	spin_lock_bh(&bucket->lock);
+	pos = __token_lookup_req(bucket, subflow_req->token);
+	if (!WARN_ON_ONCE(pos != subflow_req)) {
+		hlist_nulls_del_init_rcu(&pos->token_node);
+		bucket->chain_len--;
+	}
+	spin_unlock_bh(&bucket->lock);
 }
 
 /**
  * mptcp_token_destroy - remove mptcp connection/token
- * @token: token of mptcp connection to remove
+ * @msk: mptcp connection dropping the token
  *
- * Remove the connection identified by @token.
+ * Remove the token associated to @msk
  */
-void mptcp_token_destroy(u32 token)
+void mptcp_token_destroy(struct mptcp_sock *msk)
 {
-	spin_lock_bh(&token_tree_lock);
-	radix_tree_delete(&token_tree, token);
-	spin_unlock_bh(&token_tree_lock);
+	struct token_bucket *bucket;
+	struct mptcp_sock *pos;
+
+	if (sk_unhashed((struct sock *)msk))
+		return;
+
+	bucket = token_bucket(msk->token);
+	spin_lock_bh(&bucket->lock);
+	pos = __token_lookup_msk(bucket, msk->token);
+	if (!WARN_ON_ONCE(pos != msk)) {
+		__sk_nulls_del_node_init_rcu((struct sock *)pos);
+		bucket->chain_len--;
+	}
+	spin_unlock_bh(&bucket->lock);
+}
+
+void __init mptcp_token_init(void)
+{
+	int i;
+
+	token_hash = alloc_large_system_hash("MPTCP token",
+					     sizeof(struct token_bucket),
+					     0,
+					     20,/* one slot per 1MB of memory */
+					     0,
+					     NULL,
+					     &token_mask,
+					     0,
+					     64 * 1024);
+	for (i = 0; i < token_mask + 1; ++i) {
+		INIT_HLIST_NULLS_HEAD(&token_hash[i].req_chain, i);
+		INIT_HLIST_NULLS_HEAD(&token_hash[i].msk_chain, i);
+		spin_lock_init(&token_hash[i].lock);
+	}
 }
+
+#if IS_MODULE(CONFIG_MPTCP_KUNIT_TESTS)
+EXPORT_SYMBOL_GPL(mptcp_token_new_request);
+EXPORT_SYMBOL_GPL(mptcp_token_new_connect);
+EXPORT_SYMBOL_GPL(mptcp_token_accept);
+EXPORT_SYMBOL_GPL(mptcp_token_get_sock);
+EXPORT_SYMBOL_GPL(mptcp_token_destroy_request);
+EXPORT_SYMBOL_GPL(mptcp_token_destroy);
+#endif
diff --git a/net/mptcp/token_test.c b/net/mptcp/token_test.c
new file mode 100644
index 000000000000..e1bd6f0a0676
--- /dev/null
+++ b/net/mptcp/token_test.c
@@ -0,0 +1,140 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <kunit/test.h>
+
+#include "protocol.h"
+
+static struct mptcp_subflow_request_sock *build_req_sock(struct kunit *test)
+{
+	struct mptcp_subflow_request_sock *req;
+
+	req = kunit_kzalloc(test, sizeof(struct mptcp_subflow_request_sock),
+			    GFP_USER);
+	KUNIT_EXPECT_NOT_ERR_OR_NULL(test, req);
+	mptcp_token_init_request((struct request_sock *)req);
+	return req;
+}
+
+static void mptcp_token_test_req_basic(struct kunit *test)
+{
+	struct mptcp_subflow_request_sock *req = build_req_sock(test);
+	struct mptcp_sock *null_msk = NULL;
+
+	KUNIT_ASSERT_EQ(test, 0,
+			mptcp_token_new_request((struct request_sock *)req));
+	KUNIT_EXPECT_NE(test, 0, (int)req->token);
+	KUNIT_EXPECT_PTR_EQ(test, null_msk, mptcp_token_get_sock(req->token));
+
+	/* cleanup */
+	mptcp_token_destroy_request((struct request_sock *)req);
+}
+
+static struct inet_connection_sock *build_icsk(struct kunit *test)
+{
+	struct inet_connection_sock *icsk;
+
+	icsk = kunit_kzalloc(test, sizeof(struct inet_connection_sock),
+			     GFP_USER);
+	KUNIT_EXPECT_NOT_ERR_OR_NULL(test, icsk);
+	return icsk;
+}
+
+static struct mptcp_subflow_context *build_ctx(struct kunit *test)
+{
+	struct mptcp_subflow_context *ctx;
+
+	ctx = kunit_kzalloc(test, sizeof(struct mptcp_subflow_context),
+			    GFP_USER);
+	KUNIT_EXPECT_NOT_ERR_OR_NULL(test, ctx);
+	return ctx;
+}
+
+static struct mptcp_sock *build_msk(struct kunit *test)
+{
+	struct mptcp_sock *msk;
+
+	msk = kunit_kzalloc(test, sizeof(struct mptcp_sock), GFP_USER);
+	KUNIT_EXPECT_NOT_ERR_OR_NULL(test, msk);
+	refcount_set(&((struct sock *)msk)->sk_refcnt, 1);
+	return msk;
+}
+
+static void mptcp_token_test_msk_basic(struct kunit *test)
+{
+	struct inet_connection_sock *icsk = build_icsk(test);
+	struct mptcp_subflow_context *ctx = build_ctx(test);
+	struct mptcp_sock *msk = build_msk(test);
+	struct mptcp_sock *null_msk = NULL;
+	struct sock *sk;
+
+	rcu_assign_pointer(icsk->icsk_ulp_data, ctx);
+	ctx->conn = (struct sock *)msk;
+	sk = (struct sock *)msk;
+
+	KUNIT_ASSERT_EQ(test, 0,
+			mptcp_token_new_connect((struct sock *)icsk));
+	KUNIT_EXPECT_NE(test, 0, (int)ctx->token);
+	KUNIT_EXPECT_EQ(test, ctx->token, msk->token);
+	KUNIT_EXPECT_PTR_EQ(test, msk, mptcp_token_get_sock(ctx->token));
+	KUNIT_EXPECT_EQ(test, 2, (int)refcount_read(&sk->sk_refcnt));
+
+	mptcp_token_destroy(msk);
+	KUNIT_EXPECT_PTR_EQ(test, null_msk, mptcp_token_get_sock(ctx->token));
+}
+
+static void mptcp_token_test_accept(struct kunit *test)
+{
+	struct mptcp_subflow_request_sock *req = build_req_sock(test);
+	struct mptcp_sock *msk = build_msk(test);
+
+	KUNIT_ASSERT_EQ(test, 0,
+			mptcp_token_new_request((struct request_sock *)req));
+	msk->token = req->token;
+	mptcp_token_accept(req, msk);
+	KUNIT_EXPECT_PTR_EQ(test, msk, mptcp_token_get_sock(msk->token));
+
+	/* this is now a no-op */
+	mptcp_token_destroy_request((struct request_sock *)req);
+	KUNIT_EXPECT_PTR_EQ(test, msk, mptcp_token_get_sock(msk->token));
+
+	/* cleanup */
+	mptcp_token_destroy(msk);
+}
+
+static void mptcp_token_test_destroyed(struct kunit *test)
+{
+	struct mptcp_subflow_request_sock *req = build_req_sock(test);
+	struct mptcp_sock *msk = build_msk(test);
+	struct mptcp_sock *null_msk = NULL;
+	struct sock *sk;
+
+	sk = (struct sock *)msk;
+
+	KUNIT_ASSERT_EQ(test, 0,
+			mptcp_token_new_request((struct request_sock *)req));
+	msk->token = req->token;
+	mptcp_token_accept(req, msk);
+
+	/* simulate race on removal */
+	refcount_set(&sk->sk_refcnt, 0);
+	KUNIT_EXPECT_PTR_EQ(test, null_msk, mptcp_token_get_sock(msk->token));
+
+	/* cleanup */
+	mptcp_token_destroy(msk);
+}
+
+static struct kunit_case mptcp_token_test_cases[] = {
+	KUNIT_CASE(mptcp_token_test_req_basic),
+	KUNIT_CASE(mptcp_token_test_msk_basic),
+	KUNIT_CASE(mptcp_token_test_accept),
+	KUNIT_CASE(mptcp_token_test_destroyed),
+	{}
+};
+
+static struct kunit_suite mptcp_token_suite = {
+	.name = "mptcp-token",
+	.test_cases = mptcp_token_test_cases,
+};
+
+kunit_test_suite(mptcp_token_suite);
+
+MODULE_LICENSE("GPL");