net: psp: add socket security association code

Add the ability to install PSP Rx and Tx crypto keys on TCP
connections. Netlink ops are provided for both operations.
Rx side combines allocating a new Rx key and installing it
on the socket. Theoretically these are separate actions,
but in practice they will always be used one after the
other. We can add distinct "alloc" and "install" ops later.

Reviewed-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Co-developed-by: Daniel Zahka <daniel.zahka@gmail.com>
Signed-off-by: Daniel Zahka <daniel.zahka@gmail.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250917000954.859376-9-daniel.zahka@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

8 files changed, 601 insertions, 2 deletions

diff --git a/net/psp/Kconfig b/net/psp/Kconfig
index 5e3908a40945..a7d24691a7e1 100644
--- a/net/psp/Kconfig
+++ b/net/psp/Kconfig
@@ -6,6 +6,7 @@ config INET_PSP
 	bool "PSP Security Protocol support"
 	depends on INET
 	select SKB_DECRYPTED
+	select SOCK_VALIDATE_XMIT
 	help
 	Enable kernel support for the PSP protocol.
 	For more information see:
diff --git a/net/psp/Makefile b/net/psp/Makefile
index 41b51d06e560..eb5ff3c5bfb2 100644
--- a/net/psp/Makefile
+++ b/net/psp/Makefile
@@ -2,4 +2,4 @@
 
 obj-$(CONFIG_INET_PSP) += psp.o
 
-psp-y := psp_main.o psp_nl.o psp-nl-gen.o
+psp-y := psp_main.o psp_nl.o psp_sock.o psp-nl-gen.o
diff --git a/net/psp/psp-nl-gen.c b/net/psp/psp-nl-gen.c
index 7f49577ac72f..9fdd6f831803 100644
--- a/net/psp/psp-nl-gen.c
+++ b/net/psp/psp-nl-gen.c
@@ -10,6 +10,12 @@
 
 #include <uapi/linux/psp.h>
 
+/* Common nested types */
+const struct nla_policy psp_keys_nl_policy[PSP_A_KEYS_SPI + 1] = {
+	[PSP_A_KEYS_KEY] = { .type = NLA_BINARY, },
+	[PSP_A_KEYS_SPI] = { .type = NLA_U32, },
+};
+
 /* PSP_CMD_DEV_GET - do */
 static const struct nla_policy psp_dev_get_nl_policy[PSP_A_DEV_ID + 1] = {
 	[PSP_A_DEV_ID] = NLA_POLICY_MIN(NLA_U32, 1),
@@ -26,6 +32,21 @@ static const struct nla_policy psp_key_rotate_nl_policy[PSP_A_DEV_ID + 1] = {
 	[PSP_A_DEV_ID] = NLA_POLICY_MIN(NLA_U32, 1),
 };
 
+/* PSP_CMD_RX_ASSOC - do */
+static const struct nla_policy psp_rx_assoc_nl_policy[PSP_A_ASSOC_SOCK_FD + 1] = {
+	[PSP_A_ASSOC_DEV_ID] = NLA_POLICY_MIN(NLA_U32, 1),
+	[PSP_A_ASSOC_VERSION] = NLA_POLICY_MAX(NLA_U32, 3),
+	[PSP_A_ASSOC_SOCK_FD] = { .type = NLA_U32, },
+};
+
+/* PSP_CMD_TX_ASSOC - do */
+static const struct nla_policy psp_tx_assoc_nl_policy[PSP_A_ASSOC_SOCK_FD + 1] = {
+	[PSP_A_ASSOC_DEV_ID] = NLA_POLICY_MIN(NLA_U32, 1),
+	[PSP_A_ASSOC_VERSION] = NLA_POLICY_MAX(NLA_U32, 3),
+	[PSP_A_ASSOC_TX_KEY] = NLA_POLICY_NESTED(psp_keys_nl_policy),
+	[PSP_A_ASSOC_SOCK_FD] = { .type = NLA_U32, },
+};
+
 /* Ops table for psp */
 static const struct genl_split_ops psp_nl_ops[] = {
 	{
@@ -60,6 +81,24 @@ static const struct genl_split_ops psp_nl_ops[] = {
 		.maxattr	= PSP_A_DEV_ID,
 		.flags		= GENL_CMD_CAP_DO,
 	},
+	{
+		.cmd		= PSP_CMD_RX_ASSOC,
+		.pre_doit	= psp_assoc_device_get_locked,
+		.doit		= psp_nl_rx_assoc_doit,
+		.post_doit	= psp_device_unlock,
+		.policy		= psp_rx_assoc_nl_policy,
+		.maxattr	= PSP_A_ASSOC_SOCK_FD,
+		.flags		= GENL_CMD_CAP_DO,
+	},
+	{
+		.cmd		= PSP_CMD_TX_ASSOC,
+		.pre_doit	= psp_assoc_device_get_locked,
+		.doit		= psp_nl_tx_assoc_doit,
+		.post_doit	= psp_device_unlock,
+		.policy		= psp_tx_assoc_nl_policy,
+		.maxattr	= PSP_A_ASSOC_SOCK_FD,
+		.flags		= GENL_CMD_CAP_DO,
+	},
 };
 
 static const struct genl_multicast_group psp_nl_mcgrps[] = {
diff --git a/net/psp/psp-nl-gen.h b/net/psp/psp-nl-gen.h
index 00a2d4ec59e4..25268ed11fb5 100644
--- a/net/psp/psp-nl-gen.h
+++ b/net/psp/psp-nl-gen.h
@@ -11,8 +11,13 @@
 
 #include <uapi/linux/psp.h>
 
+/* Common nested types */
+extern const struct nla_policy psp_keys_nl_policy[PSP_A_KEYS_SPI + 1];
+
 int psp_device_get_locked(const struct genl_split_ops *ops,
 			  struct sk_buff *skb, struct genl_info *info);
+int psp_assoc_device_get_locked(const struct genl_split_ops *ops,
+				struct sk_buff *skb, struct genl_info *info);
 void
 psp_device_unlock(const struct genl_split_ops *ops, struct sk_buff *skb,
 		  struct genl_info *info);
@@ -21,6 +26,8 @@ int psp_nl_dev_get_doit(struct sk_buff *skb, struct genl_info *info);
 int psp_nl_dev_get_dumpit(struct sk_buff *skb, struct netlink_callback *cb);
 int psp_nl_dev_set_doit(struct sk_buff *skb, struct genl_info *info);
 int psp_nl_key_rotate_doit(struct sk_buff *skb, struct genl_info *info);
+int psp_nl_rx_assoc_doit(struct sk_buff *skb, struct genl_info *info);
+int psp_nl_tx_assoc_doit(struct sk_buff *skb, struct genl_info *info);
 
 enum {
 	PSP_NLGRP_MGMT,
diff --git a/net/psp/psp.h b/net/psp/psp.h
index 94d0cc31a61f..defd3e3fd5e7 100644
--- a/net/psp/psp.h
+++ b/net/psp/psp.h
@@ -4,6 +4,7 @@
 #define __PSP_PSP_H
 
 #include <linux/list.h>
+#include <linux/lockdep.h>
 #include <linux/mutex.h>
 #include <net/netns/generic.h>
 #include <net/psp.h>
@@ -17,15 +18,36 @@ int psp_dev_check_access(struct psp_dev *psd, struct net *net);
 
 void psp_nl_notify_dev(struct psp_dev *psd, u32 cmd);
 
+struct psp_assoc *psp_assoc_create(struct psp_dev *psd);
+struct psp_dev *psp_dev_get_for_sock(struct sock *sk);
+void psp_dev_tx_key_del(struct psp_dev *psd, struct psp_assoc *pas);
+int psp_sock_assoc_set_rx(struct sock *sk, struct psp_assoc *pas,
+			  struct psp_key_parsed *key,
+			  struct netlink_ext_ack *extack);
+int psp_sock_assoc_set_tx(struct sock *sk, struct psp_dev *psd,
+			  u32 version, struct psp_key_parsed *key,
+			  struct netlink_ext_ack *extack);
+
 static inline void psp_dev_get(struct psp_dev *psd)
 {
 	refcount_inc(&psd->refcnt);
 }
 
+static inline bool psp_dev_tryget(struct psp_dev *psd)
+{
+	return refcount_inc_not_zero(&psd->refcnt);
+}
+
 static inline void psp_dev_put(struct psp_dev *psd)
 {
 	if (refcount_dec_and_test(&psd->refcnt))
 		psp_dev_destroy(psd);
 }
 
+static inline bool psp_dev_is_registered(struct psp_dev *psd)
+{
+	lockdep_assert_held(&psd->lock);
+	return !!psd->ops;
+}
+
 #endif /* __PSP_PSP_H */
diff --git a/net/psp/psp_main.c b/net/psp/psp_main.c
index f60155493afc..a1ae3c8920c3 100644
--- a/net/psp/psp_main.c
+++ b/net/psp/psp_main.c
@@ -55,7 +55,10 @@ psp_dev_create(struct net_device *netdev,
 
 	if (WARN_ON(!psd_caps->versions ||
 		    !psd_ops->set_config ||
-		    !psd_ops->key_rotate))
+		    !psd_ops->key_rotate ||
+		    !psd_ops->rx_spi_alloc ||
+		    !psd_ops->tx_key_add ||
+		    !psd_ops->tx_key_del))
 		return ERR_PTR(-EINVAL);
 
 	psd = kzalloc(sizeof(*psd), GFP_KERNEL);
@@ -68,6 +71,7 @@ psp_dev_create(struct net_device *netdev,
 	psd->drv_priv = priv_ptr;
 
 	mutex_init(&psd->lock);
+	INIT_LIST_HEAD(&psd->active_assocs);
 	refcount_set(&psd->refcnt, 1);
 
 	mutex_lock(&psp_devs_lock);
@@ -107,6 +111,8 @@ void psp_dev_destroy(struct psp_dev *psd)
  */
 void psp_dev_unregister(struct psp_dev *psd)
 {
+	struct psp_assoc *pas, *next;
+
 	mutex_lock(&psp_devs_lock);
 	mutex_lock(&psd->lock);
 
@@ -119,6 +125,9 @@ void psp_dev_unregister(struct psp_dev *psd)
 	xa_store(&psp_devs, psd->id, NULL, GFP_KERNEL);
 	mutex_unlock(&psp_devs_lock);
 
+	list_for_each_entry_safe(pas, next, &psd->active_assocs, assocs_list)
+		psp_dev_tx_key_del(psd, pas);
+
 	rcu_assign_pointer(psd->main_netdev->psp_dev, NULL);
 
 	psd->ops = NULL;
@@ -130,6 +139,21 @@ void psp_dev_unregister(struct psp_dev *psd)
 }
 EXPORT_SYMBOL(psp_dev_unregister);
 
+unsigned int psp_key_size(u32 version)
+{
+	switch (version) {
+	case PSP_VERSION_HDR0_AES_GCM_128:
+	case PSP_VERSION_HDR0_AES_GMAC_128:
+		return 16;
+	case PSP_VERSION_HDR0_AES_GCM_256:
+	case PSP_VERSION_HDR0_AES_GMAC_256:
+		return 32;
+	default:
+		return 0;
+	}
+}
+EXPORT_SYMBOL(psp_key_size);
+
 static int __init psp_init(void)
 {
 	mutex_init(&psp_devs_lock);
diff --git a/net/psp/psp_nl.c b/net/psp/psp_nl.c
index 75f2702c1029..1b1d08fce637 100644
--- a/net/psp/psp_nl.c
+++ b/net/psp/psp_nl.c
@@ -79,9 +79,12 @@ void
 psp_device_unlock(const struct genl_split_ops *ops, struct sk_buff *skb,
 		  struct genl_info *info)
 {
+	struct socket *socket = info->user_ptr[1];
 	struct psp_dev *psd = info->user_ptr[0];
 
 	mutex_unlock(&psd->lock);
+	if (socket)
+		sockfd_put(socket);
 }
 
 static int
@@ -261,3 +264,232 @@ err_free_rsp:
 	nlmsg_free(rsp);
 	return err;
 }
+
+/* Key etc. */
+
+int psp_assoc_device_get_locked(const struct genl_split_ops *ops,
+				struct sk_buff *skb, struct genl_info *info)
+{
+	struct socket *socket;
+	struct psp_dev *psd;
+	struct nlattr *id;
+	int fd, err;
+
+	if (GENL_REQ_ATTR_CHECK(info, PSP_A_ASSOC_SOCK_FD))
+		return -EINVAL;
+
+	fd = nla_get_u32(info->attrs[PSP_A_ASSOC_SOCK_FD]);
+	socket = sockfd_lookup(fd, &err);
+	if (!socket)
+		return err;
+
+	if (!sk_is_tcp(socket->sk)) {
+		NL_SET_ERR_MSG_ATTR(info->extack,
+				    info->attrs[PSP_A_ASSOC_SOCK_FD],
+				    "Unsupported socket family and type");
+		err = -EOPNOTSUPP;
+		goto err_sock_put;
+	}
+
+	psd = psp_dev_get_for_sock(socket->sk);
+	if (psd) {
+		err = psp_dev_check_access(psd, genl_info_net(info));
+		if (err) {
+			psp_dev_put(psd);
+			psd = NULL;
+		}
+	}
+
+	if (!psd && GENL_REQ_ATTR_CHECK(info, PSP_A_ASSOC_DEV_ID)) {
+		err = -EINVAL;
+		goto err_sock_put;
+	}
+
+	id = info->attrs[PSP_A_ASSOC_DEV_ID];
+	if (psd) {
+		mutex_lock(&psd->lock);
+		if (id && psd->id != nla_get_u32(id)) {
+			mutex_unlock(&psd->lock);
+			NL_SET_ERR_MSG_ATTR(info->extack, id,
+					    "Device id vs socket mismatch");
+			err = -EINVAL;
+			goto err_psd_put;
+		}
+
+		psp_dev_put(psd);
+	} else {
+		psd = psp_device_get_and_lock(genl_info_net(info), id);
+		if (IS_ERR(psd)) {
+			err = PTR_ERR(psd);
+			goto err_sock_put;
+		}
+	}
+
+	info->user_ptr[0] = psd;
+	info->user_ptr[1] = socket;
+
+	return 0;
+
+err_psd_put:
+	psp_dev_put(psd);
+err_sock_put:
+	sockfd_put(socket);
+	return err;
+}
+
+static int
+psp_nl_parse_key(struct genl_info *info, u32 attr, struct psp_key_parsed *key,
+		 unsigned int key_sz)
+{
+	struct nlattr *nest = info->attrs[attr];
+	struct nlattr *tb[PSP_A_KEYS_SPI + 1];
+	u32 spi;
+	int err;
+
+	err = nla_parse_nested(tb, ARRAY_SIZE(tb) - 1, nest,
+			       psp_keys_nl_policy, info->extack);
+	if (err)
+		return err;
+
+	if (NL_REQ_ATTR_CHECK(info->extack, nest, tb, PSP_A_KEYS_KEY) ||
+	    NL_REQ_ATTR_CHECK(info->extack, nest, tb, PSP_A_KEYS_SPI))
+		return -EINVAL;
+
+	if (nla_len(tb[PSP_A_KEYS_KEY]) != key_sz) {
+		NL_SET_ERR_MSG_ATTR(info->extack, tb[PSP_A_KEYS_KEY],
+				    "incorrect key length");
+		return -EINVAL;
+	}
+
+	spi = nla_get_u32(tb[PSP_A_KEYS_SPI]);
+	if (!(spi & PSP_SPI_KEY_ID)) {
+		NL_SET_ERR_MSG_ATTR(info->extack, tb[PSP_A_KEYS_KEY],
+				    "invalid SPI: lower 31b must be non-zero");
+		return -EINVAL;
+	}
+
+	key->spi = cpu_to_be32(spi);
+	memcpy(key->key, nla_data(tb[PSP_A_KEYS_KEY]), key_sz);
+
+	return 0;
+}
+
+static int
+psp_nl_put_key(struct sk_buff *skb, u32 attr, u32 version,
+	       struct psp_key_parsed *key)
+{
+	int key_sz = psp_key_size(version);
+	void *nest;
+
+	nest = nla_nest_start(skb, attr);
+
+	if (nla_put_u32(skb, PSP_A_KEYS_SPI, be32_to_cpu(key->spi)) ||
+	    nla_put(skb, PSP_A_KEYS_KEY, key_sz, key->key)) {
+		nla_nest_cancel(skb, nest);
+		return -EMSGSIZE;
+	}
+
+	nla_nest_end(skb, nest);
+
+	return 0;
+}
+
+int psp_nl_rx_assoc_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	struct socket *socket = info->user_ptr[1];
+	struct psp_dev *psd = info->user_ptr[0];
+	struct psp_key_parsed key;
+	struct psp_assoc *pas;
+	struct sk_buff *rsp;
+	u32 version;
+	int err;
+
+	if (GENL_REQ_ATTR_CHECK(info, PSP_A_ASSOC_VERSION))
+		return -EINVAL;
+
+	version = nla_get_u32(info->attrs[PSP_A_ASSOC_VERSION]);
+	if (!(psd->caps->versions & (1 << version))) {
+		NL_SET_BAD_ATTR(info->extack, info->attrs[PSP_A_ASSOC_VERSION]);
+		return -EOPNOTSUPP;
+	}
+
+	rsp = psp_nl_reply_new(info);
+	if (!rsp)
+		return -ENOMEM;
+
+	pas = psp_assoc_create(psd);
+	if (!pas) {
+		err = -ENOMEM;
+		goto err_free_rsp;
+	}
+	pas->version = version;
+
+	err = psd->ops->rx_spi_alloc(psd, version, &key, info->extack);
+	if (err)
+		goto err_free_pas;
+
+	if (nla_put_u32(rsp, PSP_A_ASSOC_DEV_ID, psd->id) ||
+	    psp_nl_put_key(rsp, PSP_A_ASSOC_RX_KEY, version, &key)) {
+		err = -EMSGSIZE;
+		goto err_free_pas;
+	}
+
+	err = psp_sock_assoc_set_rx(socket->sk, pas, &key, info->extack);
+	if (err) {
+		NL_SET_BAD_ATTR(info->extack, info->attrs[PSP_A_ASSOC_SOCK_FD]);
+		goto err_free_pas;
+	}
+	psp_assoc_put(pas);
+
+	return psp_nl_reply_send(rsp, info);
+
+err_free_pas:
+	psp_assoc_put(pas);
+err_free_rsp:
+	nlmsg_free(rsp);
+	return err;
+}
+
+int psp_nl_tx_assoc_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	struct socket *socket = info->user_ptr[1];
+	struct psp_dev *psd = info->user_ptr[0];
+	struct psp_key_parsed key;
+	struct sk_buff *rsp;
+	unsigned int key_sz;
+	u32 version;
+	int err;
+
+	if (GENL_REQ_ATTR_CHECK(info, PSP_A_ASSOC_VERSION) ||
+	    GENL_REQ_ATTR_CHECK(info, PSP_A_ASSOC_TX_KEY))
+		return -EINVAL;
+
+	version = nla_get_u32(info->attrs[PSP_A_ASSOC_VERSION]);
+	if (!(psd->caps->versions & (1 << version))) {
+		NL_SET_BAD_ATTR(info->extack, info->attrs[PSP_A_ASSOC_VERSION]);
+		return -EOPNOTSUPP;
+	}
+
+	key_sz = psp_key_size(version);
+	if (!key_sz)
+		return -EINVAL;
+
+	err = psp_nl_parse_key(info, PSP_A_ASSOC_TX_KEY, &key, key_sz);
+	if (err < 0)
+		return err;
+
+	rsp = psp_nl_reply_new(info);
+	if (!rsp)
+		return -ENOMEM;
+
+	err = psp_sock_assoc_set_tx(socket->sk, psd, version, &key,
+				    info->extack);
+	if (err)
+		goto err_free_msg;
+
+	return psp_nl_reply_send(rsp, info);
+
+err_free_msg:
+	nlmsg_free(rsp);
+	return err;
+}
diff --git a/net/psp/psp_sock.c b/net/psp/psp_sock.c
new file mode 100644
index 000000000000..8ebccee94593
--- /dev/null
+++ b/net/psp/psp_sock.c
@@ -0,0 +1,274 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/file.h>
+#include <linux/net.h>
+#include <linux/rcupdate.h>
+#include <linux/tcp.h>
+
+#include <net/ip.h>
+#include <net/psp.h>
+#include "psp.h"
+
+struct psp_dev *psp_dev_get_for_sock(struct sock *sk)
+{
+	struct dst_entry *dst;
+	struct psp_dev *psd;
+
+	dst = sk_dst_get(sk);
+	if (!dst)
+		return NULL;
+
+	rcu_read_lock();
+	psd = rcu_dereference(dst->dev->psp_dev);
+	if (psd && !psp_dev_tryget(psd))
+		psd = NULL;
+	rcu_read_unlock();
+
+	dst_release(dst);
+
+	return psd;
+}
+
+static struct sk_buff *
+psp_validate_xmit(struct sock *sk, struct net_device *dev, struct sk_buff *skb)
+{
+	struct psp_assoc *pas;
+	bool good;
+
+	rcu_read_lock();
+	pas = psp_skb_get_assoc_rcu(skb);
+	good = !pas || rcu_access_pointer(dev->psp_dev) == pas->psd;
+	rcu_read_unlock();
+	if (!good) {
+		kfree_skb_reason(skb, SKB_DROP_REASON_PSP_OUTPUT);
+		return NULL;
+	}
+
+	return skb;
+}
+
+struct psp_assoc *psp_assoc_create(struct psp_dev *psd)
+{
+	struct psp_assoc *pas;
+
+	lockdep_assert_held(&psd->lock);
+
+	pas = kzalloc(struct_size(pas, drv_data, psd->caps->assoc_drv_spc),
+		      GFP_KERNEL_ACCOUNT);
+	if (!pas)
+		return NULL;
+
+	pas->psd = psd;
+	pas->dev_id = psd->id;
+	psp_dev_get(psd);
+	refcount_set(&pas->refcnt, 1);
+
+	list_add_tail(&pas->assocs_list, &psd->active_assocs);
+
+	return pas;
+}
+
+static struct psp_assoc *psp_assoc_dummy(struct psp_assoc *pas)
+{
+	struct psp_dev *psd = pas->psd;
+	size_t sz;
+
+	lockdep_assert_held(&psd->lock);
+
+	sz = struct_size(pas, drv_data, psd->caps->assoc_drv_spc);
+	return kmemdup(pas, sz, GFP_KERNEL);
+}
+
+static int psp_dev_tx_key_add(struct psp_dev *psd, struct psp_assoc *pas,
+			      struct netlink_ext_ack *extack)
+{
+	return psd->ops->tx_key_add(psd, pas, extack);
+}
+
+void psp_dev_tx_key_del(struct psp_dev *psd, struct psp_assoc *pas)
+{
+	if (pas->tx.spi)
+		psd->ops->tx_key_del(psd, pas);
+	list_del(&pas->assocs_list);
+}
+
+static void psp_assoc_free(struct work_struct *work)
+{
+	struct psp_assoc *pas = container_of(work, struct psp_assoc, work);
+	struct psp_dev *psd = pas->psd;
+
+	mutex_lock(&psd->lock);
+	if (psd->ops)
+		psp_dev_tx_key_del(psd, pas);
+	mutex_unlock(&psd->lock);
+	psp_dev_put(psd);
+	kfree(pas);
+}
+
+static void psp_assoc_free_queue(struct rcu_head *head)
+{
+	struct psp_assoc *pas = container_of(head, struct psp_assoc, rcu);
+
+	INIT_WORK(&pas->work, psp_assoc_free);
+	schedule_work(&pas->work);
+}
+
+/**
+ * psp_assoc_put() - release a reference on a PSP association
+ * @pas: association to release
+ */
+void psp_assoc_put(struct psp_assoc *pas)
+{
+	if (pas && refcount_dec_and_test(&pas->refcnt))
+		call_rcu(&pas->rcu, psp_assoc_free_queue);
+}
+
+void psp_sk_assoc_free(struct sock *sk)
+{
+	struct psp_assoc *pas = rcu_dereference_protected(sk->psp_assoc, 1);
+
+	rcu_assign_pointer(sk->psp_assoc, NULL);
+	psp_assoc_put(pas);
+}
+
+int psp_sock_assoc_set_rx(struct sock *sk, struct psp_assoc *pas,
+			  struct psp_key_parsed *key,
+			  struct netlink_ext_ack *extack)
+{
+	int err;
+
+	memcpy(&pas->rx, key, sizeof(*key));
+
+	lock_sock(sk);
+
+	if (psp_sk_assoc(sk)) {
+		NL_SET_ERR_MSG(extack, "Socket already has PSP state");
+		err = -EBUSY;
+		goto exit_unlock;
+	}
+
+	refcount_inc(&pas->refcnt);
+	rcu_assign_pointer(sk->psp_assoc, pas);
+	err = 0;
+
+exit_unlock:
+	release_sock(sk);
+
+	return err;
+}
+
+static int psp_sock_recv_queue_check(struct sock *sk, struct psp_assoc *pas)
+{
+	struct psp_skb_ext *pse;
+	struct sk_buff *skb;
+
+	skb_rbtree_walk(skb, &tcp_sk(sk)->out_of_order_queue) {
+		pse = skb_ext_find(skb, SKB_EXT_PSP);
+		if (!psp_pse_matches_pas(pse, pas))
+			return -EBUSY;
+	}
+
+	skb_queue_walk(&sk->sk_receive_queue, skb) {
+		pse = skb_ext_find(skb, SKB_EXT_PSP);
+		if (!psp_pse_matches_pas(pse, pas))
+			return -EBUSY;
+	}
+	return 0;
+}
+
+int psp_sock_assoc_set_tx(struct sock *sk, struct psp_dev *psd,
+			  u32 version, struct psp_key_parsed *key,
+			  struct netlink_ext_ack *extack)
+{
+	struct psp_assoc *pas, *dummy;
+	int err;
+
+	lock_sock(sk);
+
+	pas = psp_sk_assoc(sk);
+	if (!pas) {
+		NL_SET_ERR_MSG(extack, "Socket has no Rx key");
+		err = -EINVAL;
+		goto exit_unlock;
+	}
+	if (pas->psd != psd) {
+		NL_SET_ERR_MSG(extack, "Rx key from different device");
+		err = -EINVAL;
+		goto exit_unlock;
+	}
+	if (pas->version != version) {
+		NL_SET_ERR_MSG(extack,
+			       "PSP version mismatch with existing state");
+		err = -EINVAL;
+		goto exit_unlock;
+	}
+	if (pas->tx.spi) {
+		NL_SET_ERR_MSG(extack, "Tx key already set");
+		err = -EBUSY;
+		goto exit_unlock;
+	}
+
+	err = psp_sock_recv_queue_check(sk, pas);
+	if (err) {
+		NL_SET_ERR_MSG(extack, "Socket has incompatible segments already in the recv queue");
+		goto exit_unlock;
+	}
+
+	/* Pass a fake association to drivers to make sure they don't
+	 * try to store pointers to it. For re-keying we'll need to
+	 * re-allocate the assoc structures.
+	 */
+	dummy = psp_assoc_dummy(pas);
+	if (!dummy) {
+		err = -ENOMEM;
+		goto exit_unlock;
+	}
+
+	memcpy(&dummy->tx, key, sizeof(*key));
+	err = psp_dev_tx_key_add(psd, dummy, extack);
+	if (err)
+		goto exit_free_dummy;
+
+	memcpy(pas->drv_data, dummy->drv_data, psd->caps->assoc_drv_spc);
+	memcpy(&pas->tx, key, sizeof(*key));
+
+	WRITE_ONCE(sk->sk_validate_xmit_skb, psp_validate_xmit);
+	tcp_write_collapse_fence(sk);
+	pas->upgrade_seq = tcp_sk(sk)->rcv_nxt;
+
+exit_free_dummy:
+	kfree(dummy);
+exit_unlock:
+	release_sock(sk);
+	return err;
+}
+
+void psp_twsk_init(struct inet_timewait_sock *tw, const struct sock *sk)
+{
+	struct psp_assoc *pas = psp_sk_assoc(sk);
+
+	if (pas)
+		refcount_inc(&pas->refcnt);
+	rcu_assign_pointer(tw->psp_assoc, pas);
+	tw->tw_validate_xmit_skb = psp_validate_xmit;
+}
+
+void psp_twsk_assoc_free(struct inet_timewait_sock *tw)
+{
+	struct psp_assoc *pas = rcu_dereference_protected(tw->psp_assoc, 1);
+
+	rcu_assign_pointer(tw->psp_assoc, NULL);
+	psp_assoc_put(pas);
+}
+
+void psp_reply_set_decrypted(struct sk_buff *skb)
+{
+	struct psp_assoc *pas;
+
+	rcu_read_lock();
+	pas = psp_sk_get_assoc_rcu(skb->sk);
+	if (pas && pas->tx.spi)
+		skb->decrypted = 1;
+	rcu_read_unlock();
+}
+EXPORT_IPV6_MOD_GPL(psp_reply_set_decrypted);