[PATCH ipsec-next v5 8/8] xfrm: add XFRM_MSG_MIGRATE_STATE for single SA migration

Antony Antony
2026-01-27T10:44:29Z

Add a new netlink method to migrate a single xfrm_state.
Unlike the existing migration mechanism (SA + policy), this
supports migrating only the SA and allows changing the reqid.

The reqid is invariant in the old migration.

Signed-off-by: Antony Antony <antony.antony@secunet.com>
---
v1->v2: merged next patch here to fix use uninitialized value
- removed unnecessary inline
- added const when possible

v2->v3: free the skb on the error path

v3->v4: preserve reqid invariant for each state migrated

v4->v5: - set portid, seq in XFRM_MSG_MIGRATE_STATE netlink notification
- rename error label to out for clarity
- add locking and synchronize after cloning
- change some if(x) to if(!x) for clarity
- call __xfrm_state_delete() inside the lock
- return error from xfrm_send_migrate_state() instead of always
returning 0
---
include/net/xfrm.h | 1 +
include/uapi/linux/xfrm.h | 11 +++
net/xfrm/xfrm_policy.c | 1 +
net/xfrm/xfrm_state.c | 8 +-
net/xfrm/xfrm_user.c | 176 ++++++++++++++++++++++++++++++++++++
security/selinux/nlmsgtab.c | 3 +-
6 files changed, 195 insertions(+), 5 deletions(-)

diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index 6064ea0a6f2b..906027aec40b 100644
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h
@@ -686,6 +686,7 @@ struct xfrm_migrate {
u8 mode;
u16 reserved;
u32 old_reqid;
+ u32 new_reqid;
u16 old_family;
u16 new_family;
};
diff --git a/include/uapi/linux/xfrm.h b/include/uapi/linux/xfrm.h
index a23495c0e0a1..60b1f201b237 100644
--- a/include/uapi/linux/xfrm.h
+++ b/include/uapi/linux/xfrm.h
@@ -227,6 +227,9 @@ enum {
#define XFRM_MSG_SETDEFAULT XFRM_MSG_SETDEFAULT
XFRM_MSG_GETDEFAULT,
#define XFRM_MSG_GETDEFAULT XFRM_MSG_GETDEFAULT
+
+ XFRM_MSG_MIGRATE_STATE,
+#define XFRM_MSG_MIGRATE_STATE XFRM_MSG_MIGRATE_STATE
__XFRM_MSG_MAX
};
#define XFRM_MSG_MAX (__XFRM_MSG_MAX - 1)
@@ -507,6 +510,14 @@ struct xfrm_user_migrate {
__u16 new_family;
};

+struct xfrm_user_migrate_state {
+ struct xfrm_usersa_id id;
+ xfrm_address_t new_saddr;
+ xfrm_address_t new_daddr;
+ __u16 new_family;
+ __u32 new_reqid;
+};
+
struct xfrm_user_mapping {
struct xfrm_usersa_id id;
__u32 reqid;
diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index 854dfc16ed55..72678053bd69 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -4672,6 +4672,7 @@ int xfrm_migrate(const struct xfrm_selector *sel, u8 dir, u8 type,
if ((x = xfrm_migrate_state_find(mp, net, if_id))) {
x_cur[nx_cur] = x;
nx_cur++;
+ mp->new_reqid = x->props.reqid; /* reqid is invariant in XFRM_MSG_MIGRATE */
xc = xfrm_state_migrate(x, mp, encap, net, xuo, extack);
if (xc) {
x_new[nx_new] = xc;
diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
index 2e03871ae872..945e0e470c0f 100644
--- a/net/xfrm/xfrm_state.c
+++ b/net/xfrm/xfrm_state.c
@@ -1979,7 +1979,6 @@ static struct xfrm_state *xfrm_state_clone_and_setup(struct xfrm_state *orig,
memcpy(&x->lft, &orig->lft, sizeof(x->lft));
x->props.mode = orig->props.mode;
x->props.replay_window = orig->props.replay_window;
- x->props.reqid = orig->props.reqid;

if (orig->aalg) {
x->aalg = xfrm_algo_auth_clone(orig->aalg);
@@ -2053,7 +2052,7 @@ static struct xfrm_state *xfrm_state_clone_and_setup(struct xfrm_state *orig,
goto error;
}

-
+ x->props.reqid = m->new_reqid;
x->props.family = m->new_family;
memcpy(&x->id.daddr, &m->new_daddr, sizeof(x->id.daddr));
memcpy(&x->props.saddr, &m->new_saddr, sizeof(x->props.saddr));
@@ -2159,9 +2158,10 @@ int xfrm_state_migrate_install(const struct xfrm_state *x,
struct xfrm_user_offload *xuo,
struct netlink_ext_ack *extack)
{
- if (xfrm_addr_equal(&x->id.daddr, &m->new_daddr, m->new_family)) {
+ if (xfrm_addr_equal(&x->id.daddr, &m->new_daddr, m->new_family) ||
+ x->props.reqid != xc->props.reqid) {
/*
- * Care is needed when the destination address
+ * Care is needed when the destination address or reqid
* of the state is to be updated as it is a part of triplet.
*/
xfrm_state_insert(xc);
diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index 26b82d94acc1..79e65e3e278a 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -3052,6 +3052,20 @@ static int xfrm_add_acquire(struct sk_buff *skb, struct nlmsghdr *nlh,
}

#ifdef CONFIG_XFRM_MIGRATE
+static void copy_from_user_migrate_state(struct xfrm_migrate *ma,
+ const struct xfrm_user_migrate_state *um)
+{
+ memcpy(&ma->old_daddr, &um->id.daddr, sizeof(ma->old_daddr));
+ memcpy(&ma->new_daddr, &um->new_daddr, sizeof(ma->new_daddr));
+ memcpy(&ma->new_saddr, &um->new_saddr, sizeof(ma->new_saddr));
+
+ ma->proto = um->id.proto;
+ ma->new_reqid = um->new_reqid;
+
+ ma->old_family = um->id.family;
+ ma->new_family = um->new_family;
+}
+
static int copy_from_user_migrate(struct xfrm_migrate *ma,
struct xfrm_kmaddress *k,
struct nlattr **attrs, int *num,
@@ -3154,7 +3168,167 @@ static int xfrm_do_migrate(struct sk_buff *skb, struct nlmsghdr *nlh,
kfree(xuo);
return err;
}
+
+static int build_migrate_state(struct sk_buff *skb,
+ const struct xfrm_user_migrate_state *m,
+ const struct xfrm_encap_tmpl *encap,
+ const struct xfrm_user_offload *xuo,
+ u32 portid, u32 seq)
+{
+ int err;
+ struct nlmsghdr *nlh;
+ struct xfrm_user_migrate_state *um;
+
+ nlh = nlmsg_put(skb, portid, seq, XFRM_MSG_MIGRATE_STATE,
+ sizeof(struct xfrm_user_migrate_state), 0);
+ if (!nlh)
+ return -EMSGSIZE;
+
+ um = nlmsg_data(nlh);
+ *um = *m;
+
+ if (encap) {
+ err = nla_put(skb, XFRMA_ENCAP, sizeof(*encap), encap);
+ if (err)
+ goto out_cancel;
+ }
+
+ if (xuo) {
+ err = nla_put(skb, XFRMA_OFFLOAD_DEV, sizeof(*xuo), xuo);
+ if (err)
+ goto out_cancel;
+ }
+
+ nlmsg_end(skb, nlh);
+ return 0;
+
+out_cancel:
+ nlmsg_cancel(skb, nlh);
+ return err;
+}
+
+static unsigned int xfrm_migrate_state_msgsize(bool with_encap, bool with_xuo)
+{
+ return NLMSG_ALIGN(sizeof(struct xfrm_user_migrate_state)) +
+ (with_encap ? nla_total_size(sizeof(struct xfrm_encap_tmpl)) : 0) +
+ (with_xuo ? nla_total_size(sizeof(struct xfrm_user_offload)) : 0);
+}
+
+static int xfrm_send_migrate_state(const struct xfrm_user_migrate_state *um,
+ const struct xfrm_encap_tmpl *encap,
+ const struct xfrm_user_offload *xuo,
+ u32 portid, u32 seq)
+{
+ int err;
+ struct sk_buff *skb;
+ struct net *net = &init_net;
+
+ skb = nlmsg_new(xfrm_migrate_state_msgsize(!!encap, !!xuo), GFP_ATOMIC);
+ if (!skb)
+ return -ENOMEM;
+
+ err = build_migrate_state(skb, um, encap, xuo, portid, seq);
+ if (err < 0) {
+ kfree_skb(skb);
+ return err;
+ }
+
+ return xfrm_nlmsg_multicast(net, skb, 0, XFRMNLGRP_MIGRATE);
+}
+
+static int xfrm_do_migrate_state(struct sk_buff *skb, struct nlmsghdr *nlh,
+ struct nlattr **attrs, struct netlink_ext_ack *extack)
+{
+ int err = -ESRCH;
+ struct xfrm_state *x;
+ struct xfrm_state *xc;
+ struct net *net = sock_net(skb->sk);
+ struct xfrm_encap_tmpl *encap = NULL;
+ struct xfrm_user_offload *xuo = NULL;
+ struct xfrm_migrate m = {};
+ struct xfrm_user_migrate_state *um = nlmsg_data(nlh);
+
+ if (!um->id.spi) {
+ NL_SET_ERR_MSG(extack, "Invalid SPI 0x0");
+ return -EINVAL;
+ }
+
+ copy_from_user_migrate_state(&m, um);
+
+ x = xfrm_user_state_lookup(net, &um->id, attrs, &err);
+ if (!x) {
+ NL_SET_ERR_MSG(extack, "Can not find state");
+ return err;
+ }
+
+ if (!x->dir) {
+ NL_SET_ERR_MSG(extack, "State direction is invalid");
+ err = -EINVAL;
+ goto out;
+ }
+
+ if (attrs[XFRMA_ENCAP]) {
+ encap = kmemdup(nla_data(attrs[XFRMA_ENCAP]), sizeof(*encap),
+ GFP_KERNEL);
+ if (!encap) {
+ err = -ENOMEM;
+ goto out;
+ }
+ }
+
+ if (attrs[XFRMA_OFFLOAD_DEV]) {
+ xuo = kmemdup(nla_data(attrs[XFRMA_OFFLOAD_DEV]),
+ sizeof(*xuo), GFP_KERNEL);
+ if (!xuo) {
+ err = -ENOMEM;
+ goto out;
+ }
+ }
+
+ xc = xfrm_state_migrate_create(x, &m, encap, net, xuo, extack);
+ if (!xc) {
+ if (extack && !extack->_msg)
+ NL_SET_ERR_MSG(extack, "State migration clone failed");
+ err = -EINVAL;
+ goto out;
+ }
+
+ spin_lock_bh(&x->lock);
+ /* synchronize to prevent SN/IV reuse */
+ xfrm_migrate_sync(xc, x);
+ __xfrm_state_delete(x);
+ spin_unlock_bh(&x->lock);
+
+ err = xfrm_state_migrate_install(x, xc, &m, xuo, extack);
+ if (err < 0) {
+ /*
+ * In this rare case both the old SA and the new SA
+ * will disappear.
+ * Alternatives risk duplicate SN/IV usage which must not occur.
+ * Userspace must handle this error, -EEXIST.
+ */
+ goto out;
+ }
+
+ err = xfrm_send_migrate_state(um, encap, xuo, nlh->nlmsg_pid,
+ nlh->nlmsg_seq);
+ if (err < 0)
+ NL_SET_ERR_MSG(extack, "Failed to send migration notification");
+out:
+ xfrm_state_put(x);
+ kfree(encap);
+ kfree(xuo);
+ return err;
+}
+
#else
+static int xfrm_do_migrate_state(struct sk_buff *skb, struct nlmsghdr *nlh,
+ struct nlattr **attrs, struct netlink_ext_ack *extack)
+{
+ NL_SET_ERR_MSG(extack, "XFRM_MSG_MIGRATE_STATE is not supported");
+ return -ENOPROTOOPT;
+}
+
static int xfrm_do_migrate(struct sk_buff *skb, struct nlmsghdr *nlh,
struct nlattr **attrs, struct netlink_ext_ack *extack)
{
@@ -3307,6 +3481,7 @@ const int xfrm_msg_min[XFRM_NR_MSGTYPES] = {
[XFRM_MSG_GETSPDINFO - XFRM_MSG_BASE] = sizeof(u32),
[XFRM_MSG_SETDEFAULT - XFRM_MSG_BASE] = XMSGSIZE(xfrm_userpolicy_default),
[XFRM_MSG_GETDEFAULT - XFRM_MSG_BASE] = XMSGSIZE(xfrm_userpolicy_default),
+ [XFRM_MSG_MIGRATE_STATE - XFRM_MSG_BASE] = XMSGSIZE(xfrm_user_migrate_state),
};
EXPORT_SYMBOL_GPL(xfrm_msg_min);

@@ -3400,6 +3575,7 @@ static const struct xfrm_link {
[XFRM_MSG_GETSPDINFO - XFRM_MSG_BASE] = { .doit = xfrm_get_spdinfo },
[XFRM_MSG_SETDEFAULT - XFRM_MSG_BASE] = { .doit = xfrm_set_default },
[XFRM_MSG_GETDEFAULT - XFRM_MSG_BASE] = { .doit = xfrm_get_default },
+ [XFRM_MSG_MIGRATE_STATE - XFRM_MSG_BASE] = { .doit = xfrm_do_migrate_state },
};

static int xfrm_reject_unused_attr(int type, struct nlattr **attrs,
diff --git a/security/selinux/nlmsgtab.c b/security/selinux/nlmsgtab.c
index 2c0b07f9fbbd..655d2616c9d2 100644
--- a/security/selinux/nlmsgtab.c
+++ b/security/selinux/nlmsgtab.c
@@ -128,6 +128,7 @@ static const struct nlmsg_perm nlmsg_xfrm_perms[] = {
{ XFRM_MSG_MAPPING, NETLINK_XFRM_SOCKET__NLMSG_READ },
{ XFRM_MSG_SETDEFAULT, NETLINK_XFRM_SOCKET__NLMSG_WRITE },
{ XFRM_MSG_GETDEFAULT, NETLINK_XFRM_SOCKET__NLMSG_READ },
+ { XFRM_MSG_MIGRATE_STATE, NETLINK_XFRM_SOCKET__NLMSG_WRITE },
};

static const struct nlmsg_perm nlmsg_audit_perms[] = {
@@ -203,7 +204,7 @@ int selinux_nlmsg_lookup(u16 sclass, u16 nlmsg_type, u32 *perm)
* structures at the top of this file with the new mappings
* before updating the BUILD_BUG_ON() macro!
*/
- BUILD_BUG_ON(XFRM_MSG_MAX != XFRM_MSG_GETDEFAULT);
+ BUILD_BUG_ON(XFRM_MSG_MAX != XFRM_MSG_MIGRATE_STATE);

if (selinux_policycap_netlink_xperm()) {
*perm = NETLINK_XFRM_SOCKET__NLMSG;
--
2.39.5