Merge branch 'xfrm: XFRM_MSG_MIGRATE_STATE new netlink message'

Antony Antony says:

====================
The current XFRM_MSG_MIGRATE interface is tightly coupled to policy and
SA migration, and it lacks the information required to reliably migrate
individual SAs. This makes it unsuitable for IKEv2 deployments,
dual-stack setups (IPv4/IPv6), and scenarios where policies are managed
externally (e.g., by daemons other than the IKE daemon).

Mandatory SA selector list
The current API requires a non-empty SA selector list, which does not
reflect the IKEv2 use case.
A single Child SA may correspond to multiple policies,
and SA discovery already occurs via address and reqid matching. With
dual-stack Child SAs this leads to excessive churn: the current method
would have to be called up to six times (in/out/fwd × v4/v6) on SA,
while the new method only requires two calls.

Selectors lack SPI (and marks)
XFRM_MSG_MIGRATE cannot uniquely identify an SA when multiple SAs share
the same policies (per-CPU SAs, SELinux label-based SAs, etc.). Without
the SPI, the kernel may update the wrong SA instance.

Reqid cannot be changed
Some implementations allocate reqids based on traffic selectors. In
host-to-host or selector-changing scenarios, the reqid must change,
which the current API cannot express.

Because strongSwan and other implementations manage policies
independently of the kernel, an interface that updates only a specific
SA - with complete and unambiguous identification - is required.

SA Selector, x->sel, can't be changed, especially Transport mode.

XFRM_MSG_MIGRATE_STATE provides that interface. It supports migration
of a single SA via xfrm_usersa_id (including SPI) and we fix
encap removal in this patch set, reqid updates, address changes,
and other SA-specific parameters. It avoids the structural limitations
of XFRM_MSG_MIGRATE and provides a simpler, extensible mechanism for
precise per-SA migration without involving policies.
This method also allows migtrating SA selectors typically used with
host-to-host in Transport mode.

New migration steps: first install block policy, remove the old policy,
call XFRM_MSG_MIGRATE_STATE for each state, then re-install the
policies and remove the block policy.

If the target SA tuple (daddr, SPI, proto, family) is already
occupied, the operation returns -EEXIST. In this case the original
SA is not preserved. Userspace must handle -EEXIST by
re-establishing the SA at the IKE level and manage policies.
====================

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

1 files changed, 25 insertions, 0 deletions

diff --git a/include/uapi/linux/xfrm.h b/include/uapi/linux/xfrm.h
index a23495c0e0a1..051f8066efd1 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 +510,28 @@ struct xfrm_user_migrate {
 	__u16				new_family;
 };
 
+struct xfrm_user_migrate_state {
+	struct xfrm_usersa_id id;
+	xfrm_address_t new_daddr;
+	xfrm_address_t new_saddr;
+	struct xfrm_mark old_mark;
+	struct xfrm_selector new_sel;
+	__u32 new_reqid;
+	__u32 flags;
+	__u16 new_family;
+	__u16 reserved;
+};
+
+/* Flags for xfrm_user_migrate_state.flags */
+enum xfrm_migrate_state_flags {
+	XFRM_MIGRATE_STATE_CLEAR_OFFLOAD = 1, /* do not inherit offload from existing SA */
+	XFRM_MIGRATE_STATE_UPDATE_H2H_SEL = 2, /* update H2H selector from new daddr/saddr */
+};
+
+/* All flags defined as of this header version; unknown bits are rejected. */
+#define XFRM_MIGRATE_STATE_KNOWN_FLAGS \
+	(XFRM_MIGRATE_STATE_CLEAR_OFFLOAD | XFRM_MIGRATE_STATE_UPDATE_H2H_SEL)
+
 struct xfrm_user_mapping {
 	struct xfrm_usersa_id		id;
 	__u32				reqid;