1 files changed, 86 insertions, 0 deletions
diff --git a/drivers/net/ovpn/pktid.h b/drivers/net/ovpn/pktid.h
new file mode 100644
index 000000000000..0262d026d15e
--- /dev/null
+++ b/drivers/net/ovpn/pktid.h
@@ -0,0 +1,86 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*  OpenVPN data channel offload
+ *
+ *  Copyright (C) 2020-2025 OpenVPN, Inc.
+ *
+ *  Author:	Antonio Quartulli <antonio@openvpn.net>
+ *		James Yonan <james@openvpn.net>
+ */
+
+#ifndef _NET_OVPN_OVPNPKTID_H_
+#define _NET_OVPN_OVPNPKTID_H_
+
+#include "proto.h"
+
+/* If no packets received for this length of time, set a backtrack floor
+ * at highest received packet ID thus far.
+ */
+#define PKTID_RECV_EXPIRE (30 * HZ)
+
+/* Packet-ID state for transmitter */
+struct ovpn_pktid_xmit {
+	atomic_t seq_num;
+};
+
+/* replay window sizing in bytes = 2^REPLAY_WINDOW_ORDER */
+#define REPLAY_WINDOW_ORDER 8
+
+#define REPLAY_WINDOW_BYTES BIT(REPLAY_WINDOW_ORDER)
+#define REPLAY_WINDOW_SIZE  (REPLAY_WINDOW_BYTES * 8)
+#define REPLAY_INDEX(base, i) (((base) + (i)) & (REPLAY_WINDOW_SIZE - 1))
+
+/* Packet-ID state for receiver.
+ * Other than lock member, can be zeroed to initialize.
+ */
+struct ovpn_pktid_recv {
+	/* "sliding window" bitmask of recent packet IDs received */
+	u8 history[REPLAY_WINDOW_BYTES];
+	/* bit position of deque base in history */
+	unsigned int base;
+	/* extent (in bits) of deque in history */
+	unsigned int extent;
+	/* expiration of history in jiffies */
+	unsigned long expire;
+	/* highest sequence number received */
+	u32 id;
+	/* highest time stamp received */
+	u32 time;
+	/* we will only accept backtrack IDs > id_floor */
+	u32 id_floor;
+	unsigned int max_backtrack;
+	/* protects entire pktd ID state */
+	spinlock_t lock;
+};
+
+/* Get the next packet ID for xmit */
+static inline int ovpn_pktid_xmit_next(struct ovpn_pktid_xmit *pid, u32 *pktid)
+{
+	const u32 seq_num = atomic_fetch_add_unless(&pid->seq_num, 1, 0);
+	/* when the 32bit space is over, we return an error because the packet
+	 * ID is used to create the cipher IV and we do not want to reuse the
+	 * same value more than once
+	 */
+	if (unlikely(!seq_num))
+		return -ERANGE;
+
+	*pktid = seq_num;
+
+	return 0;
+}
+
+/* Write 12-byte AEAD IV to dest */
+static inline void ovpn_pktid_aead_write(const u32 pktid,
+					 const u8 nt[],
+					 unsigned char *dest)
+{
+	*(__force __be32 *)(dest) = htonl(pktid);
+	BUILD_BUG_ON(4 + OVPN_NONCE_TAIL_SIZE != OVPN_NONCE_SIZE);
+	memcpy(dest + 4, nt, OVPN_NONCE_TAIL_SIZE);
+}
+
+void ovpn_pktid_xmit_init(struct ovpn_pktid_xmit *pid);
+void ovpn_pktid_recv_init(struct ovpn_pktid_recv *pr);
+
+int ovpn_pktid_recv(struct ovpn_pktid_recv *pr, u32 pkt_id, u32 pkt_time);
+
+#endif /* _NET_OVPN_OVPNPKTID_H_ */