diff --git a/include/net/esp.h b/include/net/esp.h
new file mode 100644
index 0000000..90cd94f
--- /dev/null
+++ b/include/net/esp.h
@@ -0,0 +1,59 @@
+#ifndef _NET_ESP_H
+#define _NET_ESP_H
+
+#include <net/xfrm.h>
+#include <asm/scatterlist.h>
+
+#define ESP_NUM_FAST_SG		4
+
+struct esp_data
+{
+	struct scatterlist		sgbuf[ESP_NUM_FAST_SG];
+
+	/* Confidentiality */
+	struct {
+		u8			*key;		/* Key */
+		int			key_len;	/* Key length */
+		u8			*ivec;		/* ivec buffer */
+		/* ivlen is offset from enc_data, where encrypted data start.
+		 * It is logically different of crypto_tfm_alg_ivsize(tfm).
+		 * We assume that it is either zero (no ivec), or
+		 * >= crypto_tfm_alg_ivsize(tfm). */
+		int			ivlen;
+		int			padlen;		/* 0..255 */
+		struct crypto_tfm	*tfm;		/* crypto handle */
+	} conf;
+
+	/* Integrity. It is active when icv_full_len != 0 */
+	struct {
+		u8			*key;		/* Key */
+		int			key_len;	/* Length of the key */
+		u8			*work_icv;
+		int			icv_full_len;
+		int			icv_trunc_len;
+		void			(*icv)(struct esp_data*,
+		                               struct sk_buff *skb,
+		                               int offset, int len, u8 *icv);
+		struct crypto_tfm	*tfm;
+	} auth;
+};
+
+extern int skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len);
+extern int skb_cow_data(struct sk_buff *skb, int tailbits, struct sk_buff **trailer);
+extern void *pskb_put(struct sk_buff *skb, struct sk_buff *tail, int len);
+
+static inline void
+esp_hmac_digest(struct esp_data *esp, struct sk_buff *skb, int offset,
+                int len, u8 *auth_data)
+{
+	struct crypto_tfm *tfm = esp->auth.tfm;
+	char *icv = esp->auth.work_icv;
+
+	memset(auth_data, 0, esp->auth.icv_trunc_len);
+	crypto_hmac_init(tfm, esp->auth.key, &esp->auth.key_len);
+	skb_icv_walk(skb, tfm, offset, len, crypto_hmac_update);
+	crypto_hmac_final(tfm, esp->auth.key, &esp->auth.key_len, icv);
+	memcpy(auth_data, icv, esp->auth.icv_trunc_len);
+}
+
+#endif