net/tls/tls_device_fallback.c - linux - Git at Google

 /* Copyright (c) 2018, Mellanox Technologies All rights reserved.
  *
  * This software is available to you under a choice of one of two
  * licenses.  You may choose to be licensed under the terms of the GNU
  * General Public License (GPL) Version 2, available from the file
  * COPYING in the main directory of this source tree, or the
  * OpenIB.org BSD license below:
  *
  *     Redistribution and use in source and binary forms, with or
  *     without modification, are permitted provided that the following
  *     conditions are met:
  *
  *      - Redistributions of source code must retain the above
  *        copyright notice, this list of conditions and the following
  *        disclaimer.
  *
  *      - Redistributions in binary form must reproduce the above
  *        copyright notice, this list of conditions and the following
  *        disclaimer in the documentation and/or other materials
  *        provided with the distribution.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  */

 #include <net/tls.h>
 #include <crypto/aead.h>
 #include <crypto/scatterwalk.h>
 #include <net/ip6_checksum.h>

 static void chain_to_walk(struct scatterlist *sg, struct scatter_walk *walk)
 {
 	struct scatterlist *src = walk->sg;
 	int diff = walk->offset - src->offset;

 	sg_set_page(sg, sg_page(src),
 		    src->length - diff, walk->offset);

 	scatterwalk_crypto_chain(sg, sg_next(src), 2);
 }

 static int tls_enc_record(struct aead_request *aead_req,
 			  struct crypto_aead *aead, char *aad,
 			  char *iv, __be64 rcd_sn,
 			  struct scatter_walk *in,
 			  struct scatter_walk *out, int *in_len,
 			  struct tls_prot_info *prot)
 {
 	unsigned char buf[TLS_HEADER_SIZE + TLS_CIPHER_AES_GCM_128_IV_SIZE];
 	struct scatterlist sg_in[3];
 	struct scatterlist sg_out[3];
 	u16 len;
 	int rc;

 	len = min_t(int, *in_len, ARRAY_SIZE(buf));

 	scatterwalk_copychunks(buf, in, len, 0);
 	scatterwalk_copychunks(buf, out, len, 1);

 	*in_len -= len;
 	if (!*in_len)
 		return 0;

 	scatterwalk_pagedone(in, 0, 1);
 	scatterwalk_pagedone(out, 1, 1);

 	len = buf[4] | (buf[3] << 8);
 	len -= TLS_CIPHER_AES_GCM_128_IV_SIZE;

 	tls_make_aad(aad, len - TLS_CIPHER_AES_GCM_128_TAG_SIZE,
 		(char *)&rcd_sn, buf[0], prot);

 	memcpy(iv + TLS_CIPHER_AES_GCM_128_SALT_SIZE, buf + TLS_HEADER_SIZE,
 	       TLS_CIPHER_AES_GCM_128_IV_SIZE);

 	sg_init_table(sg_in, ARRAY_SIZE(sg_in));
 	sg_init_table(sg_out, ARRAY_SIZE(sg_out));
 	sg_set_buf(sg_in, aad, TLS_AAD_SPACE_SIZE);
 	sg_set_buf(sg_out, aad, TLS_AAD_SPACE_SIZE);
 	chain_to_walk(sg_in + 1, in);
 	chain_to_walk(sg_out + 1, out);

 	*in_len -= len;
 	if (*in_len < 0) {
 		*in_len += TLS_CIPHER_AES_GCM_128_TAG_SIZE;
 		/* the input buffer doesn't contain the entire record.
 		 * trim len accordingly. The resulting authentication tag
 		 * will contain garbage, but we don't care, so we won't
 		 * include any of it in the output skb
 		 * Note that we assume the output buffer length
 		 * is larger then input buffer length + tag size
 		 */
 		if (*in_len < 0)
 			len += *in_len;

 		*in_len = 0;
 	}

 	if (*in_len) {
 		scatterwalk_copychunks(NULL, in, len, 2);
 		scatterwalk_pagedone(in, 0, 1);
 		scatterwalk_copychunks(NULL, out, len, 2);
 		scatterwalk_pagedone(out, 1, 1);
 	}

 	len -= TLS_CIPHER_AES_GCM_128_TAG_SIZE;
 	aead_request_set_crypt(aead_req, sg_in, sg_out, len, iv);

 	rc = crypto_aead_encrypt(aead_req);

 	return rc;
 }

 static void tls_init_aead_request(struct aead_request *aead_req,
 				  struct crypto_aead *aead)
 {
 	aead_request_set_tfm(aead_req, aead);
 	aead_request_set_ad(aead_req, TLS_AAD_SPACE_SIZE);
 }

 static struct aead_request *tls_alloc_aead_request(struct crypto_aead *aead,
 						   gfp_t flags)
 {
 	unsigned int req_size = sizeof(struct aead_request) +
 		crypto_aead_reqsize(aead);
 	struct aead_request *aead_req;

 	aead_req = kzalloc(req_size, flags);
 	if (aead_req)
 		tls_init_aead_request(aead_req, aead);
 	return aead_req;
 }

 static int tls_enc_records(struct aead_request *aead_req,
 			   struct crypto_aead *aead, struct scatterlist *sg_in,
 			   struct scatterlist *sg_out, char *aad, char *iv,
 			   u64 rcd_sn, int len, struct tls_prot_info *prot)
 {
 	struct scatter_walk out, in;
 	int rc;

 	scatterwalk_start(&in, sg_in);
 	scatterwalk_start(&out, sg_out);

 	do {
 		rc = tls_enc_record(aead_req, aead, aad, iv,
 				    cpu_to_be64(rcd_sn), &in, &out, &len, prot);
 		rcd_sn++;

 	} while (rc == 0 && len);

 	scatterwalk_done(&in, 0, 0);
 	scatterwalk_done(&out, 1, 0);

 	return rc;
 }

 /* Can't use icsk->icsk_af_ops->send_check here because the ip addresses
  * might have been changed by NAT.
  */
 static void update_chksum(struct sk_buff *skb, int headln)
 {
 	struct tcphdr *th = tcp_hdr(skb);
 	int datalen = skb->len - headln;
 	const struct ipv6hdr *ipv6h;
 	const struct iphdr *iph;

 	/* We only changed the payload so if we are using partial we don't
 	 * need to update anything.
 	 */
 	if (likely(skb->ip_summed == CHECKSUM_PARTIAL))
 		return;

 	skb->ip_summed = CHECKSUM_PARTIAL;
 	skb->csum_start = skb_transport_header(skb) - skb->head;
 	skb->csum_offset = offsetof(struct tcphdr, check);

 	if (skb->sk->sk_family == AF_INET6) {
 		ipv6h = ipv6_hdr(skb);
 		th->check = ~csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr,
 					     datalen, IPPROTO_TCP, 0);
 	} else {
 		iph = ip_hdr(skb);
 		th->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr, datalen,
 					       IPPROTO_TCP, 0);
 	}
 }

 static void complete_skb(struct sk_buff *nskb, struct sk_buff *skb, int headln)
 {
 	struct sock *sk = skb->sk;
 	int delta;

 	skb_copy_header(nskb, skb);

 	skb_put(nskb, skb->len);
 	memcpy(nskb->data, skb->data, headln);

 	nskb->destructor = skb->destructor;
 	nskb->sk = sk;
 	skb->destructor = NULL;
 	skb->sk = NULL;

 	update_chksum(nskb, headln);

 	/* sock_efree means skb must gone through skb_orphan_partial() */
 	if (nskb->destructor == sock_efree)
 		return;

 	delta = nskb->truesize - skb->truesize;
 	if (likely(delta < 0))
 		WARN_ON_ONCE(refcount_sub_and_test(-delta, &sk->sk_wmem_alloc));
 	else if (delta)
 		refcount_add(delta, &sk->sk_wmem_alloc);
 }

 /* This function may be called after the user socket is already
  * closed so make sure we don't use anything freed during
  * tls_sk_proto_close here
  */

 static int fill_sg_in(struct scatterlist *sg_in,
 		      struct sk_buff *skb,
 		      struct tls_offload_context_tx *ctx,
 		      u64 *rcd_sn,
 		      s32 *sync_size,
 		      int *resync_sgs)
 {
 	int tcp_payload_offset = skb_transport_offset(skb) + tcp_hdrlen(skb);
 	int payload_len = skb->len - tcp_payload_offset;
 	u32 tcp_seq = ntohl(tcp_hdr(skb)->seq);
 	struct tls_record_info *record;
 	unsigned long flags;
 	int remaining;
 	int i;

 	spin_lock_irqsave(&ctx->lock, flags);
 	record = tls_get_record(ctx, tcp_seq, rcd_sn);
 	if (!record) {
 		spin_unlock_irqrestore(&ctx->lock, flags);
 		return -EINVAL;
 	}

 	*sync_size = tcp_seq - tls_record_start_seq(record);
 	if (*sync_size < 0) {
 		int is_start_marker = tls_record_is_start_marker(record);

 		spin_unlock_irqrestore(&ctx->lock, flags);
 		/* This should only occur if the relevant record was
 		 * already acked. In that case it should be ok
 		 * to drop the packet and avoid retransmission.
 		 *
 		 * There is a corner case where the packet contains
 		 * both an acked and a non-acked record.
 		 * We currently don't handle that case and rely
 		 * on TCP to retranmit a packet that doesn't contain
 		 * already acked payload.
 		 */
 		if (!is_start_marker)
 			*sync_size = 0;
 		return -EINVAL;
 	}

 	remaining = *sync_size;
 	for (i = 0; remaining > 0; i++) {
 		skb_frag_t *frag = &record->frags[i];

 		__skb_frag_ref(frag);
 		sg_set_page(sg_in + i, skb_frag_page(frag),
 			    skb_frag_size(frag), skb_frag_off(frag));

 		remaining -= skb_frag_size(frag);

 		if (remaining < 0)
 			sg_in[i].length += remaining;
 	}
 	*resync_sgs = i;

 	spin_unlock_irqrestore(&ctx->lock, flags);
 	if (skb_to_sgvec(skb, &sg_in[i], tcp_payload_offset, payload_len) < 0)
 		return -EINVAL;

 	return 0;
 }

 static void fill_sg_out(struct scatterlist sg_out[3], void *buf,
 			struct tls_context *tls_ctx,
 			struct sk_buff *nskb,
 			int tcp_payload_offset,
 			int payload_len,
 			int sync_size,
 			void *dummy_buf)
 {
 	sg_set_buf(&sg_out[0], dummy_buf, sync_size);
 	sg_set_buf(&sg_out[1], nskb->data + tcp_payload_offset, payload_len);
 	/* Add room for authentication tag produced by crypto */
 	dummy_buf += sync_size;
 	sg_set_buf(&sg_out[2], dummy_buf, TLS_CIPHER_AES_GCM_128_TAG_SIZE);
 }

 static struct sk_buff *tls_enc_skb(struct tls_context *tls_ctx,
 				   struct scatterlist sg_out[3],
 				   struct scatterlist *sg_in,
 				   struct sk_buff *skb,
 				   s32 sync_size, u64 rcd_sn)
 {
 	int tcp_payload_offset = skb_transport_offset(skb) + tcp_hdrlen(skb);
 	struct tls_offload_context_tx *ctx = tls_offload_ctx_tx(tls_ctx);
 	int payload_len = skb->len - tcp_payload_offset;
 	void *buf, *iv, *aad, *dummy_buf;
 	struct aead_request *aead_req;
 	struct sk_buff *nskb = NULL;
 	int buf_len;

 	aead_req = tls_alloc_aead_request(ctx->aead_send, GFP_ATOMIC);
 	if (!aead_req)
 		return NULL;

 	buf_len = TLS_CIPHER_AES_GCM_128_SALT_SIZE +
 		  TLS_CIPHER_AES_GCM_128_IV_SIZE +
 		  TLS_AAD_SPACE_SIZE +
 		  sync_size +
 		  TLS_CIPHER_AES_GCM_128_TAG_SIZE;
 	buf = kmalloc(buf_len, GFP_ATOMIC);
 	if (!buf)
 		goto free_req;

 	iv = buf;
 	memcpy(iv, tls_ctx->crypto_send.aes_gcm_128.salt,
 	       TLS_CIPHER_AES_GCM_128_SALT_SIZE);
 	aad = buf + TLS_CIPHER_AES_GCM_128_SALT_SIZE +
 	      TLS_CIPHER_AES_GCM_128_IV_SIZE;
 	dummy_buf = aad + TLS_AAD_SPACE_SIZE;

 	nskb = alloc_skb(skb_headroom(skb) + skb->len, GFP_ATOMIC);
 	if (!nskb)
 		goto free_buf;

 	skb_reserve(nskb, skb_headroom(skb));

 	fill_sg_out(sg_out, buf, tls_ctx, nskb, tcp_payload_offset,
 		    payload_len, sync_size, dummy_buf);

 	if (tls_enc_records(aead_req, ctx->aead_send, sg_in, sg_out, aad, iv,
 			    rcd_sn, sync_size + payload_len,
 			    &tls_ctx->prot_info) < 0)
 		goto free_nskb;

 	complete_skb(nskb, skb, tcp_payload_offset);

 	/* validate_xmit_skb_list assumes that if the skb wasn't segmented
 	 * nskb->prev will point to the skb itself
 	 */
 	nskb->prev = nskb;

 free_buf:
 	kfree(buf);
 free_req:
 	kfree(aead_req);
 	return nskb;
 free_nskb:
 	kfree_skb(nskb);
 	nskb = NULL;
 	goto free_buf;
 }

 static struct sk_buff *tls_sw_fallback(struct sock *sk, struct sk_buff *skb)
 {
 	int tcp_payload_offset = skb_transport_offset(skb) + tcp_hdrlen(skb);
 	struct tls_context *tls_ctx = tls_get_ctx(sk);
 	struct tls_offload_context_tx *ctx = tls_offload_ctx_tx(tls_ctx);
 	int payload_len = skb->len - tcp_payload_offset;
 	struct scatterlist *sg_in, sg_out[3];
 	struct sk_buff *nskb = NULL;
 	int sg_in_max_elements;
 	int resync_sgs = 0;
 	s32 sync_size = 0;
 	u64 rcd_sn;

 	/* worst case is:
 	 * MAX_SKB_FRAGS in tls_record_info
 	 * MAX_SKB_FRAGS + 1 in SKB head and frags.
 	 */
 	sg_in_max_elements = 2 * MAX_SKB_FRAGS + 1;

 	if (!payload_len)
 		return skb;

 	sg_in = kmalloc_array(sg_in_max_elements, sizeof(*sg_in), GFP_ATOMIC);
 	if (!sg_in)
 		goto free_orig;

 	sg_init_table(sg_in, sg_in_max_elements);
 	sg_init_table(sg_out, ARRAY_SIZE(sg_out));

 	if (fill_sg_in(sg_in, skb, ctx, &rcd_sn, &sync_size, &resync_sgs)) {
 		/* bypass packets before kernel TLS socket option was set */
 		if (sync_size < 0 && payload_len <= -sync_size)
 			nskb = skb_get(skb);
 		goto put_sg;
 	}

 	nskb = tls_enc_skb(tls_ctx, sg_out, sg_in, skb, sync_size, rcd_sn);

 put_sg:
 	while (resync_sgs)
 		put_page(sg_page(&sg_in[--resync_sgs]));
 	kfree(sg_in);
 free_orig:
 	if (nskb)
 		consume_skb(skb);
 	else
 		kfree_skb(skb);
 	return nskb;
 }

 struct sk_buff *tls_validate_xmit_skb(struct sock *sk,
 				      struct net_device *dev,
 				      struct sk_buff *skb)
 {
 	if (dev == tls_get_ctx(sk)->netdev)
 		return skb;

 	return tls_sw_fallback(sk, skb);
 }
 EXPORT_SYMBOL_GPL(tls_validate_xmit_skb);

 struct sk_buff *tls_encrypt_skb(struct sk_buff *skb)
 {
 	return tls_sw_fallback(skb->sk, skb);
 }
 EXPORT_SYMBOL_GPL(tls_encrypt_skb);

 int tls_sw_fallback_init(struct sock *sk,
 			 struct tls_offload_context_tx *offload_ctx,
 			 struct tls_crypto_info *crypto_info)
 {
 	const u8 *key;
 	int rc;

 	offload_ctx->aead_send =
 	    crypto_alloc_aead("gcm(aes)", 0, CRYPTO_ALG_ASYNC);
 	if (IS_ERR(offload_ctx->aead_send)) {
 		rc = PTR_ERR(offload_ctx->aead_send);
 		pr_err_ratelimited("crypto_alloc_aead failed rc=%d\n", rc);
 		offload_ctx->aead_send = NULL;
 		goto err_out;
 	}

 	key = ((struct tls12_crypto_info_aes_gcm_128 *)crypto_info)->key;

 	rc = crypto_aead_setkey(offload_ctx->aead_send, key,
 				TLS_CIPHER_AES_GCM_128_KEY_SIZE);
 	if (rc)
 		goto free_aead;

 	rc = crypto_aead_setauthsize(offload_ctx->aead_send,
 				     TLS_CIPHER_AES_GCM_128_TAG_SIZE);
 	if (rc)
 		goto free_aead;

 	return 0;
 free_aead:
 	crypto_free_aead(offload_ctx->aead_send);
 err_out:
 	return rc;
 }
	/* Copyright (c) 2018, Mellanox Technologies All rights reserved.
	*
	* This software is available to you under a choice of one of two
	* licenses. You may choose to be licensed under the terms of the GNU
	* General Public License (GPL) Version 2, available from the file
	* COPYING in the main directory of this source tree, or the
	* OpenIB.org BSD license below:
	*
	* Redistribution and use in source and binary forms, with or
	* without modification, are permitted provided that the following
	* conditions are met:
	*
	* - Redistributions of source code must retain the above
	* copyright notice, this list of conditions and the following
	* disclaimer.
	*
	* - Redistributions in binary form must reproduce the above
	* copyright notice, this list of conditions and the following
	* disclaimer in the documentation and/or other materials
	* provided with the distribution.
	*
	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
	* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
	* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
	* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
	* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
	* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
	* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
	* SOFTWARE.
	*/

	#include <net/tls.h>
	#include <crypto/aead.h>
	#include <crypto/scatterwalk.h>
	#include <net/ip6_checksum.h>

	static void chain_to_walk(struct scatterlist sg, struct scatter_walk walk)
	{
	struct scatterlist *src = walk->sg;
	int diff = walk->offset - src->offset;

	sg_set_page(sg, sg_page(src),
	src->length - diff, walk->offset);

	scatterwalk_crypto_chain(sg, sg_next(src), 2);
	}

	static int tls_enc_record(struct aead_request *aead_req,
	struct crypto_aead aead, char aad,
	char *iv, __be64 rcd_sn,
	struct scatter_walk *in,
	struct scatter_walk out, int in_len,
	struct tls_prot_info *prot)
	{
	unsigned char buf[TLS_HEADER_SIZE + TLS_CIPHER_AES_GCM_128_IV_SIZE];
	struct scatterlist sg_in[3];
	struct scatterlist sg_out[3];
	u16 len;
	int rc;

	len = min_t(int, *in_len, ARRAY_SIZE(buf));

	scatterwalk_copychunks(buf, in, len, 0);
	scatterwalk_copychunks(buf, out, len, 1);

	*in_len -= len;
	if (!*in_len)
	return 0;

	scatterwalk_pagedone(in, 0, 1);
	scatterwalk_pagedone(out, 1, 1);

	len = buf[4] \| (buf[3] << 8);
	len -= TLS_CIPHER_AES_GCM_128_IV_SIZE;

	tls_make_aad(aad, len - TLS_CIPHER_AES_GCM_128_TAG_SIZE,
	(char *)&rcd_sn, buf[0], prot);

	memcpy(iv + TLS_CIPHER_AES_GCM_128_SALT_SIZE, buf + TLS_HEADER_SIZE,
	TLS_CIPHER_AES_GCM_128_IV_SIZE);

	sg_init_table(sg_in, ARRAY_SIZE(sg_in));
	sg_init_table(sg_out, ARRAY_SIZE(sg_out));
	sg_set_buf(sg_in, aad, TLS_AAD_SPACE_SIZE);
	sg_set_buf(sg_out, aad, TLS_AAD_SPACE_SIZE);
	chain_to_walk(sg_in + 1, in);
	chain_to_walk(sg_out + 1, out);

	*in_len -= len;
	if (*in_len < 0) {
	*in_len += TLS_CIPHER_AES_GCM_128_TAG_SIZE;
	/* the input buffer doesn't contain the entire record.
	* trim len accordingly. The resulting authentication tag
	* will contain garbage, but we don't care, so we won't
	* include any of it in the output skb
	* Note that we assume the output buffer length
	* is larger then input buffer length + tag size
	*/
	if (*in_len < 0)
	len += *in_len;

	*in_len = 0;
	}

	if (*in_len) {
	scatterwalk_copychunks(NULL, in, len, 2);
	scatterwalk_pagedone(in, 0, 1);
	scatterwalk_copychunks(NULL, out, len, 2);
	scatterwalk_pagedone(out, 1, 1);
	}

	len -= TLS_CIPHER_AES_GCM_128_TAG_SIZE;
	aead_request_set_crypt(aead_req, sg_in, sg_out, len, iv);

	rc = crypto_aead_encrypt(aead_req);

	return rc;
	}

	static void tls_init_aead_request(struct aead_request *aead_req,
	struct crypto_aead *aead)
	{
	aead_request_set_tfm(aead_req, aead);
	aead_request_set_ad(aead_req, TLS_AAD_SPACE_SIZE);
	}

	static struct aead_request tls_alloc_aead_request(struct crypto_aead aead,
	gfp_t flags)
	{
	unsigned int req_size = sizeof(struct aead_request) +
	crypto_aead_reqsize(aead);
	struct aead_request *aead_req;

	aead_req = kzalloc(req_size, flags);
	if (aead_req)
	tls_init_aead_request(aead_req, aead);
	return aead_req;
	}

	static int tls_enc_records(struct aead_request *aead_req,
	struct crypto_aead aead, struct scatterlist sg_in,
	struct scatterlist sg_out, char aad, char *iv,
	u64 rcd_sn, int len, struct tls_prot_info *prot)
	{
	struct scatter_walk out, in;
	int rc;

	scatterwalk_start(&in, sg_in);
	scatterwalk_start(&out, sg_out);

	do {
	rc = tls_enc_record(aead_req, aead, aad, iv,
	cpu_to_be64(rcd_sn), &in, &out, &len, prot);
	rcd_sn++;

	} while (rc == 0 && len);

	scatterwalk_done(&in, 0, 0);
	scatterwalk_done(&out, 1, 0);

	return rc;
	}

	/* Can't use icsk->icsk_af_ops->send_check here because the ip addresses
	* might have been changed by NAT.
	*/
	static void update_chksum(struct sk_buff *skb, int headln)
	{
	struct tcphdr *th = tcp_hdr(skb);
	int datalen = skb->len - headln;
	const struct ipv6hdr *ipv6h;
	const struct iphdr *iph;

	/* We only changed the payload so if we are using partial we don't
	* need to update anything.
	*/
	if (likely(skb->ip_summed == CHECKSUM_PARTIAL))
	return;

	skb->ip_summed = CHECKSUM_PARTIAL;
	skb->csum_start = skb_transport_header(skb) - skb->head;
	skb->csum_offset = offsetof(struct tcphdr, check);

	if (skb->sk->sk_family == AF_INET6) {
	ipv6h = ipv6_hdr(skb);
	th->check = ~csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr,
	datalen, IPPROTO_TCP, 0);
	} else {
	iph = ip_hdr(skb);
	th->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr, datalen,
	IPPROTO_TCP, 0);
	}
	}

	static void complete_skb(struct sk_buff nskb, struct sk_buff skb, int headln)
	{
	struct sock *sk = skb->sk;
	int delta;

	skb_copy_header(nskb, skb);

	skb_put(nskb, skb->len);
	memcpy(nskb->data, skb->data, headln);

	nskb->destructor = skb->destructor;
	nskb->sk = sk;
	skb->destructor = NULL;
	skb->sk = NULL;

	update_chksum(nskb, headln);

	/* sock_efree means skb must gone through skb_orphan_partial() */
	if (nskb->destructor == sock_efree)
	return;

	delta = nskb->truesize - skb->truesize;
	if (likely(delta < 0))
	WARN_ON_ONCE(refcount_sub_and_test(-delta, &sk->sk_wmem_alloc));
	else if (delta)
	refcount_add(delta, &sk->sk_wmem_alloc);
	}

	/* This function may be called after the user socket is already
	* closed so make sure we don't use anything freed during
	* tls_sk_proto_close here
	*/

	static int fill_sg_in(struct scatterlist *sg_in,
	struct sk_buff *skb,
	struct tls_offload_context_tx *ctx,
	u64 *rcd_sn,
	s32 *sync_size,
	int *resync_sgs)
	{
	int tcp_payload_offset = skb_transport_offset(skb) + tcp_hdrlen(skb);
	int payload_len = skb->len - tcp_payload_offset;
	u32 tcp_seq = ntohl(tcp_hdr(skb)->seq);
	struct tls_record_info *record;
	unsigned long flags;
	int remaining;
	int i;

	spin_lock_irqsave(&ctx->lock, flags);
	record = tls_get_record(ctx, tcp_seq, rcd_sn);
	if (!record) {
	spin_unlock_irqrestore(&ctx->lock, flags);
	return -EINVAL;
	}

	*sync_size = tcp_seq - tls_record_start_seq(record);
	if (*sync_size < 0) {
	int is_start_marker = tls_record_is_start_marker(record);

	spin_unlock_irqrestore(&ctx->lock, flags);
	/* This should only occur if the relevant record was
	* already acked. In that case it should be ok
	* to drop the packet and avoid retransmission.
	*
	* There is a corner case where the packet contains
	* both an acked and a non-acked record.
	* We currently don't handle that case and rely
	* on TCP to retranmit a packet that doesn't contain
	* already acked payload.
	*/
	if (!is_start_marker)
	*sync_size = 0;
	return -EINVAL;
	}

	remaining = *sync_size;
	for (i = 0; remaining > 0; i++) {
	skb_frag_t *frag = &record->frags[i];

	__skb_frag_ref(frag);
	sg_set_page(sg_in + i, skb_frag_page(frag),
	skb_frag_size(frag), skb_frag_off(frag));

	remaining -= skb_frag_size(frag);

	if (remaining < 0)
	sg_in[i].length += remaining;
	}
	*resync_sgs = i;

	spin_unlock_irqrestore(&ctx->lock, flags);
	if (skb_to_sgvec(skb, &sg_in[i], tcp_payload_offset, payload_len) < 0)
	return -EINVAL;

	return 0;
	}

	static void fill_sg_out(struct scatterlist sg_out[3], void *buf,
	struct tls_context *tls_ctx,
	struct sk_buff *nskb,
	int tcp_payload_offset,
	int payload_len,
	int sync_size,
	void *dummy_buf)
	{
	sg_set_buf(&sg_out[0], dummy_buf, sync_size);
	sg_set_buf(&sg_out[1], nskb->data + tcp_payload_offset, payload_len);
	/* Add room for authentication tag produced by crypto */
	dummy_buf += sync_size;
	sg_set_buf(&sg_out[2], dummy_buf, TLS_CIPHER_AES_GCM_128_TAG_SIZE);
	}

	static struct sk_buff tls_enc_skb(struct tls_context tls_ctx,
	struct scatterlist sg_out[3],
	struct scatterlist *sg_in,
	struct sk_buff *skb,
	s32 sync_size, u64 rcd_sn)
	{
	int tcp_payload_offset = skb_transport_offset(skb) + tcp_hdrlen(skb);
	struct tls_offload_context_tx *ctx = tls_offload_ctx_tx(tls_ctx);
	int payload_len = skb->len - tcp_payload_offset;
	void buf, iv, aad, dummy_buf;
	struct aead_request *aead_req;
	struct sk_buff *nskb = NULL;
	int buf_len;

	aead_req = tls_alloc_aead_request(ctx->aead_send, GFP_ATOMIC);
	if (!aead_req)
	return NULL;

	buf_len = TLS_CIPHER_AES_GCM_128_SALT_SIZE +
	TLS_CIPHER_AES_GCM_128_IV_SIZE +
	TLS_AAD_SPACE_SIZE +
	sync_size +
	TLS_CIPHER_AES_GCM_128_TAG_SIZE;
	buf = kmalloc(buf_len, GFP_ATOMIC);
	if (!buf)
	goto free_req;

	iv = buf;
	memcpy(iv, tls_ctx->crypto_send.aes_gcm_128.salt,
	TLS_CIPHER_AES_GCM_128_SALT_SIZE);
	aad = buf + TLS_CIPHER_AES_GCM_128_SALT_SIZE +
	TLS_CIPHER_AES_GCM_128_IV_SIZE;
	dummy_buf = aad + TLS_AAD_SPACE_SIZE;

	nskb = alloc_skb(skb_headroom(skb) + skb->len, GFP_ATOMIC);
	if (!nskb)
	goto free_buf;

	skb_reserve(nskb, skb_headroom(skb));

	fill_sg_out(sg_out, buf, tls_ctx, nskb, tcp_payload_offset,
	payload_len, sync_size, dummy_buf);

	if (tls_enc_records(aead_req, ctx->aead_send, sg_in, sg_out, aad, iv,
	rcd_sn, sync_size + payload_len,
	&tls_ctx->prot_info) < 0)
	goto free_nskb;

	complete_skb(nskb, skb, tcp_payload_offset);

	/* validate_xmit_skb_list assumes that if the skb wasn't segmented
	* nskb->prev will point to the skb itself
	*/
	nskb->prev = nskb;

	free_buf:
	kfree(buf);
	free_req:
	kfree(aead_req);
	return nskb;
	free_nskb:
	kfree_skb(nskb);
	nskb = NULL;
	goto free_buf;
	}

	static struct sk_buff tls_sw_fallback(struct sock sk, struct sk_buff *skb)
	{
	int tcp_payload_offset = skb_transport_offset(skb) + tcp_hdrlen(skb);
	struct tls_context *tls_ctx = tls_get_ctx(sk);
	struct tls_offload_context_tx *ctx = tls_offload_ctx_tx(tls_ctx);
	int payload_len = skb->len - tcp_payload_offset;
	struct scatterlist *sg_in, sg_out[3];
	struct sk_buff *nskb = NULL;
	int sg_in_max_elements;
	int resync_sgs = 0;
	s32 sync_size = 0;
	u64 rcd_sn;

	/* worst case is:
	* MAX_SKB_FRAGS in tls_record_info
	* MAX_SKB_FRAGS + 1 in SKB head and frags.
	*/
	sg_in_max_elements = 2 * MAX_SKB_FRAGS + 1;

	if (!payload_len)
	return skb;

	sg_in = kmalloc_array(sg_in_max_elements, sizeof(*sg_in), GFP_ATOMIC);
	if (!sg_in)
	goto free_orig;

	sg_init_table(sg_in, sg_in_max_elements);
	sg_init_table(sg_out, ARRAY_SIZE(sg_out));

	if (fill_sg_in(sg_in, skb, ctx, &rcd_sn, &sync_size, &resync_sgs)) {
	/* bypass packets before kernel TLS socket option was set */
	if (sync_size < 0 && payload_len <= -sync_size)
	nskb = skb_get(skb);
	goto put_sg;
	}

	nskb = tls_enc_skb(tls_ctx, sg_out, sg_in, skb, sync_size, rcd_sn);

	put_sg:
	while (resync_sgs)
	put_page(sg_page(&sg_in[--resync_sgs]));
	kfree(sg_in);
	free_orig:
	if (nskb)
	consume_skb(skb);
	else
	kfree_skb(skb);
	return nskb;
	}

	struct sk_buff tls_validate_xmit_skb(struct sock sk,
	struct net_device *dev,
	struct sk_buff *skb)
	{
	if (dev == tls_get_ctx(sk)->netdev)
	return skb;

	return tls_sw_fallback(sk, skb);
	}
	EXPORT_SYMBOL_GPL(tls_validate_xmit_skb);

	struct sk_buff tls_encrypt_skb(struct sk_buff skb)
	{
	return tls_sw_fallback(skb->sk, skb);
	}
	EXPORT_SYMBOL_GPL(tls_encrypt_skb);

	int tls_sw_fallback_init(struct sock *sk,
	struct tls_offload_context_tx *offload_ctx,
	struct tls_crypto_info *crypto_info)
	{
	const u8 *key;
	int rc;

	offload_ctx->aead_send =
	crypto_alloc_aead("gcm(aes)", 0, CRYPTO_ALG_ASYNC);
	if (IS_ERR(offload_ctx->aead_send)) {
	rc = PTR_ERR(offload_ctx->aead_send);
	pr_err_ratelimited("crypto_alloc_aead failed rc=%d\n", rc);
	offload_ctx->aead_send = NULL;
	goto err_out;
	}

	key = ((struct tls12_crypto_info_aes_gcm_128 *)crypto_info)->key;

	rc = crypto_aead_setkey(offload_ctx->aead_send, key,
	TLS_CIPHER_AES_GCM_128_KEY_SIZE);
	if (rc)
	goto free_aead;

	rc = crypto_aead_setauthsize(offload_ctx->aead_send,
	TLS_CIPHER_AES_GCM_128_TAG_SIZE);
	if (rc)
	goto free_aead;

	return 0;
	free_aead:
	crypto_free_aead(offload_ctx->aead_send);
	err_out:
	return rc;
	}