rxrpc: Don't reserve security header in Tx DATA skbuff

Insert the security header into the skbuff representing a DATA packet to be
transmitted rather than using skb_reserve() when the packet is allocated.
This makes it easier to apply crypto that spans the security header and the
data, particularly in the upcoming RxGK class where we have a common
encrypt-and-checksum function that is used in a number of circumstances.

Signed-off-by: David Howells <dhowells@redhat.com>

net/rxrpc/ar-internal.h

@@ -236,10 +236,7 @@ struct rxrpc_security {
 
 
 	/* impose security on a packet */
-	int (*secure_packet)(struct rxrpc_call *,
-			     struct sk_buff *,
-			     size_t,
-			     void *);
+	int (*secure_packet)(struct rxrpc_call *, struct sk_buff *, size_t);
 
 	/* verify the security on a received packet */
 	int (*verify_packet)(struct rxrpc_call *, struct sk_buff *,

net/rxrpc/insecure.c

@@ -14,10 +14,8 @@ static int none_init_connection_security(struct rxrpc_connection *conn,
 	return 0;
 }
 
-static int none_secure_packet(struct rxrpc_call *call,
-			      struct sk_buff *skb,
-			      size_t data_size,
-			      void *sechdr)
+static int none_secure_packet(struct rxrpc_call *call, struct sk_buff *skb,
+			      size_t data_size)
 {
 	return 0;
 }

net/rxrpc/rxkad.c

@@ -230,9 +230,7 @@ static void rxkad_free_call_crypto(struct rxrpc_call *call)
  * partially encrypt a packet (level 1 security)
  */
 static int rxkad_secure_packet_auth(const struct rxrpc_call *call,
-				    struct sk_buff *skb,
-				    u32 data_size,
-				    void *sechdr,
+				    struct sk_buff *skb, u32 data_size,
 				    struct skcipher_request *req)
 {
 	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
@@ -247,12 +245,12 @@ static int rxkad_secure_packet_auth(const struct rxrpc_call *call,
 	data_size |= (u32)check << 16;
 
 	hdr.data_size = htonl(data_size);
-	memcpy(sechdr, &hdr, sizeof(hdr));
+	memcpy(skb->head, &hdr, sizeof(hdr));
 
 	/* start the encryption afresh */
 	memset(&iv, 0, sizeof(iv));
 
-	sg_init_one(&sg, sechdr, 8);
+	sg_init_one(&sg, skb->head, 8);
 	skcipher_request_set_sync_tfm(req, call->conn->cipher);
 	skcipher_request_set_callback(req, 0, NULL, NULL);
 	skcipher_request_set_crypt(req, &sg, &sg, 8, iv.x);
@@ -269,7 +267,6 @@ static int rxkad_secure_packet_auth(const struct rxrpc_call *call,
 static int rxkad_secure_packet_encrypt(const struct rxrpc_call *call,
 				       struct sk_buff *skb,
 				       u32 data_size,
-				       void *sechdr,
 				       struct skcipher_request *req)
 {
 	const struct rxrpc_key_token *token;
@@ -289,13 +286,13 @@ static int rxkad_secure_packet_encrypt(const struct rxrpc_call *call,
 
 	rxkhdr.data_size = htonl(data_size | (u32)check << 16);
 	rxkhdr.checksum = 0;
-	memcpy(sechdr, &rxkhdr, sizeof(rxkhdr));
+	memcpy(skb->head, &rxkhdr, sizeof(rxkhdr));
 
 	/* encrypt from the session key */
 	token = call->conn->params.key->payload.data[0];
 	memcpy(&iv, token->kad->session_key, sizeof(iv));
 
-	sg_init_one(&sg[0], sechdr, sizeof(rxkhdr));
+	sg_init_one(&sg[0], skb->head, sizeof(rxkhdr));
 	skcipher_request_set_sync_tfm(req, call->conn->cipher);
 	skcipher_request_set_callback(req, 0, NULL, NULL);
 	skcipher_request_set_crypt(req, &sg[0], &sg[0], sizeof(rxkhdr), iv.x);
@@ -310,7 +307,7 @@ static int rxkad_secure_packet_encrypt(const struct rxrpc_call *call,
 	len &= ~(call->conn->size_align - 1);
 
 	sg_init_table(sg, ARRAY_SIZE(sg));
-	err = skb_to_sgvec(skb, sg, 0, len);
+	err = skb_to_sgvec(skb, sg, 8, len);
 	if (unlikely(err < 0))
 		goto out;
 	skcipher_request_set_crypt(req, sg, sg, len, iv.x);
@@ -329,8 +326,7 @@ out:
  */
 static int rxkad_secure_packet(struct rxrpc_call *call,
 			       struct sk_buff *skb,
-			       size_t data_size,
-			       void *sechdr)
+			       size_t data_size)
 {
 	struct rxrpc_skb_priv *sp;
 	struct skcipher_request	*req;
@@ -383,12 +379,10 @@ static int rxkad_secure_packet(struct rxrpc_call *call,
 		ret = 0;
 		break;
 	case RXRPC_SECURITY_AUTH:
-		ret = rxkad_secure_packet_auth(call, skb, data_size, sechdr,
-					       req);
+		ret = rxkad_secure_packet_auth(call, skb, data_size, req);
 		break;
 	case RXRPC_SECURITY_ENCRYPT:
-		ret = rxkad_secure_packet_encrypt(call, skb, data_size,
-						  sechdr, req);
+		ret = rxkad_secure_packet_encrypt(call, skb, data_size, req);
 		break;
 	default:
 		ret = -EPERM;

net/rxrpc/sendmsg.c

@@ -372,8 +372,7 @@ static int rxrpc_send_data(struct rxrpc_sock *rx,
 			ASSERTCMP(skb->mark, ==, 0);
 
 			_debug("HS: %u", call->conn->security_size);
-			skb_reserve(skb, call->conn->security_size);
-			skb->len += call->conn->security_size;
+			__skb_put(skb, call->conn->security_size);
 
 			sp->remain = chunk;
 			if (sp->remain > skb_tailroom(skb))
@@ -446,8 +445,7 @@ static int rxrpc_send_data(struct rxrpc_sock *rx,
 				 call->tx_winsize)
 				sp->hdr.flags |= RXRPC_MORE_PACKETS;
 
-			ret = call->security->secure_packet(
-				call, skb, skb->mark, skb->head);
+			ret = call->security->secure_packet(call, skb, skb->mark);
 			if (ret < 0)
 				goto out;