tls: rx: strp: factor out copying skb data

We'll need to copy input skbs individually in the next patch.
Factor that code out (without assuming we're copying a full record).
Tested-by: Shai Amiram <samiram@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tls/tls_strp.c

@@ -34,31 +34,44 @@ static void tls_strp_anchor_free(struct tls_strparser *strp)
 	strp->anchor = NULL;
 }
 
-/* Create a new skb with the contents of input copied to its page frags */
-static struct sk_buff *tls_strp_msg_make_copy(struct tls_strparser *strp)
+static struct sk_buff *
+tls_strp_skb_copy(struct tls_strparser *strp, struct sk_buff *in_skb,
+		  int offset, int len)
 {
-	struct strp_msg *rxm;
 	struct sk_buff *skb;
-	int i, err, offset;
+	int i, err;
 
-	skb = alloc_skb_with_frags(0, strp->stm.full_len, TLS_PAGE_ORDER,
+	skb = alloc_skb_with_frags(0, len, TLS_PAGE_ORDER,
 				   &err, strp->sk->sk_allocation);
 	if (!skb)
 		return NULL;
 
-	offset = strp->stm.offset;
 	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
 		skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
 
-		WARN_ON_ONCE(skb_copy_bits(strp->anchor, offset,
+		WARN_ON_ONCE(skb_copy_bits(in_skb, offset,
 					   skb_frag_address(frag),
 					   skb_frag_size(frag)));
 		offset += skb_frag_size(frag);
 	}
 
-	skb->len = strp->stm.full_len;
-	skb->data_len = strp->stm.full_len;
-	skb_copy_header(skb, strp->anchor);
+	skb->len = len;
+	skb->data_len = len;
+	skb_copy_header(skb, in_skb);
+	return skb;
+}
+
+/* Create a new skb with the contents of input copied to its page frags */
+static struct sk_buff *tls_strp_msg_make_copy(struct tls_strparser *strp)
+{
+	struct strp_msg *rxm;
+	struct sk_buff *skb;
+
+	skb = tls_strp_skb_copy(strp, strp->anchor, strp->stm.offset,
+				strp->stm.full_len);
+	if (!skb)
+		return NULL;
+
 	rxm = strp_msg(skb);
 	rxm->offset = 0;
 	return skb;