[PATCH 2/4] Bluetooth: Add bt_skb_sendmmsg helper

[Luiz Augusto von Dentz <luiz.dentz@gmail.com>]

From: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

This works similarly to bt_skb_sendmsg but can split the msg into
multiple skb fragments which is useful for stream sockets.

Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
---
 include/net/bluetooth/bluetooth.h | 35 +++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/include/net/bluetooth/bluetooth.h b/include/net/bluetooth/bluetooth.h
index f858efcf9f40..96743e6e7a0a 100644
--- a/include/net/bluetooth/bluetooth.h
+++ b/include/net/bluetooth/bluetooth.h
@@ -446,6 +446,41 @@ static inline struct sk_buff *bt_skb_sendmsg(struct sock *sk,
 	return skb;
 }
 
+/* Similar to bt_skb_sendmsg but can split the msg into multiple fragments
+ * accourding to the MTU.
+ */
+static inline struct sk_buff *bt_skb_sendmmsg(struct sock *sk,
+					      struct msghdr *msg,
+					      size_t len, size_t mtu,
+					      size_t header, size_t footer)
+{
+	struct sk_buff *skb, **frag;
+	size_t size = min_t(size_t, len, mtu);
+
+	skb = bt_skb_sendmsg(sk, msg, size, header, footer);
+	if (IS_ERR_OR_NULL(skb))
+		return skb;
+
+	len -= size;
+	if (!len)
+		return skb;
+
+	/* Add remaining data over MTU as continuation fragments */
+	frag = &skb_shinfo(skb)->frag_list;
+	while (len) {
+		*frag = bt_skb_sendmsg(sk, msg, size, header, footer);
+		if (IS_ERR_OR_NULL(*frag)) {
+			kfree_skb(skb);
+			return *frag;
+		}
+
+		len -= (*frag)->len;
+		frag = &(*frag)->next;
+	}
+
+	return skb;
+}
+
 int bt_to_errno(u16 code);
 
 void hci_sock_set_flag(struct sock *sk, int nr);
-- 
2.31.1