Bluetooth: ISO: add socket option to report packet seqnum via CMSG

User applications need a way to track which ISO interval a given SDU
belongs to, to properly detect packet loss. All controllers do not set
timestamps, and it's not guaranteed user application receives all packet
reports (small socket buffer, or controller doesn't send all reports
like Intel AX210 is doing).

Add socket option BT_PKT_SEQNUM that enables reporting of received
packet ISO sequence number in BT_SCM_PKT_SEQNUM CMSG.

Use BT_PKT_SEQNUM == 22 for the socket option, as 21 was used earlier
for a removed experimental feature that never got into mainline.

Signed-off-by: Pauli Virtanen <[e-mail]>
Signed-off-by: Luiz Augusto von Dentz <[e-mail]>

include/net/bluetooth/bluetooth.h

···
 
 #define BT_ISO_BASE		20
 
+/* Socket option value 21 reserved */
+
+#define BT_PKT_SEQNUM		22
+
+#define BT_SCM_PKT_SEQNUM	0x05
+
 __printf(1, 2)
 void bt_info(const char *fmt, ...);
 __printf(1, 2)
···
 enum {
 	BT_SK_DEFER_SETUP,
 	BT_SK_SUSPEND,
-	BT_SK_PKT_STATUS
+	BT_SK_PKT_STATUS,
+	BT_SK_PKT_SEQNUM,
 };
 
 struct bt_sock_list {
···
 	u8 pkt_type;
 	u8 force_active;
 	u16 expect;
+	u16 pkt_seqnum;
 	u8 incoming:1;
 	u8 pkt_status:2;
 	union {
···
 
 #define hci_skb_pkt_type(skb) bt_cb((skb))->pkt_type
 #define hci_skb_pkt_status(skb) bt_cb((skb))->pkt_status
+#define hci_skb_pkt_seqnum(skb) bt_cb((skb))->pkt_seqnum
 #define hci_skb_expect(skb) bt_cb((skb))->expect
 #define hci_skb_opcode(skb) bt_cb((skb))->hci.opcode
 #define hci_skb_event(skb) bt_cb((skb))->hci.req_event

net/bluetooth/af_bluetooth.c

···
 			put_cmsg(msg, SOL_BLUETOOTH, BT_SCM_PKT_STATUS,
 				 sizeof(pkt_status), &pkt_status);
 		}
+
+		if (test_bit(BT_SK_PKT_SEQNUM, &bt_sk(sk)->flags)) {
+			u16 pkt_seqnum = hci_skb_pkt_seqnum(skb);
+
+			put_cmsg(msg, SOL_BLUETOOTH, BT_SCM_PKT_SEQNUM,
+				 sizeof(pkt_seqnum), &pkt_seqnum);
+		}
 	}
 
 	skb_free_datagram(sk, skb);

net/bluetooth/iso.c

···
 			clear_bit(BT_SK_PKT_STATUS, &bt_sk(sk)->flags);
 		break;
 
+	case BT_PKT_SEQNUM:
+		err = copy_safe_from_sockptr(&opt, sizeof(opt), optval, optlen);
+		if (err)
+			break;
+
+		if (opt)
+			set_bit(BT_SK_PKT_SEQNUM, &bt_sk(sk)->flags);
+		else
+			clear_bit(BT_SK_PKT_SEQNUM, &bt_sk(sk)->flags);
+		break;
+
 	case BT_ISO_QOS:
 		if (sk->sk_state != BT_OPEN && sk->sk_state != BT_BOUND &&
 		    sk->sk_state != BT_CONNECT2 &&
···
 void iso_recv(struct hci_conn *hcon, struct sk_buff *skb, u16 flags)
 {
 	struct iso_conn *conn = hcon->iso_data;
-	__u16 pb, ts, len;
+	__u16 pb, ts, len, sn;
 
 	if (!conn)
 		goto drop;
···
 				goto drop;
 			}
 
+			sn = __le16_to_cpu(hdr->sn);
 			len = __le16_to_cpu(hdr->slen);
 		} else {
 			struct hci_iso_data_hdr *hdr;
···
 				goto drop;
 			}
 
+			sn = __le16_to_cpu(hdr->sn);
 			len = __le16_to_cpu(hdr->slen);
 		}
 
 		flags  = hci_iso_data_flags(len);
 		len    = hci_iso_data_len(len);
 
-		BT_DBG("Start: total len %d, frag len %d flags 0x%4.4x", len,
-		       skb->len, flags);
+		BT_DBG("Start: total len %d, frag len %d flags 0x%4.4x sn %d",
+		       len, skb->len, flags, sn);
 
 		if (len == skb->len) {
 			/* Complete frame received */
 			hci_skb_pkt_status(skb) = flags & 0x03;
+			hci_skb_pkt_seqnum(skb) = sn;
 			iso_recv_frame(conn, skb);
 			return;
 		}
···
 			goto drop;
 
 		hci_skb_pkt_status(conn->rx_skb) = flags & 0x03;
+		hci_skb_pkt_seqnum(conn->rx_skb) = sn;
 		skb_copy_from_linear_data(skb, skb_put(conn->rx_skb, skb->len),
 					  skb->len);
 		conn->rx_len = len - skb->len;