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From: Pauli Virtanen <pav@iki.fi>
To: linux-bluetooth@vger.kernel.org
Cc: Pauli Virtanen <pav@iki.fi>
Subject: [PATCH BlueZ v2 7/9] bthost: handle client L2CAP conn in LE credit based mode
Date: Thu, 14 Mar 2024 20:21:16 +0200
Message-ID: <256516aa4a422430d28c4ac32666caa25f809430.1710440408.git.pav@iki.fi>
In-Reply-To: <cover.1710440408.git.pav@iki.fi>
References: <cover.1710440408.git.pav@iki.fi>
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Allow bthost hooks to receive data from L2CAP LE credit based
connections. Handle LE credit header when receiving, and reassemble
received SDU.

Handle L2CAP LE credit header also in bthost_send_cid.
---
 emulator/bthost.c | 205 ++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 180 insertions(+), 25 deletions(-)

diff --git a/emulator/bthost.c b/emulator/bthost.c
index 8c40fce90..8616bf715 100644
--- a/emulator/bthost.c
+++ b/emulator/bthost.c
@@ -162,11 +162,21 @@ struct btconn {
 	void *recv_data;
 };
 
+enum l2cap_mode {
+	L2CAP_MODE_OTHER,
+	L2CAP_MODE_LE_CRED,
+	L2CAP_MODE_LE_ENH_CRED,
+};
+
 struct l2conn {
+	struct l2conn *next;
 	uint16_t scid;
 	uint16_t dcid;
 	uint16_t psm;
-	struct l2conn *next;
+	enum l2cap_mode mode;
+	uint16_t data_len;
+	uint16_t recv_len;
+	void *recv_data;
 };
 
 struct rcconn {
@@ -275,6 +285,7 @@ struct bthost *bthost_create(void)
 
 static void l2conn_free(struct l2conn *conn)
 {
+	free(conn->recv_data);
 	free(conn);
 }
 
@@ -360,6 +371,7 @@ static struct l2conn *bthost_add_l2cap_conn(struct bthost *bthost,
 	l2conn->psm = psm;
 	l2conn->scid = scid;
 	l2conn->dcid = dcid;
+	l2conn->mode = L2CAP_MODE_OTHER;
 
 	l2conn->next = conn->l2conns;
 	conn->l2conns = l2conn;
@@ -415,6 +427,19 @@ static struct l2conn *btconn_find_l2cap_conn_by_scid(struct btconn *conn,
 	return NULL;
 }
 
+static struct l2conn *btconn_find_l2cap_conn_by_dcid(struct btconn *conn,
+								uint16_t dcid)
+{
+	struct l2conn *l2conn;
+
+	for (l2conn = conn->l2conns; l2conn != NULL; l2conn = l2conn->next) {
+		if (l2conn->dcid == dcid)
+			return l2conn;
+	}
+
+	return NULL;
+}
+
 static struct l2cap_conn_cb_data *bthost_find_l2cap_cb_by_psm(
 					struct bthost *bthost, uint16_t psm)
 {
@@ -609,14 +634,24 @@ static void send_iov(struct bthost *bthost, uint16_t handle, uint16_t cid,
 }
 
 static void send_acl(struct bthost *bthost, uint16_t handle, uint16_t cid,
-						const void *data, uint16_t len)
+				bool sdu_hdr, const void *data, uint16_t len)
 {
-	struct iovec iov;
+	struct iovec iov[2];
+	uint16_t sdu;
+	int num = 0;
+
+	if (sdu_hdr) {
+		sdu = cpu_to_le16(len);
+		iov[num].iov_base = &sdu;
+		iov[num].iov_len = sizeof(sdu);
+		num++;
+	}
 
-	iov.iov_base = (void *) data;
-	iov.iov_len = len;
+	iov[num].iov_base = (void *) data;
+	iov[num].iov_len = len;
+	num++;
 
-	send_iov(bthost, handle, cid, &iov, 1);
+	send_iov(bthost, handle, cid, iov, num);
 }
 
 static uint8_t l2cap_sig_send(struct bthost *bthost, struct btconn *conn,
@@ -711,12 +746,19 @@ void bthost_send_cid(struct bthost *bthost, uint16_t handle, uint16_t cid,
 					const void *data, uint16_t len)
 {
 	struct btconn *conn;
+	struct l2conn *l2conn;
+	bool sdu_hdr = false;
 
 	conn = bthost_find_conn(bthost, handle);
 	if (!conn)
 		return;
 
-	send_acl(bthost, handle, cid, data, len);
+	l2conn = btconn_find_l2cap_conn_by_dcid(conn, cid);
+	if (l2conn && (l2conn->mode == L2CAP_MODE_LE_CRED ||
+			l2conn->mode == L2CAP_MODE_LE_ENH_CRED))
+		sdu_hdr = true;
+
+	send_acl(bthost, handle, cid, sdu_hdr, data, len);
 }
 
 void bthost_send_cid_v(struct bthost *bthost, uint16_t handle, uint16_t cid,
@@ -1779,7 +1821,7 @@ static void rfcomm_sabm_send(struct bthost *bthost, struct btconn *conn,
 	cmd.length = RFCOMM_LEN8(0);
 	cmd.fcs = rfcomm_fcs2((uint8_t *)&cmd);
 
-	send_acl(bthost, conn->handle, l2conn->dcid, &cmd, sizeof(cmd));
+	send_acl(bthost, conn->handle, l2conn->dcid, false, &cmd, sizeof(cmd));
 }
 
 static bool l2cap_conn_rsp(struct bthost *bthost, struct btconn *conn,
@@ -2110,6 +2152,7 @@ static bool l2cap_le_conn_req(struct bthost *bthost, struct btconn *conn,
 				uint8_t ident, const void *data, uint16_t len)
 {
 	const struct bt_l2cap_pdu_le_conn_req *req = data;
+	struct l2cap_conn_cb_data *cb_data;
 	struct bt_l2cap_pdu_le_conn_rsp rsp;
 	uint16_t psm;
 
@@ -2124,7 +2167,8 @@ static bool l2cap_le_conn_req(struct bthost *bthost, struct btconn *conn,
 	rsp.mps = 23;
 	rsp.credits = 1;
 
-	if (bthost_find_l2cap_cb_by_psm(bthost, psm))
+	cb_data = bthost_find_l2cap_cb_by_psm(bthost, psm);
+	if (cb_data)
 		rsp.dcid = cpu_to_le16(conn->next_cid++);
 	else
 		rsp.result = cpu_to_le16(0x0002); /* PSM Not Supported */
@@ -2132,6 +2176,20 @@ static bool l2cap_le_conn_req(struct bthost *bthost, struct btconn *conn,
 	l2cap_sig_send(bthost, conn, BT_L2CAP_PDU_LE_CONN_RSP, ident, &rsp,
 								sizeof(rsp));
 
+	if (!rsp.result) {
+		struct l2conn *l2conn;
+
+		l2conn = bthost_add_l2cap_conn(bthost, conn,
+							le16_to_cpu(rsp.dcid),
+							le16_to_cpu(req->scid),
+							le16_to_cpu(psm));
+		l2conn->mode = L2CAP_MODE_LE_CRED;
+
+		if (cb_data && l2conn->psm == cb_data->psm && cb_data->func)
+			cb_data->func(conn->handle, l2conn->dcid,
+							cb_data->user_data);
+	}
+
 	return true;
 }
 
@@ -2139,11 +2197,14 @@ static bool l2cap_le_conn_rsp(struct bthost *bthost, struct btconn *conn,
 				uint8_t ident, const void *data, uint16_t len)
 {
 	const struct bt_l2cap_pdu_le_conn_rsp *rsp = data;
+	struct l2conn *l2conn;
 
 	if (len < sizeof(*rsp))
 		return false;
 	/* TODO add L2CAP connection before with proper PSM */
-	bthost_add_l2cap_conn(bthost, conn, 0, le16_to_cpu(rsp->dcid), 0);
+	l2conn = bthost_add_l2cap_conn(bthost, conn, 0,
+						le16_to_cpu(rsp->dcid), 0);
+	l2conn->mode = L2CAP_MODE_LE_CRED;
 
 	return true;
 }
@@ -2196,16 +2257,19 @@ static bool l2cap_ecred_conn_rsp(struct bthost *bthost, struct btconn *conn,
 		uint16_t scid[5];
 	} __attribute__ ((packed)) *rsp = data;
 	int num_scid, i;
+	struct l2conn *l2conn;
 
 	if (len < sizeof(*rsp))
 		return false;
 
 	num_scid = len / sizeof(*rsp->scid);
 
-	for (i = 0; i < num_scid; i++)
+	for (i = 0; i < num_scid; i++) {
 		/* TODO add L2CAP connection before with proper PSM */
-		bthost_add_l2cap_conn(bthost, conn, 0,
+		l2conn = bthost_add_l2cap_conn(bthost, conn, 0,
 				      le16_to_cpu(rsp->scid[i]), 0);
+		l2conn->mode = L2CAP_MODE_LE_ENH_CRED;
+	}
 
 
 	return true;
@@ -2333,7 +2397,7 @@ static void rfcomm_ua_send(struct bthost *bthost, struct btconn *conn,
 	cmd.length = RFCOMM_LEN8(0);
 	cmd.fcs = rfcomm_fcs2((uint8_t *)&cmd);
 
-	send_acl(bthost, conn->handle, l2conn->dcid, &cmd, sizeof(cmd));
+	send_acl(bthost, conn->handle, l2conn->dcid, false, &cmd, sizeof(cmd));
 }
 
 static void rfcomm_dm_send(struct bthost *bthost, struct btconn *conn,
@@ -2347,7 +2411,7 @@ static void rfcomm_dm_send(struct bthost *bthost, struct btconn *conn,
 	cmd.length = RFCOMM_LEN8(0);
 	cmd.fcs = rfcomm_fcs2((uint8_t *)&cmd);
 
-	send_acl(bthost, conn->handle, l2conn->dcid, &cmd, sizeof(cmd));
+	send_acl(bthost, conn->handle, l2conn->dcid, false, &cmd, sizeof(cmd));
 }
 
 static void rfcomm_sabm_recv(struct bthost *bthost, struct btconn *conn,
@@ -2636,12 +2700,97 @@ static void process_rfcomm(struct bthost *bthost, struct btconn *conn,
 	}
 }
 
+static void append_l2conn_data(struct bthost *bthost, struct l2conn *conn,
+				const void *data, uint16_t len)
+{
+	if (!conn->recv_data) {
+		bthost_debug(bthost, "Unexpected L2CAP SDU data: sCID 0x%4.4x ",
+								conn->scid);
+		return;
+	}
+
+	if (conn->recv_len + len > conn->data_len) {
+		bthost_debug(bthost, "Unexpected L2CAP SDU data: sCID 0x%4.4x ",
+								conn->scid);
+		return;
+	}
+
+	memcpy(conn->recv_data + conn->recv_len, data, len);
+	conn->recv_len += len;
+
+	bthost_debug(bthost, "L2CAP SDU data: %u/%u bytes", conn->recv_len,
+							conn->data_len);
+}
+
+static void free_l2conn_data(struct l2conn *conn)
+{
+	free(conn->recv_data);
+	conn->recv_data = NULL;
+	conn->recv_len = 0;
+	conn->data_len = 0;
+}
+
+static void new_l2conn_data(struct bthost *bthost, struct l2conn *conn,
+								uint16_t len)
+{
+	free(conn->recv_data);
+	conn->recv_data = malloc(len);
+	conn->recv_len = 0;
+	conn->data_len = len;
+}
+
+static bool process_l2cap_conn(struct bthost *bthost, struct btconn *conn,
+				struct l2conn *l2conn, struct iovec *data)
+{
+	struct bt_l2cap_pdu_le_flowctl_creds creds;
+	uint16_t sdu;
+
+	if (!l2conn)
+		return true;
+
+	switch (l2conn->mode) {
+	case L2CAP_MODE_LE_CRED:
+	case L2CAP_MODE_LE_ENH_CRED:
+		break;
+	case L2CAP_MODE_OTHER:
+		return true;
+	}
+
+	/* Credit-based flow control */
+
+	creds.cid = cpu_to_le16(l2conn->scid);
+	creds.credits = cpu_to_le16(1);
+	l2cap_sig_send(bthost, conn, BT_L2CAP_PDU_LE_FLOWCTL_CREDS, 0,
+							&creds, sizeof(creds));
+
+	if (!l2conn->data_len) {
+		if (!util_iov_pull_le16(data, &sdu)) {
+			free_l2conn_data(l2conn);
+			bthost_debug(bthost, "L2CAP invalid SDU");
+			return false;
+		}
+		new_l2conn_data(bthost, l2conn, sdu);
+	}
+
+	append_l2conn_data(bthost, l2conn, data->iov_base, data->iov_len);
+
+	if (l2conn->recv_len < l2conn->data_len)
+		return false;  /* SDU incomplete */
+
+	l2conn->data_len = 0;
+	data->iov_base = l2conn->recv_data;
+	data->iov_len = l2conn->recv_len;
+
+	return true;
+}
+
 static void process_l2cap(struct bthost *bthost, struct btconn *conn,
-					const void *data, uint16_t len)
+					const void *buf, uint16_t len)
 {
-	const struct bt_l2cap_hdr *l2_hdr = data;
+	const struct bt_l2cap_hdr *l2_hdr = buf;
 	struct cid_hook *hook;
 	struct l2conn *l2conn;
+	struct iovec data;
 	uint16_t cid, l2_len;
 
 	l2_len = le16_to_cpu(l2_hdr->len);
@@ -2654,31 +2803,37 @@ static void process_l2cap(struct bthost *bthost, struct btconn *conn,
 	bthost_debug(bthost, "L2CAP data: %u bytes", l2_len);
 
 	cid = le16_to_cpu(l2_hdr->cid);
+	l2conn = btconn_find_l2cap_conn_by_scid(conn, cid);
+
+	data.iov_base = (void *)l2_hdr->data;
+	data.iov_len = l2_len;
+
+	if (!process_l2cap_conn(bthost, conn, l2conn, &data))
+		return;
 
 	hook = find_cid_hook(conn, cid);
 	if (hook) {
-		hook->func(l2_hdr->data, l2_len, hook->user_data);
+		hook->func(data.iov_base, data.iov_len, hook->user_data);
 		return;
 	}
 
 	switch (cid) {
 	case 0x0001:
-		l2cap_sig(bthost, conn, l2_hdr->data, l2_len);
+		l2cap_sig(bthost, conn, data.iov_base, data.iov_len);
 		break;
 	case 0x0005:
-		l2cap_le_sig(bthost, conn, l2_hdr->data, l2_len);
+		l2cap_le_sig(bthost, conn, data.iov_base, data.iov_len);
 		break;
 	case 0x0006:
-		smp_data(conn->smp_data, l2_hdr->data, l2_len);
+		smp_data(conn->smp_data, data.iov_base, data.iov_len);
 		break;
 	case 0x0007:
-		smp_bredr_data(conn->smp_data, l2_hdr->data, l2_len);
+		smp_bredr_data(conn->smp_data, data.iov_base, data.iov_len);
 		break;
 	default:
-		l2conn = btconn_find_l2cap_conn_by_scid(conn, cid);
 		if (l2conn && l2conn->psm == 0x0003)
-			process_rfcomm(bthost, conn, l2conn, l2_hdr->data,
-								l2_len);
+			process_rfcomm(bthost, conn, l2conn, data.iov_base,
+								data.iov_len);
 		else
 			bthost_debug(bthost,
 					"Packet for unknown CID 0x%04x (%u)",
@@ -3494,7 +3649,7 @@ void bthost_send_rfcomm_data(struct bthost *bthost, uint16_t handle,
 	}
 
 	uih_frame[uih_len - 1] = rfcomm_fcs((void *)hdr);
-	send_acl(bthost, handle, rcconn->scid, uih_frame, uih_len);
+	send_acl(bthost, handle, rcconn->scid, false, uih_frame, uih_len);
 
 	free(uih_frame);
 }
-- 
2.44.0