Bluetooth: Add support for FCS option to L2CAP

Implement CRC16 check for L2CAP packets. FCS is used by Streaming Mode and
Enhanced Retransmission Mode and is a extra check for the packet content.

Using CRC16 is the default, L2CAP won't use FCS only when both side send
a "No FCS" request.

Initially based on a patch from Nathan Holstein <nathan@lampreynetworks.com>

Signed-off-by: Gustavo F. Padovan <gustavo@las.ic.unicamp.br>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

1 files changed, 95 insertions, 6 deletions

diff --git a/net/bluetooth/l2cap.c b/net/bluetooth/l2cap.c
index 7f835e761822..4c319003c290 100644
--- a/net/bluetooth/l2cap.c
+++ b/net/bluetooth/l2cap.c
@@ -41,6 +41,7 @@
 #include <linux/list.h>
 #include <linux/device.h>
 #include <linux/uaccess.h>
+#include <linux/crc16.h>
 #include <net/sock.h>
 
 #include <asm/system.h>
@@ -338,11 +339,14 @@ static inline int l2cap_send_sframe(struct l2cap_pinfo *pi, u16 control)
         struct sk_buff *skb;
         struct l2cap_hdr *lh;
         struct l2cap_conn *conn = pi->conn;
-        int count;
+        int count, hlen = L2CAP_HDR_SIZE + 2;
+
+        if (pi->fcs == L2CAP_FCS_CRC16)
+                hlen += 2;
 
         BT_DBG("pi %p, control 0x%2.2x", pi, control);
 
-        count = min_t(unsigned int, conn->mtu, L2CAP_HDR_SIZE + 2);
+        count = min_t(unsigned int, conn->mtu, hlen);
         control |= L2CAP_CTRL_FRAME_TYPE;
 
         skb = bt_skb_alloc(count, GFP_ATOMIC);
@@ -350,10 +354,15 @@ static inline int l2cap_send_sframe(struct l2cap_pinfo *pi, u16 control)
                 return -ENOMEM;
 
         lh = (struct l2cap_hdr *) skb_put(skb, L2CAP_HDR_SIZE);
-        lh->len = cpu_to_le16(2);
+        lh->len = cpu_to_le16(hlen - L2CAP_HDR_SIZE);
         lh->cid = cpu_to_le16(pi->dcid);
         put_unaligned_le16(control, skb_put(skb, 2));
 
+        if (pi->fcs == L2CAP_FCS_CRC16) {
+                u16 fcs = crc16(0, (u8 *)lh, count - 2);
+                put_unaligned_le16(fcs, skb_put(skb, 2));
+        }
+
         return hci_send_acl(pi->conn->hcon, skb, 0);
 }
 
@@ -1249,7 +1258,7 @@ static int l2cap_streaming_send(struct sock *sk)
 {
         struct sk_buff *skb, *tx_skb;
         struct l2cap_pinfo *pi = l2cap_pi(sk);
-        u16 control;
+        u16 control, fcs;
         int err;
 
         while ((skb = sk->sk_send_head)) {
@@ -1259,6 +1268,11 @@ static int l2cap_streaming_send(struct sock *sk)
                 control |= pi->next_tx_seq << L2CAP_CTRL_TXSEQ_SHIFT;
                 put_unaligned_le16(control, tx_skb->data + L2CAP_HDR_SIZE);
 
+                if (l2cap_pi(sk)->fcs == L2CAP_FCS_CRC16) {
+                        fcs = crc16(0, (u8 *)tx_skb->data, tx_skb->len - 2);
+                        put_unaligned_le16(fcs, tx_skb->data + tx_skb->len - 2);
+                }
+
                 err = l2cap_do_send(sk, tx_skb);
                 if (err < 0) {
                         l2cap_send_disconn_req(pi->conn, sk);
@@ -1282,7 +1296,7 @@ static int l2cap_ertm_send(struct sock *sk)
 {
         struct sk_buff *skb, *tx_skb;
         struct l2cap_pinfo *pi = l2cap_pi(sk);
-        u16 control;
+        u16 control, fcs;
         int err;
 
         if (pi->conn_state & L2CAP_CONN_WAIT_F)
@@ -1305,6 +1319,11 @@ static int l2cap_ertm_send(struct sock *sk)
                 put_unaligned_le16(control, tx_skb->data + L2CAP_HDR_SIZE);
 
 
+                if (l2cap_pi(sk)->fcs == L2CAP_FCS_CRC16) {
+                        fcs = crc16(0, (u8 *)skb->data, tx_skb->len - 2);
+                        put_unaligned_le16(fcs, skb->data + tx_skb->len - 2);
+                }
+
                 err = l2cap_do_send(sk, tx_skb);
                 if (err < 0) {
                         l2cap_send_disconn_req(pi->conn, sk);
@@ -1428,6 +1447,9 @@ static struct sk_buff *l2cap_create_iframe_pdu(struct sock *sk, struct msghdr *m
         if (sdulen)
                 hlen += 2;
 
+        if (l2cap_pi(sk)->fcs == L2CAP_FCS_CRC16)
+                hlen += 2;
+
         count = min_t(unsigned int, (conn->mtu - hlen), len);
         skb = bt_skb_send_alloc(sk, count + hlen,
                         msg->msg_flags & MSG_DONTWAIT, &err);
@@ -1448,6 +1470,9 @@ static struct sk_buff *l2cap_create_iframe_pdu(struct sock *sk, struct msghdr *m
                 return ERR_PTR(err);
         }
 
+        if (l2cap_pi(sk)->fcs == L2CAP_FCS_CRC16)
+                put_unaligned_le16(0, skb_put(skb, 2));
+
         bt_cb(skb)->retries = 0;
         return skb;
 }
@@ -1633,6 +1658,7 @@ static int l2cap_sock_setsockopt_old(struct socket *sock, int optname, char __us
                 opts.omtu     = l2cap_pi(sk)->omtu;
                 opts.flush_to = l2cap_pi(sk)->flush_to;
                 opts.mode     = l2cap_pi(sk)->mode;
+                opts.fcs      = l2cap_pi(sk)->fcs;
 
                 len = min_t(unsigned int, sizeof(opts), optlen);
                 if (copy_from_user((char *) &opts, optval, len)) {
@@ -1643,6 +1669,7 @@ static int l2cap_sock_setsockopt_old(struct socket *sock, int optname, char __us
                 l2cap_pi(sk)->imtu = opts.imtu;
                 l2cap_pi(sk)->omtu = opts.omtu;
                 l2cap_pi(sk)->mode = opts.mode;
+                l2cap_pi(sk)->fcs  = opts.fcs;
                 break;
 
         case L2CAP_LM:
@@ -1756,6 +1783,7 @@ static int l2cap_sock_getsockopt_old(struct socket *sock, int optname, char __us
                 opts.omtu     = l2cap_pi(sk)->omtu;
                 opts.flush_to = l2cap_pi(sk)->flush_to;
                 opts.mode     = l2cap_pi(sk)->mode;
+                opts.fcs      = l2cap_pi(sk)->fcs;
 
                 len = min_t(unsigned int, len, sizeof(opts));
                 if (copy_to_user(optval, (char *) &opts, len))
@@ -2154,6 +2182,15 @@ done:
 
                 l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC,
                                         sizeof(rfc), (unsigned long) &rfc);
+
+                if (!(pi->conn->feat_mask & L2CAP_FEAT_FCS))
+                        break;
+
+                if (pi->fcs == L2CAP_FCS_NONE ||
+                                pi->conf_state & L2CAP_CONF_NO_FCS_RECV) {
+                        pi->fcs = L2CAP_FCS_NONE;
+                        l2cap_add_conf_opt(&ptr, L2CAP_CONF_FCS, 1, pi->fcs);
+                }
                 break;
 
         case L2CAP_MODE_STREAMING:
@@ -2166,6 +2203,15 @@ done:
 
                 l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC,
                                         sizeof(rfc), (unsigned long) &rfc);
+
+                if (!(pi->conn->feat_mask & L2CAP_FEAT_FCS))
+                        break;
+
+                if (pi->fcs == L2CAP_FCS_NONE ||
+                                pi->conf_state & L2CAP_CONF_NO_FCS_RECV) {
+                        pi->fcs = L2CAP_FCS_NONE;
+                        l2cap_add_conf_opt(&ptr, L2CAP_CONF_FCS, 1, pi->fcs);
+                }
                 break;
         }
 
@@ -2217,6 +2263,12 @@ static int l2cap_parse_conf_req(struct sock *sk, void *data)
                                 memcpy(&rfc, (void *) val, olen);
                         break;
 
+                case L2CAP_CONF_FCS:
+                        if (val == L2CAP_FCS_NONE)
+                                pi->conf_state |= L2CAP_CONF_NO_FCS_RECV;
+
+                        break;
+
                 default:
                         if (hint)
                                 break;
@@ -2638,6 +2690,10 @@ static inline int l2cap_config_req(struct l2cap_conn *conn, struct l2cap_cmd_hdr
                 goto unlock;
 
         if (l2cap_pi(sk)->conf_state & L2CAP_CONF_INPUT_DONE) {
+                if (!(l2cap_pi(sk)->conf_state & L2CAP_CONF_NO_FCS_RECV)
+                                || l2cap_pi(sk)->fcs != L2CAP_FCS_NONE)
+                        l2cap_pi(sk)->fcs = L2CAP_FCS_CRC16;
+
                 sk->sk_state = BT_CONNECTED;
                 l2cap_pi(sk)->next_tx_seq = 0;
                 l2cap_pi(sk)->expected_ack_seq = 0;
@@ -2722,6 +2778,10 @@ static inline int l2cap_config_rsp(struct l2cap_conn *conn, struct l2cap_cmd_hdr
         l2cap_pi(sk)->conf_state |= L2CAP_CONF_INPUT_DONE;
 
         if (l2cap_pi(sk)->conf_state & L2CAP_CONF_OUTPUT_DONE) {
+                if (!(l2cap_pi(sk)->conf_state & L2CAP_CONF_NO_FCS_RECV)
+                                || l2cap_pi(sk)->fcs != L2CAP_FCS_NONE)
+                        l2cap_pi(sk)->fcs = L2CAP_FCS_CRC16;
+
                 sk->sk_state = BT_CONNECTED;
                 l2cap_pi(sk)->expected_tx_seq = 0;
                 l2cap_pi(sk)->num_to_ack = 0;
@@ -2809,7 +2869,8 @@ static inline int l2cap_information_req(struct l2cap_conn *conn, struct l2cap_cm
                 rsp->type   = cpu_to_le16(L2CAP_IT_FEAT_MASK);
                 rsp->result = cpu_to_le16(L2CAP_IR_SUCCESS);
                 if (enable_ertm)
-                        feat_mask |= L2CAP_FEAT_ERTM | L2CAP_FEAT_STREAMING;
+                        feat_mask |= L2CAP_FEAT_ERTM | L2CAP_FEAT_STREAMING
+                                                         | L2CAP_FEAT_FCS;
                 put_unaligned(cpu_to_le32(feat_mask), (__le32 *) rsp->data);
                 l2cap_send_cmd(conn, cmd->ident,
                                         L2CAP_INFO_RSP, sizeof(buf), buf);
@@ -2961,6 +3022,22 @@ static inline void l2cap_sig_channel(struct l2cap_conn *conn, struct sk_buff *sk
         kfree_skb(skb);
 }
 
+static int l2cap_check_fcs(struct l2cap_pinfo *pi,  struct sk_buff *skb)
+{
+        u16 our_fcs, rcv_fcs;
+        int hdr_size = L2CAP_HDR_SIZE + 2;
+
+        if (pi->fcs == L2CAP_FCS_CRC16) {
+                skb_trim(skb, skb->len - 2);
+                rcv_fcs = get_unaligned_le16(skb->data + skb->len);
+                our_fcs = crc16(0, skb->data - hdr_size, skb->len + hdr_size);
+
+                if (our_fcs != rcv_fcs)
+                        return -EINVAL;
+        }
+        return 0;
+}
+
 static int l2cap_sar_reassembly_sdu(struct sock *sk, struct sk_buff *skb, u16 control)
 {
         struct l2cap_pinfo *pi = l2cap_pi(sk);
@@ -3174,6 +3251,9 @@ static inline int l2cap_data_channel(struct l2cap_conn *conn, u16 cid, struct sk
                 if (__is_sar_start(control))
                         len -= 2;
 
+                if (pi->fcs == L2CAP_FCS_CRC16)
+                        len -= 2;
+
                 /*
                  * We can just drop the corrupted I-frame here.
                  * Receiver will miss it and start proper recovery
@@ -3182,6 +3262,9 @@ static inline int l2cap_data_channel(struct l2cap_conn *conn, u16 cid, struct sk
                 if (len > L2CAP_DEFAULT_MAX_PDU_SIZE)
                         goto drop;
 
+                if (l2cap_check_fcs(pi, skb))
+                        goto drop;
+
                 if (__is_iframe(control))
                         err = l2cap_data_channel_iframe(sk, control, skb);
                 else
@@ -3199,9 +3282,15 @@ static inline int l2cap_data_channel(struct l2cap_conn *conn, u16 cid, struct sk
                 if (__is_sar_start(control))
                         len -= 2;
 
+                if (pi->fcs == L2CAP_FCS_CRC16)
+                        len -= 2;
+
                 if (len > L2CAP_DEFAULT_MAX_PDU_SIZE || __is_sframe(control))
                         goto drop;
 
+                if (l2cap_check_fcs(pi, skb))
+                        goto drop;
+
                 tx_seq = __get_txseq(control);
 
                 if (pi->expected_tx_seq == tx_seq)