Re: [PATCH 08/17] can: add ISO 15765-2:2016 transport protocol

+/*
+ * Remark on CAN_ISOTP_DEFAULT_RECV_* values:
+ *
+ * We can strongly assume, that the Linux Kernel implementation of
+ * CAN_ISOTP is capable to run with BS=0, STmin=0 and WFTmax=0.
+ * But as we like to be able to behave as a commonly available ECU,
+ * these default settings can be changed via sockopts.
+ * For that reason the STmin value is intentionally _not_ checked for
+ * consistency and copied directly into the flow control (FC) frame.
+ *

+ */
+
+#endif /* !_UAPI_CAN_ISOTP_H */

diff --git a/net/can/Kconfig b/net/can/Kconfig
index 25436a715db3..021fe03a8ed6 100644
--- a/net/can/Kconfig
+++ b/net/can/Kconfig

@@ -55,6 +55,19 @@ config CAN_GW
 
 source "net/can/j1939/Kconfig"
 
+config CAN_ISOTP
+	tristate "ISO 15765-2:2016 CAN transport protocol"
+	default y

+	help
+	  CAN Transport Protocols offer support for segmented Point-to-Point
+	  communication between CAN nodes via two defined CAN Identifiers.
+	  As CAN frames can only transport a small amount of data bytes
+	  (max. 8 bytes for 'classic' CAN and max. 64 bytes for CAN FD) this
+	  segmentation is needed to transport longer PDUs as needed e.g. for
+	  vehicle diagnosis (UDS, ISO 14229) or IP-over-CAN traffic.
+	  This protocol driver implements data transfers according to
+	  ISO 15765-2:2016 for 'classic' CAN and CAN FD frame types.
+
 source "drivers/net/can/Kconfig"
 
 endif

+static enum hrtimer_restart isotp_tx_timer_handler(struct hrtimer *hrtimer)
+{
+	struct isotp_sock *so = container_of(hrtimer, struct isotp_sock,
+					     txtimer);
+	struct sock *sk = &so->sk;
+	struct sk_buff *skb;
+	struct net_device *dev;
+	struct canfd_frame *cf;
+	enum hrtimer_restart restart = HRTIMER_NORESTART;
+	int can_send_ret;
+	int ae = (so->opt.flags & CAN_ISOTP_EXTEND_ADDR) ? 1 : 0;
+
+	switch (so->tx.state) {
+	case ISOTP_WAIT_FC:
+	case ISOTP_WAIT_FIRST_FC:
+
+		/* we did not get any flow control frame in time */
+
+		/* report 'communication error on send' */
+		sk->sk_err = ECOMM;
+		if (!sock_flag(sk, SOCK_DEAD))
+			sk->sk_error_report(sk);
+
+		/* reset tx state */
+		so->tx.state = ISOTP_IDLE;
+		wake_up_interruptible(&so->wait);
+		break;
+
+	case ISOTP_SENDING:
+
+		/* push out the next segmented pdu */
+		dev = dev_get_by_index(sock_net(sk), so->ifindex);
+		if (!dev)
+			break;
+
+isotp_tx_burst:
+		skb = alloc_skb(so->ll.mtu + sizeof(struct can_skb_priv),
+				gfp_any());

+		if (!skb) {
+			dev_put(dev);
+			break;
+		}
+
+		can_skb_reserve(skb);
+		can_skb_prv(skb)->ifindex = dev->ifindex;
+		can_skb_prv(skb)->skbcnt = 0;
+
+		cf = (struct canfd_frame *)skb->data;
+		skb_put(skb, so->ll.mtu);
+
+		/* create consecutive frame */
+		isotp_fill_dataframe(cf, so, ae, 0);
+
+		/* place consecutive frame N_PCI in appropriate index */
+		cf->data[ae] = N_PCI_CF | so->tx.sn++;
+		so->tx.sn %= 16;
+		so->tx.bs++;
+
+		if (so->ll.mtu == CANFD_MTU)
+			cf->flags = so->ll.tx_flags;
+
+		skb->dev = dev;
+		can_skb_set_owner(skb, sk);
+
+		can_send_ret = can_send(skb, 1);
+		if (can_send_ret)
+			printk_once(KERN_NOTICE "can-isotp: %s: can_send_ret %d\n",
+				    __func__, can_send_ret);

+
+		if (so->tx.idx >= so->tx.len) {
+			/* we are done */
+			so->tx.state = ISOTP_IDLE;
+			dev_put(dev);
+			wake_up_interruptible(&so->wait);
+			break;
+		}
+
+		if (so->txfc.bs && so->tx.bs >= so->txfc.bs) {
+			/* stop and wait for FC */
+			so->tx.state = ISOTP_WAIT_FC;
+			dev_put(dev);
+			hrtimer_set_expires(&so->txtimer,
+					    ktime_add(ktime_get(),
+						      ktime_set(1, 0)));
+			restart = HRTIMER_RESTART;
+			break;
+		}
+
+		/* no gap between data frames needed => use burst mode */
+		if (!so->tx_gap)
+			goto isotp_tx_burst;
+
+		/* start timer to send next data frame with correct delay */
+		dev_put(dev);
+		hrtimer_set_expires(&so->txtimer,
+				    ktime_add(ktime_get(), so->tx_gap));
+		restart = HRTIMER_RESTART;
+		break;
+
+	default:
+		WARN_ON_ONCE(1);
+	}
+
+	return restart;
+}