net/can/isotp.c

// SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause)
/* isotp.c - ISO 15765-2 CAN transport protocol for protocol family CAN
 *
 * This implementation does not provide ISO-TP specific return values to the
 * userspace.
 *
 * - RX path timeout of data reception leads to -ETIMEDOUT
 * - RX path SN mismatch leads to -EILSEQ
 * - RX path data reception with wrong padding leads to -EBADMSG
 * - TX path flowcontrol reception timeout leads to -ECOMM
 * - TX path flowcontrol reception overflow leads to -EMSGSIZE
 * - TX path flowcontrol reception with wrong layout/padding leads to -EBADMSG
 * - when a transfer (tx) is on the run the next write() blocks until it's done
 * - use CAN_ISOTP_WAIT_TX_DONE flag to block the caller until the PDU is sent
 * - as we have static buffers the check whether the PDU fits into the buffer
 *   is done at FF reception time (no support for sending 'wait frames')
 *
 * Copyright (c) 2020 Volkswagen Group Electronic Research
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of Volkswagen nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * Alternatively, provided that this notice is retained in full, this
 * software may be distributed under the terms of the GNU General
 * Public License ("GPL") version 2, in which case the provisions of the
 * GPL apply INSTEAD OF those given above.
 *
 * The provided data structures and external interfaces from this code
 * are not restricted to be used by modules with a GPL compatible license.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/spinlock.h>
#include <linux/hrtimer.h>
#include <linux/wait.h>
#include <linux/uio.h>
#include <linux/net.h>
#include <linux/netdevice.h>
#include <linux/socket.h>
#include <linux/if_arp.h>
#include <linux/skbuff.h>
#include <linux/can.h>
#include <linux/can/core.h>
#include <linux/can/skb.h>
#include <linux/can/isotp.h>
#include <linux/slab.h>
#include <net/can.h>
#include <net/sock.h>
#include <net/net_namespace.h>

MODULE_DESCRIPTION("PF_CAN ISO 15765-2 transport protocol");
MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("Oliver Hartkopp <socketcan@hartkopp.net>");
MODULE_ALIAS("can-proto-6");

#define ISOTP_MIN_NAMELEN CAN_REQUIRED_SIZE(struct sockaddr_can, can_addr.tp)

#define SINGLE_MASK(id) (((id) & CAN_EFF_FLAG) ? \
			 (CAN_EFF_MASK | CAN_EFF_FLAG | CAN_RTR_FLAG) : \
			 (CAN_SFF_MASK | CAN_EFF_FLAG | CAN_RTR_FLAG))

/* Since ISO 15765-2:2016 the CAN isotp protocol supports more than 4095
 * byte per ISO PDU as the FF_DL can take full 32 bit values (4 Gbyte).
 * We would need some good concept to handle this between user space and
 * kernel space. For now set the static buffer to something about 8 kbyte
 * to be able to test this new functionality.
 */
#define DEFAULT_MAX_PDU_SIZE 8300

/* maximum PDU size before ISO 15765-2:2016 extension was 4095 */
#define MAX_12BIT_PDU_SIZE 4095

/* limit the isotp pdu size from the optional module parameter to 1MByte */
#define MAX_PDU_SIZE (1025 * 1024U)

static unsigned int max_pdu_size __read_mostly = DEFAULT_MAX_PDU_SIZE;
module_param(max_pdu_size, uint, 0444);
MODULE_PARM_DESC(max_pdu_size, "maximum isotp pdu size (default "
		 __stringify(DEFAULT_MAX_PDU_SIZE) ")");

/* N_PCI type values in bits 7-4 of N_PCI bytes */
#define N_PCI_SF 0x00	/* single frame */
#define N_PCI_FF 0x10	/* first frame */
#define N_PCI_CF 0x20	/* consecutive frame */
#define N_PCI_FC 0x30	/* flow control */

#define N_PCI_SZ 1	/* size of the PCI byte #1 */
#define SF_PCI_SZ4 1	/* size of SingleFrame PCI including 4 bit SF_DL */
#define SF_PCI_SZ8 2	/* size of SingleFrame PCI including 8 bit SF_DL */
#define FF_PCI_SZ12 2	/* size of FirstFrame PCI including 12 bit FF_DL */
#define FF_PCI_SZ32 6	/* size of FirstFrame PCI including 32 bit FF_DL */
#define FC_CONTENT_SZ 3	/* flow control content size in byte (FS/BS/STmin) */

#define ISOTP_CHECK_PADDING (CAN_ISOTP_CHK_PAD_LEN | CAN_ISOTP_CHK_PAD_DATA)
#define ISOTP_ALL_BC_FLAGS (CAN_ISOTP_SF_BROADCAST | CAN_ISOTP_CF_BROADCAST)

/* Flow Status given in FC frame */
#define ISOTP_FC_CTS 0		/* clear to send */
#define ISOTP_FC_WT 1		/* wait */
#define ISOTP_FC_OVFLW 2	/* overflow */

#define ISOTP_FC_TIMEOUT 1	/* 1 sec */
#define ISOTP_ECHO_TIMEOUT 2	/* 2 secs */

/* so->tx_result[so->tx_gen % ISOTP_TX_RESULT_SLOTS] holds the packed value
 * (err << ISOTP_TX_RESULT_GEN_BITS | gen) for each tx generation slot, so it
 * can be handled with a single READ_ONCE()/WRITE_ONCE() access.
 */
#define ISOTP_TX_RESULT_SLOTS 4
#define ISOTP_TX_RESULT_GEN_BITS 24
#define ISOTP_TX_RESULT_GEN_MASK ((1U << ISOTP_TX_RESULT_GEN_BITS) - 1)
#define ISOTP_TX_RESULT_ERR_MASK 0xFF

enum {
	ISOTP_IDLE = 0,
	ISOTP_WAIT_FIRST_FC,
	ISOTP_WAIT_FC,
	ISOTP_WAIT_DATA,
	ISOTP_SENDING,
	ISOTP_SHUTDOWN,
};

struct tpcon {
	u8 *buf;
	unsigned int buflen;
	unsigned int len;
	unsigned int idx;
	u32 state;
	u8 bs;
	u8 sn;
	u8 ll_dl;
	u8 sbuf[DEFAULT_MAX_PDU_SIZE];
};

struct isotp_sock {
	struct sock sk;
	int bound;
	int ifindex;
	struct net_device *dev;
	netdevice_tracker dev_tracker;
	canid_t txid;
	canid_t rxid;
	ktime_t tx_gap;
	ktime_t lastrxcf_tstamp;
	struct hrtimer rxtimer, txtimer, txfrtimer, echotimer;
	struct can_isotp_options opt;
	struct can_isotp_fc_options rxfc, txfc;
	struct can_isotp_ll_options ll;
	u32 frame_txtime;
	u32 force_tx_stmin;
	u32 force_rx_stmin;
	u32 cfecho; /* consecutive frame echo tag */
	u32 tx_gen; /* transfer generation, increased per new tx transfer */
	u32 tx_result[ISOTP_TX_RESULT_SLOTS]; /* per-generation result slots */
	struct tpcon rx, tx;
	struct list_head notifier;
	wait_queue_head_t wait;
	spinlock_t rx_lock; /* protect single thread state machine */
};

static LIST_HEAD(isotp_notifier_list);
static DEFINE_SPINLOCK(isotp_notifier_lock);
static struct isotp_sock *isotp_busy_notifier;

/* increase (24 bit) tx generation value */
static u32 isotp_inc_tx_gen(u32 gen)
{
	return (gen + 1) & ISOTP_TX_RESULT_GEN_MASK;
}

/* store 8 bit error and 24 bit tx generation values in packed u32 element */
static u32 isotp_pack_tx_result(u32 gen, int err)
{
	return gen | ((u32)err << ISOTP_TX_RESULT_GEN_BITS);
}

/* get the 24 bit tx generation value from the tx result */
static u32 isotp_get_tx_gen(u32 gen_err)
{
	return gen_err & ISOTP_TX_RESULT_GEN_MASK;
}

/* get the 8 bit error value from the tx result */
static u32 isotp_get_tx_err(u32 gen_err)
{
	return (gen_err >> ISOTP_TX_RESULT_GEN_BITS) & ISOTP_TX_RESULT_ERR_MASK;
}

/* store transfer result in per-generation%4 so->tx_result[] slot */
static void isotp_set_tx_result(struct isotp_sock *so, u32 gen, int err)
{
	WRITE_ONCE(so->tx_result[gen % ISOTP_TX_RESULT_SLOTS],
		   isotp_pack_tx_result(gen, err));
}

/* fetch the result recorded for 'gen', as a (negative) errno (0 for success) */
static int isotp_get_tx_result(struct isotp_sock *so, u32 gen)
{
	u32 result = READ_ONCE(so->tx_result[gen % ISOTP_TX_RESULT_SLOTS]);

	if (isotp_get_tx_gen(result) != gen) {
		pr_notice_once("can-isotp: tx_result[] slot reused before read\n");

		/* report failure rather than risk a false success */
		return -ECOMM;
	}

	return -(isotp_get_tx_err(result));
}

/* true if done, shut down or superseded ('gen' is no longer the active
 * transfer). Reads tx.state first (acquire) so tx_gen/tx_result reads
 * below see at least what that state write published (common sequence).
 */
static bool isotp_tx_gen_done(struct isotp_sock *so, u32 gen)
{
	/* read tx.state first for the common sequence */
	u32 state = smp_load_acquire(&so->tx.state);

	return state == ISOTP_IDLE || state == ISOTP_SHUTDOWN ||
	       READ_ONCE(so->tx_gen) != gen;
}

static inline struct isotp_sock *isotp_sk(const struct sock *sk)
{
	return (struct isotp_sock *)sk;
}

static u32 isotp_bc_flags(struct isotp_sock *so)
{
	return so->opt.flags & ISOTP_ALL_BC_FLAGS;
}

static bool isotp_register_rxid(struct isotp_sock *so)
{
	/* no broadcast modes => register rx_id for FC frame reception */
	return (isotp_bc_flags(so) == 0);
}

static enum hrtimer_restart isotp_rx_timer_handler(struct hrtimer *hrtimer)
{
	struct isotp_sock *so = container_of(hrtimer, struct isotp_sock,
					     rxtimer);
	struct sock *sk = &so->sk;

	if (READ_ONCE(so->rx.state) == ISOTP_WAIT_DATA) {
		/* we did not get new data frames in time */

		/* report 'connection timed out' */
		sk->sk_err = ETIMEDOUT;
		if (!sock_flag(sk, SOCK_DEAD))
			sk_error_report(sk);

		/* reset rx state */
		WRITE_ONCE(so->rx.state, ISOTP_IDLE);
	}

	return HRTIMER_NORESTART;
}

static int isotp_send_fc(struct sock *sk, int ae, u8 flowstatus)
{
	struct net_device *dev;
	struct sk_buff *nskb;
	struct can_skb_ext *csx;
	struct canfd_frame *ncf;
	struct isotp_sock *so = isotp_sk(sk);
	int can_send_ret;

	nskb = alloc_skb(so->ll.mtu, gfp_any());
	if (!nskb)
		return 1;

	csx = can_skb_ext_add(nskb);
	if (!csx) {
		kfree_skb(nskb);
		return 1;
	}

	dev = dev_get_by_index(sock_net(sk), so->ifindex);
	if (!dev) {
		kfree_skb(nskb);
		return 1;
	}

	csx->can_iif = dev->ifindex;
	nskb->dev = dev;
	can_skb_set_owner(nskb, sk);
	ncf = (struct canfd_frame *)nskb->data;
	skb_put_zero(nskb, so->ll.mtu);

	/* create & send flow control reply */
	ncf->can_id = so->txid;

	if (so->opt.flags & CAN_ISOTP_TX_PADDING) {
		memset(ncf->data, so->opt.txpad_content, CAN_MAX_DLEN);
		ncf->len = CAN_MAX_DLEN;
	} else {
		ncf->len = ae + FC_CONTENT_SZ;
	}

	ncf->data[ae] = N_PCI_FC | flowstatus;
	ncf->data[ae + 1] = so->rxfc.bs;
	ncf->data[ae + 2] = so->rxfc.stmin;

	if (ae)
		ncf->data[0] = so->opt.ext_address;

	ncf->flags = so->ll.tx_flags;

	can_send_ret = can_send(nskb, 1);
	if (can_send_ret)
		pr_notice_once("can-isotp: %s: can_send_ret %pe\n",
			       __func__, ERR_PTR(can_send_ret));

	dev_put(dev);

	/* reset blocksize counter */
	so->rx.bs = 0;

	/* reset last CF frame rx timestamp for rx stmin enforcement */
	so->lastrxcf_tstamp = ktime_set(0, 0);

	/* start rx timeout watchdog */
	hrtimer_start(&so->rxtimer, ktime_set(ISOTP_FC_TIMEOUT, 0),
		      HRTIMER_MODE_REL_SOFT);
	return 0;
}

static void isotp_rcv_skb(struct sk_buff *skb, struct sock *sk)
{
	struct sockaddr_can *addr = (struct sockaddr_can *)skb->cb;
	enum skb_drop_reason reason;

	BUILD_BUG_ON(sizeof(skb->cb) < sizeof(struct sockaddr_can));

	memset(addr, 0, sizeof(*addr));
	addr->can_family = AF_CAN;
	addr->can_ifindex = skb->dev->ifindex;

	reason = sock_queue_rcv_skb_reason(sk, skb);
	if (reason)
		sk_skb_reason_drop(sk, skb, reason);
}

static u8 padlen(u8 datalen)
{
	static const u8 plen[] = {
		8, 8, 8, 8, 8, 8, 8, 8, 8,	/* 0 - 8 */
		12, 12, 12, 12,			/* 9 - 12 */
		16, 16, 16, 16,			/* 13 - 16 */
		20, 20, 20, 20,			/* 17 - 20 */
		24, 24, 24, 24,			/* 21 - 24 */
		32, 32, 32, 32, 32, 32, 32, 32,	/* 25 - 32 */
		48, 48, 48, 48, 48, 48, 48, 48,	/* 33 - 40 */
		48, 48, 48, 48, 48, 48, 48, 48	/* 41 - 48 */
	};

	if (datalen > 48)
		return 64;

	return plen[datalen];
}

/* check for length optimization and return 1/true when the check fails */
static int check_optimized(struct canfd_frame *cf, int start_index)
{
	/* for CAN_DL <= 8 the start_index is equal to the CAN_DL as the
	 * padding would start at this point. E.g. if the padding would
	 * start at cf.data[7] cf->len has to be 7 to be optimal.
	 * Note: The data[] index starts with zero.
	 */
	if (cf->len <= CAN_MAX_DLEN)
		return (cf->len != start_index);

	/* This relation is also valid in the non-linear DLC range, where
	 * we need to take care of the minimal next possible CAN_DL.
	 * The correct check would be (padlen(cf->len) != padlen(start_index)).
	 * But as cf->len can only take discrete values from 12, .., 64 at this
	 * point the padlen(cf->len) is always equal to cf->len.
	 */
	return (cf->len != padlen(start_index));
}

/* check padding and return 1/true when the check fails */
static int check_pad(struct isotp_sock *so, struct canfd_frame *cf,
		     int start_index, u8 content)
{
	int i;

	/* no RX_PADDING value => check length of optimized frame length */
	if (!(so->opt.flags & CAN_ISOTP_RX_PADDING)) {
		if (so->opt.flags & CAN_ISOTP_CHK_PAD_LEN)
			return check_optimized(cf, start_index);

		/* no valid test against empty value => ignore frame */
		return 1;
	}

	/* check datalength of correctly padded CAN frame */
	if ((so->opt.flags & CAN_ISOTP_CHK_PAD_LEN) &&
	    cf->len != padlen(cf->len))
		return 1;

	/* check padding content */
	if (so->opt.flags & CAN_ISOTP_CHK_PAD_DATA) {
		for (i = start_index; i < cf->len; i++)
			if (cf->data[i] != content)
				return 1;
	}
	return 0;
}

static void isotp_send_cframe(struct isotp_sock *so);

static int isotp_rcv_fc(struct isotp_sock *so, struct canfd_frame *cf, int ae)
{
	struct sock *sk = &so->sk;
	int tx_err = EBADMSG; /* default for unknown FC status */

	if (READ_ONCE(so->tx.state) != ISOTP_WAIT_FC &&
	    READ_ONCE(so->tx.state) != ISOTP_WAIT_FIRST_FC)
		return 0;

	hrtimer_cancel(&so->txtimer);

	/* isotp_tx_timeout() may have given up on this job while
	 * hrtimer_cancel() above waited for it to finish => recheck
	 */
	if (READ_ONCE(so->tx.state) != ISOTP_WAIT_FC &&
	    READ_ONCE(so->tx.state) != ISOTP_WAIT_FIRST_FC)
		return 1;

	if ((cf->len < ae + FC_CONTENT_SZ) ||
	    ((so->opt.flags & ISOTP_CHECK_PADDING) &&
	     check_pad(so, cf, ae + FC_CONTENT_SZ, so->opt.rxpad_content))) {
		/* malformed PDU - report 'not a data message' */
		sk->sk_err = EBADMSG;
		if (!sock_flag(sk, SOCK_DEAD))
			sk_error_report(sk);

		isotp_set_tx_result(so, so->tx_gen, EBADMSG);
		/* set to IDLE after publishing tx_result */
		smp_store_release(&so->tx.state, ISOTP_IDLE);
		wake_up_interruptible(&so->wait);
		return 1;
	}

	/* get static/dynamic communication params from first/every FC frame */
	if (READ_ONCE(so->tx.state) == ISOTP_WAIT_FIRST_FC ||
	    so->opt.flags & CAN_ISOTP_DYN_FC_PARMS) {
		so->txfc.bs = cf->data[ae + 1];
		so->txfc.stmin = cf->data[ae + 2];

		/* fix wrong STmin values according spec */
		if (so->txfc.stmin > 0x7F &&
		    (so->txfc.stmin < 0xF1 || so->txfc.stmin > 0xF9))
			so->txfc.stmin = 0x7F;

		so->tx_gap = ktime_set(0, 0);
		/* add transmission time for CAN frame N_As */
		so->tx_gap = ktime_add_ns(so->tx_gap, so->frame_txtime);
		/* add waiting time for consecutive frames N_Cs */
		if (so->opt.flags & CAN_ISOTP_FORCE_TXSTMIN)
			so->tx_gap = ktime_add_ns(so->tx_gap,
						  so->force_tx_stmin);
		else if (so->txfc.stmin < 0x80)
			so->tx_gap = ktime_add_ns(so->tx_gap,
						  so->txfc.stmin * 1000000);
		else
			so->tx_gap = ktime_add_ns(so->tx_gap,
						  (so->txfc.stmin - 0xF0)
						  * 100000);
		WRITE_ONCE(so->tx.state, ISOTP_WAIT_FC);
	}

	switch (cf->data[ae] & 0x0F) {
	case ISOTP_FC_CTS:
		so->tx.bs = 0;
		WRITE_ONCE(so->tx.state, ISOTP_SENDING);
		/* send CF frame and enable echo timeout handling */
		hrtimer_start(&so->echotimer, ktime_set(ISOTP_ECHO_TIMEOUT, 0),
			      HRTIMER_MODE_REL_SOFT);
		isotp_send_cframe(so);
		break;

	case ISOTP_FC_WT:
		/* start timer to wait for next FC frame */
		hrtimer_start(&so->txtimer, ktime_set(ISOTP_FC_TIMEOUT, 0),
			      HRTIMER_MODE_REL_SOFT);
		break;

	case ISOTP_FC_OVFLW:
		/* overflow on receiver side - report 'message too long' */
		tx_err = EMSGSIZE;
		fallthrough;

	default:
		/* reserved/unknown flow status (tx_err defaults to EBADMSG) */

		sk->sk_err = tx_err;
		if (!sock_flag(sk, SOCK_DEAD))
			sk_error_report(sk);

		isotp_set_tx_result(so, so->tx_gen, tx_err);
		/* set to IDLE after publishing tx_result */
		smp_store_release(&so->tx.state, ISOTP_IDLE);
		wake_up_interruptible(&so->wait);
	}
	return 0;
}

static int isotp_rcv_sf(struct sock *sk, struct canfd_frame *cf, int pcilen,
			struct sk_buff *skb, int len)
{
	struct isotp_sock *so = isotp_sk(sk);
	struct sk_buff *nskb;

	hrtimer_cancel(&so->rxtimer);
	WRITE_ONCE(so->rx.state, ISOTP_IDLE);

	if (!len || len > cf->len - pcilen)
		return 1;

	if ((so->opt.flags & ISOTP_CHECK_PADDING) &&
	    check_pad(so, cf, pcilen + len, so->opt.rxpad_content)) {
		/* malformed PDU - report 'not a data message' */
		sk->sk_err = EBADMSG;
		if (!sock_flag(sk, SOCK_DEAD))
			sk_error_report(sk);
		return 1;
	}

	nskb = alloc_skb(len, gfp_any());
	if (!nskb)
		return 1;

	memcpy(skb_put(nskb, len), &cf->data[pcilen], len);

	nskb->tstamp = skb->tstamp;
	nskb->dev = skb->dev;
	isotp_rcv_skb(nskb, sk);
	return 0;
}

static int isotp_rcv_ff(struct sock *sk, struct canfd_frame *cf, int ae)
{
	struct isotp_sock *so = isotp_sk(sk);
	int i;
	int off;
	int ff_pci_sz;

	hrtimer_cancel(&so->rxtimer);
	WRITE_ONCE(so->rx.state, ISOTP_IDLE);

	/* get the used sender LL_DL from the (first) CAN frame data length */
	so->rx.ll_dl = padlen(cf->len);

	/* the first frame has to use the entire frame up to LL_DL length */
	if (cf->len != so->rx.ll_dl)
		return 1;

	/* get the FF_DL */
	so->rx.len = (cf->data[ae] & 0x0F) << 8;
	so->rx.len += cf->data[ae + 1];

	/* Check for FF_DL escape sequence supporting 32 bit PDU length */
	if (so->rx.len) {
		ff_pci_sz = FF_PCI_SZ12;
	} else {
		/* FF_DL = 0 => get real length from next 4 bytes */
		so->rx.len = cf->data[ae + 2] << 24;
		so->rx.len += cf->data[ae + 3] << 16;
		so->rx.len += cf->data[ae + 4] << 8;
		so->rx.len += cf->data[ae + 5];
		ff_pci_sz = FF_PCI_SZ32;
	}

	/* take care of a potential SF_DL ESC offset for TX_DL > 8 */
	off = (so->rx.ll_dl > CAN_MAX_DLEN) ? 1 : 0;

	if (so->rx.len + ae + off + ff_pci_sz < so->rx.ll_dl)
		return 1;

	/* PDU size > default => try max_pdu_size */
	if (so->rx.len > so->rx.buflen && so->rx.buflen < max_pdu_size) {
		u8 *newbuf = kmalloc(max_pdu_size, GFP_ATOMIC);

		if (newbuf) {
			so->rx.buf = newbuf;
			so->rx.buflen = max_pdu_size;
		}
	}

	if (so->rx.len > so->rx.buflen) {
		/* send FC frame with overflow status */
		isotp_send_fc(sk, ae, ISOTP_FC_OVFLW);
		return 1;
	}

	/* copy the first received data bytes */
	so->rx.idx = 0;
	for (i = ae + ff_pci_sz; i < so->rx.ll_dl; i++)
		so->rx.buf[so->rx.idx++] = cf->data[i];

	/* initial setup for this pdu reception */
	so->rx.sn = 1;
	WRITE_ONCE(so->rx.state, ISOTP_WAIT_DATA);

	/* no creation of flow control frames */
	if (so->opt.flags & CAN_ISOTP_LISTEN_MODE)
		return 0;

	/* send our first FC frame */
	isotp_send_fc(sk, ae, ISOTP_FC_CTS);
	return 0;
}

static int isotp_rcv_cf(struct sock *sk, struct canfd_frame *cf, int ae,
			struct sk_buff *skb)
{
	struct isotp_sock *so = isotp_sk(sk);
	struct sk_buff *nskb;
	int i;

	if (READ_ONCE(so->rx.state) != ISOTP_WAIT_DATA)
		return 0;

	/* drop if timestamp gap is less than force_rx_stmin nano secs */
	if (so->opt.flags & CAN_ISOTP_FORCE_RXSTMIN) {
		if (ktime_to_ns(ktime_sub(skb->tstamp, so->lastrxcf_tstamp)) <
		    so->force_rx_stmin)
			return 0;

		so->lastrxcf_tstamp = skb->tstamp;
	}

	hrtimer_cancel(&so->rxtimer);

	/* isotp_rx_timer_handler() may have raced us for so->rx.state
	 * while hrtimer_cancel() above waited for it to finish => recheck
	 */
	if (READ_ONCE(so->rx.state) != ISOTP_WAIT_DATA)
		return 1;

	/* CFs are never longer than the FF */
	if (cf->len > so->rx.ll_dl)
		return 1;

	/* CFs have usually the LL_DL length */
	if (cf->len < so->rx.ll_dl) {
		/* this is only allowed for the last CF */
		if (so->rx.len - so->rx.idx > so->rx.ll_dl - ae - N_PCI_SZ)
			return 1;
	}

	if ((cf->data[ae] & 0x0F) != so->rx.sn) {
		/* wrong sn detected - report 'illegal byte sequence' */
		sk->sk_err = EILSEQ;
		if (!sock_flag(sk, SOCK_DEAD))
			sk_error_report(sk);

		/* reset rx state */
		WRITE_ONCE(so->rx.state, ISOTP_IDLE);
		return 1;
	}
	so->rx.sn++;
	so->rx.sn %= 16;

	for (i = ae + N_PCI_SZ; i < cf->len; i++) {
		so->rx.buf[so->rx.idx++] = cf->data[i];
		if (so->rx.idx >= so->rx.len)
			break;
	}

	if (so->rx.idx >= so->rx.len) {
		/* we are done */
		WRITE_ONCE(so->rx.state, ISOTP_IDLE);

		if ((so->opt.flags & ISOTP_CHECK_PADDING) &&
		    check_pad(so, cf, i + 1, so->opt.rxpad_content)) {
			/* malformed PDU - report 'not a data message' */
			sk->sk_err = EBADMSG;
			if (!sock_flag(sk, SOCK_DEAD))
				sk_error_report(sk);
			return 1;
		}

		nskb = alloc_skb(so->rx.len, gfp_any());
		if (!nskb)
			return 1;

		memcpy(skb_put(nskb, so->rx.len), so->rx.buf,
		       so->rx.len);

		nskb->tstamp = skb->tstamp;
		nskb->dev = skb->dev;
		isotp_rcv_skb(nskb, sk);
		return 0;
	}

	/* perform blocksize handling, if enabled */
	if (!so->rxfc.bs || ++so->rx.bs < so->rxfc.bs) {
		/* start rx timeout watchdog */
		hrtimer_start(&so->rxtimer, ktime_set(ISOTP_FC_TIMEOUT, 0),
			      HRTIMER_MODE_REL_SOFT);
		return 0;
	}

	/* no creation of flow control frames */
	if (so->opt.flags & CAN_ISOTP_LISTEN_MODE)
		return 0;

	/* we reached the specified blocksize so->rxfc.bs */
	isotp_send_fc(sk, ae, ISOTP_FC_CTS);
	return 0;
}

static void isotp_rcv(struct sk_buff *skb, void *data)
{
	struct sock *sk = (struct sock *)data;
	struct isotp_sock *so = isotp_sk(sk);
	struct canfd_frame *cf;
	int ae = (so->opt.flags & CAN_ISOTP_EXTEND_ADDR) ? 1 : 0;
	u8 n_pci_type, sf_dl;

	/* Strictly receive only frames with the configured MTU size
	 * => clear separation of CAN2.0 / CAN FD transport channels
	 */
	if (skb->len != so->ll.mtu)
		return;

	cf = (struct canfd_frame *)skb->data;

	/* if enabled: check reception of my configured extended address */
	if (ae && cf->data[0] != so->opt.rx_ext_address)
		return;

	n_pci_type = cf->data[ae] & 0xF0;

	/* Make sure the state changes and data structures stay consistent at
	 * CAN frame reception time. This locking is not needed in real world
	 * use cases but the inconsistency can be triggered with syzkaller.
	 */
	spin_lock(&so->rx_lock);

	if (so->opt.flags & CAN_ISOTP_HALF_DUPLEX) {
		/* check rx/tx path half duplex expectations */
		if ((READ_ONCE(so->tx.state) != ISOTP_IDLE &&
		     n_pci_type != N_PCI_FC) ||
		    (READ_ONCE(so->rx.state) != ISOTP_IDLE &&
		     n_pci_type == N_PCI_FC))
			goto out_unlock;
	}

	switch (n_pci_type) {
	case N_PCI_FC:
		/* tx path: flow control frame containing the FC parameters */
		isotp_rcv_fc(so, cf, ae);
		break;

	case N_PCI_SF:
		/* rx path: single frame
		 *
		 * As we do not have a rx.ll_dl configuration, we can only test
		 * if the CAN frames payload length matches the LL_DL == 8
		 * requirements - no matter if it's CAN 2.0 or CAN FD
		 */

		/* get the SF_DL from the N_PCI byte */
		sf_dl = cf->data[ae] & 0x0F;

		if (cf->len <= CAN_MAX_DLEN) {
			isotp_rcv_sf(sk, cf, SF_PCI_SZ4 + ae, skb, sf_dl);
		} else {
			if (can_is_canfd_skb(skb)) {
				/* We have a CAN FD frame and CAN_DL is greater than 8:
				 * Only frames with the SF_DL == 0 ESC value are valid.
				 *
				 * If so take care of the increased SF PCI size
				 * (SF_PCI_SZ8) to point to the message content behind
				 * the extended SF PCI info and get the real SF_DL
				 * length value from the formerly first data byte.
				 */
				if (sf_dl == 0)
					isotp_rcv_sf(sk, cf, SF_PCI_SZ8 + ae, skb,
						     cf->data[SF_PCI_SZ4 + ae]);
			}
		}
		break;

	case N_PCI_FF:
		/* rx path: first frame */
		isotp_rcv_ff(sk, cf, ae);
		break;

	case N_PCI_CF:
		/* rx path: consecutive frame */
		isotp_rcv_cf(sk, cf, ae, skb);
		break;
	}

out_unlock:
	spin_unlock(&so->rx_lock);
}

static void isotp_fill_dataframe(struct canfd_frame *cf, struct isotp_sock *so,
				 int ae, int off)
{
	int pcilen = N_PCI_SZ + ae + off;
	int space = so->tx.ll_dl - pcilen;
	int num = min_t(int, so->tx.len - so->tx.idx, space);
	int i;

	cf->can_id = so->txid;
	cf->len = num + pcilen;

	if (num < space) {
		if (so->opt.flags & CAN_ISOTP_TX_PADDING) {
			/* user requested padding */
			cf->len = padlen(cf->len);
			memset(cf->data, so->opt.txpad_content, cf->len);
		} else if (cf->len > CAN_MAX_DLEN) {
			/* mandatory padding for CAN FD frames */
			cf->len = padlen(cf->len);
			memset(cf->data, CAN_ISOTP_DEFAULT_PAD_CONTENT,
			       cf->len);
		}
	}

	for (i = 0; i < num; i++)
		cf->data[pcilen + i] = so->tx.buf[so->tx.idx++];

	if (ae)
		cf->data[0] = so->opt.ext_address;
}

static void isotp_send_cframe(struct isotp_sock *so)
{
	struct sock *sk = &so->sk;
	struct sk_buff *skb;
	struct can_skb_ext *csx;
	struct net_device *dev;
	struct canfd_frame *cf;
	int can_send_ret;
	int ae = (so->opt.flags & CAN_ISOTP_EXTEND_ADDR) ? 1 : 0;
	u32 old_cfecho;

	dev = dev_get_by_index(sock_net(sk), so->ifindex);
	if (!dev)
		return;

	skb = alloc_skb(so->ll.mtu, GFP_ATOMIC);
	if (!skb) {
		dev_put(dev);
		return;
	}

	csx = can_skb_ext_add(skb);
	if (!csx) {
		kfree_skb(skb);
		netdev_put(dev, NULL);
		return;
	}

	csx->can_iif = dev->ifindex;

	/* set uid in tx skb to identify CF echo frames */
	can_set_skb_uid(csx);

	cf = (struct canfd_frame *)skb->data;
	skb_put_zero(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++;

	cf->flags = so->ll.tx_flags;

	skb->dev = dev;
	can_skb_set_owner(skb, sk);

	/* zero'ed by init/isotp_rcv_echo(); reached lock-free via
	 * isotp_txfr_timer_handler() too, so use READ_ONCE()/WRITE_ONCE()
	 */
	old_cfecho = READ_ONCE(so->cfecho);
	if (old_cfecho)
		pr_notice_once("can-isotp: cfecho is %08X != 0\n", old_cfecho);

	/* set consecutive frame echo tag */
	WRITE_ONCE(so->cfecho, csx->can_skb_uid);

	/* send frame with local echo enabled */
	can_send_ret = can_send(skb, 1);
	if (can_send_ret) {
		pr_notice_once("can-isotp: %s: can_send_ret %pe\n",
			       __func__, ERR_PTR(can_send_ret));
		if (can_send_ret == -ENOBUFS)
			pr_notice_once("can-isotp: tx queue is full\n");
	}
	dev_put(dev);
}

static void isotp_create_fframe(struct canfd_frame *cf, struct isotp_sock *so,
				int ae)
{
	int i;
	int ff_pci_sz;

	cf->can_id = so->txid;
	cf->len = so->tx.ll_dl;
	if (ae)
		cf->data[0] = so->opt.ext_address;

	/* create N_PCI bytes with 12/32 bit FF_DL data length */
	if (so->tx.len > MAX_12BIT_PDU_SIZE) {
		/* use 32 bit FF_DL notation */
		cf->data[ae] = N_PCI_FF;
		cf->data[ae + 1] = 0;
		cf->data[ae + 2] = (u8)(so->tx.len >> 24) & 0xFFU;
		cf->data[ae + 3] = (u8)(so->tx.len >> 16) & 0xFFU;
		cf->data[ae + 4] = (u8)(so->tx.len >> 8) & 0xFFU;
		cf->data[ae + 5] = (u8)so->tx.len & 0xFFU;
		ff_pci_sz = FF_PCI_SZ32;
	} else {
		/* use 12 bit FF_DL notation */
		cf->data[ae] = (u8)(so->tx.len >> 8) | N_PCI_FF;
		cf->data[ae + 1] = (u8)so->tx.len & 0xFFU;
		ff_pci_sz = FF_PCI_SZ12;
	}

	/* add first data bytes depending on ae */
	for (i = ae + ff_pci_sz; i < so->tx.ll_dl; i++)
		cf->data[i] = so->tx.buf[so->tx.idx++];

	so->tx.sn = 1;
}

static void isotp_rcv_echo(struct sk_buff *skb, void *data)
{
	struct sock *sk = (struct sock *)data;
	struct isotp_sock *so = isotp_sk(sk);
	struct can_skb_ext *csx = can_skb_ext_find(skb);

	/* only handle my own local echo CF/SF skb's (no FF!) */
	if (skb->sk != sk)
		return;

	if (WARN_ON_ONCE(!csx))
		return;

	/* unlike isotp_rcv_fc()/isotp_rcv_cf(), not already under so->rx_lock
	 * (no isotp_rcv() caller here), so take it ourselves
	 */
	spin_lock(&so->rx_lock);

	/* so->cfecho may since belong to a new transfer; recheck under lock */
	if (READ_ONCE(so->cfecho) != csx->can_skb_uid)
		goto out_unlock;

	/* cancel local echo timeout */
	hrtimer_cancel(&so->echotimer);

	/* local echo skb with consecutive frame has been consumed */
	WRITE_ONCE(so->cfecho, 0);

	/* claiming a transfer also takes so->rx_lock, so a plain recheck
	 * is enough: so->tx.state can't have flipped to ISOTP_SENDING for
	 * a new claim while we're still in here
	 */
	if (READ_ONCE(so->tx.state) != ISOTP_SENDING)
		goto out_unlock;

	if (so->tx.idx >= so->tx.len) {
		/* we are done */

		isotp_set_tx_result(so, so->tx_gen, 0);
		/* set to IDLE after publishing tx_result */
		smp_store_release(&so->tx.state, ISOTP_IDLE);
		wake_up_interruptible(&so->wait);
		goto out_unlock;
	}

	if (so->txfc.bs && so->tx.bs >= so->txfc.bs) {
		/* stop and wait for FC with timeout */
		WRITE_ONCE(so->tx.state, ISOTP_WAIT_FC);
		hrtimer_start(&so->txtimer, ktime_set(ISOTP_FC_TIMEOUT, 0),
			      HRTIMER_MODE_REL_SOFT);
		goto out_unlock;
	}

	/* no gap between data frames needed => use burst mode */
	if (!so->tx_gap) {
		/* enable echo timeout handling */
		hrtimer_start(&so->echotimer, ktime_set(ISOTP_ECHO_TIMEOUT, 0),
			      HRTIMER_MODE_REL_SOFT);
		isotp_send_cframe(so);
		goto out_unlock;
	}

	/* start timer to send next consecutive frame with correct delay */
	hrtimer_start(&so->txfrtimer, so->tx_gap, HRTIMER_MODE_REL_SOFT);

out_unlock:
	spin_unlock(&so->rx_lock);
}

/* isotp_tx_timeout: we did not get any flow control or echo frame in time
 *
 * Shared by so->txtimer's and so->echotimer's callbacks. Both timers get
 * cancelled under so->rx_lock elsewhere, so this must stay lock-free.
 *
 * tx.state is acquired before tx_gen. Common sequence in isotp_tx_gen_done().
 * cmpxchg() only orders itself, not the two preceding loads.
 */
static enum hrtimer_restart isotp_tx_timeout(struct isotp_sock *so)
{
	struct sock *sk = &so->sk;
	/* read tx.state first for the common sequence */
	u32 old_state = smp_load_acquire(&so->tx.state);
	u32 gen = READ_ONCE(so->tx_gen);

	/* don't handle timeouts in IDLE or SHUTDOWN state */
	if (old_state == ISOTP_IDLE || old_state == ISOTP_SHUTDOWN)
		return HRTIMER_NORESTART;

	/* only claim the timeout if the state is still unchanged */
	if (cmpxchg(&so->tx.state, old_state, ISOTP_IDLE) != old_state)
		return HRTIMER_NORESTART;

	/* detected timeout: report 'communication error on send' */

	/* a stale read of this slot by a waiter still falls back to ECOMM */
	isotp_set_tx_result(so, gen, ECOMM);

	sk->sk_err = ECOMM;
	if (!sock_flag(sk, SOCK_DEAD))
		sk_error_report(sk);

	wake_up_interruptible(&so->wait);

	return HRTIMER_NORESTART;
}

/* so->txtimer: fires when a Flow Control frame does not arrive in time */
static enum hrtimer_restart isotp_tx_timer_handler(struct hrtimer *hrtimer)
{
	struct isotp_sock *so = container_of(hrtimer, struct isotp_sock,
					     txtimer);

	return isotp_tx_timeout(so);
}

/* so->echotimer: fires when a sent CF/SF's local echo does not arrive */
static enum hrtimer_restart isotp_echo_timer_handler(struct hrtimer *hrtimer)
{
	struct isotp_sock *so = container_of(hrtimer, struct isotp_sock,
					     echotimer);

	return isotp_tx_timeout(so);
}

static enum hrtimer_restart isotp_txfr_timer_handler(struct hrtimer *hrtimer)
{
	struct isotp_sock *so = container_of(hrtimer, struct isotp_sock,
					     txfrtimer);

	/* start echo timeout handling and cover below protocol error */
	hrtimer_start(&so->echotimer, ktime_set(ISOTP_ECHO_TIMEOUT, 0),
		      HRTIMER_MODE_REL_SOFT);

	/* cfecho should be consumed by isotp_rcv_echo() here */
	if (READ_ONCE(so->tx.state) == ISOTP_SENDING && !READ_ONCE(so->cfecho))
		isotp_send_cframe(so);

	return HRTIMER_NORESTART;
}

static int isotp_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
{
	struct sock *sk = sock->sk;
	struct isotp_sock *so = isotp_sk(sk);
	struct sk_buff *skb;
	struct can_skb_ext *csx;
	struct net_device *dev;
	struct canfd_frame *cf;
	int ae = (so->opt.flags & CAN_ISOTP_EXTEND_ADDR) ? 1 : 0;
	int wait_tx_done = (so->opt.flags & CAN_ISOTP_WAIT_TX_DONE) ? 1 : 0;
	s64 hrtimer_sec = ISOTP_ECHO_TIMEOUT;
	struct hrtimer *tx_hrt = &so->echotimer;
	u32 new_state = ISOTP_SENDING;
	u32 my_gen;
	u32 old_cfecho;
	int off;
	int err;

	if (!so->bound || READ_ONCE(so->tx.state) == ISOTP_SHUTDOWN)
		return -EADDRNOTAVAIL;

	/* claim the socket under so->rx_lock: this serializes the claim
	 * with the RX path and with sendmsg()'s own error paths below, so
	 * none of them can ever see a transfer mid-claim
	 */
	for (;;) {
		spin_lock_bh(&so->rx_lock);
		if (READ_ONCE(so->tx.state) == ISOTP_IDLE)
			break;
		spin_unlock_bh(&so->rx_lock);

		/* we do not support multiple buffers - for now */
		if (msg->msg_flags & MSG_DONTWAIT)
			return -EAGAIN;

		if (READ_ONCE(so->tx.state) == ISOTP_SHUTDOWN)
			return -EADDRNOTAVAIL;

		/* wait for complete transmission of current pdu */
		err = wait_event_interruptible(so->wait,
					       READ_ONCE(so->tx.state) == ISOTP_IDLE ||
					       READ_ONCE(so->tx.state) == ISOTP_SHUTDOWN);
		if (err)
			return err;
	}

	/* txfrtimer's callback re-arms echotimer lock-free: drain it first */
	hrtimer_cancel(&so->txfrtimer);
	hrtimer_cancel(&so->txtimer);
	hrtimer_cancel(&so->echotimer);

	/* new transfer: increment so->tx_gen and set tx.state after barrier */
	my_gen = isotp_inc_tx_gen(READ_ONCE(so->tx_gen));
	isotp_set_tx_result(so, my_gen, ECOMM); /* prevent stale slot matching */
	WRITE_ONCE(so->tx_gen, my_gen);
	smp_wmb(); /* see smp_load_acquire() in isotp_tx_[timeout|gen_done] */
	WRITE_ONCE(so->tx.state, ISOTP_SENDING);
	WRITE_ONCE(so->cfecho, 0);
	spin_unlock_bh(&so->rx_lock);

	/* so->bound is only checked once above - a wakeup may have
	 * unbound/rebound the socket meanwhile => recheck
	 */
	if (!so->bound) {
		err = -EADDRNOTAVAIL;
		goto err_out_drop;
	}

	/* PDU size > default => try max_pdu_size */
	if (size > so->tx.buflen && so->tx.buflen < max_pdu_size) {
		u8 *newbuf = kmalloc(max_pdu_size, GFP_KERNEL);

		if (newbuf) {
			so->tx.buf = newbuf;
			so->tx.buflen = max_pdu_size;
		}
	}

	if (!size || size > so->tx.buflen) {
		err = -EINVAL;
		goto err_out_drop;
	}

	/* take care of a potential SF_DL ESC offset for TX_DL > 8 */
	off = (so->tx.ll_dl > CAN_MAX_DLEN) ? 1 : 0;

	/* does the given data fit into a single frame for SF_BROADCAST? */
	if ((isotp_bc_flags(so) == CAN_ISOTP_SF_BROADCAST) &&
	    (size > so->tx.ll_dl - SF_PCI_SZ4 - ae - off)) {
		err = -EINVAL;
		goto err_out_drop;
	}

	err = memcpy_from_msg(so->tx.buf, msg, size);
	if (err < 0)
		goto err_out_drop;

	dev = dev_get_by_index(sock_net(sk), so->ifindex);
	if (!dev) {
		err = -ENXIO;
		goto err_out_drop;
	}

	skb = sock_alloc_send_skb(sk, so->ll.mtu, msg->msg_flags & MSG_DONTWAIT,
				  &err);
	if (!skb) {
		dev_put(dev);
		goto err_out_drop;
	}

	csx = can_skb_ext_add(skb);
	if (!csx) {
		kfree_skb(skb);
		netdev_put(dev, NULL);
		err = -ENOMEM;
		goto err_out_drop;
	}

	csx->can_iif = dev->ifindex;

	/* set uid in tx skb to identify CF echo frames */
	can_set_skb_uid(csx);

	so->tx.len = size;
	so->tx.idx = 0;

	cf = (struct canfd_frame *)skb->data;
	skb_put_zero(skb, so->ll.mtu);

	/* cfecho should have been zero'ed by init / former isotp_rcv_echo() */
	old_cfecho = READ_ONCE(so->cfecho);
	if (old_cfecho)
		pr_notice_once("can-isotp: uninit cfecho %08X\n", old_cfecho);

	/* check for single frame transmission depending on TX_DL */
	if (size <= so->tx.ll_dl - SF_PCI_SZ4 - ae - off) {
		/* The message size generally fits into a SingleFrame - good.
		 *
		 * SF_DL ESC offset optimization:
		 *
		 * When TX_DL is greater 8 but the message would still fit
		 * into a 8 byte CAN frame, we can omit the offset.
		 * This prevents a protocol caused length extension from
		 * CAN_DL = 8 to CAN_DL = 12 due to the SF_SL ESC handling.
		 */
		if (size <= CAN_MAX_DLEN - SF_PCI_SZ4 - ae)
			off = 0;

		isotp_fill_dataframe(cf, so, ae, off);

		/* place single frame N_PCI w/o length in appropriate index */
		cf->data[ae] = N_PCI_SF;

		/* place SF_DL size value depending on the SF_DL ESC offset */
		if (off)
			cf->data[SF_PCI_SZ4 + ae] = size;
		else
			cf->data[ae] |= size;

		/* set CF echo tag for isotp_rcv_echo() (SF-mode) */
		WRITE_ONCE(so->cfecho, csx->can_skb_uid);
	} else {
		/* send first frame */

		isotp_create_fframe(cf, so, ae);

		if (isotp_bc_flags(so) == CAN_ISOTP_CF_BROADCAST) {
			/* set timer for FC-less operation (STmin = 0) */
			if (so->opt.flags & CAN_ISOTP_FORCE_TXSTMIN)
				so->tx_gap = ktime_set(0, so->force_tx_stmin);
			else
				so->tx_gap = ktime_set(0, so->frame_txtime);

			/* disable wait for FCs due to activated block size */
			so->txfc.bs = 0;

			/* set CF echo tag for isotp_rcv_echo() (CF-mode) */
			WRITE_ONCE(so->cfecho, csx->can_skb_uid);
		} else {
			/* standard flow control check */
			new_state = ISOTP_WAIT_FIRST_FC;

			/* start timeout for FC */
			hrtimer_sec = ISOTP_FC_TIMEOUT;
			tx_hrt = &so->txtimer;

			/* no CF echo tag for isotp_rcv_echo() (FF-mode) */
			WRITE_ONCE(so->cfecho, 0);
		}
	}

	spin_lock_bh(&so->rx_lock);
	if (READ_ONCE(so->tx.state) == ISOTP_SHUTDOWN) {
		/* isotp_release() has since taken over and already drained
		 * our timers - don't send into a socket that's going away
		 */
		spin_unlock_bh(&so->rx_lock);
		kfree_skb(skb);
		dev_put(dev);
		wake_up_interruptible(&so->wait);
		return -EADDRNOTAVAIL;
	}
	/* WAIT_FIRST_FC for standard FF, else stays ISOTP_SENDING */
	WRITE_ONCE(so->tx.state, new_state);
	hrtimer_start(tx_hrt, ktime_set(hrtimer_sec, 0),
		      HRTIMER_MODE_REL_SOFT);
	spin_unlock_bh(&so->rx_lock);

	/* send the first or only CAN frame */
	cf->flags = so->ll.tx_flags;

	skb->dev = dev;
	skb->sk = sk;
	err = can_send(skb, 1);
	dev_put(dev);
	if (err) {
		pr_notice_once("can-isotp: %s: can_send_ret %pe\n",
			       __func__, ERR_PTR(err));

		spin_lock_bh(&so->rx_lock);

		/* new transfer already claimed by a concurrent completion,
		 * timeout or sendmsg() while we were stuck in can_send()?
		 */
		if (READ_ONCE(so->tx_gen) != my_gen) {
			/* don't touch timers and state of the new transfer */
			spin_unlock_bh(&so->rx_lock);
			return err;
		}

		/* no transmission -> no timeout monitoring */
		hrtimer_cancel(tx_hrt);
		goto err_out_drop_locked;
	}

	if (wait_tx_done) {
		/* wake up for:
		 * - concurrent sendmsg() claiming a new transfer
		 * - complete transmission of current PDU
		 * - shutdown state change in isotp_release()
		 * isotp_tx_gen_done() uses common tx.state/tx_gen read sequence
		 */
		err = wait_event_interruptible(so->wait,
					       isotp_tx_gen_done(so, my_gen));
		if (err)
			goto err_event_drop;

		/* still our claim, but isotp_release() force-shut it down */
		if (smp_load_acquire(&so->tx.state) == ISOTP_SHUTDOWN &&
		    READ_ONCE(so->tx_gen) == my_gen) {
			err = -EADDRNOTAVAIL;
			goto err_event_drop;
		}

		/* own completion, or tx_gen moved on - either way this is
		 * what isotp_get_tx_result() recorded for my_gen
		 */
		err = isotp_get_tx_result(so, my_gen);

		/* drain to avoid stale error for a later poll()/SO_ERROR */
		sock_error(sk);

		return err ? err : size;
	}

	return size;

err_out_drop:
	/* claimed but nothing sent yet - no timer to cancel */
	spin_lock_bh(&so->rx_lock);
	goto err_out_drop_locked;
err_event_drop:
	/* interrupted or shut down while waiting on our own transfer */
	spin_lock_bh(&so->rx_lock);

	/* new transfer already started by concurrent sendmsg()? */
	if (READ_ONCE(so->tx_gen) != my_gen) {
		/* don't touch timers and states of the new transfer */
		spin_unlock_bh(&so->rx_lock);
		return err;
	}

	hrtimer_cancel(&so->txfrtimer);
	hrtimer_cancel(&so->txtimer);
	hrtimer_cancel(&so->echotimer);
err_out_drop_locked:
	/* release the claim; so->rx_lock still held from above */
	WRITE_ONCE(so->cfecho, 0);

	/* only claim to IDLE if isotp_release() has not taken over */
	if (READ_ONCE(so->tx.state) != ISOTP_SHUTDOWN)
		WRITE_ONCE(so->tx.state, ISOTP_IDLE);
	spin_unlock_bh(&so->rx_lock);
	wake_up_interruptible(&so->wait);

	return err;
}

static int isotp_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
			 int flags)
{
	struct sock *sk = sock->sk;
	struct sk_buff *skb;
	struct isotp_sock *so = isotp_sk(sk);
	int ret = 0;

	if (flags & ~(MSG_DONTWAIT | MSG_TRUNC | MSG_PEEK | MSG_CMSG_COMPAT))
		return -EINVAL;

	if (!so->bound)
		return -EADDRNOTAVAIL;

	skb = skb_recv_datagram(sk, flags, &ret);
	if (!skb)
		return ret;

	if (size < skb->len)
		msg->msg_flags |= MSG_TRUNC;
	else
		size = skb->len;

	ret = memcpy_to_msg(msg, skb->data, size);
	if (ret < 0)
		goto out_err;

	sock_recv_cmsgs(msg, sk, skb);

	if (msg->msg_name) {
		__sockaddr_check_size(ISOTP_MIN_NAMELEN);
		msg->msg_namelen = ISOTP_MIN_NAMELEN;
		memcpy(msg->msg_name, skb->cb, msg->msg_namelen);
	}

	/* set length of return value */
	ret = (flags & MSG_TRUNC) ? skb->len : size;

out_err:
	skb_free_datagram(sk, skb);

	return ret;
}

static int isotp_release(struct socket *sock)
{
	struct sock *sk = sock->sk;
	struct isotp_sock *so;
	struct net *net;

	if (!sk)
		return 0;

	so = isotp_sk(sk);
	net = sock_net(sk);

	/* best-effort: wait for a running pdu to finish, but don't block on
	 * it forever - give up after the first signal
	 */
	while (READ_ONCE(so->tx.state) != ISOTP_IDLE &&
	       wait_event_interruptible(so->wait,
					READ_ONCE(so->tx.state) == ISOTP_IDLE) == 0)
		;

	/* claim the socket under so->rx_lock like sendmsg() does, so its
	 * claim can't race the forced ISOTP_SHUTDOWN below; force it
	 * unconditionally, even when a signal cut the wait above short
	 */
	spin_lock_bh(&so->rx_lock);
	WRITE_ONCE(so->tx.state, ISOTP_SHUTDOWN);
	spin_unlock_bh(&so->rx_lock);
	WRITE_ONCE(so->rx.state, ISOTP_IDLE);

	/* forced SHUTDOWN may have skipped IDLE (gave up on a signal) */
	wake_up_interruptible(&so->wait);

	spin_lock(&isotp_notifier_lock);
	while (isotp_busy_notifier == so) {
		spin_unlock(&isotp_notifier_lock);
		schedule_timeout_uninterruptible(1);
		spin_lock(&isotp_notifier_lock);
	}
	list_del(&so->notifier);
	spin_unlock(&isotp_notifier_lock);

	rtnl_lock();
	lock_sock(sk);

	/* remove current filters & unregister
	 * tracked reference so->dev is taken at bind() time with rtnl_lock
	 */
	if (so->bound && so->dev) {
		if (isotp_register_rxid(so))
			can_rx_unregister(net, so->dev, so->rxid,
					  SINGLE_MASK(so->rxid),
					  isotp_rcv, sk);

		can_rx_unregister(net, so->dev, so->txid,
				  SINGLE_MASK(so->txid),
				  isotp_rcv_echo, sk);
		netdev_put(so->dev, &so->dev_tracker);
	}

	so->ifindex = 0;
	so->bound = 0;
	so->dev = NULL;

	rtnl_unlock();

	/* Always wait for a grace period before touching the timers below.
	 * A concurrent NETDEV_UNREGISTER may have already unregistered our
	 * filters and cleared so->bound in isotp_notify() without waiting
	 * for in-flight isotp_rcv() callers to finish, so this call must not
	 * be skipped just because so->bound is already 0 here.
	 */
	synchronize_rcu();

	hrtimer_cancel(&so->txfrtimer);
	hrtimer_cancel(&so->txtimer);
	hrtimer_cancel(&so->echotimer);
	hrtimer_cancel(&so->rxtimer);

	sock_orphan(sk);
	sock->sk = NULL;

	release_sock(sk);
	sock_prot_inuse_add(net, sk->sk_prot, -1);
	sock_put(sk);

	return 0;
}

static int isotp_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int len)
{
	struct sockaddr_can *addr = (struct sockaddr_can *)uaddr;
	struct sock *sk = sock->sk;
	struct isotp_sock *so = isotp_sk(sk);
	struct net *net = sock_net(sk);
	int ifindex;
	struct net_device *dev;
	canid_t tx_id = addr->can_addr.tp.tx_id;
	canid_t rx_id = addr->can_addr.tp.rx_id;
	int err = 0;
	int notify_enetdown = 0;

	if (len < ISOTP_MIN_NAMELEN)
		return -EINVAL;

	if (addr->can_family != AF_CAN)
		return -EINVAL;

	/* sanitize tx CAN identifier */
	if (tx_id & CAN_EFF_FLAG)
		tx_id &= (CAN_EFF_FLAG | CAN_EFF_MASK);
	else
		tx_id &= CAN_SFF_MASK;

	/* give feedback on wrong CAN-ID value */
	if (tx_id != addr->can_addr.tp.tx_id)
		return -EINVAL;

	/* sanitize rx CAN identifier (if needed) */
	if (isotp_register_rxid(so)) {
		if (rx_id & CAN_EFF_FLAG)
			rx_id &= (CAN_EFF_FLAG | CAN_EFF_MASK);
		else
			rx_id &= CAN_SFF_MASK;

		/* give feedback on wrong CAN-ID value */
		if (rx_id != addr->can_addr.tp.rx_id)
			return -EINVAL;
	}

	if (!addr->can_ifindex)
		return -ENODEV;

	rtnl_lock();
	lock_sock(sk);

	if (so->bound) {
		err = -EINVAL;
		goto out;
	}

	/* A transmission or reception that outlived a previous binding
	 * (unbound by NETDEV_UNREGISTER) may still be draining; the FC/echo
	 * and RX watchdog timers bound how long this takes. Checked together
	 * with so->bound in the same lock_sock() section above, so there is
	 * no window in which a concurrent isotp_notify() could be missed.
	 */
	if (READ_ONCE(so->tx.state) != ISOTP_IDLE ||
	    READ_ONCE(so->rx.state) != ISOTP_IDLE) {
		err = -EAGAIN;
		goto out;
	}

	/* ensure different CAN IDs when the rx_id is to be registered */
	if (isotp_register_rxid(so) && rx_id == tx_id) {
		err = -EADDRNOTAVAIL;
		goto out;
	}

	dev = dev_get_by_index(net, addr->can_ifindex);
	if (!dev) {
		err = -ENODEV;
		goto out;
	}
	if (dev->type != ARPHRD_CAN) {
		err = -ENODEV;
		goto out_put_dev;
	}
	if (READ_ONCE(dev->mtu) < so->ll.mtu) {
		err = -EINVAL;
		goto out_put_dev;
	}
	if (!(dev->flags & IFF_UP))
		notify_enetdown = 1;

	ifindex = dev->ifindex;

	if (isotp_register_rxid(so))
		can_rx_register(net, dev, rx_id, SINGLE_MASK(rx_id),
				isotp_rcv, sk, "isotp", sk);

	/* no consecutive frame echo skb in flight */
	WRITE_ONCE(so->cfecho, 0);

	/* register for echo skb's */
	can_rx_register(net, dev, tx_id, SINGLE_MASK(tx_id),
			isotp_rcv_echo, sk, "isotpe", sk);

	/* switch to new settings */
	so->ifindex = ifindex;
	so->rxid = rx_id;
	so->txid = tx_id;
	so->bound = 1;

	/* bind() ok -> hold a reference for so->dev so that isotp_release()
	 * can safely reach the device later, even if a concurrent
	 * NETDEV_UNREGISTER has already unlisted it by ifindex.
	 */
	so->dev = dev;
	netdev_hold(so->dev, &so->dev_tracker, GFP_KERNEL);

out_put_dev:
	/* remove potential reference from dev_get_by_index() */
	dev_put(dev);
out:
	release_sock(sk);
	rtnl_unlock();

	if (notify_enetdown) {
		sk->sk_err = ENETDOWN;
		if (!sock_flag(sk, SOCK_DEAD))
			sk_error_report(sk);
	}

	return err;
}

static int isotp_getname(struct socket *sock, struct sockaddr *uaddr, int peer)
{
	struct sockaddr_can *addr = (struct sockaddr_can *)uaddr;
	struct sock *sk = sock->sk;
	struct isotp_sock *so = isotp_sk(sk);

	if (peer)
		return -EOPNOTSUPP;

	memset(addr, 0, ISOTP_MIN_NAMELEN);
	addr->can_family = AF_CAN;
	addr->can_ifindex = so->ifindex;
	addr->can_addr.tp.rx_id = so->rxid;
	addr->can_addr.tp.tx_id = so->txid;

	return ISOTP_MIN_NAMELEN;
}

static int isotp_setsockopt_locked(struct socket *sock, int level, int optname,
			    sockptr_t optval, unsigned int optlen)
{
	struct sock *sk = sock->sk;
	struct isotp_sock *so = isotp_sk(sk);
	int ret = 0;

	if (so->bound)
		return -EISCONN;

	switch (optname) {
	case CAN_ISOTP_OPTS:
		if (optlen != sizeof(struct can_isotp_options))
			return -EINVAL;

		if (copy_from_sockptr(&so->opt, optval, optlen))
			return -EFAULT;

		/* no separate rx_ext_address is given => use ext_address */
		if (!(so->opt.flags & CAN_ISOTP_RX_EXT_ADDR))
			so->opt.rx_ext_address = so->opt.ext_address;

		/* these broadcast flags are not allowed together */
		if (isotp_bc_flags(so) == ISOTP_ALL_BC_FLAGS) {
			/* CAN_ISOTP_SF_BROADCAST is prioritized */
			so->opt.flags &= ~CAN_ISOTP_CF_BROADCAST;

			/* give user feedback on wrong config attempt */
			ret = -EINVAL;
		}

		/* check for frame_txtime changes (0 => no changes) */
		if (so->opt.frame_txtime) {
			if (so->opt.frame_txtime == CAN_ISOTP_FRAME_TXTIME_ZERO)
				so->frame_txtime = 0;
			else
				so->frame_txtime = so->opt.frame_txtime;
		}
		break;

	case CAN_ISOTP_RECV_FC:
		if (optlen != sizeof(struct can_isotp_fc_options))
			return -EINVAL;

		if (copy_from_sockptr(&so->rxfc, optval, optlen))
			return -EFAULT;
		break;

	case CAN_ISOTP_TX_STMIN:
		if (optlen != sizeof(u32))
			return -EINVAL;

		if (copy_from_sockptr(&so->force_tx_stmin, optval, optlen))
			return -EFAULT;
		break;

	case CAN_ISOTP_RX_STMIN:
		if (optlen != sizeof(u32))
			return -EINVAL;

		if (copy_from_sockptr(&so->force_rx_stmin, optval, optlen))
			return -EFAULT;
		break;

	case CAN_ISOTP_LL_OPTS:
		if (optlen == sizeof(struct can_isotp_ll_options)) {
			struct can_isotp_ll_options ll;

			if (copy_from_sockptr(&ll, optval, optlen))
				return -EFAULT;

			/* check for correct ISO 11898-1 DLC data length */
			if (ll.tx_dl != padlen(ll.tx_dl))
				return -EINVAL;

			if (ll.mtu != CAN_MTU && ll.mtu != CANFD_MTU)
				return -EINVAL;

			if (ll.mtu == CAN_MTU &&
			    (ll.tx_dl > CAN_MAX_DLEN || ll.tx_flags != 0))
				return -EINVAL;

			memcpy(&so->ll, &ll, sizeof(ll));

			/* set ll_dl for tx path to similar place as for rx */
			so->tx.ll_dl = ll.tx_dl;
		} else {
			return -EINVAL;
		}
		break;

	default:
		ret = -ENOPROTOOPT;
	}

	return ret;
}

static int isotp_setsockopt(struct socket *sock, int level, int optname,
			    sockptr_t optval, unsigned int optlen)

{
	struct sock *sk = sock->sk;
	int ret;

	if (level != SOL_CAN_ISOTP)
		return -EINVAL;

	lock_sock(sk);
	ret = isotp_setsockopt_locked(sock, level, optname, optval, optlen);
	release_sock(sk);
	return ret;
}

static int isotp_getsockopt(struct socket *sock, int level, int optname,
			    char __user *optval, int __user *optlen)
{
	struct sock *sk = sock->sk;
	struct isotp_sock *so = isotp_sk(sk);
	int len;
	void *val;

	if (level != SOL_CAN_ISOTP)
		return -EINVAL;
	if (get_user(len, optlen))
		return -EFAULT;
	if (len < 0)
		return -EINVAL;

	switch (optname) {
	case CAN_ISOTP_OPTS:
		len = min_t(int, len, sizeof(struct can_isotp_options));
		val = &so->opt;
		break;

	case CAN_ISOTP_RECV_FC:
		len = min_t(int, len, sizeof(struct can_isotp_fc_options));
		val = &so->rxfc;
		break;

	case CAN_ISOTP_TX_STMIN:
		len = min_t(int, len, sizeof(u32));
		val = &so->force_tx_stmin;
		break;

	case CAN_ISOTP_RX_STMIN:
		len = min_t(int, len, sizeof(u32));
		val = &so->force_rx_stmin;
		break;

	case CAN_ISOTP_LL_OPTS:
		len = min_t(int, len, sizeof(struct can_isotp_ll_options));
		val = &so->ll;
		break;

	default:
		return -ENOPROTOOPT;
	}

	if (put_user(len, optlen))
		return -EFAULT;
	if (copy_to_user(optval, val, len))
		return -EFAULT;
	return 0;
}

static void isotp_notify(struct isotp_sock *so, unsigned long msg,
			 struct net_device *dev)
{
	struct sock *sk = &so->sk;

	if (!net_eq(dev_net(dev), sock_net(sk)))
		return;

	if (so->dev != dev)
		return;

	switch (msg) {
	case NETDEV_UNREGISTER:
		lock_sock(sk);
		/* remove current filters & unregister */
		if (so->bound) {
			if (isotp_register_rxid(so))
				can_rx_unregister(dev_net(dev), dev, so->rxid,
						  SINGLE_MASK(so->rxid),
						  isotp_rcv, sk);

			can_rx_unregister(dev_net(dev), dev, so->txid,
					  SINGLE_MASK(so->txid),
					  isotp_rcv_echo, sk);
			netdev_put(so->dev, &so->dev_tracker);
		}

		so->ifindex = 0;
		so->bound  = 0;
		so->dev = NULL;
		release_sock(sk);

		sk->sk_err = ENODEV;
		if (!sock_flag(sk, SOCK_DEAD))
			sk_error_report(sk);
		break;

	case NETDEV_DOWN:
		sk->sk_err = ENETDOWN;
		if (!sock_flag(sk, SOCK_DEAD))
			sk_error_report(sk);
		break;
	}
}

static int isotp_notifier(struct notifier_block *nb, unsigned long msg,
			  void *ptr)
{
	struct net_device *dev = netdev_notifier_info_to_dev(ptr);

	if (dev->type != ARPHRD_CAN)
		return NOTIFY_DONE;
	if (msg != NETDEV_UNREGISTER && msg != NETDEV_DOWN)
		return NOTIFY_DONE;
	if (unlikely(isotp_busy_notifier)) /* Check for reentrant bug. */
		return NOTIFY_DONE;

	spin_lock(&isotp_notifier_lock);
	list_for_each_entry(isotp_busy_notifier, &isotp_notifier_list, notifier) {
		spin_unlock(&isotp_notifier_lock);
		isotp_notify(isotp_busy_notifier, msg, dev);
		spin_lock(&isotp_notifier_lock);
	}
	isotp_busy_notifier = NULL;
	spin_unlock(&isotp_notifier_lock);
	return NOTIFY_DONE;
}

static void isotp_sock_destruct(struct sock *sk)
{
	struct isotp_sock *so = isotp_sk(sk);

	/* do the standard CAN sock destruct work */
	can_sock_destruct(sk);

	/* free potential extended PDU buffers */
	if (so->rx.buf != so->rx.sbuf)
		kfree(so->rx.buf);

	if (so->tx.buf != so->tx.sbuf)
		kfree(so->tx.buf);
}

static int isotp_init(struct sock *sk)
{
	struct isotp_sock *so = isotp_sk(sk);

	so->ifindex = 0;
	so->bound = 0;
	so->dev = NULL;

	so->opt.flags = CAN_ISOTP_DEFAULT_FLAGS;
	so->opt.ext_address = CAN_ISOTP_DEFAULT_EXT_ADDRESS;
	so->opt.rx_ext_address = CAN_ISOTP_DEFAULT_EXT_ADDRESS;
	so->opt.rxpad_content = CAN_ISOTP_DEFAULT_PAD_CONTENT;
	so->opt.txpad_content = CAN_ISOTP_DEFAULT_PAD_CONTENT;
	so->opt.frame_txtime = CAN_ISOTP_DEFAULT_FRAME_TXTIME;
	so->frame_txtime = CAN_ISOTP_DEFAULT_FRAME_TXTIME;
	so->rxfc.bs = CAN_ISOTP_DEFAULT_RECV_BS;
	so->rxfc.stmin = CAN_ISOTP_DEFAULT_RECV_STMIN;
	so->rxfc.wftmax = CAN_ISOTP_DEFAULT_RECV_WFTMAX;
	so->ll.mtu = CAN_ISOTP_DEFAULT_LL_MTU;
	so->ll.tx_dl = CAN_ISOTP_DEFAULT_LL_TX_DL;
	so->ll.tx_flags = CAN_ISOTP_DEFAULT_LL_TX_FLAGS;

	/* set ll_dl for tx path to similar place as for rx */
	so->tx.ll_dl = so->ll.tx_dl;

	so->rx.state = ISOTP_IDLE;
	so->tx.state = ISOTP_IDLE;

	so->rx.buf = so->rx.sbuf;
	so->tx.buf = so->tx.sbuf;
	so->rx.buflen = ARRAY_SIZE(so->rx.sbuf);
	so->tx.buflen = ARRAY_SIZE(so->tx.sbuf);

	hrtimer_setup(&so->rxtimer, isotp_rx_timer_handler,
		      CLOCK_MONOTONIC, HRTIMER_MODE_REL_SOFT);
	hrtimer_setup(&so->txtimer, isotp_tx_timer_handler,
		      CLOCK_MONOTONIC, HRTIMER_MODE_REL_SOFT);
	hrtimer_setup(&so->echotimer, isotp_echo_timer_handler,
		      CLOCK_MONOTONIC, HRTIMER_MODE_REL_SOFT);
	hrtimer_setup(&so->txfrtimer, isotp_txfr_timer_handler,
		      CLOCK_MONOTONIC, HRTIMER_MODE_REL_SOFT);

	init_waitqueue_head(&so->wait);
	spin_lock_init(&so->rx_lock);

	spin_lock(&isotp_notifier_lock);
	list_add_tail(&so->notifier, &isotp_notifier_list);
	spin_unlock(&isotp_notifier_lock);

	/* re-assign default can_sock_destruct() reference */
	sk->sk_destruct = isotp_sock_destruct;

	return 0;
}

static __poll_t isotp_poll(struct file *file, struct socket *sock, poll_table *wait)
{
	struct sock *sk = sock->sk;
	struct isotp_sock *so = isotp_sk(sk);

	__poll_t mask = datagram_poll(file, sock, wait);
	poll_wait(file, &so->wait, wait);

	/* Check for false positives due to TX state */
	if ((mask & EPOLLWRNORM) && (READ_ONCE(so->tx.state) != ISOTP_IDLE))
		mask &= ~(EPOLLOUT | EPOLLWRNORM);

	return mask;
}

static int isotp_sock_no_ioctlcmd(struct socket *sock, unsigned int cmd,
				  unsigned long arg)
{
	/* no ioctls for socket layer -> hand it down to NIC layer */
	return -ENOIOCTLCMD;
}

static const struct proto_ops isotp_ops = {
	.family = PF_CAN,
	.release = isotp_release,
	.bind = isotp_bind,
	.connect = sock_no_connect,
	.socketpair = sock_no_socketpair,
	.accept = sock_no_accept,
	.getname = isotp_getname,
	.poll = isotp_poll,
	.ioctl = isotp_sock_no_ioctlcmd,
	.gettstamp = sock_gettstamp,
	.listen = sock_no_listen,
	.shutdown = sock_no_shutdown,
	.setsockopt = isotp_setsockopt,
	.getsockopt = isotp_getsockopt,
	.sendmsg = isotp_sendmsg,
	.recvmsg = isotp_recvmsg,
	.mmap = sock_no_mmap,
};

static struct proto isotp_proto __read_mostly = {
	.name = "CAN_ISOTP",
	.owner = THIS_MODULE,
	.obj_size = sizeof(struct isotp_sock),
	.init = isotp_init,
};

static const struct can_proto isotp_can_proto = {
	.type = SOCK_DGRAM,
	.protocol = CAN_ISOTP,
	.ops = &isotp_ops,
	.prot = &isotp_proto,
};

static struct notifier_block canisotp_notifier = {
	.notifier_call = isotp_notifier
};

static __init int isotp_module_init(void)
{
	int err;

	max_pdu_size = max_t(unsigned int, max_pdu_size, MAX_12BIT_PDU_SIZE);
	max_pdu_size = min_t(unsigned int, max_pdu_size, MAX_PDU_SIZE);

	pr_info("can: isotp protocol (max_pdu_size %d)\n", max_pdu_size);

	err = register_netdevice_notifier(&canisotp_notifier);
	if (err)
		return err;

	err = can_proto_register(&isotp_can_proto);
	if (err < 0) {
		pr_err("can: registration of isotp protocol failed %pe\n", ERR_PTR(err));
		unregister_netdevice_notifier(&canisotp_notifier);
		return err;
	}

	return 0;
}

static __exit void isotp_module_exit(void)
{
	can_proto_unregister(&isotp_can_proto);
	unregister_netdevice_notifier(&canisotp_notifier);
}

module_init(isotp_module_init);
module_exit(isotp_module_exit);