// 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 */

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;
        canid_t txid;
        canid_t rxid;
        ktime_t tx_gap;
        ktime_t lastrxcf_tstamp;
        struct hrtimer rxtimer, txtimer, txfrtimer;
        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 */
        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;

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 (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 */
                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;

        if (sock_queue_rcv_skb_reason(sk, skb, &reason) < 0)
                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;

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

        hrtimer_cancel(&so->txtimer);

        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);

                so->tx.state = ISOTP_IDLE;
                wake_up_interruptible(&so->wait);
                return 1;
        }

        /* get static/dynamic communication params from first/every FC frame */
        if (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);
                so->tx.state = ISOTP_WAIT_FC;
        }

        switch (cf->data[ae] & 0x0F) {
        case ISOTP_FC_CTS:
                so->tx.bs = 0;
                so->tx.state = ISOTP_SENDING;
                /* send CF frame and enable echo timeout handling */
                hrtimer_start(&so->txtimer, 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' */
                sk->sk_err = EMSGSIZE;
                if (!sock_flag(sk, SOCK_DEAD))
                        sk_error_report(sk);
                fallthrough;

        default:
                /* stop this tx job */
                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);
        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);
        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;
        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 (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);

        /* 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 */
                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 */
                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 ((so->tx.state != ISOTP_IDLE && n_pci_type != N_PCI_FC) ||
                    (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;

        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;

        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);

        /* cfecho should have been zero'ed by init/isotp_rcv_echo() */
        if (so->cfecho)
                pr_notice_once("can-isotp: cfecho is %08X != 0\n", so->cfecho);

        /* set consecutive frame echo tag */
        so->cfecho = *(u32 *)cf->data;

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

        /* only handle my own local echo CF/SF skb's (no FF!) */
        if (skb->sk != sk || so->cfecho != *(u32 *)cf->data)
                return;

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

        /* local echo skb with consecutive frame has been consumed */
        so->cfecho = 0;

        if (so->tx.idx >= so->tx.len) {
                /* we are done */
                so->tx.state = ISOTP_IDLE;
                wake_up_interruptible(&so->wait);
                return;
        }

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

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

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

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;

        /* don't handle timeouts in IDLE or SHUTDOWN state */
        if (so->tx.state == ISOTP_IDLE || so->tx.state == ISOTP_SHUTDOWN)
                return HRTIMER_NORESTART;

        /* we did not get any flow control or echo frame in time */

        /* report 'communication error on send' */
        sk->sk_err = ECOMM;
        if (!sock_flag(sk, SOCK_DEAD))
                sk_error_report(sk);

        /* reset tx state */
        so->tx.state = ISOTP_IDLE;
        wake_up_interruptible(&so->wait);

        return HRTIMER_NORESTART;
}

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->txtimer, ktime_set(ISOTP_ECHO_TIMEOUT, 0),
                      HRTIMER_MODE_REL_SOFT);

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

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

        while (cmpxchg(&so->tx.state, ISOTP_IDLE, ISOTP_SENDING) != ISOTP_IDLE) {
                /* we do not support multiple buffers - for now */
                if (msg->msg_flags & MSG_DONTWAIT)
                        return -EAGAIN;

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

                /* wait for complete transmission of current pdu */
                err = wait_event_interruptible(so->wait, so->tx.state == ISOTP_IDLE);
                if (err)
                        goto err_event_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;

        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() */
        if (so->cfecho)
                pr_notice_once("can-isotp: uninit cfecho %08X\n", so->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) */
                so->cfecho = *(u32 *)cf->data;
        } 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) */
                        so->cfecho = *(u32 *)cf->data;
                } else {
                        /* standard flow control check */
                        so->tx.state = ISOTP_WAIT_FIRST_FC;

                        /* start timeout for FC */
                        hrtimer_sec = ISOTP_FC_TIMEOUT;

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

        hrtimer_start(&so->txtimer, ktime_set(hrtimer_sec, 0),
                      HRTIMER_MODE_REL_SOFT);

        /* 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));

                /* no transmission -> no timeout monitoring */
                hrtimer_cancel(&so->txtimer);

                /* reset consecutive frame echo tag */
                so->cfecho = 0;

                goto err_out_drop;
        }

        if (wait_tx_done) {
                /* wait for complete transmission of current pdu */
                err = wait_event_interruptible(so->wait, so->tx.state == ISOTP_IDLE);
                if (err)
                        goto err_event_drop;

                err = sock_error(sk);
                if (err)
                        return err;
        }

        return size;

err_event_drop:
        /* got signal: force tx state machine to be idle */
        so->tx.state = ISOTP_IDLE;
        hrtimer_cancel(&so->txfrtimer);
        hrtimer_cancel(&so->txtimer);
err_out_drop:
        /* drop this PDU and unlock a potential wait queue */
        so->tx.state = ISOTP_IDLE;
        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);

        /* wait for complete transmission of current pdu */
        while (wait_event_interruptible(so->wait, so->tx.state == ISOTP_IDLE) == 0 &&
               cmpxchg(&so->tx.state, ISOTP_IDLE, ISOTP_SHUTDOWN) != ISOTP_IDLE)
                ;

        /* force state machines to be idle also when a signal occurred */
        so->tx.state = ISOTP_SHUTDOWN;
        so->rx.state = ISOTP_IDLE;

        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);

        lock_sock(sk);

        /* remove current filters & unregister */
        if (so->bound) {
                if (so->ifindex) {
                        struct net_device *dev;

                        dev = dev_get_by_index(net, so->ifindex);
                        if (dev) {
                                if (isotp_register_rxid(so))
                                        can_rx_unregister(net, dev, so->rxid,
                                                          SINGLE_MASK(so->rxid),
                                                          isotp_rcv, sk);

                                can_rx_unregister(net, dev, so->txid,
                                                  SINGLE_MASK(so->txid),
                                                  isotp_rcv_echo, sk);
                                dev_put(dev);
                                synchronize_rcu();
                        }
                }
        }

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

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

        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;

        lock_sock(sk);

        if (so->bound) {
                err = -EINVAL;
                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) {
                dev_put(dev);
                err = -ENODEV;
                goto out;
        }
        if (READ_ONCE(dev->mtu) < so->ll.mtu) {
                dev_put(dev);
                err = -EINVAL;
                goto out;
        }
        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 */
        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);

        dev_put(dev);

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

out:
        release_sock(sk);

        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->ifindex != dev->ifindex)
                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);
                }

                so->ifindex = 0;
                so->bound  = 0;
                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->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->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) && (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 = can_proto_register(&isotp_can_proto);
        if (err < 0)
                pr_err("can: registration of isotp protocol failed %pe\n", ERR_PTR(err));
        else
                register_netdevice_notifier(&canisotp_notifier);

        return err;
}

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);