// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  linux/drivers/net/netconsole.c
 *
 *  Copyright (C) 2001  Ingo Molnar <mingo@redhat.com>
 *
 *  This file contains the implementation of an IRQ-safe, crash-safe
 *  kernel console implementation that outputs kernel messages to the
 *  network.
 *
 * Modification history:
 *
 * 2001-09-17    started by Ingo Molnar.
 * 2003-08-11    2.6 port by Matt Mackall
 *               simplified options
 *               generic card hooks
 *               works non-modular
 * 2003-09-07    rewritten with netpoll api
 */

/****************************************************************
 *
 ****************************************************************/

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/mm.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/console.h>
#include <linux/moduleparam.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/netpoll.h>
#include <linux/inet.h>
#include <linux/configfs.h>
#include <linux/etherdevice.h>
#include <linux/hex.h>
#include <linux/u64_stats_sync.h>
#include <linux/utsname.h>
#include <linux/rtnetlink.h>
#include <linux/workqueue.h>

MODULE_AUTHOR("Matt Mackall <mpm@selenic.com>");
MODULE_DESCRIPTION("Console driver for network interfaces");
MODULE_LICENSE("GPL");

#define MAX_PARAM_LENGTH                256
#define MAX_EXTRADATA_ENTRY_LEN         256
#define MAX_EXTRADATA_VALUE_LEN 200
/* The number 3 comes from userdata entry format characters (' ', '=', '\n') */
#define MAX_EXTRADATA_NAME_LEN          (MAX_EXTRADATA_ENTRY_LEN - \
                                        MAX_EXTRADATA_VALUE_LEN - 3)
#define MAX_USERDATA_ITEMS              256
#define MAX_PRINT_CHUNK                 1000

static char config[MAX_PARAM_LENGTH];
module_param_string(netconsole, config, MAX_PARAM_LENGTH, 0);
MODULE_PARM_DESC(netconsole, " netconsole=[src-port]@[src-ip]/[dev],[tgt-port]@<tgt-ip>/[tgt-macaddr]");

static bool oops_only;
module_param(oops_only, bool, 0600);
MODULE_PARM_DESC(oops_only, "Only log oops messages");

#define NETCONSOLE_PARAM_TARGET_PREFIX "cmdline"

#ifndef MODULE
static int __init option_setup(char *opt)
{
        strscpy(config, opt, MAX_PARAM_LENGTH);
        return 1;
}
__setup("netconsole=", option_setup);
#endif  /* MODULE */

/* Linked list of all configured targets */
static LIST_HEAD(target_list);
/* target_cleanup_list is used to track targets that need to be cleaned outside
 * of target_list_lock. It should be cleaned in the same function it is
 * populated.
 */
static LIST_HEAD(target_cleanup_list);

/* This needs to be a spinlock because write_msg() cannot sleep */
static DEFINE_SPINLOCK(target_list_lock);
/* This needs to be a mutex because netpoll_cleanup might sleep */
static DEFINE_MUTEX(target_cleanup_list_lock);

static struct workqueue_struct *netconsole_wq;

/*
 * Console driver for netconsoles.  Register only consoles that have
 * an associated target of the same type.
 */
static struct console netconsole_ext, netconsole;

struct netconsole_target_stats  {
        u64_stats_t xmit_drop_count;
        u64_stats_t enomem_count;
        struct u64_stats_sync syncp;
};

enum console_type {
        CONS_BASIC = BIT(0),
        CONS_EXTENDED = BIT(1),
};

/* Features enabled in sysdata. Contrary to userdata, this data is populated by
 * the kernel. The fields are designed as bitwise flags, allowing multiple
 * features to be set in sysdata_fields.
 */
enum sysdata_feature {
        /* Populate the CPU that sends the message */
        SYSDATA_CPU_NR = BIT(0),
        /* Populate the task name (as in current->comm) in sysdata */
        SYSDATA_TASKNAME = BIT(1),
        /* Kernel release/version as part of sysdata */
        SYSDATA_RELEASE = BIT(2),
        /* Include a per-target message ID as part of sysdata */
        SYSDATA_MSGID = BIT(3),
        /* Sentinel: highest bit position */
        MAX_SYSDATA_ITEMS = 4,
};

enum target_state {
        STATE_DISABLED,
        STATE_ENABLED,
        STATE_DEACTIVATED,
};

/**
 * struct netconsole_target - Represents a configured netconsole target.
 * @list:       Links this target into the target_list.
 * @group:      Links us into the configfs subsystem hierarchy.
 * @userdata_group:     Links to the userdata configfs hierarchy
 * @userdata:           Cached, formatted string of append
 * @userdata_length:    String length of userdata.
 * @sysdata:            Cached, formatted string of append
 * @sysdata_fields:     Sysdata features enabled.
 * @msgcounter: Message sent counter.
 * @stats:      Packet send stats for the target. Used for debugging.
 * @state:      State of the target.
 *              Visible from userspace (read-write).
 *              From a userspace perspective, the target is either enabled or
 *              disabled. Internally, although both STATE_DISABLED and
 *              STATE_DEACTIVATED correspond to inactive targets, the latter is
 *              due to automatic interface state changes and will try
 *              recover automatically, if the interface comes back
 *              online.
 *              Also, other parameters of a target may be modified at
 *              runtime only when it is disabled (state != STATE_ENABLED).
 * @extended:   Denotes whether console is extended or not.
 * @release:    Denotes whether kernel release version should be prepended
 *              to the message. Depends on extended console.
 * @np:         The netpoll structure for this target.
 *              Contains the other userspace visible parameters:
 *              dev_name        (read-write)
 *              local_port      (read-write)
 *              remote_port     (read-write)
 *              local_ip        (read-write)
 *              remote_ip       (read-write)
 *              local_mac       (read-only)
 *              remote_mac      (read-write)
 * @buf:        The buffer used to send the full msg to the network stack
 * @resume_wq:  Workqueue to resume deactivated target
 */
struct netconsole_target {
        struct list_head        list;
#ifdef  CONFIG_NETCONSOLE_DYNAMIC
        struct config_group     group;
        struct config_group     userdata_group;
        char                    *userdata;
        size_t                  userdata_length;
        char                    sysdata[MAX_EXTRADATA_ENTRY_LEN * MAX_SYSDATA_ITEMS];

        /* bit-wise with sysdata_feature bits */
        u32                     sysdata_fields;
        /* protected by target_list_lock */
        u32                     msgcounter;
#endif
        struct netconsole_target_stats stats;
        enum target_state       state;
        bool                    extended;
        bool                    release;
        struct netpoll          np;
        /* protected by target_list_lock */
        char                    buf[MAX_PRINT_CHUNK];
        struct work_struct      resume_wq;
};

#ifdef  CONFIG_NETCONSOLE_DYNAMIC

static struct configfs_subsystem netconsole_subsys;
static DEFINE_MUTEX(dynamic_netconsole_mutex);

static int __init dynamic_netconsole_init(void)
{
        config_group_init(&netconsole_subsys.su_group);
        mutex_init(&netconsole_subsys.su_mutex);
        return configfs_register_subsystem(&netconsole_subsys);
}

static void __exit dynamic_netconsole_exit(void)
{
        configfs_unregister_subsystem(&netconsole_subsys);
}

/*
 * Targets that were created by parsing the boot/module option string
 * do not exist in the configfs hierarchy (and have NULL names) and will
 * never go away, so make these a no-op for them.
 */
static void netconsole_target_get(struct netconsole_target *nt)
{
        if (config_item_name(&nt->group.cg_item))
                config_group_get(&nt->group);
}

static void netconsole_target_put(struct netconsole_target *nt)
{
        if (config_item_name(&nt->group.cg_item))
                config_group_put(&nt->group);
}

static void dynamic_netconsole_mutex_lock(void)
{
        mutex_lock(&dynamic_netconsole_mutex);
}

static void dynamic_netconsole_mutex_unlock(void)
{
        mutex_unlock(&dynamic_netconsole_mutex);
}

#else   /* !CONFIG_NETCONSOLE_DYNAMIC */

static int __init dynamic_netconsole_init(void)
{
        return 0;
}

static void __exit dynamic_netconsole_exit(void)
{
}

/*
 * No danger of targets going away from under us when dynamic
 * reconfigurability is off.
 */
static void netconsole_target_get(struct netconsole_target *nt)
{
}

static void netconsole_target_put(struct netconsole_target *nt)
{
}

static void populate_configfs_item(struct netconsole_target *nt,
                                   int cmdline_count)
{
}

static void dynamic_netconsole_mutex_lock(void)
{
}

static void dynamic_netconsole_mutex_unlock(void)
{
}

#endif  /* CONFIG_NETCONSOLE_DYNAMIC */

/* Check if the target was bound by mac address. */
static bool bound_by_mac(struct netconsole_target *nt)
{
        return is_valid_ether_addr(nt->np.dev_mac);
}

/* Attempts to resume logging to a deactivated target. */
static void resume_target(struct netconsole_target *nt)
{
        if (netpoll_setup(&nt->np)) {
                /* netpoll fails setup once, do not try again. */
                nt->state = STATE_DISABLED;
                return;
        }

        nt->state = STATE_ENABLED;
        pr_info("network logging resumed on interface %s\n", nt->np.dev_name);
}

/* Checks if a deactivated target matches a device. */
static bool deactivated_target_match(struct netconsole_target *nt,
                                     struct net_device *ndev)
{
        if (nt->state != STATE_DEACTIVATED)
                return false;

        if (bound_by_mac(nt))
                return !memcmp(nt->np.dev_mac, ndev->dev_addr, ETH_ALEN);
        return !strncmp(nt->np.dev_name, ndev->name, IFNAMSIZ);
}

/* Process work scheduled for target resume. */
static void process_resume_target(struct work_struct *work)
{
        struct netconsole_target *nt;
        unsigned long flags;

        nt = container_of(work, struct netconsole_target, resume_wq);

        dynamic_netconsole_mutex_lock();

        spin_lock_irqsave(&target_list_lock, flags);
        /* Check if target is still deactivated as it may have been disabled
         * while resume was being scheduled.
         */
        if (nt->state != STATE_DEACTIVATED) {
                spin_unlock_irqrestore(&target_list_lock, flags);
                goto out_unlock;
        }

        /* resume_target is IRQ unsafe, remove target from
         * target_list in order to resume it with IRQ enabled.
         */
        list_del_init(&nt->list);
        spin_unlock_irqrestore(&target_list_lock, flags);

        resume_target(nt);

        /* At this point the target is either enabled or disabled and
         * was cleaned up before getting deactivated. Either way, add it
         * back to target list.
         */
        spin_lock_irqsave(&target_list_lock, flags);
        list_add(&nt->list, &target_list);
        spin_unlock_irqrestore(&target_list_lock, flags);

out_unlock:
        dynamic_netconsole_mutex_unlock();
}

/* Allocate and initialize with defaults.
 * Note that these targets get their config_item fields zeroed-out.
 */
static struct netconsole_target *alloc_and_init(void)
{
        struct netconsole_target *nt;

        nt = kzalloc_obj(*nt);
        if (!nt)
                return nt;

        if (IS_ENABLED(CONFIG_NETCONSOLE_EXTENDED_LOG))
                nt->extended = true;
        if (IS_ENABLED(CONFIG_NETCONSOLE_PREPEND_RELEASE))
                nt->release = true;

        nt->np.name = "netconsole";
        strscpy(nt->np.dev_name, "eth0", IFNAMSIZ);
        nt->np.local_port = 6665;
        nt->np.remote_port = 6666;
        eth_broadcast_addr(nt->np.remote_mac);
        nt->state = STATE_DISABLED;
        INIT_WORK(&nt->resume_wq, process_resume_target);

        return nt;
}

/* Clean up every target in the cleanup_list and move the clean targets back to
 * the main target_list.
 */
static void netconsole_process_cleanups_core(void)
{
        struct netconsole_target *nt, *tmp;
        unsigned long flags;

        /* The cleanup needs RTNL locked */
        ASSERT_RTNL();

        mutex_lock(&target_cleanup_list_lock);
        list_for_each_entry_safe(nt, tmp, &target_cleanup_list, list) {
                /* all entries in the cleanup_list needs to be disabled */
                WARN_ON_ONCE(nt->state == STATE_ENABLED);
                do_netpoll_cleanup(&nt->np);
                if (bound_by_mac(nt))
                        memset(&nt->np.dev_name, 0, IFNAMSIZ);
                /* moved the cleaned target to target_list. Need to hold both
                 * locks
                 */
                spin_lock_irqsave(&target_list_lock, flags);
                list_move(&nt->list, &target_list);
                spin_unlock_irqrestore(&target_list_lock, flags);
        }
        WARN_ON_ONCE(!list_empty(&target_cleanup_list));
        mutex_unlock(&target_cleanup_list_lock);
}

static void netconsole_print_banner(struct netpoll *np)
{
        np_info(np, "local port %d\n", np->local_port);
        if (np->ipv6)
                np_info(np, "local IPv6 address %pI6c\n", &np->local_ip.in6);
        else
                np_info(np, "local IPv4 address %pI4\n", &np->local_ip.ip);
        np_info(np, "interface name '%s'\n", np->dev_name);
        np_info(np, "local ethernet address '%pM'\n", np->dev_mac);
        np_info(np, "remote port %d\n", np->remote_port);
        if (np->ipv6)
                np_info(np, "remote IPv6 address %pI6c\n", &np->remote_ip.in6);
        else
                np_info(np, "remote IPv4 address %pI4\n", &np->remote_ip.ip);
        np_info(np, "remote ethernet address %pM\n", np->remote_mac);
}

/* Parse the string and populate the `inet_addr` union. Return 0 if IPv4 is
 * populated, 1 if IPv6 is populated, and -1 upon failure.
 */
static int netpoll_parse_ip_addr(const char *str, union inet_addr *addr)
{
        const char *end = NULL;
        int len;

        len = strlen(str);
        if (!len)
                return -1;

        if (str[len - 1] == '\n')
                len -= 1;

        if (in4_pton(str, len, (void *)addr, -1, &end) > 0 &&
            (!end || *end == 0 || *end == '\n'))
                return 0;

        if (IS_ENABLED(CONFIG_IPV6) &&
            in6_pton(str, len, (void *)addr, -1, &end) > 0 &&
            (!end || *end == 0 || *end == '\n'))
                return 1;

        return -1;
}

#ifdef  CONFIG_NETCONSOLE_DYNAMIC

/*
 * Our subsystem hierarchy is:
 *
 * /sys/kernel/config/netconsole/
 *                              |
 *                              <target>/
 *                              |       enabled
 *                              |       release
 *                              |       dev_name
 *                              |       local_port
 *                              |       remote_port
 *                              |       local_ip
 *                              |       remote_ip
 *                              |       local_mac
 *                              |       remote_mac
 *                              |       transmit_errors
 *                              |       userdata/
 *                              |               <key>/
 *                              |                       value
 *                              |               ...
 *                              |
 *                              <target>/...
 */

static struct netconsole_target *to_target(struct config_item *item)
{
        struct config_group *cfg_group;

        cfg_group = to_config_group(item);
        if (!cfg_group)
                return NULL;
        return container_of(to_config_group(item),
                            struct netconsole_target, group);
}

/* Do the list cleanup with the rtnl lock hold.  rtnl lock is necessary because
 * netdev might be cleaned-up by calling __netpoll_cleanup(),
 */
static void netconsole_process_cleanups(void)
{
        /* rtnl lock is called here, because it has precedence over
         * target_cleanup_list_lock mutex and target_cleanup_list
         */
        rtnl_lock();
        netconsole_process_cleanups_core();
        rtnl_unlock();
}

/* Get rid of possible trailing newline, returning the new length */
static void trim_newline(char *s, size_t maxlen)
{
        size_t len;

        len = strnlen(s, maxlen);
        if (s[len - 1] == '\n')
                s[len - 1] = '\0';
}

/*
 * Attribute operations for netconsole_target.
 */

static ssize_t enabled_show(struct config_item *item, char *buf)
{
        return sysfs_emit(buf, "%d\n", to_target(item)->state == STATE_ENABLED);
}

static ssize_t extended_show(struct config_item *item, char *buf)
{
        return sysfs_emit(buf, "%d\n", to_target(item)->extended);
}

static ssize_t release_show(struct config_item *item, char *buf)
{
        return sysfs_emit(buf, "%d\n", to_target(item)->release);
}

static ssize_t dev_name_show(struct config_item *item, char *buf)
{
        return sysfs_emit(buf, "%s\n", to_target(item)->np.dev_name);
}

static ssize_t local_port_show(struct config_item *item, char *buf)
{
        return sysfs_emit(buf, "%d\n", to_target(item)->np.local_port);
}

static ssize_t remote_port_show(struct config_item *item, char *buf)
{
        return sysfs_emit(buf, "%d\n", to_target(item)->np.remote_port);
}

static ssize_t local_ip_show(struct config_item *item, char *buf)
{
        struct netconsole_target *nt = to_target(item);

        if (nt->np.ipv6)
                return sysfs_emit(buf, "%pI6c\n", &nt->np.local_ip.in6);
        else
                return sysfs_emit(buf, "%pI4\n", &nt->np.local_ip);
}

static ssize_t remote_ip_show(struct config_item *item, char *buf)
{
        struct netconsole_target *nt = to_target(item);

        if (nt->np.ipv6)
                return sysfs_emit(buf, "%pI6c\n", &nt->np.remote_ip.in6);
        else
                return sysfs_emit(buf, "%pI4\n", &nt->np.remote_ip);
}

static ssize_t local_mac_show(struct config_item *item, char *buf)
{
        struct net_device *dev = to_target(item)->np.dev;
        static const u8 bcast[ETH_ALEN] = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };

        return sysfs_emit(buf, "%pM\n", dev ? dev->dev_addr : bcast);
}

static ssize_t remote_mac_show(struct config_item *item, char *buf)
{
        return sysfs_emit(buf, "%pM\n", to_target(item)->np.remote_mac);
}

static ssize_t transmit_errors_show(struct config_item *item, char *buf)
{
        struct netconsole_target *nt = to_target(item);
        u64 xmit_drop_count, enomem_count;
        unsigned int start;

        do {
                start = u64_stats_fetch_begin(&nt->stats.syncp);
                xmit_drop_count = u64_stats_read(&nt->stats.xmit_drop_count);
                enomem_count = u64_stats_read(&nt->stats.enomem_count);
        } while (u64_stats_fetch_retry(&nt->stats.syncp, start));

        return sysfs_emit(buf, "%llu\n", xmit_drop_count + enomem_count);
}

/* configfs helper to display if cpu_nr sysdata feature is enabled */
static ssize_t sysdata_cpu_nr_enabled_show(struct config_item *item, char *buf)
{
        struct netconsole_target *nt = to_target(item->ci_parent);
        bool cpu_nr_enabled;

        dynamic_netconsole_mutex_lock();
        cpu_nr_enabled = !!(nt->sysdata_fields & SYSDATA_CPU_NR);
        dynamic_netconsole_mutex_unlock();

        return sysfs_emit(buf, "%d\n", cpu_nr_enabled);
}

/* configfs helper to display if taskname sysdata feature is enabled */
static ssize_t sysdata_taskname_enabled_show(struct config_item *item,
                                             char *buf)
{
        struct netconsole_target *nt = to_target(item->ci_parent);
        bool taskname_enabled;

        dynamic_netconsole_mutex_lock();
        taskname_enabled = !!(nt->sysdata_fields & SYSDATA_TASKNAME);
        dynamic_netconsole_mutex_unlock();

        return sysfs_emit(buf, "%d\n", taskname_enabled);
}

static ssize_t sysdata_release_enabled_show(struct config_item *item,
                                            char *buf)
{
        struct netconsole_target *nt = to_target(item->ci_parent);
        bool release_enabled;

        dynamic_netconsole_mutex_lock();
        release_enabled = !!(nt->sysdata_fields & SYSDATA_RELEASE);
        dynamic_netconsole_mutex_unlock();

        return sysfs_emit(buf, "%d\n", release_enabled);
}

/* Iterate in the list of target, and make sure we don't have any console
 * register without targets of the same type
 */
static void unregister_netcons_consoles(void)
{
        struct netconsole_target *nt;
        u32 console_type_needed = 0;
        unsigned long flags;

        spin_lock_irqsave(&target_list_lock, flags);
        list_for_each_entry(nt, &target_list, list) {
                if (nt->extended)
                        console_type_needed |= CONS_EXTENDED;
                else
                        console_type_needed |= CONS_BASIC;
        }
        spin_unlock_irqrestore(&target_list_lock, flags);

        if (!(console_type_needed & CONS_EXTENDED) &&
            console_is_registered(&netconsole_ext))
                unregister_console(&netconsole_ext);

        if (!(console_type_needed & CONS_BASIC) &&
            console_is_registered(&netconsole))
                unregister_console(&netconsole);
}

static ssize_t sysdata_msgid_enabled_show(struct config_item *item,
                                          char *buf)
{
        struct netconsole_target *nt = to_target(item->ci_parent);
        bool msgid_enabled;

        dynamic_netconsole_mutex_lock();
        msgid_enabled = !!(nt->sysdata_fields & SYSDATA_MSGID);
        dynamic_netconsole_mutex_unlock();

        return sysfs_emit(buf, "%d\n", msgid_enabled);
}

/*
 * This one is special -- targets created through the configfs interface
 * are not enabled (and the corresponding netpoll activated) by default.
 * The user is expected to set the desired parameters first (which
 * would enable him to dynamically add new netpoll targets for new
 * network interfaces as and when they come up).
 */
static ssize_t enabled_store(struct config_item *item,
                const char *buf, size_t count)
{
        struct netconsole_target *nt = to_target(item);
        bool enabled, current_enabled;
        unsigned long flags;
        ssize_t ret;

        dynamic_netconsole_mutex_lock();
        ret = kstrtobool(buf, &enabled);
        if (ret)
                goto out_unlock;

        /* When the user explicitly enables or disables a target that is
         * currently deactivated, reset its state to disabled. The DEACTIVATED
         * state only tracks interface-driven deactivation and should _not_
         * persist when the user manually changes the target's enabled state.
         */
        if (nt->state == STATE_DEACTIVATED)
                nt->state = STATE_DISABLED;

        ret = -EINVAL;
        current_enabled = nt->state == STATE_ENABLED;
        if (enabled == current_enabled) {
                pr_info("network logging has already %s\n",
                        current_enabled ? "started" : "stopped");
                goto out_unlock;
        }

        if (enabled) {  /* true */
                if (nt->release && !nt->extended) {
                        pr_err("Not enabling netconsole. Release feature requires extended log message");
                        goto out_unlock;
                }

                if (nt->extended && !console_is_registered(&netconsole_ext)) {
                        netconsole_ext.flags |= CON_ENABLED;
                        register_console(&netconsole_ext);
                }

                /* User might be enabling the basic format target for the very
                 * first time, make sure the console is registered.
                 */
                if (!nt->extended && !console_is_registered(&netconsole)) {
                        netconsole.flags |= CON_ENABLED;
                        register_console(&netconsole);
                }

                /*
                 * Skip netconsole_parser_cmdline() -- all the attributes are
                 * already configured via configfs. Just print them out.
                 */
                netconsole_print_banner(&nt->np);

                ret = netpoll_setup(&nt->np);
                if (ret)
                        goto out_unlock;

                nt->state = STATE_ENABLED;
                pr_info("network logging started\n");
        } else {        /* false */
                /* We need to disable the netconsole before cleaning it up
                 * otherwise we might end up in write_msg() with
                 * nt->np.dev == NULL and nt->state == STATE_ENABLED
                 */
                mutex_lock(&target_cleanup_list_lock);
                spin_lock_irqsave(&target_list_lock, flags);
                nt->state = STATE_DISABLED;
                /* Remove the target from the list, while holding
                 * target_list_lock
                 */
                list_move(&nt->list, &target_cleanup_list);
                spin_unlock_irqrestore(&target_list_lock, flags);
                mutex_unlock(&target_cleanup_list_lock);
                /* Unregister consoles, whose the last target of that type got
                 * disabled.
                 */
                unregister_netcons_consoles();
        }

        ret = strnlen(buf, count);
        /* Deferred cleanup */
        netconsole_process_cleanups();
out_unlock:
        dynamic_netconsole_mutex_unlock();
        return ret;
}

static ssize_t release_store(struct config_item *item, const char *buf,
                             size_t count)
{
        struct netconsole_target *nt = to_target(item);
        bool release;
        ssize_t ret;

        dynamic_netconsole_mutex_lock();
        if (nt->state == STATE_ENABLED) {
                pr_err("target (%s) is enabled, disable to update parameters\n",
                       config_item_name(&nt->group.cg_item));
                ret = -EINVAL;
                goto out_unlock;
        }

        ret = kstrtobool(buf, &release);
        if (ret)
                goto out_unlock;

        nt->release = release;

        ret = strnlen(buf, count);
out_unlock:
        dynamic_netconsole_mutex_unlock();
        return ret;
}

static ssize_t extended_store(struct config_item *item, const char *buf,
                size_t count)
{
        struct netconsole_target *nt = to_target(item);
        bool extended;
        ssize_t ret;

        dynamic_netconsole_mutex_lock();
        if (nt->state == STATE_ENABLED)  {
                pr_err("target (%s) is enabled, disable to update parameters\n",
                       config_item_name(&nt->group.cg_item));
                ret = -EINVAL;
                goto out_unlock;
        }

        ret = kstrtobool(buf, &extended);
        if (ret)
                goto out_unlock;

        nt->extended = extended;
        ret = strnlen(buf, count);
out_unlock:
        dynamic_netconsole_mutex_unlock();
        return ret;
}

static ssize_t dev_name_store(struct config_item *item, const char *buf,
                size_t count)
{
        struct netconsole_target *nt = to_target(item);

        dynamic_netconsole_mutex_lock();
        if (nt->state == STATE_ENABLED) {
                pr_err("target (%s) is enabled, disable to update parameters\n",
                       config_item_name(&nt->group.cg_item));
                dynamic_netconsole_mutex_unlock();
                return -EINVAL;
        }

        strscpy(nt->np.dev_name, buf, IFNAMSIZ);
        trim_newline(nt->np.dev_name, IFNAMSIZ);

        dynamic_netconsole_mutex_unlock();
        return strnlen(buf, count);
}

static ssize_t local_port_store(struct config_item *item, const char *buf,
                size_t count)
{
        struct netconsole_target *nt = to_target(item);
        ssize_t ret = -EINVAL;

        dynamic_netconsole_mutex_lock();
        if (nt->state == STATE_ENABLED) {
                pr_err("target (%s) is enabled, disable to update parameters\n",
                       config_item_name(&nt->group.cg_item));
                goto out_unlock;
        }

        ret = kstrtou16(buf, 10, &nt->np.local_port);
        if (ret < 0)
                goto out_unlock;
        ret = strnlen(buf, count);
out_unlock:
        dynamic_netconsole_mutex_unlock();
        return ret;
}

static ssize_t remote_port_store(struct config_item *item,
                const char *buf, size_t count)
{
        struct netconsole_target *nt = to_target(item);
        ssize_t ret = -EINVAL;

        dynamic_netconsole_mutex_lock();
        if (nt->state == STATE_ENABLED) {
                pr_err("target (%s) is enabled, disable to update parameters\n",
                       config_item_name(&nt->group.cg_item));
                goto out_unlock;
        }

        ret = kstrtou16(buf, 10, &nt->np.remote_port);
        if (ret < 0)
                goto out_unlock;
        ret = strnlen(buf, count);
out_unlock:
        dynamic_netconsole_mutex_unlock();
        return ret;
}

static ssize_t local_ip_store(struct config_item *item, const char *buf,
                size_t count)
{
        struct netconsole_target *nt = to_target(item);
        ssize_t ret = -EINVAL;
        int ipv6;

        dynamic_netconsole_mutex_lock();
        if (nt->state == STATE_ENABLED) {
                pr_err("target (%s) is enabled, disable to update parameters\n",
                       config_item_name(&nt->group.cg_item));
                goto out_unlock;
        }

        ipv6 = netpoll_parse_ip_addr(buf, &nt->np.local_ip);
        if (ipv6 == -1)
                goto out_unlock;
        nt->np.ipv6 = !!ipv6;

        ret = strnlen(buf, count);
out_unlock:
        dynamic_netconsole_mutex_unlock();
        return ret;
}

static ssize_t remote_ip_store(struct config_item *item, const char *buf,
               size_t count)
{
        struct netconsole_target *nt = to_target(item);
        ssize_t ret = -EINVAL;
        int ipv6;

        dynamic_netconsole_mutex_lock();
        if (nt->state == STATE_ENABLED) {
                pr_err("target (%s) is enabled, disable to update parameters\n",
                       config_item_name(&nt->group.cg_item));
                goto out_unlock;
        }

        ipv6 = netpoll_parse_ip_addr(buf, &nt->np.remote_ip);
        if (ipv6 == -1)
                goto out_unlock;
        nt->np.ipv6 = !!ipv6;

        ret = strnlen(buf, count);
out_unlock:
        dynamic_netconsole_mutex_unlock();
        return ret;
}

/* Count number of entries we have in userdata.
 * This is important because userdata only supports MAX_USERDATA_ITEMS
 * entries. Before enabling any new userdata feature, number of entries needs
 * to checked for available space.
 */
static size_t count_userdata_entries(struct netconsole_target *nt)
{
        return list_count_nodes(&nt->userdata_group.cg_children);
}

static ssize_t remote_mac_store(struct config_item *item, const char *buf,
                size_t count)
{
        struct netconsole_target *nt = to_target(item);
        u8 remote_mac[ETH_ALEN];
        ssize_t ret = -EINVAL;

        dynamic_netconsole_mutex_lock();
        if (nt->state == STATE_ENABLED) {
                pr_err("target (%s) is enabled, disable to update parameters\n",
                       config_item_name(&nt->group.cg_item));
                goto out_unlock;
        }

        if (!mac_pton(buf, remote_mac))
                goto out_unlock;
        if (buf[MAC_ADDR_STR_LEN] && buf[MAC_ADDR_STR_LEN] != '\n')
                goto out_unlock;
        memcpy(nt->np.remote_mac, remote_mac, ETH_ALEN);

        ret = strnlen(buf, count);
out_unlock:
        dynamic_netconsole_mutex_unlock();
        return ret;
}

struct userdatum {
        struct config_item item;
        char value[MAX_EXTRADATA_VALUE_LEN];
};

static struct userdatum *to_userdatum(struct config_item *item)
{
        return container_of(item, struct userdatum, item);
}

struct userdata {
        struct config_group group;
};

static struct userdata *to_userdata(struct config_item *item)
{
        return container_of(to_config_group(item), struct userdata, group);
}

static struct netconsole_target *userdata_to_target(struct userdata *ud)
{
        struct config_group *netconsole_group;

        netconsole_group = to_config_group(ud->group.cg_item.ci_parent);
        return to_target(&netconsole_group->cg_item);
}

static ssize_t userdatum_value_show(struct config_item *item, char *buf)
{
        return sysfs_emit(buf, "%s\n", &(to_userdatum(item)->value[0]));
}

/* Navigate configfs and calculate the lentgh of the formatted string
 * representing userdata.
 * Must be called holding netconsole_subsys.su_mutex
 */
static int calc_userdata_len(struct netconsole_target *nt)
{
        struct userdatum *udm_item;
        struct config_item *item;
        struct list_head *entry;
        int len = 0;

        list_for_each(entry, &nt->userdata_group.cg_children) {
                item = container_of(entry, struct config_item, ci_entry);
                udm_item = to_userdatum(item);
                /* Skip userdata with no value set */
                if (udm_item->value[0]) {
                        len += snprintf(NULL, 0, " %s=%s\n", item->ci_name,
                                        udm_item->value);
                }
        }
        return len;
}

static int update_userdata(struct netconsole_target *nt)
{
        struct userdatum *udm_item;
        struct config_item *item;
        struct list_head *entry;
        char *old_buf = NULL;
        char *new_buf = NULL;
        unsigned long flags;
        int offset = 0;
        int len;

        /* Calculate required buffer size */
        len = calc_userdata_len(nt);

        if (WARN_ON_ONCE(len > MAX_EXTRADATA_ENTRY_LEN * MAX_USERDATA_ITEMS))
                return -ENOSPC;

        /* Allocate new buffer */
        if (len) {
                new_buf = kmalloc(len + 1, GFP_KERNEL);
                if (!new_buf)
                        return -ENOMEM;
        }

        /* Write userdata to new buffer */
        list_for_each(entry, &nt->userdata_group.cg_children) {
                item = container_of(entry, struct config_item, ci_entry);
                udm_item = to_userdatum(item);
                /* Skip userdata with no value set */
                if (udm_item->value[0]) {
                        offset += scnprintf(&new_buf[offset], len + 1 - offset,
                                            " %s=%s\n", item->ci_name,
                                            udm_item->value);
                }
        }

        WARN_ON_ONCE(offset != len);

        /* Switch to new buffer and free old buffer */
        spin_lock_irqsave(&target_list_lock, flags);
        old_buf = nt->userdata;
        nt->userdata = new_buf;
        nt->userdata_length = offset;
        spin_unlock_irqrestore(&target_list_lock, flags);

        kfree(old_buf);

        return 0;
}

static ssize_t userdatum_value_store(struct config_item *item, const char *buf,
                                     size_t count)
{
        struct userdatum *udm = to_userdatum(item);
        struct netconsole_target *nt;
        struct userdata *ud;
        ssize_t ret;

        if (count > MAX_EXTRADATA_VALUE_LEN)
                return -EMSGSIZE;

        mutex_lock(&netconsole_subsys.su_mutex);
        dynamic_netconsole_mutex_lock();

        ret = strscpy(udm->value, buf, sizeof(udm->value));
        if (ret < 0)
                goto out_unlock;
        trim_newline(udm->value, sizeof(udm->value));

        ud = to_userdata(item->ci_parent);
        nt = userdata_to_target(ud);
        ret = update_userdata(nt);
        if (ret < 0)
                goto out_unlock;
        ret = count;
out_unlock:
        dynamic_netconsole_mutex_unlock();
        mutex_unlock(&netconsole_subsys.su_mutex);
        return ret;
}

/* disable_sysdata_feature - Disable sysdata feature and clean sysdata
 * @nt: target that is disabling the feature
 * @feature: feature being disabled
 */
static void disable_sysdata_feature(struct netconsole_target *nt,
                                    enum sysdata_feature feature)
{
        nt->sysdata_fields &= ~feature;
        nt->sysdata[0] = 0;
}

static ssize_t sysdata_msgid_enabled_store(struct config_item *item,
                                           const char *buf, size_t count)
{
        struct netconsole_target *nt = to_target(item->ci_parent);
        bool msgid_enabled, curr;
        ssize_t ret;

        ret = kstrtobool(buf, &msgid_enabled);
        if (ret)
                return ret;

        mutex_lock(&netconsole_subsys.su_mutex);
        dynamic_netconsole_mutex_lock();
        curr = !!(nt->sysdata_fields & SYSDATA_MSGID);
        if (msgid_enabled == curr)
                goto unlock_ok;

        if (msgid_enabled)
                nt->sysdata_fields |= SYSDATA_MSGID;
        else
                disable_sysdata_feature(nt, SYSDATA_MSGID);

unlock_ok:
        ret = strnlen(buf, count);
        dynamic_netconsole_mutex_unlock();
        mutex_unlock(&netconsole_subsys.su_mutex);
        return ret;
}

static ssize_t sysdata_release_enabled_store(struct config_item *item,
                                             const char *buf, size_t count)
{
        struct netconsole_target *nt = to_target(item->ci_parent);
        bool release_enabled, curr;
        ssize_t ret;

        ret = kstrtobool(buf, &release_enabled);
        if (ret)
                return ret;

        mutex_lock(&netconsole_subsys.su_mutex);
        dynamic_netconsole_mutex_lock();
        curr = !!(nt->sysdata_fields & SYSDATA_RELEASE);
        if (release_enabled == curr)
                goto unlock_ok;

        if (release_enabled)
                nt->sysdata_fields |= SYSDATA_RELEASE;
        else
                disable_sysdata_feature(nt, SYSDATA_RELEASE);

unlock_ok:
        ret = strnlen(buf, count);
        dynamic_netconsole_mutex_unlock();
        mutex_unlock(&netconsole_subsys.su_mutex);
        return ret;
}

static ssize_t sysdata_taskname_enabled_store(struct config_item *item,
                                              const char *buf, size_t count)
{
        struct netconsole_target *nt = to_target(item->ci_parent);
        bool taskname_enabled, curr;
        ssize_t ret;

        ret = kstrtobool(buf, &taskname_enabled);
        if (ret)
                return ret;

        mutex_lock(&netconsole_subsys.su_mutex);
        dynamic_netconsole_mutex_lock();
        curr = !!(nt->sysdata_fields & SYSDATA_TASKNAME);
        if (taskname_enabled == curr)
                goto unlock_ok;

        if (taskname_enabled)
                nt->sysdata_fields |= SYSDATA_TASKNAME;
        else
                disable_sysdata_feature(nt, SYSDATA_TASKNAME);

unlock_ok:
        ret = strnlen(buf, count);
        dynamic_netconsole_mutex_unlock();
        mutex_unlock(&netconsole_subsys.su_mutex);
        return ret;
}

/* configfs helper to sysdata cpu_nr feature */
static ssize_t sysdata_cpu_nr_enabled_store(struct config_item *item,
                                            const char *buf, size_t count)
{
        struct netconsole_target *nt = to_target(item->ci_parent);
        bool cpu_nr_enabled, curr;
        ssize_t ret;

        ret = kstrtobool(buf, &cpu_nr_enabled);
        if (ret)
                return ret;

        mutex_lock(&netconsole_subsys.su_mutex);
        dynamic_netconsole_mutex_lock();
        curr = !!(nt->sysdata_fields & SYSDATA_CPU_NR);
        if (cpu_nr_enabled == curr)
                /* no change requested */
                goto unlock_ok;

        if (cpu_nr_enabled)
                nt->sysdata_fields |= SYSDATA_CPU_NR;
        else
                /* This is special because sysdata might have remaining data
                 * from previous sysdata, and it needs to be cleaned.
                 */
                disable_sysdata_feature(nt, SYSDATA_CPU_NR);

unlock_ok:
        ret = strnlen(buf, count);
        dynamic_netconsole_mutex_unlock();
        mutex_unlock(&netconsole_subsys.su_mutex);
        return ret;
}

CONFIGFS_ATTR(userdatum_, value);
CONFIGFS_ATTR(sysdata_, cpu_nr_enabled);
CONFIGFS_ATTR(sysdata_, taskname_enabled);
CONFIGFS_ATTR(sysdata_, release_enabled);
CONFIGFS_ATTR(sysdata_, msgid_enabled);

static struct configfs_attribute *userdatum_attrs[] = {
        &userdatum_attr_value,
        NULL,
};

static void userdatum_release(struct config_item *item)
{
        kfree(to_userdatum(item));
}

static struct configfs_item_operations userdatum_ops = {
        .release = userdatum_release,
};

static const struct config_item_type userdatum_type = {
        .ct_item_ops    = &userdatum_ops,
        .ct_attrs       = userdatum_attrs,
        .ct_owner       = THIS_MODULE,
};

static struct config_item *userdatum_make_item(struct config_group *group,
                                               const char *name)
{
        struct netconsole_target *nt;
        struct userdatum *udm;
        struct userdata *ud;

        if (strlen(name) > MAX_EXTRADATA_NAME_LEN)
                return ERR_PTR(-ENAMETOOLONG);

        ud = to_userdata(&group->cg_item);
        nt = userdata_to_target(ud);
        if (count_userdata_entries(nt) >= MAX_USERDATA_ITEMS)
                return ERR_PTR(-ENOSPC);

        udm = kzalloc_obj(*udm);
        if (!udm)
                return ERR_PTR(-ENOMEM);

        config_item_init_type_name(&udm->item, name, &userdatum_type);
        return &udm->item;
}

static void userdatum_drop(struct config_group *group, struct config_item *item)
{
        struct netconsole_target *nt;
        struct userdata *ud;

        ud = to_userdata(&group->cg_item);
        nt = userdata_to_target(ud);

        dynamic_netconsole_mutex_lock();
        update_userdata(nt);
        config_item_put(item);
        dynamic_netconsole_mutex_unlock();
}

static struct configfs_attribute *userdata_attrs[] = {
        &sysdata_attr_cpu_nr_enabled,
        &sysdata_attr_taskname_enabled,
        &sysdata_attr_release_enabled,
        &sysdata_attr_msgid_enabled,
        NULL,
};

static struct configfs_group_operations userdata_ops = {
        .make_item              = userdatum_make_item,
        .drop_item              = userdatum_drop,
};

static const struct config_item_type userdata_type = {
        .ct_item_ops    = &userdatum_ops,
        .ct_group_ops   = &userdata_ops,
        .ct_attrs       = userdata_attrs,
        .ct_owner       = THIS_MODULE,
};

CONFIGFS_ATTR(, enabled);
CONFIGFS_ATTR(, extended);
CONFIGFS_ATTR(, dev_name);
CONFIGFS_ATTR(, local_port);
CONFIGFS_ATTR(, remote_port);
CONFIGFS_ATTR(, local_ip);
CONFIGFS_ATTR(, remote_ip);
CONFIGFS_ATTR_RO(, local_mac);
CONFIGFS_ATTR(, remote_mac);
CONFIGFS_ATTR(, release);
CONFIGFS_ATTR_RO(, transmit_errors);

static struct configfs_attribute *netconsole_target_attrs[] = {
        &attr_enabled,
        &attr_extended,
        &attr_release,
        &attr_dev_name,
        &attr_local_port,
        &attr_remote_port,
        &attr_local_ip,
        &attr_remote_ip,
        &attr_local_mac,
        &attr_remote_mac,
        &attr_transmit_errors,
        NULL,
};

/*
 * Item operations and type for netconsole_target.
 */

static void netconsole_target_release(struct config_item *item)
{
        struct netconsole_target *nt = to_target(item);

        kfree(nt->userdata);
        kfree(nt);
}

static struct configfs_item_operations netconsole_target_item_ops = {
        .release                = netconsole_target_release,
};

static const struct config_item_type netconsole_target_type = {
        .ct_attrs               = netconsole_target_attrs,
        .ct_item_ops            = &netconsole_target_item_ops,
        .ct_owner               = THIS_MODULE,
};

static void init_target_config_group(struct netconsole_target *nt,
                                     const char *name)
{
        config_group_init_type_name(&nt->group, name, &netconsole_target_type);
        config_group_init_type_name(&nt->userdata_group, "userdata",
                                    &userdata_type);
        configfs_add_default_group(&nt->userdata_group, &nt->group);
}

static struct netconsole_target *find_cmdline_target(const char *name)
{
        struct netconsole_target *nt, *ret = NULL;
        unsigned long flags;

        spin_lock_irqsave(&target_list_lock, flags);
        list_for_each_entry(nt, &target_list, list) {
                if (!strcmp(nt->group.cg_item.ci_name, name)) {
                        ret = nt;
                        break;
                }
        }
        spin_unlock_irqrestore(&target_list_lock, flags);

        return ret;
}

/*
 * Group operations and type for netconsole_subsys.
 */

static struct config_group *make_netconsole_target(struct config_group *group,
                                                   const char *name)
{
        struct netconsole_target *nt;
        unsigned long flags;

        /* Checking if a target by this name was created at boot time.  If so,
         * attach a configfs entry to that target.  This enables dynamic
         * control.
         */
        if (!strncmp(name, NETCONSOLE_PARAM_TARGET_PREFIX,
                     strlen(NETCONSOLE_PARAM_TARGET_PREFIX))) {
                nt = find_cmdline_target(name);
                if (nt) {
                        init_target_config_group(nt, name);
                        return &nt->group;
                }
        }

        nt = alloc_and_init();
        if (!nt)
                return ERR_PTR(-ENOMEM);

        /* Initialize the config_group member */
        init_target_config_group(nt, name);

        /* Adding, but it is disabled */
        spin_lock_irqsave(&target_list_lock, flags);
        list_add(&nt->list, &target_list);
        spin_unlock_irqrestore(&target_list_lock, flags);

        return &nt->group;
}

static void drop_netconsole_target(struct config_group *group,
                                   struct config_item *item)
{
        struct netconsole_target *nt = to_target(item);
        unsigned long flags;

        dynamic_netconsole_mutex_lock();

        spin_lock_irqsave(&target_list_lock, flags);
        /* Disable deactivated target to prevent races between resume attempt
         * and target removal.
         */
        if (nt->state == STATE_DEACTIVATED)
                nt->state = STATE_DISABLED;
        list_del(&nt->list);
        spin_unlock_irqrestore(&target_list_lock, flags);

        dynamic_netconsole_mutex_unlock();

        /* Now that the target has been marked disabled no further work
         * can be scheduled. Existing work will skip as targets are not
         * deactivated anymore. Cancel any scheduled resume and wait for
         * completion.
         */
        cancel_work_sync(&nt->resume_wq);

        /*
         * The target may have never been enabled, or was manually disabled
         * before being removed so netpoll may have already been cleaned up.
         */
        if (nt->state == STATE_ENABLED)
                netpoll_cleanup(&nt->np);

        config_item_put(&nt->group.cg_item);
}

static struct configfs_group_operations netconsole_subsys_group_ops = {
        .make_group     = make_netconsole_target,
        .drop_item      = drop_netconsole_target,
};

static const struct config_item_type netconsole_subsys_type = {
        .ct_group_ops   = &netconsole_subsys_group_ops,
        .ct_owner       = THIS_MODULE,
};

/* The netconsole configfs subsystem */
static struct configfs_subsystem netconsole_subsys = {
        .su_group       = {
                .cg_item        = {
                        .ci_namebuf     = "netconsole",
                        .ci_type        = &netconsole_subsys_type,
                },
        },
};

static void populate_configfs_item(struct netconsole_target *nt,
                                   int cmdline_count)
{
        char target_name[16];

        snprintf(target_name, sizeof(target_name), "%s%d",
                 NETCONSOLE_PARAM_TARGET_PREFIX, cmdline_count);
        init_target_config_group(nt, target_name);
}

static int sysdata_append_cpu_nr(struct netconsole_target *nt, int offset,
                                 struct nbcon_write_context *wctxt)
{
        return scnprintf(&nt->sysdata[offset],
                         MAX_EXTRADATA_ENTRY_LEN, " cpu=%u\n",
                         wctxt->cpu);
}

static int sysdata_append_taskname(struct netconsole_target *nt, int offset,
                                   struct nbcon_write_context *wctxt)
{
        return scnprintf(&nt->sysdata[offset],
                         MAX_EXTRADATA_ENTRY_LEN, " taskname=%s\n",
                         wctxt->comm);
}

static int sysdata_append_release(struct netconsole_target *nt, int offset)
{
        return scnprintf(&nt->sysdata[offset],
                         MAX_EXTRADATA_ENTRY_LEN, " release=%s\n",
                         init_utsname()->release);
}

static int sysdata_append_msgid(struct netconsole_target *nt, int offset)
{
        wrapping_assign_add(nt->msgcounter, 1);
        return scnprintf(&nt->sysdata[offset],
                         MAX_EXTRADATA_ENTRY_LEN, " msgid=%u\n",
                         nt->msgcounter);
}

/*
 * prepare_sysdata - append sysdata in runtime
 * @nt: target to send message to
 * @wctxt: nbcon write context containing message metadata
 */
static int prepare_sysdata(struct netconsole_target *nt,
                           struct nbcon_write_context *wctxt)
{
        int sysdata_len = 0;

        if (!nt->sysdata_fields)
                goto out;

        if (nt->sysdata_fields & SYSDATA_CPU_NR)
                sysdata_len += sysdata_append_cpu_nr(nt, sysdata_len, wctxt);
        if (nt->sysdata_fields & SYSDATA_TASKNAME)
                sysdata_len += sysdata_append_taskname(nt, sysdata_len, wctxt);
        if (nt->sysdata_fields & SYSDATA_RELEASE)
                sysdata_len += sysdata_append_release(nt, sysdata_len);
        if (nt->sysdata_fields & SYSDATA_MSGID)
                sysdata_len += sysdata_append_msgid(nt, sysdata_len);

        WARN_ON_ONCE(sysdata_len >
                     MAX_EXTRADATA_ENTRY_LEN * MAX_SYSDATA_ITEMS);

out:
        return sysdata_len;
}
#endif  /* CONFIG_NETCONSOLE_DYNAMIC */

/* Handle network interface device notifications */
static int netconsole_netdev_event(struct notifier_block *this,
                                   unsigned long event, void *ptr)
{
        struct net_device *dev = netdev_notifier_info_to_dev(ptr);
        struct netconsole_target *nt, *tmp;
        bool stopped = false;
        unsigned long flags;

        if (!(event == NETDEV_CHANGENAME || event == NETDEV_UNREGISTER ||
              event == NETDEV_RELEASE || event == NETDEV_JOIN ||
              event == NETDEV_REGISTER))
                goto done;

        mutex_lock(&target_cleanup_list_lock);
        spin_lock_irqsave(&target_list_lock, flags);
        list_for_each_entry_safe(nt, tmp, &target_list, list) {
                netconsole_target_get(nt);
                if (nt->np.dev == dev) {
                        switch (event) {
                        case NETDEV_CHANGENAME:
                                strscpy(nt->np.dev_name, dev->name, IFNAMSIZ);
                                break;
                        case NETDEV_RELEASE:
                        case NETDEV_JOIN:
                                /* transition target to DISABLED instead of
                                 * DEACTIVATED when (de)enslaving devices as
                                 * their targets should not be automatically
                                 * resumed when the interface is brought up.
                                 */
                                nt->state = STATE_DISABLED;
                                list_move(&nt->list, &target_cleanup_list);
                                stopped = true;
                                break;
                        case NETDEV_UNREGISTER:
                                nt->state = STATE_DEACTIVATED;
                                list_move(&nt->list, &target_cleanup_list);
                                stopped = true;
                        }
                }
                if ((event == NETDEV_REGISTER || event == NETDEV_CHANGENAME) &&
                    deactivated_target_match(nt, dev))
                        /* Schedule resume on a workqueue as it will attempt
                         * to UP the device, which can't be done as part of this
                         * notifier.
                         */
                        queue_work(netconsole_wq, &nt->resume_wq);
                netconsole_target_put(nt);
        }
        spin_unlock_irqrestore(&target_list_lock, flags);
        mutex_unlock(&target_cleanup_list_lock);

        if (stopped) {
                const char *msg = "had an event";

                switch (event) {
                case NETDEV_UNREGISTER:
                        msg = "unregistered";
                        break;
                case NETDEV_RELEASE:
                        msg = "released slaves";
                        break;
                case NETDEV_JOIN:
                        msg = "is joining a master device";
                        break;
                }
                pr_info("network logging stopped on interface %s as it %s\n",
                        dev->name, msg);
        }

        /* Process target_cleanup_list entries. By the end, target_cleanup_list
         * should be empty
         */
        netconsole_process_cleanups_core();

done:
        return NOTIFY_DONE;
}

static struct notifier_block netconsole_netdev_notifier = {
        .notifier_call  = netconsole_netdev_event,
};

/**
 * send_udp - Wrapper for netpoll_send_udp that counts errors
 * @nt: target to send message to
 * @msg: message to send
 * @len: length of message
 *
 * Calls netpoll_send_udp and classifies the return value. If an error
 * occurred it increments statistics in nt->stats accordingly.
 * Only calls netpoll_send_udp if CONFIG_NETCONSOLE_DYNAMIC is disabled.
 */
static void send_udp(struct netconsole_target *nt, const char *msg, int len)
{
        int result = netpoll_send_udp(&nt->np, msg, len);

        if (IS_ENABLED(CONFIG_NETCONSOLE_DYNAMIC)) {
                if (result == NET_XMIT_DROP) {
                        u64_stats_update_begin(&nt->stats.syncp);
                        u64_stats_inc(&nt->stats.xmit_drop_count);
                        u64_stats_update_end(&nt->stats.syncp);
                } else if (result == -ENOMEM) {
                        u64_stats_update_begin(&nt->stats.syncp);
                        u64_stats_inc(&nt->stats.enomem_count);
                        u64_stats_update_end(&nt->stats.syncp);
                }
        }
}

static void send_msg_no_fragmentation(struct netconsole_target *nt,
                                      const char *msg,
                                      int msg_len,
                                      int release_len)
{
        const char *userdata = NULL;
        const char *sysdata = NULL;
        const char *release;

#ifdef CONFIG_NETCONSOLE_DYNAMIC
        userdata = nt->userdata;
        sysdata = nt->sysdata;
#endif

        if (release_len) {
                release = init_utsname()->release;

                scnprintf(nt->buf, MAX_PRINT_CHUNK, "%s,%.*s", release,
                          msg_len, msg);
                msg_len += release_len;
        } else {
                memcpy(nt->buf, msg, msg_len);
        }

        if (userdata)
                msg_len += scnprintf(&nt->buf[msg_len],
                                     MAX_PRINT_CHUNK - msg_len, "%s",
                                     userdata);

        if (sysdata)
                msg_len += scnprintf(&nt->buf[msg_len],
                                     MAX_PRINT_CHUNK - msg_len, "%s",
                                     sysdata);

        send_udp(nt, nt->buf, msg_len);
}

static void append_release(char *buf)
{
        const char *release;

        release = init_utsname()->release;
        scnprintf(buf, MAX_PRINT_CHUNK, "%s,", release);
}

static void send_fragmented_body(struct netconsole_target *nt,
                                 const char *msgbody_ptr, int header_len,
                                 int msgbody_len, int sysdata_len)
{
        const char *userdata_ptr = NULL;
        const char *sysdata_ptr = NULL;
        int data_len, data_sent = 0;
        int userdata_offset = 0;
        int sysdata_offset = 0;
        int msgbody_offset = 0;
        int userdata_len = 0;

#ifdef CONFIG_NETCONSOLE_DYNAMIC
        userdata_ptr = nt->userdata;
        sysdata_ptr = nt->sysdata;
        userdata_len = nt->userdata_length;
#endif
        if (WARN_ON_ONCE(!userdata_ptr && userdata_len != 0))
                return;

        if (WARN_ON_ONCE(!sysdata_ptr && sysdata_len != 0))
                return;

        /* data_len represents the number of bytes that will be sent. This is
         * bigger than MAX_PRINT_CHUNK, thus, it will be split in multiple
         * packets
         */
        data_len = msgbody_len + userdata_len + sysdata_len;

        /* In each iteration of the while loop below, we send a packet
         * containing the header and a portion of the data. The data is
         * composed of three parts: msgbody, userdata, and sysdata.
         * We keep track of how many bytes have been sent from each part using
         * the *_offset variables.
         * We keep track of how many bytes have been sent overall using the
         * data_sent variable, which ranges from 0 to the total bytes to be
         * sent.
         */
        while (data_sent < data_len) {
                int userdata_left = userdata_len - userdata_offset;
                int sysdata_left = sysdata_len - sysdata_offset;
                int msgbody_left = msgbody_len - msgbody_offset;
                int buf_offset = 0;
                int this_chunk = 0;

                /* header is already populated in nt->buf, just append to it */
                buf_offset = header_len;

                buf_offset += scnprintf(nt->buf + buf_offset,
                                         MAX_PRINT_CHUNK - buf_offset,
                                         ",ncfrag=%d/%d;", data_sent,
                                         data_len);

                /* append msgbody first */
                this_chunk = min(msgbody_left, MAX_PRINT_CHUNK - buf_offset);
                memcpy(nt->buf + buf_offset, msgbody_ptr + msgbody_offset,
                       this_chunk);
                msgbody_offset += this_chunk;
                buf_offset += this_chunk;
                data_sent += this_chunk;

                /* after msgbody, append userdata */
                if (userdata_ptr && userdata_left) {
                        this_chunk = min(userdata_left,
                                         MAX_PRINT_CHUNK - buf_offset);
                        memcpy(nt->buf + buf_offset,
                               userdata_ptr + userdata_offset, this_chunk);
                        userdata_offset += this_chunk;
                        buf_offset += this_chunk;
                        data_sent += this_chunk;
                }

                /* after userdata, append sysdata */
                if (sysdata_ptr && sysdata_left) {
                        this_chunk = min(sysdata_left,
                                         MAX_PRINT_CHUNK - buf_offset);
                        memcpy(nt->buf + buf_offset,
                               sysdata_ptr + sysdata_offset, this_chunk);
                        sysdata_offset += this_chunk;
                        buf_offset += this_chunk;
                        data_sent += this_chunk;
                }

                /* if all is good, send the packet out */
                if (WARN_ON_ONCE(data_sent > data_len))
                        return;

                send_udp(nt, nt->buf, buf_offset);
        }
}

static void send_msg_fragmented(struct netconsole_target *nt,
                                const char *msg,
                                int msg_len,
                                int release_len,
                                int sysdata_len)
{
        int header_len, msgbody_len;
        const char *msgbody;

        /* need to insert extra header fields, detect header and msgbody */
        msgbody = memchr(msg, ';', msg_len);
        if (WARN_ON_ONCE(!msgbody))
                return;

        header_len = msgbody - msg;
        msgbody_len = msg_len - header_len - 1;
        msgbody++;

        /*
         * Transfer multiple chunks with the following extra header.
         * "ncfrag=<byte-offset>/<total-bytes>"
         */
        if (release_len)
                append_release(nt->buf);

        /* Copy the header into the buffer */
        memcpy(nt->buf + release_len, msg, header_len);
        header_len += release_len;

        /* for now on, the header will be persisted, and the msgbody
         * will be replaced
         */
        send_fragmented_body(nt, msgbody, header_len, msgbody_len,
                             sysdata_len);
}

/**
 * send_ext_msg_udp - send extended log message to target
 * @nt: target to send message to
 * @wctxt: nbcon write context containing message and metadata
 *
 * Transfer extended log message to @nt.  If message is longer than
 * MAX_PRINT_CHUNK, it'll be split and transmitted in multiple chunks with
 * ncfrag header field added to identify them.
 */
static void send_ext_msg_udp(struct netconsole_target *nt,
                             struct nbcon_write_context *wctxt)
{
        int userdata_len = 0;
        int release_len = 0;
        int sysdata_len = 0;
        int len;

#ifdef CONFIG_NETCONSOLE_DYNAMIC
        sysdata_len = prepare_sysdata(nt, wctxt);
        userdata_len = nt->userdata_length;
#endif
        if (nt->release)
                release_len = strlen(init_utsname()->release) + 1;

        len = wctxt->len + release_len + sysdata_len + userdata_len;
        if (len <= MAX_PRINT_CHUNK)
                return send_msg_no_fragmentation(nt, wctxt->outbuf,
                                                 wctxt->len, release_len);

        return send_msg_fragmented(nt, wctxt->outbuf, wctxt->len, release_len,
                                   sysdata_len);
}

static void send_msg_udp(struct netconsole_target *nt, const char *msg,
                         unsigned int len)
{
        const char *tmp = msg;
        int frag, left = len;

        while (left > 0) {
                frag = min(left, MAX_PRINT_CHUNK);
                send_udp(nt, tmp, frag);
                tmp += frag;
                left -= frag;
        }
}

/**
 * netconsole_write - Generic function to send a msg to all targets
 * @wctxt: nbcon write context
 * @extended: "true" for extended console mode
 *
 * Given an nbcon write context, send the message to the netconsole targets
 */
static void netconsole_write(struct nbcon_write_context *wctxt, bool extended)
{
        struct netconsole_target *nt;

        if (oops_only && !oops_in_progress)
                return;

        list_for_each_entry(nt, &target_list, list) {
                if (nt->extended != extended || nt->state != STATE_ENABLED ||
                    !netif_running(nt->np.dev))
                        continue;

                /* If nbcon_enter_unsafe() fails, just return given netconsole
                 * lost the ownership, and iterating over the targets will not
                 * be able to re-acquire.
                 */
                if (!nbcon_enter_unsafe(wctxt))
                        return;

                if (extended)
                        send_ext_msg_udp(nt, wctxt);
                else
                        send_msg_udp(nt, wctxt->outbuf, wctxt->len);

                nbcon_exit_unsafe(wctxt);
        }
}

static void netconsole_write_ext(struct console *con __always_unused,
                                 struct nbcon_write_context *wctxt)
{
        netconsole_write(wctxt, true);
}

static void netconsole_write_basic(struct console *con __always_unused,
                                   struct nbcon_write_context *wctxt)
{
        netconsole_write(wctxt, false);
}

static void netconsole_device_lock(struct console *con __always_unused,
                                   unsigned long *flags)
__acquires(&target_list_lock)
{
        spin_lock_irqsave(&target_list_lock, *flags);
}

static void netconsole_device_unlock(struct console *con __always_unused,
                                     unsigned long flags)
__releases(&target_list_lock)
{
        spin_unlock_irqrestore(&target_list_lock, flags);
}

static int netconsole_parser_cmdline(struct netpoll *np, char *opt)
{
        bool ipversion_set = false;
        char *cur = opt;
        char *delim;
        int ipv6;

        if (*cur != '@') {
                delim = strchr(cur, '@');
                if (!delim)
                        goto parse_failed;
                *delim = 0;
                if (kstrtou16(cur, 10, &np->local_port))
                        goto parse_failed;
                cur = delim;
        }
        cur++;

        if (*cur != '/') {
                ipversion_set = true;
                delim = strchr(cur, '/');
                if (!delim)
                        goto parse_failed;
                *delim = 0;
                ipv6 = netpoll_parse_ip_addr(cur, &np->local_ip);
                if (ipv6 < 0)
                        goto parse_failed;
                else
                        np->ipv6 = (bool)ipv6;
                cur = delim;
        }
        cur++;

        if (*cur != ',') {
                /* parse out dev_name or dev_mac */
                delim = strchr(cur, ',');
                if (!delim)
                        goto parse_failed;
                *delim = 0;

                np->dev_name[0] = '\0';
                eth_broadcast_addr(np->dev_mac);
                if (!strchr(cur, ':'))
                        strscpy(np->dev_name, cur, sizeof(np->dev_name));
                else if (!mac_pton(cur, np->dev_mac))
                        goto parse_failed;

                cur = delim;
        }
        cur++;

        if (*cur != '@') {
                /* dst port */
                delim = strchr(cur, '@');
                if (!delim)
                        goto parse_failed;
                *delim = 0;
                if (*cur == ' ' || *cur == '\t')
                        np_info(np, "warning: whitespace is not allowed\n");
                if (kstrtou16(cur, 10, &np->remote_port))
                        goto parse_failed;
                cur = delim;
        }
        cur++;

        /* dst ip */
        delim = strchr(cur, '/');
        if (!delim)
                goto parse_failed;
        *delim = 0;
        ipv6 = netpoll_parse_ip_addr(cur, &np->remote_ip);
        if (ipv6 < 0)
                goto parse_failed;
        else if (ipversion_set && np->ipv6 != (bool)ipv6)
                goto parse_failed;
        else
                np->ipv6 = (bool)ipv6;
        cur = delim + 1;

        if (*cur != 0) {
                /* MAC address */
                if (!mac_pton(cur, np->remote_mac))
                        goto parse_failed;
        }

        netconsole_print_banner(np);

        return 0;

 parse_failed:
        np_info(np, "couldn't parse config at '%s'!\n", cur);
        return -1;
}

/* Allocate new target (from boot/module param) and setup netpoll for it */
static struct netconsole_target *alloc_param_target(char *target_config,
                                                    int cmdline_count)
{
        struct netconsole_target *nt;
        int err;

        nt = alloc_and_init();
        if (!nt) {
                err = -ENOMEM;
                goto fail;
        }

        if (*target_config == '+') {
                nt->extended = true;
                target_config++;
        }

        if (*target_config == 'r') {
                if (!nt->extended) {
                        pr_err("Netconsole configuration error. Release feature requires extended log message");
                        err = -EINVAL;
                        goto fail;
                }
                nt->release = true;
                target_config++;
        }

        /* Parse parameters and setup netpoll */
        err = netconsole_parser_cmdline(&nt->np, target_config);
        if (err)
                goto fail;

        err = netpoll_setup(&nt->np);
        if (err) {
                pr_err("Not enabling netconsole for %s%d. Netpoll setup failed\n",
                       NETCONSOLE_PARAM_TARGET_PREFIX, cmdline_count);
                if (!IS_ENABLED(CONFIG_NETCONSOLE_DYNAMIC))
                        /* only fail if dynamic reconfiguration is set,
                         * otherwise, keep the target in the list, but disabled.
                         */
                        goto fail;
        } else {
                nt->state = STATE_ENABLED;
        }
        populate_configfs_item(nt, cmdline_count);

        return nt;

fail:
        kfree(nt);
        return ERR_PTR(err);
}

/* Cleanup netpoll for given target (from boot/module param) and free it */
static void free_param_target(struct netconsole_target *nt)
{
        cancel_work_sync(&nt->resume_wq);
        netpoll_cleanup(&nt->np);
#ifdef  CONFIG_NETCONSOLE_DYNAMIC
        kfree(nt->userdata);
#endif
        kfree(nt);
}

static struct console netconsole_ext = {
        .name = "netcon_ext",
        .flags = CON_ENABLED | CON_EXTENDED | CON_NBCON | CON_NBCON_ATOMIC_UNSAFE,
        .write_thread = netconsole_write_ext,
        .write_atomic = netconsole_write_ext,
        .device_lock = netconsole_device_lock,
        .device_unlock = netconsole_device_unlock,
};

static struct console netconsole = {
        .name = "netcon",
        .flags = CON_ENABLED | CON_NBCON | CON_NBCON_ATOMIC_UNSAFE,
        .write_thread = netconsole_write_basic,
        .write_atomic = netconsole_write_basic,
        .device_lock = netconsole_device_lock,
        .device_unlock = netconsole_device_unlock,
};

static int __init init_netconsole(void)
{
        int err;
        struct netconsole_target *nt, *tmp;
        u32 console_type_needed = 0;
        unsigned int count = 0;
        unsigned long flags;
        char *target_config;
        char *input = config;

        if (strnlen(input, MAX_PARAM_LENGTH)) {
                while ((target_config = strsep(&input, ";"))) {
                        nt = alloc_param_target(target_config, count);
                        if (IS_ERR(nt)) {
                                if (IS_ENABLED(CONFIG_NETCONSOLE_DYNAMIC))
                                        continue;
                                err = PTR_ERR(nt);
                                goto fail;
                        }
                        /* Dump existing printks when we register */
                        if (nt->extended) {
                                console_type_needed |= CONS_EXTENDED;
                                netconsole_ext.flags |= CON_PRINTBUFFER;
                        } else {
                                console_type_needed |= CONS_BASIC;
                                netconsole.flags |= CON_PRINTBUFFER;
                        }

                        spin_lock_irqsave(&target_list_lock, flags);
                        list_add(&nt->list, &target_list);
                        spin_unlock_irqrestore(&target_list_lock, flags);
                        count++;
                }
        }

        netconsole_wq = alloc_workqueue("netconsole", WQ_UNBOUND, 0);
        if (!netconsole_wq) {
                err = -ENOMEM;
                goto fail;
        }

        err = register_netdevice_notifier(&netconsole_netdev_notifier);
        if (err)
                goto fail;

        err = dynamic_netconsole_init();
        if (err)
                goto undonotifier;

        if (console_type_needed & CONS_EXTENDED)
                register_console(&netconsole_ext);
        if (console_type_needed & CONS_BASIC)
                register_console(&netconsole);
        pr_info("network logging started\n");

        return err;

undonotifier:
        unregister_netdevice_notifier(&netconsole_netdev_notifier);

fail:
        pr_err("cleaning up\n");

        if (netconsole_wq)
                flush_workqueue(netconsole_wq);
        /*
         * Remove all targets and destroy them (only targets created
         * from the boot/module option exist here). Skipping the list
         * lock is safe here, and netpoll_cleanup() will sleep.
         */
        list_for_each_entry_safe(nt, tmp, &target_list, list) {
                list_del(&nt->list);
                free_param_target(nt);
        }

        if (netconsole_wq)
                destroy_workqueue(netconsole_wq);

        return err;
}

static void __exit cleanup_netconsole(void)
{
        struct netconsole_target *nt, *tmp;

        if (console_is_registered(&netconsole_ext))
                unregister_console(&netconsole_ext);
        if (console_is_registered(&netconsole))
                unregister_console(&netconsole);
        dynamic_netconsole_exit();
        unregister_netdevice_notifier(&netconsole_netdev_notifier);
        flush_workqueue(netconsole_wq);

        /*
         * Targets created via configfs pin references on our module
         * and would first be rmdir(2)'ed from userspace. We reach
         * here only when they are already destroyed, and only those
         * created from the boot/module option are left, so remove and
         * destroy them. Skipping the list lock is safe here, and
         * netpoll_cleanup() will sleep.
         */
        list_for_each_entry_safe(nt, tmp, &target_list, list) {
                list_del(&nt->list);
                free_param_target(nt);
        }

        destroy_workqueue(netconsole_wq);
}

/*
 * Use late_initcall to ensure netconsole is
 * initialized after network device driver if built-in.
 *
 * late_initcall() and module_init() are identical if built as module.
 */
late_initcall(init_netconsole);
module_exit(cleanup_netconsole);