Linux 4.16.11

[linux/fpc-iii.git] / drivers / net / netconsole.c

/*
 *  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
 */

/****************************************************************
 *      This program is free software; you can redistribute it and/or modify
 *      it under the terms of the GNU General Public License as published by
 *      the Free Software Foundation; either version 2, or (at your option)
 *      any later version.
 *
 *      This program is distributed in the hope that it will be useful,
 *      but WITHOUT ANY WARRANTY; without even the implied warranty of
 *      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *      GNU General Public License for more details.
 *
 *      You should have received a copy of the GNU General Public License
 *      along with this program; if not, write to the Free Software
 *      Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 ****************************************************************/

#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>

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

#define MAX_PARAM_LENGTH        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 = false;
module_param(oops_only, bool, 0600);
MODULE_PARM_DESC(oops_only, "Only log oops messages");

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

/* Linked list of all configured targets */
static LIST_HEAD(target_list);

/* This needs to be a spinlock because write_msg() cannot sleep */
static DEFINE_SPINLOCK(target_list_lock);

/*
 * Console driver for extended netconsoles.  Registered on the first use to
 * avoid unnecessarily enabling ext message formatting.
 */
static struct console netconsole_ext;

/**
 * struct netconsole_target - Represents a configured netconsole target.
 * @list:       Links this target into the target_list.
 * @item:       Links us into the configfs subsystem hierarchy.
 * @enabled:    On / off knob to enable / disable target.
 *              Visible from userspace (read-write).
 *              We maintain a strict 1:1 correspondence between this and
 *              whether the corresponding netpoll is active or inactive.
 *              Also, other parameters of a target may be modified at
 *              runtime only when it is disabled (enabled == 0).
 * @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)
 */
struct netconsole_target {
        struct list_head        list;
#ifdef  CONFIG_NETCONSOLE_DYNAMIC
        struct config_item      item;
#endif
        bool                    enabled;
        bool                    extended;
        struct netpoll          np;
};

#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->item))
                config_item_get(&nt->item);
}

static void netconsole_target_put(struct netconsole_target *nt)
{
        if (config_item_name(&nt->item))
                config_item_put(&nt->item);
}

#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)
{
}

#endif  /* CONFIG_NETCONSOLE_DYNAMIC */

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

        /*
         * Allocate and initialize with defaults.
         * Note that these targets get their config_item fields zeroed-out.
         */
        nt = kzalloc(sizeof(*nt), GFP_KERNEL);
        if (!nt)
                goto fail;

        nt->np.name = "netconsole";
        strlcpy(nt->np.dev_name, "eth0", IFNAMSIZ);
        nt->np.local_port = 6665;
        nt->np.remote_port = 6666;
        eth_broadcast_addr(nt->np.remote_mac);

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

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

        err = netpoll_setup(&nt->np);
        if (err)
                goto fail;

        nt->enabled = true;

        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)
{
        netpoll_cleanup(&nt->np);
        kfree(nt);
}

#ifdef  CONFIG_NETCONSOLE_DYNAMIC

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

static struct netconsole_target *to_target(struct config_item *item)
{
        return item ?
                container_of(item, struct netconsole_target, item) :
                NULL;
}

/*
 * Attribute operations for netconsole_target.
 */

static ssize_t enabled_show(struct config_item *item, char *buf)
{
        return snprintf(buf, PAGE_SIZE, "%d\n", to_target(item)->enabled);
}

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

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

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

static ssize_t remote_port_show(struct config_item *item, char *buf)
{
        return snprintf(buf, PAGE_SIZE, "%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 snprintf(buf, PAGE_SIZE, "%pI6c\n", &nt->np.local_ip.in6);
        else
                return snprintf(buf, PAGE_SIZE, "%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 snprintf(buf, PAGE_SIZE, "%pI6c\n", &nt->np.remote_ip.in6);
        else
                return snprintf(buf, PAGE_SIZE, "%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 snprintf(buf, PAGE_SIZE, "%pM\n", dev ? dev->dev_addr : bcast);
}

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

/*
 * 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);
        unsigned long flags;
        int enabled;
        int err;

        mutex_lock(&dynamic_netconsole_mutex);
        err = kstrtoint(buf, 10, &enabled);
        if (err < 0)
                goto out_unlock;

        err = -EINVAL;
        if (enabled < 0 || enabled > 1)
                goto out_unlock;
        if ((bool)enabled == nt->enabled) {
                pr_info("network logging has already %s\n",
                        nt->enabled ? "started" : "stopped");
                goto out_unlock;
        }

        if (enabled) {  /* true */
                if (nt->extended && !(netconsole_ext.flags & CON_ENABLED)) {
                        netconsole_ext.flags |= CON_ENABLED;
                        register_console(&netconsole_ext);
                }

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

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

                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->enabled == true
                 */
                spin_lock_irqsave(&target_list_lock, flags);
                nt->enabled = false;
                spin_unlock_irqrestore(&target_list_lock, flags);
                netpoll_cleanup(&nt->np);
        }

        nt->enabled = enabled;

        mutex_unlock(&dynamic_netconsole_mutex);
        return strnlen(buf, count);
out_unlock:
        mutex_unlock(&dynamic_netconsole_mutex);
        return err;
}

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

        mutex_lock(&dynamic_netconsole_mutex);
        if (nt->enabled) {
                pr_err("target (%s) is enabled, disable to update parameters\n",
                       config_item_name(&nt->item));
                err = -EINVAL;
                goto out_unlock;
        }

        err = kstrtoint(buf, 10, &extended);
        if (err < 0)
                goto out_unlock;
        if (extended < 0 || extended > 1) {
                err = -EINVAL;
                goto out_unlock;
        }

        nt->extended = extended;

        mutex_unlock(&dynamic_netconsole_mutex);
        return strnlen(buf, count);
out_unlock:
        mutex_unlock(&dynamic_netconsole_mutex);
        return err;
}

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

        mutex_lock(&dynamic_netconsole_mutex);
        if (nt->enabled) {
                pr_err("target (%s) is enabled, disable to update parameters\n",
                       config_item_name(&nt->item));
                mutex_unlock(&dynamic_netconsole_mutex);
                return -EINVAL;
        }

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

        /* Get rid of possible trailing newline from echo(1) */
        len = strnlen(nt->np.dev_name, IFNAMSIZ);
        if (nt->np.dev_name[len - 1] == '\n')
                nt->np.dev_name[len - 1] = '\0';

        mutex_unlock(&dynamic_netconsole_mutex);
        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);
        int rv = -EINVAL;

        mutex_lock(&dynamic_netconsole_mutex);
        if (nt->enabled) {
                pr_err("target (%s) is enabled, disable to update parameters\n",
                       config_item_name(&nt->item));
                goto out_unlock;
        }

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

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

        mutex_lock(&dynamic_netconsole_mutex);
        if (nt->enabled) {
                pr_err("target (%s) is enabled, disable to update parameters\n",
                       config_item_name(&nt->item));
                goto out_unlock;
        }

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

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

        mutex_lock(&dynamic_netconsole_mutex);
        if (nt->enabled) {
                pr_err("target (%s) is enabled, disable to update parameters\n",
                       config_item_name(&nt->item));
                goto out_unlock;
        }

        if (strnchr(buf, count, ':')) {
                const char *end;
                if (in6_pton(buf, count, nt->np.local_ip.in6.s6_addr, -1, &end) > 0) {
                        if (*end && *end != '\n') {
                                pr_err("invalid IPv6 address at: <%c>\n", *end);
                                goto out_unlock;
                        }
                        nt->np.ipv6 = true;
                } else
                        goto out_unlock;
        } else {
                if (!nt->np.ipv6) {
                        nt->np.local_ip.ip = in_aton(buf);
                } else
                        goto out_unlock;
        }

        mutex_unlock(&dynamic_netconsole_mutex);
        return strnlen(buf, count);
out_unlock:
        mutex_unlock(&dynamic_netconsole_mutex);
        return -EINVAL;
}

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

        mutex_lock(&dynamic_netconsole_mutex);
        if (nt->enabled) {
                pr_err("target (%s) is enabled, disable to update parameters\n",
                       config_item_name(&nt->item));
                goto out_unlock;
        }

        if (strnchr(buf, count, ':')) {
                const char *end;
                if (in6_pton(buf, count, nt->np.remote_ip.in6.s6_addr, -1, &end) > 0) {
                        if (*end && *end != '\n') {
                                pr_err("invalid IPv6 address at: <%c>\n", *end);
                                goto out_unlock;
                        }
                        nt->np.ipv6 = true;
                } else
                        goto out_unlock;
        } else {
                if (!nt->np.ipv6) {
                        nt->np.remote_ip.ip = in_aton(buf);
                } else
                        goto out_unlock;
        }

        mutex_unlock(&dynamic_netconsole_mutex);
        return strnlen(buf, count);
out_unlock:
        mutex_unlock(&dynamic_netconsole_mutex);
        return -EINVAL;
}

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];

        mutex_lock(&dynamic_netconsole_mutex);
        if (nt->enabled) {
                pr_err("target (%s) is enabled, disable to update parameters\n",
                       config_item_name(&nt->item));
                goto out_unlock;
        }

        if (!mac_pton(buf, remote_mac))
                goto out_unlock;
        if (buf[3 * ETH_ALEN - 1] && buf[3 * ETH_ALEN - 1] != '\n')
                goto out_unlock;
        memcpy(nt->np.remote_mac, remote_mac, ETH_ALEN);

        mutex_unlock(&dynamic_netconsole_mutex);
        return strnlen(buf, count);
out_unlock:
        mutex_unlock(&dynamic_netconsole_mutex);
        return -EINVAL;
}

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);

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

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

static void netconsole_target_release(struct config_item *item)
{
        kfree(to_target(item));
}

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,
};

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

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

        /*
         * Allocate and initialize with defaults.
         * Target is disabled at creation (!enabled).
         */
        nt = kzalloc(sizeof(*nt), GFP_KERNEL);
        if (!nt)
                return ERR_PTR(-ENOMEM);

        nt->np.name = "netconsole";
        strlcpy(nt->np.dev_name, "eth0", IFNAMSIZ);
        nt->np.local_port = 6665;
        nt->np.remote_port = 6666;
        eth_broadcast_addr(nt->np.remote_mac);

        /* Initialize the config_item member */
        config_item_init_type_name(&nt->item, name, &netconsole_target_type);

        /* 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->item;
}

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

        spin_lock_irqsave(&target_list_lock, flags);
        list_del(&nt->list);
        spin_unlock_irqrestore(&target_list_lock, flags);

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

        config_item_put(&nt->item);
}

static struct configfs_group_operations netconsole_subsys_group_ops = {
        .make_item      = 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,
                },
        },
};

#endif  /* CONFIG_NETCONSOLE_DYNAMIC */

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

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

        spin_lock_irqsave(&target_list_lock, flags);
restart:
        list_for_each_entry(nt, &target_list, list) {
                netconsole_target_get(nt);
                if (nt->np.dev == dev) {
                        switch (event) {
                        case NETDEV_CHANGENAME:
                                strlcpy(nt->np.dev_name, dev->name, IFNAMSIZ);
                                break;
                        case NETDEV_RELEASE:
                        case NETDEV_JOIN:
                        case NETDEV_UNREGISTER:
                                /* rtnl_lock already held
                                 * we might sleep in __netpoll_cleanup()
                                 */
                                spin_unlock_irqrestore(&target_list_lock, flags);

                                __netpoll_cleanup(&nt->np);

                                spin_lock_irqsave(&target_list_lock, flags);
                                dev_put(nt->np.dev);
                                nt->np.dev = NULL;
                                nt->enabled = false;
                                stopped = true;
                                netconsole_target_put(nt);
                                goto restart;
                        }
                }
                netconsole_target_put(nt);
        }
        spin_unlock_irqrestore(&target_list_lock, flags);
        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);
        }

done:
        return NOTIFY_DONE;
}

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

/**
 * send_ext_msg_udp - send extended log message to target
 * @nt: target to send message to
 * @msg: extended log message to send
 * @msg_len: length of message
 *
 * Transfer extended log @msg to @nt.  If @msg 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, const char *msg,
                             int msg_len)
{
        static char buf[MAX_PRINT_CHUNK]; /* protected by target_list_lock */
        const char *header, *body;
        int offset = 0;
        int header_len, body_len;

        if (msg_len <= MAX_PRINT_CHUNK) {
                netpoll_send_udp(&nt->np, msg, msg_len);
                return;
        }

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

        header_len = body - header;
        body_len = msg_len - header_len - 1;
        body++;

        /*
         * Transfer multiple chunks with the following extra header.
         * "ncfrag=<byte-offset>/<total-bytes>"
         */
        memcpy(buf, header, header_len);

        while (offset < body_len) {
                int this_header = header_len;
                int this_chunk;

                this_header += scnprintf(buf + this_header,
                                         sizeof(buf) - this_header,
                                         ",ncfrag=%d/%d;", offset, body_len);

                this_chunk = min(body_len - offset,
                                 MAX_PRINT_CHUNK - this_header);
                if (WARN_ON_ONCE(this_chunk <= 0))
                        return;

                memcpy(buf + this_header, body + offset, this_chunk);

                netpoll_send_udp(&nt->np, buf, this_header + this_chunk);

                offset += this_chunk;
        }
}

static void write_ext_msg(struct console *con, const char *msg,
                          unsigned int len)
{
        struct netconsole_target *nt;
        unsigned long flags;

        if ((oops_only && !oops_in_progress) || list_empty(&target_list))
                return;

        spin_lock_irqsave(&target_list_lock, flags);
        list_for_each_entry(nt, &target_list, list)
                if (nt->extended && nt->enabled && netif_running(nt->np.dev))
                        send_ext_msg_udp(nt, msg, len);
        spin_unlock_irqrestore(&target_list_lock, flags);
}

static void write_msg(struct console *con, const char *msg, unsigned int len)
{
        int frag, left;
        unsigned long flags;
        struct netconsole_target *nt;
        const char *tmp;

        if (oops_only && !oops_in_progress)
                return;
        /* Avoid taking lock and disabling interrupts unnecessarily */
        if (list_empty(&target_list))
                return;

        spin_lock_irqsave(&target_list_lock, flags);
        list_for_each_entry(nt, &target_list, list) {
                if (!nt->extended && nt->enabled && netif_running(nt->np.dev)) {
                        /*
                         * We nest this inside the for-each-target loop above
                         * so that we're able to get as much logging out to
                         * at least one target if we die inside here, instead
                         * of unnecessarily keeping all targets in lock-step.
                         */
                        tmp = msg;
                        for (left = len; left;) {
                                frag = min(left, MAX_PRINT_CHUNK);
                                netpoll_send_udp(&nt->np, tmp, frag);
                                tmp += frag;
                                left -= frag;
                        }
                }
        }
        spin_unlock_irqrestore(&target_list_lock, flags);
}

static struct console netconsole_ext = {
        .name   = "netcon_ext",
        .flags  = CON_EXTENDED, /* starts disabled, registered on first use */
        .write  = write_ext_msg,
};

static struct console netconsole = {
        .name   = "netcon",
        .flags  = CON_ENABLED,
        .write  = write_msg,
};

static int __init init_netconsole(void)
{
        int err;
        struct netconsole_target *nt, *tmp;
        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);
                        if (IS_ERR(nt)) {
                                err = PTR_ERR(nt);
                                goto fail;
                        }
                        /* Dump existing printks when we register */
                        if (nt->extended)
                                netconsole_ext.flags |= CON_PRINTBUFFER |
                                                        CON_ENABLED;
                        else
                                netconsole.flags |= CON_PRINTBUFFER;

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

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

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

        if (netconsole_ext.flags & CON_ENABLED)
                register_console(&netconsole_ext);
        register_console(&netconsole);
        pr_info("network logging started\n");

        return err;

undonotifier:
        unregister_netdevice_notifier(&netconsole_netdev_notifier);

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

        /*
         * 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);
        }

        return err;
}

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

        unregister_console(&netconsole_ext);
        unregister_console(&netconsole);
        dynamic_netconsole_exit();
        unregister_netdevice_notifier(&netconsole_netdev_notifier);

        /*
         * 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);
        }
}

/*
 * 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);