// SPDX-License-Identifier: GPL-2.0-only
/*
 * Common framework for low-level network console, dump, and debugger code
 *
 * Sep 8 2003  Matt Mackall <mpm@selenic.com>
 *
 * based on the netconsole code from:
 *
 * Copyright (C) 2001  Ingo Molnar <mingo@redhat.com>
 * Copyright (C) 2002  Red Hat, Inc.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/moduleparam.h>
#include <linux/kernel.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/string.h>
#include <linux/if_arp.h>
#include <linux/inetdevice.h>
#include <linux/inet.h>
#include <linux/interrupt.h>
#include <linux/netpoll.h>
#include <linux/sched.h>
#include <linux/delay.h>
#include <linux/rcupdate.h>
#include <linux/workqueue.h>
#include <linux/slab.h>
#include <linux/export.h>
#include <linux/if_vlan.h>
#include <linux/udp.h>
#include <net/tcp.h>
#include <net/addrconf.h>
#include <net/ndisc.h>
#include <trace/events/napi.h>
#include <linux/kconfig.h>

/*
 * We maintain a small pool of fully-sized skbs, to make sure the
 * message gets out even in extreme OOM situations.
 */

#define MAX_SKBS 32
#define USEC_PER_POLL   50

static unsigned int carrier_timeout = 4;
module_param(carrier_timeout, uint, 0644);

static netdev_tx_t netpoll_start_xmit(struct sk_buff *skb,
                                      struct net_device *dev,
                                      struct netdev_queue *txq)
{
        netdev_tx_t status = NETDEV_TX_OK;
        netdev_features_t features;

        features = netif_skb_features(skb);

        if (skb_vlan_tag_present(skb) &&
            !vlan_hw_offload_capable(features, skb->vlan_proto)) {
                skb = __vlan_hwaccel_push_inside(skb);
                if (unlikely(!skb)) {
                        /* This is actually a packet drop, but we
                         * don't want the code that calls this
                         * function to try and operate on a NULL skb.
                         */
                        goto out;
                }
        }

        status = netdev_start_xmit(skb, dev, txq, false);

out:
        return status;
}

static void queue_process(struct work_struct *work)
{
        struct netpoll_info *npinfo =
                container_of(work, struct netpoll_info, tx_work.work);
        struct sk_buff *skb;
        unsigned long flags;

        while ((skb = skb_dequeue(&npinfo->txq))) {
                struct net_device *dev = skb->dev;
                struct netdev_queue *txq;
                unsigned int q_index;

                if (!netif_device_present(dev) || !netif_running(dev)) {
                        kfree_skb(skb);
                        continue;
                }

                local_irq_save(flags);
                /* check if skb->queue_mapping is still valid */
                q_index = skb_get_queue_mapping(skb);
                if (unlikely(q_index >= dev->real_num_tx_queues)) {
                        q_index = q_index % dev->real_num_tx_queues;
                        skb_set_queue_mapping(skb, q_index);
                }
                txq = netdev_get_tx_queue(dev, q_index);
                HARD_TX_LOCK(dev, txq, smp_processor_id());
                if (netif_xmit_frozen_or_stopped(txq) ||
                    !dev_xmit_complete(netpoll_start_xmit(skb, dev, txq))) {
                        skb_queue_head(&npinfo->txq, skb);
                        HARD_TX_UNLOCK(dev, txq);
                        local_irq_restore(flags);

                        schedule_delayed_work(&npinfo->tx_work, HZ/10);
                        return;
                }
                HARD_TX_UNLOCK(dev, txq);
                local_irq_restore(flags);
        }
}

static int netif_local_xmit_active(struct net_device *dev)
{
        int i;

        for (i = 0; i < dev->num_tx_queues; i++) {
                struct netdev_queue *txq = netdev_get_tx_queue(dev, i);

                if (netif_tx_owned(txq, smp_processor_id()))
                        return 1;
        }

        return 0;
}

static void poll_one_napi(struct napi_struct *napi)
{
        int work;

        /* If we set this bit but see that it has already been set,
         * that indicates that napi has been disabled and we need
         * to abort this operation
         */
        if (test_and_set_bit(NAPI_STATE_NPSVC, &napi->state))
                return;

        /* We explicitly pass the polling call a budget of 0 to
         * indicate that we are clearing the Tx path only.
         */
        work = napi->poll(napi, 0);
        WARN_ONCE(work, "%pS exceeded budget in poll\n", napi->poll);
        trace_napi_poll(napi, work, 0);

        clear_bit(NAPI_STATE_NPSVC, &napi->state);
}

static void poll_napi(struct net_device *dev)
{
        struct napi_struct *napi;
        int cpu = smp_processor_id();

        list_for_each_entry_rcu(napi, &dev->napi_list, dev_list) {
                if (cmpxchg(&napi->poll_owner, -1, cpu) == -1) {
                        poll_one_napi(napi);
                        smp_store_release(&napi->poll_owner, -1);
                }
        }
}

void netpoll_poll_dev(struct net_device *dev)
{
        struct netpoll_info *ni = rcu_dereference_bh(dev->npinfo);
        const struct net_device_ops *ops;

        /* Don't do any rx activity if the dev_lock mutex is held
         * the dev_open/close paths use this to block netpoll activity
         * while changing device state
         */
        if (!ni || down_trylock(&ni->dev_lock))
                return;

        /* Some drivers will take the same locks in poll and xmit,
         * we can't poll if local CPU is already in xmit.
         */
        if (!netif_running(dev) || netif_local_xmit_active(dev)) {
                up(&ni->dev_lock);
                return;
        }

        ops = dev->netdev_ops;
        if (ops->ndo_poll_controller)
                ops->ndo_poll_controller(dev);

        poll_napi(dev);

        up(&ni->dev_lock);

        netpoll_zap_completion_queue();
}
EXPORT_SYMBOL(netpoll_poll_dev);

void netpoll_poll_disable(struct net_device *dev)
{
        struct netpoll_info *ni;

        might_sleep();
        ni = rtnl_dereference(dev->npinfo);
        if (ni)
                down(&ni->dev_lock);
}

void netpoll_poll_enable(struct net_device *dev)
{
        struct netpoll_info *ni;

        ni = rtnl_dereference(dev->npinfo);
        if (ni)
                up(&ni->dev_lock);
}

static void refill_skbs(struct netpoll *np)
{
        struct sk_buff_head *skb_pool;
        struct sk_buff *skb;

        skb_pool = &np->skb_pool;

        while (READ_ONCE(skb_pool->qlen) < MAX_SKBS) {
                skb = alloc_skb(MAX_SKB_SIZE, GFP_ATOMIC);
                if (!skb)
                        break;

                skb_queue_tail(skb_pool, skb);
        }
}

void netpoll_zap_completion_queue(void)
{
        unsigned long flags;
        struct softnet_data *sd = &get_cpu_var(softnet_data);

        if (sd->completion_queue) {
                struct sk_buff *clist;

                local_irq_save(flags);
                clist = sd->completion_queue;
                sd->completion_queue = NULL;
                local_irq_restore(flags);

                while (clist != NULL) {
                        struct sk_buff *skb = clist;
                        clist = clist->next;
                        if (!skb_irq_freeable(skb)) {
                                refcount_set(&skb->users, 1);
                                dev_kfree_skb_any(skb); /* put this one back */
                        } else {
                                __kfree_skb(skb);
                        }
                }
        }

        put_cpu_var(softnet_data);
}
EXPORT_SYMBOL_NS_GPL(netpoll_zap_completion_queue, "NETDEV_INTERNAL");

static int netpoll_owner_active(struct net_device *dev)
{
        struct napi_struct *napi;

        list_for_each_entry_rcu(napi, &dev->napi_list, dev_list) {
                if (READ_ONCE(napi->poll_owner) == smp_processor_id())
                        return 1;
        }
        return 0;
}

/* call with IRQ disabled */
static netdev_tx_t __netpoll_send_skb(struct netpoll *np, struct sk_buff *skb)
{
        netdev_tx_t status = NETDEV_TX_BUSY;
        netdev_tx_t ret = NET_XMIT_DROP;
        struct net_device *dev;
        unsigned long tries;
        /* It is up to the caller to keep npinfo alive. */
        struct netpoll_info *npinfo;

        lockdep_assert_irqs_disabled();

        dev = np->dev;
        /* npinfo->txq belongs to np->dev, so retries must stay bound to it. */
        skb->dev = dev;
        rcu_read_lock();
        npinfo = rcu_dereference_bh(dev->npinfo);

        if (!npinfo || !netif_running(dev) || !netif_device_present(dev)) {
                dev_kfree_skb_irq(skb);
                goto out;
        }

        /* don't get messages out of order, and no recursion */
        if (skb_queue_len(&npinfo->txq) == 0 && !netpoll_owner_active(dev)) {
                struct netdev_queue *txq;

                txq = netdev_core_pick_tx(dev, skb, NULL);

                /* try until next clock tick */
                for (tries = jiffies_to_usecs(1)/USEC_PER_POLL;
                     tries > 0; --tries) {
                        if (HARD_TX_TRYLOCK(dev, txq)) {
                                if (!netif_xmit_stopped(txq))
                                        status = netpoll_start_xmit(skb, dev, txq);

                                HARD_TX_UNLOCK(dev, txq);

                                if (dev_xmit_complete(status))
                                        break;

                        }

                        /* tickle device maybe there is some cleanup */
                        netpoll_poll_dev(np->dev);

                        udelay(USEC_PER_POLL);
                }

                WARN_ONCE(!irqs_disabled(),
                        "netpoll_send_skb_on_dev(): %s enabled interrupts in poll (%pS)\n",
                        dev->name, dev->netdev_ops->ndo_start_xmit);

        }

        if (!dev_xmit_complete(status)) {
                skb_queue_tail(&npinfo->txq, skb);
                schedule_delayed_work(&npinfo->tx_work,0);
        }
        ret = NETDEV_TX_OK;
out:
        rcu_read_unlock();
        return ret;
}

netdev_tx_t netpoll_send_skb(struct netpoll *np, struct sk_buff *skb)
{
        unsigned long flags;
        netdev_tx_t ret;

        if (unlikely(!np)) {
                dev_kfree_skb_irq(skb);
                ret = NET_XMIT_DROP;
        } else {
                local_irq_save(flags);
                ret = __netpoll_send_skb(np, skb);
                local_irq_restore(flags);
        }
        return ret;
}
EXPORT_SYMBOL(netpoll_send_skb);

static void skb_pool_flush(struct netpoll *np)
{
        struct sk_buff_head *skb_pool;

        cancel_work_sync(&np->refill_wq);
        skb_pool = &np->skb_pool;
        skb_queue_purge_reason(skb_pool, SKB_CONSUMED);
}

static void refill_skbs_work_handler(struct work_struct *work)
{
        struct netpoll *np =
                container_of(work, struct netpoll, refill_wq);

        refill_skbs(np);
}

int __netpoll_setup(struct netpoll *np, struct net_device *ndev)
{
        struct netpoll_info *npinfo;
        const struct net_device_ops *ops;
        int err;

        skb_queue_head_init(&np->skb_pool);
        INIT_WORK(&np->refill_wq, refill_skbs_work_handler);

        if (ndev->priv_flags & IFF_DISABLE_NETPOLL) {
                np_err(np, "%s doesn't support polling, aborting\n",
                       ndev->name);
                err = -ENOTSUPP;
                goto out;
        }

        npinfo = rtnl_dereference(ndev->npinfo);
        if (!npinfo) {
                npinfo = kmalloc_obj(*npinfo);
                if (!npinfo) {
                        err = -ENOMEM;
                        goto out;
                }

                sema_init(&npinfo->dev_lock, 1);
                skb_queue_head_init(&npinfo->txq);
                INIT_DELAYED_WORK(&npinfo->tx_work, queue_process);

                refcount_set(&npinfo->refcnt, 1);

                ops = ndev->netdev_ops;
                if (ops->ndo_netpoll_setup) {
                        err = ops->ndo_netpoll_setup(ndev);
                        if (err)
                                goto free_npinfo;
                }
        } else {
                refcount_inc(&npinfo->refcnt);
        }

        np->dev = ndev;
        strscpy(np->dev_name, ndev->name, IFNAMSIZ);

        /* fill up the skb queue */
        refill_skbs(np);

        /* last thing to do is link it to the net device structure */
        rcu_assign_pointer(ndev->npinfo, npinfo);

        return 0;

free_npinfo:
        kfree(npinfo);
out:
        return err;
}
EXPORT_SYMBOL_GPL(__netpoll_setup);

/*
 * Returns a pointer to a string representation of the identifier used
 * to select the egress interface for the given netpoll instance. buf
 * is used to format np->dev_mac when np->dev_name is empty; bufsz must
 * be at least MAC_ADDR_STR_LEN + 1 to fit the formatted MAC address
 * and its NUL terminator.
 */
static char *egress_dev(struct netpoll *np, char *buf, size_t bufsz)
{
        if (np->dev_name[0])
                return np->dev_name;

        snprintf(buf, bufsz, "%pM", np->dev_mac);
        return buf;
}

static void netpoll_wait_carrier(struct netpoll *np, struct net_device *ndev,
                                 unsigned int timeout)
{
        unsigned long atmost;

        atmost = jiffies + timeout * HZ;
        while (!netif_carrier_ok(ndev)) {
                if (time_after(jiffies, atmost)) {
                        np_notice(np, "timeout waiting for carrier\n");
                        break;
                }
                msleep(1);
        }
}

/*
 * Take the IPv6 from ndev and populate local_ip structure in netpoll
 */
static int netpoll_take_ipv6(struct netpoll *np, struct net_device *ndev)
{
        char buf[MAC_ADDR_STR_LEN + 1];
        int err = -EDESTADDRREQ;
        struct inet6_dev *idev;

        if (!IS_ENABLED(CONFIG_IPV6)) {
                np_err(np, "IPv6 is not supported %s, aborting\n",
                       egress_dev(np, buf, sizeof(buf)));
                return -EINVAL;
        }

        idev = __in6_dev_get(ndev);
        if (idev) {
                struct inet6_ifaddr *ifp;

                read_lock_bh(&idev->lock);
                list_for_each_entry(ifp, &idev->addr_list, if_list) {
                        if (!!(ipv6_addr_type(&ifp->addr) & IPV6_ADDR_LINKLOCAL) !=
                                !!(ipv6_addr_type(&np->remote_ip.in6) & IPV6_ADDR_LINKLOCAL))
                                continue;
                        /* Got the IP, let's return */
                        np->local_ip.in6 = ifp->addr;
                        err = 0;
                        break;
                }
                read_unlock_bh(&idev->lock);
        }
        if (err) {
                np_err(np, "no IPv6 address for %s, aborting\n",
                       egress_dev(np, buf, sizeof(buf)));
                return err;
        }

        np_info(np, "local IPv6 %pI6c\n", &np->local_ip.in6);
        return 0;
}

/*
 * Take the IPv4 from ndev and populate local_ip structure in netpoll
 */
static int netpoll_take_ipv4(struct netpoll *np, struct net_device *ndev)
{
        char buf[MAC_ADDR_STR_LEN + 1];
        const struct in_ifaddr *ifa;
        struct in_device *in_dev;

        in_dev = __in_dev_get_rtnl(ndev);
        if (!in_dev) {
                np_err(np, "no IP address for %s, aborting\n",
                       egress_dev(np, buf, sizeof(buf)));
                return -EDESTADDRREQ;
        }

        ifa = rtnl_dereference(in_dev->ifa_list);
        if (!ifa) {
                np_err(np, "no IP address for %s, aborting\n",
                       egress_dev(np, buf, sizeof(buf)));
                return -EDESTADDRREQ;
        }

        np->local_ip.ip = ifa->ifa_local;
        np_info(np, "local IP %pI4\n", &np->local_ip.ip);

        return 0;
}

/*
 * Test whether the caller left np->local_ip unset, so that
 * netpoll_setup() should auto-populate it from the egress device.
 *
 * np->local_ip is a union of __be32 (IPv4) and struct in6_addr (IPv6),
 * so an IPv6 address whose first 4 bytes are zero (e.g. ::1, ::2,
 * IPv4-mapped ::ffff:a.b.c.d) must not be tested via the IPv4 arm —
 * doing so would misclassify a caller-supplied address as unset and
 * silently overwrite it with whatever address the device exposes.
 */
static bool netpoll_local_ip_unset(const struct netpoll *np)
{
        if (np->ipv6)
                return ipv6_addr_any(&np->local_ip.in6);
        return !np->local_ip.ip;
}

int netpoll_setup(struct netpoll *np)
{
        struct net *net = current->nsproxy->net_ns;
        char buf[MAC_ADDR_STR_LEN + 1];
        struct net_device *ndev = NULL;
        bool ip_overwritten = false;
        int err;

        rtnl_lock();
        if (np->dev_name[0])
                ndev = __dev_get_by_name(net, np->dev_name);
        else if (is_valid_ether_addr(np->dev_mac))
                ndev = dev_getbyhwaddr(net, ARPHRD_ETHER, np->dev_mac);

        if (!ndev) {
                np_err(np, "%s doesn't exist, aborting\n",
                       egress_dev(np, buf, sizeof(buf)));
                err = -ENODEV;
                goto unlock;
        }
        netdev_hold(ndev, &np->dev_tracker, GFP_KERNEL);

        if (netdev_master_upper_dev_get(ndev)) {
                np_err(np, "%s is a slave device, aborting\n",
                       egress_dev(np, buf, sizeof(buf)));
                err = -EBUSY;
                goto put;
        }

        if (!netif_running(ndev)) {
                np_info(np, "device %s not up yet, forcing it\n",
                        egress_dev(np, buf, sizeof(buf)));

                err = dev_open(ndev, NULL);
                if (err) {
                        np_err(np, "failed to open %s\n", ndev->name);
                        goto put;
                }

                rtnl_unlock();
                netpoll_wait_carrier(np, ndev, carrier_timeout);
                rtnl_lock();
        }

        if (netpoll_local_ip_unset(np)) {
                if (!np->ipv6) {
                        err = netpoll_take_ipv4(np, ndev);
                        if (err)
                                goto put;
                } else {
                        err = netpoll_take_ipv6(np, ndev);
                        if (err)
                                goto put;
                }
                ip_overwritten = true;
        }

        err = __netpoll_setup(np, ndev);
        if (err)
                goto flush;
        rtnl_unlock();

        /* Make sure all NAPI polls which started before dev->npinfo
         * was visible have exited before we start calling NAPI poll.
         * NAPI skips locking if dev->npinfo is NULL.
         */
        synchronize_rcu();

        return 0;

flush:
        skb_pool_flush(np);
put:
        DEBUG_NET_WARN_ON_ONCE(np->dev);
        if (ip_overwritten)
                memset(&np->local_ip, 0, sizeof(np->local_ip));
        netdev_put(ndev, &np->dev_tracker);
unlock:
        rtnl_unlock();
        return err;
}
EXPORT_SYMBOL(netpoll_setup);

static void rcu_cleanup_netpoll_info(struct rcu_head *rcu_head)
{
        struct netpoll_info *npinfo =
                        container_of(rcu_head, struct netpoll_info, rcu);

        skb_queue_purge(&npinfo->txq);
        kfree(npinfo);
}

static void __netpoll_cleanup(struct netpoll *np)
{
        struct netpoll_info *npinfo;

        npinfo = rtnl_dereference(np->dev->npinfo);
        if (!npinfo)
                return;

        /* At this point, there is a single npinfo instance per netdevice, and
         * its refcnt tracks how many netpoll structures are linked to it. We
         * only perform npinfo cleanup when the refcnt decrements to zero.
         */
        if (refcount_dec_and_test(&npinfo->refcnt)) {
                const struct net_device_ops *ops;

                ops = np->dev->netdev_ops;
                if (ops->ndo_netpoll_cleanup)
                        ops->ndo_netpoll_cleanup(np->dev);

                RCU_INIT_POINTER(np->dev->npinfo, NULL);
                disable_delayed_work_sync(&npinfo->tx_work);
                call_rcu(&npinfo->rcu, rcu_cleanup_netpoll_info);
        }

        skb_pool_flush(np);
}

void __netpoll_free(struct netpoll *np)
{
        ASSERT_RTNL();

        /* Wait for transmitting packets to finish before freeing. */
        synchronize_net();
        __netpoll_cleanup(np);
        kfree(np);
}
EXPORT_SYMBOL_GPL(__netpoll_free);

void do_netpoll_cleanup(struct netpoll *np)
{
        __netpoll_cleanup(np);
        netdev_put(np->dev, &np->dev_tracker);
        np->dev = NULL;
}
EXPORT_SYMBOL(do_netpoll_cleanup);

void netpoll_cleanup(struct netpoll *np)
{
        rtnl_lock();
        if (!np->dev)
                goto out;
        do_netpoll_cleanup(np);
out:
        rtnl_unlock();
}
EXPORT_SYMBOL(netpoll_cleanup);