// SPDX-License-Identifier: GPL-2.0-or-later
/** -*- linux-c -*- ***********************************************************
 * Linux PPP over Ethernet (PPPoX/PPPoE) Sockets
 *
 * PPPoX --- Generic PPP encapsulation socket family
 * PPPoE --- PPP over Ethernet (RFC 2516)
 *
 * Version:     0.7.0
 *
 * 070228 :     Fix to allow multiple sessions with same remote MAC and same
 *              session id by including the local device ifindex in the
 *              tuple identifying a session. This also ensures packets can't
 *              be injected into a session from interfaces other than the one
 *              specified by userspace. Florian Zumbiehl <florz@florz.de>
 *              (Oh, BTW, this one is YYMMDD, in case you were wondering ...)
 * 220102 :     Fix module use count on failure in pppoe_create, pppox_sk -acme
 * 030700 :     Fixed connect logic to allow for disconnect.
 * 270700 :     Fixed potential SMP problems; we must protect against
 *              simultaneous invocation of ppp_input
 *              and ppp_unregister_channel.
 * 040800 :     Respect reference count mechanisms on net-devices.
 * 200800 :     fix kfree(skb) in pppoe_rcv (acme)
 *              Module reference count is decremented in the right spot now,
 *              guards against sock_put not actually freeing the sk
 *              in pppoe_release.
 * 051000 :     Initialization cleanup.
 * 111100 :     Fix recvmsg.
 * 050101 :     Fix PADT processing.
 * 140501 :     Use pppoe_rcv_core to handle all backlog. (Alexey)
 * 170701 :     Do not lock_sock with rwlock held. (DaveM)
 *              Ignore discovery frames if user has socket
 *              locked. (DaveM)
 *              Ignore return value of dev_queue_xmit in __pppoe_xmit
 *              or else we may kfree an SKB twice. (DaveM)
 * 190701 :     When doing copies of skb's in __pppoe_xmit, always delete
 *              the original skb that was passed in on success, never on
 *              failure.  Delete the copy of the skb on failure to avoid
 *              a memory leak.
 * 081001 :     Misc. cleanup (licence string, non-blocking, prevent
 *              reference of device on close).
 * 121301 :     New ppp channels interface; cannot unregister a channel
 *              from interrupts.  Thus, we mark the socket as a ZOMBIE
 *              and do the unregistration later.
 * 081002 :     seq_file support for proc stuff -acme
 * 111602 :     Merge all 2.4 fixes into 2.5/2.6 tree.  Label 2.5/2.6
 *              as version 0.7.  Spacing cleanup.
 * Author:      Michal Ostrowski <mostrows@speakeasy.net>
 * Contributors:
 *              Arnaldo Carvalho de Melo <acme@conectiva.com.br>
 *              David S. Miller (davem@redhat.com)
 *
 * License:
 */

#include <linux/string.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/errno.h>
#include <linux/netdevice.h>
#include <linux/net.h>
#include <linux/inetdevice.h>
#include <linux/etherdevice.h>
#include <linux/skbuff.h>
#include <linux/init.h>
#include <linux/if_ether.h>
#include <linux/if_pppox.h>
#include <linux/ppp_channel.h>
#include <linux/ppp_defs.h>
#include <linux/ppp-ioctl.h>
#include <linux/notifier.h>
#include <linux/file.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>

#include <linux/nsproxy.h>
#include <net/net_namespace.h>
#include <net/netns/generic.h>
#include <net/sock.h>
#include <net/gro.h>

#include <linux/uaccess.h>

#define PPPOE_HASH_BITS CONFIG_PPPOE_HASH_BITS
#define PPPOE_HASH_SIZE (1 << PPPOE_HASH_BITS)
#define PPPOE_HASH_MASK (PPPOE_HASH_SIZE - 1)

static int __pppoe_xmit(struct sock *sk, struct sk_buff *skb);

static const struct proto_ops pppoe_ops;
static const struct ppp_channel_ops pppoe_chan_ops;

/* per-net private data for this module */
static unsigned int pppoe_net_id __read_mostly;
struct pppoe_net {
        /*
         * we could use _single_ hash table for all
         * nets by injecting net id into the hash but
         * it would increase hash chains and add
         * a few additional math comparisons messy
         * as well, moreover in case of SMP less locking
         * controversy here
         */
        struct pppox_sock __rcu *hash_table[PPPOE_HASH_SIZE];
        spinlock_t hash_lock;
};

/*
 * PPPoE could be in the following stages:
 * 1) Discovery stage (to obtain remote MAC and Session ID)
 * 2) Session stage (MAC and SID are known)
 *
 * Ethernet frames have a special tag for this but
 * we use simpler approach based on session id
 */
static inline bool stage_session(__be16 sid)
{
        return sid != 0;
}

static inline struct pppoe_net *pppoe_pernet(struct net *net)
{
        return net_generic(net, pppoe_net_id);
}

static inline int cmp_2_addr(struct pppoe_addr *a, struct pppoe_addr *b)
{
        return a->sid == b->sid && ether_addr_equal(a->remote, b->remote);
}

static inline int cmp_addr(struct pppoe_addr *a, __be16 sid, char *addr)
{
        return a->sid == sid && ether_addr_equal(a->remote, addr);
}

#if 8 % PPPOE_HASH_BITS
#error 8 must be a multiple of PPPOE_HASH_BITS
#endif

static u8 hash_item(__be16 sid, const u8 addr[ETH_ALEN])
{
        const u16 *addr16 = (const u16 *)addr;
        unsigned int i;
        u16 hash16;
        u8 hash;

        hash16 = addr16[0] ^ addr16[1] ^ addr16[2] ^ (__force u16)sid;
        hash = (hash16 >> 8) ^ hash16;
        for (i = 8; (i >>= 1) >= PPPOE_HASH_BITS;)
                hash ^= hash >> i;

        return hash & PPPOE_HASH_MASK;
}

/**********************************************************************
 *
 *  Set/get/delete/rehash items  (internal versions)
 *
 **********************************************************************/
static struct pppox_sock *__get_item(struct pppoe_net *pn, __be16 sid,
                                unsigned char *addr, int ifindex)
{
        int hash = hash_item(sid, addr);
        struct pppox_sock *ret;

        ret = rcu_dereference(pn->hash_table[hash]);
        while (ret) {
                if (cmp_addr(&ret->pppoe_pa, sid, addr) &&
                    ret->pppoe_ifindex == ifindex)
                        return ret;

                ret = rcu_dereference(ret->next);
        }

        return NULL;
}

static int __set_item(struct pppoe_net *pn, struct pppox_sock *po)
{
        int hash = hash_item(po->pppoe_pa.sid, po->pppoe_pa.remote);
        struct pppox_sock *ret, *first;

        first = rcu_dereference_protected(pn->hash_table[hash], lockdep_is_held(&pn->hash_lock));
        ret = first;
        while (ret) {
                if (cmp_2_addr(&ret->pppoe_pa, &po->pppoe_pa) &&
                    ret->pppoe_ifindex == po->pppoe_ifindex)
                        return -EALREADY;

                ret = rcu_dereference_protected(ret->next, lockdep_is_held(&pn->hash_lock));
        }

        RCU_INIT_POINTER(po->next, first);
        rcu_assign_pointer(pn->hash_table[hash], po);

        return 0;
}

static void __delete_item(struct pppoe_net *pn, __be16 sid,
                                        char *addr, int ifindex)
{
        int hash = hash_item(sid, addr);
        struct pppox_sock *ret, __rcu **src;

        ret = rcu_dereference_protected(pn->hash_table[hash], lockdep_is_held(&pn->hash_lock));
        src = &pn->hash_table[hash];

        while (ret) {
                if (cmp_addr(&ret->pppoe_pa, sid, addr) &&
                    ret->pppoe_ifindex == ifindex) {
                        struct pppox_sock *next;

                        next = rcu_dereference_protected(ret->next,
                                                         lockdep_is_held(&pn->hash_lock));
                        rcu_assign_pointer(*src, next);
                        break;
                }

                src = &ret->next;
                ret = rcu_dereference_protected(ret->next, lockdep_is_held(&pn->hash_lock));
        }
}

/**********************************************************************
 *
 *  Set/get/delete/rehash items
 *
 **********************************************************************/
static inline struct pppox_sock *get_item(struct pppoe_net *pn, __be16 sid,
                                        unsigned char *addr, int ifindex)
{
        struct pppox_sock *po;

        po = __get_item(pn, sid, addr, ifindex);
        if (po && !refcount_inc_not_zero(&po->sk.sk_refcnt))
                po = NULL;

        return po;
}

static inline void delete_item(struct pppoe_net *pn, __be16 sid,
                                        char *addr, int ifindex)
{
        spin_lock(&pn->hash_lock);
        __delete_item(pn, sid, addr, ifindex);
        spin_unlock(&pn->hash_lock);
}

/***************************************************************************
 *
 *  Handler for device events.
 *  Certain device events require that sockets be unconnected.
 *
 **************************************************************************/

static void pppoe_flush_dev(struct net_device *dev)
{
        struct pppoe_net *pn;
        int i;

        pn = pppoe_pernet(dev_net(dev));
        spin_lock(&pn->hash_lock);
        for (i = 0; i < PPPOE_HASH_SIZE; i++) {
                struct pppox_sock *po = rcu_dereference_protected(pn->hash_table[i],
                                                                  lockdep_is_held(&pn->hash_lock));
                struct sock *sk;

                while (po) {
                        while (po && po->pppoe_dev != dev) {
                                po = rcu_dereference_protected(po->next,
                                                               lockdep_is_held(&pn->hash_lock));
                        }

                        if (!po)
                                break;

                        sk = &po->sk;

                        /* We always grab the socket lock, followed by the
                         * hash_lock, in that order.  Since we should hold the
                         * sock lock while doing any unbinding, we need to
                         * release the lock we're holding.  Hold a reference to
                         * the sock so it doesn't disappear as we're jumping
                         * between locks.
                         */

                        sock_hold(sk);
                        spin_unlock(&pn->hash_lock);
                        lock_sock(sk);

                        if (po->pppoe_dev == dev &&
                            sk->sk_state & (PPPOX_CONNECTED | PPPOX_BOUND)) {
                                pppox_unbind_sock(sk);
                                sk->sk_state_change(sk);
                                po->pppoe_dev = NULL;
                                dev_put(dev);
                        }

                        release_sock(sk);
                        sock_put(sk);

                        /* Restart the process from the start of the current
                         * hash chain. We dropped locks so the world may have
                         * change from underneath us.
                         */

                        BUG_ON(pppoe_pernet(dev_net(dev)) == NULL);
                        spin_lock(&pn->hash_lock);
                        po = rcu_dereference_protected(pn->hash_table[i],
                                                       lockdep_is_held(&pn->hash_lock));
                }
        }
        spin_unlock(&pn->hash_lock);
}

static int pppoe_device_event(struct notifier_block *this,
                              unsigned long event, void *ptr)
{
        struct net_device *dev = netdev_notifier_info_to_dev(ptr);

        /* Only look at sockets that are using this specific device. */
        switch (event) {
        case NETDEV_CHANGEADDR:
        case NETDEV_CHANGEMTU:
                /* A change in mtu or address is a bad thing, requiring
                 * LCP re-negotiation.
                 */

        case NETDEV_GOING_DOWN:
        case NETDEV_DOWN:
                /* Find every socket on this device and kill it. */
                pppoe_flush_dev(dev);
                break;

        default:
                break;
        }

        return NOTIFY_DONE;
}

static struct notifier_block pppoe_notifier = {
        .notifier_call = pppoe_device_event,
};

/************************************************************************
 *
 * Do the real work of receiving a PPPoE Session frame.
 *
 ***********************************************************************/
static int pppoe_rcv_core(struct sock *sk, struct sk_buff *skb)
{
        struct pppox_sock *po = pppox_sk(sk);

        /* Backlog receive. Semantics of backlog rcv preclude any code from
         * executing in lock_sock()/release_sock() bounds; meaning sk->sk_state
         * can't change.
         */

        if (sk->sk_state & PPPOX_BOUND) {
                ppp_input(&po->chan, skb);
        } else {
                if (sock_queue_rcv_skb(sk, skb))
                        goto abort_kfree;
        }

        return NET_RX_SUCCESS;

abort_kfree:
        kfree_skb(skb);
        return NET_RX_DROP;
}

/************************************************************************
 *
 * Receive wrapper called in BH context.
 *
 ***********************************************************************/
static int pppoe_rcv(struct sk_buff *skb, struct net_device *dev,
                     struct packet_type *pt, struct net_device *orig_dev)
{
        struct pppoe_hdr *ph;
        struct pppox_sock *po;
        struct pppoe_net *pn;
        int len;

        if (skb->pkt_type == PACKET_OTHERHOST)
                goto drop;

        skb = skb_share_check(skb, GFP_ATOMIC);
        if (!skb)
                goto out;

        if (skb_mac_header_len(skb) < ETH_HLEN)
                goto drop;

        if (!pskb_may_pull(skb, PPPOE_SES_HLEN))
                goto drop;

        ph = pppoe_hdr(skb);
        len = ntohs(ph->length);

        skb_pull_rcsum(skb, sizeof(*ph));
        if (skb->len < len)
                goto drop;

        /* skb->data points to the PPP protocol header after skb_pull_rcsum.
         * Drop PFC frames.
         */
        if (ppp_skb_is_compressed_proto(skb))
                goto drop;

        if (!skb_is_gso(skb) && pskb_trim_rcsum(skb, len))
                goto drop;

        ph = pppoe_hdr(skb);
        pn = pppoe_pernet(dev_net(dev));

        po = __get_item(pn, ph->sid, eth_hdr(skb)->h_source, dev->ifindex);
        if (!po)
                goto drop;

        return __sk_receive_skb(&po->sk, skb, 0, 1, false);

drop:
        kfree_skb(skb);
out:
        return NET_RX_DROP;
}

static void pppoe_unbind_sock_work(struct work_struct *work)
{
        struct pppox_sock *po = container_of(work, struct pppox_sock,
                                             proto.pppoe.padt_work);
        struct sock *sk = &po->sk;

        lock_sock(sk);
        if (po->pppoe_dev) {
                dev_put(po->pppoe_dev);
                po->pppoe_dev = NULL;
        }
        pppox_unbind_sock(sk);
        release_sock(sk);
        sock_put(sk);
}

/************************************************************************
 *
 * Receive a PPPoE Discovery frame.
 * This is solely for detection of PADT frames
 *
 ***********************************************************************/
static int pppoe_disc_rcv(struct sk_buff *skb, struct net_device *dev,
                          struct packet_type *pt, struct net_device *orig_dev)

{
        struct pppoe_hdr *ph;
        struct pppox_sock *po;
        struct pppoe_net *pn;

        skb = skb_share_check(skb, GFP_ATOMIC);
        if (!skb)
                goto out;

        if (skb->pkt_type != PACKET_HOST)
                goto abort;

        if (!pskb_may_pull(skb, sizeof(struct pppoe_hdr)))
                goto abort;

        ph = pppoe_hdr(skb);
        if (ph->code != PADT_CODE)
                goto abort;

        pn = pppoe_pernet(dev_net(dev));
        po = get_item(pn, ph->sid, eth_hdr(skb)->h_source, dev->ifindex);
        if (po)
                if (!schedule_work(&po->proto.pppoe.padt_work))
                        sock_put(&po->sk);

abort:
        kfree_skb(skb);
out:
        return NET_RX_SUCCESS; /* Lies... :-) */
}

static struct packet_type pppoes_ptype __read_mostly = {
        .type   = cpu_to_be16(ETH_P_PPP_SES),
        .func   = pppoe_rcv,
};

static struct packet_type pppoed_ptype __read_mostly = {
        .type   = cpu_to_be16(ETH_P_PPP_DISC),
        .func   = pppoe_disc_rcv,
};

static struct proto pppoe_sk_proto __read_mostly = {
        .name     = "PPPOE",
        .owner    = THIS_MODULE,
        .obj_size = sizeof(struct pppox_sock),
};

static void pppoe_destruct(struct sock *sk)
{
        skb_queue_purge(&sk->sk_receive_queue);
}

/***********************************************************************
 *
 * Initialize a new struct sock.
 *
 **********************************************************************/
static int pppoe_create(struct net *net, struct socket *sock, int kern)
{
        struct sock *sk;

        sk = sk_alloc(net, PF_PPPOX, GFP_KERNEL, &pppoe_sk_proto, kern);
        if (!sk)
                return -ENOMEM;

        sock_init_data(sock, sk);
        sock_set_flag(sk, SOCK_RCU_FREE);

        sock->state     = SS_UNCONNECTED;
        sock->ops       = &pppoe_ops;

        sk->sk_backlog_rcv      = pppoe_rcv_core;
        sk->sk_destruct         = pppoe_destruct;
        sk->sk_state            = PPPOX_NONE;
        sk->sk_type             = SOCK_STREAM;
        sk->sk_family           = PF_PPPOX;
        sk->sk_protocol         = PX_PROTO_OE;

        INIT_WORK(&pppox_sk(sk)->proto.pppoe.padt_work,
                  pppoe_unbind_sock_work);

        return 0;
}

static int pppoe_release(struct socket *sock)
{
        struct sock *sk = sock->sk;
        struct pppox_sock *po;
        struct pppoe_net *pn;
        struct net *net = NULL;

        if (!sk)
                return 0;

        lock_sock(sk);
        if (sock_flag(sk, SOCK_DEAD)) {
                release_sock(sk);
                return -EBADF;
        }

        po = pppox_sk(sk);

        if (po->pppoe_dev) {
                dev_put(po->pppoe_dev);
                po->pppoe_dev = NULL;
        }

        pppox_unbind_sock(sk);

        /* Signal the death of the socket. */
        sk->sk_state = PPPOX_DEAD;

        net = sock_net(sk);
        pn = pppoe_pernet(net);

        /*
         * protect "po" from concurrent updates
         * on pppoe_flush_dev
         */
        delete_item(pn, po->pppoe_pa.sid, po->pppoe_pa.remote,
                    po->pppoe_ifindex);

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

        release_sock(sk);
        sock_put(sk);

        return 0;
}

static int pppoe_connect(struct socket *sock, struct sockaddr_unsized *uservaddr,
                         int sockaddr_len, int flags)
{
        struct sock *sk = sock->sk;
        struct sockaddr_pppox *sp = (struct sockaddr_pppox *)uservaddr;
        struct pppox_sock *po = pppox_sk(sk);
        struct net_device *dev = NULL;
        struct pppoe_net *pn;
        struct net *net = NULL;
        int error;

        lock_sock(sk);

        error = -EINVAL;

        if (sockaddr_len != sizeof(struct sockaddr_pppox))
                goto end;

        if (sp->sa_protocol != PX_PROTO_OE)
                goto end;

        /* Check for already bound sockets */
        error = -EBUSY;
        if ((sk->sk_state & PPPOX_CONNECTED) &&
             stage_session(sp->sa_addr.pppoe.sid))
                goto end;

        /* Check for already disconnected sockets, on attempts to disconnect */
        error = -EALREADY;
        if ((sk->sk_state & PPPOX_DEAD) &&
             !stage_session(sp->sa_addr.pppoe.sid))
                goto end;

        error = 0;

        /* Delete the old binding */
        if (stage_session(po->pppoe_pa.sid)) {
                pppox_unbind_sock(sk);
                pn = pppoe_pernet(sock_net(sk));
                delete_item(pn, po->pppoe_pa.sid,
                            po->pppoe_pa.remote, po->pppoe_ifindex);
                if (po->pppoe_dev) {
                        dev_put(po->pppoe_dev);
                        po->pppoe_dev = NULL;
                }

                po->pppoe_ifindex = 0;
                memset(&po->pppoe_pa, 0, sizeof(po->pppoe_pa));
                memset(&po->chan, 0, sizeof(po->chan));
                po->next = NULL;
                po->num = 0;

                sk->sk_state = PPPOX_NONE;
        }

        /* Re-bind in session stage only */
        if (stage_session(sp->sa_addr.pppoe.sid)) {
                error = -ENODEV;
                net = sock_net(sk);
                dev = dev_get_by_name(net, sp->sa_addr.pppoe.dev);
                if (!dev)
                        goto err_put;

                po->pppoe_dev = dev;
                po->pppoe_ifindex = dev->ifindex;
                pn = pppoe_pernet(net);
                if (!(dev->flags & IFF_UP)) {
                        goto err_put;
                }

                memcpy(&po->pppoe_pa,
                       &sp->sa_addr.pppoe,
                       sizeof(struct pppoe_addr));

                spin_lock(&pn->hash_lock);
                error = __set_item(pn, po);
                spin_unlock(&pn->hash_lock);
                if (error < 0)
                        goto err_put;

                po->chan.hdrlen = (sizeof(struct pppoe_hdr) +
                                   dev->hard_header_len);

                po->chan.mtu = dev->mtu - sizeof(struct pppoe_hdr) - 2;
                po->chan.private = sk;
                po->chan.ops = &pppoe_chan_ops;
                po->chan.direct_xmit = true;

                error = ppp_register_net_channel(dev_net(dev), &po->chan);
                if (error) {
                        delete_item(pn, po->pppoe_pa.sid,
                                    po->pppoe_pa.remote, po->pppoe_ifindex);
                        goto err_put;
                }

                sk->sk_state = PPPOX_CONNECTED;
        }

        po->num = sp->sa_addr.pppoe.sid;

end:
        release_sock(sk);
        return error;
err_put:
        if (po->pppoe_dev) {
                dev_put(po->pppoe_dev);
                po->pppoe_dev = NULL;
        }
        goto end;
}

static int pppoe_getname(struct socket *sock, struct sockaddr *uaddr,
                  int peer)
{
        int len = sizeof(struct sockaddr_pppox);
        struct sockaddr_pppox sp;

        sp.sa_family    = AF_PPPOX;
        sp.sa_protocol  = PX_PROTO_OE;
        memcpy(&sp.sa_addr.pppoe, &pppox_sk(sock->sk)->pppoe_pa,
               sizeof(struct pppoe_addr));

        memcpy(uaddr, &sp, len);

        return len;
}

static int pppoe_ioctl(struct socket *sock, unsigned int cmd,
                unsigned long arg)
{
        struct sock *sk = sock->sk;
        struct pppox_sock *po = pppox_sk(sk);
        int val;
        int err;

        switch (cmd) {
        case PPPIOCGMRU:
                err = -ENXIO;
                if (!(sk->sk_state & PPPOX_CONNECTED))
                        break;

                err = -EFAULT;
                if (put_user(po->pppoe_dev->mtu -
                             sizeof(struct pppoe_hdr) -
                             PPP_HDRLEN,
                             (int __user *)arg))
                        break;
                err = 0;
                break;

        case PPPIOCSMRU:
                err = -ENXIO;
                if (!(sk->sk_state & PPPOX_CONNECTED))
                        break;

                err = -EFAULT;
                if (get_user(val, (int __user *)arg))
                        break;

                if (val < (po->pppoe_dev->mtu
                           - sizeof(struct pppoe_hdr)
                           - PPP_HDRLEN))
                        err = 0;
                else
                        err = -EINVAL;
                break;

        case PPPIOCSFLAGS:
                err = -EFAULT;
                if (get_user(val, (int __user *)arg))
                        break;
                err = 0;
                break;

        default:
                err = -ENOTTY;
        }

        return err;
}

static int pppoe_sendmsg(struct socket *sock, struct msghdr *m,
                         size_t total_len)
{
        struct sk_buff *skb;
        struct sock *sk = sock->sk;
        struct pppox_sock *po = pppox_sk(sk);
        int error;
        struct pppoe_hdr hdr;
        struct pppoe_hdr *ph;
        struct net_device *dev;
        char *start;
        int hlen;

        lock_sock(sk);
        if (sock_flag(sk, SOCK_DEAD) || !(sk->sk_state & PPPOX_CONNECTED)) {
                error = -ENOTCONN;
                goto end;
        }

        hdr.ver = 1;
        hdr.type = 1;
        hdr.code = 0;
        hdr.sid = po->num;

        dev = po->pppoe_dev;

        error = -EMSGSIZE;
        if (total_len > (dev->mtu + dev->hard_header_len))
                goto end;

        hlen = LL_RESERVED_SPACE(dev);
        skb = sock_wmalloc(sk, hlen + sizeof(*ph) + total_len +
                           dev->needed_tailroom, 0, GFP_KERNEL);
        if (!skb) {
                error = -ENOMEM;
                goto end;
        }

        /* Reserve space for headers. */
        skb_reserve(skb, hlen);
        skb_reset_network_header(skb);

        skb->dev = dev;

        skb->priority = READ_ONCE(sk->sk_priority);
        skb->protocol = cpu_to_be16(ETH_P_PPP_SES);

        ph = skb_put(skb, total_len + sizeof(struct pppoe_hdr));
        start = (char *)ph + sizeof(*ph);

        error = memcpy_from_msg(start, m, total_len);
        if (error < 0) {
                kfree_skb(skb);
                goto end;
        }

        error = total_len;
        dev_hard_header(skb, dev, ETH_P_PPP_SES,
                        po->pppoe_pa.remote, NULL, total_len);

        ph = pppoe_hdr(skb);
        memcpy(ph, &hdr, sizeof(struct pppoe_hdr));

        ph->length = htons(total_len);

        dev_queue_xmit(skb);

end:
        release_sock(sk);
        return error;
}

/************************************************************************
 *
 * xmit function for internal use.
 *
 ***********************************************************************/
static int __pppoe_xmit(struct sock *sk, struct sk_buff *skb)
{
        struct pppox_sock *po = pppox_sk(sk);
        struct net_device *dev = po->pppoe_dev;
        struct pppoe_hdr *ph;
        int data_len = skb->len;

        /* The higher-level PPP code (ppp_unregister_channel()) ensures the PPP
         * xmit operations conclude prior to an unregistration call.  Thus
         * sk->sk_state cannot change, so we don't need to do lock_sock().
         * But, we also can't do a lock_sock since that introduces a potential
         * deadlock as we'd reverse the lock ordering used when calling
         * ppp_unregister_channel().
         */

        if (sock_flag(sk, SOCK_DEAD) || !(sk->sk_state & PPPOX_CONNECTED))
                goto abort;

        if (!dev)
                goto abort;

        /* Copy the data if there is no space for the header or if it's
         * read-only.
         */
        if (skb_cow_head(skb, LL_RESERVED_SPACE(dev) + sizeof(*ph)))
                goto abort;

        __skb_push(skb, sizeof(*ph));
        skb_reset_network_header(skb);

        ph = pppoe_hdr(skb);
        ph->ver = 1;
        ph->type = 1;
        ph->code = 0;
        ph->sid = po->num;
        ph->length = htons(data_len);

        skb->protocol = cpu_to_be16(ETH_P_PPP_SES);
        skb->dev = dev;

        dev_hard_header(skb, dev, ETH_P_PPP_SES,
                        po->pppoe_pa.remote, NULL, data_len);

        dev_queue_xmit(skb);
        return 1;

abort:
        kfree_skb(skb);
        return 1;
}

/************************************************************************
 *
 * xmit function called by generic PPP driver
 * sends PPP frame over PPPoE socket
 *
 ***********************************************************************/
static int pppoe_xmit(struct ppp_channel *chan, struct sk_buff *skb)
{
        struct sock *sk = chan->private;
        return __pppoe_xmit(sk, skb);
}

static int pppoe_fill_forward_path(struct net_device_path_ctx *ctx,
                                   struct net_device_path *path,
                                   const struct ppp_channel *chan)
{
        struct sock *sk = chan->private;
        struct pppox_sock *po = pppox_sk(sk);
        struct net_device *dev = po->pppoe_dev;

        if (sock_flag(sk, SOCK_DEAD) ||
            !(sk->sk_state & PPPOX_CONNECTED) || !dev)
                return -1;

        path->type = DEV_PATH_PPPOE;
        path->encap.proto = htons(ETH_P_PPP_SES);
        path->encap.id = be16_to_cpu(po->num);
        memcpy(path->encap.h_dest, po->pppoe_pa.remote, ETH_ALEN);
        memcpy(ctx->daddr, po->pppoe_pa.remote, ETH_ALEN);
        path->dev = ctx->dev;
        ctx->dev = dev;

        return 0;
}

static const struct ppp_channel_ops pppoe_chan_ops = {
        .start_xmit = pppoe_xmit,
        .fill_forward_path = pppoe_fill_forward_path,
};

static int pppoe_recvmsg(struct socket *sock, struct msghdr *m,
                         size_t total_len, int flags)
{
        struct sock *sk = sock->sk;
        struct sk_buff *skb;
        int error = 0;

        if (sk->sk_state & PPPOX_BOUND)
                return -EIO;

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

        total_len = min_t(size_t, total_len, skb->len);
        error = skb_copy_datagram_msg(skb, 0, m, total_len);
        if (error == 0) {
                consume_skb(skb);
                return total_len;
        }

        kfree_skb(skb);
        return error;
}

#ifdef CONFIG_PROC_FS
static int pppoe_seq_show(struct seq_file *seq, void *v)
{
        struct pppox_sock *po;
        char *dev_name;

        if (v == SEQ_START_TOKEN) {
                seq_puts(seq, "Id       Address              Device\n");
                goto out;
        }

        po = v;
        dev_name = po->pppoe_pa.dev;

        seq_printf(seq, "%08X %pM %8s\n",
                po->pppoe_pa.sid, po->pppoe_pa.remote, dev_name);
out:
        return 0;
}

static inline struct pppox_sock *pppoe_get_idx(struct pppoe_net *pn, loff_t pos)
{
        struct pppox_sock *po;
        int i;

        for (i = 0; i < PPPOE_HASH_SIZE; i++) {
                po = rcu_dereference(pn->hash_table[i]);
                while (po) {
                        if (!pos--)
                                goto out;
                        po = rcu_dereference(po->next);
                }
        }

out:
        return po;
}

static void *pppoe_seq_start(struct seq_file *seq, loff_t *pos)
        __acquires(RCU)
{
        struct pppoe_net *pn = pppoe_pernet(seq_file_net(seq));
        loff_t l = *pos;

        rcu_read_lock();
        return l ? pppoe_get_idx(pn, --l) : SEQ_START_TOKEN;
}

static void *pppoe_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
        struct pppoe_net *pn = pppoe_pernet(seq_file_net(seq));
        struct pppox_sock *po, *next;

        ++*pos;
        if (v == SEQ_START_TOKEN) {
                po = pppoe_get_idx(pn, 0);
                goto out;
        }
        po = v;
        next = rcu_dereference(po->next);
        if (next)
                po = next;
        else {
                int hash = hash_item(po->pppoe_pa.sid, po->pppoe_pa.remote);

                po = NULL;
                while (++hash < PPPOE_HASH_SIZE) {
                        po = rcu_dereference(pn->hash_table[hash]);
                        if (po)
                                break;
                }
        }

out:
        return po;
}

static void pppoe_seq_stop(struct seq_file *seq, void *v)
        __releases(RCU)
{
        rcu_read_unlock();
}

static const struct seq_operations pppoe_seq_ops = {
        .start          = pppoe_seq_start,
        .next           = pppoe_seq_next,
        .stop           = pppoe_seq_stop,
        .show           = pppoe_seq_show,
};
#endif /* CONFIG_PROC_FS */

static const struct proto_ops pppoe_ops = {
        .family         = AF_PPPOX,
        .owner          = THIS_MODULE,
        .release        = pppoe_release,
        .bind           = sock_no_bind,
        .connect        = pppoe_connect,
        .socketpair     = sock_no_socketpair,
        .accept         = sock_no_accept,
        .getname        = pppoe_getname,
        .poll           = datagram_poll,
        .listen         = sock_no_listen,
        .shutdown       = sock_no_shutdown,
        .sendmsg        = pppoe_sendmsg,
        .recvmsg        = pppoe_recvmsg,
        .mmap           = sock_no_mmap,
        .ioctl          = pppox_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl   = pppox_compat_ioctl,
#endif
};

static const struct pppox_proto pppoe_proto = {
        .create = pppoe_create,
        .ioctl  = pppoe_ioctl,
        .owner  = THIS_MODULE,
};

static __net_init int pppoe_init_net(struct net *net)
{
        struct pppoe_net *pn = pppoe_pernet(net);
        struct proc_dir_entry *pde;

        spin_lock_init(&pn->hash_lock);

        pde = proc_create_net("pppoe", 0444, net->proc_net,
                        &pppoe_seq_ops, sizeof(struct seq_net_private));
#ifdef CONFIG_PROC_FS
        if (!pde)
                return -ENOMEM;
#endif

        return 0;
}

static __net_exit void pppoe_exit_net(struct net *net)
{
        remove_proc_entry("pppoe", net->proc_net);
}

static struct pernet_operations pppoe_net_ops = {
        .init = pppoe_init_net,
        .exit = pppoe_exit_net,
        .id   = &pppoe_net_id,
        .size = sizeof(struct pppoe_net),
};

static u16
compare_pppoe_header(const struct pppoe_hdr *phdr,
                     const struct pppoe_hdr *phdr2)
{
        __be16 proto = *(const __be16 *)(phdr + 1);
        __be16 proto2 = *(const __be16 *)(phdr2 + 1);

        return (__force u16)((phdr->sid ^ phdr2->sid) | (proto ^ proto2));
}

static __be16 pppoe_hdr_proto(const struct pppoe_hdr *phdr)
{
        __be16 proto = *(const __be16 *)(phdr + 1);

        switch (proto) {
        case cpu_to_be16(PPP_IP):
                return cpu_to_be16(ETH_P_IP);
#if IS_ENABLED(CONFIG_IPV6)
        case cpu_to_be16(PPP_IPV6):
                return cpu_to_be16(ETH_P_IPV6);
#endif
        default:
                return 0;
        }
}

static struct sk_buff *pppoe_gro_receive(struct list_head *head,
                                         struct sk_buff *skb)
{
        const struct packet_offload *ptype;
        unsigned int hlen, off_pppoe;
        const struct pppoe_hdr *phdr;
        struct sk_buff *pp = NULL;
        struct sk_buff *p;
        int flush = 1;
        __be16 type;

        off_pppoe = skb_gro_offset(skb);
        hlen = off_pppoe + PPPOE_SES_HLEN;
        phdr = skb_gro_header(skb, hlen, off_pppoe);
        if (unlikely(!phdr))
                goto out;

        /* filter for session packets (type:1, ver:1, code:0) */
        if (*(const __be16 *)phdr != cpu_to_be16(0x1100))
                goto out;

        /* ignore packets with padding or invalid length */
        if (skb_gro_len(skb) != be16_to_cpu(phdr->length) + sizeof(*phdr))
                goto out;

        type = pppoe_hdr_proto(phdr);
        ptype = gro_find_receive_by_type(type);
        if (!ptype)
                goto out;

        flush = 0;

        list_for_each_entry(p, head, list) {
                const struct pppoe_hdr *phdr2;

                if (!NAPI_GRO_CB(p)->same_flow)
                        continue;

                phdr2 = (const struct pppoe_hdr *)(p->data + off_pppoe);
                if (compare_pppoe_header(phdr, phdr2))
                        NAPI_GRO_CB(p)->same_flow = 0;
        }

        skb_gro_pull(skb, PPPOE_SES_HLEN);
        skb_gro_postpull_rcsum(skb, phdr, PPPOE_SES_HLEN);

        pp = indirect_call_gro_receive_inet(ptype->callbacks.gro_receive,
                                            ipv6_gro_receive, inet_gro_receive,
                                            head, skb);

out:
        skb_gro_flush_final(skb, pp, flush);

        return pp;
}

static int pppoe_gro_complete(struct sk_buff *skb, int nhoff)
{
        struct pppoe_hdr *phdr = (struct pppoe_hdr *)(skb->data + nhoff);
        __be16 type = pppoe_hdr_proto(phdr);
        struct packet_offload *ptype;
        unsigned int len;

        ptype = gro_find_complete_by_type(type);
        if (!ptype)
                return -ENOENT;

        len = skb->len - (nhoff + sizeof(*phdr));
        len = min(len, 0xFFFFU);
        phdr->length = cpu_to_be16(len);

        return INDIRECT_CALL_INET(ptype->callbacks.gro_complete,
                                  ipv6_gro_complete, inet_gro_complete,
                                  skb, nhoff + PPPOE_SES_HLEN);
}

static struct sk_buff *pppoe_gso_segment(struct sk_buff *skb,
                                         netdev_features_t features)
{
        struct sk_buff *segs = ERR_PTR(-EINVAL);
        struct packet_offload *ptype;
        struct pppoe_hdr *phdr;
        __be16 orig_type, type;
        int len, nhoff;

        skb_reset_network_header(skb);
        nhoff = skb_network_header(skb) - skb_mac_header(skb);

        if (unlikely(!pskb_may_pull(skb, PPPOE_SES_HLEN)))
                goto out;

        phdr = (struct pppoe_hdr *)skb_network_header(skb);
        type = pppoe_hdr_proto(phdr);
        ptype = gro_find_complete_by_type(type);
        if (!ptype)
                goto out;

        orig_type = skb->protocol;
        __skb_pull(skb, PPPOE_SES_HLEN);
        features &= ~NETIF_F_GSO_SOFTWARE;
        segs = ptype->callbacks.gso_segment(skb, features);
        if (IS_ERR_OR_NULL(segs))
                goto out;

        skb = segs;
        do {
                phdr = (struct pppoe_hdr *)(skb_mac_header(skb) + nhoff);
                len = skb->len - (nhoff + sizeof(*phdr));
                phdr->length = cpu_to_be16(len);
                skb->network_header = (u8 *)phdr - skb->head;
                skb->protocol = orig_type;
                skb_reset_mac_len(skb);
        } while ((skb = skb->next));

out:
        return segs;
}

static struct packet_offload pppoe_packet_offload __read_mostly = {
        .type = cpu_to_be16(ETH_P_PPP_SES),
        .priority = 20,
        .callbacks = {
                .gro_receive = pppoe_gro_receive,
                .gro_complete = pppoe_gro_complete,
                .gso_segment = pppoe_gso_segment,
        },
};

static int __init pppoe_init(void)
{
        int err;

        err = register_pernet_device(&pppoe_net_ops);
        if (err)
                goto out;

        err = proto_register(&pppoe_sk_proto, 0);
        if (err)
                goto out_unregister_net_ops;

        err = register_pppox_proto(PX_PROTO_OE, &pppoe_proto);
        if (err)
                goto out_unregister_pppoe_proto;

        if (IS_ENABLED(CONFIG_INET))
                dev_add_offload(&pppoe_packet_offload);
        dev_add_pack(&pppoes_ptype);
        dev_add_pack(&pppoed_ptype);
        register_netdevice_notifier(&pppoe_notifier);

        return 0;

out_unregister_pppoe_proto:
        proto_unregister(&pppoe_sk_proto);
out_unregister_net_ops:
        unregister_pernet_device(&pppoe_net_ops);
out:
        return err;
}

static void __exit pppoe_exit(void)
{
        unregister_netdevice_notifier(&pppoe_notifier);
        dev_remove_pack(&pppoed_ptype);
        dev_remove_pack(&pppoes_ptype);
        if (IS_ENABLED(CONFIG_INET))
                dev_remove_offload(&pppoe_packet_offload);
        unregister_pppox_proto(PX_PROTO_OE);
        proto_unregister(&pppoe_sk_proto);
        unregister_pernet_device(&pppoe_net_ops);
}

module_init(pppoe_init);
module_exit(pppoe_exit);

MODULE_AUTHOR("Michal Ostrowski <mostrows@speakeasy.net>");
MODULE_DESCRIPTION("PPP over Ethernet driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS_NET_PF_PROTO(PF_PPPOX, PX_PROTO_OE);