root/net/l2tp/l2tp_netlink.c 
// SPDX-License-Identifier: GPL-2.0-only
/* L2TP netlink layer, for management
 *
 * Copyright (c) 2008,2009,2010 Katalix Systems Ltd
 *
 * Partly based on the IrDA nelink implementation
 * (see net/irda/irnetlink.c) which is:
 * Copyright (c) 2007 Samuel Ortiz <samuel@sortiz.org>
 * which is in turn partly based on the wireless netlink code:
 * Copyright 2006 Johannes Berg <johannes@sipsolutions.net>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <net/sock.h>
#include <net/genetlink.h>
#include <net/udp.h>
#include <linux/in.h>
#include <linux/udp.h>
#include <linux/socket.h>
#include <linux/module.h>
#include <linux/list.h>
#include <net/net_namespace.h>

#include <linux/l2tp.h>

#include "l2tp_core.h"

static struct genl_family l2tp_nl_family;

static const struct genl_multicast_group l2tp_multicast_group[] = {
        {
                .name = L2TP_GENL_MCGROUP,
        },
};

static int l2tp_nl_tunnel_send(struct sk_buff *skb, u32 portid, u32 seq,
                               int flags, struct l2tp_tunnel *tunnel, u8 cmd);
static int l2tp_nl_session_send(struct sk_buff *skb, u32 portid, u32 seq,
                                int flags, struct l2tp_session *session,
                                u8 cmd);

/* Accessed under genl lock */
static const struct l2tp_nl_cmd_ops *l2tp_nl_cmd_ops[__L2TP_PWTYPE_MAX];

static struct l2tp_session *l2tp_nl_session_get(struct genl_info *info)
{
        u32 tunnel_id;
        u32 session_id;
        char *ifname;
        struct l2tp_tunnel *tunnel;
        struct l2tp_session *session = NULL;
        struct net *net = genl_info_net(info);

        if (info->attrs[L2TP_ATTR_IFNAME]) {
                ifname = nla_data(info->attrs[L2TP_ATTR_IFNAME]);
                session = l2tp_session_get_by_ifname(net, ifname);
        } else if ((info->attrs[L2TP_ATTR_SESSION_ID]) &&
                   (info->attrs[L2TP_ATTR_CONN_ID])) {
                tunnel_id = nla_get_u32(info->attrs[L2TP_ATTR_CONN_ID]);
                session_id = nla_get_u32(info->attrs[L2TP_ATTR_SESSION_ID]);
                tunnel = l2tp_tunnel_get(net, tunnel_id);
                if (tunnel) {
                        session = l2tp_session_get(net, tunnel->sock, tunnel->version,
                                                   tunnel_id, session_id);
                        l2tp_tunnel_put(tunnel);
                }
        }

        return session;
}

static int l2tp_nl_cmd_noop(struct sk_buff *skb, struct genl_info *info)
{
        struct sk_buff *msg;
        void *hdr;
        int ret = -ENOBUFS;

        msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
        if (!msg) {
                ret = -ENOMEM;
                goto out;
        }

        hdr = genlmsg_put(msg, info->snd_portid, info->snd_seq,
                          &l2tp_nl_family, 0, L2TP_CMD_NOOP);
        if (!hdr) {
                ret = -EMSGSIZE;
                goto err_out;
        }

        genlmsg_end(msg, hdr);

        return genlmsg_unicast(genl_info_net(info), msg, info->snd_portid);

err_out:
        nlmsg_free(msg);

out:
        return ret;
}

static int l2tp_tunnel_notify(struct genl_family *family,
                              struct genl_info *info,
                              struct l2tp_tunnel *tunnel,
                              u8 cmd)
{
        struct sk_buff *msg;
        int ret;

        msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
        if (!msg)
                return -ENOMEM;

        ret = l2tp_nl_tunnel_send(msg, info->snd_portid, info->snd_seq,
                                  NLM_F_ACK, tunnel, cmd);

        if (ret >= 0) {
                ret = genlmsg_multicast_allns(family, msg, 0, 0);
                /* We don't care if no one is listening */
                if (ret == -ESRCH)
                        ret = 0;
                return ret;
        }

        nlmsg_free(msg);

        return ret;
}

static int l2tp_session_notify(struct genl_family *family,
                               struct genl_info *info,
                               struct l2tp_session *session,
                               u8 cmd)
{
        struct sk_buff *msg;
        int ret;

        msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
        if (!msg)
                return -ENOMEM;

        ret = l2tp_nl_session_send(msg, info->snd_portid, info->snd_seq,
                                   NLM_F_ACK, session, cmd);

        if (ret >= 0) {
                ret = genlmsg_multicast_allns(family, msg, 0, 0);
                /* We don't care if no one is listening */
                if (ret == -ESRCH)
                        ret = 0;
                return ret;
        }

        nlmsg_free(msg);

        return ret;
}

static int l2tp_nl_cmd_tunnel_create_get_addr(struct nlattr **attrs, struct l2tp_tunnel_cfg *cfg)
{
        if (attrs[L2TP_ATTR_UDP_SPORT])
                cfg->local_udp_port = nla_get_u16(attrs[L2TP_ATTR_UDP_SPORT]);
        if (attrs[L2TP_ATTR_UDP_DPORT])
                cfg->peer_udp_port = nla_get_u16(attrs[L2TP_ATTR_UDP_DPORT]);
        cfg->use_udp_checksums = nla_get_flag(attrs[L2TP_ATTR_UDP_CSUM]);

        /* Must have either AF_INET or AF_INET6 address for source and destination */
#if IS_ENABLED(CONFIG_IPV6)
        if (attrs[L2TP_ATTR_IP6_SADDR] && attrs[L2TP_ATTR_IP6_DADDR]) {
                cfg->local_ip6 = nla_data(attrs[L2TP_ATTR_IP6_SADDR]);
                cfg->peer_ip6 = nla_data(attrs[L2TP_ATTR_IP6_DADDR]);
                cfg->udp6_zero_tx_checksums = nla_get_flag(attrs[L2TP_ATTR_UDP_ZERO_CSUM6_TX]);
                cfg->udp6_zero_rx_checksums = nla_get_flag(attrs[L2TP_ATTR_UDP_ZERO_CSUM6_RX]);
                return 0;
        }
#endif
        if (attrs[L2TP_ATTR_IP_SADDR] && attrs[L2TP_ATTR_IP_DADDR]) {
                cfg->local_ip.s_addr = nla_get_in_addr(attrs[L2TP_ATTR_IP_SADDR]);
                cfg->peer_ip.s_addr = nla_get_in_addr(attrs[L2TP_ATTR_IP_DADDR]);
                return 0;
        }
        return -EINVAL;
}

static int l2tp_nl_cmd_tunnel_create(struct sk_buff *skb, struct genl_info *info)
{
        u32 tunnel_id;
        u32 peer_tunnel_id;
        int proto_version;
        int fd = -1;
        int ret = 0;
        struct l2tp_tunnel_cfg cfg = { 0, };
        struct l2tp_tunnel *tunnel;
        struct net *net = genl_info_net(info);
        struct nlattr **attrs = info->attrs;

        if (!attrs[L2TP_ATTR_CONN_ID]) {
                ret = -EINVAL;
                goto out;
        }
        tunnel_id = nla_get_u32(attrs[L2TP_ATTR_CONN_ID]);

        if (!attrs[L2TP_ATTR_PEER_CONN_ID]) {
                ret = -EINVAL;
                goto out;
        }
        peer_tunnel_id = nla_get_u32(attrs[L2TP_ATTR_PEER_CONN_ID]);

        if (!attrs[L2TP_ATTR_PROTO_VERSION]) {
                ret = -EINVAL;
                goto out;
        }
        proto_version = nla_get_u8(attrs[L2TP_ATTR_PROTO_VERSION]);

        if (!attrs[L2TP_ATTR_ENCAP_TYPE]) {
                ret = -EINVAL;
                goto out;
        }
        cfg.encap = nla_get_u16(attrs[L2TP_ATTR_ENCAP_TYPE]);

        /* Managed tunnels take the tunnel socket from userspace.
         * Unmanaged tunnels must call out the source and destination addresses
         * for the kernel to create the tunnel socket itself.
         */
        if (attrs[L2TP_ATTR_FD]) {
                fd = nla_get_u32(attrs[L2TP_ATTR_FD]);
        } else {
                ret = l2tp_nl_cmd_tunnel_create_get_addr(attrs, &cfg);
                if (ret < 0)
                        goto out;
        }

        ret = -EINVAL;
        switch (cfg.encap) {
        case L2TP_ENCAPTYPE_UDP:
        case L2TP_ENCAPTYPE_IP:
                ret = l2tp_tunnel_create(fd, proto_version, tunnel_id,
                                         peer_tunnel_id, &cfg, &tunnel);
                break;
        }

        if (ret < 0)
                goto out;

        refcount_inc(&tunnel->ref_count);
        ret = l2tp_tunnel_register(tunnel, net, &cfg);
        if (ret < 0) {
                kfree(tunnel);
                goto out;
        }
        ret = l2tp_tunnel_notify(&l2tp_nl_family, info, tunnel,
                                 L2TP_CMD_TUNNEL_CREATE);
        l2tp_tunnel_put(tunnel);

out:
        return ret;
}

static int l2tp_nl_cmd_tunnel_delete(struct sk_buff *skb, struct genl_info *info)
{
        struct l2tp_tunnel *tunnel;
        u32 tunnel_id;
        int ret = 0;
        struct net *net = genl_info_net(info);

        if (!info->attrs[L2TP_ATTR_CONN_ID]) {
                ret = -EINVAL;
                goto out;
        }
        tunnel_id = nla_get_u32(info->attrs[L2TP_ATTR_CONN_ID]);

        tunnel = l2tp_tunnel_get(net, tunnel_id);
        if (!tunnel) {
                ret = -ENODEV;
                goto out;
        }

        l2tp_tunnel_notify(&l2tp_nl_family, info,
                           tunnel, L2TP_CMD_TUNNEL_DELETE);

        l2tp_tunnel_delete(tunnel);

        l2tp_tunnel_put(tunnel);

out:
        return ret;
}

static int l2tp_nl_cmd_tunnel_modify(struct sk_buff *skb, struct genl_info *info)
{
        struct l2tp_tunnel *tunnel;
        u32 tunnel_id;
        int ret = 0;
        struct net *net = genl_info_net(info);

        if (!info->attrs[L2TP_ATTR_CONN_ID]) {
                ret = -EINVAL;
                goto out;
        }
        tunnel_id = nla_get_u32(info->attrs[L2TP_ATTR_CONN_ID]);

        tunnel = l2tp_tunnel_get(net, tunnel_id);
        if (!tunnel) {
                ret = -ENODEV;
                goto out;
        }

        ret = l2tp_tunnel_notify(&l2tp_nl_family, info,
                                 tunnel, L2TP_CMD_TUNNEL_MODIFY);

        l2tp_tunnel_put(tunnel);

out:
        return ret;
}

#if IS_ENABLED(CONFIG_IPV6)
static int l2tp_nl_tunnel_send_addr6(struct sk_buff *skb, struct sock *sk,
                                     enum l2tp_encap_type encap)
{
        struct inet_sock *inet = inet_sk(sk);
        struct ipv6_pinfo *np = inet6_sk(sk);

        switch (encap) {
        case L2TP_ENCAPTYPE_UDP:
                if (udp_get_no_check6_tx(sk) &&
                    nla_put_flag(skb, L2TP_ATTR_UDP_ZERO_CSUM6_TX))
                        return -1;
                if (udp_get_no_check6_rx(sk) &&
                    nla_put_flag(skb, L2TP_ATTR_UDP_ZERO_CSUM6_RX))
                        return -1;
                if (nla_put_u16(skb, L2TP_ATTR_UDP_SPORT, ntohs(inet->inet_sport)) ||
                    nla_put_u16(skb, L2TP_ATTR_UDP_DPORT, ntohs(inet->inet_dport)))
                        return -1;
                fallthrough;
        case L2TP_ENCAPTYPE_IP:
                if (nla_put_in6_addr(skb, L2TP_ATTR_IP6_SADDR, &np->saddr) ||
                    nla_put_in6_addr(skb, L2TP_ATTR_IP6_DADDR, &sk->sk_v6_daddr))
                        return -1;
                break;
        }
        return 0;
}
#endif

static int l2tp_nl_tunnel_send_addr4(struct sk_buff *skb, struct sock *sk,
                                     enum l2tp_encap_type encap)
{
        struct inet_sock *inet = inet_sk(sk);

        switch (encap) {
        case L2TP_ENCAPTYPE_UDP:
                if (nla_put_u8(skb, L2TP_ATTR_UDP_CSUM, !sk->sk_no_check_tx) ||
                    nla_put_u16(skb, L2TP_ATTR_UDP_SPORT, ntohs(inet->inet_sport)) ||
                    nla_put_u16(skb, L2TP_ATTR_UDP_DPORT, ntohs(inet->inet_dport)))
                        return -1;
                fallthrough;
        case L2TP_ENCAPTYPE_IP:
                if (nla_put_in_addr(skb, L2TP_ATTR_IP_SADDR, inet->inet_saddr) ||
                    nla_put_in_addr(skb, L2TP_ATTR_IP_DADDR, inet->inet_daddr))
                        return -1;
                break;
        }

        return 0;
}

/* Append attributes for the tunnel address, handling the different attribute types
 * used for different tunnel encapsulation and AF_INET v.s. AF_INET6.
 */
static int l2tp_nl_tunnel_send_addr(struct sk_buff *skb, struct l2tp_tunnel *tunnel)
{
        struct sock *sk = tunnel->sock;

        if (!sk)
                return 0;

#if IS_ENABLED(CONFIG_IPV6)
        if (sk->sk_family == AF_INET6)
                return l2tp_nl_tunnel_send_addr6(skb, sk, tunnel->encap);
#endif
        return l2tp_nl_tunnel_send_addr4(skb, sk, tunnel->encap);
}

static int l2tp_nl_tunnel_send(struct sk_buff *skb, u32 portid, u32 seq, int flags,
                               struct l2tp_tunnel *tunnel, u8 cmd)
{
        void *hdr;
        struct nlattr *nest;

        hdr = genlmsg_put(skb, portid, seq, &l2tp_nl_family, flags, cmd);
        if (!hdr)
                return -EMSGSIZE;

        if (nla_put_u8(skb, L2TP_ATTR_PROTO_VERSION, tunnel->version) ||
            nla_put_u32(skb, L2TP_ATTR_CONN_ID, tunnel->tunnel_id) ||
            nla_put_u32(skb, L2TP_ATTR_PEER_CONN_ID, tunnel->peer_tunnel_id) ||
            nla_put_u32(skb, L2TP_ATTR_DEBUG, 0) ||
            nla_put_u16(skb, L2TP_ATTR_ENCAP_TYPE, tunnel->encap))
                goto nla_put_failure;

        nest = nla_nest_start_noflag(skb, L2TP_ATTR_STATS);
        if (!nest)
                goto nla_put_failure;

        if (nla_put_u64_64bit(skb, L2TP_ATTR_TX_PACKETS,
                              atomic_long_read(&tunnel->stats.tx_packets),
                              L2TP_ATTR_STATS_PAD) ||
            nla_put_u64_64bit(skb, L2TP_ATTR_TX_BYTES,
                              atomic_long_read(&tunnel->stats.tx_bytes),
                              L2TP_ATTR_STATS_PAD) ||
            nla_put_u64_64bit(skb, L2TP_ATTR_TX_ERRORS,
                              atomic_long_read(&tunnel->stats.tx_errors),
                              L2TP_ATTR_STATS_PAD) ||
            nla_put_u64_64bit(skb, L2TP_ATTR_RX_PACKETS,
                              atomic_long_read(&tunnel->stats.rx_packets),
                              L2TP_ATTR_STATS_PAD) ||
            nla_put_u64_64bit(skb, L2TP_ATTR_RX_BYTES,
                              atomic_long_read(&tunnel->stats.rx_bytes),
                              L2TP_ATTR_STATS_PAD) ||
            nla_put_u64_64bit(skb, L2TP_ATTR_RX_SEQ_DISCARDS,
                              atomic_long_read(&tunnel->stats.rx_seq_discards),
                              L2TP_ATTR_STATS_PAD) ||
            nla_put_u64_64bit(skb, L2TP_ATTR_RX_COOKIE_DISCARDS,
                              atomic_long_read(&tunnel->stats.rx_cookie_discards),
                              L2TP_ATTR_STATS_PAD) ||
            nla_put_u64_64bit(skb, L2TP_ATTR_RX_OOS_PACKETS,
                              atomic_long_read(&tunnel->stats.rx_oos_packets),
                              L2TP_ATTR_STATS_PAD) ||
            nla_put_u64_64bit(skb, L2TP_ATTR_RX_ERRORS,
                              atomic_long_read(&tunnel->stats.rx_errors),
                              L2TP_ATTR_STATS_PAD) ||
            nla_put_u64_64bit(skb, L2TP_ATTR_RX_INVALID,
                              atomic_long_read(&tunnel->stats.rx_invalid),
                              L2TP_ATTR_STATS_PAD))
                goto nla_put_failure;
        nla_nest_end(skb, nest);

        if (l2tp_nl_tunnel_send_addr(skb, tunnel))
                goto nla_put_failure;

        genlmsg_end(skb, hdr);
        return 0;

nla_put_failure:
        genlmsg_cancel(skb, hdr);
        return -1;
}

static int l2tp_nl_cmd_tunnel_get(struct sk_buff *skb, struct genl_info *info)
{
        struct l2tp_tunnel *tunnel;
        struct sk_buff *msg;
        u32 tunnel_id;
        int ret = -ENOBUFS;
        struct net *net = genl_info_net(info);

        if (!info->attrs[L2TP_ATTR_CONN_ID]) {
                ret = -EINVAL;
                goto err;
        }

        tunnel_id = nla_get_u32(info->attrs[L2TP_ATTR_CONN_ID]);

        msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
        if (!msg) {
                ret = -ENOMEM;
                goto err;
        }

        tunnel = l2tp_tunnel_get(net, tunnel_id);
        if (!tunnel) {
                ret = -ENODEV;
                goto err_nlmsg;
        }

        ret = l2tp_nl_tunnel_send(msg, info->snd_portid, info->snd_seq,
                                  NLM_F_ACK, tunnel, L2TP_CMD_TUNNEL_GET);
        if (ret < 0)
                goto err_nlmsg_tunnel;

        l2tp_tunnel_put(tunnel);

        return genlmsg_unicast(net, msg, info->snd_portid);

err_nlmsg_tunnel:
        l2tp_tunnel_put(tunnel);
err_nlmsg:
        nlmsg_free(msg);
err:
        return ret;
}

struct l2tp_nl_cb_data {
        unsigned long tkey;
        unsigned long skey;
};

static int l2tp_nl_cmd_tunnel_dump(struct sk_buff *skb, struct netlink_callback *cb)
{
        struct l2tp_nl_cb_data *cbd = (void *)&cb->ctx[0];
        unsigned long key = cbd->tkey;
        struct l2tp_tunnel *tunnel;
        struct net *net = sock_net(skb->sk);

        for (;;) {
                tunnel = l2tp_tunnel_get_next(net, &key);
                if (!tunnel)
                        goto out;

                if (l2tp_nl_tunnel_send(skb, NETLINK_CB(cb->skb).portid,
                                        cb->nlh->nlmsg_seq, NLM_F_MULTI,
                                        tunnel, L2TP_CMD_TUNNEL_GET) < 0) {
                        l2tp_tunnel_put(tunnel);
                        goto out;
                }
                l2tp_tunnel_put(tunnel);

                key++;
        }

out:
        cbd->tkey = key;

        return skb->len;
}

static int l2tp_nl_cmd_session_create(struct sk_buff *skb, struct genl_info *info)
{
        u32 tunnel_id = 0;
        u32 session_id;
        u32 peer_session_id;
        int ret = 0;
        struct l2tp_tunnel *tunnel;
        struct l2tp_session *session;
        struct l2tp_session_cfg cfg = { 0, };
        struct net *net = genl_info_net(info);

        if (!info->attrs[L2TP_ATTR_CONN_ID]) {
                ret = -EINVAL;
                goto out;
        }

        tunnel_id = nla_get_u32(info->attrs[L2TP_ATTR_CONN_ID]);
        tunnel = l2tp_tunnel_get(net, tunnel_id);
        if (!tunnel) {
                ret = -ENODEV;
                goto out;
        }

        if (!info->attrs[L2TP_ATTR_SESSION_ID]) {
                ret = -EINVAL;
                goto out_tunnel;
        }
        session_id = nla_get_u32(info->attrs[L2TP_ATTR_SESSION_ID]);

        if (!info->attrs[L2TP_ATTR_PEER_SESSION_ID]) {
                ret = -EINVAL;
                goto out_tunnel;
        }
        peer_session_id = nla_get_u32(info->attrs[L2TP_ATTR_PEER_SESSION_ID]);

        if (!info->attrs[L2TP_ATTR_PW_TYPE]) {
                ret = -EINVAL;
                goto out_tunnel;
        }
        cfg.pw_type = nla_get_u16(info->attrs[L2TP_ATTR_PW_TYPE]);
        if (cfg.pw_type >= __L2TP_PWTYPE_MAX) {
                ret = -EINVAL;
                goto out_tunnel;
        }

        /* L2TPv2 only accepts PPP pseudo-wires */
        if (tunnel->version == 2 && cfg.pw_type != L2TP_PWTYPE_PPP) {
                ret = -EPROTONOSUPPORT;
                goto out_tunnel;
        }

        if (tunnel->version > 2) {
                if (info->attrs[L2TP_ATTR_L2SPEC_TYPE]) {
                        cfg.l2specific_type = nla_get_u8(info->attrs[L2TP_ATTR_L2SPEC_TYPE]);
                        if (cfg.l2specific_type != L2TP_L2SPECTYPE_DEFAULT &&
                            cfg.l2specific_type != L2TP_L2SPECTYPE_NONE) {
                                ret = -EINVAL;
                                goto out_tunnel;
                        }
                } else {
                        cfg.l2specific_type = L2TP_L2SPECTYPE_DEFAULT;
                }

                if (info->attrs[L2TP_ATTR_COOKIE]) {
                        u16 len = nla_len(info->attrs[L2TP_ATTR_COOKIE]);

                        if (len > 8) {
                                ret = -EINVAL;
                                goto out_tunnel;
                        }
                        cfg.cookie_len = len;
                        memcpy(&cfg.cookie[0], nla_data(info->attrs[L2TP_ATTR_COOKIE]), len);
                }
                if (info->attrs[L2TP_ATTR_PEER_COOKIE]) {
                        u16 len = nla_len(info->attrs[L2TP_ATTR_PEER_COOKIE]);

                        if (len > 8) {
                                ret = -EINVAL;
                                goto out_tunnel;
                        }
                        cfg.peer_cookie_len = len;
                        memcpy(&cfg.peer_cookie[0], nla_data(info->attrs[L2TP_ATTR_PEER_COOKIE]), len);
                }
                if (info->attrs[L2TP_ATTR_IFNAME])
                        cfg.ifname = nla_data(info->attrs[L2TP_ATTR_IFNAME]);
        }

        if (info->attrs[L2TP_ATTR_RECV_SEQ])
                cfg.recv_seq = nla_get_u8(info->attrs[L2TP_ATTR_RECV_SEQ]);

        if (info->attrs[L2TP_ATTR_SEND_SEQ])
                cfg.send_seq = nla_get_u8(info->attrs[L2TP_ATTR_SEND_SEQ]);

        if (info->attrs[L2TP_ATTR_LNS_MODE])
                cfg.lns_mode = nla_get_u8(info->attrs[L2TP_ATTR_LNS_MODE]);

        if (info->attrs[L2TP_ATTR_RECV_TIMEOUT])
                cfg.reorder_timeout = nla_get_msecs(info->attrs[L2TP_ATTR_RECV_TIMEOUT]);

#ifdef CONFIG_MODULES
        if (!l2tp_nl_cmd_ops[cfg.pw_type]) {
                genl_unlock();
                request_module("net-l2tp-type-%u", cfg.pw_type);
                genl_lock();
        }
#endif
        if (!l2tp_nl_cmd_ops[cfg.pw_type] || !l2tp_nl_cmd_ops[cfg.pw_type]->session_create) {
                ret = -EPROTONOSUPPORT;
                goto out_tunnel;
        }

        ret = l2tp_nl_cmd_ops[cfg.pw_type]->session_create(net, tunnel,
                                                           session_id,
                                                           peer_session_id,
                                                           &cfg);

        if (ret >= 0) {
                session = l2tp_session_get(net, tunnel->sock, tunnel->version,
                                           tunnel_id, session_id);
                if (session) {
                        ret = l2tp_session_notify(&l2tp_nl_family, info, session,
                                                  L2TP_CMD_SESSION_CREATE);
                        l2tp_session_put(session);
                }
        }

out_tunnel:
        l2tp_tunnel_put(tunnel);
out:
        return ret;
}

static int l2tp_nl_cmd_session_delete(struct sk_buff *skb, struct genl_info *info)
{
        int ret = 0;
        struct l2tp_session *session;
        u16 pw_type;

        session = l2tp_nl_session_get(info);
        if (!session) {
                ret = -ENODEV;
                goto out;
        }

        l2tp_session_notify(&l2tp_nl_family, info,
                            session, L2TP_CMD_SESSION_DELETE);

        pw_type = session->pwtype;
        if (pw_type < __L2TP_PWTYPE_MAX)
                if (l2tp_nl_cmd_ops[pw_type] && l2tp_nl_cmd_ops[pw_type]->session_delete)
                        l2tp_nl_cmd_ops[pw_type]->session_delete(session);

        l2tp_session_put(session);

out:
        return ret;
}

static int l2tp_nl_cmd_session_modify(struct sk_buff *skb, struct genl_info *info)
{
        int ret = 0;
        struct l2tp_session *session;

        session = l2tp_nl_session_get(info);
        if (!session) {
                ret = -ENODEV;
                goto out;
        }

        if (info->attrs[L2TP_ATTR_RECV_SEQ])
                session->recv_seq = nla_get_u8(info->attrs[L2TP_ATTR_RECV_SEQ]);

        if (info->attrs[L2TP_ATTR_SEND_SEQ]) {
                struct l2tp_tunnel *tunnel = session->tunnel;

                session->send_seq = nla_get_u8(info->attrs[L2TP_ATTR_SEND_SEQ]);
                l2tp_session_set_header_len(session, tunnel->version, tunnel->encap);
        }

        if (info->attrs[L2TP_ATTR_LNS_MODE])
                session->lns_mode = nla_get_u8(info->attrs[L2TP_ATTR_LNS_MODE]);

        if (info->attrs[L2TP_ATTR_RECV_TIMEOUT])
                session->reorder_timeout = nla_get_msecs(info->attrs[L2TP_ATTR_RECV_TIMEOUT]);

        ret = l2tp_session_notify(&l2tp_nl_family, info,
                                  session, L2TP_CMD_SESSION_MODIFY);

        l2tp_session_put(session);

out:
        return ret;
}

static int l2tp_nl_session_send(struct sk_buff *skb, u32 portid, u32 seq, int flags,
                                struct l2tp_session *session, u8 cmd)
{
        void *hdr;
        struct nlattr *nest;
        struct l2tp_tunnel *tunnel = session->tunnel;

        hdr = genlmsg_put(skb, portid, seq, &l2tp_nl_family, flags, cmd);
        if (!hdr)
                return -EMSGSIZE;

        if (nla_put_u32(skb, L2TP_ATTR_CONN_ID, tunnel->tunnel_id) ||
            nla_put_u32(skb, L2TP_ATTR_SESSION_ID, session->session_id) ||
            nla_put_u32(skb, L2TP_ATTR_PEER_CONN_ID, tunnel->peer_tunnel_id) ||
            nla_put_u32(skb, L2TP_ATTR_PEER_SESSION_ID, session->peer_session_id) ||
            nla_put_u32(skb, L2TP_ATTR_DEBUG, 0) ||
            nla_put_u16(skb, L2TP_ATTR_PW_TYPE, session->pwtype))
                goto nla_put_failure;

        if ((session->ifname[0] &&
             nla_put_string(skb, L2TP_ATTR_IFNAME, session->ifname)) ||
            (session->cookie_len &&
             nla_put(skb, L2TP_ATTR_COOKIE, session->cookie_len, session->cookie)) ||
            (session->peer_cookie_len &&
             nla_put(skb, L2TP_ATTR_PEER_COOKIE, session->peer_cookie_len, session->peer_cookie)) ||
            nla_put_u8(skb, L2TP_ATTR_RECV_SEQ, session->recv_seq) ||
            nla_put_u8(skb, L2TP_ATTR_SEND_SEQ, session->send_seq) ||
            nla_put_u8(skb, L2TP_ATTR_LNS_MODE, session->lns_mode) ||
            (l2tp_tunnel_uses_xfrm(tunnel) &&
             nla_put_u8(skb, L2TP_ATTR_USING_IPSEC, 1)) ||
            (session->reorder_timeout &&
             nla_put_msecs(skb, L2TP_ATTR_RECV_TIMEOUT,
                           session->reorder_timeout, L2TP_ATTR_PAD)))
                goto nla_put_failure;

        nest = nla_nest_start_noflag(skb, L2TP_ATTR_STATS);
        if (!nest)
                goto nla_put_failure;

        if (nla_put_u64_64bit(skb, L2TP_ATTR_TX_PACKETS,
                              atomic_long_read(&session->stats.tx_packets),
                              L2TP_ATTR_STATS_PAD) ||
            nla_put_u64_64bit(skb, L2TP_ATTR_TX_BYTES,
                              atomic_long_read(&session->stats.tx_bytes),
                              L2TP_ATTR_STATS_PAD) ||
            nla_put_u64_64bit(skb, L2TP_ATTR_TX_ERRORS,
                              atomic_long_read(&session->stats.tx_errors),
                              L2TP_ATTR_STATS_PAD) ||
            nla_put_u64_64bit(skb, L2TP_ATTR_RX_PACKETS,
                              atomic_long_read(&session->stats.rx_packets),
                              L2TP_ATTR_STATS_PAD) ||
            nla_put_u64_64bit(skb, L2TP_ATTR_RX_BYTES,
                              atomic_long_read(&session->stats.rx_bytes),
                              L2TP_ATTR_STATS_PAD) ||
            nla_put_u64_64bit(skb, L2TP_ATTR_RX_SEQ_DISCARDS,
                              atomic_long_read(&session->stats.rx_seq_discards),
                              L2TP_ATTR_STATS_PAD) ||
            nla_put_u64_64bit(skb, L2TP_ATTR_RX_COOKIE_DISCARDS,
                              atomic_long_read(&session->stats.rx_cookie_discards),
                              L2TP_ATTR_STATS_PAD) ||
            nla_put_u64_64bit(skb, L2TP_ATTR_RX_OOS_PACKETS,
                              atomic_long_read(&session->stats.rx_oos_packets),
                              L2TP_ATTR_STATS_PAD) ||
            nla_put_u64_64bit(skb, L2TP_ATTR_RX_ERRORS,
                              atomic_long_read(&session->stats.rx_errors),
                              L2TP_ATTR_STATS_PAD) ||
            nla_put_u64_64bit(skb, L2TP_ATTR_RX_INVALID,
                              atomic_long_read(&session->stats.rx_invalid),
                              L2TP_ATTR_STATS_PAD))
                goto nla_put_failure;
        nla_nest_end(skb, nest);

        genlmsg_end(skb, hdr);
        return 0;

 nla_put_failure:
        genlmsg_cancel(skb, hdr);
        return -1;
}

static int l2tp_nl_cmd_session_get(struct sk_buff *skb, struct genl_info *info)
{
        struct l2tp_session *session;
        struct sk_buff *msg;
        int ret;

        session = l2tp_nl_session_get(info);
        if (!session) {
                ret = -ENODEV;
                goto err;
        }

        msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
        if (!msg) {
                ret = -ENOMEM;
                goto err_ref;
        }

        ret = l2tp_nl_session_send(msg, info->snd_portid, info->snd_seq,
                                   0, session, L2TP_CMD_SESSION_GET);
        if (ret < 0)
                goto err_ref_msg;

        ret = genlmsg_unicast(genl_info_net(info), msg, info->snd_portid);

        l2tp_session_put(session);

        return ret;

err_ref_msg:
        nlmsg_free(msg);
err_ref:
        l2tp_session_put(session);
err:
        return ret;
}

static int l2tp_nl_cmd_session_dump(struct sk_buff *skb, struct netlink_callback *cb)
{
        struct l2tp_nl_cb_data *cbd = (void *)&cb->ctx[0];
        struct net *net = sock_net(skb->sk);
        struct l2tp_session *session;
        struct l2tp_tunnel *tunnel = NULL;
        unsigned long tkey = cbd->tkey;
        unsigned long skey = cbd->skey;

        for (;;) {
                if (!tunnel) {
                        tunnel = l2tp_tunnel_get_next(net, &tkey);
                        if (!tunnel)
                                goto out;
                }

                session = l2tp_session_get_next(net, tunnel->sock, tunnel->version,
                                                tunnel->tunnel_id, &skey);
                if (!session) {
                        tkey++;
                        l2tp_tunnel_put(tunnel);
                        tunnel = NULL;
                        skey = 0;
                        continue;
                }

                if (l2tp_nl_session_send(skb, NETLINK_CB(cb->skb).portid,
                                         cb->nlh->nlmsg_seq, NLM_F_MULTI,
                                         session, L2TP_CMD_SESSION_GET) < 0) {
                        l2tp_session_put(session);
                        l2tp_tunnel_put(tunnel);
                        break;
                }
                l2tp_session_put(session);

                skey++;
        }

out:
        cbd->tkey = tkey;
        cbd->skey = skey;

        return skb->len;
}

static const struct nla_policy l2tp_nl_policy[L2TP_ATTR_MAX + 1] = {
        [L2TP_ATTR_NONE]                = { .type = NLA_UNSPEC, },
        [L2TP_ATTR_PW_TYPE]             = { .type = NLA_U16, },
        [L2TP_ATTR_ENCAP_TYPE]          = { .type = NLA_U16, },
        [L2TP_ATTR_OFFSET]              = { .type = NLA_U16, },
        [L2TP_ATTR_DATA_SEQ]            = { .type = NLA_U8, },
        [L2TP_ATTR_L2SPEC_TYPE]         = { .type = NLA_U8, },
        [L2TP_ATTR_L2SPEC_LEN]          = { .type = NLA_U8, },
        [L2TP_ATTR_PROTO_VERSION]       = { .type = NLA_U8, },
        [L2TP_ATTR_CONN_ID]             = { .type = NLA_U32, },
        [L2TP_ATTR_PEER_CONN_ID]        = { .type = NLA_U32, },
        [L2TP_ATTR_SESSION_ID]          = { .type = NLA_U32, },
        [L2TP_ATTR_PEER_SESSION_ID]     = { .type = NLA_U32, },
        [L2TP_ATTR_UDP_CSUM]            = { .type = NLA_U8, },
        [L2TP_ATTR_VLAN_ID]             = { .type = NLA_U16, },
        [L2TP_ATTR_DEBUG]               = { .type = NLA_U32, },
        [L2TP_ATTR_RECV_SEQ]            = { .type = NLA_U8, },
        [L2TP_ATTR_SEND_SEQ]            = { .type = NLA_U8, },
        [L2TP_ATTR_LNS_MODE]            = { .type = NLA_U8, },
        [L2TP_ATTR_USING_IPSEC]         = { .type = NLA_U8, },
        [L2TP_ATTR_RECV_TIMEOUT]        = { .type = NLA_MSECS, },
        [L2TP_ATTR_FD]                  = { .type = NLA_U32, },
        [L2TP_ATTR_IP_SADDR]            = { .type = NLA_U32, },
        [L2TP_ATTR_IP_DADDR]            = { .type = NLA_U32, },
        [L2TP_ATTR_UDP_SPORT]           = { .type = NLA_U16, },
        [L2TP_ATTR_UDP_DPORT]           = { .type = NLA_U16, },
        [L2TP_ATTR_MTU]                 = { .type = NLA_U16, },
        [L2TP_ATTR_MRU]                 = { .type = NLA_U16, },
        [L2TP_ATTR_STATS]               = { .type = NLA_NESTED, },
        [L2TP_ATTR_IP6_SADDR] = {
                .type = NLA_BINARY,
                .len = sizeof(struct in6_addr),
        },
        [L2TP_ATTR_IP6_DADDR] = {
                .type = NLA_BINARY,
                .len = sizeof(struct in6_addr),
        },
        [L2TP_ATTR_IFNAME] = {
                .type = NLA_NUL_STRING,
                .len = IFNAMSIZ - 1,
        },
        [L2TP_ATTR_COOKIE] = {
                .type = NLA_BINARY,
                .len = 8,
        },
        [L2TP_ATTR_PEER_COOKIE] = {
                .type = NLA_BINARY,
                .len = 8,
        },
};

static const struct genl_small_ops l2tp_nl_ops[] = {
        {
                .cmd = L2TP_CMD_NOOP,
                .validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
                .doit = l2tp_nl_cmd_noop,
                /* can be retrieved by unprivileged users */
        },
        {
                .cmd = L2TP_CMD_TUNNEL_CREATE,
                .validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
                .doit = l2tp_nl_cmd_tunnel_create,
                .flags = GENL_UNS_ADMIN_PERM,
        },
        {
                .cmd = L2TP_CMD_TUNNEL_DELETE,
                .validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
                .doit = l2tp_nl_cmd_tunnel_delete,
                .flags = GENL_UNS_ADMIN_PERM,
        },
        {
                .cmd = L2TP_CMD_TUNNEL_MODIFY,
                .validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
                .doit = l2tp_nl_cmd_tunnel_modify,
                .flags = GENL_UNS_ADMIN_PERM,
        },
        {
                .cmd = L2TP_CMD_TUNNEL_GET,
                .validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
                .doit = l2tp_nl_cmd_tunnel_get,
                .dumpit = l2tp_nl_cmd_tunnel_dump,
                .flags = GENL_UNS_ADMIN_PERM,
        },
        {
                .cmd = L2TP_CMD_SESSION_CREATE,
                .validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
                .doit = l2tp_nl_cmd_session_create,
                .flags = GENL_UNS_ADMIN_PERM,
        },
        {
                .cmd = L2TP_CMD_SESSION_DELETE,
                .validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
                .doit = l2tp_nl_cmd_session_delete,
                .flags = GENL_UNS_ADMIN_PERM,
        },
        {
                .cmd = L2TP_CMD_SESSION_MODIFY,
                .validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
                .doit = l2tp_nl_cmd_session_modify,
                .flags = GENL_UNS_ADMIN_PERM,
        },
        {
                .cmd = L2TP_CMD_SESSION_GET,
                .validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
                .doit = l2tp_nl_cmd_session_get,
                .dumpit = l2tp_nl_cmd_session_dump,
                .flags = GENL_UNS_ADMIN_PERM,
        },
};

static struct genl_family l2tp_nl_family __ro_after_init = {
        .name           = L2TP_GENL_NAME,
        .version        = L2TP_GENL_VERSION,
        .hdrsize        = 0,
        .maxattr        = L2TP_ATTR_MAX,
        .policy = l2tp_nl_policy,
        .netnsok        = true,
        .module         = THIS_MODULE,
        .small_ops      = l2tp_nl_ops,
        .n_small_ops    = ARRAY_SIZE(l2tp_nl_ops),
        .resv_start_op  = L2TP_CMD_SESSION_GET + 1,
        .mcgrps         = l2tp_multicast_group,
        .n_mcgrps       = ARRAY_SIZE(l2tp_multicast_group),
};

int l2tp_nl_register_ops(enum l2tp_pwtype pw_type, const struct l2tp_nl_cmd_ops *ops)
{
        int ret;

        ret = -EINVAL;
        if (pw_type >= __L2TP_PWTYPE_MAX)
                goto err;

        genl_lock();
        ret = -EBUSY;
        if (l2tp_nl_cmd_ops[pw_type])
                goto out;

        l2tp_nl_cmd_ops[pw_type] = ops;
        ret = 0;

out:
        genl_unlock();
err:
        return ret;
}
EXPORT_SYMBOL_GPL(l2tp_nl_register_ops);

void l2tp_nl_unregister_ops(enum l2tp_pwtype pw_type)
{
        if (pw_type < __L2TP_PWTYPE_MAX) {
                genl_lock();
                l2tp_nl_cmd_ops[pw_type] = NULL;
                genl_unlock();
        }
}
EXPORT_SYMBOL_GPL(l2tp_nl_unregister_ops);

static int __init l2tp_nl_init(void)
{
        pr_info("L2TP netlink interface\n");
        return genl_register_family(&l2tp_nl_family);
}

static void l2tp_nl_cleanup(void)
{
        genl_unregister_family(&l2tp_nl_family);
}

module_init(l2tp_nl_init);
module_exit(l2tp_nl_cleanup);

MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
MODULE_DESCRIPTION("L2TP netlink");
MODULE_LICENSE("GPL");
MODULE_VERSION("1.0");
MODULE_ALIAS_GENL_FAMILY("l2tp");