/*
 * Copyright (c) 2017 Mellanox Technologies Inc.  All rights reserved.
 * Copyright (c) 2010 Voltaire Inc.  All rights reserved.
 *
 * This software is available to you under a choice of one of two
 * licenses.  You may choose to be licensed under the terms of the GNU
 * General Public License (GPL) Version 2, available from the file
 * COPYING in the main directory of this source tree, or the
 * OpenIB.org BSD license below:
 *
 *     Redistribution and use in source and binary forms, with or
 *     without modification, are permitted provided that the following
 *     conditions are met:
 *
 *      - Redistributions of source code must retain the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer.
 *
 *      - Redistributions in binary form must reproduce the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer in the documentation and/or other materials
 *        provided with the distribution.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

#define pr_fmt(fmt) "%s:%s: " fmt, KBUILD_MODNAME, __func__

#include <linux/export.h>
#include <net/netlink.h>
#include <net/net_namespace.h>
#include <net/netns/generic.h>
#include <net/sock.h>
#include <rdma/rdma_netlink.h>
#include <linux/module.h>
#include "core_priv.h"

static struct {
        const struct rdma_nl_cbs *cb_table;
        /* Synchronizes between ongoing netlink commands and netlink client
         * unregistration.
         */
        struct rw_semaphore sem;
} rdma_nl_types[RDMA_NL_NUM_CLIENTS];

bool rdma_nl_chk_listeners(unsigned int group)
{
        struct rdma_dev_net *rnet = rdma_net_to_dev_net(&init_net);

        return netlink_has_listeners(rnet->nl_sock, group);
}
EXPORT_SYMBOL(rdma_nl_chk_listeners);

static bool is_nl_msg_valid(unsigned int type, unsigned int op)
{
        static const unsigned int max_num_ops[RDMA_NL_NUM_CLIENTS] = {
                [RDMA_NL_IWCM] = RDMA_NL_IWPM_NUM_OPS,
                [RDMA_NL_LS] = RDMA_NL_LS_NUM_OPS,
                [RDMA_NL_NLDEV] = RDMA_NLDEV_NUM_OPS,
        };

        /*
         * This BUILD_BUG_ON is intended to catch addition of new
         * RDMA netlink protocol without updating the array above.
         */
        BUILD_BUG_ON(RDMA_NL_NUM_CLIENTS != 6);

        if (type >= RDMA_NL_NUM_CLIENTS)
                return false;

        return (op < max_num_ops[type]) ? true : false;
}

static const struct rdma_nl_cbs *
get_cb_table(const struct sk_buff *skb, unsigned int type, unsigned int op)
{
        const struct rdma_nl_cbs *cb_table;

        /*
         * Currently only NLDEV client is supporting netlink commands in
         * non init_net net namespace.
         */
        if (sock_net(skb->sk) != &init_net && type != RDMA_NL_NLDEV)
                return NULL;

        cb_table = READ_ONCE(rdma_nl_types[type].cb_table);
        if (!cb_table) {
                /*
                 * Didn't get valid reference of the table, attempt module
                 * load once.
                 */
                up_read(&rdma_nl_types[type].sem);

                request_module("rdma-netlink-subsys-%u", type);

                down_read(&rdma_nl_types[type].sem);
                cb_table = READ_ONCE(rdma_nl_types[type].cb_table);
        }
        if (!cb_table || (!cb_table[op].dump && !cb_table[op].doit))
                return NULL;
        return cb_table;
}

void rdma_nl_register(unsigned int index,
                      const struct rdma_nl_cbs cb_table[])
{
        if (WARN_ON(!is_nl_msg_valid(index, 0)) ||
            WARN_ON(READ_ONCE(rdma_nl_types[index].cb_table)))
                return;

        /* Pairs with the READ_ONCE in is_nl_valid() */
        smp_store_release(&rdma_nl_types[index].cb_table, cb_table);
}
EXPORT_SYMBOL(rdma_nl_register);

void rdma_nl_unregister(unsigned int index)
{
        down_write(&rdma_nl_types[index].sem);
        rdma_nl_types[index].cb_table = NULL;
        up_write(&rdma_nl_types[index].sem);
}
EXPORT_SYMBOL(rdma_nl_unregister);

void *ibnl_put_msg(struct sk_buff *skb, struct nlmsghdr **nlh, int seq,
                   int len, int client, int op, int flags)
{
        *nlh = nlmsg_put(skb, 0, seq, RDMA_NL_GET_TYPE(client, op), len, flags);
        if (!*nlh)
                return NULL;
        return nlmsg_data(*nlh);
}
EXPORT_SYMBOL(ibnl_put_msg);

int ibnl_put_attr(struct sk_buff *skb, struct nlmsghdr *nlh,
                  int len, void *data, int type)
{
        if (nla_put(skb, type, len, data)) {
                nlmsg_cancel(skb, nlh);
                return -EMSGSIZE;
        }
        return 0;
}
EXPORT_SYMBOL(ibnl_put_attr);

static int rdma_nl_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
                           struct netlink_ext_ack *extack)
{
        int type = nlh->nlmsg_type;
        unsigned int index = RDMA_NL_GET_CLIENT(type);
        unsigned int op = RDMA_NL_GET_OP(type);
        const struct rdma_nl_cbs *cb_table;
        int err = -EINVAL;

        if (!is_nl_msg_valid(index, op))
                return -EINVAL;

        down_read(&rdma_nl_types[index].sem);
        cb_table = get_cb_table(skb, index, op);
        if (!cb_table)
                goto done;

        if ((cb_table[op].flags & RDMA_NL_ADMIN_PERM) &&
            !netlink_capable(skb, CAP_NET_ADMIN)) {
                err = -EPERM;
                goto done;
        }

        /*
         * LS responses overload the 0x100 (NLM_F_ROOT) flag.  Don't
         * mistakenly call the .dump() function.
         */
        if (index == RDMA_NL_LS) {
                if (cb_table[op].doit)
                        err = cb_table[op].doit(skb, nlh, extack);
                goto done;
        }
        /* FIXME: Convert IWCM to properly handle doit callbacks */
        if ((nlh->nlmsg_flags & NLM_F_DUMP) || index == RDMA_NL_IWCM) {
                struct netlink_dump_control c = {
                        .dump = cb_table[op].dump,
                };
                if (c.dump)
                        err = netlink_dump_start(skb->sk, skb, nlh, &c);
                goto done;
        }

        if (cb_table[op].doit)
                err = cb_table[op].doit(skb, nlh, extack);
done:
        up_read(&rdma_nl_types[index].sem);
        return err;
}

/*
 * This function is similar to netlink_rcv_skb with one exception:
 * It calls to the callback for the netlink messages without NLM_F_REQUEST
 * flag. These messages are intended for RDMA_NL_LS consumer, so it is allowed
 * for that consumer only.
 */
static int rdma_nl_rcv_skb(struct sk_buff *skb, int (*cb)(struct sk_buff *,
                                                   struct nlmsghdr *,
                                                   struct netlink_ext_ack *))
{
        struct netlink_ext_ack extack = {};
        struct nlmsghdr *nlh;
        int err;

        while (skb->len >= nlmsg_total_size(0)) {
                int msglen;

                nlh = nlmsg_hdr(skb);
                err = 0;

                if (nlh->nlmsg_len < NLMSG_HDRLEN || skb->len < nlh->nlmsg_len)
                        return 0;

                /*
                 * Generally speaking, the only requests are handled
                 * by the kernel, but RDMA_NL_LS is different, because it
                 * runs backward netlink scheme. Kernel initiates messages
                 * and waits for reply with data to keep pathrecord cache
                 * in sync.
                 */
                if (!(nlh->nlmsg_flags & NLM_F_REQUEST) &&
                    (RDMA_NL_GET_CLIENT(nlh->nlmsg_type) != RDMA_NL_LS))
                        goto ack;

                /* Skip control messages */
                if (nlh->nlmsg_type < NLMSG_MIN_TYPE)
                        goto ack;

                err = cb(skb, nlh, &extack);
                if (err == -EINTR)
                        goto skip;

ack:
                if (nlh->nlmsg_flags & NLM_F_ACK || err)
                        netlink_ack(skb, nlh, err, &extack);

skip:
                msglen = NLMSG_ALIGN(nlh->nlmsg_len);
                if (msglen > skb->len)
                        msglen = skb->len;
                skb_pull(skb, msglen);
        }

        return 0;
}

static void rdma_nl_rcv(struct sk_buff *skb)
{
        rdma_nl_rcv_skb(skb, &rdma_nl_rcv_msg);
}

int rdma_nl_unicast(struct net *net, struct sk_buff *skb, u32 pid)
{
        struct rdma_dev_net *rnet = rdma_net_to_dev_net(net);
        int err;

        err = netlink_unicast(rnet->nl_sock, skb, pid, MSG_DONTWAIT);
        return (err < 0) ? err : 0;
}
EXPORT_SYMBOL(rdma_nl_unicast);

int rdma_nl_unicast_wait(struct net *net, struct sk_buff *skb, __u32 pid)
{
        struct rdma_dev_net *rnet = rdma_net_to_dev_net(net);
        int err;

        err = netlink_unicast(rnet->nl_sock, skb, pid, 0);
        return (err < 0) ? err : 0;
}
EXPORT_SYMBOL(rdma_nl_unicast_wait);

int rdma_nl_multicast(struct net *net, struct sk_buff *skb,
                      unsigned int group, gfp_t flags)
{
        struct rdma_dev_net *rnet = rdma_net_to_dev_net(net);

        return nlmsg_multicast(rnet->nl_sock, skb, 0, group, flags);
}
EXPORT_SYMBOL(rdma_nl_multicast);

void rdma_nl_init(void)
{
        int idx;

        for (idx = 0; idx < RDMA_NL_NUM_CLIENTS; idx++)
                init_rwsem(&rdma_nl_types[idx].sem);
}

void rdma_nl_exit(void)
{
        int idx;

        for (idx = 0; idx < RDMA_NL_NUM_CLIENTS; idx++)
                WARN(rdma_nl_types[idx].cb_table,
                     "Netlink client %d wasn't released prior to unloading %s\n",
                     idx, KBUILD_MODNAME);
}

int rdma_nl_net_init(struct rdma_dev_net *rnet)
{
        struct net *net = read_pnet(&rnet->net);
        struct netlink_kernel_cfg cfg = {
                .input  = rdma_nl_rcv,
        };
        struct sock *nls;

        nls = netlink_kernel_create(net, NETLINK_RDMA, &cfg);
        if (!nls)
                return -ENOMEM;

        nls->sk_sndtimeo = 10 * HZ;
        rnet->nl_sock = nls;
        return 0;
}

void rdma_nl_net_exit(struct rdma_dev_net *rnet)
{
        netlink_kernel_release(rnet->nl_sock);
}

MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_RDMA);