// SPDX-License-Identifier: GPL-2.0

#include <linux/bpf.h>
#include <linux/bpf-netns.h>
#include <linux/filter.h>
#include <net/net_namespace.h>

/*
 * Functions to manage BPF programs attached to netns
 */

struct bpf_netns_link {
        struct bpf_link link;

        /* We don't hold a ref to net in order to auto-detach the link
         * when netns is going away. Instead we rely on pernet
         * pre_exit callback to clear this pointer. Must be accessed
         * with netns_bpf_mutex held.
         */
        struct net *net;
        struct list_head node; /* node in list of links attached to net */
        enum netns_bpf_attach_type netns_type;
};

/* Protects updates to netns_bpf */
DEFINE_MUTEX(netns_bpf_mutex);

static void netns_bpf_attach_type_unneed(enum netns_bpf_attach_type type)
{
        switch (type) {
#ifdef CONFIG_INET
        case NETNS_BPF_SK_LOOKUP:
                static_branch_dec(&bpf_sk_lookup_enabled);
                break;
#endif
        default:
                break;
        }
}

static void netns_bpf_attach_type_need(enum netns_bpf_attach_type type)
{
        switch (type) {
#ifdef CONFIG_INET
        case NETNS_BPF_SK_LOOKUP:
                static_branch_inc(&bpf_sk_lookup_enabled);
                break;
#endif
        default:
                break;
        }
}

/* Must be called with netns_bpf_mutex held. */
static void netns_bpf_run_array_detach(struct net *net,
                                       enum netns_bpf_attach_type type)
{
        struct bpf_prog_array *run_array;

        run_array = rcu_replace_pointer(net->bpf.run_array[type], NULL,
                                        lockdep_is_held(&netns_bpf_mutex));
        bpf_prog_array_free(run_array);
}

static int link_index(struct net *net, enum netns_bpf_attach_type type,
                      struct bpf_netns_link *link)
{
        struct bpf_netns_link *pos;
        int i = 0;

        list_for_each_entry(pos, &net->bpf.links[type], node) {
                if (pos == link)
                        return i;
                i++;
        }
        return -ENOENT;
}

static int link_count(struct net *net, enum netns_bpf_attach_type type)
{
        struct list_head *pos;
        int i = 0;

        list_for_each(pos, &net->bpf.links[type])
                i++;
        return i;
}

static void fill_prog_array(struct net *net, enum netns_bpf_attach_type type,
                            struct bpf_prog_array *prog_array)
{
        struct bpf_netns_link *pos;
        unsigned int i = 0;

        list_for_each_entry(pos, &net->bpf.links[type], node) {
                prog_array->items[i].prog = pos->link.prog;
                i++;
        }
}

static void bpf_netns_link_release(struct bpf_link *link)
{
        struct bpf_netns_link *net_link =
                container_of(link, struct bpf_netns_link, link);
        enum netns_bpf_attach_type type = net_link->netns_type;
        struct bpf_prog_array *old_array, *new_array;
        struct net *net;
        int cnt, idx;

        mutex_lock(&netns_bpf_mutex);

        /* We can race with cleanup_net, but if we see a non-NULL
         * struct net pointer, pre_exit has not run yet and wait for
         * netns_bpf_mutex.
         */
        net = net_link->net;
        if (!net)
                goto out_unlock;

        /* Mark attach point as unused */
        netns_bpf_attach_type_unneed(type);

        /* Remember link position in case of safe delete */
        idx = link_index(net, type, net_link);
        list_del(&net_link->node);

        cnt = link_count(net, type);
        if (!cnt) {
                netns_bpf_run_array_detach(net, type);
                goto out_unlock;
        }

        old_array = rcu_dereference_protected(net->bpf.run_array[type],
                                              lockdep_is_held(&netns_bpf_mutex));
        new_array = bpf_prog_array_alloc(cnt, GFP_KERNEL);
        if (!new_array) {
                WARN_ON(bpf_prog_array_delete_safe_at(old_array, idx));
                goto out_unlock;
        }
        fill_prog_array(net, type, new_array);
        rcu_assign_pointer(net->bpf.run_array[type], new_array);
        bpf_prog_array_free(old_array);

out_unlock:
        net_link->net = NULL;
        mutex_unlock(&netns_bpf_mutex);
}

static int bpf_netns_link_detach(struct bpf_link *link)
{
        bpf_netns_link_release(link);
        return 0;
}

static void bpf_netns_link_dealloc(struct bpf_link *link)
{
        struct bpf_netns_link *net_link =
                container_of(link, struct bpf_netns_link, link);

        kfree(net_link);
}

static int bpf_netns_link_update_prog(struct bpf_link *link,
                                      struct bpf_prog *new_prog,
                                      struct bpf_prog *old_prog)
{
        struct bpf_netns_link *net_link =
                container_of(link, struct bpf_netns_link, link);
        enum netns_bpf_attach_type type = net_link->netns_type;
        struct bpf_prog_array *run_array;
        struct net *net;
        int idx, ret;

        if (old_prog && old_prog != link->prog)
                return -EPERM;
        if (new_prog->type != link->prog->type)
                return -EINVAL;

        mutex_lock(&netns_bpf_mutex);

        net = net_link->net;
        if (!net || !check_net(net)) {
                /* Link auto-detached or netns dying */
                ret = -ENOLINK;
                goto out_unlock;
        }

        run_array = rcu_dereference_protected(net->bpf.run_array[type],
                                              lockdep_is_held(&netns_bpf_mutex));
        idx = link_index(net, type, net_link);
        ret = bpf_prog_array_update_at(run_array, idx, new_prog);
        if (ret)
                goto out_unlock;

        old_prog = xchg(&link->prog, new_prog);
        bpf_prog_put(old_prog);

out_unlock:
        mutex_unlock(&netns_bpf_mutex);
        return ret;
}

static int bpf_netns_link_fill_info(const struct bpf_link *link,
                                    struct bpf_link_info *info)
{
        const struct bpf_netns_link *net_link =
                container_of(link, struct bpf_netns_link, link);
        unsigned int inum = 0;
        struct net *net;

        mutex_lock(&netns_bpf_mutex);
        net = net_link->net;
        if (net && check_net(net))
                inum = net->ns.inum;
        mutex_unlock(&netns_bpf_mutex);

        info->netns.netns_ino = inum;
        info->netns.attach_type = link->attach_type;
        return 0;
}

static void bpf_netns_link_show_fdinfo(const struct bpf_link *link,
                                       struct seq_file *seq)
{
        struct bpf_link_info info = {};

        bpf_netns_link_fill_info(link, &info);
        seq_printf(seq,
                   "netns_ino:\t%u\n"
                   "attach_type:\t%u\n",
                   info.netns.netns_ino,
                   link->attach_type);
}

static const struct bpf_link_ops bpf_netns_link_ops = {
        .release = bpf_netns_link_release,
        .dealloc = bpf_netns_link_dealloc,
        .detach = bpf_netns_link_detach,
        .update_prog = bpf_netns_link_update_prog,
        .fill_link_info = bpf_netns_link_fill_info,
        .show_fdinfo = bpf_netns_link_show_fdinfo,
};

/* Must be called with netns_bpf_mutex held. */
static int __netns_bpf_prog_query(const union bpf_attr *attr,
                                  union bpf_attr __user *uattr,
                                  struct net *net,
                                  enum netns_bpf_attach_type type)
{
        __u32 __user *prog_ids = u64_to_user_ptr(attr->query.prog_ids);
        struct bpf_prog_array *run_array;
        u32 prog_cnt = 0, flags = 0;

        run_array = rcu_dereference_protected(net->bpf.run_array[type],
                                              lockdep_is_held(&netns_bpf_mutex));
        if (run_array)
                prog_cnt = bpf_prog_array_length(run_array);

        if (copy_to_user(&uattr->query.attach_flags, &flags, sizeof(flags)))
                return -EFAULT;
        if (copy_to_user(&uattr->query.prog_cnt, &prog_cnt, sizeof(prog_cnt)))
                return -EFAULT;
        if (!attr->query.prog_cnt || !prog_ids || !prog_cnt)
                return 0;

        return bpf_prog_array_copy_to_user(run_array, prog_ids,
                                           attr->query.prog_cnt);
}

int netns_bpf_prog_query(const union bpf_attr *attr,
                         union bpf_attr __user *uattr)
{
        enum netns_bpf_attach_type type;
        struct net *net;
        int ret;

        if (attr->query.query_flags)
                return -EINVAL;

        type = to_netns_bpf_attach_type(attr->query.attach_type);
        if (type < 0)
                return -EINVAL;

        net = get_net_ns_by_fd(attr->query.target_fd);
        if (IS_ERR(net))
                return PTR_ERR(net);

        mutex_lock(&netns_bpf_mutex);
        ret = __netns_bpf_prog_query(attr, uattr, net, type);
        mutex_unlock(&netns_bpf_mutex);

        put_net(net);
        return ret;
}

int netns_bpf_prog_attach(const union bpf_attr *attr, struct bpf_prog *prog)
{
        struct bpf_prog_array *run_array;
        enum netns_bpf_attach_type type;
        struct bpf_prog *attached;
        struct net *net;
        int ret;

        if (attr->target_fd || attr->attach_flags || attr->replace_bpf_fd)
                return -EINVAL;

        type = to_netns_bpf_attach_type(attr->attach_type);
        if (type < 0)
                return -EINVAL;

        net = current->nsproxy->net_ns;
        mutex_lock(&netns_bpf_mutex);

        /* Attaching prog directly is not compatible with links */
        if (!list_empty(&net->bpf.links[type])) {
                ret = -EEXIST;
                goto out_unlock;
        }

        switch (type) {
        case NETNS_BPF_FLOW_DISSECTOR:
                ret = flow_dissector_bpf_prog_attach_check(net, prog);
                break;
        default:
                ret = -EINVAL;
                break;
        }
        if (ret)
                goto out_unlock;

        attached = net->bpf.progs[type];
        if (attached == prog) {
                /* The same program cannot be attached twice */
                ret = -EINVAL;
                goto out_unlock;
        }

        run_array = rcu_dereference_protected(net->bpf.run_array[type],
                                              lockdep_is_held(&netns_bpf_mutex));
        if (run_array) {
                WRITE_ONCE(run_array->items[0].prog, prog);
        } else {
                run_array = bpf_prog_array_alloc(1, GFP_KERNEL);
                if (!run_array) {
                        ret = -ENOMEM;
                        goto out_unlock;
                }
                run_array->items[0].prog = prog;
                rcu_assign_pointer(net->bpf.run_array[type], run_array);
        }

        net->bpf.progs[type] = prog;
        if (attached)
                bpf_prog_put(attached);

out_unlock:
        mutex_unlock(&netns_bpf_mutex);

        return ret;
}

/* Must be called with netns_bpf_mutex held. */
static int __netns_bpf_prog_detach(struct net *net,
                                   enum netns_bpf_attach_type type,
                                   struct bpf_prog *old)
{
        struct bpf_prog *attached;

        /* Progs attached via links cannot be detached */
        if (!list_empty(&net->bpf.links[type]))
                return -EINVAL;

        attached = net->bpf.progs[type];
        if (!attached || attached != old)
                return -ENOENT;
        netns_bpf_run_array_detach(net, type);
        net->bpf.progs[type] = NULL;
        bpf_prog_put(attached);
        return 0;
}

int netns_bpf_prog_detach(const union bpf_attr *attr, enum bpf_prog_type ptype)
{
        enum netns_bpf_attach_type type;
        struct bpf_prog *prog;
        int ret;

        if (attr->target_fd)
                return -EINVAL;

        type = to_netns_bpf_attach_type(attr->attach_type);
        if (type < 0)
                return -EINVAL;

        prog = bpf_prog_get_type(attr->attach_bpf_fd, ptype);
        if (IS_ERR(prog))
                return PTR_ERR(prog);

        mutex_lock(&netns_bpf_mutex);
        ret = __netns_bpf_prog_detach(current->nsproxy->net_ns, type, prog);
        mutex_unlock(&netns_bpf_mutex);

        bpf_prog_put(prog);

        return ret;
}

static int netns_bpf_max_progs(enum netns_bpf_attach_type type)
{
        switch (type) {
        case NETNS_BPF_FLOW_DISSECTOR:
                return 1;
        case NETNS_BPF_SK_LOOKUP:
                return 64;
        default:
                return 0;
        }
}

static int netns_bpf_link_attach(struct net *net, struct bpf_link *link,
                                 enum netns_bpf_attach_type type)
{
        struct bpf_netns_link *net_link =
                container_of(link, struct bpf_netns_link, link);
        struct bpf_prog_array *run_array;
        int cnt, err;

        mutex_lock(&netns_bpf_mutex);

        cnt = link_count(net, type);
        if (cnt >= netns_bpf_max_progs(type)) {
                err = -E2BIG;
                goto out_unlock;
        }
        /* Links are not compatible with attaching prog directly */
        if (net->bpf.progs[type]) {
                err = -EEXIST;
                goto out_unlock;
        }

        switch (type) {
        case NETNS_BPF_FLOW_DISSECTOR:
                err = flow_dissector_bpf_prog_attach_check(net, link->prog);
                break;
        case NETNS_BPF_SK_LOOKUP:
                err = 0; /* nothing to check */
                break;
        default:
                err = -EINVAL;
                break;
        }
        if (err)
                goto out_unlock;

        run_array = bpf_prog_array_alloc(cnt + 1, GFP_KERNEL);
        if (!run_array) {
                err = -ENOMEM;
                goto out_unlock;
        }

        list_add_tail(&net_link->node, &net->bpf.links[type]);

        fill_prog_array(net, type, run_array);
        run_array = rcu_replace_pointer(net->bpf.run_array[type], run_array,
                                        lockdep_is_held(&netns_bpf_mutex));
        bpf_prog_array_free(run_array);

        /* Mark attach point as used */
        netns_bpf_attach_type_need(type);

out_unlock:
        mutex_unlock(&netns_bpf_mutex);
        return err;
}

int netns_bpf_link_create(const union bpf_attr *attr, struct bpf_prog *prog)
{
        enum netns_bpf_attach_type netns_type;
        struct bpf_link_primer link_primer;
        struct bpf_netns_link *net_link;
        enum bpf_attach_type type;
        struct net *net;
        int err;

        if (attr->link_create.flags)
                return -EINVAL;

        type = attr->link_create.attach_type;
        netns_type = to_netns_bpf_attach_type(type);
        if (netns_type < 0)
                return -EINVAL;

        net = get_net_ns_by_fd(attr->link_create.target_fd);
        if (IS_ERR(net))
                return PTR_ERR(net);

        net_link = kzalloc_obj(*net_link, GFP_USER);
        if (!net_link) {
                err = -ENOMEM;
                goto out_put_net;
        }
        bpf_link_init(&net_link->link, BPF_LINK_TYPE_NETNS,
                      &bpf_netns_link_ops, prog, type);
        net_link->net = net;
        net_link->netns_type = netns_type;

        err = bpf_link_prime(&net_link->link, &link_primer);
        if (err) {
                kfree(net_link);
                goto out_put_net;
        }

        err = netns_bpf_link_attach(net, &net_link->link, netns_type);
        if (err) {
                bpf_link_cleanup(&link_primer);
                goto out_put_net;
        }

        put_net(net);
        return bpf_link_settle(&link_primer);

out_put_net:
        put_net(net);
        return err;
}

static int __net_init netns_bpf_pernet_init(struct net *net)
{
        int type;

        for (type = 0; type < MAX_NETNS_BPF_ATTACH_TYPE; type++)
                INIT_LIST_HEAD(&net->bpf.links[type]);

        return 0;
}

static void __net_exit netns_bpf_pernet_pre_exit(struct net *net)
{
        enum netns_bpf_attach_type type;
        struct bpf_netns_link *net_link;

        mutex_lock(&netns_bpf_mutex);
        for (type = 0; type < MAX_NETNS_BPF_ATTACH_TYPE; type++) {
                netns_bpf_run_array_detach(net, type);
                list_for_each_entry(net_link, &net->bpf.links[type], node) {
                        net_link->net = NULL; /* auto-detach link */
                        netns_bpf_attach_type_unneed(type);
                }
                if (net->bpf.progs[type])
                        bpf_prog_put(net->bpf.progs[type]);
        }
        mutex_unlock(&netns_bpf_mutex);
}

static struct pernet_operations netns_bpf_pernet_ops __net_initdata = {
        .init = netns_bpf_pernet_init,
        .pre_exit = netns_bpf_pernet_pre_exit,
};

static int __init netns_bpf_init(void)
{
        return register_pernet_subsys(&netns_bpf_pernet_ops);
}

subsys_initcall(netns_bpf_init);