// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * net/core/netclassid_cgroup.c Classid Cgroupfs Handling
 *
 * Authors:     Thomas Graf <tgraf@suug.ch>
 */

#include <linux/slab.h>
#include <linux/cgroup.h>
#include <linux/fdtable.h>
#include <linux/sched/task.h>

#include <net/cls_cgroup.h>
#include <net/sock.h>

static inline struct cgroup_cls_state *css_cls_state(struct cgroup_subsys_state *css)
{
        return css ? container_of(css, struct cgroup_cls_state, css) : NULL;
}

struct cgroup_cls_state *task_cls_state(struct task_struct *p)
{
        return css_cls_state(task_css_check(p, net_cls_cgrp_id,
                                            rcu_read_lock_held() ||
                                            rcu_read_lock_bh_held() ||
                                            rcu_read_lock_trace_held()));
}
EXPORT_SYMBOL_GPL(task_cls_state);

static struct cgroup_subsys_state *
cgrp_css_alloc(struct cgroup_subsys_state *parent_css)
{
        struct cgroup_cls_state *cs;

        cs = kzalloc_obj(*cs);
        if (!cs)
                return ERR_PTR(-ENOMEM);

        return &cs->css;
}

static int cgrp_css_online(struct cgroup_subsys_state *css)
{
        struct cgroup_cls_state *cs = css_cls_state(css);
        struct cgroup_cls_state *parent = css_cls_state(css->parent);

        if (parent)
                cs->classid = parent->classid;

        return 0;
}

static void cgrp_css_free(struct cgroup_subsys_state *css)
{
        kfree(css_cls_state(css));
}

/*
 * To avoid freezing of sockets creation for tasks with big number of threads
 * and opened sockets lets release file_lock every 1000 iterated descriptors.
 * New sockets will already have been created with new classid.
 */

struct update_classid_context {
        u32 classid;
        unsigned int batch;
};

#define UPDATE_CLASSID_BATCH 1000

static int update_classid_sock(const void *v, struct file *file, unsigned int n)
{
        struct update_classid_context *ctx = (void *)v;
        struct socket *sock = sock_from_file(file);

        if (sock)
                sock_cgroup_set_classid(&sock->sk->sk_cgrp_data, ctx->classid);
        if (--ctx->batch == 0) {
                ctx->batch = UPDATE_CLASSID_BATCH;
                return n + 1;
        }
        return 0;
}

static void update_classid_task(struct task_struct *p, u32 classid)
{
        struct update_classid_context ctx = {
                .classid = classid,
                .batch = UPDATE_CLASSID_BATCH
        };
        unsigned int fd = 0;

        /* Only update the leader task, when many threads in this task,
         * so it can avoid the useless traversal.
         */
        if (!thread_group_leader(p))
                return;

        do {
                task_lock(p);
                fd = iterate_fd(p->files, fd, update_classid_sock, &ctx);
                task_unlock(p);
                cond_resched();
        } while (fd);
}

static void cgrp_attach(struct cgroup_taskset *tset)
{
        struct cgroup_subsys_state *css;
        struct task_struct *p;

        cgroup_taskset_for_each(p, css, tset) {
                update_classid_task(p, css_cls_state(css)->classid);
        }
}

static u64 read_classid(struct cgroup_subsys_state *css, struct cftype *cft)
{
        return css_cls_state(css)->classid;
}

static int write_classid(struct cgroup_subsys_state *css, struct cftype *cft,
                         u64 value)
{
        struct cgroup_cls_state *cs = css_cls_state(css);
        struct css_task_iter it;
        struct task_struct *p;

        cs->classid = (u32)value;

        css_task_iter_start(css, 0, &it);
        while ((p = css_task_iter_next(&it)))
                update_classid_task(p, cs->classid);
        css_task_iter_end(&it);

        return 0;
}

static struct cftype ss_files[] = {
        {
                .name           = "classid",
                .read_u64       = read_classid,
                .write_u64      = write_classid,
        },
        { }     /* terminate */
};

struct cgroup_subsys net_cls_cgrp_subsys = {
        .css_alloc              = cgrp_css_alloc,
        .css_online             = cgrp_css_online,
        .css_free               = cgrp_css_free,
        .attach                 = cgrp_attach,
        .legacy_cftypes         = ss_files,
};