net_namespace.c

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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/workqueue.h>
#include <linux/rtnetlink.h>
#include <linux/cache.h>
#include <linux/slab.h>
#include <linux/list.h>
#include <linux/delay.h>
#include <linux/sched.h>
#include <linux/idr.h>
#include <linux/rculist.h>
#include <linux/nsproxy.h>
#include <linux/proc_fs.h>
#include <linux/file.h>
#include <linux/export.h>
#include <net/net_namespace.h>
#include <net/netns/generic.h>

/*
 *  Our network namespace constructor/destructor lists
 */

static LIST_HEAD(pernet_list);
static struct list_head *first_device = &pernet_list;
static DEFINE_MUTEX(net_mutex);

LIST_HEAD(net_namespace_list);
EXPORT_SYMBOL_GPL(net_namespace_list);

struct net init_net = {
    .dev_base_head = LIST_HEAD_INIT(init_net.dev_base_head),
};
EXPORT_SYMBOL(init_net);

#define INITIAL_NET_GEN_PTRS    13 /* +1 for len +2 for rcu_head */

static unsigned int max_gen_ptrs = INITIAL_NET_GEN_PTRS;

static struct net_generic *net_alloc_generic(void)
{
    struct net_generic *ng;
    size_t generic_size = offsetof(struct net_generic, ptr[max_gen_ptrs]);

    ng = kzalloc(generic_size, GFP_KERNEL);
    if (ng)
        ng->len = max_gen_ptrs;

    return ng;
}

static int net_assign_generic(struct net *net, int id, void *data)
{
    struct net_generic *ng, *old_ng;

    BUG_ON(!mutex_is_locked(&net_mutex));
    BUG_ON(id == 0);

    old_ng = rcu_dereference_protected(net->gen,
                       lockdep_is_held(&net_mutex));
    ng = old_ng;
    if (old_ng->len >= id)
        goto assign;

    ng = net_alloc_generic();
    if (ng == NULL)
        return -ENOMEM;

    /*
     * Some synchronisation notes:
     *
     * The net_generic explores the net->gen array inside rcu
     * read section. Besides once set the net->gen->ptr[x]
     * pointer never changes (see rules in netns/generic.h).
     *
     * That said, we simply duplicate this array and schedule
     * the old copy for kfree after a grace period.
     */

    memcpy(&ng->ptr, &old_ng->ptr, old_ng->len * sizeof(void*));

    rcu_assign_pointer(net->gen, ng);
    kfree_rcu(old_ng, rcu);
assign:
    ng->ptr[id - 1] = data;
    return 0;
}

static int ops_init(const struct pernet_operations *ops, struct net *net)
{
    int err = -ENOMEM;
    void *data = NULL;

    if (ops->id && ops->size) {
        data = kzalloc(ops->size, GFP_KERNEL);
        if (!data)
            goto out;

        err = net_assign_generic(net, *ops->id, data);
        if (err)
            goto cleanup;
    }
    err = 0;
    if (ops->init)
        err = ops->init(net);
    if (!err)
        return 0;

cleanup:
    kfree(data);

out:
    return err;
}

static void ops_free(const struct pernet_operations *ops, struct net *net)
{
    if (ops->id && ops->size) {
        int id = *ops->id;
        kfree(net_generic(net, id));
    }
}

static void ops_exit_list(const struct pernet_operations *ops,
              struct list_head *net_exit_list)
{
    struct net *net;
    if (ops->exit) {
        list_for_each_entry(net, net_exit_list, exit_list)
            ops->exit(net);
    }
    if (ops->exit_batch)
        ops->exit_batch(net_exit_list);
}

static void ops_free_list(const struct pernet_operations *ops,
              struct list_head *net_exit_list)
{
    struct net *net;
    if (ops->size && ops->id) {
        list_for_each_entry(net, net_exit_list, exit_list)
            ops_free(ops, net);
    }
}

/*
 * setup_net runs the initializers for the network namespace object.
 */
static __net_init int setup_net(struct net *net)
{
    /* Must be called with net_mutex held */
    const struct pernet_operations *ops, *saved_ops;
    int error = 0;
    LIST_HEAD(net_exit_list);

    atomic_set(&net->count, 1);
    atomic_set(&net->passive, 1);
    net->dev_base_seq = 1;

#ifdef NETNS_REFCNT_DEBUG
    atomic_set(&net->use_count, 0);
#endif

    list_for_each_entry(ops, &pernet_list, list) {
        error = ops_init(ops, net);
        if (error < 0)
            goto out_undo;
    }
out:
    return error;

out_undo:
    /* Walk through the list backwards calling the exit functions
     * for the pernet modules whose init functions did not fail.
     */
    list_add(&net->exit_list, &net_exit_list);
    saved_ops = ops;
    list_for_each_entry_continue_reverse(ops, &pernet_list, list)
        ops_exit_list(ops, &net_exit_list);

    ops = saved_ops;
    list_for_each_entry_continue_reverse(ops, &pernet_list, list)
        ops_free_list(ops, &net_exit_list);

    rcu_barrier();
    goto out;
}


#ifdef CONFIG_NET_NS
static struct kmem_cache *net_cachep;
static struct workqueue_struct *netns_wq;

static struct net *net_alloc(void)
{
    struct net *net = NULL;
    struct net_generic *ng;

    ng = net_alloc_generic();
    if (!ng)
        goto out;

    net = kmem_cache_zalloc(net_cachep, GFP_KERNEL);
    if (!net)
        goto out_free;

    rcu_assign_pointer(net->gen, ng);
out:
    return net;

out_free:
    kfree(ng);
    goto out;
}

static void net_free(struct net *net)
{
#ifdef NETNS_REFCNT_DEBUG
    if (unlikely(atomic_read(&net->use_count) != 0)) {
        pr_emerg("network namespace not free! Usage: %d\n",
             atomic_read(&net->use_count));
        return;
    }
#endif
    kfree(net->gen);
    kmem_cache_free(net_cachep, net);
}

void net_drop_ns(void *p)
{
    struct net *ns = p;
    if (ns && atomic_dec_and_test(&ns->passive))
        net_free(ns);
}

struct net *copy_net_ns(unsigned long flags, struct net *old_net)
{
    struct net *net;
    int rv;

    if (!(flags & CLONE_NEWNET))
        return get_net(old_net);

    net = net_alloc();
    if (!net)
        return ERR_PTR(-ENOMEM);
    mutex_lock(&net_mutex);
    rv = setup_net(net);
    if (rv == 0) {
        rtnl_lock();
        list_add_tail_rcu(&net->list, &net_namespace_list);
        rtnl_unlock();
    }
    mutex_unlock(&net_mutex);
    if (rv < 0) {
        net_drop_ns(net);
        return ERR_PTR(rv);
    }
    return net;
}

static DEFINE_SPINLOCK(cleanup_list_lock);
static LIST_HEAD(cleanup_list);  /* Must hold cleanup_list_lock to touch */

static void cleanup_net(struct work_struct *work)
{
    const struct pernet_operations *ops;
    struct net *net, *tmp;
    LIST_HEAD(net_kill_list);
    LIST_HEAD(net_exit_list);

    /* Atomically snapshot the list of namespaces to cleanup */
    spin_lock_irq(&cleanup_list_lock);
    list_replace_init(&cleanup_list, &net_kill_list);
    spin_unlock_irq(&cleanup_list_lock);

    mutex_lock(&net_mutex);

    /* Don't let anyone else find us. */
    rtnl_lock();
    list_for_each_entry(net, &net_kill_list, cleanup_list) {
        list_del_rcu(&net->list);
        list_add_tail(&net->exit_list, &net_exit_list);
    }
    rtnl_unlock();

    /*
     * Another CPU might be rcu-iterating the list, wait for it.
     * This needs to be before calling the exit() notifiers, so
     * the rcu_barrier() below isn't sufficient alone.
     */
    synchronize_rcu();

    /* Run all of the network namespace exit methods */
    list_for_each_entry_reverse(ops, &pernet_list, list)
        ops_exit_list(ops, &net_exit_list);

    /* Free the net generic variables */
    list_for_each_entry_reverse(ops, &pernet_list, list)
        ops_free_list(ops, &net_exit_list);

    mutex_unlock(&net_mutex);

    /* Ensure there are no outstanding rcu callbacks using this
     * network namespace.
     */
    rcu_barrier();

    /* Finally it is safe to free my network namespace structure */
    list_for_each_entry_safe(net, tmp, &net_exit_list, exit_list) {
        list_del_init(&net->exit_list);
        net_drop_ns(net);
    }
}
static DECLARE_WORK(net_cleanup_work, cleanup_net);

void __put_net(struct net *net)
{
    /* Cleanup the network namespace in process context */
    unsigned long flags;

    spin_lock_irqsave(&cleanup_list_lock, flags);
    list_add(&net->cleanup_list, &cleanup_list);
    spin_unlock_irqrestore(&cleanup_list_lock, flags);

    queue_work(netns_wq, &net_cleanup_work);
}
EXPORT_SYMBOL_GPL(__put_net);

struct net *get_net_ns_by_fd(int fd)
{
    struct proc_inode *ei;
    struct file *file;
    struct net *net;

    file = proc_ns_fget(fd);
    if (IS_ERR(file))
        return ERR_CAST(file);

    ei = PROC_I(file->f_dentry->d_inode);
    if (ei->ns_ops == &netns_operations)
        net = get_net(ei->ns);
    else
        net = ERR_PTR(-EINVAL);

    fput(file);
    return net;
}

#else
struct net *copy_net_ns(unsigned long flags, struct net *old_net)
{
    if (flags & CLONE_NEWNET)
        return ERR_PTR(-EINVAL);
    return old_net;
}

struct net *get_net_ns_by_fd(int fd)
{
    return ERR_PTR(-EINVAL);
}
#endif

struct net *get_net_ns_by_pid(pid_t pid)
{
    struct task_struct *tsk;
    struct net *net;

    /* Lookup the network namespace */
    net = ERR_PTR(-ESRCH);
    rcu_read_lock();
    tsk = find_task_by_vpid(pid);
    if (tsk) {
        struct nsproxy *nsproxy;
        nsproxy = task_nsproxy(tsk);
        if (nsproxy)
            net = get_net(nsproxy->net_ns);
    }
    rcu_read_unlock();
    return net;
}
EXPORT_SYMBOL_GPL(get_net_ns_by_pid);

static int __init net_ns_init(void)
{
    struct net_generic *ng;

#ifdef CONFIG_NET_NS
    net_cachep = kmem_cache_create("net_namespace", sizeof(struct net),
                    SMP_CACHE_BYTES,
                    SLAB_PANIC, NULL);

    /* Create workqueue for cleanup */
    netns_wq = create_singlethread_workqueue("netns");
    if (!netns_wq)
        panic("Could not create netns workq");
#endif

    ng = net_alloc_generic();
    if (!ng)
        panic("Could not allocate generic netns");

    rcu_assign_pointer(init_net.gen, ng);

    mutex_lock(&net_mutex);
    if (setup_net(&init_net))
        panic("Could not setup the initial network namespace");

    rtnl_lock();
    list_add_tail_rcu(&init_net.list, &net_namespace_list);
    rtnl_unlock();

    mutex_unlock(&net_mutex);

    return 0;
}

pure_initcall(net_ns_init);

#ifdef CONFIG_NET_NS
static int __register_pernet_operations(struct list_head *list,
                    struct pernet_operations *ops)
{
    struct net *net;
    int error;
    LIST_HEAD(net_exit_list);

    list_add_tail(&ops->list, list);
    if (ops->init || (ops->id && ops->size)) {
        for_each_net(net) {
            error = ops_init(ops, net);
            if (error)
                goto out_undo;
            list_add_tail(&net->exit_list, &net_exit_list);
        }
    }
    return 0;

out_undo:
    /* If I have an error cleanup all namespaces I initialized */
    list_del(&ops->list);
    ops_exit_list(ops, &net_exit_list);
    ops_free_list(ops, &net_exit_list);
    return error;
}

static void __unregister_pernet_operations(struct pernet_operations *ops)
{
    struct net *net;
    LIST_HEAD(net_exit_list);

    list_del(&ops->list);
    for_each_net(net)
        list_add_tail(&net->exit_list, &net_exit_list);
    ops_exit_list(ops, &net_exit_list);
    ops_free_list(ops, &net_exit_list);
}

#else

static int __register_pernet_operations(struct list_head *list,
                    struct pernet_operations *ops)
{
    return ops_init(ops, &init_net);
}

static void __unregister_pernet_operations(struct pernet_operations *ops)
{
    LIST_HEAD(net_exit_list);
    list_add(&init_net.exit_list, &net_exit_list);
    ops_exit_list(ops, &net_exit_list);
    ops_free_list(ops, &net_exit_list);
}

#endif /* CONFIG_NET_NS */

static DEFINE_IDA(net_generic_ids);

static int register_pernet_operations(struct list_head *list,
                      struct pernet_operations *ops)
{
    int error;

    if (ops->id) {
again:
        error = ida_get_new_above(&net_generic_ids, 1, ops->id);
        if (error < 0) {
            if (error == -EAGAIN) {
                ida_pre_get(&net_generic_ids, GFP_KERNEL);
                goto again;
            }
            return error;
        }
        max_gen_ptrs = max_t(unsigned int, max_gen_ptrs, *ops->id);
    }
    error = __register_pernet_operations(list, ops);
    if (error) {
        rcu_barrier();
        if (ops->id)
            ida_remove(&net_generic_ids, *ops->id);
    }

    return error;
}

static void unregister_pernet_operations(struct pernet_operations *ops)
{
    
    __unregister_pernet_operations(ops);
    rcu_barrier();
    if (ops->id)
        ida_remove(&net_generic_ids, *ops->id);
}

int register_pernet_subsys(struct pernet_operations *ops)
{
    int error;
    mutex_lock(&net_mutex);
    error =  register_pernet_operations(first_device, ops);
    mutex_unlock(&net_mutex);
    return error;
}
EXPORT_SYMBOL_GPL(register_pernet_subsys);

void unregister_pernet_subsys(struct pernet_operations *ops)
{
    mutex_lock(&net_mutex);
    unregister_pernet_operations(ops);
    mutex_unlock(&net_mutex);
}
EXPORT_SYMBOL_GPL(unregister_pernet_subsys);

int register_pernet_device(struct pernet_operations *ops)
{
    int error;
    mutex_lock(&net_mutex);
    error = register_pernet_operations(&pernet_list, ops);
    if (!error && (first_device == &pernet_list))
        first_device = &ops->list;
    mutex_unlock(&net_mutex);
    return error;
}
EXPORT_SYMBOL_GPL(register_pernet_device);

void unregister_pernet_device(struct pernet_operations *ops)
{
    mutex_lock(&net_mutex);
    if (&ops->list == first_device)
        first_device = first_device->next;
    unregister_pernet_operations(ops);
    mutex_unlock(&net_mutex);
}
EXPORT_SYMBOL_GPL(unregister_pernet_device);

#ifdef CONFIG_NET_NS
static void *netns_get(struct task_struct *task)
{
    struct net *net = NULL;
    struct nsproxy *nsproxy;

    rcu_read_lock();
    nsproxy = task_nsproxy(task);
    if (nsproxy)
        net = get_net(nsproxy->net_ns);
    rcu_read_unlock();

    return net;
}

static void netns_put(void *ns)
{
    put_net(ns);
}

static int netns_install(struct nsproxy *nsproxy, void *ns)
{
    put_net(nsproxy->net_ns);
    nsproxy->net_ns = get_net(ns);
    return 0;
}

const struct proc_ns_operations netns_operations = {
    .name       = "net",
    .type       = CLONE_NEWNET,
    .get        = netns_get,
    .put        = netns_put,
    .install    = netns_install,
};
#endif