tunnel4.c

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/* tunnel4.c: Generic IP tunnel transformer.
 *
 * Copyright (C) 2003 David S. Miller ([email protected])
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <net/icmp.h>
#include <net/ip.h>
#include <net/protocol.h>
#include <net/xfrm.h>

static struct xfrm_tunnel __rcu *tunnel4_handlers __read_mostly;
static struct xfrm_tunnel __rcu *tunnel64_handlers __read_mostly;
static DEFINE_MUTEX(tunnel4_mutex);

static inline struct xfrm_tunnel __rcu **fam_handlers(unsigned short family)
{
    return (family == AF_INET) ? &tunnel4_handlers : &tunnel64_handlers;
}

int xfrm4_tunnel_register(struct xfrm_tunnel *handler, unsigned short family)
{
    struct xfrm_tunnel __rcu **pprev;
    struct xfrm_tunnel *t;

    int ret = -EEXIST;
    int priority = handler->priority;

    mutex_lock(&tunnel4_mutex);

    for (pprev = fam_handlers(family);
         (t = rcu_dereference_protected(*pprev,
            lockdep_is_held(&tunnel4_mutex))) != NULL;
         pprev = &t->next) {
        if (t->priority > priority)
            break;
        if (t->priority == priority)
            goto err;
    }

    handler->next = *pprev;
    rcu_assign_pointer(*pprev, handler);

    ret = 0;

err:
    mutex_unlock(&tunnel4_mutex);

    return ret;
}
EXPORT_SYMBOL(xfrm4_tunnel_register);

int xfrm4_tunnel_deregister(struct xfrm_tunnel *handler, unsigned short family)
{
    struct xfrm_tunnel __rcu **pprev;
    struct xfrm_tunnel *t;
    int ret = -ENOENT;

    mutex_lock(&tunnel4_mutex);

    for (pprev = fam_handlers(family);
         (t = rcu_dereference_protected(*pprev,
            lockdep_is_held(&tunnel4_mutex))) != NULL;
         pprev = &t->next) {
        if (t == handler) {
            *pprev = handler->next;
            ret = 0;
            break;
        }
    }

    mutex_unlock(&tunnel4_mutex);

    synchronize_net();

    return ret;
}
EXPORT_SYMBOL(xfrm4_tunnel_deregister);

#define for_each_tunnel_rcu(head, handler)      \
    for (handler = rcu_dereference(head);       \
         handler != NULL;               \
         handler = rcu_dereference(handler->next))  \
    
static int tunnel4_rcv(struct sk_buff *skb)
{
    struct xfrm_tunnel *handler;

    if (!pskb_may_pull(skb, sizeof(struct iphdr)))
        goto drop;

    for_each_tunnel_rcu(tunnel4_handlers, handler)
        if (!handler->handler(skb))
            return 0;

    icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0);

drop:
    kfree_skb(skb);
    return 0;
}

#if IS_ENABLED(CONFIG_IPV6)
static int tunnel64_rcv(struct sk_buff *skb)
{
    struct xfrm_tunnel *handler;

    if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
        goto drop;

    for_each_tunnel_rcu(tunnel64_handlers, handler)
        if (!handler->handler(skb))
            return 0;

    icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0);

drop:
    kfree_skb(skb);
    return 0;
}
#endif

static void tunnel4_err(struct sk_buff *skb, u32 info)
{
    struct xfrm_tunnel *handler;

    for_each_tunnel_rcu(tunnel4_handlers, handler)
        if (!handler->err_handler(skb, info))
            break;
}

#if IS_ENABLED(CONFIG_IPV6)
static void tunnel64_err(struct sk_buff *skb, u32 info)
{
    struct xfrm_tunnel *handler;

    for_each_tunnel_rcu(tunnel64_handlers, handler)
        if (!handler->err_handler(skb, info))
            break;
}
#endif

static const struct net_protocol tunnel4_protocol = {
    .handler    =   tunnel4_rcv,
    .err_handler    =   tunnel4_err,
    .no_policy  =   1,
    .netns_ok   =   1,
};

#if IS_ENABLED(CONFIG_IPV6)
static const struct net_protocol tunnel64_protocol = {
    .handler    =   tunnel64_rcv,
    .err_handler    =   tunnel64_err,
    .no_policy  =   1,
    .netns_ok   =   1,
};
#endif

static int __init tunnel4_init(void)
{
    if (inet_add_protocol(&tunnel4_protocol, IPPROTO_IPIP)) {
        pr_err("%s: can't add protocol\n", __func__);
        return -EAGAIN;
    }
#if IS_ENABLED(CONFIG_IPV6)
    if (inet_add_protocol(&tunnel64_protocol, IPPROTO_IPV6)) {
        pr_err("tunnel64 init: can't add protocol\n");
        inet_del_protocol(&tunnel4_protocol, IPPROTO_IPIP);
        return -EAGAIN;
    }
#endif
    return 0;
}

static void __exit tunnel4_fini(void)
{
#if IS_ENABLED(CONFIG_IPV6)
    if (inet_del_protocol(&tunnel64_protocol, IPPROTO_IPV6))
        pr_err("tunnel64 close: can't remove protocol\n");
#endif
    if (inet_del_protocol(&tunnel4_protocol, IPPROTO_IPIP))
        pr_err("tunnel4 close: can't remove protocol\n");
}

module_init(tunnel4_init);
module_exit(tunnel4_fini);
MODULE_LICENSE("GPL");