net/ipv4/xfrm4_mode_tunnel.c

   1 /*
   2  * xfrm4_mode_tunnel.c - Tunnel mode encapsulation for IPv4.
   3  *
   4  * Copyright (c) 2004-2006 Herbert Xu <herbert@gondor.apana.org.au>
   5  */
   6
   7 #include <linux/gfp.h>
   8 #include <linux/init.h>
   9 #include <linux/kernel.h>
  10 #include <linux/module.h>
  11 #include <linux/skbuff.h>
  12 #include <linux/stringify.h>
  13 #include <net/dst.h>
  14 #include <net/inet_ecn.h>
  15 #include <net/ip.h>
  16 #include <net/xfrm.h>
  17
  18 /* Informational hook. The decap is still done here. */
  19 static struct xfrm_tunnel __rcu *rcv_notify_handlers __read_mostly;
  20 static DEFINE_MUTEX(xfrm4_mode_tunnel_input_mutex);
  21
  22 int xfrm4_mode_tunnel_input_register(struct xfrm_tunnel *handler)
  23 {
  24         struct xfrm_tunnel __rcu **pprev;
  25         struct xfrm_tunnel *t;
  26         int ret = -EEXIST;
  27         int priority = handler->priority;
  28
  29         mutex_lock(&xfrm4_mode_tunnel_input_mutex);
  30
  31         for (pprev = &rcv_notify_handlers;
  32              (t = rcu_dereference_protected(*pprev,
  33              lockdep_is_held(&xfrm4_mode_tunnel_input_mutex))) != NULL;
  34              pprev = &t->next) {
  35                 if (t->priority > priority)
  36                         break;
  37                 if (t->priority == priority)
  38                         goto err;
  39
  40         }
  41
  42         handler->next = *pprev;
  43         rcu_assign_pointer(*pprev, handler);
  44
  45         ret = 0;
  46
  47 err:
  48         mutex_unlock(&xfrm4_mode_tunnel_input_mutex);
  49         return ret;
  50 }
  51 EXPORT_SYMBOL_GPL(xfrm4_mode_tunnel_input_register);
  52
  53 int xfrm4_mode_tunnel_input_deregister(struct xfrm_tunnel *handler)
  54 {
  55         struct xfrm_tunnel __rcu **pprev;
  56         struct xfrm_tunnel *t;
  57         int ret = -ENOENT;
  58
  59         mutex_lock(&xfrm4_mode_tunnel_input_mutex);
  60         for (pprev = &rcv_notify_handlers;
  61              (t = rcu_dereference_protected(*pprev,
  62              lockdep_is_held(&xfrm4_mode_tunnel_input_mutex))) != NULL;
  63              pprev = &t->next) {
  64                 if (t == handler) {
  65                         *pprev = handler->next;
  66                         ret = 0;
  67                         break;
  68                 }
  69         }
  70         mutex_unlock(&xfrm4_mode_tunnel_input_mutex);
  71         synchronize_net();
  72
  73         return ret;
  74 }
  75 EXPORT_SYMBOL_GPL(xfrm4_mode_tunnel_input_deregister);
  76
  77 static inline void ipip_ecn_decapsulate(struct sk_buff *skb)
  78 {
  79         struct iphdr *inner_iph = ipip_hdr(skb);
  80
  81         if (INET_ECN_is_ce(XFRM_MODE_SKB_CB(skb)->tos))
  82                 IP_ECN_set_ce(inner_iph);
  83 }
  84
  85 /* Add encapsulation header.
  86  *
  87  * The top IP header will be constructed per RFC 2401.
  88  */
  89 static int xfrm4_mode_tunnel_output(struct xfrm_state *x, struct sk_buff *skb)
  90 {
  91         struct dst_entry *dst = skb_dst(skb);
  92         struct iphdr *top_iph;
  93         int flags;
  94
  95         skb_set_network_header(skb, -x->props.header_len);
  96         skb->mac_header = skb->network_header +
  97                           offsetof(struct iphdr, protocol);
  98         skb->transport_header = skb->network_header + sizeof(*top_iph);
  99         top_iph = ip_hdr(skb);
 100
 101         top_iph->ihl = 5;
 102         top_iph->version = 4;
 103
 104         top_iph->protocol = xfrm_af2proto(skb_dst(skb)->ops->family);
 105
 106         /* DS disclosed */
 107         top_iph->tos = INET_ECN_encapsulate(XFRM_MODE_SKB_CB(skb)->tos,
 108                                             XFRM_MODE_SKB_CB(skb)->tos);
 109
 110         flags = x->props.flags;
 111         if (flags & XFRM_STATE_NOECN)
 112                 IP_ECN_clear(top_iph);
 113
 114         top_iph->frag_off = (flags & XFRM_STATE_NOPMTUDISC) ?
 115                 0 : (XFRM_MODE_SKB_CB(skb)->frag_off & htons(IP_DF));
 116         ip_select_ident(top_iph, dst->child, NULL);
 117
 118         top_iph->ttl = ip4_dst_hoplimit(dst->child);
 119
 120         top_iph->saddr = x->props.saddr.a4;
 121         top_iph->daddr = x->id.daddr.a4;
 122
 123         return 0;
 124 }
 125
 126 #define for_each_input_rcu(head, handler)       \
 127         for (handler = rcu_dereference(head);   \
 128              handler != NULL;                   \
 129              handler = rcu_dereference(handler->next))
 130
 131 static int xfrm4_mode_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
 132 {
 133         struct xfrm_tunnel *handler;
 134         int err = -EINVAL;
 135
 136         if (XFRM_MODE_SKB_CB(skb)->protocol != IPPROTO_IPIP)
 137                 goto out;
 138
 139         if (!pskb_may_pull(skb, sizeof(struct iphdr)))
 140                 goto out;
 141
 142         for_each_input_rcu(rcv_notify_handlers, handler)
 143                 handler->handler(skb);
 144
 145         err = skb_unclone(skb, GFP_ATOMIC);
 146         if (err)
 147                 goto out;
 148
 149         if (x->props.flags & XFRM_STATE_DECAP_DSCP)
 150                 ipv4_copy_dscp(XFRM_MODE_SKB_CB(skb)->tos, ipip_hdr(skb));
 151         if (!(x->props.flags & XFRM_STATE_NOECN))
 152                 ipip_ecn_decapsulate(skb);
 153
 154         skb_reset_network_header(skb);
 155         skb_mac_header_rebuild(skb);
 156
 157         err = 0;
 158
 159 out:
 160         return err;
 161 }
 162
 163 static struct xfrm_mode xfrm4_tunnel_mode = {
 164         .input2 = xfrm4_mode_tunnel_input,
 165         .input = xfrm_prepare_input,
 166         .output2 = xfrm4_mode_tunnel_output,
 167         .output = xfrm4_prepare_output,
 168         .owner = THIS_MODULE,
 169         .encap = XFRM_MODE_TUNNEL,
 170         .flags = XFRM_MODE_FLAG_TUNNEL,
 171 };
 172
 173 static int __init xfrm4_mode_tunnel_init(void)
 174 {
 175         return xfrm_register_mode(&xfrm4_tunnel_mode, AF_INET);
 176 }
 177
 178 static void __exit xfrm4_mode_tunnel_exit(void)
 179 {
 180         int err;
 181
 182         err = xfrm_unregister_mode(&xfrm4_tunnel_mode, AF_INET);
 183         BUG_ON(err);
 184 }
 185
 186 module_init(xfrm4_mode_tunnel_init);
 187 module_exit(xfrm4_mode_tunnel_exit);
 188 MODULE_LICENSE("GPL");
 189 MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_TUNNEL);