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   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/init.h>
   8 #include <linux/kernel.h>
   9 #include <linux/module.h>
  10 #include <linux/skbuff.h>
  11 #include <linux/stringify.h>
  12 #include <net/dst.h>
  13 #include <net/inet_ecn.h>
  14 #include <net/ip.h>
  15 #include <net/xfrm.h>
  16
  17 static inline void ipip_ecn_decapsulate(struct sk_buff *skb)
  18 {
  19         struct iphdr *inner_iph = ipip_hdr(skb);
  20
  21         if (INET_ECN_is_ce(XFRM_MODE_SKB_CB(skb)->tos))
  22                 IP_ECN_set_ce(inner_iph);
  23 }
  24
  25 /* Add encapsulation header.
  26  *
  27  * The top IP header will be constructed per RFC 2401.
  28  */
  29 static int xfrm4_mode_tunnel_output(struct xfrm_state *x, struct sk_buff *skb)
  30 {
  31         struct dst_entry *dst = skb_dst(skb);
  32         struct iphdr *top_iph;
  33         int flags;
  34
  35         skb_set_network_header(skb, -x->props.header_len);
  36         skb->mac_header = skb->network_header +
  37                           offsetof(struct iphdr, protocol);
  38         skb->transport_header = skb->network_header + sizeof(*top_iph);
  39         top_iph = ip_hdr(skb);
  40
  41         top_iph->ihl = 5;
  42         top_iph->version = 4;
  43
  44         top_iph->protocol = xfrm_af2proto(skb_dst(skb)->ops->family);
  45
  46         /* DS disclosed */
  47         top_iph->tos = INET_ECN_encapsulate(XFRM_MODE_SKB_CB(skb)->tos,
  48                                             XFRM_MODE_SKB_CB(skb)->tos);
  49
  50         flags = x->props.flags;
  51         if (flags & XFRM_STATE_NOECN)
  52                 IP_ECN_clear(top_iph);
  53
  54         top_iph->frag_off = (flags & XFRM_STATE_NOPMTUDISC) ?
  55                 0 : (XFRM_MODE_SKB_CB(skb)->frag_off & htons(IP_DF));
  56         ip_select_ident(top_iph, dst->child, NULL);
  57
  58         top_iph->ttl = dst_metric(dst->child, RTAX_HOPLIMIT);
  59
  60         top_iph->saddr = x->props.saddr.a4;
  61         top_iph->daddr = x->id.daddr.a4;
  62
  63         return 0;
  64 }
  65
  66 static int xfrm4_mode_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
  67 {
  68         const unsigned char *old_mac;
  69         int err = -EINVAL;
  70
  71         if (XFRM_MODE_SKB_CB(skb)->protocol != IPPROTO_IPIP)
  72                 goto out;
  73
  74         if (!pskb_may_pull(skb, sizeof(struct iphdr)))
  75                 goto out;
  76
  77         if (skb_cloned(skb) &&
  78             (err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
  79                 goto out;
  80
  81         if (x->props.flags & XFRM_STATE_DECAP_DSCP)
  82                 ipv4_copy_dscp(XFRM_MODE_SKB_CB(skb)->tos, ipip_hdr(skb));
  83         if (!(x->props.flags & XFRM_STATE_NOECN))
  84                 ipip_ecn_decapsulate(skb);
  85
  86         old_mac = skb_mac_header(skb);
  87         skb_set_mac_header(skb, -skb->mac_len);
  88         memmove(skb_mac_header(skb), old_mac, skb->mac_len);
  89         skb_reset_network_header(skb);
  90         err = 0;
  91
  92 out:
  93         return err;
  94 }
  95
  96 static struct xfrm_mode xfrm4_tunnel_mode = {
  97         .input2 = xfrm4_mode_tunnel_input,
  98         .input = xfrm_prepare_input,
  99         .output2 = xfrm4_mode_tunnel_output,
 100         .output = xfrm4_prepare_output,
 101         .owner = THIS_MODULE,
 102         .encap = XFRM_MODE_TUNNEL,
 103         .flags = XFRM_MODE_FLAG_TUNNEL,
 104 };
 105
 106 static int __init xfrm4_mode_tunnel_init(void)
 107 {
 108         return xfrm_register_mode(&xfrm4_tunnel_mode, AF_INET);
 109 }
 110
 111 static void __exit xfrm4_mode_tunnel_exit(void)
 112 {
 113         int err;
 114
 115         err = xfrm_unregister_mode(&xfrm4_tunnel_mode, AF_INET);
 116         BUG_ON(err);
 117 }
 118
 119 module_init(xfrm4_mode_tunnel_init);
 120 module_exit(xfrm4_mode_tunnel_exit);
 121 MODULE_LICENSE("GPL");
 122 MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_TUNNEL);