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 static inline void ipip_ecn_decapsulate(struct sk_buff *skb)
  19 {
  20         struct iphdr *inner_iph = ipip_hdr(skb);
  21
  22         if (INET_ECN_is_ce(XFRM_MODE_SKB_CB(skb)->tos))
  23                 IP_ECN_set_ce(inner_iph);
  24 }
  25
  26 /* Add encapsulation header.
  27  *
  28  * The top IP header will be constructed per RFC 2401.
  29  */
  30 static int xfrm4_mode_tunnel_output(struct xfrm_state *x, struct sk_buff *skb)
  31 {
  32         struct dst_entry *dst = skb_dst(skb);
  33         struct iphdr *top_iph;
  34         int flags;
  35
  36         skb_set_inner_network_header(skb, skb_network_offset(skb));
  37         skb_set_inner_transport_header(skb, skb_transport_offset(skb));
  38
  39         skb_set_network_header(skb, -x->props.header_len);
  40         skb->mac_header = skb->network_header +
  41                           offsetof(struct iphdr, protocol);
  42         skb->transport_header = skb->network_header + sizeof(*top_iph);
  43         top_iph = ip_hdr(skb);
  44
  45         top_iph->ihl = 5;
  46         top_iph->version = 4;
  47
  48         top_iph->protocol = xfrm_af2proto(skb_dst(skb)->ops->family);
  49
  50         /* DS disclosing depends on XFRM_SA_XFLAG_DONT_ENCAP_DSCP */
  51         if (x->props.extra_flags & XFRM_SA_XFLAG_DONT_ENCAP_DSCP)
  52                 top_iph->tos = 0;
  53         else
  54                 top_iph->tos = XFRM_MODE_SKB_CB(skb)->tos;
  55         top_iph->tos = INET_ECN_encapsulate(top_iph->tos,
  56                                             XFRM_MODE_SKB_CB(skb)->tos);
  57
  58         flags = x->props.flags;
  59         if (flags & XFRM_STATE_NOECN)
  60                 IP_ECN_clear(top_iph);
  61
  62         top_iph->frag_off = (flags & XFRM_STATE_NOPMTUDISC) ?
  63                 0 : (XFRM_MODE_SKB_CB(skb)->frag_off & htons(IP_DF));
  64
  65         top_iph->ttl = ip4_dst_hoplimit(xfrm_dst_child(dst));
  66
  67         top_iph->saddr = x->props.saddr.a4;
  68         top_iph->daddr = x->id.daddr.a4;
  69         ip_select_ident(dev_net(dst->dev), skb, NULL);
  70
  71         return 0;
  72 }
  73
  74 static int xfrm4_mode_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
  75 {
  76         int err = -EINVAL;
  77
  78         if (XFRM_MODE_SKB_CB(skb)->protocol != IPPROTO_IPIP)
  79                 goto out;
  80
  81         if (!pskb_may_pull(skb, sizeof(struct iphdr)))
  82                 goto out;
  83
  84         err = skb_unclone(skb, GFP_ATOMIC);
  85         if (err)
  86                 goto out;
  87
  88         if (x->props.flags & XFRM_STATE_DECAP_DSCP)
  89                 ipv4_copy_dscp(XFRM_MODE_SKB_CB(skb)->tos, ipip_hdr(skb));
  90         if (!(x->props.flags & XFRM_STATE_NOECN))
  91                 ipip_ecn_decapsulate(skb);
  92
  93         skb_reset_network_header(skb);
  94         skb_mac_header_rebuild(skb);
  95         if (skb->mac_len)
  96                 eth_hdr(skb)->h_proto = skb->protocol;
  97
  98         err = 0;
  99
 100 out:
 101         return err;
 102 }
 103
 104 static struct sk_buff *xfrm4_mode_tunnel_gso_segment(struct xfrm_state *x,
 105                                                      struct sk_buff *skb,
 106                                                      netdev_features_t features)
 107 {
 108         __skb_push(skb, skb->mac_len);
 109         return skb_mac_gso_segment(skb, features);
 110 }
 111
 112 static void xfrm4_mode_tunnel_xmit(struct xfrm_state *x, struct sk_buff *skb)
 113 {
 114         struct xfrm_offload *xo = xfrm_offload(skb);
 115
 116         if (xo->flags & XFRM_GSO_SEGMENT)
 117                 skb->transport_header = skb->network_header +
 118                                         sizeof(struct iphdr);
 119
 120         skb_reset_mac_len(skb);
 121         pskb_pull(skb, skb->mac_len + x->props.header_len);
 122 }
 123
 124 static struct xfrm_mode xfrm4_tunnel_mode = {
 125         .input2 = xfrm4_mode_tunnel_input,
 126         .input = xfrm_prepare_input,
 127         .output2 = xfrm4_mode_tunnel_output,
 128         .output = xfrm4_prepare_output,
 129         .gso_segment = xfrm4_mode_tunnel_gso_segment,
 130         .xmit = xfrm4_mode_tunnel_xmit,
 131         .owner = THIS_MODULE,
 132         .encap = XFRM_MODE_TUNNEL,
 133         .flags = XFRM_MODE_FLAG_TUNNEL,
 134 };
 135
 136 static int __init xfrm4_mode_tunnel_init(void)
 137 {
 138         return xfrm_register_mode(&xfrm4_tunnel_mode, AF_INET);
 139 }
 140
 141 static void __exit xfrm4_mode_tunnel_exit(void)
 142 {
 143         int err;
 144
 145         err = xfrm_unregister_mode(&xfrm4_tunnel_mode, AF_INET);
 146         BUG_ON(err);
 147 }
 148
 149 module_init(xfrm4_mode_tunnel_init);
 150 module_exit(xfrm4_mode_tunnel_exit);
 151 MODULE_LICENSE("GPL");
 152 MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_TUNNEL);