| 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_network_header(skb, -x->props.header_len); |
| 37 | skb->mac_header = skb->network_header + |
| 38 | offsetof(struct iphdr, protocol); |
| 39 | skb->transport_header = skb->network_header + sizeof(*top_iph); |
| 40 | top_iph = ip_hdr(skb); |
| 41 | |
| 42 | top_iph->ihl = 5; |
| 43 | top_iph->version = 4; |
| 44 | |
| 45 | top_iph->protocol = xfrm_af2proto(skb_dst(skb)->ops->family); |
| 46 | |
| 47 | /* DS disclosing depends on XFRM_SA_XFLAG_DONT_ENCAP_DSCP */ |
| 48 | if (x->props.extra_flags & XFRM_SA_XFLAG_DONT_ENCAP_DSCP) |
| 49 | top_iph->tos = 0; |
| 50 | else |
| 51 | top_iph->tos = XFRM_MODE_SKB_CB(skb)->tos; |
| 52 | top_iph->tos = INET_ECN_encapsulate(top_iph->tos, |
| 53 | XFRM_MODE_SKB_CB(skb)->tos); |
| 54 | |
| 55 | flags = x->props.flags; |
| 56 | if (flags & XFRM_STATE_NOECN) |
| 57 | IP_ECN_clear(top_iph); |
| 58 | |
| 59 | top_iph->frag_off = (flags & XFRM_STATE_NOPMTUDISC) ? |
| 60 | 0 : (XFRM_MODE_SKB_CB(skb)->frag_off & htons(IP_DF)); |
| 61 | |
| 62 | top_iph->ttl = ip4_dst_hoplimit(dst->child); |
| 63 | |
| 64 | top_iph->saddr = x->props.saddr.a4; |
| 65 | top_iph->daddr = x->id.daddr.a4; |
| 66 | ip_select_ident(dev_net(dst->dev), skb, NULL); |
| 67 | |
| 68 | return 0; |
| 69 | } |
| 70 | |
| 71 | static int xfrm4_mode_tunnel_input(struct xfrm_state *x, struct sk_buff *skb) |
| 72 | { |
| 73 | int err = -EINVAL; |
| 74 | |
| 75 | if (XFRM_MODE_SKB_CB(skb)->protocol != IPPROTO_IPIP) |
| 76 | goto out; |
| 77 | |
| 78 | if (!pskb_may_pull(skb, sizeof(struct iphdr))) |
| 79 | goto out; |
| 80 | |
| 81 | err = skb_unclone(skb, GFP_ATOMIC); |
| 82 | if (err) |
| 83 | goto out; |
| 84 | |
| 85 | if (x->props.flags & XFRM_STATE_DECAP_DSCP) |
| 86 | ipv4_copy_dscp(XFRM_MODE_SKB_CB(skb)->tos, ipip_hdr(skb)); |
| 87 | if (!(x->props.flags & XFRM_STATE_NOECN)) |
| 88 | ipip_ecn_decapsulate(skb); |
| 89 | |
| 90 | skb_reset_network_header(skb); |
| 91 | skb_mac_header_rebuild(skb); |
| 92 | |
| 93 | err = 0; |
| 94 | |
| 95 | out: |
| 96 | return err; |
| 97 | } |
| 98 | |
| 99 | static struct xfrm_mode xfrm4_tunnel_mode = { |
| 100 | .input2 = xfrm4_mode_tunnel_input, |
| 101 | .input = xfrm_prepare_input, |
| 102 | .output2 = xfrm4_mode_tunnel_output, |
| 103 | .output = xfrm4_prepare_output, |
| 104 | .owner = THIS_MODULE, |
| 105 | .encap = XFRM_MODE_TUNNEL, |
| 106 | .flags = XFRM_MODE_FLAG_TUNNEL, |
| 107 | }; |
| 108 | |
| 109 | static int __init xfrm4_mode_tunnel_init(void) |
| 110 | { |
| 111 | return xfrm_register_mode(&xfrm4_tunnel_mode, AF_INET); |
| 112 | } |
| 113 | |
| 114 | static void __exit xfrm4_mode_tunnel_exit(void) |
| 115 | { |
| 116 | int err; |
| 117 | |
| 118 | err = xfrm_unregister_mode(&xfrm4_tunnel_mode, AF_INET); |
| 119 | BUG_ON(err); |
| 120 | } |
| 121 | |
| 122 | module_init(xfrm4_mode_tunnel_init); |
| 123 | module_exit(xfrm4_mode_tunnel_exit); |
| 124 | MODULE_LICENSE("GPL"); |
| 125 | MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_TUNNEL); |