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 18static 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 */ 30static 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 disclosed */ 48 top_iph->tos = INET_ECN_encapsulate(XFRM_MODE_SKB_CB(skb)->tos, 49 XFRM_MODE_SKB_CB(skb)->tos); 50 51 flags = x->props.flags; 52 if (flags & XFRM_STATE_NOECN) 53 IP_ECN_clear(top_iph); 54 55 top_iph->frag_off = (flags & XFRM_STATE_NOPMTUDISC) ? 56 0 : (XFRM_MODE_SKB_CB(skb)->frag_off & htons(IP_DF)); 57 ip_select_ident(top_iph, dst->child, NULL); 58 59 top_iph->ttl = dst_metric(dst->child, RTAX_HOPLIMIT); 60 61 top_iph->saddr = x->props.saddr.a4; 62 top_iph->daddr = x->id.daddr.a4; 63 64 return 0; 65} 66 67static int xfrm4_mode_tunnel_input(struct xfrm_state *x, struct sk_buff *skb) 68{ 69 const unsigned char *old_mac; 70 int err = -EINVAL; 71 72 if (XFRM_MODE_SKB_CB(skb)->protocol != IPPROTO_IPIP) 73 goto out; 74 75 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 76 goto out; 77 78 if (skb_cloned(skb) && 79 (err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC))) 80 goto out; 81 82 if (x->props.flags & XFRM_STATE_DECAP_DSCP) 83 ipv4_copy_dscp(XFRM_MODE_SKB_CB(skb)->tos, ipip_hdr(skb)); 84 if (!(x->props.flags & XFRM_STATE_NOECN)) 85 ipip_ecn_decapsulate(skb); 86 87 old_mac = skb_mac_header(skb); 88 skb_set_mac_header(skb, -skb->mac_len); 89 memmove(skb_mac_header(skb), old_mac, skb->mac_len); 90 skb_reset_network_header(skb); 91 err = 0; 92 93out: 94 return err; 95} 96 97static struct xfrm_mode xfrm4_tunnel_mode = { 98 .input2 = xfrm4_mode_tunnel_input, 99 .input = xfrm_prepare_input, 100 .output2 = xfrm4_mode_tunnel_output, 101 .output = xfrm4_prepare_output, 102 .owner = THIS_MODULE, 103 .encap = XFRM_MODE_TUNNEL, 104 .flags = XFRM_MODE_FLAG_TUNNEL, 105}; 106 107static int __init xfrm4_mode_tunnel_init(void) 108{ 109 return xfrm_register_mode(&xfrm4_tunnel_mode, AF_INET); 110} 111 112static void __exit xfrm4_mode_tunnel_exit(void) 113{ 114 int err; 115 116 err = xfrm_unregister_mode(&xfrm4_tunnel_mode, AF_INET); 117 BUG_ON(err); 118} 119 120module_init(xfrm4_mode_tunnel_init); 121module_exit(xfrm4_mode_tunnel_exit); 122MODULE_LICENSE("GPL"); 123MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_TUNNEL); 124