1/* 2 * xfrm4_mode_transport.c - Transport 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/ip.h> 14#include <net/xfrm.h> 15 16/* Add encapsulation header. 17 * 18 * The IP header will be moved forward to make space for the encapsulation 19 * header. 20 */ 21static int xfrm4_transport_output(struct xfrm_state *x, struct sk_buff *skb) 22{ 23 struct iphdr *iph = ip_hdr(skb); 24 int ihl = iph->ihl * 4; 25 26 skb_set_network_header(skb, -x->props.header_len); 27 skb->mac_header = skb->network_header + 28 offsetof(struct iphdr, protocol); 29 skb->transport_header = skb->network_header + ihl; 30 __skb_pull(skb, ihl); 31 memmove(skb_network_header(skb), iph, ihl); 32 return 0; 33} 34 35/* Remove encapsulation header. 36 * 37 * The IP header will be moved over the top of the encapsulation header. 38 * 39 * On entry, skb->h shall point to where the IP header should be and skb->nh 40 * shall be set to where the IP header currently is. skb->data shall point 41 * to the start of the payload. 42 */ 43static int xfrm4_transport_input(struct xfrm_state *x, struct sk_buff *skb) 44{ 45 int ihl = skb->data - skb_transport_header(skb); 46 47 if (skb->transport_header != skb->network_header) { 48 memmove(skb_transport_header(skb), 49 skb_network_header(skb), ihl); 50 skb->network_header = skb->transport_header; 51 } 52 ip_hdr(skb)->tot_len = htons(skb->len + ihl); 53 skb_reset_transport_header(skb); 54 return 0; 55} 56 57static struct xfrm_mode xfrm4_transport_mode = { 58 .input = xfrm4_transport_input, 59 .output = xfrm4_transport_output, 60 .owner = THIS_MODULE, 61 .encap = XFRM_MODE_TRANSPORT, 62}; 63 64static int __init xfrm4_transport_init(void) 65{ 66 return xfrm_register_mode(&xfrm4_transport_mode, AF_INET); 67} 68 69static void __exit xfrm4_transport_exit(void) 70{ 71 int err; 72 73 err = xfrm_unregister_mode(&xfrm4_transport_mode, AF_INET); 74 BUG_ON(err); 75} 76 77module_init(xfrm4_transport_init); 78module_exit(xfrm4_transport_exit); 79MODULE_LICENSE("GPL"); 80MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_TRANSPORT); 81