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 * 21 * On exit, skb->h will be set to the start of the payload to be processed 22 * by x->type->output and skb->nh will be set to the top IP header. 23 */ 24static int xfrm4_transport_output(struct xfrm_state *x, struct sk_buff *skb) 25{ 26 struct iphdr *iph = ip_hdr(skb); 27 int ihl = iph->ihl * 4; 28 29 skb->transport_header = skb->network_header + ihl; 30 skb_push(skb, x->props.header_len); 31 skb_reset_network_header(skb); 32 memmove(skb_network_header(skb), iph, ihl); 33 return 0; 34} 35 36/* Remove encapsulation header. 37 * 38 * The IP header will be moved over the top of the encapsulation header. 39 * 40 * On entry, skb->h shall point to where the IP header should be and skb->nh 41 * shall be set to where the IP header currently is. skb->data shall point 42 * to the start of the payload. 43 */ 44static int xfrm4_transport_input(struct xfrm_state *x, struct sk_buff *skb) 45{ 46 int ihl = skb->data - skb_transport_header(skb); 47 48 if (skb->transport_header != skb->network_header) { 49 memmove(skb_transport_header(skb), 50 skb_network_header(skb), ihl); 51 skb->network_header = skb->transport_header; 52 } 53 ip_hdr(skb)->tot_len = htons(skb->len + ihl); 54 skb_reset_transport_header(skb); 55 return 0; 56} 57 58static struct xfrm_mode xfrm4_transport_mode = { 59 .input = xfrm4_transport_input, 60 .output = xfrm4_transport_output, 61 .owner = THIS_MODULE, 62 .encap = XFRM_MODE_TRANSPORT, 63}; 64 65static int __init xfrm4_transport_init(void) 66{ 67 return xfrm_register_mode(&xfrm4_transport_mode, AF_INET); 68} 69 70static void __exit xfrm4_transport_exit(void) 71{ 72 int err; 73 74 err = xfrm_unregister_mode(&xfrm4_transport_mode, AF_INET); 75 BUG_ON(err); 76} 77 78module_init(xfrm4_transport_init); 79module_exit(xfrm4_transport_exit); 80MODULE_LICENSE("GPL"); 81MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_TRANSPORT); 82