1 /* 2 * xfrm4_output.c - Common IPsec encapsulation code for IPv4. 3 * Copyright (c) 2004 Herbert Xu <herbert@gondor.apana.org.au> 4 * 5 * This program is free software; you can redistribute it and/or 6 * modify it under the terms of the GNU General Public License 7 * as published by the Free Software Foundation; either version 8 * 2 of the License, or (at your option) any later version. 9 */ 10 11 #include <linux/if_ether.h> 12 #include <linux/kernel.h> 13 #include <linux/module.h> 14 #include <linux/skbuff.h> 15 #include <linux/netfilter_ipv4.h> 16 #include <net/dst.h> 17 #include <net/ip.h> 18 #include <net/xfrm.h> 19 #include <net/icmp.h> 20 21 static int xfrm4_tunnel_check_size(struct sk_buff *skb) 22 { 23 int mtu, ret = 0; 24 struct dst_entry *dst; 25 26 if (IPCB(skb)->flags & IPSKB_XFRM_TUNNEL_SIZE) 27 goto out; 28 29 if (!(ip_hdr(skb)->frag_off & htons(IP_DF)) || skb->local_df) 30 goto out; 31 32 dst = skb_dst(skb); 33 mtu = dst_mtu(dst); 34 if (skb->len > mtu) { 35 if (skb->sk) 36 ip_local_error(skb->sk, EMSGSIZE, ip_hdr(skb)->daddr, 37 inet_sk(skb->sk)->inet_dport, mtu); 38 else 39 icmp_send(skb, ICMP_DEST_UNREACH, 40 ICMP_FRAG_NEEDED, htonl(mtu)); 41 ret = -EMSGSIZE; 42 } 43 out: 44 return ret; 45 } 46 47 int xfrm4_extract_output(struct xfrm_state *x, struct sk_buff *skb) 48 { 49 int err; 50 51 err = xfrm4_tunnel_check_size(skb); 52 if (err) 53 return err; 54 55 XFRM_MODE_SKB_CB(skb)->protocol = ip_hdr(skb)->protocol; 56 57 return xfrm4_extract_header(skb); 58 } 59 60 int xfrm4_prepare_output(struct xfrm_state *x, struct sk_buff *skb) 61 { 62 int err; 63 64 err = xfrm_inner_extract_output(x, skb); 65 if (err) 66 return err; 67 68 memset(IPCB(skb), 0, sizeof(*IPCB(skb))); 69 IPCB(skb)->flags |= IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED; 70 71 skb->protocol = htons(ETH_P_IP); 72 73 return x->outer_mode->output2(x, skb); 74 } 75 EXPORT_SYMBOL(xfrm4_prepare_output); 76 77 int xfrm4_output_finish(struct sk_buff *skb) 78 { 79 #ifdef CONFIG_NETFILTER 80 if (!skb_dst(skb)->xfrm) { 81 IPCB(skb)->flags |= IPSKB_REROUTED; 82 return dst_output(skb); 83 } 84 85 IPCB(skb)->flags |= IPSKB_XFRM_TRANSFORMED; 86 #endif 87 88 skb->protocol = htons(ETH_P_IP); 89 return xfrm_output(skb); 90 } 91 92 int xfrm4_output(struct sk_buff *skb) 93 { 94 struct dst_entry *dst = skb_dst(skb); 95 struct xfrm_state *x = dst->xfrm; 96 97 return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING, skb, 98 NULL, dst->dev, 99 x->outer_mode->afinfo->output_finish, 100 !(IPCB(skb)->flags & IPSKB_REROUTED)); 101 } 102