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 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, htonl(mtu)); 36 ret = -EMSGSIZE; 37 } 38 out: 39 return ret; 40 } 41 42 int xfrm4_extract_output(struct xfrm_state *x, struct sk_buff *skb) 43 { 44 int err; 45 46 err = xfrm4_tunnel_check_size(skb); 47 if (err) 48 return err; 49 50 XFRM_MODE_SKB_CB(skb)->protocol = ip_hdr(skb)->protocol; 51 52 return xfrm4_extract_header(skb); 53 } 54 55 int xfrm4_prepare_output(struct xfrm_state *x, struct sk_buff *skb) 56 { 57 int err; 58 59 err = xfrm_inner_extract_output(x, skb); 60 if (err) 61 return err; 62 63 memset(IPCB(skb), 0, sizeof(*IPCB(skb))); 64 IPCB(skb)->flags |= IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED; 65 66 skb->protocol = htons(ETH_P_IP); 67 68 return x->outer_mode->output2(x, skb); 69 } 70 EXPORT_SYMBOL(xfrm4_prepare_output); 71 72 static int xfrm4_output_finish(struct sk_buff *skb) 73 { 74 #ifdef CONFIG_NETFILTER 75 if (!skb_dst(skb)->xfrm) { 76 IPCB(skb)->flags |= IPSKB_REROUTED; 77 return dst_output(skb); 78 } 79 80 IPCB(skb)->flags |= IPSKB_XFRM_TRANSFORMED; 81 #endif 82 83 skb->protocol = htons(ETH_P_IP); 84 return xfrm_output(skb); 85 } 86 87 int xfrm4_output(struct sk_buff *skb) 88 { 89 return NF_HOOK_COND(PF_INET, NF_INET_POST_ROUTING, skb, 90 NULL, skb_dst(skb)->dev, xfrm4_output_finish, 91 !(IPCB(skb)->flags & IPSKB_REROUTED)); 92 } 93