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 25 if (IPCB(skb)->flags & IPSKB_XFRM_TUNNEL_SIZE) 26 goto out; 27 28 if (!(ip_hdr(skb)->frag_off & htons(IP_DF)) || skb->ignore_df) 29 goto out; 30 31 mtu = dst_mtu(skb_dst(skb)); 32 if (skb->len > mtu) { 33 skb->protocol = htons(ETH_P_IP); 34 35 if (skb->sk) 36 xfrm_local_error(skb, mtu); 37 else 38 icmp_send(skb, ICMP_DEST_UNREACH, 39 ICMP_FRAG_NEEDED, htonl(mtu)); 40 ret = -EMSGSIZE; 41 } 42 out: 43 return ret; 44 } 45 46 int xfrm4_extract_output(struct xfrm_state *x, struct sk_buff *skb) 47 { 48 int err; 49 50 err = xfrm4_tunnel_check_size(skb); 51 if (err) 52 return err; 53 54 XFRM_MODE_SKB_CB(skb)->protocol = ip_hdr(skb)->protocol; 55 56 return xfrm4_extract_header(skb); 57 } 58 59 int xfrm4_prepare_output(struct xfrm_state *x, struct sk_buff *skb) 60 { 61 int err; 62 63 err = xfrm_inner_extract_output(x, skb); 64 if (err) 65 return err; 66 67 IPCB(skb)->flags |= IPSKB_XFRM_TUNNEL_SIZE; 68 skb->protocol = htons(ETH_P_IP); 69 70 return x->outer_mode->output2(x, skb); 71 } 72 EXPORT_SYMBOL(xfrm4_prepare_output); 73 74 int xfrm4_output_finish(struct sock *sk, struct sk_buff *skb) 75 { 76 memset(IPCB(skb), 0, sizeof(*IPCB(skb))); 77 78 #ifdef CONFIG_NETFILTER 79 IPCB(skb)->flags |= IPSKB_XFRM_TRANSFORMED; 80 #endif 81 82 return xfrm_output(sk, skb); 83 } 84 85 static int __xfrm4_output(struct sock *sk, struct sk_buff *skb) 86 { 87 struct xfrm_state *x = skb_dst(skb)->xfrm; 88 89 #ifdef CONFIG_NETFILTER 90 if (!x) { 91 IPCB(skb)->flags |= IPSKB_REROUTED; 92 return dst_output_sk(sk, skb); 93 } 94 #endif 95 96 return x->outer_mode->afinfo->output_finish(sk, skb); 97 } 98 99 int xfrm4_output(struct sock *sk, struct sk_buff *skb) 100 { 101 return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING, sk, skb, 102 NULL, skb_dst(skb)->dev, __xfrm4_output, 103 !(IPCB(skb)->flags & IPSKB_REROUTED)); 104 } 105 106 void xfrm4_local_error(struct sk_buff *skb, u32 mtu) 107 { 108 struct iphdr *hdr; 109 110 hdr = skb->encapsulation ? inner_ip_hdr(skb) : ip_hdr(skb); 111 ip_local_error(skb->sk, EMSGSIZE, hdr->daddr, 112 inet_sk(skb->sk)->inet_dport, mtu); 113 } 114