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