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 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 memset(IPCB(skb), 0, sizeof(*IPCB(skb))); 68 IPCB(skb)->flags |= IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED; 69 70 skb->protocol = htons(ETH_P_IP); 71 72 return x->outer_mode->output2(x, skb); 73 } 74 EXPORT_SYMBOL(xfrm4_prepare_output); 75 76 int xfrm4_output_finish(struct sk_buff *skb) 77 { 78 #ifdef CONFIG_NETFILTER 79 if (!skb_dst(skb)->xfrm) { 80 IPCB(skb)->flags |= IPSKB_REROUTED; 81 return dst_output(skb); 82 } 83 84 IPCB(skb)->flags |= IPSKB_XFRM_TRANSFORMED; 85 #endif 86 87 skb->protocol = htons(ETH_P_IP); 88 return xfrm_output(skb); 89 } 90 91 int xfrm4_output(struct sk_buff *skb) 92 { 93 struct dst_entry *dst = skb_dst(skb); 94 struct xfrm_state *x = dst->xfrm; 95 96 return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING, skb, 97 NULL, dst->dev, 98 x->outer_mode->afinfo->output_finish, 99 !(IPCB(skb)->flags & IPSKB_REROUTED)); 100 } 101 102 void xfrm4_local_error(struct sk_buff *skb, u32 mtu) 103 { 104 struct iphdr *hdr; 105 106 hdr = skb->encapsulation ? inner_ip_hdr(skb) : ip_hdr(skb); 107 ip_local_error(skb->sk, EMSGSIZE, hdr->daddr, 108 inet_sk(skb->sk)->inet_dport, mtu); 109 } 110