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_is_gso(skb) && skb->len > mtu) || 33 (skb_is_gso(skb) && skb_gso_network_seglen(skb) > ip_skb_dst_mtu(skb->sk, skb))) { 34 skb->protocol = htons(ETH_P_IP); 35 36 if (skb->sk) 37 xfrm_local_error(skb, 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 IPCB(skb)->flags |= IPSKB_XFRM_TUNNEL_SIZE; 69 skb->protocol = htons(ETH_P_IP); 70 71 return x->outer_mode->output2(x, skb); 72 } 73 EXPORT_SYMBOL(xfrm4_prepare_output); 74 75 int xfrm4_output_finish(struct sock *sk, struct sk_buff *skb) 76 { 77 memset(IPCB(skb), 0, sizeof(*IPCB(skb))); 78 79 #ifdef CONFIG_NETFILTER 80 IPCB(skb)->flags |= IPSKB_XFRM_TRANSFORMED; 81 #endif 82 83 return xfrm_output(sk, skb); 84 } 85 86 static int __xfrm4_output(struct net *net, struct sock *sk, struct sk_buff *skb) 87 { 88 struct xfrm_state *x = skb_dst(skb)->xfrm; 89 90 #ifdef CONFIG_NETFILTER 91 if (!x) { 92 IPCB(skb)->flags |= IPSKB_REROUTED; 93 return dst_output(net, sk, skb); 94 } 95 #endif 96 97 return x->outer_mode->afinfo->output_finish(sk, skb); 98 } 99 100 int xfrm4_output(struct net *net, struct sock *sk, struct sk_buff *skb) 101 { 102 return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING, 103 net, sk, skb, NULL, skb_dst(skb)->dev, 104 __xfrm4_output, 105 !(IPCB(skb)->flags & IPSKB_REROUTED)); 106 } 107 108 void xfrm4_local_error(struct sk_buff *skb, u32 mtu) 109 { 110 struct iphdr *hdr; 111 112 hdr = skb->encapsulation ? inner_ip_hdr(skb) : ip_hdr(skb); 113 ip_local_error(skb->sk, EMSGSIZE, hdr->daddr, 114 inet_sk(skb->sk)->inet_dport, mtu); 115 } 116