net/ipv4/xfrm4_output.c

   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 net *net, 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(net, sk, skb);
  93         }
  94 #endif
  95
  96         return x->outer_mode->afinfo->output_finish(sk, skb);
  97 }
  98
  99 int xfrm4_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 100 {
 101         return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING,
 102                             net, sk, skb, NULL, skb_dst(skb)->dev,
 103                             __xfrm4_output,
 104                             !(IPCB(skb)->flags & IPSKB_REROUTED));
 105 }
 106
 107 void xfrm4_local_error(struct sk_buff *skb, u32 mtu)
 108 {
 109         struct iphdr *hdr;
 110
 111         hdr = skb->encapsulation ? inner_ip_hdr(skb) : ip_hdr(skb);
 112         ip_local_error(skb->sk, EMSGSIZE, hdr->daddr,
 113                        inet_sk(skb->sk)->inet_dport, mtu);
 114 }