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