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                 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         IPCB(skb)->flags |= IPSKB_XFRM_TUNNEL_SIZE;
  66
  67         return x->outer_mode->output2(x, skb);
  68 }
  69 EXPORT_SYMBOL(xfrm4_prepare_output);
  70
  71 int xfrm4_output_finish(struct sk_buff *skb)
  72 {
  73         memset(IPCB(skb), 0, sizeof(*IPCB(skb)));
  74         skb->protocol = htons(ETH_P_IP);
  75
  76 #ifdef CONFIG_NETFILTER
  77         IPCB(skb)->flags |= IPSKB_XFRM_TRANSFORMED;
  78 #endif
  79
  80         return xfrm_output(skb);
  81 }
  82
  83 static int __xfrm4_output(struct sk_buff *skb)
  84 {
  85         struct xfrm_state *x = skb_dst(skb)->xfrm;
  86
  87 #ifdef CONFIG_NETFILTER
  88         if (!x) {
  89                 IPCB(skb)->flags |= IPSKB_REROUTED;
  90                 return dst_output(skb);
  91         }
  92 #endif
  93
  94         return x->outer_mode->afinfo->output_finish(skb);
  95 }
  96
  97 int xfrm4_output(struct sock *sk, struct sk_buff *skb)
  98 {
  99         return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING, skb,
 100                             NULL, skb_dst(skb)->dev, __xfrm4_output,
 101                             !(IPCB(skb)->flags & IPSKB_REROUTED));
 102 }
 103
 104 void xfrm4_local_error(struct sk_buff *skb, u32 mtu)
 105 {
 106         struct iphdr *hdr;
 107
 108         hdr = skb->encapsulation ? inner_ip_hdr(skb) : ip_hdr(skb);
 109         ip_local_error(skb->sk, EMSGSIZE, hdr->daddr,
 110                        inet_sk(skb->sk)->inet_dport, mtu);
 111 }