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