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;
  33         mtu = dst_mtu(dst);
  34         if (skb->len > mtu) {
  35                 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, htonl(mtu));
  36                 ret = -EMSGSIZE;
  37         }
  38 out:
  39         return ret;
  40 }
  41
  42 int xfrm4_extract_output(struct xfrm_state *x, struct sk_buff *skb)
  43 {
  44         int err;
  45
  46         err = xfrm4_tunnel_check_size(skb);
  47         if (err)
  48                 return err;
  49
  50         XFRM_MODE_SKB_CB(skb)->protocol = ip_hdr(skb)->protocol;
  51
  52         return xfrm4_extract_header(skb);
  53 }
  54
  55 int xfrm4_prepare_output(struct xfrm_state *x, struct sk_buff *skb)
  56 {
  57         int err;
  58
  59         err = x->inner_mode->afinfo->extract_output(x, skb);
  60         if (err)
  61                 return err;
  62
  63         memset(IPCB(skb), 0, sizeof(*IPCB(skb)));
  64         IPCB(skb)->flags |= IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED;
  65
  66         skb->protocol = htons(ETH_P_IP);
  67
  68         return x->outer_mode->output2(x, skb);
  69 }
  70 EXPORT_SYMBOL(xfrm4_prepare_output);
  71
  72 static int xfrm4_output_finish(struct sk_buff *skb)
  73 {
  74 #ifdef CONFIG_NETFILTER
  75         if (!skb->dst->xfrm) {
  76                 IPCB(skb)->flags |= IPSKB_REROUTED;
  77                 return dst_output(skb);
  78         }
  79
  80         IPCB(skb)->flags |= IPSKB_XFRM_TRANSFORMED;
  81 #endif
  82
  83         skb->protocol = htons(ETH_P_IP);
  84         return xfrm_output(skb);
  85 }
  86
  87 int xfrm4_output(struct sk_buff *skb)
  88 {
  89         return NF_HOOK_COND(PF_INET, NF_INET_POST_ROUTING, skb,
  90                             NULL, skb->dst->dev, xfrm4_output_finish,
  91                             !(IPCB(skb)->flags & IPSKB_REROUTED));
  92 }