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_is_gso(skb) && skb->len > mtu) ||
  33             (skb_is_gso(skb) && skb_gso_network_seglen(skb) > ip_skb_dst_mtu(skb->sk, skb))) {
  34                 skb->protocol = htons(ETH_P_IP);
  35
  36                 if (skb->sk)
  37                         xfrm_local_error(skb, 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         IPCB(skb)->flags |= IPSKB_XFRM_TUNNEL_SIZE;
  69         skb->protocol = htons(ETH_P_IP);
  70
  71         return x->outer_mode->output2(x, skb);
  72 }
  73 EXPORT_SYMBOL(xfrm4_prepare_output);
  74
  75 int xfrm4_output_finish(struct sock *sk, struct sk_buff *skb)
  76 {
  77         memset(IPCB(skb), 0, sizeof(*IPCB(skb)));
  78
  79 #ifdef CONFIG_NETFILTER
  80         IPCB(skb)->flags |= IPSKB_XFRM_TRANSFORMED;
  81 #endif
  82
  83         return xfrm_output(sk, skb);
  84 }
  85
  86 static int __xfrm4_output(struct net *net, struct sock *sk, struct sk_buff *skb)
  87 {
  88         struct xfrm_state *x = skb_dst(skb)->xfrm;
  89
  90 #ifdef CONFIG_NETFILTER
  91         if (!x) {
  92                 IPCB(skb)->flags |= IPSKB_REROUTED;
  93                 return dst_output(net, sk, skb);
  94         }
  95 #endif
  96
  97         return x->outer_mode->afinfo->output_finish(sk, skb);
  98 }
  99
 100 int xfrm4_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 101 {
 102         return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING,
 103                             net, sk, skb, NULL, skb_dst(skb)->dev,
 104                             __xfrm4_output,
 105                             !(IPCB(skb)->flags & IPSKB_REROUTED));
 106 }
 107
 108 void xfrm4_local_error(struct sk_buff *skb, u32 mtu)
 109 {
 110         struct iphdr *hdr;
 111
 112         hdr = skb->encapsulation ? inner_ip_hdr(skb) : ip_hdr(skb);
 113         ip_local_error(skb->sk, EMSGSIZE, hdr->daddr,
 114                        inet_sk(skb->sk)->inet_dport, mtu);
 115 }