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) &&
  34              !skb_gso_validate_network_len(skb, ip_skb_dst_mtu(skb->sk, skb)))) {
  35                 skb->protocol = htons(ETH_P_IP);
  36
  37                 if (skb->sk)
  38                         xfrm_local_error(skb, mtu);
  39                 else
  40                         icmp_send(skb, ICMP_DEST_UNREACH,
  41                                   ICMP_FRAG_NEEDED, htonl(mtu));
  42                 ret = -EMSGSIZE;
  43         }
  44 out:
  45         return ret;
  46 }
  47
  48 int xfrm4_extract_output(struct xfrm_state *x, struct sk_buff *skb)
  49 {
  50         int err;
  51
  52         err = xfrm4_tunnel_check_size(skb);
  53         if (err)
  54                 return err;
  55
  56         XFRM_MODE_SKB_CB(skb)->protocol = ip_hdr(skb)->protocol;
  57
  58         return xfrm4_extract_header(skb);
  59 }
  60
  61 int xfrm4_prepare_output(struct xfrm_state *x, struct sk_buff *skb)
  62 {
  63         int err;
  64
  65         err = xfrm_inner_extract_output(x, skb);
  66         if (err)
  67                 return err;
  68
  69         IPCB(skb)->flags |= IPSKB_XFRM_TUNNEL_SIZE;
  70         skb->protocol = htons(ETH_P_IP);
  71
  72         return x->outer_mode->output2(x, skb);
  73 }
  74 EXPORT_SYMBOL(xfrm4_prepare_output);
  75
  76 int xfrm4_output_finish(struct sock *sk, struct sk_buff *skb)
  77 {
  78         memset(IPCB(skb), 0, sizeof(*IPCB(skb)));
  79
  80 #ifdef CONFIG_NETFILTER
  81         IPCB(skb)->flags |= IPSKB_XFRM_TRANSFORMED;
  82 #endif
  83
  84         return xfrm_output(sk, skb);
  85 }
  86
  87 static int __xfrm4_output(struct net *net, struct sock *sk, struct sk_buff *skb)
  88 {
  89         struct xfrm_state *x = skb_dst(skb)->xfrm;
  90
  91 #ifdef CONFIG_NETFILTER
  92         if (!x) {
  93                 IPCB(skb)->flags |= IPSKB_REROUTED;
  94                 return dst_output(net, sk, skb);
  95         }
  96 #endif
  97
  98         return x->outer_mode->afinfo->output_finish(sk, skb);
  99 }
 100
 101 int xfrm4_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 102 {
 103         return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING,
 104                             net, sk, skb, NULL, skb_dst(skb)->dev,
 105                             __xfrm4_output,
 106                             !(IPCB(skb)->flags & IPSKB_REROUTED));
 107 }
 108
 109 void xfrm4_local_error(struct sk_buff *skb, u32 mtu)
 110 {
 111         struct iphdr *hdr;
 112
 113         hdr = skb->encapsulation ? inner_ip_hdr(skb) : ip_hdr(skb);
 114         ip_local_error(skb->sk, EMSGSIZE, hdr->daddr,
 115                        inet_sk(skb->sk)->inet_dport, mtu);
 116 }