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/compiler.h>
  12 #include <linux/skbuff.h>
  13 #include <linux/spinlock.h>
  14 #include <linux/netfilter_ipv4.h>
  15 #include <net/ip.h>
  16 #include <net/xfrm.h>
  17 #include <net/icmp.h>
  18
  19 static int xfrm4_tunnel_check_size(struct sk_buff *skb)
  20 {
  21         int mtu, ret = 0;
  22         struct dst_entry *dst;
  23         struct iphdr *iph = skb->nh.iph;
  24
  25         if (IPCB(skb)->flags & IPSKB_XFRM_TUNNEL_SIZE)
  26                 goto out;
  27
  28         IPCB(skb)->flags |= IPSKB_XFRM_TUNNEL_SIZE;
  29
  30         if (!(iph->frag_off & htons(IP_DF)) || skb->local_df)
  31                 goto out;
  32
  33         dst = skb->dst;
  34         mtu = dst_mtu(dst);
  35         if (skb->len > mtu) {
  36                 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, htonl(mtu));
  37                 ret = -EMSGSIZE;
  38         }
  39 out:
  40         return ret;
  41 }
  42
  43 static int xfrm4_output_one(struct sk_buff *skb)
  44 {
  45         struct dst_entry *dst = skb->dst;
  46         struct xfrm_state *x = dst->xfrm;
  47         int err;
  48
  49         if (skb->ip_summed == CHECKSUM_HW) {
  50                 err = skb_checksum_help(skb, 0);
  51                 if (err)
  52                         goto error_nolock;
  53         }
  54
  55         if (x->props.mode) {
  56                 err = xfrm4_tunnel_check_size(skb);
  57                 if (err)
  58                         goto error_nolock;
  59         }
  60
  61         do {
  62                 spin_lock_bh(&x->lock);
  63                 err = xfrm_state_check(x, skb);
  64                 if (err)
  65                         goto error;
  66
  67                 err = x->mode->output(skb);
  68                 if (err)
  69                         goto error;
  70
  71                 err = x->type->output(x, skb);
  72                 if (err)
  73                         goto error;
  74
  75                 x->curlft.bytes += skb->len;
  76                 x->curlft.packets++;
  77
  78                 spin_unlock_bh(&x->lock);
  79
  80                 if (!(skb->dst = dst_pop(dst))) {
  81                         err = -EHOSTUNREACH;
  82                         goto error_nolock;
  83                 }
  84                 dst = skb->dst;
  85                 x = dst->xfrm;
  86         } while (x && !x->props.mode);
  87
  88         IPCB(skb)->flags |= IPSKB_XFRM_TRANSFORMED;
  89         err = 0;
  90
  91 out_exit:
  92         return err;
  93 error:
  94         spin_unlock_bh(&x->lock);
  95 error_nolock:
  96         kfree_skb(skb);
  97         goto out_exit;
  98 }
  99
 100 static int xfrm4_output_finish(struct sk_buff *skb)
 101 {
 102         int err;
 103
 104 #ifdef CONFIG_NETFILTER
 105         if (!skb->dst->xfrm) {
 106                 IPCB(skb)->flags |= IPSKB_REROUTED;
 107                 return dst_output(skb);
 108         }
 109 #endif
 110         while (likely((err = xfrm4_output_one(skb)) == 0)) {
 111                 nf_reset(skb);
 112
 113                 err = nf_hook(PF_INET, NF_IP_LOCAL_OUT, &skb, NULL,
 114                               skb->dst->dev, dst_output);
 115                 if (unlikely(err != 1))
 116                         break;
 117
 118                 if (!skb->dst->xfrm)
 119                         return dst_output(skb);
 120
 121                 err = nf_hook(PF_INET, NF_IP_POST_ROUTING, &skb, NULL,
 122                               skb->dst->dev, xfrm4_output_finish);
 123                 if (unlikely(err != 1))
 124                         break;
 125         }
 126
 127         return err;
 128 }
 129
 130 int xfrm4_output(struct sk_buff *skb)
 131 {
 132         return NF_HOOK_COND(PF_INET, NF_IP_POST_ROUTING, skb, NULL, skb->dst->dev,
 133                             xfrm4_output_finish,
 134                             !(IPCB(skb)->flags & IPSKB_REROUTED));
 135 }