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         return xfrm4_extract_header(skb);
  51 }
  52
  53 int xfrm4_prepare_output(struct xfrm_state *x, struct sk_buff *skb)
  54 {
  55         int err;
  56
  57         err = x->inner_mode->afinfo->extract_output(x, skb);
  58         if (err)
  59                 return err;
  60
  61         memset(IPCB(skb), 0, sizeof(*IPCB(skb)));
  62         IPCB(skb)->flags |= IPSKB_XFRM_TUNNEL_SIZE;
  63
  64         skb->protocol = htons(ETH_P_IP);
  65
  66         return x->outer_mode->output2(x, skb);
  67 }
  68 EXPORT_SYMBOL(xfrm4_prepare_output);
  69
  70 static inline int xfrm4_output_one(struct sk_buff *skb)
  71 {
  72         struct iphdr *iph;
  73         int err;
  74
  75         err = xfrm_output(skb);
  76         if (err)
  77                 goto error_nolock;
  78
  79         iph = ip_hdr(skb);
  80         iph->tot_len = htons(skb->len);
  81         ip_send_check(iph);
  82
  83         IPCB(skb)->flags |= IPSKB_XFRM_TRANSFORMED;
  84         err = 0;
  85
  86 out_exit:
  87         return err;
  88 error_nolock:
  89         kfree_skb(skb);
  90         goto out_exit;
  91 }
  92
  93 static int xfrm4_output_finish2(struct sk_buff *skb)
  94 {
  95         int err;
  96
  97         while (likely((err = xfrm4_output_one(skb)) == 0)) {
  98                 nf_reset(skb);
  99
 100                 err = nf_hook(PF_INET, NF_IP_LOCAL_OUT, skb, NULL,
 101                               skb->dst->dev, dst_output);
 102                 if (unlikely(err != 1))
 103                         break;
 104
 105                 if (!skb->dst->xfrm)
 106                         return dst_output(skb);
 107
 108                 err = nf_hook(PF_INET, NF_IP_POST_ROUTING, skb, NULL,
 109                               skb->dst->dev, xfrm4_output_finish2);
 110                 if (unlikely(err != 1))
 111                         break;
 112         }
 113
 114         return err;
 115 }
 116
 117 static int xfrm4_output_finish(struct sk_buff *skb)
 118 {
 119         struct sk_buff *segs;
 120
 121 #ifdef CONFIG_NETFILTER
 122         if (!skb->dst->xfrm) {
 123                 IPCB(skb)->flags |= IPSKB_REROUTED;
 124                 return dst_output(skb);
 125         }
 126 #endif
 127
 128         if (!skb_is_gso(skb))
 129                 return xfrm4_output_finish2(skb);
 130
 131         skb->protocol = htons(ETH_P_IP);
 132         segs = skb_gso_segment(skb, 0);
 133         kfree_skb(skb);
 134         if (unlikely(IS_ERR(segs)))
 135                 return PTR_ERR(segs);
 136
 137         do {
 138                 struct sk_buff *nskb = segs->next;
 139                 int err;
 140
 141                 segs->next = NULL;
 142                 err = xfrm4_output_finish2(segs);
 143
 144                 if (unlikely(err)) {
 145                         while ((segs = nskb)) {
 146                                 nskb = segs->next;
 147                                 segs->next = NULL;
 148                                 kfree_skb(segs);
 149                         }
 150                         return err;
 151                 }
 152
 153                 segs = nskb;
 154         } while (segs);
 155
 156         return 0;
 157 }
 158
 159 int xfrm4_output(struct sk_buff *skb)
 160 {
 161         return NF_HOOK_COND(PF_INET, NF_IP_POST_ROUTING, skb, NULL, skb->dst->dev,
 162                             xfrm4_output_finish,
 163                             !(IPCB(skb)->flags & IPSKB_REROUTED));
 164 }