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         int err;
  73
  74         err = xfrm_output(skb);
  75         if (err)
  76                 goto error_nolock;
  77
  78         IPCB(skb)->flags |= IPSKB_XFRM_TRANSFORMED;
  79         err = 0;
  80
  81 out_exit:
  82         return err;
  83 error_nolock:
  84         kfree_skb(skb);
  85         goto out_exit;
  86 }
  87
  88 static int xfrm4_output_finish2(struct sk_buff *skb)
  89 {
  90         int err;
  91
  92         while (likely((err = xfrm4_output_one(skb)) == 0)) {
  93                 nf_reset(skb);
  94
  95                 err = __ip_local_out(skb);
  96                 if (unlikely(err != 1))
  97                         break;
  98
  99                 if (!skb->dst->xfrm)
 100                         return dst_output(skb);
 101
 102                 err = nf_hook(PF_INET, NF_IP_POST_ROUTING, skb, NULL,
 103                               skb->dst->dev, xfrm4_output_finish2);
 104                 if (unlikely(err != 1))
 105                         break;
 106         }
 107
 108         return err;
 109 }
 110
 111 static int xfrm4_output_finish(struct sk_buff *skb)
 112 {
 113         struct sk_buff *segs;
 114
 115 #ifdef CONFIG_NETFILTER
 116         if (!skb->dst->xfrm) {
 117                 IPCB(skb)->flags |= IPSKB_REROUTED;
 118                 return dst_output(skb);
 119         }
 120 #endif
 121
 122         if (!skb_is_gso(skb))
 123                 return xfrm4_output_finish2(skb);
 124
 125         skb->protocol = htons(ETH_P_IP);
 126         segs = skb_gso_segment(skb, 0);
 127         kfree_skb(skb);
 128         if (unlikely(IS_ERR(segs)))
 129                 return PTR_ERR(segs);
 130
 131         do {
 132                 struct sk_buff *nskb = segs->next;
 133                 int err;
 134
 135                 segs->next = NULL;
 136                 err = xfrm4_output_finish2(segs);
 137
 138                 if (unlikely(err)) {
 139                         while ((segs = nskb)) {
 140                                 nskb = segs->next;
 141                                 segs->next = NULL;
 142                                 kfree_skb(segs);
 143                         }
 144                         return err;
 145                 }
 146
 147                 segs = nskb;
 148         } while (segs);
 149
 150         return 0;
 151 }
 152
 153 int xfrm4_output(struct sk_buff *skb)
 154 {
 155         return NF_HOOK_COND(PF_INET, NF_IP_POST_ROUTING, skb, NULL, skb->dst->dev,
 156                             xfrm4_output_finish,
 157                             !(IPCB(skb)->flags & IPSKB_REROUTED));
 158 }