net/ipv6/xfrm6_output.c

   1 /*
   2  * xfrm6_output.c - Common IPsec encapsulation code for IPv6.
   3  * Copyright (C) 2002 USAGI/WIDE Project
   4  * Copyright (c) 2004 Herbert Xu <herbert@gondor.apana.org.au>
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  */
  11
  12 #include <linux/compiler.h>
  13 #include <linux/skbuff.h>
  14 #include <linux/spinlock.h>
  15 #include <linux/icmpv6.h>
  16 #include <linux/netfilter_ipv6.h>
  17 #include <net/dsfield.h>
  18 #include <net/inet_ecn.h>
  19 #include <net/ipv6.h>
  20 #include <net/xfrm.h>
  21
  22 /* Add encapsulation header.
  23  *
  24  * In transport mode, the IP header and mutable extension headers will be moved
  25  * forward to make space for the encapsulation header.
  26  *
  27  * In tunnel mode, the top IP header will be constructed per RFC 2401.
  28  * The following fields in it shall be filled in by x->type->output:
  29  *      payload_len
  30  *
  31  * On exit, skb->h will be set to the start of the encapsulation header to be
  32  * filled in by x->type->output and skb->nh will be set to the nextheader field
  33  * of the extension header directly preceding the encapsulation header, or in
  34  * its absence, that of the top IP header.  The value of skb->data will always
  35  * point to the top IP header.
  36  */
  37 static void xfrm6_encap(struct sk_buff *skb)
  38 {
  39         struct dst_entry *dst = skb->dst;
  40         struct xfrm_state *x = dst->xfrm;
  41         struct ipv6hdr *iph, *top_iph;
  42         int dsfield;
  43
  44         skb_push(skb, x->props.header_len);
  45         iph = skb->nh.ipv6h;
  46
  47         if (!x->props.mode) {
  48                 u8 *prevhdr;
  49                 int hdr_len;
  50
  51                 hdr_len = ip6_find_1stfragopt(skb, &prevhdr);
  52                 skb->nh.raw = prevhdr - x->props.header_len;
  53                 skb->h.raw = skb->data + hdr_len;
  54                 memmove(skb->data, iph, hdr_len);
  55                 return;
  56         }
  57
  58         skb->nh.raw = skb->data;
  59         top_iph = skb->nh.ipv6h;
  60         skb->nh.raw = &top_iph->nexthdr;
  61         skb->h.ipv6h = top_iph + 1;
  62
  63         top_iph->version = 6;
  64         top_iph->priority = iph->priority;
  65         top_iph->flow_lbl[0] = iph->flow_lbl[0];
  66         top_iph->flow_lbl[1] = iph->flow_lbl[1];
  67         top_iph->flow_lbl[2] = iph->flow_lbl[2];
  68         dsfield = ipv6_get_dsfield(top_iph);
  69         dsfield = INET_ECN_encapsulate(dsfield, dsfield);
  70         if (x->props.flags & XFRM_STATE_NOECN)
  71                 dsfield &= ~INET_ECN_MASK;
  72         ipv6_change_dsfield(top_iph, 0, dsfield);
  73         top_iph->nexthdr = IPPROTO_IPV6;
  74         top_iph->hop_limit = dst_metric(dst->child, RTAX_HOPLIMIT);
  75         ipv6_addr_copy(&top_iph->saddr, (struct in6_addr *)&x->props.saddr);
  76         ipv6_addr_copy(&top_iph->daddr, (struct in6_addr *)&x->id.daddr);
  77 }
  78
  79 static int xfrm6_tunnel_check_size(struct sk_buff *skb)
  80 {
  81         int mtu, ret = 0;
  82         struct dst_entry *dst = skb->dst;
  83
  84         mtu = dst_mtu(dst);
  85         if (mtu < IPV6_MIN_MTU)
  86                 mtu = IPV6_MIN_MTU;
  87
  88         if (skb->len > mtu) {
  89                 skb->dev = dst->dev;
  90                 icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu, skb->dev);
  91                 ret = -EMSGSIZE;
  92         }
  93
  94         return ret;
  95 }
  96
  97 static int xfrm6_output_one(struct sk_buff *skb)
  98 {
  99         struct dst_entry *dst = skb->dst;
 100         struct xfrm_state *x = dst->xfrm;
 101         int err;
 102
 103         if (skb->ip_summed == CHECKSUM_HW) {
 104                 err = skb_checksum_help(skb, 0);
 105                 if (err)
 106                         goto error_nolock;
 107         }
 108
 109         if (x->props.mode) {
 110                 err = xfrm6_tunnel_check_size(skb);
 111                 if (err)
 112                         goto error_nolock;
 113         }
 114
 115         do {
 116                 spin_lock_bh(&x->lock);
 117                 err = xfrm_state_check(x, skb);
 118                 if (err)
 119                         goto error;
 120
 121                 xfrm6_encap(skb);
 122
 123                 err = x->type->output(x, skb);
 124                 if (err)
 125                         goto error;
 126
 127                 x->curlft.bytes += skb->len;
 128                 x->curlft.packets++;
 129
 130                 spin_unlock_bh(&x->lock);
 131
 132                 skb->nh.raw = skb->data;
 133
 134                 if (!(skb->dst = dst_pop(dst))) {
 135                         err = -EHOSTUNREACH;
 136                         goto error_nolock;
 137                 }
 138                 dst = skb->dst;
 139                 x = dst->xfrm;
 140         } while (x && !x->props.mode);
 141
 142         IP6CB(skb)->flags |= IP6SKB_XFRM_TRANSFORMED;
 143         err = 0;
 144
 145 out_exit:
 146         return err;
 147 error:
 148         spin_unlock_bh(&x->lock);
 149 error_nolock:
 150         kfree_skb(skb);
 151         goto out_exit;
 152 }
 153
 154 static int xfrm6_output_finish(struct sk_buff *skb)
 155 {
 156         int err;
 157
 158         while (likely((err = xfrm6_output_one(skb)) == 0)) {
 159                 nf_reset(skb);
 160
 161                 err = nf_hook(PF_INET6, NF_IP6_LOCAL_OUT, &skb, NULL,
 162                               skb->dst->dev, dst_output);
 163                 if (unlikely(err != 1))
 164                         break;
 165
 166                 if (!skb->dst->xfrm)
 167                         return dst_output(skb);
 168
 169                 err = nf_hook(PF_INET6, NF_IP6_POST_ROUTING, &skb, NULL,
 170                               skb->dst->dev, xfrm6_output_finish);
 171                 if (unlikely(err != 1))
 172                         break;
 173         }
 174
 175         return err;
 176 }
 177
 178 int xfrm6_output(struct sk_buff *skb)
 179 {
 180         return NF_HOOK(PF_INET6, NF_IP6_POST_ROUTING, skb, NULL, skb->dst->dev,
 181                        xfrm6_output_finish);
 182 }