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/skbuff.h>
  13 #include <linux/spinlock.h>
  14 #include <linux/icmpv6.h>
  15 #include <net/dsfield.h>
  16 #include <net/inet_ecn.h>
  17 #include <net/ipv6.h>
  18 #include <net/xfrm.h>
  19
  20 /* Add encapsulation header.
  21  *
  22  * In transport mode, the IP header and mutable extension headers will be moved
  23  * forward to make space for the encapsulation header.
  24  *
  25  * In tunnel mode, the top IP header will be constructed per RFC 2401.
  26  * The following fields in it shall be filled in by x->type->output:
  27  *      payload_len
  28  *
  29  * On exit, skb->h will be set to the start of the encapsulation header to be
  30  * filled in by x->type->output and skb->nh will be set to the nextheader field
  31  * of the extension header directly preceding the encapsulation header, or in
  32  * its absence, that of the top IP header.  The value of skb->data will always
  33  * point to the top IP header.
  34  */
  35 static void xfrm6_encap(struct sk_buff *skb)
  36 {
  37         struct dst_entry *dst = skb->dst;
  38         struct xfrm_state *x = dst->xfrm;
  39         struct ipv6hdr *iph, *top_iph;
  40         int dsfield;
  41
  42         skb_push(skb, x->props.header_len);
  43         iph = skb->nh.ipv6h;
  44
  45         if (!x->props.mode) {
  46                 u8 *prevhdr;
  47                 int hdr_len;
  48
  49                 hdr_len = ip6_find_1stfragopt(skb, &prevhdr);
  50                 skb->nh.raw = prevhdr - x->props.header_len;
  51                 skb->h.raw = skb->data + hdr_len;
  52                 memmove(skb->data, iph, hdr_len);
  53                 return;
  54         }
  55
  56         skb->nh.raw = skb->data;
  57         top_iph = skb->nh.ipv6h;
  58         skb->nh.raw = &top_iph->nexthdr;
  59         skb->h.ipv6h = top_iph + 1;
  60
  61         top_iph->version = 6;
  62         top_iph->priority = iph->priority;
  63         top_iph->flow_lbl[0] = iph->flow_lbl[0];
  64         top_iph->flow_lbl[1] = iph->flow_lbl[1];
  65         top_iph->flow_lbl[2] = iph->flow_lbl[2];
  66         dsfield = ipv6_get_dsfield(top_iph);
  67         dsfield = INET_ECN_encapsulate(dsfield, dsfield);
  68         if (x->props.flags & XFRM_STATE_NOECN)
  69                 dsfield &= ~INET_ECN_MASK;
  70         ipv6_change_dsfield(top_iph, 0, dsfield);
  71         top_iph->nexthdr = IPPROTO_IPV6;
  72         top_iph->hop_limit = dst_metric(dst->child, RTAX_HOPLIMIT);
  73         ipv6_addr_copy(&top_iph->saddr, (struct in6_addr *)&x->props.saddr);
  74         ipv6_addr_copy(&top_iph->daddr, (struct in6_addr *)&x->id.daddr);
  75 }
  76
  77 static int xfrm6_tunnel_check_size(struct sk_buff *skb)
  78 {
  79         int mtu, ret = 0;
  80         struct dst_entry *dst = skb->dst;
  81
  82         mtu = dst_mtu(dst);
  83         if (mtu < IPV6_MIN_MTU)
  84                 mtu = IPV6_MIN_MTU;
  85
  86         if (skb->len > mtu) {
  87                 icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu, skb->dev);
  88                 ret = -EMSGSIZE;
  89         }
  90
  91         return ret;
  92 }
  93
  94 int xfrm6_output(struct sk_buff *skb)
  95 {
  96         struct dst_entry *dst = skb->dst;
  97         struct xfrm_state *x = dst->xfrm;
  98         int err;
  99
 100         if (skb->ip_summed == CHECKSUM_HW) {
 101                 err = skb_checksum_help(skb, 0);
 102                 if (err)
 103                         goto error_nolock;
 104         }
 105
 106         if (x->props.mode) {
 107                 err = xfrm6_tunnel_check_size(skb);
 108                 if (err)
 109                         goto error_nolock;
 110         }
 111
 112         spin_lock_bh(&x->lock);
 113         err = xfrm_state_check(x, skb);
 114         if (err)
 115                 goto error;
 116
 117         xfrm6_encap(skb);
 118
 119         err = x->type->output(x, skb);
 120         if (err)
 121                 goto error;
 122
 123         x->curlft.bytes += skb->len;
 124         x->curlft.packets++;
 125
 126         spin_unlock_bh(&x->lock);
 127
 128         skb->nh.raw = skb->data;
 129
 130         if (!(skb->dst = dst_pop(dst))) {
 131                 err = -EHOSTUNREACH;
 132                 goto error_nolock;
 133         }
 134         err = NET_XMIT_BYPASS;
 135
 136 out_exit:
 137         return err;
 138 error:
 139         spin_unlock_bh(&x->lock);
 140 error_nolock:
 141         kfree_skb(skb);
 142         goto out_exit;
 143 }