linux/net/ipv4/xfrm4_output.c
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   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
  21static 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(skb);
  33        mtu = dst_mtu(dst);
  34        if (skb->len > mtu) {
  35                if (skb->sk)
  36                        ip_local_error(skb->sk, EMSGSIZE, ip_hdr(skb)->daddr,
  37                                       inet_sk(skb->sk)->inet_dport, mtu);
  38                else
  39                        icmp_send(skb, ICMP_DEST_UNREACH,
  40                                  ICMP_FRAG_NEEDED, htonl(mtu));
  41                ret = -EMSGSIZE;
  42        }
  43out:
  44        return ret;
  45}
  46
  47int xfrm4_extract_output(struct xfrm_state *x, struct sk_buff *skb)
  48{
  49        int err;
  50
  51        err = xfrm4_tunnel_check_size(skb);
  52        if (err)
  53                return err;
  54
  55        XFRM_MODE_SKB_CB(skb)->protocol = ip_hdr(skb)->protocol;
  56
  57        return xfrm4_extract_header(skb);
  58}
  59
  60int xfrm4_prepare_output(struct xfrm_state *x, struct sk_buff *skb)
  61{
  62        int err;
  63
  64        err = xfrm_inner_extract_output(x, skb);
  65        if (err)
  66                return err;
  67
  68        memset(IPCB(skb), 0, sizeof(*IPCB(skb)));
  69        IPCB(skb)->flags |= IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED;
  70
  71        skb->protocol = htons(ETH_P_IP);
  72
  73        return x->outer_mode->output2(x, skb);
  74}
  75EXPORT_SYMBOL(xfrm4_prepare_output);
  76
  77int xfrm4_output_finish(struct sk_buff *skb)
  78{
  79#ifdef CONFIG_NETFILTER
  80        if (!skb_dst(skb)->xfrm) {
  81                IPCB(skb)->flags |= IPSKB_REROUTED;
  82                return dst_output(skb);
  83        }
  84
  85        IPCB(skb)->flags |= IPSKB_XFRM_TRANSFORMED;
  86#endif
  87
  88        skb->protocol = htons(ETH_P_IP);
  89        return xfrm_output(skb);
  90}
  91
  92int xfrm4_output(struct sk_buff *skb)
  93{
  94        struct dst_entry *dst = skb_dst(skb);
  95        struct xfrm_state *x = dst->xfrm;
  96
  97        return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING, skb,
  98                            NULL, dst->dev,
  99                            x->outer_mode->afinfo->output_finish,
 100                            !(IPCB(skb)->flags & IPSKB_REROUTED));
 101}
 102
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