linux/net/ipv4/xfrm4_input.c
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   1/*
   2 * xfrm4_input.c
   3 *
   4 * Changes:
   5 *      YOSHIFUJI Hideaki @USAGI
   6 *              Split up af-specific portion
   7 *      Derek Atkins <derek@ihtfp.com>
   8 *              Add Encapsulation support
   9 *
  10 */
  11
  12#include <linux/slab.h>
  13#include <linux/module.h>
  14#include <linux/string.h>
  15#include <linux/netfilter.h>
  16#include <linux/netfilter_ipv4.h>
  17#include <net/ip.h>
  18#include <net/xfrm.h>
  19
  20int xfrm4_extract_input(struct xfrm_state *x, struct sk_buff *skb)
  21{
  22        return xfrm4_extract_header(skb);
  23}
  24
  25static inline int xfrm4_rcv_encap_finish(struct sk_buff *skb)
  26{
  27        if (skb_dst(skb) == NULL) {
  28                const struct iphdr *iph = ip_hdr(skb);
  29
  30                if (ip_route_input_noref(skb, iph->daddr, iph->saddr,
  31                                         iph->tos, skb->dev))
  32                        goto drop;
  33        }
  34        return dst_input(skb);
  35drop:
  36        kfree_skb(skb);
  37        return NET_RX_DROP;
  38}
  39
  40int xfrm4_rcv_encap(struct sk_buff *skb, int nexthdr, __be32 spi,
  41                    int encap_type)
  42{
  43        XFRM_SPI_SKB_CB(skb)->family = AF_INET;
  44        XFRM_SPI_SKB_CB(skb)->daddroff = offsetof(struct iphdr, daddr);
  45        return xfrm_input(skb, nexthdr, spi, encap_type);
  46}
  47EXPORT_SYMBOL(xfrm4_rcv_encap);
  48
  49int xfrm4_transport_finish(struct sk_buff *skb, int async)
  50{
  51        struct iphdr *iph = ip_hdr(skb);
  52
  53        iph->protocol = XFRM_MODE_SKB_CB(skb)->protocol;
  54
  55#ifndef CONFIG_NETFILTER
  56        if (!async)
  57                return -iph->protocol;
  58#endif
  59
  60        __skb_push(skb, skb->data - skb_network_header(skb));
  61        iph->tot_len = htons(skb->len);
  62        ip_send_check(iph);
  63
  64        NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, skb, skb->dev, NULL,
  65                xfrm4_rcv_encap_finish);
  66        return 0;
  67}
  68
  69/* If it's a keepalive packet, then just eat it.
  70 * If it's an encapsulated packet, then pass it to the
  71 * IPsec xfrm input.
  72 * Returns 0 if skb passed to xfrm or was dropped.
  73 * Returns >0 if skb should be passed to UDP.
  74 * Returns <0 if skb should be resubmitted (-ret is protocol)
  75 */
  76int xfrm4_udp_encap_rcv(struct sock *sk, struct sk_buff *skb)
  77{
  78        struct udp_sock *up = udp_sk(sk);
  79        struct udphdr *uh;
  80        struct iphdr *iph;
  81        int iphlen, len;
  82
  83        __u8 *udpdata;
  84        __be32 *udpdata32;
  85        __u16 encap_type = up->encap_type;
  86
  87        /* if this is not encapsulated socket, then just return now */
  88        if (!encap_type)
  89                return 1;
  90
  91        /* If this is a paged skb, make sure we pull up
  92         * whatever data we need to look at. */
  93        len = skb->len - sizeof(struct udphdr);
  94        if (!pskb_may_pull(skb, sizeof(struct udphdr) + min(len, 8)))
  95                return 1;
  96
  97        /* Now we can get the pointers */
  98        uh = udp_hdr(skb);
  99        udpdata = (__u8 *)uh + sizeof(struct udphdr);
 100        udpdata32 = (__be32 *)udpdata;
 101
 102        switch (encap_type) {
 103        default:
 104        case UDP_ENCAP_ESPINUDP:
 105                /* Check if this is a keepalive packet.  If so, eat it. */
 106                if (len == 1 && udpdata[0] == 0xff) {
 107                        goto drop;
 108                } else if (len > sizeof(struct ip_esp_hdr) && udpdata32[0] != 0) {
 109                        /* ESP Packet without Non-ESP header */
 110                        len = sizeof(struct udphdr);
 111                } else
 112                        /* Must be an IKE packet.. pass it through */
 113                        return 1;
 114                break;
 115        case UDP_ENCAP_ESPINUDP_NON_IKE:
 116                /* Check if this is a keepalive packet.  If so, eat it. */
 117                if (len == 1 && udpdata[0] == 0xff) {
 118                        goto drop;
 119                } else if (len > 2 * sizeof(u32) + sizeof(struct ip_esp_hdr) &&
 120                           udpdata32[0] == 0 && udpdata32[1] == 0) {
 121
 122                        /* ESP Packet with Non-IKE marker */
 123                        len = sizeof(struct udphdr) + 2 * sizeof(u32);
 124                } else
 125                        /* Must be an IKE packet.. pass it through */
 126                        return 1;
 127                break;
 128        }
 129
 130        /* At this point we are sure that this is an ESPinUDP packet,
 131         * so we need to remove 'len' bytes from the packet (the UDP
 132         * header and optional ESP marker bytes) and then modify the
 133         * protocol to ESP, and then call into the transform receiver.
 134         */
 135        if (skb_cloned(skb) && pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
 136                goto drop;
 137
 138        /* Now we can update and verify the packet length... */
 139        iph = ip_hdr(skb);
 140        iphlen = iph->ihl << 2;
 141        iph->tot_len = htons(ntohs(iph->tot_len) - len);
 142        if (skb->len < iphlen + len) {
 143                /* packet is too small!?! */
 144                goto drop;
 145        }
 146
 147        /* pull the data buffer up to the ESP header and set the
 148         * transport header to point to ESP.  Keep UDP on the stack
 149         * for later.
 150         */
 151        __skb_pull(skb, len);
 152        skb_reset_transport_header(skb);
 153
 154        /* process ESP */
 155        return xfrm4_rcv_encap(skb, IPPROTO_ESP, 0, encap_type);
 156
 157drop:
 158        kfree_skb(skb);
 159        return 0;
 160}
 161
 162int xfrm4_rcv(struct sk_buff *skb)
 163{
 164        return xfrm4_rcv_spi(skb, ip_hdr(skb)->protocol, 0);
 165}
 166EXPORT_SYMBOL(xfrm4_rcv);
 167
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