net/ipv4/xfrm4_input.c

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