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 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);
  35 drop:
  36         kfree_skb(skb);
  37         return NET_RX_DROP;
  38 }
  39
  40 int 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 }
  47 EXPORT_SYMBOL(xfrm4_rcv_encap);
  48
  49 int 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  */
  76 int 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_unclone(skb, 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
 157 drop:
 158         kfree_skb(skb);
 159         return 0;
 160 }
 161
 162 int xfrm4_rcv(struct sk_buff *skb)
 163 {
 164         return xfrm4_rcv_spi(skb, ip_hdr(skb)->protocol, 0);
 165 }
 166 EXPORT_SYMBOL(xfrm4_rcv);