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/module.h>
  13 #include <linux/string.h>
  14 #include <linux/netfilter.h>
  15 #include <linux/netfilter_ipv4.h>
  16 #include <net/ip.h>
  17 #include <net/xfrm.h>
  18
  19 int xfrm4_extract_input(struct xfrm_state *x, struct sk_buff *skb)
  20 {
  21         return xfrm4_extract_header(skb);
  22 }
  23
  24 static inline int xfrm4_rcv_encap_finish(struct sk_buff *skb)
  25 {
  26         if (skb->dst == NULL) {
  27                 const struct iphdr *iph = ip_hdr(skb);
  28
  29                 if (ip_route_input(skb, iph->daddr, iph->saddr, iph->tos,
  30                                    skb->dev))
  31                         goto drop;
  32         }
  33         return dst_input(skb);
  34 drop:
  35         kfree_skb(skb);
  36         return NET_RX_DROP;
  37 }
  38
  39 int xfrm4_rcv_encap(struct sk_buff *skb, int nexthdr, __be32 spi,
  40                     int encap_type)
  41 {
  42         XFRM_SPI_SKB_CB(skb)->family = AF_INET;
  43         XFRM_SPI_SKB_CB(skb)->daddroff = offsetof(struct iphdr, daddr);
  44         return xfrm_input(skb, nexthdr, spi, encap_type);
  45 }
  46 EXPORT_SYMBOL(xfrm4_rcv_encap);
  47
  48 int xfrm4_transport_finish(struct sk_buff *skb, int async)
  49 {
  50         struct iphdr *iph = ip_hdr(skb);
  51
  52         iph->protocol = XFRM_MODE_SKB_CB(skb)->protocol;
  53
  54 #ifndef CONFIG_NETFILTER
  55         if (!async)
  56                 return -iph->protocol;
  57 #endif
  58
  59         __skb_push(skb, skb->data - skb_network_header(skb));
  60         iph->tot_len = htons(skb->len);
  61         ip_send_check(iph);
  62
  63         NF_HOOK(PF_INET, NF_INET_PRE_ROUTING, skb, skb->dev, NULL,
  64                 xfrm4_rcv_encap_finish);
  65         return 0;
  66 }
  67
  68 /* If it's a keepalive packet, then just eat it.
  69  * If it's an encapsulated packet, then pass it to the
  70  * IPsec xfrm input.
  71  * Returns 0 if skb passed to xfrm or was dropped.
  72  * Returns >0 if skb should be passed to UDP.
  73  * Returns <0 if skb should be resubmitted (-ret is protocol)
  74  */
  75 int xfrm4_udp_encap_rcv(struct sock *sk, struct sk_buff *skb)
  76 {
  77         struct udp_sock *up = udp_sk(sk);
  78         struct udphdr *uh;
  79         struct iphdr *iph;
  80         int iphlen, len;
  81         int ret;
  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         ret = xfrm4_rcv_encap(skb, IPPROTO_ESP, 0, encap_type);
 156         return ret;
 157
 158 drop:
 159         kfree_skb(skb);
 160         return 0;
 161 }
 162
 163 int xfrm4_rcv(struct sk_buff *skb)
 164 {
 165         return xfrm4_rcv_spi(skb, ip_hdr(skb)->protocol, 0);
 166 }
 167
 168 EXPORT_SYMBOL(xfrm4_rcv);