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