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)->daddroff = offsetof(struct iphdr, daddr);
  43         return xfrm_input(skb, nexthdr, spi, encap_type);
  44 }
  45 EXPORT_SYMBOL(xfrm4_rcv_encap);
  46
  47 int xfrm4_transport_finish(struct sk_buff *skb, int async)
  48 {
  49         struct iphdr *iph = ip_hdr(skb);
  50
  51         iph->protocol = XFRM_MODE_SKB_CB(skb)->protocol;
  52
  53 #ifdef CONFIG_NETFILTER
  54         __skb_push(skb, skb->data - skb_network_header(skb));
  55         iph->tot_len = htons(skb->len);
  56         ip_send_check(iph);
  57
  58         NF_HOOK(PF_INET, NF_IP_PRE_ROUTING, skb, skb->dev, NULL,
  59                 xfrm4_rcv_encap_finish);
  60         return 0;
  61 #else
  62         return -iph->protocol;
  63 #endif
  64 }
  65
  66 /* If it's a keepalive packet, then just eat it.
  67  * If it's an encapsulated packet, then pass it to the
  68  * IPsec xfrm input.
  69  * Returns 0 if skb passed to xfrm or was dropped.
  70  * Returns >0 if skb should be passed to UDP.
  71  * Returns <0 if skb should be resubmitted (-ret is protocol)
  72  */
  73 int xfrm4_udp_encap_rcv(struct sock *sk, struct sk_buff *skb)
  74 {
  75         struct udp_sock *up = udp_sk(sk);
  76         struct udphdr *uh;
  77         struct iphdr *iph;
  78         int iphlen, len;
  79         int ret;
  80
  81         __u8 *udpdata;
  82         __be32 *udpdata32;
  83         __u16 encap_type = up->encap_type;
  84
  85         /* if this is not encapsulated socket, then just return now */
  86         if (!encap_type)
  87                 return 1;
  88
  89         /* If this is a paged skb, make sure we pull up
  90          * whatever data we need to look at. */
  91         len = skb->len - sizeof(struct udphdr);
  92         if (!pskb_may_pull(skb, sizeof(struct udphdr) + min(len, 8)))
  93                 return 1;
  94
  95         /* Now we can get the pointers */
  96         uh = udp_hdr(skb);
  97         udpdata = (__u8 *)uh + sizeof(struct udphdr);
  98         udpdata32 = (__be32 *)udpdata;
  99
 100         switch (encap_type) {
 101         default:
 102         case UDP_ENCAP_ESPINUDP:
 103                 /* Check if this is a keepalive packet.  If so, eat it. */
 104                 if (len == 1 && udpdata[0] == 0xff) {
 105                         goto drop;
 106                 } else if (len > sizeof(struct ip_esp_hdr) && udpdata32[0] != 0) {
 107                         /* ESP Packet without Non-ESP header */
 108                         len = sizeof(struct udphdr);
 109                 } else
 110                         /* Must be an IKE packet.. pass it through */
 111                         return 1;
 112                 break;
 113         case UDP_ENCAP_ESPINUDP_NON_IKE:
 114                 /* Check if this is a keepalive packet.  If so, eat it. */
 115                 if (len == 1 && udpdata[0] == 0xff) {
 116                         goto drop;
 117                 } else if (len > 2 * sizeof(u32) + sizeof(struct ip_esp_hdr) &&
 118                            udpdata32[0] == 0 && udpdata32[1] == 0) {
 119
 120                         /* ESP Packet with Non-IKE marker */
 121                         len = sizeof(struct udphdr) + 2 * sizeof(u32);
 122                 } else
 123                         /* Must be an IKE packet.. pass it through */
 124                         return 1;
 125                 break;
 126         }
 127
 128         /* At this point we are sure that this is an ESPinUDP packet,
 129          * so we need to remove 'len' bytes from the packet (the UDP
 130          * header and optional ESP marker bytes) and then modify the
 131          * protocol to ESP, and then call into the transform receiver.
 132          */
 133         if (skb_cloned(skb) && pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
 134                 goto drop;
 135
 136         /* Now we can update and verify the packet length... */
 137         iph = ip_hdr(skb);
 138         iphlen = iph->ihl << 2;
 139         iph->tot_len = htons(ntohs(iph->tot_len) - len);
 140         if (skb->len < iphlen + len) {
 141                 /* packet is too small!?! */
 142                 goto drop;
 143         }
 144
 145         /* pull the data buffer up to the ESP header and set the
 146          * transport header to point to ESP.  Keep UDP on the stack
 147          * for later.
 148          */
 149         __skb_pull(skb, len);
 150         skb_reset_transport_header(skb);
 151
 152         /* process ESP */
 153         ret = xfrm4_rcv_encap(skb, IPPROTO_ESP, 0, encap_type);
 154         return ret;
 155
 156 drop:
 157         kfree_skb(skb);
 158         return 0;
 159 }
 160
 161 int xfrm4_rcv(struct sk_buff *skb)
 162 {
 163         return xfrm4_rcv_spi(skb, ip_hdr(skb)->protocol, 0);
 164 }
 165
 166 EXPORT_SYMBOL(xfrm4_rcv);