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 #ifdef CONFIG_NETFILTER
  25 static inline int xfrm4_rcv_encap_finish(struct sk_buff *skb)
  26 {
  27         if (skb->dst == NULL) {
  28                 const struct iphdr *iph = ip_hdr(skb);
  29
  30                 if (ip_route_input(skb, iph->daddr, iph->saddr, iph->tos,
  31                                    skb->dev))
  32                         goto drop;
  33         }
  34         return dst_input(skb);
  35 drop:
  36         kfree_skb(skb);
  37         return NET_RX_DROP;
  38 }
  39 #endif
  40
  41 int xfrm4_rcv_encap(struct sk_buff *skb, int nexthdr, __be32 spi,
  42                     int encap_type)
  43 {
  44         XFRM_SPI_SKB_CB(skb)->nhoff = offsetof(struct iphdr, protocol);
  45         XFRM_SPI_SKB_CB(skb)->daddroff = offsetof(struct iphdr, daddr);
  46         return xfrm_input(skb, nexthdr, spi, encap_type);
  47 }
  48 EXPORT_SYMBOL(xfrm4_rcv_encap);
  49
  50 int xfrm4_transport_finish(struct sk_buff *skb, int async)
  51 {
  52 #ifdef CONFIG_NETFILTER
  53         __skb_push(skb, skb->data - skb_network_header(skb));
  54         ip_hdr(skb)->tot_len = htons(skb->len);
  55         ip_send_check(ip_hdr(skb));
  56
  57         NF_HOOK(PF_INET, NF_IP_PRE_ROUTING, skb, skb->dev, NULL,
  58                 xfrm4_rcv_encap_finish);
  59         return 0;
  60 #else
  61         return -ip_hdr(skb)->protocol;
  62 #endif
  63 }
  64
  65 /* If it's a keepalive packet, then just eat it.
  66  * If it's an encapsulated packet, then pass it to the
  67  * IPsec xfrm input.
  68  * Returns 0 if skb passed to xfrm or was dropped.
  69  * Returns >0 if skb should be passed to UDP.
  70  * Returns <0 if skb should be resubmitted (-ret is protocol)
  71  */
  72 int xfrm4_udp_encap_rcv(struct sock *sk, struct sk_buff *skb)
  73 {
  74         struct udp_sock *up = udp_sk(sk);
  75         struct udphdr *uh;
  76         struct iphdr *iph;
  77         int iphlen, len;
  78         int ret;
  79
  80         __u8 *udpdata;
  81         __be32 *udpdata32;
  82         __u16 encap_type = up->encap_type;
  83
  84         /* if this is not encapsulated socket, then just return now */
  85         if (!encap_type)
  86                 return 1;
  87
  88         /* If this is a paged skb, make sure we pull up
  89          * whatever data we need to look at. */
  90         len = skb->len - sizeof(struct udphdr);
  91         if (!pskb_may_pull(skb, sizeof(struct udphdr) + min(len, 8)))
  92                 return 1;
  93
  94         /* Now we can get the pointers */
  95         uh = udp_hdr(skb);
  96         udpdata = (__u8 *)uh + sizeof(struct udphdr);
  97         udpdata32 = (__be32 *)udpdata;
  98
  99         switch (encap_type) {
 100         default:
 101         case UDP_ENCAP_ESPINUDP:
 102                 /* Check if this is a keepalive packet.  If so, eat it. */
 103                 if (len == 1 && udpdata[0] == 0xff) {
 104                         goto drop;
 105                 } else if (len > sizeof(struct ip_esp_hdr) && udpdata32[0] != 0) {
 106                         /* ESP Packet without Non-ESP header */
 107                         len = sizeof(struct udphdr);
 108                 } else
 109                         /* Must be an IKE packet.. pass it through */
 110                         return 1;
 111                 break;
 112         case UDP_ENCAP_ESPINUDP_NON_IKE:
 113                 /* Check if this is a keepalive packet.  If so, eat it. */
 114                 if (len == 1 && udpdata[0] == 0xff) {
 115                         goto drop;
 116                 } else if (len > 2 * sizeof(u32) + sizeof(struct ip_esp_hdr) &&
 117                            udpdata32[0] == 0 && udpdata32[1] == 0) {
 118
 119                         /* ESP Packet with Non-IKE marker */
 120                         len = sizeof(struct udphdr) + 2 * sizeof(u32);
 121                 } else
 122                         /* Must be an IKE packet.. pass it through */
 123                         return 1;
 124                 break;
 125         }
 126
 127         /* At this point we are sure that this is an ESPinUDP packet,
 128          * so we need to remove 'len' bytes from the packet (the UDP
 129          * header and optional ESP marker bytes) and then modify the
 130          * protocol to ESP, and then call into the transform receiver.
 131          */
 132         if (skb_cloned(skb) && pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
 133                 goto drop;
 134
 135         /* Now we can update and verify the packet length... */
 136         iph = ip_hdr(skb);
 137         iphlen = iph->ihl << 2;
 138         iph->tot_len = htons(ntohs(iph->tot_len) - len);
 139         if (skb->len < iphlen + len) {
 140                 /* packet is too small!?! */
 141                 goto drop;
 142         }
 143
 144         /* pull the data buffer up to the ESP header and set the
 145          * transport header to point to ESP.  Keep UDP on the stack
 146          * for later.
 147          */
 148         __skb_pull(skb, len);
 149         skb_reset_transport_header(skb);
 150
 151         /* process ESP */
 152         ret = xfrm4_rcv_encap(skb, IPPROTO_ESP, 0, encap_type);
 153         return ret;
 154
 155 drop:
 156         kfree_skb(skb);
 157         return 0;
 158 }
 159
 160 int xfrm4_rcv(struct sk_buff *skb)
 161 {
 162         return xfrm4_rcv_spi(skb, ip_hdr(skb)->protocol, 0);
 163 }
 164
 165 EXPORT_SYMBOL(xfrm4_rcv);