LXR linux/net/ipv4/xfrm4

   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
  20int xfrm4_extract_input(struct xfrm_state *x, struct sk_buff *skb)
  21{
  22        return xfrm4_extract_header(skb);
  23}
  24
  25static inline int xfrm4_rcv_encap_finish(struct sock *sk, struct sk_buff *skb)
  26{
  27        if (!skb_dst(skb)) {
  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);
  35drop:
  36        kfree_skb(skb);
  37        return NET_RX_DROP;
  38}
  39
  40int xfrm4_transport_finish(struct sk_buff *skb, int async)
  41{
  42        struct iphdr *iph = ip_hdr(skb);
  43
  44        iph->protocol = XFRM_MODE_SKB_CB(skb)->protocol;
  45
  46#ifndef CONFIG_NETFILTER
  47        if (!async)
  48                return -iph->protocol;
  49#endif
  50
  51        __skb_push(skb, skb->data - skb_network_header(skb));
  52        iph->tot_len = htons(skb->len);
  53        ip_send_check(iph);
  54
  55        NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, NULL, skb,
  56                skb->dev, NULL,
  57                xfrm4_rcv_encap_finish);
  58        return 0;
  59}
  60
  61/* If it's a keepalive packet, then just eat it.
  62 * If it's an encapsulated packet, then pass it to the
  63 * IPsec xfrm input.
  64 * Returns 0 if skb passed to xfrm or was dropped.
  65 * Returns >0 if skb should be passed to UDP.
  66 * Returns <0 if skb should be resubmitted (-ret is protocol)
  67 */
  68int xfrm4_udp_encap_rcv(struct sock *sk, struct sk_buff *skb)
  69{
  70        struct udp_sock *up = udp_sk(sk);
  71        struct udphdr *uh;
  72        struct iphdr *iph;
  73        int iphlen, len;
  74
  75        __u8 *udpdata;
  76        __be32 *udpdata32;
  77        __u16 encap_type = up->encap_type;
  78
  79        /* if this is not encapsulated socket, then just return now */
  80        if (!encap_type)
  81                return 1;
  82
  83        /* If this is a paged skb, make sure we pull up
  84         * whatever data we need to look at. */
  85        len = skb->len - sizeof(struct udphdr);
  86        if (!pskb_may_pull(skb, sizeof(struct udphdr) + min(len, 8)))
  87                return 1;
  88
  89        /* Now we can get the pointers */
  90        uh = udp_hdr(skb);
  91        udpdata = (__u8 *)uh + sizeof(struct udphdr);
  92        udpdata32 = (__be32 *)udpdata;
  93
  94        switch (encap_type) {
  95        default:
  96        case UDP_ENCAP_ESPINUDP:
  97                /* Check if this is a keepalive packet.  If so, eat it. */
  98                if (len == 1 && udpdata[0] == 0xff) {
  99                        goto drop;
 100                } else if (len > sizeof(struct ip_esp_hdr) && udpdata32[0] != 0) {
 101                        /* ESP Packet without Non-ESP header */
 102                        len = sizeof(struct udphdr);
 103                } else
 104                        /* Must be an IKE packet.. pass it through */
 105                        return 1;
 106                break;
 107        case UDP_ENCAP_ESPINUDP_NON_IKE:
 108                /* Check if this is a keepalive packet.  If so, eat it. */
 109                if (len == 1 && udpdata[0] == 0xff) {
 110                        goto drop;
 111                } else if (len > 2 * sizeof(u32) + sizeof(struct ip_esp_hdr) &&
 112                           udpdata32[0] == 0 && udpdata32[1] == 0) {
 113
 114                        /* ESP Packet with Non-IKE marker */
 115                        len = sizeof(struct udphdr) + 2 * sizeof(u32);
 116                } else
 117                        /* Must be an IKE packet.. pass it through */
 118                        return 1;
 119                break;
 120        }
 121
 122        /* At this point we are sure that this is an ESPinUDP packet,
 123         * so we need to remove 'len' bytes from the packet (the UDP
 124         * header and optional ESP marker bytes) and then modify the
 125         * protocol to ESP, and then call into the transform receiver.
 126         */
 127        if (skb_unclone(skb, GFP_ATOMIC))
 128                goto drop;
 129
 130        /* Now we can update and verify the packet length... */
 131        iph = ip_hdr(skb);
 132        iphlen = iph->ihl << 2;
 133        iph->tot_len = htons(ntohs(iph->tot_len) - len);
 134        if (skb->len < iphlen + len) {
 135                /* packet is too small!?! */
 136                goto drop;
 137        }
 138
 139        /* pull the data buffer up to the ESP header and set the
 140         * transport header to point to ESP.  Keep UDP on the stack
 141         * for later.
 142         */
 143        __skb_pull(skb, len);
 144        skb_reset_transport_header(skb);
 145
 146        /* process ESP */
 147        return xfrm4_rcv_encap(skb, IPPROTO_ESP, 0, encap_type);
 148
 149drop:
 150        kfree_skb(skb);
 151        return 0;
 152}
 153
 154int xfrm4_rcv(struct sk_buff *skb)
 155{
 156        return xfrm4_rcv_spi(skb, ip_hdr(skb)->protocol, 0);
 157}
 158EXPORT_SYMBOL(xfrm4_rcv);
 159