xfrm4_input.c

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/*
 * xfrm4_input.c
 *
 * Changes:
 *  YOSHIFUJI Hideaki @USAGI
 *      Split up af-specific portion
 *  Derek Atkins <[email protected]>
 *      Add Encapsulation support
 *
 */

#include <linux/slab.h>
#include <linux/module.h>
#include <linux/string.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
#include <net/ip.h>
#include <net/xfrm.h>

int xfrm4_extract_input(struct xfrm_state *x, struct sk_buff *skb)
{
    return xfrm4_extract_header(skb);
}

static inline int xfrm4_rcv_encap_finish(struct sk_buff *skb)
{
    if (skb_dst(skb) == NULL) {
        const struct iphdr *iph = ip_hdr(skb);

        if (ip_route_input_noref(skb, iph->daddr, iph->saddr,
                     iph->tos, skb->dev))
            goto drop;
    }
    return dst_input(skb);
drop:
    kfree_skb(skb);
    return NET_RX_DROP;
}

int xfrm4_rcv_encap(struct sk_buff *skb, int nexthdr, __be32 spi,
            int encap_type)
{
    XFRM_SPI_SKB_CB(skb)->family = AF_INET;
    XFRM_SPI_SKB_CB(skb)->daddroff = offsetof(struct iphdr, daddr);
    return xfrm_input(skb, nexthdr, spi, encap_type);
}
EXPORT_SYMBOL(xfrm4_rcv_encap);

int xfrm4_transport_finish(struct sk_buff *skb, int async)
{
    struct iphdr *iph = ip_hdr(skb);

    iph->protocol = XFRM_MODE_SKB_CB(skb)->protocol;

#ifndef CONFIG_NETFILTER
    if (!async)
        return -iph->protocol;
#endif

    __skb_push(skb, skb->data - skb_network_header(skb));
    iph->tot_len = htons(skb->len);
    ip_send_check(iph);

    NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, skb, skb->dev, NULL,
        xfrm4_rcv_encap_finish);
    return 0;
}

/* If it's a keepalive packet, then just eat it.
 * If it's an encapsulated packet, then pass it to the
 * IPsec xfrm input.
 * Returns 0 if skb passed to xfrm or was dropped.
 * Returns >0 if skb should be passed to UDP.
 * Returns <0 if skb should be resubmitted (-ret is protocol)
 */
int xfrm4_udp_encap_rcv(struct sock *sk, struct sk_buff *skb)
{
    struct udp_sock *up = udp_sk(sk);
    struct udphdr *uh;
    struct iphdr *iph;
    int iphlen, len;

    __u8 *udpdata;
    __be32 *udpdata32;
    __u16 encap_type = up->encap_type;

    /* if this is not encapsulated socket, then just return now */
    if (!encap_type)
        return 1;

    /* If this is a paged skb, make sure we pull up
     * whatever data we need to look at. */
    len = skb->len - sizeof(struct udphdr);
    if (!pskb_may_pull(skb, sizeof(struct udphdr) + min(len, 8)))
        return 1;

    /* Now we can get the pointers */
    uh = udp_hdr(skb);
    udpdata = (__u8 *)uh + sizeof(struct udphdr);
    udpdata32 = (__be32 *)udpdata;

    switch (encap_type) {
    default:
    case UDP_ENCAP_ESPINUDP:
        /* Check if this is a keepalive packet.  If so, eat it. */
        if (len == 1 && udpdata[0] == 0xff) {
            goto drop;
        } else if (len > sizeof(struct ip_esp_hdr) && udpdata32[0] != 0) {
            /* ESP Packet without Non-ESP header */
            len = sizeof(struct udphdr);
        } else
            /* Must be an IKE packet.. pass it through */
            return 1;
        break;
    case UDP_ENCAP_ESPINUDP_NON_IKE:
        /* Check if this is a keepalive packet.  If so, eat it. */
        if (len == 1 && udpdata[0] == 0xff) {
            goto drop;
        } else if (len > 2 * sizeof(u32) + sizeof(struct ip_esp_hdr) &&
               udpdata32[0] == 0 && udpdata32[1] == 0) {

            /* ESP Packet with Non-IKE marker */
            len = sizeof(struct udphdr) + 2 * sizeof(u32);
        } else
            /* Must be an IKE packet.. pass it through */
            return 1;
        break;
    }

    /* At this point we are sure that this is an ESPinUDP packet,
     * so we need to remove 'len' bytes from the packet (the UDP
     * header and optional ESP marker bytes) and then modify the
     * protocol to ESP, and then call into the transform receiver.
     */
    if (skb_cloned(skb) && pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
        goto drop;

    /* Now we can update and verify the packet length... */
    iph = ip_hdr(skb);
    iphlen = iph->ihl << 2;
    iph->tot_len = htons(ntohs(iph->tot_len) - len);
    if (skb->len < iphlen + len) {
        /* packet is too small!?! */
        goto drop;
    }

    /* pull the data buffer up to the ESP header and set the
     * transport header to point to ESP.  Keep UDP on the stack
     * for later.
     */
    __skb_pull(skb, len);
    skb_reset_transport_header(skb);

    /* process ESP */
    return xfrm4_rcv_encap(skb, IPPROTO_ESP, 0, encap_type);

drop:
    kfree_skb(skb);
    return 0;
}

int xfrm4_rcv(struct sk_buff *skb)
{
    return xfrm4_rcv_spi(skb, ip_hdr(skb)->protocol, 0);
}
EXPORT_SYMBOL(xfrm4_rcv);