root/net/ipv4/xfrm4_input.c

DEFINITIONS

1. xfrm4_extract_input
2. xfrm4_rcv_encap_finish
3. xfrm4_rcv_encap
4. xfrm4_transport_finish
5. xfrm4_udp_encap_rcv
6. xfrm4_rcv

/*
 * xfrm4_input.c
 *
 * Changes:
 *      YOSHIFUJI Hideaki @USAGI
 *              Split up af-specific portion
 *      Derek Atkins <derek@ihtfp.com>
 *              Add Encapsulation support
 *
 */

#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 == NULL) {
                const struct iphdr *iph = ip_hdr(skb);

                if (ip_route_input(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(PF_INET, 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;
        int ret;

        __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 */
        ret = xfrm4_rcv_encap(skb, IPPROTO_ESP, 0, encap_type);
        return ret;

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);