xfrm4_policy.c

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/*
 * xfrm4_policy.c
 *
 * Changes:
 *  Kazunori MIYAZAWA @USAGI
 *  YOSHIFUJI Hideaki @USAGI
 *      Split up af-specific portion
 *
 */

#include <linux/err.h>
#include <linux/kernel.h>
#include <linux/inetdevice.h>
#include <linux/if_tunnel.h>
#include <net/dst.h>
#include <net/xfrm.h>
#include <net/ip.h>

static struct xfrm_policy_afinfo xfrm4_policy_afinfo;

static struct dst_entry *__xfrm4_dst_lookup(struct net *net, struct flowi4 *fl4,
                        int tos,
                        const xfrm_address_t *saddr,
                        const xfrm_address_t *daddr)
{
    struct rtable *rt;

    memset(fl4, 0, sizeof(*fl4));
    fl4->daddr = daddr->a4;
    fl4->flowi4_tos = tos;
    if (saddr)
        fl4->saddr = saddr->a4;

    rt = __ip_route_output_key(net, fl4);
    if (!IS_ERR(rt))
        return &rt->dst;

    return ERR_CAST(rt);
}

static struct dst_entry *xfrm4_dst_lookup(struct net *net, int tos,
                      const xfrm_address_t *saddr,
                      const xfrm_address_t *daddr)
{
    struct flowi4 fl4;

    return __xfrm4_dst_lookup(net, &fl4, tos, saddr, daddr);
}

static int xfrm4_get_saddr(struct net *net,
               xfrm_address_t *saddr, xfrm_address_t *daddr)
{
    struct dst_entry *dst;
    struct flowi4 fl4;

    dst = __xfrm4_dst_lookup(net, &fl4, 0, NULL, daddr);
    if (IS_ERR(dst))
        return -EHOSTUNREACH;

    saddr->a4 = fl4.saddr;
    dst_release(dst);
    return 0;
}

static int xfrm4_get_tos(const struct flowi *fl)
{
    return IPTOS_RT_MASK & fl->u.ip4.flowi4_tos; /* Strip ECN bits */
}

static int xfrm4_init_path(struct xfrm_dst *path, struct dst_entry *dst,
               int nfheader_len)
{
    return 0;
}

static int xfrm4_fill_dst(struct xfrm_dst *xdst, struct net_device *dev,
              const struct flowi *fl)
{
    struct rtable *rt = (struct rtable *)xdst->route;
    const struct flowi4 *fl4 = &fl->u.ip4;

    xdst->u.rt.rt_iif = fl4->flowi4_iif;

    xdst->u.dst.dev = dev;
    dev_hold(dev);

    /* Sheit... I remember I did this right. Apparently,
     * it was magically lost, so this code needs audit */
    xdst->u.rt.rt_is_input = rt->rt_is_input;
    xdst->u.rt.rt_flags = rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST |
                          RTCF_LOCAL);
    xdst->u.rt.rt_type = rt->rt_type;
    xdst->u.rt.rt_gateway = rt->rt_gateway;
    xdst->u.rt.rt_uses_gateway = rt->rt_uses_gateway;
    xdst->u.rt.rt_pmtu = rt->rt_pmtu;
    INIT_LIST_HEAD(&xdst->u.rt.rt_uncached);

    return 0;
}

static void
_decode_session4(struct sk_buff *skb, struct flowi *fl, int reverse)
{
    const struct iphdr *iph = ip_hdr(skb);
    u8 *xprth = skb_network_header(skb) + iph->ihl * 4;
    struct flowi4 *fl4 = &fl->u.ip4;

    memset(fl4, 0, sizeof(struct flowi4));
    fl4->flowi4_mark = skb->mark;

    if (!ip_is_fragment(iph)) {
        switch (iph->protocol) {
        case IPPROTO_UDP:
        case IPPROTO_UDPLITE:
        case IPPROTO_TCP:
        case IPPROTO_SCTP:
        case IPPROTO_DCCP:
            if (xprth + 4 < skb->data ||
                pskb_may_pull(skb, xprth + 4 - skb->data)) {
                __be16 *ports = (__be16 *)xprth;

                fl4->fl4_sport = ports[!!reverse];
                fl4->fl4_dport = ports[!reverse];
            }
            break;

        case IPPROTO_ICMP:
            if (pskb_may_pull(skb, xprth + 2 - skb->data)) {
                u8 *icmp = xprth;

                fl4->fl4_icmp_type = icmp[0];
                fl4->fl4_icmp_code = icmp[1];
            }
            break;

        case IPPROTO_ESP:
            if (pskb_may_pull(skb, xprth + 4 - skb->data)) {
                __be32 *ehdr = (__be32 *)xprth;

                fl4->fl4_ipsec_spi = ehdr[0];
            }
            break;

        case IPPROTO_AH:
            if (pskb_may_pull(skb, xprth + 8 - skb->data)) {
                __be32 *ah_hdr = (__be32 *)xprth;

                fl4->fl4_ipsec_spi = ah_hdr[1];
            }
            break;

        case IPPROTO_COMP:
            if (pskb_may_pull(skb, xprth + 4 - skb->data)) {
                __be16 *ipcomp_hdr = (__be16 *)xprth;

                fl4->fl4_ipsec_spi = htonl(ntohs(ipcomp_hdr[1]));
            }
            break;

        case IPPROTO_GRE:
            if (pskb_may_pull(skb, xprth + 12 - skb->data)) {
                __be16 *greflags = (__be16 *)xprth;
                __be32 *gre_hdr = (__be32 *)xprth;

                if (greflags[0] & GRE_KEY) {
                    if (greflags[0] & GRE_CSUM)
                        gre_hdr++;
                    fl4->fl4_gre_key = gre_hdr[1];
                }
            }
            break;

        default:
            fl4->fl4_ipsec_spi = 0;
            break;
        }
    }
    fl4->flowi4_proto = iph->protocol;
    fl4->daddr = reverse ? iph->saddr : iph->daddr;
    fl4->saddr = reverse ? iph->daddr : iph->saddr;
    fl4->flowi4_tos = iph->tos;
}

static inline int xfrm4_garbage_collect(struct dst_ops *ops)
{
    struct net *net = container_of(ops, struct net, xfrm.xfrm4_dst_ops);

    xfrm4_policy_afinfo.garbage_collect(net);
    return (dst_entries_get_slow(ops) > ops->gc_thresh * 2);
}

static void xfrm4_update_pmtu(struct dst_entry *dst, struct sock *sk,
                  struct sk_buff *skb, u32 mtu)
{
    struct xfrm_dst *xdst = (struct xfrm_dst *)dst;
    struct dst_entry *path = xdst->route;

    path->ops->update_pmtu(path, sk, skb, mtu);
}

static void xfrm4_redirect(struct dst_entry *dst, struct sock *sk,
               struct sk_buff *skb)
{
    struct xfrm_dst *xdst = (struct xfrm_dst *)dst;
    struct dst_entry *path = xdst->route;

    path->ops->redirect(path, sk, skb);
}

static void xfrm4_dst_destroy(struct dst_entry *dst)
{
    struct xfrm_dst *xdst = (struct xfrm_dst *)dst;

    dst_destroy_metrics_generic(dst);

    xfrm_dst_destroy(xdst);
}

static void xfrm4_dst_ifdown(struct dst_entry *dst, struct net_device *dev,
                 int unregister)
{
    if (!unregister)
        return;

    xfrm_dst_ifdown(dst, dev);
}

static struct dst_ops xfrm4_dst_ops = {
    .family =       AF_INET,
    .protocol =     cpu_to_be16(ETH_P_IP),
    .gc =           xfrm4_garbage_collect,
    .update_pmtu =      xfrm4_update_pmtu,
    .redirect =     xfrm4_redirect,
    .cow_metrics =      dst_cow_metrics_generic,
    .destroy =      xfrm4_dst_destroy,
    .ifdown =       xfrm4_dst_ifdown,
    .local_out =        __ip_local_out,
    .gc_thresh =        1024,
};

static struct xfrm_policy_afinfo xfrm4_policy_afinfo = {
    .family =       AF_INET,
    .dst_ops =      &xfrm4_dst_ops,
    .dst_lookup =       xfrm4_dst_lookup,
    .get_saddr =        xfrm4_get_saddr,
    .decode_session =   _decode_session4,
    .get_tos =      xfrm4_get_tos,
    .init_path =        xfrm4_init_path,
    .fill_dst =     xfrm4_fill_dst,
    .blackhole_route =  ipv4_blackhole_route,
};

#ifdef CONFIG_SYSCTL
static struct ctl_table xfrm4_policy_table[] = {
    {
        .procname       = "xfrm4_gc_thresh",
        .data           = &init_net.xfrm.xfrm4_dst_ops.gc_thresh,
        .maxlen         = sizeof(int),
        .mode           = 0644,
        .proc_handler   = proc_dointvec,
    },
    { }
};

static struct ctl_table_header *sysctl_hdr;
#endif

static void __init xfrm4_policy_init(void)
{
    xfrm_policy_register_afinfo(&xfrm4_policy_afinfo);
}

static void __exit xfrm4_policy_fini(void)
{
#ifdef CONFIG_SYSCTL
    if (sysctl_hdr)
        unregister_net_sysctl_table(sysctl_hdr);
#endif
    xfrm_policy_unregister_afinfo(&xfrm4_policy_afinfo);
}

void __init xfrm4_init(void)
{
    dst_entries_init(&xfrm4_dst_ops);

    xfrm4_state_init();
    xfrm4_policy_init();
#ifdef CONFIG_SYSCTL
    sysctl_hdr = register_net_sysctl(&init_net, "net/ipv4",
                     xfrm4_policy_table);
#endif
}