nf_nat_l3proto_ipv6.c

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/*
 * Copyright (c) 2011 Patrick McHardy <[email protected]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Development of IPv6 NAT funded by Astaro.
 */
#include <linux/types.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/ipv6.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv6.h>
#include <net/secure_seq.h>
#include <net/checksum.h>
#include <net/ip6_checksum.h>
#include <net/ip6_route.h>
#include <net/ipv6.h>

#include <net/netfilter/nf_conntrack_core.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_nat_core.h>
#include <net/netfilter/nf_nat_l3proto.h>
#include <net/netfilter/nf_nat_l4proto.h>

static const struct nf_nat_l3proto nf_nat_l3proto_ipv6;

#ifdef CONFIG_XFRM
static void nf_nat_ipv6_decode_session(struct sk_buff *skb,
                       const struct nf_conn *ct,
                       enum ip_conntrack_dir dir,
                       unsigned long statusbit,
                       struct flowi *fl)
{
    const struct nf_conntrack_tuple *t = &ct->tuplehash[dir].tuple;
    struct flowi6 *fl6 = &fl->u.ip6;

    if (ct->status & statusbit) {
        fl6->daddr = t->dst.u3.in6;
        if (t->dst.protonum == IPPROTO_TCP ||
            t->dst.protonum == IPPROTO_UDP ||
            t->dst.protonum == IPPROTO_UDPLITE ||
            t->dst.protonum == IPPROTO_DCCP ||
            t->dst.protonum == IPPROTO_SCTP)
            fl6->fl6_dport = t->dst.u.all;
    }

    statusbit ^= IPS_NAT_MASK;

    if (ct->status & statusbit) {
        fl6->saddr = t->src.u3.in6;
        if (t->dst.protonum == IPPROTO_TCP ||
            t->dst.protonum == IPPROTO_UDP ||
            t->dst.protonum == IPPROTO_UDPLITE ||
            t->dst.protonum == IPPROTO_DCCP ||
            t->dst.protonum == IPPROTO_SCTP)
            fl6->fl6_sport = t->src.u.all;
    }
}
#endif

static bool nf_nat_ipv6_in_range(const struct nf_conntrack_tuple *t,
                 const struct nf_nat_range *range)
{
    return ipv6_addr_cmp(&t->src.u3.in6, &range->min_addr.in6) >= 0 &&
           ipv6_addr_cmp(&t->src.u3.in6, &range->max_addr.in6) <= 0;
}

static u32 nf_nat_ipv6_secure_port(const struct nf_conntrack_tuple *t,
                   __be16 dport)
{
    return secure_ipv6_port_ephemeral(t->src.u3.ip6, t->dst.u3.ip6, dport);
}

static bool nf_nat_ipv6_manip_pkt(struct sk_buff *skb,
                  unsigned int iphdroff,
                  const struct nf_nat_l4proto *l4proto,
                  const struct nf_conntrack_tuple *target,
                  enum nf_nat_manip_type maniptype)
{
    struct ipv6hdr *ipv6h;
    __be16 frag_off;
    int hdroff;
    u8 nexthdr;

    if (!skb_make_writable(skb, iphdroff + sizeof(*ipv6h)))
        return false;

    ipv6h = (void *)skb->data + iphdroff;
    nexthdr = ipv6h->nexthdr;
    hdroff = ipv6_skip_exthdr(skb, iphdroff + sizeof(*ipv6h),
                  &nexthdr, &frag_off);
    if (hdroff < 0)
        goto manip_addr;

    if ((frag_off & htons(~0x7)) == 0 &&
        !l4proto->manip_pkt(skb, &nf_nat_l3proto_ipv6, iphdroff, hdroff,
                target, maniptype))
        return false;
manip_addr:
    if (maniptype == NF_NAT_MANIP_SRC)
        ipv6h->saddr = target->src.u3.in6;
    else
        ipv6h->daddr = target->dst.u3.in6;

    return true;
}

static void nf_nat_ipv6_csum_update(struct sk_buff *skb,
                    unsigned int iphdroff, __sum16 *check,
                    const struct nf_conntrack_tuple *t,
                    enum nf_nat_manip_type maniptype)
{
    const struct ipv6hdr *ipv6h = (struct ipv6hdr *)(skb->data + iphdroff);
    const struct in6_addr *oldip, *newip;

    if (maniptype == NF_NAT_MANIP_SRC) {
        oldip = &ipv6h->saddr;
        newip = &t->src.u3.in6;
    } else {
        oldip = &ipv6h->daddr;
        newip = &t->dst.u3.in6;
    }
    inet_proto_csum_replace16(check, skb, oldip->s6_addr32,
                  newip->s6_addr32, 1);
}

static void nf_nat_ipv6_csum_recalc(struct sk_buff *skb,
                    u8 proto, void *data, __sum16 *check,
                    int datalen, int oldlen)
{
    const struct ipv6hdr *ipv6h = ipv6_hdr(skb);
    struct rt6_info *rt = (struct rt6_info *)skb_dst(skb);

    if (skb->ip_summed != CHECKSUM_PARTIAL) {
        if (!(rt->rt6i_flags & RTF_LOCAL) &&
            (!skb->dev || skb->dev->features & NETIF_F_V6_CSUM)) {
            skb->ip_summed = CHECKSUM_PARTIAL;
            skb->csum_start = skb_headroom(skb) +
                      skb_network_offset(skb) +
                      (data - (void *)skb->data);
            skb->csum_offset = (void *)check - data;
            *check = ~csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr,
                          datalen, proto, 0);
        } else {
            *check = 0;
            *check = csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr,
                         datalen, proto,
                         csum_partial(data, datalen,
                                  0));
            if (proto == IPPROTO_UDP && !*check)
                *check = CSUM_MANGLED_0;
        }
    } else
        inet_proto_csum_replace2(check, skb,
                     htons(oldlen), htons(datalen), 1);
}

static int nf_nat_ipv6_nlattr_to_range(struct nlattr *tb[],
                       struct nf_nat_range *range)
{
    if (tb[CTA_NAT_V6_MINIP]) {
        nla_memcpy(&range->min_addr.ip6, tb[CTA_NAT_V6_MINIP],
               sizeof(struct in6_addr));
        range->flags |= NF_NAT_RANGE_MAP_IPS;
    }

    if (tb[CTA_NAT_V6_MAXIP])
        nla_memcpy(&range->max_addr.ip6, tb[CTA_NAT_V6_MAXIP],
               sizeof(struct in6_addr));
    else
        range->max_addr = range->min_addr;

    return 0;
}

static const struct nf_nat_l3proto nf_nat_l3proto_ipv6 = {
    .l3proto        = NFPROTO_IPV6,
    .secure_port        = nf_nat_ipv6_secure_port,
    .in_range       = nf_nat_ipv6_in_range,
    .manip_pkt      = nf_nat_ipv6_manip_pkt,
    .csum_update        = nf_nat_ipv6_csum_update,
    .csum_recalc        = nf_nat_ipv6_csum_recalc,
    .nlattr_to_range    = nf_nat_ipv6_nlattr_to_range,
#ifdef CONFIG_XFRM
    .decode_session = nf_nat_ipv6_decode_session,
#endif
};

int nf_nat_icmpv6_reply_translation(struct sk_buff *skb,
                    struct nf_conn *ct,
                    enum ip_conntrack_info ctinfo,
                    unsigned int hooknum,
                    unsigned int hdrlen)
{
    struct {
        struct icmp6hdr icmp6;
        struct ipv6hdr  ip6;
    } *inside;
    enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
    enum nf_nat_manip_type manip = HOOK2MANIP(hooknum);
    const struct nf_nat_l4proto *l4proto;
    struct nf_conntrack_tuple target;
    unsigned long statusbit;

    NF_CT_ASSERT(ctinfo == IP_CT_RELATED || ctinfo == IP_CT_RELATED_REPLY);

    if (!skb_make_writable(skb, hdrlen + sizeof(*inside)))
        return 0;
    if (nf_ip6_checksum(skb, hooknum, hdrlen, IPPROTO_ICMPV6))
        return 0;

    inside = (void *)skb->data + hdrlen;
    if (inside->icmp6.icmp6_type == NDISC_REDIRECT) {
        if ((ct->status & IPS_NAT_DONE_MASK) != IPS_NAT_DONE_MASK)
            return 0;
        if (ct->status & IPS_NAT_MASK)
            return 0;
    }

    if (manip == NF_NAT_MANIP_SRC)
        statusbit = IPS_SRC_NAT;
    else
        statusbit = IPS_DST_NAT;

    /* Invert if this is reply direction */
    if (dir == IP_CT_DIR_REPLY)
        statusbit ^= IPS_NAT_MASK;

    if (!(ct->status & statusbit))
        return 1;

    l4proto = __nf_nat_l4proto_find(NFPROTO_IPV6, inside->ip6.nexthdr);
    if (!nf_nat_ipv6_manip_pkt(skb, hdrlen + sizeof(inside->icmp6),
                   l4proto, &ct->tuplehash[!dir].tuple, !manip))
        return 0;

    if (skb->ip_summed != CHECKSUM_PARTIAL) {
        struct ipv6hdr *ipv6h = ipv6_hdr(skb);
        inside = (void *)skb->data + hdrlen;
        inside->icmp6.icmp6_cksum = 0;
        inside->icmp6.icmp6_cksum =
            csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr,
                    skb->len - hdrlen, IPPROTO_ICMPV6,
                    csum_partial(&inside->icmp6,
                             skb->len - hdrlen, 0));
    }

    nf_ct_invert_tuplepr(&target, &ct->tuplehash[!dir].tuple);
    l4proto = __nf_nat_l4proto_find(NFPROTO_IPV6, IPPROTO_ICMPV6);
    if (!nf_nat_ipv6_manip_pkt(skb, 0, l4proto, &target, manip))
        return 0;

    return 1;
}
EXPORT_SYMBOL_GPL(nf_nat_icmpv6_reply_translation);

static int __init nf_nat_l3proto_ipv6_init(void)
{
    int err;

    err = nf_nat_l4proto_register(NFPROTO_IPV6, &nf_nat_l4proto_icmpv6);
    if (err < 0)
        goto err1;
    err = nf_nat_l3proto_register(&nf_nat_l3proto_ipv6);
    if (err < 0)
        goto err2;
    return err;

err2:
    nf_nat_l4proto_unregister(NFPROTO_IPV6, &nf_nat_l4proto_icmpv6);
err1:
    return err;
}

static void __exit nf_nat_l3proto_ipv6_exit(void)
{
    nf_nat_l3proto_unregister(&nf_nat_l3proto_ipv6);
    nf_nat_l4proto_unregister(NFPROTO_IPV6, &nf_nat_l4proto_icmpv6);
}

MODULE_LICENSE("GPL");
MODULE_ALIAS("nf-nat-" __stringify(AF_INET6));

module_init(nf_nat_l3proto_ipv6_init);
module_exit(nf_nat_l3proto_ipv6_exit);