br_netfilter.c

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/*
 *  Handle firewalling
 *  Linux ethernet bridge
 *
 *  Authors:
 *  Lennert Buytenhek       <[email protected]>
 *  Bart De Schuymer        <[email protected]>
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version
 *  2 of the License, or (at your option) any later version.
 *
 *  Lennert dedicates this file to Kerstin Wurdinger.
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/ip.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/if_arp.h>
#include <linux/if_ether.h>
#include <linux/if_vlan.h>
#include <linux/if_pppox.h>
#include <linux/ppp_defs.h>
#include <linux/netfilter_bridge.h>
#include <linux/netfilter_ipv4.h>
#include <linux/netfilter_ipv6.h>
#include <linux/netfilter_arp.h>
#include <linux/in_route.h>
#include <linux/inetdevice.h>

#include <net/ip.h>
#include <net/ipv6.h>
#include <net/route.h>

#include <asm/uaccess.h>
#include "br_private.h"
#ifdef CONFIG_SYSCTL
#include <linux/sysctl.h>
#endif

#define skb_origaddr(skb)    (((struct bridge_skb_cb *) \
                 (skb->nf_bridge->data))->daddr.ipv4)
#define store_orig_dstaddr(skb)  (skb_origaddr(skb) = ip_hdr(skb)->daddr)
#define dnat_took_place(skb)     (skb_origaddr(skb) != ip_hdr(skb)->daddr)

#ifdef CONFIG_SYSCTL
static struct ctl_table_header *brnf_sysctl_header;
static int brnf_call_iptables __read_mostly = 1;
static int brnf_call_ip6tables __read_mostly = 1;
static int brnf_call_arptables __read_mostly = 1;
static int brnf_filter_vlan_tagged __read_mostly = 0;
static int brnf_filter_pppoe_tagged __read_mostly = 0;
static int brnf_pass_vlan_indev __read_mostly = 0;
#else
#define brnf_call_iptables 1
#define brnf_call_ip6tables 1
#define brnf_call_arptables 1
#define brnf_filter_vlan_tagged 0
#define brnf_filter_pppoe_tagged 0
#define brnf_pass_vlan_indev 0
#endif

#define IS_IP(skb) \
    (!vlan_tx_tag_present(skb) && skb->protocol == htons(ETH_P_IP))

#define IS_IPV6(skb) \
    (!vlan_tx_tag_present(skb) && skb->protocol == htons(ETH_P_IPV6))

#define IS_ARP(skb) \
    (!vlan_tx_tag_present(skb) && skb->protocol == htons(ETH_P_ARP))

static inline __be16 vlan_proto(const struct sk_buff *skb)
{
    if (vlan_tx_tag_present(skb))
        return skb->protocol;
    else if (skb->protocol == htons(ETH_P_8021Q))
        return vlan_eth_hdr(skb)->h_vlan_encapsulated_proto;
    else
        return 0;
}

#define IS_VLAN_IP(skb) \
    (vlan_proto(skb) == htons(ETH_P_IP) && \
     brnf_filter_vlan_tagged)

#define IS_VLAN_IPV6(skb) \
    (vlan_proto(skb) == htons(ETH_P_IPV6) && \
     brnf_filter_vlan_tagged)

#define IS_VLAN_ARP(skb) \
    (vlan_proto(skb) == htons(ETH_P_ARP) && \
     brnf_filter_vlan_tagged)

static inline __be16 pppoe_proto(const struct sk_buff *skb)
{
    return *((__be16 *)(skb_mac_header(skb) + ETH_HLEN +
                sizeof(struct pppoe_hdr)));
}

#define IS_PPPOE_IP(skb) \
    (skb->protocol == htons(ETH_P_PPP_SES) && \
     pppoe_proto(skb) == htons(PPP_IP) && \
     brnf_filter_pppoe_tagged)

#define IS_PPPOE_IPV6(skb) \
    (skb->protocol == htons(ETH_P_PPP_SES) && \
     pppoe_proto(skb) == htons(PPP_IPV6) && \
     brnf_filter_pppoe_tagged)

static void fake_update_pmtu(struct dst_entry *dst, struct sock *sk,
                 struct sk_buff *skb, u32 mtu)
{
}

static void fake_redirect(struct dst_entry *dst, struct sock *sk,
              struct sk_buff *skb)
{
}

static u32 *fake_cow_metrics(struct dst_entry *dst, unsigned long old)
{
    return NULL;
}

static struct neighbour *fake_neigh_lookup(const struct dst_entry *dst,
                       struct sk_buff *skb,
                       const void *daddr)
{
    return NULL;
}

static unsigned int fake_mtu(const struct dst_entry *dst)
{
    return dst->dev->mtu;
}

static struct dst_ops fake_dst_ops = {
    .family =       AF_INET,
    .protocol =     cpu_to_be16(ETH_P_IP),
    .update_pmtu =      fake_update_pmtu,
    .redirect =     fake_redirect,
    .cow_metrics =      fake_cow_metrics,
    .neigh_lookup =     fake_neigh_lookup,
    .mtu =          fake_mtu,
};

/*
 * Initialize bogus route table used to keep netfilter happy.
 * Currently, we fill in the PMTU entry because netfilter
 * refragmentation needs it, and the rt_flags entry because
 * ipt_REJECT needs it.  Future netfilter modules might
 * require us to fill additional fields.
 */
static const u32 br_dst_default_metrics[RTAX_MAX] = {
    [RTAX_MTU - 1] = 1500,
};

void br_netfilter_rtable_init(struct net_bridge *br)
{
    struct rtable *rt = &br->fake_rtable;

    atomic_set(&rt->dst.__refcnt, 1);
    rt->dst.dev = br->dev;
    rt->dst.path = &rt->dst;
    dst_init_metrics(&rt->dst, br_dst_default_metrics, true);
    rt->dst.flags   = DST_NOXFRM | DST_NOPEER | DST_FAKE_RTABLE;
    rt->dst.ops = &fake_dst_ops;
}

static inline struct rtable *bridge_parent_rtable(const struct net_device *dev)
{
    struct net_bridge_port *port;

    port = br_port_get_rcu(dev);
    return port ? &port->br->fake_rtable : NULL;
}

static inline struct net_device *bridge_parent(const struct net_device *dev)
{
    struct net_bridge_port *port;

    port = br_port_get_rcu(dev);
    return port ? port->br->dev : NULL;
}

static inline struct nf_bridge_info *nf_bridge_alloc(struct sk_buff *skb)
{
    skb->nf_bridge = kzalloc(sizeof(struct nf_bridge_info), GFP_ATOMIC);
    if (likely(skb->nf_bridge))
        atomic_set(&(skb->nf_bridge->use), 1);

    return skb->nf_bridge;
}

static inline struct nf_bridge_info *nf_bridge_unshare(struct sk_buff *skb)
{
    struct nf_bridge_info *nf_bridge = skb->nf_bridge;

    if (atomic_read(&nf_bridge->use) > 1) {
        struct nf_bridge_info *tmp = nf_bridge_alloc(skb);

        if (tmp) {
            memcpy(tmp, nf_bridge, sizeof(struct nf_bridge_info));
            atomic_set(&tmp->use, 1);
        }
        nf_bridge_put(nf_bridge);
        nf_bridge = tmp;
    }
    return nf_bridge;
}

static inline void nf_bridge_push_encap_header(struct sk_buff *skb)
{
    unsigned int len = nf_bridge_encap_header_len(skb);

    skb_push(skb, len);
    skb->network_header -= len;
}

static inline void nf_bridge_pull_encap_header(struct sk_buff *skb)
{
    unsigned int len = nf_bridge_encap_header_len(skb);

    skb_pull(skb, len);
    skb->network_header += len;
}

static inline void nf_bridge_pull_encap_header_rcsum(struct sk_buff *skb)
{
    unsigned int len = nf_bridge_encap_header_len(skb);

    skb_pull_rcsum(skb, len);
    skb->network_header += len;
}

static inline void nf_bridge_save_header(struct sk_buff *skb)
{
    int header_size = ETH_HLEN + nf_bridge_encap_header_len(skb);

    skb_copy_from_linear_data_offset(skb, -header_size,
                     skb->nf_bridge->data, header_size);
}

static inline void nf_bridge_update_protocol(struct sk_buff *skb)
{
    if (skb->nf_bridge->mask & BRNF_8021Q)
        skb->protocol = htons(ETH_P_8021Q);
    else if (skb->nf_bridge->mask & BRNF_PPPoE)
        skb->protocol = htons(ETH_P_PPP_SES);
}

/* When handing a packet over to the IP layer
 * check whether we have a skb that is in the
 * expected format
 */

static int br_parse_ip_options(struct sk_buff *skb)
{
    struct ip_options *opt;
    const struct iphdr *iph;
    struct net_device *dev = skb->dev;
    u32 len;

    if (!pskb_may_pull(skb, sizeof(struct iphdr)))
        goto inhdr_error;

    iph = ip_hdr(skb);
    opt = &(IPCB(skb)->opt);

    /* Basic sanity checks */
    if (iph->ihl < 5 || iph->version != 4)
        goto inhdr_error;

    if (!pskb_may_pull(skb, iph->ihl*4))
        goto inhdr_error;

    iph = ip_hdr(skb);
    if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl)))
        goto inhdr_error;

    len = ntohs(iph->tot_len);
    if (skb->len < len) {
        IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INTRUNCATEDPKTS);
        goto drop;
    } else if (len < (iph->ihl*4))
        goto inhdr_error;

    if (pskb_trim_rcsum(skb, len)) {
        IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS);
        goto drop;
    }

    memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
    if (iph->ihl == 5)
        return 0;

    opt->optlen = iph->ihl*4 - sizeof(struct iphdr);
    if (ip_options_compile(dev_net(dev), opt, skb))
        goto inhdr_error;

    /* Check correct handling of SRR option */
    if (unlikely(opt->srr)) {
        struct in_device *in_dev = __in_dev_get_rcu(dev);
        if (in_dev && !IN_DEV_SOURCE_ROUTE(in_dev))
            goto drop;

        if (ip_options_rcv_srr(skb))
            goto drop;
    }

    return 0;

inhdr_error:
    IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INHDRERRORS);
drop:
    return -1;
}

/* Fill in the header for fragmented IP packets handled by
 * the IPv4 connection tracking code.
 */
int nf_bridge_copy_header(struct sk_buff *skb)
{
    int err;
    unsigned int header_size;

    nf_bridge_update_protocol(skb);
    header_size = ETH_HLEN + nf_bridge_encap_header_len(skb);
    err = skb_cow_head(skb, header_size);
    if (err)
        return err;

    skb_copy_to_linear_data_offset(skb, -header_size,
                       skb->nf_bridge->data, header_size);
    __skb_push(skb, nf_bridge_encap_header_len(skb));
    return 0;
}

/* PF_BRIDGE/PRE_ROUTING *********************************************/
/* Undo the changes made for ip6tables PREROUTING and continue the
 * bridge PRE_ROUTING hook. */
static int br_nf_pre_routing_finish_ipv6(struct sk_buff *skb)
{
    struct nf_bridge_info *nf_bridge = skb->nf_bridge;
    struct rtable *rt;

    if (nf_bridge->mask & BRNF_PKT_TYPE) {
        skb->pkt_type = PACKET_OTHERHOST;
        nf_bridge->mask ^= BRNF_PKT_TYPE;
    }
    nf_bridge->mask ^= BRNF_NF_BRIDGE_PREROUTING;

    rt = bridge_parent_rtable(nf_bridge->physindev);
    if (!rt) {
        kfree_skb(skb);
        return 0;
    }
    skb_dst_set_noref(skb, &rt->dst);

    skb->dev = nf_bridge->physindev;
    nf_bridge_update_protocol(skb);
    nf_bridge_push_encap_header(skb);
    NF_HOOK_THRESH(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING, skb, skb->dev, NULL,
               br_handle_frame_finish, 1);

    return 0;
}

/* Obtain the correct destination MAC address, while preserving the original
 * source MAC address. If we already know this address, we just copy it. If we
 * don't, we use the neighbour framework to find out. In both cases, we make
 * sure that br_handle_frame_finish() is called afterwards.
 */
static int br_nf_pre_routing_finish_bridge(struct sk_buff *skb)
{
    struct nf_bridge_info *nf_bridge = skb->nf_bridge;
    struct neighbour *neigh;
    struct dst_entry *dst;

    skb->dev = bridge_parent(skb->dev);
    if (!skb->dev)
        goto free_skb;
    dst = skb_dst(skb);
    neigh = dst_neigh_lookup_skb(dst, skb);
    if (neigh) {
        int ret;

        if (neigh->hh.hh_len) {
            neigh_hh_bridge(&neigh->hh, skb);
            skb->dev = nf_bridge->physindev;
            ret = br_handle_frame_finish(skb);
        } else {
            /* the neighbour function below overwrites the complete
             * MAC header, so we save the Ethernet source address and
             * protocol number.
             */
            skb_copy_from_linear_data_offset(skb,
                             -(ETH_HLEN-ETH_ALEN),
                             skb->nf_bridge->data,
                             ETH_HLEN-ETH_ALEN);
            /* tell br_dev_xmit to continue with forwarding */
            nf_bridge->mask |= BRNF_BRIDGED_DNAT;
            ret = neigh->output(neigh, skb);
        }
        neigh_release(neigh);
        return ret;
    }
free_skb:
    kfree_skb(skb);
    return 0;
}

/* This requires some explaining. If DNAT has taken place,
 * we will need to fix up the destination Ethernet address.
 *
 * There are two cases to consider:
 * 1. The packet was DNAT'ed to a device in the same bridge
 *    port group as it was received on. We can still bridge
 *    the packet.
 * 2. The packet was DNAT'ed to a different device, either
 *    a non-bridged device or another bridge port group.
 *    The packet will need to be routed.
 *
 * The correct way of distinguishing between these two cases is to
 * call ip_route_input() and to look at skb->dst->dev, which is
 * changed to the destination device if ip_route_input() succeeds.
 *
 * Let's first consider the case that ip_route_input() succeeds:
 *
 * If the output device equals the logical bridge device the packet
 * came in on, we can consider this bridging. The corresponding MAC
 * address will be obtained in br_nf_pre_routing_finish_bridge.
 * Otherwise, the packet is considered to be routed and we just
 * change the destination MAC address so that the packet will
 * later be passed up to the IP stack to be routed. For a redirected
 * packet, ip_route_input() will give back the localhost as output device,
 * which differs from the bridge device.
 *
 * Let's now consider the case that ip_route_input() fails:
 *
 * This can be because the destination address is martian, in which case
 * the packet will be dropped.
 * If IP forwarding is disabled, ip_route_input() will fail, while
 * ip_route_output_key() can return success. The source
 * address for ip_route_output_key() is set to zero, so ip_route_output_key()
 * thinks we're handling a locally generated packet and won't care
 * if IP forwarding is enabled. If the output device equals the logical bridge
 * device, we proceed as if ip_route_input() succeeded. If it differs from the
 * logical bridge port or if ip_route_output_key() fails we drop the packet.
 */
static int br_nf_pre_routing_finish(struct sk_buff *skb)
{
    struct net_device *dev = skb->dev;
    struct iphdr *iph = ip_hdr(skb);
    struct nf_bridge_info *nf_bridge = skb->nf_bridge;
    struct rtable *rt;
    int err;

    if (nf_bridge->mask & BRNF_PKT_TYPE) {
        skb->pkt_type = PACKET_OTHERHOST;
        nf_bridge->mask ^= BRNF_PKT_TYPE;
    }
    nf_bridge->mask ^= BRNF_NF_BRIDGE_PREROUTING;
    if (dnat_took_place(skb)) {
        if ((err = ip_route_input(skb, iph->daddr, iph->saddr, iph->tos, dev))) {
            struct in_device *in_dev = __in_dev_get_rcu(dev);

            /* If err equals -EHOSTUNREACH the error is due to a
             * martian destination or due to the fact that
             * forwarding is disabled. For most martian packets,
             * ip_route_output_key() will fail. It won't fail for 2 types of
             * martian destinations: loopback destinations and destination
             * 0.0.0.0. In both cases the packet will be dropped because the
             * destination is the loopback device and not the bridge. */
            if (err != -EHOSTUNREACH || !in_dev || IN_DEV_FORWARD(in_dev))
                goto free_skb;

            rt = ip_route_output(dev_net(dev), iph->daddr, 0,
                         RT_TOS(iph->tos), 0);
            if (!IS_ERR(rt)) {
                /* - Bridged-and-DNAT'ed traffic doesn't
                 *   require ip_forwarding. */
                if (rt->dst.dev == dev) {
                    skb_dst_set(skb, &rt->dst);
                    goto bridged_dnat;
                }
                ip_rt_put(rt);
            }
free_skb:
            kfree_skb(skb);
            return 0;
        } else {
            if (skb_dst(skb)->dev == dev) {
bridged_dnat:
                skb->dev = nf_bridge->physindev;
                nf_bridge_update_protocol(skb);
                nf_bridge_push_encap_header(skb);
                NF_HOOK_THRESH(NFPROTO_BRIDGE,
                           NF_BR_PRE_ROUTING,
                           skb, skb->dev, NULL,
                           br_nf_pre_routing_finish_bridge,
                           1);
                return 0;
            }
            memcpy(eth_hdr(skb)->h_dest, dev->dev_addr, ETH_ALEN);
            skb->pkt_type = PACKET_HOST;
        }
    } else {
        rt = bridge_parent_rtable(nf_bridge->physindev);
        if (!rt) {
            kfree_skb(skb);
            return 0;
        }
        skb_dst_set_noref(skb, &rt->dst);
    }

    skb->dev = nf_bridge->physindev;
    nf_bridge_update_protocol(skb);
    nf_bridge_push_encap_header(skb);
    NF_HOOK_THRESH(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING, skb, skb->dev, NULL,
               br_handle_frame_finish, 1);

    return 0;
}

static struct net_device *brnf_get_logical_dev(struct sk_buff *skb, const struct net_device *dev)
{
    struct net_device *vlan, *br;

    br = bridge_parent(dev);
    if (brnf_pass_vlan_indev == 0 || !vlan_tx_tag_present(skb))
        return br;

    vlan = __vlan_find_dev_deep(br, vlan_tx_tag_get(skb) & VLAN_VID_MASK);

    return vlan ? vlan : br;
}

/* Some common code for IPv4/IPv6 */
static struct net_device *setup_pre_routing(struct sk_buff *skb)
{
    struct nf_bridge_info *nf_bridge = skb->nf_bridge;

    if (skb->pkt_type == PACKET_OTHERHOST) {
        skb->pkt_type = PACKET_HOST;
        nf_bridge->mask |= BRNF_PKT_TYPE;
    }

    nf_bridge->mask |= BRNF_NF_BRIDGE_PREROUTING;
    nf_bridge->physindev = skb->dev;
    skb->dev = brnf_get_logical_dev(skb, skb->dev);
    if (skb->protocol == htons(ETH_P_8021Q))
        nf_bridge->mask |= BRNF_8021Q;
    else if (skb->protocol == htons(ETH_P_PPP_SES))
        nf_bridge->mask |= BRNF_PPPoE;

    return skb->dev;
}

/* We only check the length. A bridge shouldn't do any hop-by-hop stuff anyway */
static int check_hbh_len(struct sk_buff *skb)
{
    unsigned char *raw = (u8 *)(ipv6_hdr(skb) + 1);
    u32 pkt_len;
    const unsigned char *nh = skb_network_header(skb);
    int off = raw - nh;
    int len = (raw[1] + 1) << 3;

    if ((raw + len) - skb->data > skb_headlen(skb))
        goto bad;

    off += 2;
    len -= 2;

    while (len > 0) {
        int optlen = nh[off + 1] + 2;

        switch (nh[off]) {
        case IPV6_TLV_PAD1:
            optlen = 1;
            break;

        case IPV6_TLV_PADN:
            break;

        case IPV6_TLV_JUMBO:
            if (nh[off + 1] != 4 || (off & 3) != 2)
                goto bad;
            pkt_len = ntohl(*(__be32 *) (nh + off + 2));
            if (pkt_len <= IPV6_MAXPLEN ||
                ipv6_hdr(skb)->payload_len)
                goto bad;
            if (pkt_len > skb->len - sizeof(struct ipv6hdr))
                goto bad;
            if (pskb_trim_rcsum(skb,
                        pkt_len + sizeof(struct ipv6hdr)))
                goto bad;
            nh = skb_network_header(skb);
            break;
        default:
            if (optlen > len)
                goto bad;
            break;
        }
        off += optlen;
        len -= optlen;
    }
    if (len == 0)
        return 0;
bad:
    return -1;

}

/* Replicate the checks that IPv6 does on packet reception and pass the packet
 * to ip6tables, which doesn't support NAT, so things are fairly simple. */
static unsigned int br_nf_pre_routing_ipv6(unsigned int hook,
                       struct sk_buff *skb,
                       const struct net_device *in,
                       const struct net_device *out,
                       int (*okfn)(struct sk_buff *))
{
    const struct ipv6hdr *hdr;
    u32 pkt_len;

    if (skb->len < sizeof(struct ipv6hdr))
        return NF_DROP;

    if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
        return NF_DROP;

    hdr = ipv6_hdr(skb);

    if (hdr->version != 6)
        return NF_DROP;

    pkt_len = ntohs(hdr->payload_len);

    if (pkt_len || hdr->nexthdr != NEXTHDR_HOP) {
        if (pkt_len + sizeof(struct ipv6hdr) > skb->len)
            return NF_DROP;
        if (pskb_trim_rcsum(skb, pkt_len + sizeof(struct ipv6hdr)))
            return NF_DROP;
    }
    if (hdr->nexthdr == NEXTHDR_HOP && check_hbh_len(skb))
        return NF_DROP;

    nf_bridge_put(skb->nf_bridge);
    if (!nf_bridge_alloc(skb))
        return NF_DROP;
    if (!setup_pre_routing(skb))
        return NF_DROP;

    skb->protocol = htons(ETH_P_IPV6);
    NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING, skb, skb->dev, NULL,
        br_nf_pre_routing_finish_ipv6);

    return NF_STOLEN;
}

/* Direct IPv6 traffic to br_nf_pre_routing_ipv6.
 * Replicate the checks that IPv4 does on packet reception.
 * Set skb->dev to the bridge device (i.e. parent of the
 * receiving device) to make netfilter happy, the REDIRECT
 * target in particular.  Save the original destination IP
 * address to be able to detect DNAT afterwards. */
static unsigned int br_nf_pre_routing(unsigned int hook, struct sk_buff *skb,
                      const struct net_device *in,
                      const struct net_device *out,
                      int (*okfn)(struct sk_buff *))
{
    struct net_bridge_port *p;
    struct net_bridge *br;
    __u32 len = nf_bridge_encap_header_len(skb);

    if (unlikely(!pskb_may_pull(skb, len)))
        return NF_DROP;

    p = br_port_get_rcu(in);
    if (p == NULL)
        return NF_DROP;
    br = p->br;

    if (IS_IPV6(skb) || IS_VLAN_IPV6(skb) || IS_PPPOE_IPV6(skb)) {
        if (!brnf_call_ip6tables && !br->nf_call_ip6tables)
            return NF_ACCEPT;

        nf_bridge_pull_encap_header_rcsum(skb);
        return br_nf_pre_routing_ipv6(hook, skb, in, out, okfn);
    }

    if (!brnf_call_iptables && !br->nf_call_iptables)
        return NF_ACCEPT;

    if (!IS_IP(skb) && !IS_VLAN_IP(skb) && !IS_PPPOE_IP(skb))
        return NF_ACCEPT;

    nf_bridge_pull_encap_header_rcsum(skb);

    if (br_parse_ip_options(skb))
        return NF_DROP;

    nf_bridge_put(skb->nf_bridge);
    if (!nf_bridge_alloc(skb))
        return NF_DROP;
    if (!setup_pre_routing(skb))
        return NF_DROP;
    store_orig_dstaddr(skb);
    skb->protocol = htons(ETH_P_IP);

    NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, skb, skb->dev, NULL,
        br_nf_pre_routing_finish);

    return NF_STOLEN;
}


/* PF_BRIDGE/LOCAL_IN ************************************************/
/* The packet is locally destined, which requires a real
 * dst_entry, so detach the fake one.  On the way up, the
 * packet would pass through PRE_ROUTING again (which already
 * took place when the packet entered the bridge), but we
 * register an IPv4 PRE_ROUTING 'sabotage' hook that will
 * prevent this from happening. */
static unsigned int br_nf_local_in(unsigned int hook, struct sk_buff *skb,
                   const struct net_device *in,
                   const struct net_device *out,
                   int (*okfn)(struct sk_buff *))
{
    br_drop_fake_rtable(skb);
    return NF_ACCEPT;
}

/* PF_BRIDGE/FORWARD *************************************************/
static int br_nf_forward_finish(struct sk_buff *skb)
{
    struct nf_bridge_info *nf_bridge = skb->nf_bridge;
    struct net_device *in;

    if (!IS_ARP(skb) && !IS_VLAN_ARP(skb)) {
        in = nf_bridge->physindev;
        if (nf_bridge->mask & BRNF_PKT_TYPE) {
            skb->pkt_type = PACKET_OTHERHOST;
            nf_bridge->mask ^= BRNF_PKT_TYPE;
        }
        nf_bridge_update_protocol(skb);
    } else {
        in = *((struct net_device **)(skb->cb));
    }
    nf_bridge_push_encap_header(skb);

    NF_HOOK_THRESH(NFPROTO_BRIDGE, NF_BR_FORWARD, skb, in,
               skb->dev, br_forward_finish, 1);
    return 0;
}


/* This is the 'purely bridged' case.  For IP, we pass the packet to
 * netfilter with indev and outdev set to the bridge device,
 * but we are still able to filter on the 'real' indev/outdev
 * because of the physdev module. For ARP, indev and outdev are the
 * bridge ports. */
static unsigned int br_nf_forward_ip(unsigned int hook, struct sk_buff *skb,
                     const struct net_device *in,
                     const struct net_device *out,
                     int (*okfn)(struct sk_buff *))
{
    struct nf_bridge_info *nf_bridge;
    struct net_device *parent;
    u_int8_t pf;

    if (!skb->nf_bridge)
        return NF_ACCEPT;

    /* Need exclusive nf_bridge_info since we might have multiple
     * different physoutdevs. */
    if (!nf_bridge_unshare(skb))
        return NF_DROP;

    parent = bridge_parent(out);
    if (!parent)
        return NF_DROP;

    if (IS_IP(skb) || IS_VLAN_IP(skb) || IS_PPPOE_IP(skb))
        pf = NFPROTO_IPV4;
    else if (IS_IPV6(skb) || IS_VLAN_IPV6(skb) || IS_PPPOE_IPV6(skb))
        pf = NFPROTO_IPV6;
    else
        return NF_ACCEPT;

    nf_bridge_pull_encap_header(skb);

    nf_bridge = skb->nf_bridge;
    if (skb->pkt_type == PACKET_OTHERHOST) {
        skb->pkt_type = PACKET_HOST;
        nf_bridge->mask |= BRNF_PKT_TYPE;
    }

    if (pf == NFPROTO_IPV4 && br_parse_ip_options(skb))
        return NF_DROP;

    /* The physdev module checks on this */
    nf_bridge->mask |= BRNF_BRIDGED;
    nf_bridge->physoutdev = skb->dev;
    if (pf == NFPROTO_IPV4)
        skb->protocol = htons(ETH_P_IP);
    else
        skb->protocol = htons(ETH_P_IPV6);

    NF_HOOK(pf, NF_INET_FORWARD, skb, brnf_get_logical_dev(skb, in), parent,
        br_nf_forward_finish);

    return NF_STOLEN;
}

static unsigned int br_nf_forward_arp(unsigned int hook, struct sk_buff *skb,
                      const struct net_device *in,
                      const struct net_device *out,
                      int (*okfn)(struct sk_buff *))
{
    struct net_bridge_port *p;
    struct net_bridge *br;
    struct net_device **d = (struct net_device **)(skb->cb);

    p = br_port_get_rcu(out);
    if (p == NULL)
        return NF_ACCEPT;
    br = p->br;

    if (!brnf_call_arptables && !br->nf_call_arptables)
        return NF_ACCEPT;

    if (!IS_ARP(skb)) {
        if (!IS_VLAN_ARP(skb))
            return NF_ACCEPT;
        nf_bridge_pull_encap_header(skb);
    }

    if (arp_hdr(skb)->ar_pln != 4) {
        if (IS_VLAN_ARP(skb))
            nf_bridge_push_encap_header(skb);
        return NF_ACCEPT;
    }
    *d = (struct net_device *)in;
    NF_HOOK(NFPROTO_ARP, NF_ARP_FORWARD, skb, (struct net_device *)in,
        (struct net_device *)out, br_nf_forward_finish);

    return NF_STOLEN;
}

#if IS_ENABLED(CONFIG_NF_CONNTRACK_IPV4)
static int br_nf_dev_queue_xmit(struct sk_buff *skb)
{
    int ret;

    if (skb->nfct != NULL && skb->protocol == htons(ETH_P_IP) &&
        skb->len + nf_bridge_mtu_reduction(skb) > skb->dev->mtu &&
        !skb_is_gso(skb)) {
        if (br_parse_ip_options(skb))
            /* Drop invalid packet */
            return NF_DROP;
        ret = ip_fragment(skb, br_dev_queue_push_xmit);
    } else
        ret = br_dev_queue_push_xmit(skb);

    return ret;
}
#else
static int br_nf_dev_queue_xmit(struct sk_buff *skb)
{
        return br_dev_queue_push_xmit(skb);
}
#endif

/* PF_BRIDGE/POST_ROUTING ********************************************/
static unsigned int br_nf_post_routing(unsigned int hook, struct sk_buff *skb,
                       const struct net_device *in,
                       const struct net_device *out,
                       int (*okfn)(struct sk_buff *))
{
    struct nf_bridge_info *nf_bridge = skb->nf_bridge;
    struct net_device *realoutdev = bridge_parent(skb->dev);
    u_int8_t pf;

    if (!nf_bridge || !(nf_bridge->mask & BRNF_BRIDGED))
        return NF_ACCEPT;

    if (!realoutdev)
        return NF_DROP;

    if (IS_IP(skb) || IS_VLAN_IP(skb) || IS_PPPOE_IP(skb))
        pf = NFPROTO_IPV4;
    else if (IS_IPV6(skb) || IS_VLAN_IPV6(skb) || IS_PPPOE_IPV6(skb))
        pf = NFPROTO_IPV6;
    else
        return NF_ACCEPT;

    /* We assume any code from br_dev_queue_push_xmit onwards doesn't care
     * about the value of skb->pkt_type. */
    if (skb->pkt_type == PACKET_OTHERHOST) {
        skb->pkt_type = PACKET_HOST;
        nf_bridge->mask |= BRNF_PKT_TYPE;
    }

    nf_bridge_pull_encap_header(skb);
    nf_bridge_save_header(skb);
    if (pf == NFPROTO_IPV4)
        skb->protocol = htons(ETH_P_IP);
    else
        skb->protocol = htons(ETH_P_IPV6);

    NF_HOOK(pf, NF_INET_POST_ROUTING, skb, NULL, realoutdev,
        br_nf_dev_queue_xmit);

    return NF_STOLEN;
}

/* IP/SABOTAGE *****************************************************/
/* Don't hand locally destined packets to PF_INET(6)/PRE_ROUTING
 * for the second time. */
static unsigned int ip_sabotage_in(unsigned int hook, struct sk_buff *skb,
                   const struct net_device *in,
                   const struct net_device *out,
                   int (*okfn)(struct sk_buff *))
{
    if (skb->nf_bridge &&
        !(skb->nf_bridge->mask & BRNF_NF_BRIDGE_PREROUTING)) {
        return NF_STOP;
    }

    return NF_ACCEPT;
}

/* For br_nf_post_routing, we need (prio = NF_BR_PRI_LAST), because
 * br_dev_queue_push_xmit is called afterwards */
static struct nf_hook_ops br_nf_ops[] __read_mostly = {
    {
        .hook = br_nf_pre_routing,
        .owner = THIS_MODULE,
        .pf = NFPROTO_BRIDGE,
        .hooknum = NF_BR_PRE_ROUTING,
        .priority = NF_BR_PRI_BRNF,
    },
    {
        .hook = br_nf_local_in,
        .owner = THIS_MODULE,
        .pf = NFPROTO_BRIDGE,
        .hooknum = NF_BR_LOCAL_IN,
        .priority = NF_BR_PRI_BRNF,
    },
    {
        .hook = br_nf_forward_ip,
        .owner = THIS_MODULE,
        .pf = NFPROTO_BRIDGE,
        .hooknum = NF_BR_FORWARD,
        .priority = NF_BR_PRI_BRNF - 1,
    },
    {
        .hook = br_nf_forward_arp,
        .owner = THIS_MODULE,
        .pf = NFPROTO_BRIDGE,
        .hooknum = NF_BR_FORWARD,
        .priority = NF_BR_PRI_BRNF,
    },
    {
        .hook = br_nf_post_routing,
        .owner = THIS_MODULE,
        .pf = NFPROTO_BRIDGE,
        .hooknum = NF_BR_POST_ROUTING,
        .priority = NF_BR_PRI_LAST,
    },
    {
        .hook = ip_sabotage_in,
        .owner = THIS_MODULE,
        .pf = NFPROTO_IPV4,
        .hooknum = NF_INET_PRE_ROUTING,
        .priority = NF_IP_PRI_FIRST,
    },
    {
        .hook = ip_sabotage_in,
        .owner = THIS_MODULE,
        .pf = NFPROTO_IPV6,
        .hooknum = NF_INET_PRE_ROUTING,
        .priority = NF_IP6_PRI_FIRST,
    },
};

#ifdef CONFIG_SYSCTL
static
int brnf_sysctl_call_tables(ctl_table * ctl, int write,
                void __user * buffer, size_t * lenp, loff_t * ppos)
{
    int ret;

    ret = proc_dointvec(ctl, write, buffer, lenp, ppos);

    if (write && *(int *)(ctl->data))
        *(int *)(ctl->data) = 1;
    return ret;
}

static ctl_table brnf_table[] = {
    {
        .procname   = "bridge-nf-call-arptables",
        .data       = &brnf_call_arptables,
        .maxlen     = sizeof(int),
        .mode       = 0644,
        .proc_handler   = brnf_sysctl_call_tables,
    },
    {
        .procname   = "bridge-nf-call-iptables",
        .data       = &brnf_call_iptables,
        .maxlen     = sizeof(int),
        .mode       = 0644,
        .proc_handler   = brnf_sysctl_call_tables,
    },
    {
        .procname   = "bridge-nf-call-ip6tables",
        .data       = &brnf_call_ip6tables,
        .maxlen     = sizeof(int),
        .mode       = 0644,
        .proc_handler   = brnf_sysctl_call_tables,
    },
    {
        .procname   = "bridge-nf-filter-vlan-tagged",
        .data       = &brnf_filter_vlan_tagged,
        .maxlen     = sizeof(int),
        .mode       = 0644,
        .proc_handler   = brnf_sysctl_call_tables,
    },
    {
        .procname   = "bridge-nf-filter-pppoe-tagged",
        .data       = &brnf_filter_pppoe_tagged,
        .maxlen     = sizeof(int),
        .mode       = 0644,
        .proc_handler   = brnf_sysctl_call_tables,
    },
    {
        .procname   = "bridge-nf-pass-vlan-input-dev",
        .data       = &brnf_pass_vlan_indev,
        .maxlen     = sizeof(int),
        .mode       = 0644,
        .proc_handler   = brnf_sysctl_call_tables,
    },
    { }
};
#endif

int __init br_netfilter_init(void)
{
    int ret;

    ret = dst_entries_init(&fake_dst_ops);
    if (ret < 0)
        return ret;

    ret = nf_register_hooks(br_nf_ops, ARRAY_SIZE(br_nf_ops));
    if (ret < 0) {
        dst_entries_destroy(&fake_dst_ops);
        return ret;
    }
#ifdef CONFIG_SYSCTL
    brnf_sysctl_header = register_net_sysctl(&init_net, "net/bridge", brnf_table);
    if (brnf_sysctl_header == NULL) {
        printk(KERN_WARNING
               "br_netfilter: can't register to sysctl.\n");
        nf_unregister_hooks(br_nf_ops, ARRAY_SIZE(br_nf_ops));
        dst_entries_destroy(&fake_dst_ops);
        return -ENOMEM;
    }
#endif
    printk(KERN_NOTICE "Bridge firewalling registered\n");
    return 0;
}

void br_netfilter_fini(void)
{
    nf_unregister_hooks(br_nf_ops, ARRAY_SIZE(br_nf_ops));
#ifdef CONFIG_SYSCTL
    unregister_net_sysctl_table(brnf_sysctl_header);
#endif
    dst_entries_destroy(&fake_dst_ops);
}