br_forward.c

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/*
 *  Forwarding decision
 *  Linux ethernet bridge
 *
 *  Authors:
 *  Lennert Buytenhek       <[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.
 */

#include <linux/err.h>
#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/netdevice.h>
#include <linux/netpoll.h>
#include <linux/skbuff.h>
#include <linux/if_vlan.h>
#include <linux/netfilter_bridge.h>
#include "br_private.h"

static int deliver_clone(const struct net_bridge_port *prev,
             struct sk_buff *skb,
             void (*__packet_hook)(const struct net_bridge_port *p,
                           struct sk_buff *skb));

/* Don't forward packets to originating port or forwarding diasabled */
static inline int should_deliver(const struct net_bridge_port *p,
                 const struct sk_buff *skb)
{
    return (((p->flags & BR_HAIRPIN_MODE) || skb->dev != p->dev) &&
        p->state == BR_STATE_FORWARDING);
}

static inline unsigned int packet_length(const struct sk_buff *skb)
{
    return skb->len - (skb->protocol == htons(ETH_P_8021Q) ? VLAN_HLEN : 0);
}

int br_dev_queue_push_xmit(struct sk_buff *skb)
{
    /* ip_fragment doesn't copy the MAC header */
    if (nf_bridge_maybe_copy_header(skb) ||
        (packet_length(skb) > skb->dev->mtu && !skb_is_gso(skb))) {
        kfree_skb(skb);
    } else {
        skb_push(skb, ETH_HLEN);
        br_drop_fake_rtable(skb);
        dev_queue_xmit(skb);
    }

    return 0;
}

int br_forward_finish(struct sk_buff *skb)
{
    return NF_HOOK(NFPROTO_BRIDGE, NF_BR_POST_ROUTING, skb, NULL, skb->dev,
               br_dev_queue_push_xmit);

}

static void __br_deliver(const struct net_bridge_port *to, struct sk_buff *skb)
{
    skb->dev = to->dev;

    if (unlikely(netpoll_tx_running(to->br->dev))) {
        if (packet_length(skb) > skb->dev->mtu && !skb_is_gso(skb))
            kfree_skb(skb);
        else {
            skb_push(skb, ETH_HLEN);
            br_netpoll_send_skb(to, skb);
        }
        return;
    }

    NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_OUT, skb, NULL, skb->dev,
        br_forward_finish);
}

static void __br_forward(const struct net_bridge_port *to, struct sk_buff *skb)
{
    struct net_device *indev;

    if (skb_warn_if_lro(skb)) {
        kfree_skb(skb);
        return;
    }

    indev = skb->dev;
    skb->dev = to->dev;
    skb_forward_csum(skb);

    NF_HOOK(NFPROTO_BRIDGE, NF_BR_FORWARD, skb, indev, skb->dev,
        br_forward_finish);
}

/* called with rcu_read_lock */
void br_deliver(const struct net_bridge_port *to, struct sk_buff *skb)
{
    if (to && should_deliver(to, skb)) {
        __br_deliver(to, skb);
        return;
    }

    kfree_skb(skb);
}

/* called with rcu_read_lock */
void br_forward(const struct net_bridge_port *to, struct sk_buff *skb, struct sk_buff *skb0)
{
    if (should_deliver(to, skb)) {
        if (skb0)
            deliver_clone(to, skb, __br_forward);
        else
            __br_forward(to, skb);
        return;
    }

    if (!skb0)
        kfree_skb(skb);
}

static int deliver_clone(const struct net_bridge_port *prev,
             struct sk_buff *skb,
             void (*__packet_hook)(const struct net_bridge_port *p,
                           struct sk_buff *skb))
{
    struct net_device *dev = BR_INPUT_SKB_CB(skb)->brdev;

    skb = skb_clone(skb, GFP_ATOMIC);
    if (!skb) {
        dev->stats.tx_dropped++;
        return -ENOMEM;
    }

    __packet_hook(prev, skb);
    return 0;
}

static struct net_bridge_port *maybe_deliver(
    struct net_bridge_port *prev, struct net_bridge_port *p,
    struct sk_buff *skb,
    void (*__packet_hook)(const struct net_bridge_port *p,
                  struct sk_buff *skb))
{
    int err;

    if (!should_deliver(p, skb))
        return prev;

    if (!prev)
        goto out;

    err = deliver_clone(prev, skb, __packet_hook);
    if (err)
        return ERR_PTR(err);

out:
    return p;
}

/* called under bridge lock */
static void br_flood(struct net_bridge *br, struct sk_buff *skb,
             struct sk_buff *skb0,
             void (*__packet_hook)(const struct net_bridge_port *p,
                       struct sk_buff *skb))
{
    struct net_bridge_port *p;
    struct net_bridge_port *prev;

    prev = NULL;

    list_for_each_entry_rcu(p, &br->port_list, list) {
        prev = maybe_deliver(prev, p, skb, __packet_hook);
        if (IS_ERR(prev))
            goto out;
    }

    if (!prev)
        goto out;

    if (skb0)
        deliver_clone(prev, skb, __packet_hook);
    else
        __packet_hook(prev, skb);
    return;

out:
    if (!skb0)
        kfree_skb(skb);
}


/* called with rcu_read_lock */
void br_flood_deliver(struct net_bridge *br, struct sk_buff *skb)
{
    br_flood(br, skb, NULL, __br_deliver);
}

/* called under bridge lock */
void br_flood_forward(struct net_bridge *br, struct sk_buff *skb,
              struct sk_buff *skb2)
{
    br_flood(br, skb, skb2, __br_forward);
}

#ifdef CONFIG_BRIDGE_IGMP_SNOOPING
/* called with rcu_read_lock */
static void br_multicast_flood(struct net_bridge_mdb_entry *mdst,
                   struct sk_buff *skb, struct sk_buff *skb0,
                   void (*__packet_hook)(
                    const struct net_bridge_port *p,
                    struct sk_buff *skb))
{
    struct net_device *dev = BR_INPUT_SKB_CB(skb)->brdev;
    struct net_bridge *br = netdev_priv(dev);
    struct net_bridge_port *prev = NULL;
    struct net_bridge_port_group *p;
    struct hlist_node *rp;

    rp = rcu_dereference(hlist_first_rcu(&br->router_list));
    p = mdst ? rcu_dereference(mdst->ports) : NULL;
    while (p || rp) {
        struct net_bridge_port *port, *lport, *rport;

        lport = p ? p->port : NULL;
        rport = rp ? hlist_entry(rp, struct net_bridge_port, rlist) :
                 NULL;

        port = (unsigned long)lport > (unsigned long)rport ?
               lport : rport;

        prev = maybe_deliver(prev, port, skb, __packet_hook);
        if (IS_ERR(prev))
            goto out;

        if ((unsigned long)lport >= (unsigned long)port)
            p = rcu_dereference(p->next);
        if ((unsigned long)rport >= (unsigned long)port)
            rp = rcu_dereference(hlist_next_rcu(rp));
    }

    if (!prev)
        goto out;

    if (skb0)
        deliver_clone(prev, skb, __packet_hook);
    else
        __packet_hook(prev, skb);
    return;

out:
    if (!skb0)
        kfree_skb(skb);
}

/* called with rcu_read_lock */
void br_multicast_deliver(struct net_bridge_mdb_entry *mdst,
              struct sk_buff *skb)
{
    br_multicast_flood(mdst, skb, NULL, __br_deliver);
}

/* called with rcu_read_lock */
void br_multicast_forward(struct net_bridge_mdb_entry *mdst,
              struct sk_buff *skb, struct sk_buff *skb2)
{
    br_multicast_flood(mdst, skb, skb2, __br_forward);
}
#endif