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    Subject[patch v1, kernel version 3.2.1] net/ipv4/ip_gre: Ethernet multipoint GRE over IP
    From: Stefan Gula <steweg@gmail.com

    This patch is an extension for current Ethernet over GRE
    implementation, which allows user to create virtual bridge (multipoint
    VPN) and forward traffic based on Ethernet MAC address informations in
    it. It simulates the Bridge bahaviour learing mechanism, but instead
    of learning port ID from which given MAC address comes, it learns IP
    address of peer which encapsulated given packet. Multicast, Broadcast
    and unknown-multicast traffic is send over network as multicast
    enacapsulated GRE packet, so one Ethernet multipoint GRE tunnel can be
    represented as one single virtual switch on logical level and be also
    represented as one multicast IPv4 address on network level.

    Signed-off-by: Stefan Gula <steweg@gmail.com>

    ---

    Patch was tested for more than one year in real network infrastructure
    consisting of 98 Linux based access-points

    diff -uprN -X linux-3.2.1-orig/Documentation/dontdiff
    linux-3.2.1-orig/Documentation/dontdiff
    linux-3.2.1-my/Documentation/dontdiff
    --- linux-3.2.1-orig/Documentation/dontdiff 2012-01-16 12:32:18.000000000 +0100
    +++ linux-3.2.1-my/Documentation/dontdiff 2012-01-12 20:42:45.000000000 +0100
    @@ -260,5 +260,3 @@ wakeup.lds
    zImage*
    zconf.hash.c
    zoffset.h
    -mkpiggy
    -mdp
    diff -uprN -X linux-3.2.1-orig/Documentation/dontdiff
    linux-3.2.1-orig/include/net/ipip.h linux-3.2.1-my/include/net/ipip.h
    --- linux-3.2.1-orig/include/net/ipip.h 2012-01-12 20:42:45.000000000 +0100
    +++ linux-3.2.1-my/include/net/ipip.h 2012-01-16 11:17:01.000000000 +0100
    @@ -27,6 +27,14 @@ struct ip_tunnel {
    __u32 o_seqno; /* The last output seqno */
    int hlen; /* Precalculated GRE header length */
    int mlink;
    +#ifdef CONFIG_NET_IPGRE_BRIDGE
    +#define GRETAP_BR_HASH_BITS 8
    +#define GRETAP_BR_HASH_SIZE (1 << GRETAP_BR_HASH_BITS)
    + struct hlist_head hash[GRETAP_BR_HASH_SIZE];
    + spinlock_t hash_lock;
    + unsigned long ageing_time;
    + struct timer_list gc_timer;
    +#endif

    struct ip_tunnel_parm parms;

    diff -uprN -X linux-3.2.1-orig/Documentation/dontdiff
    linux-3.2.1-orig/net/ipv4/Kconfig linux-3.2.1-my/net/ipv4/Kconfig
    --- linux-3.2.1-orig/net/ipv4/Kconfig 2012-01-12 20:42:45.000000000 +0100
    +++ linux-3.2.1-my/net/ipv4/Kconfig 2012-01-16 12:37:00.000000000 +0100
    @@ -211,6 +211,15 @@ config NET_IPGRE_BROADCAST
    Network), but can be distributed all over the Internet. If you want
    to do that, say Y here and to "IP multicast routing" below.

    +config NET_IPGRE_BRIDGE
    + bool "IP: Ethernet over multipoint GRE over IP"
    + depends on IP_MULTICAST && NET_IPGRE && NET_IPGRE_BROADCAST
    + help
    + Allows you to use multipoint GRE VPN as virtual switch and interconnect
    + several L2 endpoints over L3 routed infrastructure. It is useful for
    + creating multipoint L2 VPNs which can be later used inside bridge
    + interfaces If you want to use. GRE multipoint L2 VPN feature say Y.
    +
    config IP_MROUTE
    bool "IP: multicast routing"
    depends on IP_MULTICAST
    diff -uprN -X linux-3.2.1-orig/Documentation/dontdiff
    linux-3.2.1-orig/net/ipv4/ip_gre.c linux-3.2.1-my/net/ipv4/ip_gre.c
    --- linux-3.2.1-orig/net/ipv4/ip_gre.c 2012-01-12 20:42:45.000000000 +0100
    +++ linux-3.2.1-my/net/ipv4/ip_gre.c 2012-01-16 12:29:03.000000000 +0100
    @@ -52,6 +52,11 @@
    #include <net/ip6_route.h>
    #endif

    +#ifdef CONFIG_NET_IPGRE_BRIDGE
    +#include <linux/jhash.h>
    +#include <asm/unaligned.h>
    +#endif
    +
    /*
    Problems & solutions
    --------------------
    @@ -134,6 +139,199 @@ struct ipgre_net {
    struct net_device *fb_tunnel_dev;
    };

    +#ifdef CONFIG_NET_IPGRE_BRIDGE
    + /*
    + * This part of code includes codes to enable L2 ethernet
    + * switch virtualization over IP routed infrastructure with
    + * utilization of multicast capable endpoint using Ethernet
    + * over GRE
    + *
    + * Author: Stefan Gula
    + * Signed-off-by: Stefan Gula <steweg@gmail.com>
    + */
    +struct mac_addr {
    + unsigned char addr[6];
    +};
    +
    +struct ipgre_tap_bridge_entry {
    + struct hlist_node hlist;
    + u32 raddr;
    + struct mac_addr addr;
    + struct net_device *dev;
    + struct rcu_head rcu;
    + atomic_t use_count;
    + unsigned long ageing_timer;
    +};
    +
    +static struct kmem_cache *ipgre_tap_bridge_cache __read_mostly;
    +static u32 ipgre_salt __read_mostly;
    +
    +static inline int ipgre_tap_bridge_hash(const unsigned char *mac)
    +{
    + u32 key = get_unaligned((u32 *)(mac + 2));
    + return jhash_1word(key, ipgre_salt) & (GRETAP_BR_HASH_SIZE - 1);
    +}
    +
    +static inline int ipgre_tap_bridge_has_expired(const struct ip_tunnel *tunnel,
    + const struct ipgre_tap_bridge_entry *entry)
    +{
    + return time_before_eq(entry->ageing_timer + tunnel->ageing_time,
    + jiffies);
    +}
    +
    +static void ipgre_tap_bridge_rcu_free(struct rcu_head *head)
    +{
    + struct ipgre_tap_bridge_entry *entry
    + = container_of(head, struct ipgre_tap_bridge_entry, rcu);
    + kmem_cache_free(ipgre_tap_bridge_cache, entry);
    +}
    +
    +void ipgre_tap_bridge_put(struct ipgre_tap_bridge_entry *entry)
    +{
    + if (atomic_dec_and_test(&entry->use_count))
    + call_rcu(&entry->rcu, ipgre_tap_bridge_rcu_free);
    +}
    +
    +static inline void ipgre_tap_bridge_delete(struct
    ipgre_tap_bridge_entry *entry)
    +{
    + hlist_del_rcu(&entry->hlist);
    + ipgre_tap_bridge_put(entry);
    +}
    +
    +static struct ipgre_tap_bridge_entry *ipgre_tap_bridge_create(
    + struct hlist_head *head,
    + u32 source,
    + const unsigned char *addr, struct net_device *dev)
    +{
    + struct ipgre_tap_bridge_entry *entry;
    + entry = kmem_cache_alloc(ipgre_tap_bridge_cache, GFP_ATOMIC);
    + if (entry) {
    + memcpy(entry->addr.addr, addr, ETH_ALEN);
    + atomic_set(&entry->use_count, 1);
    + hlist_add_head_rcu(&entry->hlist, head);
    + entry->raddr = source;
    + entry->ageing_timer = jiffies;
    + entry->dev = dev;
    + }
    + return entry;
    +}
    +
    +struct ipgre_tap_bridge_entry *__ipgre_tap_bridge_get(struct ip_tunnel *tunnel,
    + const unsigned char *addr)
    +{
    + struct hlist_node *h;
    + struct ipgre_tap_bridge_entry *entry;
    + hlist_for_each_entry_rcu(entry, h,
    + &tunnel->hash[ipgre_tap_bridge_hash(addr)], hlist)
    + {
    + if (!compare_ether_addr(entry->addr.addr, addr)) {
    + if (unlikely(ipgre_tap_bridge_has_expired(tunnel,
    + entry)))
    + break;
    + return entry;
    + }
    + }
    +
    + return NULL;
    +}
    +
    +struct ipgre_tap_bridge_entry *ipgre_tap_bridge_get(struct ip_tunnel *tunnel,
    + const unsigned char *addr)
    +{
    + struct ipgre_tap_bridge_entry *entry;
    + rcu_read_lock();
    + entry = __ipgre_tap_bridge_get(tunnel, addr);
    + if (entry && !atomic_inc_not_zero(&entry->use_count))
    + entry = NULL;
    + rcu_read_unlock();
    + return entry;
    +}
    +
    +__be32 ipgre_tap_bridge_get_raddr(struct ip_tunnel *tunnel,
    + const unsigned char *addr)
    +{
    + struct ipgre_tap_bridge_entry *entry;
    + entry = ipgre_tap_bridge_get(tunnel, addr);
    + if (entry == NULL)
    + return 0;
    + else
    + return entry->raddr;
    +}
    +
    +
    +static inline struct ipgre_tap_bridge_entry *ipgre_tap_bridge_find(
    + struct hlist_head *head,
    + const unsigned char *addr)
    +{
    + struct hlist_node *h;
    + struct ipgre_tap_bridge_entry *entry;
    + hlist_for_each_entry_rcu(entry, h, head, hlist) {
    + if (!compare_ether_addr(entry->addr.addr, addr))
    + return entry;
    + }
    + return NULL;
    +}
    +
    +int ipgre_tap_bridge_init(void)
    +{
    + ipgre_tap_bridge_cache = kmem_cache_create("ipgre_tap_bridge_cache",
    + sizeof(struct ipgre_tap_bridge_entry),
    + 0,
    + SLAB_HWCACHE_ALIGN, NULL);
    + if (!ipgre_tap_bridge_cache)
    + return -ENOMEM;
    + get_random_bytes(&ipgre_salt, sizeof(ipgre_salt));
    + return 0;
    +}
    +
    +void ipgre_tap_bridge_fini(void)
    +{
    + kmem_cache_destroy(ipgre_tap_bridge_cache);
    +}
    +
    +void ipgre_tap_bridge_cleanup(unsigned long _data)
    +{
    + struct ip_tunnel *tunnel = (struct ip_tunnel *)_data;
    + unsigned long delay = tunnel->ageing_time;
    + unsigned long next_timer = jiffies + tunnel->ageing_time;
    + int i;
    + spin_lock_bh(&tunnel->hash_lock);
    + for (i = 0; i < GRETAP_BR_HASH_SIZE; i++) {
    + struct ipgre_tap_bridge_entry *entry;
    + struct hlist_node *h, *n;
    + hlist_for_each_entry_safe(entry, h, n,
    + &tunnel->hash[i], hlist)
    + {
    + unsigned long this_timer;
    + this_timer = entry->ageing_timer + delay;
    + if (time_before_eq(this_timer, jiffies))
    + ipgre_tap_bridge_delete(entry);
    + else if (time_before(this_timer, next_timer))
    + next_timer = this_timer;
    + }
    + }
    + spin_unlock_bh(&tunnel->hash_lock);
    + mod_timer(&tunnel->gc_timer, round_jiffies(next_timer + HZ/4));
    +}
    +
    +void ipgre_tap_bridge_flush(struct ip_tunnel *tunnel)
    +{
    + int i;
    + spin_lock_bh(&tunnel->hash_lock);
    + for (i = 0; i < GRETAP_BR_HASH_SIZE; i++) {
    + struct ipgre_tap_bridge_entry *entry;
    + struct hlist_node *h, *n;
    + hlist_for_each_entry_safe(entry, h, n,
    + &tunnel->hash[i], hlist)
    + {
    + ipgre_tap_bridge_delete(entry);
    + }
    + }
    + spin_unlock_bh(&tunnel->hash_lock);
    +}
    +
    +#endif
    +
    /* Tunnel hash table */

    /*
    @@ -563,6 +761,13 @@ static int ipgre_rcv(struct sk_buff *skb
    int offset = 4;
    __be16 gre_proto;

    +#ifdef CONFIG_NET_IPGRE_BRIDGE
    + u32 orig_source;
    + struct hlist_head *head;
    + struct ipgre_tap_bridge_entry *entry;
    + struct ethhdr *tethhdr;
    +#endif
    +
    if (!pskb_may_pull(skb, 16))
    goto drop_nolock;

    @@ -659,10 +864,38 @@ static int ipgre_rcv(struct sk_buff *skb
    tunnel->dev->stats.rx_errors++;
    goto drop;
    }
    -
    +#ifdef CONFIG_NET_IPGRE_BRIDGE
    + orig_source = iph->saddr;
    +#endif
    iph = ip_hdr(skb);
    skb->protocol = eth_type_trans(skb, tunnel->dev);
    skb_postpull_rcsum(skb, eth_hdr(skb), ETH_HLEN);
    +#ifdef CONFIG_NET_IPGRE_BRIDGE
    + if (ipv4_is_multicast(tunnel->parms.iph.daddr)) {
    + tethhdr = eth_hdr(skb);
    + if ((tethhdr->h_source[0]&1) == 0) {
    + head = &tunnel->hash[
    + ipgre_tap_bridge_hash(
    + tethhdr->h_source)];
    + entry = ipgre_tap_bridge_find(head,
    + tethhdr->h_source);
    + if (likely(entry)) {
    + entry->raddr = orig_source;
    + entry->ageing_timer = jiffies;
    + } else {
    + spin_lock(&tunnel->hash_lock);
    + if (!ipgre_tap_bridge_find(head,
    + tethhdr->h_source))
    + ipgre_tap_bridge_create(
    + head,
    + orig_source,
    + tethhdr->h_source,
    + tunnel->dev);
    + spin_unlock(&tunnel->hash_lock);
    + }
    + }
    + }
    +#endif
    }

    tstats = this_cpu_ptr(tunnel->dev->tstats);
    @@ -716,7 +949,17 @@ static netdev_tx_t ipgre_tunnel_xmit(str
    tiph = &tunnel->parms.iph;
    }

    +#ifdef CONFIG_NET_IPGRE_BRIDGE
    + if ((dev->type == ARPHRD_ETHER) && ipv4_is_multicast(
    + tunnel->parms.iph.daddr))
    + dst = ipgre_tap_bridge_get_raddr(tunnel,
    + ((struct ethhdr *)skb->data)->h_dest);
    + if (dst == 0)
    + dst = tiph->daddr;
    + if (dst == 0) {
    +#else
    if ((dst = tiph->daddr) == 0) {
    +#endif
    /* NBMA tunnel */

    if (skb_dst(skb) == NULL) {
    @@ -1209,6 +1452,16 @@ static int ipgre_open(struct net_device
    return -EADDRNOTAVAIL;
    t->mlink = dev->ifindex;
    ip_mc_inc_group(__in_dev_get_rtnl(dev), t->parms.iph.daddr);
    +#ifdef CONFIG_NET_IPGRE_BRIDGE
    + if (t->dev->type == ARPHRD_ETHER) {
    + INIT_HLIST_HEAD(t->hash);
    + spin_lock_init(&t->hash_lock);
    + t->ageing_time = 300 * HZ;
    + setup_timer(&t->gc_timer, ipgre_tap_bridge_cleanup,
    + (unsigned long) t);
    + mod_timer(&t->gc_timer, jiffies + t->ageing_time);
    + }
    +#endif
    }
    return 0;
    }
    @@ -1219,6 +1472,12 @@ static int ipgre_close(struct net_device

    if (ipv4_is_multicast(t->parms.iph.daddr) && t->mlink) {
    struct in_device *in_dev;
    +#ifdef CONFIG_NET_IPGRE_BRIDGE
    + if (t->dev->type == ARPHRD_ETHER) {
    + ipgre_tap_bridge_flush(t);
    + del_timer_sync(&t->gc_timer);
    + }
    +#endif
    in_dev = inetdev_by_index(dev_net(dev), t->mlink);
    if (in_dev)
    ip_mc_dec_group(in_dev, t->parms.iph.daddr);
    @@ -1341,6 +1600,12 @@ static int __net_init ipgre_init_net(str
    struct ipgre_net *ign = net_generic(net, ipgre_net_id);
    int err;

    +#ifdef CONFIG_NET_IPGRE_BRIDGE
    + err = ipgre_tap_bridge_init();
    + if (err)
    + goto err_out;
    +#endif
    +
    ign->fb_tunnel_dev = alloc_netdev(sizeof(struct ip_tunnel), "gre0",
    ipgre_tunnel_setup);
    if (!ign->fb_tunnel_dev) {
    @@ -1362,6 +1627,10 @@ static int __net_init ipgre_init_net(str
    err_reg_dev:
    ipgre_dev_free(ign->fb_tunnel_dev);
    err_alloc_dev:
    +#ifdef CONFIG_NET_IPGRE_BRIDGE
    + ipgre_tap_bridge_fini();
    +err_out:
    +#endif
    return err;
    }

    @@ -1375,6 +1644,9 @@ static void __net_exit ipgre_exit_net(st
    ipgre_destroy_tunnels(ign, &list);
    unregister_netdevice_many(&list);
    rtnl_unlock();
    +#ifdef CONFIG_NET_IPGRE_BRIDGE
    + ipgre_tap_bridge_fini();
    +#endif
    }

    static struct pernet_operations ipgre_net_ops = {
    --
    Stefan Gula
    CCNP, CCIP


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