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Subject[patch v5, 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 information in
it. It simulates the Bridge behavior learning 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
encapsulated 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>

---

V5 changes: created ipgre_tap_bridge_rcv function to make code somehow more readable



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 2012-01-25 10:30:32.000000000 +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 +139,202 @@ 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 ipgre_tap_bridge_entry {
+ struct hlist_node hlist;
+ __be32 raddr;
+ unsigned char addr[ETH_ALEN];
+ unsigned long updated;
+ struct rcu_head rcu;
+};
+
+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->updated + tunnel->ageing_time,
+ jiffies);
+}
+
+static inline void ipgre_tap_bridge_delete(struct ipgre_tap_bridge_entry *entry)
+{
+ hlist_del_rcu(&entry->hlist);
+ kfree_rcu(entry, rcu);
+}
+
+static 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(&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->updated + 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(&tunnel->hash_lock);
+ mod_timer(&tunnel->gc_timer, round_jiffies_up(next_timer));
+}
+
+static 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);
+}
+
+static 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)) {
+ if (unlikely(ipgre_tap_bridge_has_expired(tunnel,
+ entry)))
+ break;
+ return entry;
+ }
+ }
+
+ return NULL;
+}
+
+static 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(entry, h, head, hlist) {
+ if (!compare_ether_addr(entry->addr, addr))
+ return entry;
+ }
+ return NULL;
+}
+
+
+static struct ipgre_tap_bridge_entry *ipgre_tap_bridge_find_rcu(
+ 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))
+ return entry;
+ }
+ return NULL;
+}
+
+static struct ipgre_tap_bridge_entry *ipgre_tap_bridge_create(
+ struct hlist_head *head,
+ __be32 source,
+ const unsigned char *addr)
+{
+ struct ipgre_tap_bridge_entry *entry;
+
+ entry = kmalloc(sizeof(*entry), GFP_ATOMIC);
+ if (entry) {
+ memcpy(entry->addr, addr, ETH_ALEN);
+ entry->raddr = source;
+ entry->updated = jiffies;
+ hlist_add_head_rcu(&entry->hlist, head);
+ }
+ return entry;
+}
+
+static __be32 ipgre_tap_bridge_get_raddr(struct ip_tunnel *tunnel,
+ const unsigned char *addr)
+{
+ __be32 raddr = 0;
+ struct ipgre_tap_bridge_entry *entry;
+
+ rcu_read_lock();
+ entry = __ipgre_tap_bridge_get(tunnel, addr);
+ if (entry)
+ raddr = entry->raddr;
+ rcu_read_unlock();
+
+ return raddr;
+}
+
+static void ipgre_tap_bridge_rcv(struct ip_tunnel *tunnel,struct sk_buff *skb,
+ __be32 orig_source)
+{
+ const struct ethhdr *tethhdr;
+ struct hlist_head *head;
+ struct ipgre_tap_bridge_entry *entry;
+
+ if (ipv4_is_multicast(tunnel->parms.iph.daddr)) {
+ tethhdr = eth_hdr(skb);
+ if (!is_multicast_ether_addr(
+ tethhdr->h_source)) {
+ head = &tunnel->hash[
+ ipgre_tap_bridge_hash(tethhdr->h_source)];
+ entry = ipgre_tap_bridge_find_rcu(head,
+ tethhdr->h_source);
+ if (likely(entry)) {
+ entry->raddr = orig_source;
+ entry->updated = 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);
+ spin_unlock(&tunnel->hash_lock);
+ }
+ }
+ }
+}
+#endif
/* Tunnel hash table */

/*
@@ -562,6 +763,9 @@ static int ipgre_rcv(struct sk_buff *skb
struct ip_tunnel *tunnel;
int offset = 4;
__be16 gre_proto;
+#ifdef CONFIG_NET_IPGRE_BRIDGE
+ __be32 orig_source;
+#endif

if (!pskb_may_pull(skb, 16))
goto drop_nolock;
@@ -654,6 +858,9 @@ static int ipgre_rcv(struct sk_buff *skb

/* Warning: All skb pointers will be invalidated! */
if (tunnel->dev->type == ARPHRD_ETHER) {
+#ifdef CONFIG_NET_IPGRE_BRIDGE
+ orig_source = iph->saddr;
+#endif
if (!pskb_may_pull(skb, ETH_HLEN)) {
tunnel->dev->stats.rx_length_errors++;
tunnel->dev->stats.rx_errors++;
@@ -663,6 +870,9 @@ static int ipgre_rcv(struct sk_buff *skb
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
+ ipgre_tap_bridge_rcv(tunnel, skb, orig_source);
+#endif
}

tstats = this_cpu_ptr(tunnel->dev->tstats);
@@ -702,7 +912,7 @@ static netdev_tx_t ipgre_tunnel_xmit(str
struct iphdr *iph; /* Our new IP header */
unsigned int max_headroom; /* The extra header space needed */
int gre_hlen;
- __be32 dst;
+ __be32 dst = 0;
int mtu;

if (dev->type == ARPHRD_ETHER)
@@ -716,7 +926,15 @@ static netdev_tx_t ipgre_tunnel_xmit(str
tiph = &tunnel->parms.iph;
}

- if ((dst = tiph->daddr) == 0) {
+#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);
+#endif
+ if (dst == 0)
+ dst = tiph->daddr;
+ if (dst == 0) {
/* NBMA tunnel */

if (skb_dst(skb) == NULL) {
@@ -1209,6 +1427,16 @@ 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 +1447,12 @@ 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);
@@ -1488,6 +1722,10 @@ static int ipgre_tap_init(struct net_dev
static const struct net_device_ops ipgre_tap_netdev_ops = {
.ndo_init = ipgre_tap_init,
.ndo_uninit = ipgre_tunnel_uninit,
+#ifdef CONFIG_NET_IPGRE_BRIDGE
+ .ndo_open = ipgre_open,
+ .ndo_stop = ipgre_close,
+#endif
.ndo_start_xmit = ipgre_tunnel_xmit,
.ndo_set_mac_address = eth_mac_addr,
.ndo_validate_addr = eth_validate_addr,
@@ -1705,6 +1943,9 @@ static int __init ipgre_init(void)

printk(KERN_INFO "GRE over IPv4 tunneling driver\n");

+#ifdef CONFIG_NET_IPGRE_BRIDGE
+ get_random_bytes(&ipgre_salt, sizeof(ipgre_salt));
+#endif
err = register_pernet_device(&ipgre_net_ops);
if (err < 0)
return err;

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