4 files changed, 166 insertions, 7 deletions

diff --git a/net/ipv4/Kconfig b/net/ipv4/Kconfig
index 7c3a7d191249..7458bdae7e9f 100644
--- a/net/ipv4/Kconfig
+++ b/net/ipv4/Kconfig
@@ -215,8 +215,15 @@ config NET_IPIP
           be inserted in and removed from the running kernel whenever you
           want). Most people won't need this and can say N.
 
+config NET_IPGRE_DEMUX
+        tristate "IP: GRE demultiplexer"
+        help
+         This is helper module to demultiplex GRE packets on GRE version field criteria.
+         Required by ip_gre and pptp modules.
+
 config NET_IPGRE
         tristate "IP: GRE tunnels over IP"
+        depends on NET_IPGRE_DEMUX
         help
           Tunneling means encapsulating data of one protocol type within
           another protocol and sending it over a channel that understands the
diff --git a/net/ipv4/Makefile b/net/ipv4/Makefile
index 80ff87ce43aa..4978d22f9a75 100644
--- a/net/ipv4/Makefile
+++ b/net/ipv4/Makefile
@@ -20,6 +20,7 @@ obj-$(CONFIG_PROC_FS) += proc.o
 obj-$(CONFIG_IP_MULTIPLE_TABLES) += fib_rules.o
 obj-$(CONFIG_IP_MROUTE) += ipmr.o
 obj-$(CONFIG_NET_IPIP) += ipip.o
+obj-$(CONFIG_NET_IPGRE_DEMUX) += gre.o
 obj-$(CONFIG_NET_IPGRE) += ip_gre.o
 obj-$(CONFIG_SYN_COOKIES) += syncookies.o
 obj-$(CONFIG_INET_AH) += ah4.o
diff --git a/net/ipv4/gre.c b/net/ipv4/gre.c
new file mode 100644
index 000000000000..b546736da2e1
--- /dev/null
+++ b/net/ipv4/gre.c
@@ -0,0 +1,151 @@
+/*
+ *      GRE over IPv4 demultiplexer driver
+ *
+ *      Authors: Dmitry Kozlov (xeb@mail.ru)
+ *
+ *      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/module.h>
+#include <linux/kernel.h>
+#include <linux/kmod.h>
+#include <linux/skbuff.h>
+#include <linux/in.h>
+#include <linux/netdevice.h>
+#include <linux/version.h>
+#include <linux/spinlock.h>
+#include <net/protocol.h>
+#include <net/gre.h>
+
+
+const struct gre_protocol *gre_proto[GREPROTO_MAX] __read_mostly;
+static DEFINE_SPINLOCK(gre_proto_lock);
+
+int gre_add_protocol(const struct gre_protocol *proto, u8 version)
+{
+        if (version >= GREPROTO_MAX)
+                goto err_out;
+
+        spin_lock(&gre_proto_lock);
+        if (gre_proto[version])
+                goto err_out_unlock;
+
+        rcu_assign_pointer(gre_proto[version], proto);
+        spin_unlock(&gre_proto_lock);
+        return 0;
+
+err_out_unlock:
+        spin_unlock(&gre_proto_lock);
+err_out:
+        return -1;
+}
+EXPORT_SYMBOL_GPL(gre_add_protocol);
+
+int gre_del_protocol(const struct gre_protocol *proto, u8 version)
+{
+        if (version >= GREPROTO_MAX)
+                goto err_out;
+
+        spin_lock(&gre_proto_lock);
+        if (gre_proto[version] != proto)
+                goto err_out_unlock;
+        rcu_assign_pointer(gre_proto[version], NULL);
+        spin_unlock(&gre_proto_lock);
+        synchronize_rcu();
+        return 0;
+
+err_out_unlock:
+        spin_unlock(&gre_proto_lock);
+err_out:
+        return -1;
+}
+EXPORT_SYMBOL_GPL(gre_del_protocol);
+
+static int gre_rcv(struct sk_buff *skb)
+{
+        const struct gre_protocol *proto;
+        u8 ver;
+        int ret;
+
+        if (!pskb_may_pull(skb, 12))
+                goto drop;
+
+        ver = skb->data[1]&0x7f;
+        if (ver >= GREPROTO_MAX)
+                goto drop;
+
+        rcu_read_lock();
+        proto = rcu_dereference(gre_proto[ver]);
+        if (!proto || !proto->handler)
+                goto drop_unlock;
+        ret = proto->handler(skb);
+        rcu_read_unlock();
+        return ret;
+
+drop_unlock:
+        rcu_read_unlock();
+drop:
+        kfree_skb(skb);
+        return NET_RX_DROP;
+}
+
+static void gre_err(struct sk_buff *skb, u32 info)
+{
+        const struct gre_protocol *proto;
+        u8 ver;
+
+        if (!pskb_may_pull(skb, 12))
+                goto drop;
+
+        ver = skb->data[1]&0x7f;
+        if (ver >= GREPROTO_MAX)
+                goto drop;
+
+        rcu_read_lock();
+        proto = rcu_dereference(gre_proto[ver]);
+        if (!proto || !proto->err_handler)
+                goto drop_unlock;
+        proto->err_handler(skb, info);
+        rcu_read_unlock();
+        return;
+
+drop_unlock:
+        rcu_read_unlock();
+drop:
+        kfree_skb(skb);
+}
+
+static const struct net_protocol net_gre_protocol = {
+        .handler     = gre_rcv,
+        .err_handler = gre_err,
+        .netns_ok    = 1,
+};
+
+static int __init gre_init(void)
+{
+        pr_info("GRE over IPv4 demultiplexor driver");
+
+        if (inet_add_protocol(&net_gre_protocol, IPPROTO_GRE) < 0) {
+                pr_err("gre: can't add protocol\n");
+                return -EAGAIN;
+        }
+
+        return 0;
+}
+
+static void __exit gre_exit(void)
+{
+        inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
+}
+
+module_init(gre_init);
+module_exit(gre_exit);
+
+MODULE_DESCRIPTION("GRE over IPv4 demultiplexer driver");
+MODULE_AUTHOR("D. Kozlov (xeb@mail.ru)");
+MODULE_LICENSE("GPL");
+
diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index 945b20a5ad50..85176895495a 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -44,6 +44,7 @@
 #include <net/net_namespace.h>
 #include <net/netns/generic.h>
 #include <net/rtnetlink.h>
+#include <net/gre.h>
 
 #ifdef CONFIG_IPV6
 #include <net/ipv6.h>
@@ -1278,10 +1279,9 @@ static void ipgre_fb_tunnel_init(struct net_device *dev)
 }
 
 
-static const struct net_protocol ipgre_protocol = {
-        .handler        =       ipgre_rcv,
-        .err_handler    =       ipgre_err,
-        .netns_ok       =       1,
+static const struct gre_protocol ipgre_protocol = {
+        .handler     = ipgre_rcv,
+        .err_handler = ipgre_err,
 };
 
 static void ipgre_destroy_tunnels(struct ipgre_net *ign, struct list_head *head)
@@ -1663,7 +1663,7 @@ static int __init ipgre_init(void)
         if (err < 0)
                 return err;
 
-        err = inet_add_protocol(&ipgre_protocol, IPPROTO_GRE);
+        err = gre_add_protocol(&ipgre_protocol, GREPROTO_CISCO);
         if (err < 0) {
                 printk(KERN_INFO "ipgre init: can't add protocol\n");
                 goto add_proto_failed;
@@ -1683,7 +1683,7 @@ out:
 tap_ops_failed:
         rtnl_link_unregister(&ipgre_link_ops);
 rtnl_link_failed:
-        inet_del_protocol(&ipgre_protocol, IPPROTO_GRE);
+        gre_del_protocol(&ipgre_protocol, GREPROTO_CISCO);
 add_proto_failed:
         unregister_pernet_device(&ipgre_net_ops);
         goto out;
@@ -1693,7 +1693,7 @@ static void __exit ipgre_fini(void)
 {
         rtnl_link_unregister(&ipgre_tap_ops);
         rtnl_link_unregister(&ipgre_link_ops);
-        if (inet_del_protocol(&ipgre_protocol, IPPROTO_GRE) < 0)
+        if (gre_del_protocol(&ipgre_protocol, GREPROTO_CISCO) < 0)
                 printk(KERN_INFO "ipgre close: can't remove protocol\n");
         unregister_pernet_device(&ipgre_net_ops);
 }