1 files changed, 152 insertions, 0 deletions

diff --git a/net/ipv4/gre.c b/net/ipv4/gre.c
new file mode 100644
index 000000000000..c6933f2ea310
--- /dev/null
+++ b/net/ipv4/gre.c
@@ -0,0 +1,152 @@
+/*
+ *      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>
+
+
+static const struct gre_protocol __rcu *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 (rcu_dereference_protected(gre_proto[version],
+                        lockdep_is_held(&gre_proto_lock)) != 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");
+