1 /* 2 * GRE over IPv4 demultiplexer driver 3 * 4 * Authors: Dmitry Kozlov (xeb@mail.ru) 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public License 8 * as published by the Free Software Foundation; either version 9 * 2 of the License, or (at your option) any later version. 10 * 11 */ 12 13 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 14 15 #include <linux/module.h> 16 #include <linux/if.h> 17 #include <linux/icmp.h> 18 #include <linux/kernel.h> 19 #include <linux/kmod.h> 20 #include <linux/skbuff.h> 21 #include <linux/in.h> 22 #include <linux/ip.h> 23 #include <linux/netdevice.h> 24 #include <linux/if_tunnel.h> 25 #include <linux/spinlock.h> 26 #include <net/protocol.h> 27 #include <net/gre.h> 28 29 #include <net/icmp.h> 30 #include <net/route.h> 31 #include <net/xfrm.h> 32 33 static const struct gre_protocol __rcu *gre_proto[GREPROTO_MAX] __read_mostly; 34 35 int gre_add_protocol(const struct gre_protocol *proto, u8 version) 36 { 37 if (version >= GREPROTO_MAX) 38 return -EINVAL; 39 40 return (cmpxchg((const struct gre_protocol **)&gre_proto[version], NULL, proto) == NULL) ? 41 0 : -EBUSY; 42 } 43 EXPORT_SYMBOL_GPL(gre_add_protocol); 44 45 int gre_del_protocol(const struct gre_protocol *proto, u8 version) 46 { 47 int ret; 48 49 if (version >= GREPROTO_MAX) 50 return -EINVAL; 51 52 ret = (cmpxchg((const struct gre_protocol **)&gre_proto[version], proto, NULL) == proto) ? 53 0 : -EBUSY; 54 55 if (ret) 56 return ret; 57 58 synchronize_rcu(); 59 return 0; 60 } 61 EXPORT_SYMBOL_GPL(gre_del_protocol); 62 63 static int gre_rcv(struct sk_buff *skb) 64 { 65 const struct gre_protocol *proto; 66 u8 ver; 67 int ret; 68 69 if (!pskb_may_pull(skb, 12)) 70 goto drop; 71 72 ver = skb->data[1]&0x7f; 73 if (ver >= GREPROTO_MAX) 74 goto drop; 75 76 rcu_read_lock(); 77 proto = rcu_dereference(gre_proto[ver]); 78 if (!proto || !proto->handler) 79 goto drop_unlock; 80 ret = proto->handler(skb); 81 rcu_read_unlock(); 82 return ret; 83 84 drop_unlock: 85 rcu_read_unlock(); 86 drop: 87 kfree_skb(skb); 88 return NET_RX_DROP; 89 } 90 91 static void gre_err(struct sk_buff *skb, u32 info) 92 { 93 const struct gre_protocol *proto; 94 const struct iphdr *iph = (const struct iphdr *)skb->data; 95 u8 ver = skb->data[(iph->ihl<<2) + 1]&0x7f; 96 97 if (ver >= GREPROTO_MAX) 98 return; 99 100 rcu_read_lock(); 101 proto = rcu_dereference(gre_proto[ver]); 102 if (proto && proto->err_handler) 103 proto->err_handler(skb, info); 104 rcu_read_unlock(); 105 } 106 107 static const struct net_protocol net_gre_protocol = { 108 .handler = gre_rcv, 109 .err_handler = gre_err, 110 .netns_ok = 1, 111 }; 112 113 static int __init gre_init(void) 114 { 115 pr_info("GRE over IPv4 demultiplexor driver\n"); 116 117 if (inet_add_protocol(&net_gre_protocol, IPPROTO_GRE) < 0) { 118 pr_err("can't add protocol\n"); 119 return -EAGAIN; 120 } 121 return 0; 122 } 123 124 static void __exit gre_exit(void) 125 { 126 inet_del_protocol(&net_gre_protocol, IPPROTO_GRE); 127 } 128 129 module_init(gre_init); 130 module_exit(gre_exit); 131 132 MODULE_DESCRIPTION("GRE over IPv4 demultiplexer driver"); 133 MODULE_AUTHOR("D. Kozlov (xeb@mail.ru)"); 134 MODULE_LICENSE("GPL"); 135