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 /* Fills in tpi and returns header length to be pulled. */ 64 int gre_parse_header(struct sk_buff *skb, struct tnl_ptk_info *tpi, 65 bool *csum_err, __be16 proto, int nhs) 66 { 67 const struct gre_base_hdr *greh; 68 __be32 *options; 69 int hdr_len; 70 71 if (unlikely(!pskb_may_pull(skb, nhs + sizeof(struct gre_base_hdr)))) 72 return -EINVAL; 73 74 greh = (struct gre_base_hdr *)(skb->data + nhs); 75 if (unlikely(greh->flags & (GRE_VERSION | GRE_ROUTING))) 76 return -EINVAL; 77 78 tpi->flags = gre_flags_to_tnl_flags(greh->flags); 79 hdr_len = gre_calc_hlen(tpi->flags); 80 81 if (!pskb_may_pull(skb, nhs + hdr_len)) 82 return -EINVAL; 83 84 greh = (struct gre_base_hdr *)(skb->data + nhs); 85 tpi->proto = greh->protocol; 86 87 options = (__be32 *)(greh + 1); 88 if (greh->flags & GRE_CSUM) { 89 if (skb_checksum_simple_validate(skb)) { 90 *csum_err = true; 91 return -EINVAL; 92 } 93 94 skb_checksum_try_convert(skb, IPPROTO_GRE, 0, 95 null_compute_pseudo); 96 options++; 97 } 98 99 if (greh->flags & GRE_KEY) { 100 tpi->key = *options; 101 options++; 102 } else { 103 tpi->key = 0; 104 } 105 if (unlikely(greh->flags & GRE_SEQ)) { 106 tpi->seq = *options; 107 options++; 108 } else { 109 tpi->seq = 0; 110 } 111 /* WCCP version 1 and 2 protocol decoding. 112 * - Change protocol to IPv4/IPv6 113 * - When dealing with WCCPv2, Skip extra 4 bytes in GRE header 114 */ 115 if (greh->flags == 0 && tpi->proto == htons(ETH_P_WCCP)) { 116 tpi->proto = proto; 117 if ((*(u8 *)options & 0xF0) != 0x40) 118 hdr_len += 4; 119 } 120 return hdr_len; 121 } 122 EXPORT_SYMBOL(gre_parse_header); 123 124 static int gre_rcv(struct sk_buff *skb) 125 { 126 const struct gre_protocol *proto; 127 u8 ver; 128 int ret; 129 130 if (!pskb_may_pull(skb, 12)) 131 goto drop; 132 133 ver = skb->data[1]&0x7f; 134 if (ver >= GREPROTO_MAX) 135 goto drop; 136 137 rcu_read_lock(); 138 proto = rcu_dereference(gre_proto[ver]); 139 if (!proto || !proto->handler) 140 goto drop_unlock; 141 ret = proto->handler(skb); 142 rcu_read_unlock(); 143 return ret; 144 145 drop_unlock: 146 rcu_read_unlock(); 147 drop: 148 kfree_skb(skb); 149 return NET_RX_DROP; 150 } 151 152 static void gre_err(struct sk_buff *skb, u32 info) 153 { 154 const struct gre_protocol *proto; 155 const struct iphdr *iph = (const struct iphdr *)skb->data; 156 u8 ver = skb->data[(iph->ihl<<2) + 1]&0x7f; 157 158 if (ver >= GREPROTO_MAX) 159 return; 160 161 rcu_read_lock(); 162 proto = rcu_dereference(gre_proto[ver]); 163 if (proto && proto->err_handler) 164 proto->err_handler(skb, info); 165 rcu_read_unlock(); 166 } 167 168 static const struct net_protocol net_gre_protocol = { 169 .handler = gre_rcv, 170 .err_handler = gre_err, 171 .netns_ok = 1, 172 }; 173 174 static int __init gre_init(void) 175 { 176 pr_info("GRE over IPv4 demultiplexor driver\n"); 177 178 if (inet_add_protocol(&net_gre_protocol, IPPROTO_GRE) < 0) { 179 pr_err("can't add protocol\n"); 180 return -EAGAIN; 181 } 182 return 0; 183 } 184 185 static void __exit gre_exit(void) 186 { 187 inet_del_protocol(&net_gre_protocol, IPPROTO_GRE); 188 } 189 190 module_init(gre_init); 191 module_exit(gre_exit); 192 193 MODULE_DESCRIPTION("GRE over IPv4 demultiplexer driver"); 194 MODULE_AUTHOR("D. Kozlov (xeb@mail.ru)"); 195 MODULE_LICENSE("GPL"); 196