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 skb_checksum_try_convert(skb, IPPROTO_GRE, 0, 91 null_compute_pseudo); 92 } else if (csum_err) { 93 *csum_err = true; 94 return -EINVAL; 95 } 96 97 options++; 98 } 99 100 if (greh->flags & GRE_KEY) { 101 tpi->key = *options; 102 options++; 103 } else { 104 tpi->key = 0; 105 } 106 if (unlikely(greh->flags & GRE_SEQ)) { 107 tpi->seq = *options; 108 options++; 109 } else { 110 tpi->seq = 0; 111 } 112 /* WCCP version 1 and 2 protocol decoding. 113 * - Change protocol to IPv4/IPv6 114 * - When dealing with WCCPv2, Skip extra 4 bytes in GRE header 115 */ 116 if (greh->flags == 0 && tpi->proto == htons(ETH_P_WCCP)) { 117 tpi->proto = proto; 118 if ((*(u8 *)options & 0xF0) != 0x40) 119 hdr_len += 4; 120 } 121 tpi->hdr_len = hdr_len; 122 return hdr_len; 123 } 124 EXPORT_SYMBOL(gre_parse_header); 125 126 static int gre_rcv(struct sk_buff *skb) 127 { 128 const struct gre_protocol *proto; 129 u8 ver; 130 int ret; 131 132 if (!pskb_may_pull(skb, 12)) 133 goto drop; 134 135 ver = skb->data[1]&0x7f; 136 if (ver >= GREPROTO_MAX) 137 goto drop; 138 139 rcu_read_lock(); 140 proto = rcu_dereference(gre_proto[ver]); 141 if (!proto || !proto->handler) 142 goto drop_unlock; 143 ret = proto->handler(skb); 144 rcu_read_unlock(); 145 return ret; 146 147 drop_unlock: 148 rcu_read_unlock(); 149 drop: 150 kfree_skb(skb); 151 return NET_RX_DROP; 152 } 153 154 static int gre_err(struct sk_buff *skb, u32 info) 155 { 156 const struct gre_protocol *proto; 157 const struct iphdr *iph = (const struct iphdr *)skb->data; 158 u8 ver = skb->data[(iph->ihl<<2) + 1]&0x7f; 159 int err = 0; 160 161 if (ver >= GREPROTO_MAX) 162 return -EINVAL; 163 164 rcu_read_lock(); 165 proto = rcu_dereference(gre_proto[ver]); 166 if (proto && proto->err_handler) 167 proto->err_handler(skb, info); 168 else 169 err = -EPROTONOSUPPORT; 170 rcu_read_unlock(); 171 172 return err; 173 } 174 175 static const struct net_protocol net_gre_protocol = { 176 .handler = gre_rcv, 177 .err_handler = gre_err, 178 .netns_ok = 1, 179 }; 180 181 static int __init gre_init(void) 182 { 183 pr_info("GRE over IPv4 demultiplexor driver\n"); 184 185 if (inet_add_protocol(&net_gre_protocol, IPPROTO_GRE) < 0) { 186 pr_err("can't add protocol\n"); 187 return -EAGAIN; 188 } 189 return 0; 190 } 191 192 static void __exit gre_exit(void) 193 { 194 inet_del_protocol(&net_gre_protocol, IPPROTO_GRE); 195 } 196 197 module_init(gre_init); 198 module_exit(gre_exit); 199 200 MODULE_DESCRIPTION("GRE over IPv4 demultiplexer driver"); 201 MODULE_AUTHOR("D. Kozlov (xeb@mail.ru)"); 202 MODULE_LICENSE("GPL"); 203