1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * GRE over IPv4 demultiplexer driver 4 * 5 * Authors: Dmitry Kozlov (xeb@mail.ru) 6 */ 7 8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 9 10 #include <linux/module.h> 11 #include <linux/if.h> 12 #include <linux/icmp.h> 13 #include <linux/kernel.h> 14 #include <linux/kmod.h> 15 #include <linux/skbuff.h> 16 #include <linux/in.h> 17 #include <linux/ip.h> 18 #include <linux/netdevice.h> 19 #include <linux/if_tunnel.h> 20 #include <linux/spinlock.h> 21 #include <net/protocol.h> 22 #include <net/gre.h> 23 #include <net/erspan.h> 24 25 #include <net/icmp.h> 26 #include <net/route.h> 27 #include <net/xfrm.h> 28 29 static const struct gre_protocol __rcu *gre_proto[GREPROTO_MAX] __read_mostly; 30 31 int gre_add_protocol(const struct gre_protocol *proto, u8 version) 32 { 33 if (version >= GREPROTO_MAX) 34 return -EINVAL; 35 36 return (cmpxchg((const struct gre_protocol **)&gre_proto[version], NULL, proto) == NULL) ? 37 0 : -EBUSY; 38 } 39 EXPORT_SYMBOL_GPL(gre_add_protocol); 40 41 int gre_del_protocol(const struct gre_protocol *proto, u8 version) 42 { 43 int ret; 44 45 if (version >= GREPROTO_MAX) 46 return -EINVAL; 47 48 ret = (cmpxchg((const struct gre_protocol **)&gre_proto[version], proto, NULL) == proto) ? 49 0 : -EBUSY; 50 51 if (ret) 52 return ret; 53 54 synchronize_rcu(); 55 return 0; 56 } 57 EXPORT_SYMBOL_GPL(gre_del_protocol); 58 59 /* Fills in tpi and returns header length to be pulled. 60 * Note that caller must use pskb_may_pull() before pulling GRE header. 61 */ 62 int gre_parse_header(struct sk_buff *skb, struct tnl_ptk_info *tpi, 63 bool *csum_err, __be16 proto, int nhs) 64 { 65 const struct gre_base_hdr *greh; 66 __be32 *options; 67 int hdr_len; 68 69 if (unlikely(!pskb_may_pull(skb, nhs + sizeof(struct gre_base_hdr)))) 70 return -EINVAL; 71 72 greh = (struct gre_base_hdr *)(skb->data + nhs); 73 if (unlikely(greh->flags & (GRE_VERSION | GRE_ROUTING))) 74 return -EINVAL; 75 76 tpi->flags = gre_flags_to_tnl_flags(greh->flags); 77 hdr_len = gre_calc_hlen(tpi->flags); 78 79 if (!pskb_may_pull(skb, nhs + hdr_len)) 80 return -EINVAL; 81 82 greh = (struct gre_base_hdr *)(skb->data + nhs); 83 tpi->proto = greh->protocol; 84 85 options = (__be32 *)(greh + 1); 86 if (greh->flags & GRE_CSUM) { 87 if (!skb_checksum_simple_validate(skb)) { 88 skb_checksum_try_convert(skb, IPPROTO_GRE, 89 null_compute_pseudo); 90 } else if (csum_err) { 91 *csum_err = true; 92 return -EINVAL; 93 } 94 95 options++; 96 } 97 98 if (greh->flags & GRE_KEY) { 99 tpi->key = *options; 100 options++; 101 } else { 102 tpi->key = 0; 103 } 104 if (unlikely(greh->flags & GRE_SEQ)) { 105 tpi->seq = *options; 106 options++; 107 } else { 108 tpi->seq = 0; 109 } 110 /* WCCP version 1 and 2 protocol decoding. 111 * - Change protocol to IPv4/IPv6 112 * - When dealing with WCCPv2, Skip extra 4 bytes in GRE header 113 */ 114 if (greh->flags == 0 && tpi->proto == htons(ETH_P_WCCP)) { 115 u8 _val, *val; 116 117 val = skb_header_pointer(skb, nhs + hdr_len, 118 sizeof(_val), &_val); 119 if (!val) 120 return -EINVAL; 121 tpi->proto = proto; 122 if ((*val & 0xF0) != 0x40) 123 hdr_len += 4; 124 } 125 tpi->hdr_len = hdr_len; 126 127 /* ERSPAN ver 1 and 2 protocol sets GRE key field 128 * to 0 and sets the configured key in the 129 * inner erspan header field 130 */ 131 if ((greh->protocol == htons(ETH_P_ERSPAN) && hdr_len != 4) || 132 greh->protocol == htons(ETH_P_ERSPAN2)) { 133 struct erspan_base_hdr *ershdr; 134 135 if (!pskb_may_pull(skb, nhs + hdr_len + sizeof(*ershdr))) 136 return -EINVAL; 137 138 ershdr = (struct erspan_base_hdr *)(skb->data + nhs + hdr_len); 139 tpi->key = cpu_to_be32(get_session_id(ershdr)); 140 } 141 142 return hdr_len; 143 } 144 EXPORT_SYMBOL(gre_parse_header); 145 146 static int gre_rcv(struct sk_buff *skb) 147 { 148 const struct gre_protocol *proto; 149 u8 ver; 150 int ret; 151 152 if (!pskb_may_pull(skb, 12)) 153 goto drop; 154 155 ver = skb->data[1]&0x7f; 156 if (ver >= GREPROTO_MAX) 157 goto drop; 158 159 rcu_read_lock(); 160 proto = rcu_dereference(gre_proto[ver]); 161 if (!proto || !proto->handler) 162 goto drop_unlock; 163 ret = proto->handler(skb); 164 rcu_read_unlock(); 165 return ret; 166 167 drop_unlock: 168 rcu_read_unlock(); 169 drop: 170 kfree_skb(skb); 171 return NET_RX_DROP; 172 } 173 174 static int gre_err(struct sk_buff *skb, u32 info) 175 { 176 const struct gre_protocol *proto; 177 const struct iphdr *iph = (const struct iphdr *)skb->data; 178 u8 ver = skb->data[(iph->ihl<<2) + 1]&0x7f; 179 int err = 0; 180 181 if (ver >= GREPROTO_MAX) 182 return -EINVAL; 183 184 rcu_read_lock(); 185 proto = rcu_dereference(gre_proto[ver]); 186 if (proto && proto->err_handler) 187 proto->err_handler(skb, info); 188 else 189 err = -EPROTONOSUPPORT; 190 rcu_read_unlock(); 191 192 return err; 193 } 194 195 static const struct net_protocol net_gre_protocol = { 196 .handler = gre_rcv, 197 .err_handler = gre_err, 198 .netns_ok = 1, 199 }; 200 201 static int __init gre_init(void) 202 { 203 pr_info("GRE over IPv4 demultiplexor driver\n"); 204 205 if (inet_add_protocol(&net_gre_protocol, IPPROTO_GRE) < 0) { 206 pr_err("can't add protocol\n"); 207 return -EAGAIN; 208 } 209 return 0; 210 } 211 212 static void __exit gre_exit(void) 213 { 214 inet_del_protocol(&net_gre_protocol, IPPROTO_GRE); 215 } 216 217 module_init(gre_init); 218 module_exit(gre_exit); 219 220 MODULE_DESCRIPTION("GRE over IPv4 demultiplexer driver"); 221 MODULE_AUTHOR("D. Kozlov (xeb@mail.ru)"); 222 MODULE_LICENSE("GPL"); 223