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 int gre_parse_header(struct sk_buff *skb, struct tnl_ptk_info *tpi, 61 bool *csum_err, __be16 proto, int nhs) 62 { 63 const struct gre_base_hdr *greh; 64 __be32 *options; 65 int hdr_len; 66 67 if (unlikely(!pskb_may_pull(skb, nhs + sizeof(struct gre_base_hdr)))) 68 return -EINVAL; 69 70 greh = (struct gre_base_hdr *)(skb->data + nhs); 71 if (unlikely(greh->flags & (GRE_VERSION | GRE_ROUTING))) 72 return -EINVAL; 73 74 tpi->flags = gre_flags_to_tnl_flags(greh->flags); 75 hdr_len = gre_calc_hlen(tpi->flags); 76 77 if (!pskb_may_pull(skb, nhs + hdr_len)) 78 return -EINVAL; 79 80 greh = (struct gre_base_hdr *)(skb->data + nhs); 81 tpi->proto = greh->protocol; 82 83 options = (__be32 *)(greh + 1); 84 if (greh->flags & GRE_CSUM) { 85 if (!skb_checksum_simple_validate(skb)) { 86 skb_checksum_try_convert(skb, IPPROTO_GRE, 87 null_compute_pseudo); 88 } else if (csum_err) { 89 *csum_err = true; 90 return -EINVAL; 91 } 92 93 options++; 94 } 95 96 if (greh->flags & GRE_KEY) { 97 tpi->key = *options; 98 options++; 99 } else { 100 tpi->key = 0; 101 } 102 if (unlikely(greh->flags & GRE_SEQ)) { 103 tpi->seq = *options; 104 options++; 105 } else { 106 tpi->seq = 0; 107 } 108 /* WCCP version 1 and 2 protocol decoding. 109 * - Change protocol to IPv4/IPv6 110 * - When dealing with WCCPv2, Skip extra 4 bytes in GRE header 111 */ 112 if (greh->flags == 0 && tpi->proto == htons(ETH_P_WCCP)) { 113 tpi->proto = proto; 114 if ((*(u8 *)options & 0xF0) != 0x40) 115 hdr_len += 4; 116 } 117 tpi->hdr_len = hdr_len; 118 119 /* ERSPAN ver 1 and 2 protocol sets GRE key field 120 * to 0 and sets the configured key in the 121 * inner erspan header field 122 */ 123 if (greh->protocol == htons(ETH_P_ERSPAN) || 124 greh->protocol == htons(ETH_P_ERSPAN2)) { 125 struct erspan_base_hdr *ershdr; 126 127 if (!pskb_may_pull(skb, nhs + hdr_len + sizeof(*ershdr))) 128 return -EINVAL; 129 130 ershdr = (struct erspan_base_hdr *)options; 131 tpi->key = cpu_to_be32(get_session_id(ershdr)); 132 } 133 134 return hdr_len; 135 } 136 EXPORT_SYMBOL(gre_parse_header); 137 138 static int gre_rcv(struct sk_buff *skb) 139 { 140 const struct gre_protocol *proto; 141 u8 ver; 142 int ret; 143 144 if (!pskb_may_pull(skb, 12)) 145 goto drop; 146 147 ver = skb->data[1]&0x7f; 148 if (ver >= GREPROTO_MAX) 149 goto drop; 150 151 rcu_read_lock(); 152 proto = rcu_dereference(gre_proto[ver]); 153 if (!proto || !proto->handler) 154 goto drop_unlock; 155 ret = proto->handler(skb); 156 rcu_read_unlock(); 157 return ret; 158 159 drop_unlock: 160 rcu_read_unlock(); 161 drop: 162 kfree_skb(skb); 163 return NET_RX_DROP; 164 } 165 166 static int gre_err(struct sk_buff *skb, u32 info) 167 { 168 const struct gre_protocol *proto; 169 const struct iphdr *iph = (const struct iphdr *)skb->data; 170 u8 ver = skb->data[(iph->ihl<<2) + 1]&0x7f; 171 int err = 0; 172 173 if (ver >= GREPROTO_MAX) 174 return -EINVAL; 175 176 rcu_read_lock(); 177 proto = rcu_dereference(gre_proto[ver]); 178 if (proto && proto->err_handler) 179 proto->err_handler(skb, info); 180 else 181 err = -EPROTONOSUPPORT; 182 rcu_read_unlock(); 183 184 return err; 185 } 186 187 static const struct net_protocol net_gre_protocol = { 188 .handler = gre_rcv, 189 .err_handler = gre_err, 190 .netns_ok = 1, 191 }; 192 193 static int __init gre_init(void) 194 { 195 pr_info("GRE over IPv4 demultiplexor driver\n"); 196 197 if (inet_add_protocol(&net_gre_protocol, IPPROTO_GRE) < 0) { 198 pr_err("can't add protocol\n"); 199 return -EAGAIN; 200 } 201 return 0; 202 } 203 204 static void __exit gre_exit(void) 205 { 206 inet_del_protocol(&net_gre_protocol, IPPROTO_GRE); 207 } 208 209 module_init(gre_init); 210 module_exit(gre_exit); 211 212 MODULE_DESCRIPTION("GRE over IPv4 demultiplexer driver"); 213 MODULE_AUTHOR("D. Kozlov (xeb@mail.ru)"); 214 MODULE_LICENSE("GPL"); 215