net/ipv4/gre.c

   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/kernel.h>
  17 #include <linux/kmod.h>
  18 #include <linux/skbuff.h>
  19 #include <linux/in.h>
  20 #include <linux/ip.h>
  21 #include <linux/netdevice.h>
  22 #include <linux/if_tunnel.h>
  23 #include <linux/spinlock.h>
  24 #include <net/protocol.h>
  25 #include <net/gre.h>
  26
  27
  28 static const struct gre_protocol __rcu *gre_proto[GREPROTO_MAX] __read_mostly;
  29 static DEFINE_SPINLOCK(gre_proto_lock);
  30
  31 int gre_add_protocol(const struct gre_protocol *proto, u8 version)
  32 {
  33         if (version >= GREPROTO_MAX)
  34                 goto err_out;
  35
  36         spin_lock(&gre_proto_lock);
  37         if (gre_proto[version])
  38                 goto err_out_unlock;
  39
  40         RCU_INIT_POINTER(gre_proto[version], proto);
  41         spin_unlock(&gre_proto_lock);
  42         return 0;
  43
  44 err_out_unlock:
  45         spin_unlock(&gre_proto_lock);
  46 err_out:
  47         return -1;
  48 }
  49 EXPORT_SYMBOL_GPL(gre_add_protocol);
  50
  51 int gre_del_protocol(const struct gre_protocol *proto, u8 version)
  52 {
  53         if (version >= GREPROTO_MAX)
  54                 goto err_out;
  55
  56         spin_lock(&gre_proto_lock);
  57         if (rcu_dereference_protected(gre_proto[version],
  58                         lockdep_is_held(&gre_proto_lock)) != proto)
  59                 goto err_out_unlock;
  60         RCU_INIT_POINTER(gre_proto[version], NULL);
  61         spin_unlock(&gre_proto_lock);
  62         synchronize_rcu();
  63         return 0;
  64
  65 err_out_unlock:
  66         spin_unlock(&gre_proto_lock);
  67 err_out:
  68         return -1;
  69 }
  70 EXPORT_SYMBOL_GPL(gre_del_protocol);
  71
  72 static int gre_rcv(struct sk_buff *skb)
  73 {
  74         const struct gre_protocol *proto;
  75         u8 ver;
  76         int ret;
  77
  78         if (!pskb_may_pull(skb, 12))
  79                 goto drop;
  80
  81         ver = skb->data[1]&0x7f;
  82         if (ver >= GREPROTO_MAX)
  83                 goto drop;
  84
  85         rcu_read_lock();
  86         proto = rcu_dereference(gre_proto[ver]);
  87         if (!proto || !proto->handler)
  88                 goto drop_unlock;
  89         ret = proto->handler(skb);
  90         rcu_read_unlock();
  91         return ret;
  92
  93 drop_unlock:
  94         rcu_read_unlock();
  95 drop:
  96         kfree_skb(skb);
  97         return NET_RX_DROP;
  98 }
  99
 100 static void gre_err(struct sk_buff *skb, u32 info)
 101 {
 102         const struct gre_protocol *proto;
 103         const struct iphdr *iph = (const struct iphdr *)skb->data;
 104         u8 ver = skb->data[(iph->ihl<<2) + 1]&0x7f;
 105
 106         if (ver >= GREPROTO_MAX)
 107                 return;
 108
 109         rcu_read_lock();
 110         proto = rcu_dereference(gre_proto[ver]);
 111         if (proto && proto->err_handler)
 112                 proto->err_handler(skb, info);
 113         rcu_read_unlock();
 114 }
 115
 116 static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
 117                                        netdev_features_t features)
 118 {
 119         struct sk_buff *segs = ERR_PTR(-EINVAL);
 120         netdev_features_t enc_features;
 121         int ghl = GRE_HEADER_SECTION;
 122         struct gre_base_hdr *greh;
 123         int mac_len = skb->mac_len;
 124         __be16 protocol = skb->protocol;
 125         int tnl_hlen;
 126         bool csum;
 127
 128         if (unlikely(skb_shinfo(skb)->gso_type &
 129                                 ~(SKB_GSO_TCPV4 |
 130                                   SKB_GSO_TCPV6 |
 131                                   SKB_GSO_UDP |
 132                                   SKB_GSO_DODGY |
 133                                   SKB_GSO_TCP_ECN |
 134                                   SKB_GSO_GRE)))
 135                 goto out;
 136
 137         if (unlikely(!pskb_may_pull(skb, sizeof(*greh))))
 138                 goto out;
 139
 140         greh = (struct gre_base_hdr *)skb_transport_header(skb);
 141
 142         if (greh->flags & GRE_KEY)
 143                 ghl += GRE_HEADER_SECTION;
 144         if (greh->flags & GRE_SEQ)
 145                 ghl += GRE_HEADER_SECTION;
 146         if (greh->flags & GRE_CSUM) {
 147                 ghl += GRE_HEADER_SECTION;
 148                 csum = true;
 149         } else
 150                 csum = false;
 151
 152         /* setup inner skb. */
 153         skb->protocol = greh->protocol;
 154         skb->encapsulation = 0;
 155
 156         if (unlikely(!pskb_may_pull(skb, ghl)))
 157                 goto out;
 158         __skb_pull(skb, ghl);
 159         skb_reset_mac_header(skb);
 160         skb_set_network_header(skb, skb_inner_network_offset(skb));
 161         skb->mac_len = skb_inner_network_offset(skb);
 162
 163         /* segment inner packet. */
 164         enc_features = skb->dev->hw_enc_features & netif_skb_features(skb);
 165         segs = skb_mac_gso_segment(skb, enc_features);
 166         if (!segs || IS_ERR(segs))
 167                 goto out;
 168
 169         skb = segs;
 170         tnl_hlen = skb_tnl_header_len(skb);
 171         do {
 172                 __skb_push(skb, ghl);
 173                 if (csum) {
 174                         __be32 *pcsum;
 175
 176                         if (skb_has_shared_frag(skb)) {
 177                                 int err;
 178
 179                                 err = __skb_linearize(skb);
 180                                 if (err) {
 181                                         kfree_skb_list(segs);
 182                                         segs = ERR_PTR(err);
 183                                         goto out;
 184                                 }
 185                         }
 186
 187                         greh = (struct gre_base_hdr *)(skb->data);
 188                         pcsum = (__be32 *)(greh + 1);
 189                         *pcsum = 0;
 190                         *(__sum16 *)pcsum = csum_fold(skb_checksum(skb, 0, skb->len, 0));
 191                 }
 192                 __skb_push(skb, tnl_hlen - ghl);
 193
 194                 skb_reset_mac_header(skb);
 195                 skb_set_network_header(skb, mac_len);
 196                 skb->mac_len = mac_len;
 197                 skb->protocol = protocol;
 198         } while ((skb = skb->next));
 199 out:
 200         return segs;
 201 }
 202
 203 static int gre_gso_send_check(struct sk_buff *skb)
 204 {
 205         if (!skb->encapsulation)
 206                 return -EINVAL;
 207         return 0;
 208 }
 209
 210 static const struct net_protocol net_gre_protocol = {
 211         .handler     = gre_rcv,
 212         .err_handler = gre_err,
 213         .netns_ok    = 1,
 214 };
 215
 216 static const struct net_offload gre_offload = {
 217         .callbacks = {
 218                 .gso_send_check =       gre_gso_send_check,
 219                 .gso_segment    =       gre_gso_segment,
 220         },
 221 };
 222
 223 static int __init gre_init(void)
 224 {
 225         pr_info("GRE over IPv4 demultiplexor driver\n");
 226
 227         if (inet_add_protocol(&net_gre_protocol, IPPROTO_GRE) < 0) {
 228                 pr_err("can't add protocol\n");
 229                 return -EAGAIN;
 230         }
 231
 232         if (inet_add_offload(&gre_offload, IPPROTO_GRE)) {
 233                 pr_err("can't add protocol offload\n");
 234                 inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
 235                 return -EAGAIN;
 236         }
 237
 238         return 0;
 239 }
 240
 241 static void __exit gre_exit(void)
 242 {
 243         inet_del_offload(&gre_offload, IPPROTO_GRE);
 244         inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
 245 }
 246
 247 module_init(gre_init);
 248 module_exit(gre_exit);
 249
 250 MODULE_DESCRIPTION("GRE over IPv4 demultiplexer driver");
 251 MODULE_AUTHOR("D. Kozlov (xeb@mail.ru)");
 252 MODULE_LICENSE("GPL");
 253