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 struct gre_base_hdr {
  31         __be16 flags;
  32         __be16 protocol;
  33 };
  34 #define GRE_HEADER_SECTION 4
  35
  36 int gre_add_protocol(const struct gre_protocol *proto, u8 version)
  37 {
  38         if (version >= GREPROTO_MAX)
  39                 goto err_out;
  40
  41         spin_lock(&gre_proto_lock);
  42         if (gre_proto[version])
  43                 goto err_out_unlock;
  44
  45         RCU_INIT_POINTER(gre_proto[version], proto);
  46         spin_unlock(&gre_proto_lock);
  47         return 0;
  48
  49 err_out_unlock:
  50         spin_unlock(&gre_proto_lock);
  51 err_out:
  52         return -1;
  53 }
  54 EXPORT_SYMBOL_GPL(gre_add_protocol);
  55
  56 int gre_del_protocol(const struct gre_protocol *proto, u8 version)
  57 {
  58         if (version >= GREPROTO_MAX)
  59                 goto err_out;
  60
  61         spin_lock(&gre_proto_lock);
  62         if (rcu_dereference_protected(gre_proto[version],
  63                         lockdep_is_held(&gre_proto_lock)) != proto)
  64                 goto err_out_unlock;
  65         RCU_INIT_POINTER(gre_proto[version], NULL);
  66         spin_unlock(&gre_proto_lock);
  67         synchronize_rcu();
  68         return 0;
  69
  70 err_out_unlock:
  71         spin_unlock(&gre_proto_lock);
  72 err_out:
  73         return -1;
  74 }
  75 EXPORT_SYMBOL_GPL(gre_del_protocol);
  76
  77 static int gre_rcv(struct sk_buff *skb)
  78 {
  79         const struct gre_protocol *proto;
  80         u8 ver;
  81         int ret;
  82
  83         if (!pskb_may_pull(skb, 12))
  84                 goto drop;
  85
  86         ver = skb->data[1]&0x7f;
  87         if (ver >= GREPROTO_MAX)
  88                 goto drop;
  89
  90         rcu_read_lock();
  91         proto = rcu_dereference(gre_proto[ver]);
  92         if (!proto || !proto->handler)
  93                 goto drop_unlock;
  94         ret = proto->handler(skb);
  95         rcu_read_unlock();
  96         return ret;
  97
  98 drop_unlock:
  99         rcu_read_unlock();
 100 drop:
 101         kfree_skb(skb);
 102         return NET_RX_DROP;
 103 }
 104
 105 static void gre_err(struct sk_buff *skb, u32 info)
 106 {
 107         const struct gre_protocol *proto;
 108         const struct iphdr *iph = (const struct iphdr *)skb->data;
 109         u8 ver = skb->data[(iph->ihl<<2) + 1]&0x7f;
 110
 111         if (ver >= GREPROTO_MAX)
 112                 return;
 113
 114         rcu_read_lock();
 115         proto = rcu_dereference(gre_proto[ver]);
 116         if (proto && proto->err_handler)
 117                 proto->err_handler(skb, info);
 118         rcu_read_unlock();
 119 }
 120
 121 static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
 122                                        netdev_features_t features)
 123 {
 124         struct sk_buff *segs = ERR_PTR(-EINVAL);
 125         netdev_features_t enc_features;
 126         int ghl = GRE_HEADER_SECTION;
 127         struct gre_base_hdr *greh;
 128         int mac_len = skb->mac_len;
 129         int tnl_hlen;
 130         bool csum;
 131
 132         if (unlikely(skb_shinfo(skb)->gso_type &
 133                                 ~(SKB_GSO_TCPV4 |
 134                                   SKB_GSO_TCPV6 |
 135                                   SKB_GSO_UDP |
 136                                   SKB_GSO_DODGY |
 137                                   SKB_GSO_TCP_ECN |
 138                                   SKB_GSO_GRE)))
 139                 goto out;
 140
 141         if (unlikely(!pskb_may_pull(skb, sizeof(*greh))))
 142                 goto out;
 143
 144         greh = (struct gre_base_hdr *)skb_transport_header(skb);
 145
 146         if (greh->flags & GRE_KEY)
 147                 ghl += GRE_HEADER_SECTION;
 148         if (greh->flags & GRE_SEQ)
 149                 ghl += GRE_HEADER_SECTION;
 150         if (greh->flags & GRE_CSUM) {
 151                 ghl += GRE_HEADER_SECTION;
 152                 csum = true;
 153         } else
 154                 csum = false;
 155
 156         /* setup inner skb. */
 157         if (greh->protocol == htons(ETH_P_TEB)) {
 158                 struct ethhdr *eth = eth_hdr(skb);
 159                 skb->protocol = eth->h_proto;
 160         } else {
 161                 skb->protocol = greh->protocol;
 162         }
 163
 164         skb->encapsulation = 0;
 165
 166         if (unlikely(!pskb_may_pull(skb, ghl)))
 167                 goto out;
 168         __skb_pull(skb, ghl);
 169         skb_reset_mac_header(skb);
 170         skb_set_network_header(skb, skb_inner_network_offset(skb));
 171         skb->mac_len = skb_inner_network_offset(skb);
 172
 173         /* segment inner packet. */
 174         enc_features = skb->dev->hw_enc_features & netif_skb_features(skb);
 175         segs = skb_mac_gso_segment(skb, enc_features);
 176         if (!segs || IS_ERR(segs))
 177                 goto out;
 178
 179         skb = segs;
 180         tnl_hlen = skb_tnl_header_len(skb);
 181         do {
 182                 __skb_push(skb, ghl);
 183                 if (csum) {
 184                         __be32 *pcsum;
 185
 186                         if (skb_has_shared_frag(skb)) {
 187                                 int err;
 188
 189                                 err = __skb_linearize(skb);
 190                                 if (err) {
 191                                         kfree_skb(segs);
 192                                         segs = ERR_PTR(err);
 193                                         goto out;
 194                                 }
 195                         }
 196
 197                         greh = (struct gre_base_hdr *)(skb->data);
 198                         pcsum = (__be32 *)(greh + 1);
 199                         *pcsum = 0;
 200                         *(__sum16 *)pcsum = csum_fold(skb_checksum(skb, 0, skb->len, 0));
 201                 }
 202                 __skb_push(skb, tnl_hlen - ghl);
 203
 204                 skb_reset_mac_header(skb);
 205                 skb_set_network_header(skb, mac_len);
 206                 skb->mac_len = mac_len;
 207         } while ((skb = skb->next));
 208 out:
 209         return segs;
 210 }
 211
 212 static int gre_gso_send_check(struct sk_buff *skb)
 213 {
 214         if (!skb->encapsulation)
 215                 return -EINVAL;
 216         return 0;
 217 }
 218
 219 static const struct net_protocol net_gre_protocol = {
 220         .handler     = gre_rcv,
 221         .err_handler = gre_err,
 222         .netns_ok    = 1,
 223 };
 224
 225 static const struct net_offload gre_offload = {
 226         .callbacks = {
 227                 .gso_send_check =       gre_gso_send_check,
 228                 .gso_segment    =       gre_gso_segment,
 229         },
 230 };
 231
 232 static int __init gre_init(void)
 233 {
 234         pr_info("GRE over IPv4 demultiplexor driver\n");
 235
 236         if (inet_add_protocol(&net_gre_protocol, IPPROTO_GRE) < 0) {
 237                 pr_err("can't add protocol\n");
 238                 return -EAGAIN;
 239         }
 240
 241         if (inet_add_offload(&gre_offload, IPPROTO_GRE)) {
 242                 pr_err("can't add protocol offload\n");
 243                 inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
 244                 return -EAGAIN;
 245         }
 246
 247         return 0;
 248 }
 249
 250 static void __exit gre_exit(void)
 251 {
 252         inet_del_offload(&gre_offload, IPPROTO_GRE);
 253         inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
 254 }
 255
 256 module_init(gre_init);
 257 module_exit(gre_exit);
 258
 259 MODULE_DESCRIPTION("GRE over IPv4 demultiplexer driver");
 260 MODULE_AUTHOR("D. Kozlov (xeb@mail.ru)");
 261 MODULE_LICENSE("GPL");
 262