net/dccp/ccid.c

   1 /*
   2  *  net/dccp/ccid.c
   3  *
   4  *  An implementation of the DCCP protocol
   5  *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>
   6  *
   7  *  CCID infrastructure
   8  *
   9  *      This program is free software; you can redistribute it and/or modify it
  10  *      under the terms of the GNU General Public License version 2 as
  11  *      published by the Free Software Foundation.
  12  */
  13
  14 #include "ccid.h"
  15
  16 static struct ccid_operations *ccids[CCID_MAX];
  17 #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT)
  18 static atomic_t ccids_lockct = ATOMIC_INIT(0);
  19 static DEFINE_SPINLOCK(ccids_lock);
  20
  21 /*
  22  * The strategy is: modifications ccids vector are short, do not sleep and
  23  * veeery rare, but read access should be free of any exclusive locks.
  24  */
  25 static void ccids_write_lock(void)
  26 {
  27         spin_lock(&ccids_lock);
  28         while (atomic_read(&ccids_lockct) != 0) {
  29                 spin_unlock(&ccids_lock);
  30                 yield();
  31                 spin_lock(&ccids_lock);
  32         }
  33 }
  34
  35 static inline void ccids_write_unlock(void)
  36 {
  37         spin_unlock(&ccids_lock);
  38 }
  39
  40 static inline void ccids_read_lock(void)
  41 {
  42         atomic_inc(&ccids_lockct);
  43         spin_unlock_wait(&ccids_lock);
  44 }
  45
  46 static inline void ccids_read_unlock(void)
  47 {
  48         atomic_dec(&ccids_lockct);
  49 }
  50
  51 #else
  52 #define ccids_write_lock() do { } while(0)
  53 #define ccids_write_unlock() do { } while(0)
  54 #define ccids_read_lock() do { } while(0)
  55 #define ccids_read_unlock() do { } while(0)
  56 #endif
  57
  58 static struct kmem_cache *ccid_kmem_cache_create(int obj_size, const char *fmt,...)
  59 {
  60         struct kmem_cache *slab;
  61         char slab_name_fmt[32], *slab_name;
  62         va_list args;
  63
  64         va_start(args, fmt);
  65         vsnprintf(slab_name_fmt, sizeof(slab_name_fmt), fmt, args);
  66         va_end(args);
  67
  68         slab_name = kstrdup(slab_name_fmt, GFP_KERNEL);
  69         if (slab_name == NULL)
  70                 return NULL;
  71         slab = kmem_cache_create(slab_name, sizeof(struct ccid) + obj_size, 0,
  72                                  SLAB_HWCACHE_ALIGN, NULL, NULL);
  73         if (slab == NULL)
  74                 kfree(slab_name);
  75         return slab;
  76 }
  77
  78 static void ccid_kmem_cache_destroy(struct kmem_cache *slab)
  79 {
  80         if (slab != NULL) {
  81                 const char *name = kmem_cache_name(slab);
  82
  83                 kmem_cache_destroy(slab);
  84                 kfree(name);
  85         }
  86 }
  87
  88 int ccid_register(struct ccid_operations *ccid_ops)
  89 {
  90         int err = -ENOBUFS;
  91
  92         ccid_ops->ccid_hc_rx_slab =
  93                         ccid_kmem_cache_create(ccid_ops->ccid_hc_rx_obj_size,
  94                                                "%s_hc_rx_sock",
  95                                                ccid_ops->ccid_name);
  96         if (ccid_ops->ccid_hc_rx_slab == NULL)
  97                 goto out;
  98
  99         ccid_ops->ccid_hc_tx_slab =
 100                         ccid_kmem_cache_create(ccid_ops->ccid_hc_tx_obj_size,
 101                                                "%s_hc_tx_sock",
 102                                                ccid_ops->ccid_name);
 103         if (ccid_ops->ccid_hc_tx_slab == NULL)
 104                 goto out_free_rx_slab;
 105
 106         ccids_write_lock();
 107         err = -EEXIST;
 108         if (ccids[ccid_ops->ccid_id] == NULL) {
 109                 ccids[ccid_ops->ccid_id] = ccid_ops;
 110                 err = 0;
 111         }
 112         ccids_write_unlock();
 113         if (err != 0)
 114                 goto out_free_tx_slab;
 115
 116         pr_info("CCID: Registered CCID %d (%s)\n",
 117                 ccid_ops->ccid_id, ccid_ops->ccid_name);
 118 out:
 119         return err;
 120 out_free_tx_slab:
 121         ccid_kmem_cache_destroy(ccid_ops->ccid_hc_tx_slab);
 122         ccid_ops->ccid_hc_tx_slab = NULL;
 123         goto out;
 124 out_free_rx_slab:
 125         ccid_kmem_cache_destroy(ccid_ops->ccid_hc_rx_slab);
 126         ccid_ops->ccid_hc_rx_slab = NULL;
 127         goto out;
 128 }
 129
 130 EXPORT_SYMBOL_GPL(ccid_register);
 131
 132 int ccid_unregister(struct ccid_operations *ccid_ops)
 133 {
 134         ccids_write_lock();
 135         ccids[ccid_ops->ccid_id] = NULL;
 136         ccids_write_unlock();
 137
 138         ccid_kmem_cache_destroy(ccid_ops->ccid_hc_tx_slab);
 139         ccid_ops->ccid_hc_tx_slab = NULL;
 140         ccid_kmem_cache_destroy(ccid_ops->ccid_hc_rx_slab);
 141         ccid_ops->ccid_hc_rx_slab = NULL;
 142
 143         pr_info("CCID: Unregistered CCID %d (%s)\n",
 144                 ccid_ops->ccid_id, ccid_ops->ccid_name);
 145         return 0;
 146 }
 147
 148 EXPORT_SYMBOL_GPL(ccid_unregister);
 149
 150 struct ccid *ccid_new(unsigned char id, struct sock *sk, int rx, gfp_t gfp)
 151 {
 152         struct ccid_operations *ccid_ops;
 153         struct ccid *ccid = NULL;
 154
 155         ccids_read_lock();
 156 #ifdef CONFIG_KMOD
 157         if (ccids[id] == NULL) {
 158                 /* We only try to load if in process context */
 159                 ccids_read_unlock();
 160                 if (gfp & GFP_ATOMIC)
 161                         goto out;
 162                 request_module("net-dccp-ccid-%d", id);
 163                 ccids_read_lock();
 164         }
 165 #endif
 166         ccid_ops = ccids[id];
 167         if (ccid_ops == NULL)
 168                 goto out_unlock;
 169
 170         if (!try_module_get(ccid_ops->ccid_owner))
 171                 goto out_unlock;
 172
 173         ccids_read_unlock();
 174
 175         ccid = kmem_cache_alloc(rx ? ccid_ops->ccid_hc_rx_slab :
 176                                      ccid_ops->ccid_hc_tx_slab, gfp);
 177         if (ccid == NULL)
 178                 goto out_module_put;
 179         ccid->ccid_ops = ccid_ops;
 180         if (rx) {
 181                 memset(ccid + 1, 0, ccid_ops->ccid_hc_rx_obj_size);
 182                 if (ccid->ccid_ops->ccid_hc_rx_init != NULL &&
 183                     ccid->ccid_ops->ccid_hc_rx_init(ccid, sk) != 0)
 184                         goto out_free_ccid;
 185         } else {
 186                 memset(ccid + 1, 0, ccid_ops->ccid_hc_tx_obj_size);
 187                 if (ccid->ccid_ops->ccid_hc_tx_init != NULL &&
 188                     ccid->ccid_ops->ccid_hc_tx_init(ccid, sk) != 0)
 189                         goto out_free_ccid;
 190         }
 191 out:
 192         return ccid;
 193 out_unlock:
 194         ccids_read_unlock();
 195         goto out;
 196 out_free_ccid:
 197         kmem_cache_free(rx ? ccid_ops->ccid_hc_rx_slab :
 198                         ccid_ops->ccid_hc_tx_slab, ccid);
 199         ccid = NULL;
 200 out_module_put:
 201         module_put(ccid_ops->ccid_owner);
 202         goto out;
 203 }
 204
 205 EXPORT_SYMBOL_GPL(ccid_new);
 206
 207 struct ccid *ccid_hc_rx_new(unsigned char id, struct sock *sk, gfp_t gfp)
 208 {
 209         return ccid_new(id, sk, 1, gfp);
 210 }
 211
 212 EXPORT_SYMBOL_GPL(ccid_hc_rx_new);
 213
 214 struct ccid *ccid_hc_tx_new(unsigned char id,struct sock *sk,  gfp_t gfp)
 215 {
 216         return ccid_new(id, sk, 0, gfp);
 217 }
 218
 219 EXPORT_SYMBOL_GPL(ccid_hc_tx_new);
 220
 221 static void ccid_delete(struct ccid *ccid, struct sock *sk, int rx)
 222 {
 223         struct ccid_operations *ccid_ops;
 224
 225         if (ccid == NULL)
 226                 return;
 227
 228         ccid_ops = ccid->ccid_ops;
 229         if (rx) {
 230                 if (ccid_ops->ccid_hc_rx_exit != NULL)
 231                         ccid_ops->ccid_hc_rx_exit(sk);
 232                 kmem_cache_free(ccid_ops->ccid_hc_rx_slab,  ccid);
 233         } else {
 234                 if (ccid_ops->ccid_hc_tx_exit != NULL)
 235                         ccid_ops->ccid_hc_tx_exit(sk);
 236                 kmem_cache_free(ccid_ops->ccid_hc_tx_slab,  ccid);
 237         }
 238         ccids_read_lock();
 239         if (ccids[ccid_ops->ccid_id] != NULL)
 240                 module_put(ccid_ops->ccid_owner);
 241         ccids_read_unlock();
 242 }
 243
 244 void ccid_hc_rx_delete(struct ccid *ccid, struct sock *sk)
 245 {
 246         ccid_delete(ccid, sk, 1);
 247 }
 248
 249 EXPORT_SYMBOL_GPL(ccid_hc_rx_delete);
 250
 251 void ccid_hc_tx_delete(struct ccid *ccid, struct sock *sk)
 252 {
 253         ccid_delete(ccid, sk, 0);
 254 }
 255
 256 EXPORT_SYMBOL_GPL(ccid_hc_tx_delete);