fs/afs/addr_list.c

   1 /* Server address list management
   2  *
   3  * Copyright (C) 2017 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public Licence
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the Licence, or (at your option) any later version.
  10  */
  11
  12 #include <linux/slab.h>
  13 #include <linux/ctype.h>
  14 #include <linux/dns_resolver.h>
  15 #include <linux/inet.h>
  16 #include <keys/rxrpc-type.h>
  17 #include "internal.h"
  18 #include "afs_fs.h"
  19
  20 #define AFS_MAX_ADDRESSES                                               \
  21         ((unsigned int)((PAGE_SIZE - sizeof(struct afs_addr_list)) /    \
  22                         sizeof(struct sockaddr_rxrpc)))
  23
  24 /*
  25  * Release an address list.
  26  */
  27 void afs_put_addrlist(struct afs_addr_list *alist)
  28 {
  29         if (alist && refcount_dec_and_test(&alist->usage))
  30                 call_rcu(&alist->rcu, (rcu_callback_t)kfree);
  31 }
  32
  33 /*
  34  * Allocate an address list.
  35  */
  36 struct afs_addr_list *afs_alloc_addrlist(unsigned int nr,
  37                                          unsigned short service,
  38                                          unsigned short port)
  39 {
  40         struct afs_addr_list *alist;
  41         unsigned int i;
  42
  43         _enter("%u,%u,%u", nr, service, port);
  44
  45         alist = kzalloc(sizeof(*alist) + sizeof(alist->addrs[0]) * nr,
  46                         GFP_KERNEL);
  47         if (!alist)
  48                 return NULL;
  49
  50         refcount_set(&alist->usage, 1);
  51
  52         for (i = 0; i < nr; i++) {
  53                 struct sockaddr_rxrpc *srx = &alist->addrs[i];
  54                 srx->srx_family                 = AF_RXRPC;
  55                 srx->srx_service                = service;
  56                 srx->transport_type             = SOCK_DGRAM;
  57                 srx->transport_len              = sizeof(srx->transport.sin6);
  58                 srx->transport.sin6.sin6_family = AF_INET6;
  59                 srx->transport.sin6.sin6_port   = htons(port);
  60         }
  61
  62         return alist;
  63 }
  64
  65 /*
  66  * Parse a text string consisting of delimited addresses.
  67  */
  68 struct afs_addr_list *afs_parse_text_addrs(const char *text, size_t len,
  69                                            char delim,
  70                                            unsigned short service,
  71                                            unsigned short port)
  72 {
  73         struct afs_addr_list *alist;
  74         const char *p, *end = text + len;
  75         unsigned int nr = 0;
  76
  77         _enter("%*.*s,%c", (int)len, (int)len, text, delim);
  78
  79         if (!len)
  80                 return ERR_PTR(-EDESTADDRREQ);
  81
  82         if (delim == ':' && (memchr(text, ',', len) || !memchr(text, '.', len)))
  83                 delim = ',';
  84
  85         /* Count the addresses */
  86         p = text;
  87         do {
  88                 if (!*p)
  89                         return ERR_PTR(-EINVAL);
  90                 if (*p == delim)
  91                         continue;
  92                 nr++;
  93                 if (*p == '[') {
  94                         p++;
  95                         if (p == end)
  96                                 return ERR_PTR(-EINVAL);
  97                         p = memchr(p, ']', end - p);
  98                         if (!p)
  99                                 return ERR_PTR(-EINVAL);
 100                         p++;
 101                         if (p >= end)
 102                                 break;
 103                 }
 104
 105                 p = memchr(p, delim, end - p);
 106                 if (!p)
 107                         break;
 108                 p++;
 109         } while (p < end);
 110
 111         _debug("%u/%u addresses", nr, AFS_MAX_ADDRESSES);
 112         if (nr > AFS_MAX_ADDRESSES)
 113                 nr = AFS_MAX_ADDRESSES;
 114
 115         alist = afs_alloc_addrlist(nr, service, port);
 116         if (!alist)
 117                 return ERR_PTR(-ENOMEM);
 118
 119         /* Extract the addresses */
 120         p = text;
 121         do {
 122                 struct sockaddr_rxrpc *srx = &alist->addrs[alist->nr_addrs];
 123                 char tdelim = delim;
 124
 125                 if (*p == delim) {
 126                         p++;
 127                         continue;
 128                 }
 129
 130                 if (*p == '[') {
 131                         p++;
 132                         tdelim = ']';
 133                 }
 134
 135                 if (in4_pton(p, end - p,
 136                              (u8 *)&srx->transport.sin6.sin6_addr.s6_addr32[3],
 137                              tdelim, &p)) {
 138                         srx->transport.sin6.sin6_addr.s6_addr32[0] = 0;
 139                         srx->transport.sin6.sin6_addr.s6_addr32[1] = 0;
 140                         srx->transport.sin6.sin6_addr.s6_addr32[2] = htonl(0xffff);
 141                 } else if (in6_pton(p, end - p,
 142                                     srx->transport.sin6.sin6_addr.s6_addr,
 143                                     tdelim, &p)) {
 144                         /* Nothing to do */
 145                 } else {
 146                         goto bad_address;
 147                 }
 148
 149                 if (tdelim == ']') {
 150                         if (p == end || *p != ']')
 151                                 goto bad_address;
 152                         p++;
 153                 }
 154
 155                 if (p < end) {
 156                         if (*p == '+') {
 157                                 /* Port number specification "+1234" */
 158                                 unsigned int xport = 0;
 159                                 p++;
 160                                 if (p >= end || !isdigit(*p))
 161                                         goto bad_address;
 162                                 do {
 163                                         xport *= 10;
 164                                         xport += *p - '0';
 165                                         if (xport > 65535)
 166                                                 goto bad_address;
 167                                         p++;
 168                                 } while (p < end && isdigit(*p));
 169                                 srx->transport.sin6.sin6_port = htons(xport);
 170                         } else if (*p == delim) {
 171                                 p++;
 172                         } else {
 173                                 goto bad_address;
 174                         }
 175                 }
 176
 177                 alist->nr_addrs++;
 178         } while (p < end && alist->nr_addrs < AFS_MAX_ADDRESSES);
 179
 180         _leave(" = [nr %u]", alist->nr_addrs);
 181         return alist;
 182
 183 bad_address:
 184         kfree(alist);
 185         return ERR_PTR(-EINVAL);
 186 }
 187
 188 /*
 189  * Compare old and new address lists to see if there's been any change.
 190  * - How to do this in better than O(Nlog(N)) time?
 191  *   - We don't really want to sort the address list, but would rather take the
 192  *     list as we got it so as not to undo record rotation by the DNS server.
 193  */
 194 #if 0
 195 static int afs_cmp_addr_list(const struct afs_addr_list *a1,
 196                              const struct afs_addr_list *a2)
 197 {
 198 }
 199 #endif
 200
 201 /*
 202  * Perform a DNS query for VL servers and build a up an address list.
 203  */
 204 struct afs_addr_list *afs_dns_query(struct afs_cell *cell, time64_t *_expiry)
 205 {
 206         struct afs_addr_list *alist;
 207         char *vllist = NULL;
 208         int ret;
 209
 210         _enter("%s", cell->name);
 211
 212         ret = dns_query("afsdb", cell->name, cell->name_len,
 213                         "ipv4", &vllist, _expiry);
 214         if (ret < 0)
 215                 return ERR_PTR(ret);
 216
 217         alist = afs_parse_text_addrs(vllist, strlen(vllist), ',',
 218                                      VL_SERVICE, AFS_VL_PORT);
 219         if (IS_ERR(alist)) {
 220                 kfree(vllist);
 221                 if (alist != ERR_PTR(-ENOMEM))
 222                         pr_err("Failed to parse DNS data\n");
 223                 return alist;
 224         }
 225
 226         kfree(vllist);
 227         return alist;
 228 }
 229
 230 /*
 231  * Merge an IPv4 entry into a fileserver address list.
 232  */
 233 void afs_merge_fs_addr4(struct afs_addr_list *alist, __be32 xdr)
 234 {
 235         struct sockaddr_in6 *a;
 236         int i;
 237
 238         for (i = 0; i < alist->nr_ipv4; i++) {
 239                 a = &alist->addrs[i].transport.sin6;
 240                 if (xdr == a->sin6_addr.s6_addr32[3])
 241                         return;
 242                 if (xdr < a->sin6_addr.s6_addr32[3])
 243                         break;
 244         }
 245
 246         if (i < alist->nr_addrs)
 247                 memmove(alist->addrs + i + 1,
 248                         alist->addrs + i,
 249                         sizeof(alist->addrs[0]) * (alist->nr_addrs - i));
 250
 251         a = &alist->addrs[i].transport.sin6;
 252         a->sin6_port              = htons(AFS_FS_PORT);
 253         a->sin6_addr.s6_addr32[0] = 0;
 254         a->sin6_addr.s6_addr32[1] = 0;
 255         a->sin6_addr.s6_addr32[2] = htonl(0xffff);
 256         a->sin6_addr.s6_addr32[3] = xdr;
 257         alist->nr_ipv4++;
 258         alist->nr_addrs++;
 259 }
 260
 261 /*
 262  * Get an address to try.
 263  */
 264 bool afs_iterate_addresses(struct afs_addr_cursor *ac)
 265 {
 266         _enter("%hu+%hd", ac->start, (short)ac->index);
 267
 268         if (!ac->alist)
 269                 return false;
 270
 271         if (ac->begun) {
 272                 ac->index++;
 273                 if (ac->index == ac->alist->nr_addrs)
 274                         ac->index = 0;
 275
 276                 if (ac->index == ac->start) {
 277                         ac->error = -EDESTADDRREQ;
 278                         return false;
 279                 }
 280         }
 281
 282         ac->begun = true;
 283         ac->responded = false;
 284         ac->addr = &ac->alist->addrs[ac->index];
 285         return true;
 286 }
 287
 288 /*
 289  * Release an address list cursor.
 290  */
 291 int afs_end_cursor(struct afs_addr_cursor *ac)
 292 {
 293         if (ac->responded && ac->index != ac->start)
 294                 WRITE_ONCE(ac->alist->index, ac->index);
 295
 296         afs_put_addrlist(ac->alist);
 297         ac->alist = NULL;
 298         return ac->error;
 299 }
 300
 301 /*
 302  * Set the address cursor for iterating over VL servers.
 303  */
 304 int afs_set_vl_cursor(struct afs_addr_cursor *ac, struct afs_cell *cell)
 305 {
 306         struct afs_addr_list *alist;
 307         int ret;
 308
 309         if (!rcu_access_pointer(cell->vl_addrs)) {
 310                 ret = wait_on_bit(&cell->flags, AFS_CELL_FL_NO_LOOKUP_YET,
 311                                   TASK_INTERRUPTIBLE);
 312                 if (ret < 0)
 313                         return ret;
 314
 315                 if (!rcu_access_pointer(cell->vl_addrs) &&
 316                     ktime_get_real_seconds() < cell->dns_expiry)
 317                         return cell->error;
 318         }
 319
 320         read_lock(&cell->vl_addrs_lock);
 321         alist = rcu_dereference_protected(cell->vl_addrs,
 322                                           lockdep_is_held(&cell->vl_addrs_lock));
 323         if (alist->nr_addrs > 0)
 324                 afs_get_addrlist(alist);
 325         else
 326                 alist = NULL;
 327         read_unlock(&cell->vl_addrs_lock);
 328
 329         if (!alist)
 330                 return -EDESTADDRREQ;
 331
 332         ac->alist = alist;
 333         ac->addr = NULL;
 334         ac->start = READ_ONCE(alist->index);
 335         ac->index = ac->start;
 336         ac->error = 0;
 337         ac->begun = false;
 338         return 0;
 339 }