package/network/services/dnsmasq/patches/0046-Add-shared-network-DHCP-configuration.patch

   1 From ae5b7e04a1025167f1b80840e61432a3cea9625c Mon Sep 17 00:00:00 2001
   2 From: Simon Kelley <simon@thekelleys.org.uk>
   3 Date: Wed, 27 Mar 2019 22:33:28 +0000
   4 Subject: [PATCH 46/57] Add --shared-network DHCP configuration.
   5
   6 Signed-off-by: Kevin Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk>
   7 ---
   8  CHANGELOG     |   5 ++
   9  man/dnsmasq.8 |  21 ++++++
  10  src/dhcp.c    |  76 ++++++++++++++++++----
  11  src/dhcp6.c   | 175 ++++++++++++++++++++++++++++----------------------
  12  src/dnsmasq.h |  11 ++++
  13  src/option.c  |  41 ++++++++++++
  14  src/rfc2131.c |  97 +++++++++++++++++-----------
  15  src/rfc3315.c |  40 +++++++++---
  16  8 files changed, 332 insertions(+), 134 deletions(-)
  17
  18 --- a/CHANGELOG
  19 +++ b/CHANGELOG
  20 @@ -34,6 +34,11 @@ version 2.81
  21         tries not to request capabilities not required by its
  22         configuration.
  23
  24 +       Add --shared-network config. This enables allocation of addresses
  25 +       the DHCP server in subnets where the server (or relay) doesn't
  26 +       have an interface on the network in that subnet. Many thanks to
  27 +       plank.de for sponsoring this feature.
  28 +
  29
  30  version 2.80
  31         Add support for RFC 4039 DHCP rapid commit. Thanks to Ashram Method
  32 --- a/man/dnsmasq.8
  33 +++ b/man/dnsmasq.8
  34 @@ -1741,6 +1741,27 @@ It is permissible to add more than one a
  35  \fB--bridge-interface=int1,alias1,alias2\fP is exactly equivalent to
  36  \fB--bridge-interface=int1,alias1 --bridge-interface=int1,alias2\fP
  37  .TP
  38 +.B --shared-network=<interface>|<addr>,<addr>
  39 +The DHCP server determines which dhcp ranges are useable for allocating and
  40 +address to a DHCP client based on the network from which the DHCP request arrives,
  41 +and the IP configuration of the server's interface on that network. The shared-network
  42 +option extends the available subnets (and therefore dhcp ranges) beyond the
  43 +subnets configured on the arrival interface. The first argument is either the
  44 +name of an interface or an address which is configured on a local interface, and the
  45 +second argument is an address which defines another subnet on which addresses can be allocated.
  46 +To be useful, there must be suitable dhcp-range which allows address allocation on this subnet
  47 +and this dhcp-range MUST include the netmask. Use shared-network also needs extra
  48 +consideration of routing. Dnsmasq doesn't have the usual information which it uses to
  49 +determine the default route, so the default route option (or other routing) MUST be
  50 +manually configured. The client must have a route to the server: if the two-address form
  51 +of shared-network is used, this will be to the first specified address. If the interface,address
  52 +form is used, there must be a route to all of the addresses configured on the interface.
  53 +
  54 +The two-address form of shared-network is also usable with a DHCP relay: the first address
  55 +is the address of the relay and the second, as before, specifies an extra subnet which
  56 +may be allocated.
  57 +
  58 +.TP
  59  .B \-s, --domain=<domain>[,<address range>[,local]]
  60  Specifies DNS domains for the DHCP server. Domains may be be given
  61  unconditionally (without the IP range) or for limited IP ranges. This has two effects;
  62 --- a/src/dhcp.c
  63 +++ b/src/dhcp.c
  64 @@ -507,33 +507,83 @@ static int check_listen_addrs(struct in_
  65
  66     Note that the current chain may be superseded later for configured hosts or those coming via gateways. */
  67
  68 -static int complete_context(struct in_addr local, int if_index, char *label,
  69 -                           struct in_addr netmask, struct in_addr broadcast, void *vparam)
  70 +static void guess_range_netmask(struct in_addr addr, struct in_addr netmask)
  71  {
  72    struct dhcp_context *context;
  73 -  struct dhcp_relay *relay;
  74 -  struct iface_param *param = vparam;
  75
  76 -  (void)label;
  77 -
  78    for (context = daemon->dhcp; context; context = context->next)
  79 -    {
  80 -      if (!(context->flags & CONTEXT_NETMASK) &&
  81 -         (is_same_net(local, context->start, netmask) ||
  82 -          is_same_net(local, context->end, netmask)))
  83 +    if (!(context->flags & CONTEXT_NETMASK) &&
  84 +       (is_same_net(addr, context->start, netmask) ||
  85 +        is_same_net(addr, context->end, netmask)))
  86        {
  87         if (context->netmask.s_addr != netmask.s_addr &&
  88 -           !(is_same_net(local, context->start, netmask) &&
  89 -             is_same_net(local, context->end, netmask)))
  90 +           !(is_same_net(addr, context->start, netmask) &&
  91 +             is_same_net(addr, context->end, netmask)))
  92           {
  93             strcpy(daemon->dhcp_buff, inet_ntoa(context->start));
  94             strcpy(daemon->dhcp_buff2, inet_ntoa(context->end));
  95             my_syslog(MS_DHCP | LOG_WARNING, _("DHCP range %s -- %s is not consistent with netmask %s"),
  96                       daemon->dhcp_buff, daemon->dhcp_buff2, inet_ntoa(netmask));
  97           }
  98 -       context->netmask = netmask;
  99 +       context->netmask = netmask;
 100        }
 101 +}
 102 +
 103 +static int complete_context(struct in_addr local, int if_index, char *label,
 104 +                           struct in_addr netmask, struct in_addr broadcast, void *vparam)
 105 +{
 106 +  struct dhcp_context *context;
 107 +  struct dhcp_relay *relay;
 108 +  struct iface_param *param = vparam;
 109 +  struct shared_network *share;
 110 +
 111 +  (void)label;
 112 +
 113 +  for (share = daemon->shared_networks; share; share = share->next)
 114 +    {
 115
 116 +#ifdef HAVE_DHCP6
 117 +      if (share->shared_addr.s_addr == 0)
 118 +       continue;
 119 +#endif
 120 +
 121 +      if (share->if_index != 0)
 122 +       {
 123 +         if (share->if_index != if_index)
 124 +           continue;
 125 +       }
 126 +      else
 127 +       {
 128 +         if (share->match_addr.s_addr != local.s_addr)
 129 +           continue;
 130 +       }
 131 +
 132 +      for (context = daemon->dhcp; context; context = context->next)
 133 +       {
 134 +         if (context->netmask.s_addr != 0 &&
 135 +             is_same_net(share->shared_addr, context->start, context->netmask) &&
 136 +             is_same_net(share->shared_addr, context->end, context->netmask))
 137 +           {
 138 +             /* link it onto the current chain if we've not seen it before */
 139 +             if (context->current == context)
 140 +               {
 141 +                 /* For a shared network, we have no way to guess what the default route should be. */
 142 +                 context->router.s_addr = 0;
 143 +                 context->local = local; /* Use configured address for Server Identifier */
 144 +                 context->current = param->current;
 145 +                 param->current = context;
 146 +               }
 147 +
 148 +             if (!(context->flags & CONTEXT_BRDCAST))
 149 +               context->broadcast.s_addr  = context->start.s_addr | ~context->netmask.s_addr;
 150 +           }
 151 +       }
 152 +    }
 153 +
 154 +  guess_range_netmask(local, netmask);
 155 +
 156 +  for (context = daemon->dhcp; context; context = context->next)
 157 +    {
 158        if (context->netmask.s_addr != 0 &&
 159           is_same_net(local, context->start, context->netmask) &&
 160           is_same_net(local, context->end, context->netmask))
 161 --- a/src/dhcp6.c
 162 +++ b/src/dhcp6.c
 163 @@ -299,89 +299,114 @@ static int complete_context6(struct in6_
 164                              unsigned int valid, void *vparam)
 165  {
 166    struct dhcp_context *context;
 167 +  struct shared_network *share;
 168    struct dhcp_relay *relay;
 169    struct iface_param *param = vparam;
 170    struct iname *tmp;
 171
 172    (void)scope; /* warning */
 173
 174 -  if (if_index == param->ind)
 175 -    {
 176 -      if (IN6_IS_ADDR_LINKLOCAL(local))
 177 -       param->ll_addr = *local;
 178 -      else if (IN6_IS_ADDR_ULA(local))
 179 -       param->ula_addr = *local;
 180 -
 181 -      if (!IN6_IS_ADDR_LOOPBACK(local) &&
 182 -         !IN6_IS_ADDR_LINKLOCAL(local) &&
 183 -         !IN6_IS_ADDR_MULTICAST(local))
 184 -       {
 185 -         /* if we have --listen-address config, see if the
 186 -            arrival interface has a matching address. */
 187 -         for (tmp = daemon->if_addrs; tmp; tmp = tmp->next)
 188 -           if (tmp->addr.sa.sa_family == AF_INET6 &&
 189 -               IN6_ARE_ADDR_EQUAL(&tmp->addr.in6.sin6_addr, local))
 190 -             param->addr_match = 1;
 191 -
 192 -         /* Determine a globally address on the arrival interface, even
 193 -            if we have no matching dhcp-context, because we're only
 194 -            allocating on remote subnets via relays. This
 195 -            is used as a default for the DNS server option. */
 196 -         param->fallback = *local;
 197 -
 198 -         for (context = daemon->dhcp6; context; context = context->next)
 199 -           {
 200 -             if ((context->flags & CONTEXT_DHCP) &&
 201 -                 !(context->flags & (CONTEXT_TEMPLATE | CONTEXT_OLD)) &&
 202 -                 prefix <= context->prefix &&
 203 -                 is_same_net6(local, &context->start6, context->prefix) &&
 204 -                 is_same_net6(local, &context->end6, context->prefix))
 205 -               {
 206 -
 207 -
 208 -                 /* link it onto the current chain if we've not seen it before */
 209 -                 if (context->current == context)
 210 -                   {
 211 -                     struct dhcp_context *tmp, **up;
 212 -
 213 -                     /* use interface values only for constructed contexts */
 214 -                     if (!(context->flags & CONTEXT_CONSTRUCTED))
 215 -                       preferred = valid = 0xffffffff;
 216 -                     else if (flags & IFACE_DEPRECATED)
 217 -                       preferred = 0;
 218 -
 219 -                     if (context->flags & CONTEXT_DEPRECATE)
 220 -                       preferred = 0;
 221 -
 222 -                     /* order chain, longest preferred time first */
 223 -                     for (up = &param->current, tmp = param->current; tmp; tmp = tmp->current)
 224 -                       if (tmp->preferred <= preferred)
 225 -                         break;
 226 -                       else
 227 -                         up = &tmp->current;
 228 -
 229 -                     context->current = *up;
 230 -                     *up = context;
 231 -                     context->local6 = *local;
 232 -                     context->preferred = preferred;
 233 -                     context->valid = valid;
 234 -                   }
 235 -               }
 236 -           }
 237 -       }
 238 -
 239 -      for (relay = daemon->relay6; relay; relay = relay->next)
 240 -       if (IN6_ARE_ADDR_EQUAL(local, &relay->local.addr6) && relay->current == relay &&
 241 -           (IN6_IS_ADDR_UNSPECIFIED(&param->relay_local) || IN6_ARE_ADDR_EQUAL(local, &param->relay_local)))
 242 +  if (if_index != param->ind)
 243 +    return 1;
 244 +
 245 +  if (IN6_IS_ADDR_LINKLOCAL(local))
 246 +    param->ll_addr = *local;
 247 +  else if (IN6_IS_ADDR_ULA(local))
 248 +    param->ula_addr = *local;
 249 +
 250 +  if (IN6_IS_ADDR_LOOPBACK(local) ||
 251 +      IN6_IS_ADDR_LINKLOCAL(local) ||
 252 +      IN6_IS_ADDR_MULTICAST(local))
 253 +    return 1;
 254 +
 255 +  /* if we have --listen-address config, see if the
 256 +     arrival interface has a matching address. */
 257 +  for (tmp = daemon->if_addrs; tmp; tmp = tmp->next)
 258 +    if (tmp->addr.sa.sa_family == AF_INET6 &&
 259 +       IN6_ARE_ADDR_EQUAL(&tmp->addr.in6.sin6_addr, local))
 260 +      param->addr_match = 1;
 261 +
 262 +  /* Determine a globally address on the arrival interface, even
 263 +     if we have no matching dhcp-context, because we're only
 264 +     allocating on remote subnets via relays. This
 265 +     is used as a default for the DNS server option. */
 266 +  param->fallback = *local;
 267 +
 268 +  for (context = daemon->dhcp6; context; context = context->next)
 269 +    if ((context->flags & CONTEXT_DHCP) &&
 270 +       !(context->flags & (CONTEXT_TEMPLATE | CONTEXT_OLD)) &&
 271 +       prefix <= context->prefix &&
 272 +       context->current == context)
 273 +      {
 274 +       if (is_same_net6(local, &context->start6, context->prefix) &&
 275 +           is_same_net6(local, &context->end6, context->prefix))
 276           {
 277 -           relay->current = param->relay;
 278 -           param->relay = relay;
 279 -           param->relay_local = *local;
 280 +           struct dhcp_context *tmp, **up;
 281 +
 282 +           /* use interface values only for constructed contexts */
 283 +           if (!(context->flags & CONTEXT_CONSTRUCTED))
 284 +             preferred = valid = 0xffffffff;
 285 +           else if (flags & IFACE_DEPRECATED)
 286 +             preferred = 0;
 287 +
 288 +           if (context->flags & CONTEXT_DEPRECATE)
 289 +             preferred = 0;
 290 +
 291 +           /* order chain, longest preferred time first */
 292 +           for (up = &param->current, tmp = param->current; tmp; tmp = tmp->current)
 293 +             if (tmp->preferred <= preferred)
 294 +               break;
 295 +             else
 296 +               up = &tmp->current;
 297 +
 298 +           context->current = *up;
 299 +           *up = context;
 300 +           context->local6 = *local;
 301 +           context->preferred = preferred;
 302 +           context->valid = valid;
 303           }
 304 -
 305 -    }
 306 -
 307 - return 1;
 308 +       else
 309 +         {
 310 +           for (share = daemon->shared_networks; share; share = share->next)
 311 +             {
 312 +               /* IPv4 shared_address - ignore */
 313 +               if (share->shared_addr.s_addr != 0)
 314 +                 continue;
 315 +
 316 +               if (share->if_index != 0)
 317 +                 {
 318 +                   if (share->if_index != if_index)
 319 +                     continue;
 320 +                 }
 321 +               else
 322 +                 {
 323 +                   if (!IN6_ARE_ADDR_EQUAL(&share->match_addr6, local))
 324 +                     continue;
 325 +                 }
 326 +
 327 +               if (is_same_net6(&share->shared_addr6, &context->start6, context->prefix) &&
 328 +                   is_same_net6(&share->shared_addr6, &context->end6, context->prefix))
 329 +                 {
 330 +                   context->current = param->current;
 331 +                   param->current = context;
 332 +                   context->local6 = *local;
 333 +                   context->preferred = context->flags & CONTEXT_DEPRECATE ? 0 :0xffffffff;
 334 +                   context->valid = 0xffffffff;
 335 +                 }
 336 +             }
 337 +         }
 338 +      }
 339 +
 340 +  for (relay = daemon->relay6; relay; relay = relay->next)
 341 +    if (IN6_ARE_ADDR_EQUAL(local, &relay->local.addr6) && relay->current == relay &&
 342 +       (IN6_IS_ADDR_UNSPECIFIED(&param->relay_local) || IN6_ARE_ADDR_EQUAL(local, &param->relay_local)))
 343 +      {
 344 +       relay->current = param->relay;
 345 +       param->relay = relay;
 346 +       param->relay_local = *local;
 347 +      }
 348 +
 349 +  return 1;
 350  }
 351
 352  struct dhcp_config *config_find_by_address6(struct dhcp_config *configs, struct in6_addr *net, int prefix, u64 addr)
 353 --- a/src/dnsmasq.h
 354 +++ b/src/dnsmasq.h
 355 @@ -910,6 +910,16 @@ struct dhcp_context {
 356    struct dhcp_context *next, *current;
 357  };
 358
 359 +struct shared_network {
 360 +  int if_index;
 361 +  struct in_addr match_addr, shared_addr;
 362 +#ifdef HAVE_DHCP6
 363 +  /* shared_addr == 0 for IP6 entries. */
 364 +  struct in6_addr match_addr6, shared_addr6;
 365 +#endif
 366 +  struct shared_network *next;
 367 +};
 368 +
 369  #define CONTEXT_STATIC         (1u<<0)
 370  #define CONTEXT_NETMASK        (1u<<1)
 371  #define CONTEXT_BRDCAST        (1u<<2)
 372 @@ -1107,6 +1117,7 @@ extern struct daemon {
 373    struct ping_result *ping_results;
 374    FILE *lease_stream;
 375    struct dhcp_bridge *bridges;
 376 +  struct shared_network *shared_networks;
 377  #ifdef HAVE_DHCP6
 378    int duid_len;
 379    unsigned char *duid;
 380 --- a/src/option.c
 381 +++ b/src/option.c
 382 @@ -166,6 +166,7 @@ struct myoption {
 383  #define LOPT_UBUS          354
 384  #define LOPT_NAME_MATCH    355
 385  #define LOPT_CAA           356
 386 +#define LOPT_SHARED_NET    357
 387
 388  #ifdef HAVE_GETOPT_LONG
 389  static const struct option opts[] =
 390 @@ -259,6 +260,7 @@ static const struct myoption opts[] =
 391      { "ptr-record", 1, 0, LOPT_PTR },
 392      { "naptr-record", 1, 0, LOPT_NAPTR },
 393      { "bridge-interface", 1, 0 , LOPT_BRIDGE },
 394 +    { "shared-network", 1, 0, LOPT_SHARED_NET },
 395      { "dhcp-option-force", 1, 0, LOPT_FORCE },
 396      { "tftp-no-blocksize", 0, 0, LOPT_NOBLOCK },
 397      { "log-dhcp", 0, 0, LOPT_LOG_OPTS },
 398 @@ -431,6 +433,7 @@ static struct {
 399    { '3', ARG_DUP, "[=tag:<tag>]...", gettext_noop("Enable dynamic address allocation for bootp."), NULL },
 400    { '4', ARG_DUP, "set:<tag>,<mac address>", gettext_noop("Map MAC address (with wildcards) to option set."), NULL },
 401    { LOPT_BRIDGE, ARG_DUP, "<iface>,<alias>..", gettext_noop("Treat DHCP requests on aliases as arriving from interface."), NULL },
 402 +  { LOPT_SHARED_NET, ARG_DUP, "<iface>|<addr>,<addr>", gettext_noop("Specify extra networks sharing a broadcast domain for DHCP"), NULL},
 403    { '5', OPT_NO_PING, NULL, gettext_noop("Disable ICMP echo address checking in the DHCP server."), NULL },
 404    { '6', ARG_ONE, "<path>", gettext_noop("Shell script to run on DHCP lease creation and destruction."), NULL },
 405    { LOPT_LUASCRIPT, ARG_DUP, "path", gettext_noop("Lua script to run on DHCP lease creation and destruction."), NULL },
 406 @@ -2873,6 +2876,44 @@ static int one_opt(int option, char *arg
 407        }
 408
 409  #ifdef HAVE_DHCP
 410 +    case LOPT_SHARED_NET: /* --shared-network */
 411 +      {
 412 +       struct shared_network *new = opt_malloc(sizeof(struct shared_network));
 413 +
 414 +#ifdef HAVE_DHCP6
 415 +       new->shared_addr.s_addr = 0;
 416 +#endif
 417 +       new->if_index = 0;
 418 +
 419 +       if (!(comma = split(arg)))
 420 +         {
 421 +         snerr:
 422 +           free(new);
 423 +           ret_err(_("bad shared-network"));
 424 +         }
 425 +
 426 +       if (inet_pton(AF_INET, comma, &new->shared_addr))
 427 +         {
 428 +           if (!inet_pton(AF_INET, arg, &new->match_addr) &&
 429 +               !(new->if_index = if_nametoindex(arg)))
 430 +             goto snerr;
 431 +         }
 432 +#ifdef HAVE_DHCP6
 433 +       else if (inet_pton(AF_INET6, comma, &new->shared_addr6))
 434 +         {
 435 +           if (!inet_pton(AF_INET6, arg, &new->match_addr6) &&
 436 +               !(new->if_index = if_nametoindex(arg)))
 437 +             goto snerr;
 438 +         }
 439 +#endif
 440 +       else
 441 +         goto snerr;
 442 +
 443 +       new->next = daemon->shared_networks;
 444 +       daemon->shared_networks = new;
 445 +       break;
 446 +      }
 447 +
 448      case 'F':  /* --dhcp-range */
 449        {
 450         int k, leasepos = 2;
 451 --- a/src/rfc2131.c
 452 +++ b/src/rfc2131.c
 453 @@ -274,8 +274,9 @@ size_t dhcp_reply(struct dhcp_context *c
 454    if (mess->giaddr.s_addr || subnet_addr.s_addr || mess->ciaddr.s_addr)
 455      {
 456        struct dhcp_context *context_tmp, *context_new = NULL;
 457 +      struct shared_network *share = NULL;
 458        struct in_addr addr;
 459 -      int force = 0;
 460 +      int force = 0, via_relay = 0;
 461
 462        if (subnet_addr.s_addr)
 463         {
 464 @@ -286,6 +287,7 @@ size_t dhcp_reply(struct dhcp_context *c
 465         {
 466           addr = mess->giaddr;
 467           force = 1;
 468 +         via_relay = 1;
 469         }
 470        else
 471         {
 472 @@ -302,42 +304,65 @@ size_t dhcp_reply(struct dhcp_context *c
 473         }
 474
 475        if (!context_new)
 476 -       for (context_tmp = daemon->dhcp; context_tmp; context_tmp = context_tmp->next)
 477 -         {
 478 -           struct in_addr netmask = context_tmp->netmask;
 479 +       {
 480 +         for (context_tmp = daemon->dhcp; context_tmp; context_tmp = context_tmp->next)
 481 +           {
 482 +             struct in_addr netmask = context_tmp->netmask;
 483 +
 484 +             /* guess the netmask for relayed networks */
 485 +             if (!(context_tmp->flags & CONTEXT_NETMASK) && context_tmp->netmask.s_addr == 0)
 486 +               {
 487 +                 if (IN_CLASSA(ntohl(context_tmp->start.s_addr)) && IN_CLASSA(ntohl(context_tmp->end.s_addr)))
 488 +                   netmask.s_addr = htonl(0xff000000);
 489 +                 else if (IN_CLASSB(ntohl(context_tmp->start.s_addr)) && IN_CLASSB(ntohl(context_tmp->end.s_addr)))
 490 +                   netmask.s_addr = htonl(0xffff0000);
 491 +                 else if (IN_CLASSC(ntohl(context_tmp->start.s_addr)) && IN_CLASSC(ntohl(context_tmp->end.s_addr)))
 492 +                   netmask.s_addr = htonl(0xffffff00);
 493 +               }
 494
 495 -           /* guess the netmask for relayed networks */
 496 -           if (!(context_tmp->flags & CONTEXT_NETMASK) && context_tmp->netmask.s_addr == 0)
 497 -             {
 498 -               if (IN_CLASSA(ntohl(context_tmp->start.s_addr)) && IN_CLASSA(ntohl(context_tmp->end.s_addr)))
 499 -                 netmask.s_addr = htonl(0xff000000);
 500 -               else if (IN_CLASSB(ntohl(context_tmp->start.s_addr)) && IN_CLASSB(ntohl(context_tmp->end.s_addr)))
 501 -                 netmask.s_addr = htonl(0xffff0000);
 502 -               else if (IN_CLASSC(ntohl(context_tmp->start.s_addr)) && IN_CLASSC(ntohl(context_tmp->end.s_addr)))
 503 -                 netmask.s_addr = htonl(0xffffff00);
 504 -             }
 505 -
 506 -           /* This section fills in context mainly when a client which is on a remote (relayed)
 507 -              network renews a lease without using the relay, after dnsmasq has restarted. */
 508 -           if (netmask.s_addr != 0  &&
 509 -               is_same_net(addr, context_tmp->start, netmask) &&
 510 -               is_same_net(addr, context_tmp->end, netmask))
 511 -             {
 512 -               context_tmp->netmask = netmask;
 513 -               if (context_tmp->local.s_addr == 0)
 514 -                 context_tmp->local = fallback;
 515 -               if (context_tmp->router.s_addr == 0)
 516 -                 context_tmp->router = mess->giaddr;
 517 -
 518 -               /* fill in missing broadcast addresses for relayed ranges */
 519 -               if (!(context_tmp->flags & CONTEXT_BRDCAST) && context_tmp->broadcast.s_addr == 0 )
 520 -                 context_tmp->broadcast.s_addr = context_tmp->start.s_addr | ~context_tmp->netmask.s_addr;
 521 -
 522 -               context_tmp->current = context_new;
 523 -               context_new = context_tmp;
 524 -             }
 525 -         }
 526 -
 527 +             /* check to see is a context is OK because of a shared address on
 528 +                the relayed subnet. */
 529 +             if (via_relay)
 530 +               for (share = daemon->shared_networks; share; share = share->next)
 531 +                 {
 532 +#ifdef HAVE_DHCP6
 533 +                   if (share->shared_addr.s_addr == 0)
 534 +                     continue;
 535 +#endif
 536 +                   if (share->if_index != 0 ||
 537 +                       share->match_addr.s_addr != mess->giaddr.s_addr)
 538 +                     continue;
 539 +
 540 +                   if (netmask.s_addr != 0  &&
 541 +                       is_same_net(share->shared_addr, context_tmp->start, netmask) &&
 542 +                       is_same_net(share->shared_addr, context_tmp->end, netmask))
 543 +                     break;
 544 +                 }
 545 +
 546 +             /* This section fills in context mainly when a client which is on a remote (relayed)
 547 +                network renews a lease without using the relay, after dnsmasq has restarted. */
 548 +             if (share ||
 549 +                 (netmask.s_addr != 0  &&
 550 +                  is_same_net(addr, context_tmp->start, netmask) &&
 551 +                  is_same_net(addr, context_tmp->end, netmask)))
 552 +               {
 553 +                 context_tmp->netmask = netmask;
 554 +                 if (context_tmp->local.s_addr == 0)
 555 +                   context_tmp->local = fallback;
 556 +                 if (context_tmp->router.s_addr == 0 && !share)
 557 +                   context_tmp->router = mess->giaddr;
 558 +
 559 +                 /* fill in missing broadcast addresses for relayed ranges */
 560 +                 if (!(context_tmp->flags & CONTEXT_BRDCAST) && context_tmp->broadcast.s_addr == 0 )
 561 +                   context_tmp->broadcast.s_addr = context_tmp->start.s_addr | ~context_tmp->netmask.s_addr;
 562 +
 563 +                 context_tmp->current = context_new;
 564 +                 context_new = context_tmp;
 565 +               }
 566 +
 567 +           }
 568 +       }
 569 +
 570        if (context_new || force)
 571         context = context_new;
 572      }
 573 --- a/src/rfc3315.c
 574 +++ b/src/rfc3315.c
 575 @@ -134,21 +134,41 @@ static int dhcp6_maybe_relay(struct stat
 576        else
 577         {
 578           struct dhcp_context *c;
 579 +         struct shared_network *share = NULL;
 580           state->context = NULL;
 581 -
 582 +
 583           if (!IN6_IS_ADDR_LOOPBACK(state->link_address) &&
 584               !IN6_IS_ADDR_LINKLOCAL(state->link_address) &&
 585               !IN6_IS_ADDR_MULTICAST(state->link_address))
 586             for (c = daemon->dhcp6; c; c = c->next)
 587 -             if ((c->flags & CONTEXT_DHCP) &&
 588 -                 !(c->flags & (CONTEXT_TEMPLATE | CONTEXT_OLD)) &&
 589 -                 is_same_net6(state->link_address, &c->start6, c->prefix) &&
 590 -                 is_same_net6(state->link_address, &c->end6, c->prefix))
 591 -               {
 592 -                 c->preferred = c->valid = 0xffffffff;
 593 -                 c->current = state->context;
 594 -                 state->context = c;
 595 -               }
 596 +             {
 597 +               for (share = daemon->shared_networks; share; share = share->next)
 598 +                 {
 599 +                   if (share->shared_addr.s_addr != 0)
 600 +                     continue;
 601 +
 602 +                   if (share->if_index != 0 ||
 603 +                       !IN6_ARE_ADDR_EQUAL(state->link_address, &share->match_addr6))
 604 +                     continue;
 605 +
 606 +                   if ((c->flags & CONTEXT_DHCP) &&
 607 +                       !(c->flags & (CONTEXT_TEMPLATE | CONTEXT_OLD)) &&
 608 +                       is_same_net6(&share->shared_addr6, &c->start6, c->prefix) &&
 609 +                       is_same_net6(&share->shared_addr6, &c->end6, c->prefix))
 610 +                     break;
 611 +                 }
 612 +
 613 +               if (share ||
 614 +                   ((c->flags & CONTEXT_DHCP) &&
 615 +                    !(c->flags & (CONTEXT_TEMPLATE | CONTEXT_OLD)) &&
 616 +                    is_same_net6(state->link_address, &c->start6, c->prefix) &&
 617 +                    is_same_net6(state->link_address, &c->end6, c->prefix)))
 618 +                 {
 619 +                   c->preferred = c->valid = 0xffffffff;
 620 +                   c->current = state->context;
 621 +                   state->context = c;
 622 +                 }
 623 +             }
 624
 625           if (!state->context)
 626             {