/* dnsmasq is Copyright (c) 2000-2025 Simon Kelley

   This program is free software; you can redistribute it and/or modify

   it under the terms of the GNU General Public License as published by

   the Free Software Foundation; version 2 dated June, 1991, or

   (at your option) version 3 dated 29 June, 2007.

   This program is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License

   along with this program.  If not, see <http://www.gnu.org/licenses/>.

*/

#include "dnsmasq.h"

#ifdef HAVE_DHCP

struct iface_param {

  struct dhcp_context *current;

  int ind;

};

struct match_param {

  int ind, matched;

  struct in_addr netmask, broadcast, addr;

};

static int complete_context(struct in_addr local, int if_index, char *label,

          struct in_addr netmask, struct in_addr broadcast, void *vparam);

static int check_listen_addrs(struct in_addr local, int if_index, char *label,

            struct in_addr netmask, struct in_addr broadcast, void *vparam);

static void relay_upstream4(int iface_index, struct dhcp_packet *mess, size_t sz);

static struct dhcp_relay *relay_reply4(struct dhcp_packet *mess, char *arrival_interface);

static int make_fd(int port)

{

  int fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);

  struct sockaddr_in saddr;

  int oneopt = 1;

#if defined(IP_MTU_DISCOVER) && defined(IP_PMTUDISC_DONT)

  int mtu = IP_PMTUDISC_DONT;

#endif

#if defined(IP_TOS) && defined(IPTOS_CLASS_CS6)

  int tos = IPTOS_CLASS_CS6;

#endif

  if (fd == -1)

    die (_("cannot create DHCP socket: %s"), NULL, EC_BADNET);

  if (!fix_fd(fd) ||

#if defined(IP_MTU_DISCOVER) && defined(IP_PMTUDISC_DONT)

      setsockopt(fd, IPPROTO_IP, IP_MTU_DISCOVER, &mtu, sizeof(mtu)) == -1 ||

#endif

#if defined(IP_TOS) && defined(IPTOS_CLASS_CS6)

      setsockopt(fd, IPPROTO_IP, IP_TOS, &tos, sizeof(tos)) == -1 ||

#endif

#if defined(HAVE_LINUX_NETWORK)

      setsockopt(fd, IPPROTO_IP, IP_PKTINFO, &oneopt, sizeof(oneopt)) == -1 ||

#else

      setsockopt(fd, IPPROTO_IP, IP_RECVIF, &oneopt, sizeof(oneopt)) == -1 ||

#endif

      setsockopt(fd, SOL_SOCKET, SO_BROADCAST, &oneopt, sizeof(oneopt)) == -1)  

    die(_("failed to set options on DHCP socket: %s"), NULL, EC_BADNET);

  /* When bind-interfaces is set, there might be more than one dnsmasq

     instance binding port 67. That's OK if they serve different networks.

     Need to set REUSEADDR|REUSEPORT to make this possible.

     Handle the case that REUSEPORT is defined, but the kernel doesn't 

     support it. This handles the introduction of REUSEPORT on Linux. */

  if (option_bool(OPT_NOWILD) || option_bool(OPT_CLEVERBIND))

    {

      int rc = 0;

#ifdef SO_REUSEPORT

      if ((rc = setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &oneopt, sizeof(oneopt))) == -1 && 

    errno == ENOPROTOOPT)

  rc = 0;

#endif

      if (rc != -1)

  rc = setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &oneopt, sizeof(oneopt));

      if (rc == -1)

  die(_("failed to set SO_REUSE{ADDR|PORT} on DHCP socket: %s"), NULL, EC_BADNET);

    }

  memset(&saddr, 0, sizeof(saddr));

  saddr.sin_family = AF_INET;

  saddr.sin_port = htons(port);

  saddr.sin_addr.s_addr = INADDR_ANY;

#ifdef HAVE_SOCKADDR_SA_LEN

  saddr.sin_len = sizeof(struct sockaddr_in);

#endif

  if (bind(fd, (struct sockaddr *)&saddr, sizeof(struct sockaddr_in)))

    die(_("failed to bind DHCP server socket: %s"), NULL, EC_BADNET);

  return fd;

}

void dhcp_init(void)

{

#if defined(HAVE_BSD_NETWORK)

  int oneopt = 1;

#endif

  daemon->dhcpfd = make_fd(daemon->dhcp_server_port);

  if (daemon->enable_pxe)

    daemon->pxefd = make_fd(PXE_PORT);

  else

    daemon->pxefd = -1;

#if defined(HAVE_BSD_NETWORK)

  /* When we're not using capabilities, we need to do this here before

     we drop root. Also, set buffer size small, to avoid wasting

     kernel buffers */

  if (option_bool(OPT_NO_PING))

    daemon->dhcp_icmp_fd = -1;

  else if ((daemon->dhcp_icmp_fd = make_icmp_sock()) == -1 ||

     setsockopt(daemon->dhcp_icmp_fd, SOL_SOCKET, SO_RCVBUF, &oneopt, sizeof(oneopt)) == -1 )

    die(_("cannot create ICMP raw socket: %s."), NULL, EC_BADNET);

  /* Make BPF raw send socket */

  init_bpf();

#endif  

}

void dhcp_packet(time_t now, int pxe_fd)

{

  int fd = pxe_fd ? daemon->pxefd : daemon->dhcpfd;

  struct dhcp_packet *mess;

  struct dhcp_context *context;

  struct dhcp_relay *relay;

  int is_relay_reply = 0, is_relay_use_source = 0;

  struct iname *tmp;

  struct ifreq ifr;

  struct msghdr msg;

  struct sockaddr_in dest;

  struct cmsghdr *cmptr;

  struct iovec iov;

  ssize_t sz; 

  int iface_index = 0, unicast_dest = 0, is_inform = 0, loopback = 0;

  int rcvd_iface_index;

  struct in_addr iface_addr;

  struct iface_param parm;

  time_t recvtime = now;

#ifdef HAVE_LINUX_NETWORK

  struct arpreq arp_req;

  struct timeval tv;

#endif

  union {

    struct cmsghdr align; /* this ensures alignment */

#if defined(HAVE_LINUX_NETWORK)

    char control[CMSG_SPACE(sizeof(struct in_pktinfo))];

#elif defined(HAVE_SOLARIS_NETWORK)

    char control[CMSG_SPACE(sizeof(unsigned int))];

#elif defined(HAVE_BSD_NETWORK) 

    char control[CMSG_SPACE(sizeof(struct sockaddr_dl))];

#endif

  } control_u;

  struct dhcp_bridge *bridge, *alias;

  msg.msg_controllen = sizeof(control_u);

  msg.msg_control = control_u.control;

  msg.msg_name = &dest;

  msg.msg_namelen = sizeof(dest);

  msg.msg_iov = &daemon->dhcp_packet;

  msg.msg_iovlen = 1;

  if ((sz = recv_dhcp_packet(fd, &msg)) == -1 || 

      (sz < (ssize_t)(sizeof(*mess) - sizeof(mess->options)))) 

    return;

#ifdef HAVE_DUMPFILE

  dump_packet_udp(DUMP_DHCP, (void *)daemon->dhcp_packet.iov_base, sz, (union mysockaddr *)&dest, NULL, fd);

#endif

#if defined (HAVE_LINUX_NETWORK)

  if (ioctl(fd, SIOCGSTAMP, &tv) == 0)

    recvtime = tv.tv_sec;

  if (msg.msg_controllen >= sizeof(struct cmsghdr))

    for (cmptr = CMSG_FIRSTHDR(&msg); cmptr; cmptr = CMSG_NXTHDR(&msg, cmptr))

      if (cmptr->cmsg_level == IPPROTO_IP && cmptr->cmsg_type == IP_PKTINFO)

  {

    union {

      unsigned char *c;

      struct in_pktinfo *p;

    } p;

    p.c = CMSG_DATA(cmptr);

    iface_index = p.p->ipi_ifindex;

    if (p.p->ipi_addr.s_addr != INADDR_BROADCAST)

      unicast_dest = 1;

  }

#elif defined(HAVE_BSD_NETWORK) 

  if (msg.msg_controllen >= sizeof(struct cmsghdr))

    for (cmptr = CMSG_FIRSTHDR(&msg); cmptr; cmptr = CMSG_NXTHDR(&msg, cmptr))

      if (cmptr->cmsg_level == IPPROTO_IP && cmptr->cmsg_type == IP_RECVIF)

        {

    union {

            unsigned char *c;

            struct sockaddr_dl *s;

          } p;

    p.c = CMSG_DATA(cmptr);

    iface_index = p.s->sdl_index;

  }

#elif defined(HAVE_SOLARIS_NETWORK) 

  if (msg.msg_controllen >= sizeof(struct cmsghdr))

    for (cmptr = CMSG_FIRSTHDR(&msg); cmptr; cmptr = CMSG_NXTHDR(&msg, cmptr))

      if (cmptr->cmsg_level == IPPROTO_IP && cmptr->cmsg_type == IP_RECVIF)

  {

    union {

      unsigned char *c;

      unsigned int *i;

    } p;

    p.c = CMSG_DATA(cmptr);

    iface_index = *(p.i);

  }

#endif

  if (!indextoname(daemon->dhcpfd, iface_index, ifr.ifr_name) ||

      ioctl(daemon->dhcpfd, SIOCGIFFLAGS, &ifr) != 0)

    return;

  mess = (struct dhcp_packet *)daemon->dhcp_packet.iov_base;

  /* Non-standard extension:

     If giaddr == 255.255.255.255 we reply to the source

     address in the request packet header. This makes

     stand-alone leasequery clients easier, as they

     can leave source address determination to the kernel.

     In this case, set a flag and clear giaddr here,

     to avoid massive relay confusion. */

  if (mess->giaddr.s_addr == INADDR_BROADCAST)

    {

      mess->giaddr.s_addr = 0;

      is_relay_use_source = 1;

    }

  loopback = !mess->giaddr.s_addr && (ifr.ifr_flags & IFF_LOOPBACK);

#ifdef HAVE_LINUX_NETWORK

  /* ARP fiddling uses original interface even if we pretend to use a different one. */

  safe_strncpy(arp_req.arp_dev, ifr.ifr_name, sizeof(arp_req.arp_dev));

#endif 

  /* If the interface on which the DHCP request was received is an

     alias of some other interface (as specified by the

     --bridge-interface option), change ifr.ifr_name so that we look

     for DHCP contexts associated with the aliased interface instead

     of with the aliasing one. */

  rcvd_iface_index = iface_index;

  for (bridge = daemon->bridges; bridge; bridge = bridge->next)

    {

      for (alias = bridge->alias; alias; alias = alias->next)

  if (wildcard_matchn(alias->iface, ifr.ifr_name, IF_NAMESIZE))

    {

      if (!(iface_index = if_nametoindex(bridge->iface)))

        {

    my_syslog(MS_DHCP | LOG_WARNING,

        _("unknown interface %s in bridge-interface"),

        bridge->iface);

    return;

        }

      else 

        {

    safe_strncpy(ifr.ifr_name,  bridge->iface, sizeof(ifr.ifr_name));

    break;

        }

    }

      if (alias)

  break;

    }

#ifdef MSG_BCAST

  /* OpenBSD tells us when a packet was broadcast */

  if (!(msg.msg_flags & MSG_BCAST))

    unicast_dest = 1;

#endif

  if ((relay = relay_reply4((struct dhcp_packet *)daemon->dhcp_packet.iov_base, ifr.ifr_name)))

    {

      /* Reply from server, using us as relay. */

      rcvd_iface_index = relay->iface_index;

      if (!indextoname(daemon->dhcpfd, rcvd_iface_index, ifr.ifr_name))

  return;

      is_relay_reply = 1; 

      iov.iov_len = sz;

#ifdef HAVE_LINUX_NETWORK

      safe_strncpy(arp_req.arp_dev, ifr.ifr_name, sizeof(arp_req.arp_dev));

#endif 

    }

  else

    {

      ifr.ifr_addr.sa_family = AF_INET;

      if (ioctl(daemon->dhcpfd, SIOCGIFADDR, &ifr) != -1 )

  iface_addr = ((struct sockaddr_in *) &ifr.ifr_addr)->sin_addr;

      else

  {

    if (iface_check(AF_INET, NULL, ifr.ifr_name, NULL))

      my_syslog(MS_DHCP | LOG_WARNING, _("DHCP packet received on %s which has no address"), ifr.ifr_name);

    return;

  }

      for (tmp = daemon->dhcp_except; tmp; tmp = tmp->next)

  if (tmp->name && (tmp->flags & INAME_4) && wildcard_match(tmp->name, ifr.ifr_name))

    return;

      /* unlinked contexts/relays are marked by context->current == context */

      for (context = daemon->dhcp; context; context = context->next)

  context->current = context;

      parm.current = NULL;

      parm.ind = iface_index;

      if (!iface_check(AF_INET, (union all_addr *)&iface_addr, ifr.ifr_name, NULL))

  {

    /* If we failed to match the primary address of the interface, see if we've got a --listen-address

       for a secondary */

    struct match_param match;

    match.matched = 0;

    match.ind = iface_index;

    if (!daemon->if_addrs ||

        !iface_enumerate(AF_INET, &match, (callback_t){.af_inet=check_listen_addrs}) ||

        !match.matched)

      return;

    iface_addr = match.addr;

    /* make sure secondary address gets priority in case

       there is more than one address on the interface in the same subnet */

    complete_context(match.addr, iface_index, NULL, match.netmask, match.broadcast, &parm);

  }    

      if (!iface_enumerate(AF_INET, &parm, (callback_t){.af_inet=complete_context}))

  return;

      relay_upstream4(iface_index, mess, (size_t)sz);

      /* May have configured relay, but not DHCP server */

      if (!daemon->dhcp)

  return;

      lease_prune(NULL, now); /* lose any expired leases */

      iov.iov_len = dhcp_reply(parm.current, ifr.ifr_name, iface_index, (size_t)sz, now, unicast_dest,

             loopback, &is_inform, pxe_fd, iface_addr, recvtime,

             is_relay_use_source ? dest.sin_addr : mess->giaddr);

      lease_update_file(now);

      lease_update_dns(0);

      if (iov.iov_len == 0)

  return;

    }

  msg.msg_name = &dest;

  msg.msg_namelen = sizeof(dest);

  msg.msg_control = NULL;

  msg.msg_controllen = 0;

  msg.msg_iov = &iov;

  iov.iov_base = daemon->dhcp_packet.iov_base;

  /* packet buffer may have moved */

  mess = (struct dhcp_packet *)daemon->dhcp_packet.iov_base;

#ifdef HAVE_SOCKADDR_SA_LEN

  dest.sin_len = sizeof(struct sockaddr_in);

#endif

  if (pxe_fd)

    { 

      if (mess->ciaddr.s_addr != 0)

  dest.sin_addr = mess->ciaddr;

    }

  if ((is_relay_use_source || mess->giaddr.s_addr) && !is_relay_reply)

    {

      /* Send to BOOTP relay. */

      if (is_relay_use_source)

  /* restore as-received value */

  mess->giaddr.s_addr = INADDR_BROADCAST;

      else

  {

    dest.sin_addr = mess->giaddr;

    dest.sin_port = htons(daemon->dhcp_server_port);

  }

    }

  else if (mess->ciaddr.s_addr)

    {

      /* If the client's idea of its own address tallys with

   the source address in the request packet, we believe the

   source port too, and send back to that.  If we're replying 

   to a DHCPINFORM, trust the source address always. */

      if ((!is_inform && dest.sin_addr.s_addr != mess->ciaddr.s_addr) ||

    dest.sin_port == 0 || dest.sin_addr.s_addr == 0 || is_relay_reply)

  {

    dest.sin_port = htons(daemon->dhcp_client_port); 

    dest.sin_addr = mess->ciaddr;

  }

    } 

#if defined(HAVE_LINUX_NETWORK)

  else

    {

      /* fill cmsg for outbound interface (both broadcast & unicast) */

      struct in_pktinfo *pkt;

      msg.msg_control = control_u.control;

      msg.msg_controllen = sizeof(control_u);

      /* alignment padding passed to the kernel should not be uninitialised. */

      memset(&control_u, 0, sizeof(control_u));

      cmptr = CMSG_FIRSTHDR(&msg);

      pkt = (struct in_pktinfo *)CMSG_DATA(cmptr);

      pkt->ipi_ifindex = rcvd_iface_index;

      pkt->ipi_spec_dst.s_addr = 0;

      msg.msg_controllen = CMSG_SPACE(sizeof(struct in_pktinfo));

      cmptr->cmsg_len = CMSG_LEN(sizeof(struct in_pktinfo));

      cmptr->cmsg_level = IPPROTO_IP;

      cmptr->cmsg_type = IP_PKTINFO;

      if ((ntohs(mess->flags) & 0x8000) || mess->hlen == 0 ||

         mess->hlen > sizeof(ifr.ifr_addr.sa_data) || mess->htype == 0)

        {

          /* broadcast to 255.255.255.255 (or mac address invalid) */

          dest.sin_addr.s_addr = INADDR_BROADCAST;

          dest.sin_port = htons(daemon->dhcp_client_port);

        }

      else

        {

          /* unicast to unconfigured client. Inject mac address direct into ARP cache.

          struct sockaddr limits size to 14 bytes. */

          dest.sin_addr = mess->yiaddr;

          dest.sin_port = htons(daemon->dhcp_client_port);

          memcpy(&arp_req.arp_pa, &dest, sizeof(struct sockaddr_in));

          arp_req.arp_ha.sa_family = mess->htype;

          memcpy(arp_req.arp_ha.sa_data, mess->chaddr, mess->hlen);

          /* interface name already copied in */

          arp_req.arp_flags = ATF_COM;

          if (ioctl(daemon->dhcpfd, SIOCSARP, &arp_req) == -1)

            my_syslog(MS_DHCP | LOG_ERR, _("ARP-cache injection failed: %s"), strerror(errno));

        }

    }

#elif defined(HAVE_SOLARIS_NETWORK)

  else if ((ntohs(mess->flags) & 0x8000) || mess->hlen != ETHER_ADDR_LEN || mess->htype != ARPHRD_ETHER)

    {

      /* broadcast to 255.255.255.255 (or mac address invalid) */

      dest.sin_addr.s_addr = INADDR_BROADCAST;

      dest.sin_port = htons(daemon->dhcp_client_port);

      /* note that we don't specify the interface here: that's done by the

   IP_BOUND_IF sockopt lower down. */

    }

  else

    {

      /* unicast to unconfigured client. Inject mac address direct into ARP cache. 

   Note that this only works for ethernet on solaris, because we use SIOCSARP

   and not SIOCSXARP, which would be perfect, except that it returns ENXIO 

   mysteriously. Bah. Fall back to broadcast for other net types. */

      struct arpreq req;

      dest.sin_addr = mess->yiaddr;

      dest.sin_port = htons(daemon->dhcp_client_port);

      *((struct sockaddr_in *)&req.arp_pa) = dest;

      req.arp_ha.sa_family = AF_UNSPEC;

      memcpy(req.arp_ha.sa_data, mess->chaddr, mess->hlen);

      req.arp_flags = ATF_COM;

      ioctl(daemon->dhcpfd, SIOCSARP, &req);

    }

#elif defined(HAVE_BSD_NETWORK)

  else 

    {

#ifdef HAVE_DUMPFILE

      if (ntohs(mess->flags) & 0x8000)

        dest.sin_addr.s_addr = INADDR_BROADCAST;

      else

        dest.sin_addr = mess->yiaddr;

      dest.sin_port = htons(daemon->dhcp_client_port);

      dump_packet_udp(DUMP_DHCP, (void *)iov.iov_base, iov.iov_len, NULL,

          (union mysockaddr *)&dest, fd);

#endif

      send_via_bpf(mess, iov.iov_len, iface_addr, &ifr);

      return;

    }

#endif

#ifdef HAVE_SOLARIS_NETWORK

  setsockopt(fd, IPPROTO_IP, IP_BOUND_IF, &iface_index, sizeof(iface_index));

#endif

#ifdef HAVE_DUMPFILE

  dump_packet_udp(DUMP_DHCP, (void *)iov.iov_base, iov.iov_len, NULL,

      (union mysockaddr *)&dest, fd);

#endif

  while(retry_send(sendmsg(fd, &msg, 0)));

  /* This can fail when, eg, iptables DROPS destination 255.255.255.255 */

  if (errno != 0)

    {

      inet_ntop(AF_INET, &dest.sin_addr, daemon->addrbuff, ADDRSTRLEN);

      my_syslog(MS_DHCP | LOG_WARNING, _("Error sending DHCP packet to %s: %s"),

    daemon->addrbuff, strerror(errno));

    }

}

/* check against secondary interface addresses */

static int check_listen_addrs(struct in_addr local, int if_index, char *label,

            struct in_addr netmask, struct in_addr broadcast, void *vparam)

{

  struct match_param *param = vparam;

  struct iname *tmp;

  (void) label;

  if (if_index == param->ind)

    {

      for (tmp = daemon->if_addrs; tmp; tmp = tmp->next)

  if ( tmp->addr.sa.sa_family == AF_INET &&

       tmp->addr.in.sin_addr.s_addr == local.s_addr)

    {

      param->matched = 1;

      param->addr = local;

      param->netmask = netmask;

      param->broadcast = broadcast;

      break;

    }

    }

  return 1;

}

/* This is a complex routine: it gets called with each (address,netmask,broadcast) triple 

   of each interface (and any relay address) and does the  following things:

   1) Discards stuff for interfaces other than the one on which a DHCP packet just arrived.

   2) Fills in any netmask and broadcast addresses which have not been explicitly configured.

   3) Fills in local (this host) and router (this host or relay) addresses.

   4) Links contexts which are valid for hosts directly connected to the arrival interface on ->current.

   Note that the current chain may be superseded later for configured hosts or those coming via gateways. */

static void guess_range_netmask(struct in_addr addr, struct in_addr netmask)

{

  struct dhcp_context *context;

  for (context = daemon->dhcp; context; context = context->next)

    if (!(context->flags & CONTEXT_NETMASK) &&

  (is_same_net(addr, context->start, netmask) ||

   is_same_net(addr, context->end, netmask)))

      { 

  if (context->netmask.s_addr != netmask.s_addr &&

      !(is_same_net(addr, context->start, netmask) &&

        is_same_net(addr, context->end, netmask)))

    {

      inet_ntop(AF_INET, &context->start, daemon->dhcp_buff, DHCP_BUFF_SZ);

      inet_ntop(AF_INET, &context->end, daemon->dhcp_buff2, DHCP_BUFF_SZ);

      inet_ntop(AF_INET, &netmask, daemon->addrbuff, ADDRSTRLEN);

      my_syslog(MS_DHCP | LOG_WARNING, _("DHCP range %s -- %s is not consistent with netmask %s"),

          daemon->dhcp_buff, daemon->dhcp_buff2, daemon->addrbuff);

    } 

  context->netmask = netmask;

      }

}

static int complete_context(struct in_addr local, int if_index, char *label,

          struct in_addr netmask, struct in_addr broadcast, void *vparam)

{

  struct dhcp_context *context;

  struct dhcp_relay *relay;

  struct iface_param *param = vparam;

  struct shared_network *share;

  (void)label;

  for (share = daemon->shared_networks; share; share = share->next)

    {

#ifdef HAVE_DHCP6

      if (share->shared_addr.s_addr == 0)

  continue;

#endif

      if (share->if_index != 0)

  {

    if (share->if_index != if_index)

      continue;

  }

      else

  {

    if (share->match_addr.s_addr != local.s_addr)

      continue;

  }

      for (context = daemon->dhcp; context; context = context->next)

  {

    if (context->netmask.s_addr != 0 &&

        is_same_net(share->shared_addr, context->start, context->netmask) &&

        is_same_net(share->shared_addr, context->end, context->netmask))

      {

        /* link it onto the current chain if we've not seen it before */

        if (context->current == context)

    {

      /* For a shared network, we have no way to guess what the default route should be. */

      context->router.s_addr = 0;

      context->local = local; /* Use configured address for Server Identifier */

      context->current = param->current;

      param->current = context;

    }

        if (!(context->flags & CONTEXT_BRDCAST))

    context->broadcast.s_addr  = context->start.s_addr | ~context->netmask.s_addr;

      }   

  }

    }

  guess_range_netmask(local, netmask);

  for (context = daemon->dhcp; context; context = context->next)

    {

      if (context->netmask.s_addr != 0 &&

    is_same_net(local, context->start, context->netmask) &&

    is_same_net(local, context->end, context->netmask))

  {

    /* link it onto the current chain if we've not seen it before */

    if (if_index == param->ind && context->current == context)

      {

        context->router = local;

        context->local = local;

        context->current = param->current;

        param->current = context;

      }

    if (!(context->flags & CONTEXT_BRDCAST))

      {

        if (is_same_net(broadcast, context->start, context->netmask))

    context->broadcast = broadcast;

        else 

    context->broadcast.s_addr  = context->start.s_addr | ~context->netmask.s_addr;

      }

  }   

    }

  for (relay = daemon->relay4; relay; relay = relay->next)

    if (relay->local.addr4.s_addr == local.s_addr)

      relay->iface_index = if_index;

  return 1;

}

struct dhcp_context *address_available(struct dhcp_context *context, 

               struct in_addr taddr,

               struct dhcp_netid *netids)

{

  /* Check is an address is OK for this network, check all

     possible ranges. Make sure that the address isn't in use

     by the server itself. */

  unsigned int start, end, addr = ntohl(taddr.s_addr);

  struct dhcp_context *tmp;

  for (tmp = context; tmp; tmp = tmp->current)

    if (taddr.s_addr == context->router.s_addr)

      return NULL;

  for (tmp = context; tmp; tmp = tmp->current)

    {

      start = ntohl(tmp->start.s_addr);

      end = ntohl(tmp->end.s_addr);

      if (!(tmp->flags & (CONTEXT_STATIC | CONTEXT_PROXY)) &&

    addr >= start &&

    addr <= end &&

    match_netid(tmp->filter, netids, 1))

  return tmp;

    }

  return NULL;

}

struct dhcp_context *narrow_context(struct dhcp_context *context, 

            struct in_addr taddr,

            struct dhcp_netid *netids)

{

  /* We start of with a set of possible contexts, all on the current physical interface.

     These are chained on ->current.

     Here we have an address, and return the actual context corresponding to that

     address. Note that none may fit, if the address came a dhcp-host and is outside

     any dhcp-range. In that case we return a static range if possible, or failing that,

     any context on the correct subnet. (If there's more than one, this is a dodgy 

     configuration: maybe there should be a warning.) */

  struct dhcp_context *tmp;

  if (!(tmp = address_available(context, taddr, netids)))

    {

      for (tmp = context; tmp; tmp = tmp->current)

  if (match_netid(tmp->filter, netids, 1) &&

      is_same_net(taddr, tmp->start, tmp->netmask) && 

      (tmp->flags & CONTEXT_STATIC))

    break;

      if (!tmp)

  for (tmp = context; tmp; tmp = tmp->current)

    if (match_netid(tmp->filter, netids, 1) &&

        is_same_net(taddr, tmp->start, tmp->netmask) &&

        !(tmp->flags & CONTEXT_PROXY))

      break;

    }

  /* Only one context allowed now */

  if (tmp)

    tmp->current = NULL;

  return tmp;

}

struct dhcp_config *config_find_by_address(struct dhcp_config *configs, struct in_addr addr)

{

  struct dhcp_config *config;

  for (config = configs; config; config = config->next)

    if ((config->flags & CONFIG_ADDR) && config->addr.s_addr == addr.s_addr)

      return config;

  return NULL;

}

/* Check if and address is in use by sending ICMP ping.

   This wrapper handles a cache and load-limiting.

   Return is NULL is address in use, or a pointer to a cache entry

   recording that it isn't. */

struct ping_result *do_icmp_ping(time_t now, struct in_addr addr, unsigned int hash, int loopback)

{

  static struct ping_result dummy;

  struct ping_result *r, *victim = NULL;

  int count, max = (int)(0.6 * (((float)PING_CACHE_TIME)/

        ((float)PING_WAIT)));

  /* check if we failed to ping addr sometime in the last

     PING_CACHE_TIME seconds. If so, assume the same situation still exists.

     This avoids problems when a stupid client bangs

     on us repeatedly. As a final check, if we did more

     than 60% of the possible ping checks in the last 

     PING_CACHE_TIME, we are in high-load mode, so don't do any more. */

  for (count = 0, r = daemon->ping_results; r; r = r->next)

    if (difftime(now, r->time) >  (float)PING_CACHE_TIME)

      victim = r; /* old record */

    else 

      {

  count++;

  if (r->addr.s_addr == addr.s_addr)

    return r;

      }

  /* didn't find cached entry */

  if ((count >= max) || option_bool(OPT_NO_PING) || loopback)

    {

      /* overloaded, or configured not to check, loopback interface, return "not in use" */

      dummy.hash = hash;

      return &dummy;

    }

  else if (icmp_ping(addr))

    return NULL; /* address in use. */

  else

    {

      /* at this point victim may hold an expired record */

      if (!victim)

  {

    if ((victim = whine_malloc(sizeof(struct ping_result))))

      {

        victim->next = daemon->ping_results;

        daemon->ping_results = victim;

      }

  }

      /* record that this address is OK for 30s 

   without more ping checks */

      if (victim)

  {

    victim->addr = addr;

    victim->time = now;

    victim->hash = hash;

  }

      return victim;

    }

}

int address_allocate(struct dhcp_context *context,

         struct in_addr *addrp, unsigned char *hwaddr, int hw_len, 

         struct dhcp_netid *netids, time_t now, int loopback)   

{

  /* Find a free address: exclude anything in use and anything allocated to

     a particular hwaddr/clientid/hostname in our configuration.

     Try to return from contexts which match netids first. */

  struct in_addr start, addr;

  struct dhcp_context *c, *d;

  int i, pass;

  unsigned int j; 

  /* hash hwaddr: use the SDBM hashing algorithm.  Seems to give good

     dispersal even with similarly-valued "strings". */ 

  for (j = 0, i = 0; i < hw_len; i++)

    j = hwaddr[i] + (j << 6) + (j << 16) - j;

  /* j == 0 is marker */

  if (j == 0)

    j = 1;

  for (pass = 0; pass <= 1; pass++)

    for (c = context; c; c = c->current)

      if (c->flags & (CONTEXT_STATIC | CONTEXT_PROXY))

  continue;

      else if (!match_netid(c->filter, netids, pass))

  continue;

      else

  {

    if (option_bool(OPT_CONSEC_ADDR))

      /* seed is largest extant lease addr in this context */

      start = lease_find_max_addr(c);

    else

      /* pick a seed based on hwaddr */

      start.s_addr = htonl(ntohl(c->start.s_addr) + 

         ((j + c->addr_epoch) % (1 + ntohl(c->end.s_addr) - ntohl(c->start.s_addr))));

    /* iterate until we find a free address. */

    addr = start;

    do {

      /* eliminate addresses in use by the server. */

      for (d = context; d; d = d->current)

        if (addr.s_addr == d->router.s_addr)

    break;

      /* Addresses which end in .255 and .0 are broken in Windows even when using 

         supernetting. ie dhcp-range=192.168.0.1,192.168.1.254,255,255,254.0

         then 192.168.0.255 is a valid IP address, but not for Windows as it's

         in the class C range. See  KB281579. We therefore don't allocate these 

         addresses to avoid hard-to-diagnose problems. Thanks Bill. */      

      if (!d &&

    !lease_find_by_addr(addr) && 

    !config_find_by_address(daemon->dhcp_conf, addr) &&

    (!IN_CLASSC(ntohl(addr.s_addr)) || 

     ((ntohl(addr.s_addr) & 0xff) != 0xff && ((ntohl(addr.s_addr) & 0xff) != 0x0))))

        {

    /* in consec-ip mode, skip addresses equal to

       the number of addresses rejected by clients. This

       should avoid the same client being offered the same

       address after it has rjected it. */

    if (option_bool(OPT_CONSEC_ADDR) && c->addr_epoch)

      c->addr_epoch--;

    else

      {

        struct ping_result *r;

        if ((r = do_icmp_ping(now, addr, j, loopback)))

          {

      /* consec-ip mode: we offered this address for another client

         (different hash) recently, don't offer it to this one. */

      if (!option_bool(OPT_CONSEC_ADDR) || r->hash == j)

        {

          *addrp = addr;

          return 1;

        }

          }

        else

          {

      /* address in use: perturb address selection so that we are

         less likely to try this address again. */

      if (!option_bool(OPT_CONSEC_ADDR))

        c->addr_epoch++;

          }

      }

        }

      addr.s_addr = htonl(ntohl(addr.s_addr) + 1);