dhcpv4: fix DHCPv4 hostname handling
[project/odhcpd.git] / src / dhcpv4.c
index b4b0720..9d9ed92 100644 (file)
@@ -1,5 +1,6 @@
 /**
  * Copyright (C) 2012-2013 Steven Barth <steven@midlink.org>
+ * Copyright (C) 2016 Hans Dedecker <dedeckeh@gmail.com>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License v2 as published by
@@ -20,6 +21,7 @@
 #include <stddef.h>
 #include <stdlib.h>
 #include <resolv.h>
+#include <limits.h>
 #include <net/if.h>
 #include <net/if_arp.h>
 #include <netinet/ip.h>
 #include "dhcpv4.h"
 #include "dhcpv6.h"
 
-
+static void free_dhcpv4_assignment(struct dhcpv4_assignment *a);
 static void handle_dhcpv4(void *addr, void *data, size_t len,
-               struct interface *iface);
+               struct interface *iface, void *dest_addr);
 static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
                enum dhcpv4_msg msg, const uint8_t *mac, struct in_addr reqaddr,
-               const char *hostname);
-
+               uint32_t *leasetime, const char *hostname, const size_t hostname_len);
 
 // Create socket and register events
 int init_dhcpv4(void)
@@ -45,10 +46,34 @@ int init_dhcpv4(void)
        return 0;
 }
 
+char *dhcpv4_msg_to_string(uint8_t reqmsg)
+{
+       switch (reqmsg) {
+       case (DHCPV4_MSG_DISCOVER):
+               return "DHCPV4_MSG_DISCOVER";
+       case (DHCPV4_MSG_OFFER):
+               return "DHCPV4_MSG_OFFER";
+       case (DHCPV4_MSG_REQUEST):
+               return "DHCPV4_MSG_REQUEST";
+       case (DHCPV4_MSG_DECLINE):
+               return "DHCPV4_MSG_DECLINE";
+       case (DHCPV4_MSG_ACK):
+               return "DHCPV4_MSG_ACK";
+       case (DHCPV4_MSG_NAK):
+               return "DHCPV4_MSG_NAK";
+       case (DHCPV4_MSG_RELEASE):
+               return "DHCPV4_MSG_RELEASE";
+       case (DHCPV4_MSG_INFORM):
+               return "DHCPV4_MSG_INFORM";
+       default:
+               return "UNKNOWN";
+       }
+}
 
 int setup_dhcpv4_interface(struct interface *iface, bool enable)
 {
        if (iface->dhcpv4_event.uloop.fd > 0) {
+               uloop_fd_delete(&iface->dhcpv4_event.uloop);
                close(iface->dhcpv4_event.uloop.fd);
                iface->dhcpv4_event.uloop.fd = -1;
        }
@@ -58,6 +83,11 @@ int setup_dhcpv4_interface(struct interface *iface, bool enable)
                        INIT_LIST_HEAD(&iface->dhcpv4_assignments);
 
                int sock = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC, IPPROTO_UDP);
+               if (sock < 0) {
+                       syslog(LOG_ERR, "Failed to create DHCPv4 server socket: %s",
+                                       strerror(errno));
+                       return -1;
+               }
 
                // Basic IPv6 configuration
                int val = 1;
@@ -108,22 +138,28 @@ int setup_dhcpv4_interface(struct interface *iface, bool enable)
 
                        if (start && end && start < end &&
                                        start > ntohl(addr.s_addr & ~mask.s_addr) &&
-                                       (start & ntohl(mask.s_addr)) == start &&
-                                       (end & ntohl(mask.s_addr)) == end) {
+                                       (start & ntohl(~mask.s_addr)) == start &&
+                                       (end & ntohl(~mask.s_addr)) == end) {
                                iface->dhcpv4_start.s_addr = htonl(start) |
                                                (addr.s_addr & mask.s_addr);
                                iface->dhcpv4_end.s_addr = htonl(end) |
                                                (addr.s_addr & mask.s_addr);
-                       } else if (ntohl(mask.s_addr) <= 0xffffffc0) {
+                       } else if (ntohl(mask.s_addr) <= 0xfffffff0) {
                                start = addr.s_addr & mask.s_addr;
                                end = addr.s_addr & mask.s_addr;
 
                                if (ntohl(mask.s_addr) <= 0xffffff00) {
                                        iface->dhcpv4_start.s_addr = start | htonl(100);
                                        iface->dhcpv4_end.s_addr = end | htonl(250);
-                               } else {
+                               } else if (ntohl(mask.s_addr) <= 0xffffffc0) {
+                                       iface->dhcpv4_start.s_addr = start | htonl(10);
+                                       iface->dhcpv4_end.s_addr = end | htonl(60);
+                               } else if (ntohl(mask.s_addr) <= 0xffffffe0) {
                                        iface->dhcpv4_start.s_addr = start | htonl(10);
-                                       iface->dhcpv4_end.s_addr = end | htonl(59);
+                                       iface->dhcpv4_end.s_addr = end | htonl(30);
+                               } else {
+                                       iface->dhcpv4_start.s_addr = start | htonl(3);
+                                       iface->dhcpv4_end.s_addr = end | htonl(12);
                                }
                        }
 
@@ -134,36 +170,52 @@ int setup_dhcpv4_interface(struct interface *iface, bool enable)
                struct lease *lease;
                list_for_each_entry(lease, &leases, head) {
                        // Construct entry
-                       size_t hostlen = strlen(lease->hostname) + 1;
-                       struct dhcpv4_assignment *a = calloc(1, sizeof(*a) + hostlen);
+                       struct dhcpv4_assignment *a = calloc(1, sizeof(*a));
+                       if (!a) {
+                               syslog(LOG_ERR, "Calloc failed for static lease on interface %s",
+                                       iface->ifname);
+                               return -1;
+                       }
+                       if (lease->dhcpv4_leasetime >= 60)
+                               a->leasetime = lease->dhcpv4_leasetime;
 
                        a->addr = ntohl(lease->ipaddr.s_addr);
                        memcpy(a->hwaddr, lease->mac.ether_addr_octet, sizeof(a->hwaddr));
-                       memcpy(a->hostname, lease->hostname, hostlen);
+                       /* Static assignment */
+                       a->flags |= OAF_STATIC;
+                       /* Infinite valid */
+                       a->valid_until = 0;
 
                        // Assign to all interfaces
                        struct dhcpv4_assignment *c;
                        list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
                                if (c->addr > a->addr) {
                                        list_add_tail(&a->head, &c->head);
+                                       break;
                                } else if (c->addr == a->addr) {
                                        // Already an assignment with that number
                                        break;
                                }
                        }
+                       if (&c->head == &iface->dhcpv4_assignments) {
+                               list_add(&a->head, &iface->dhcpv4_assignments);
+                       }
 
-                       if (!a->head.next)
-                               free(a);
+                       if (a->head.next) {
+                               if (lease->hostname[0]) {
+                                       free(a->hostname);
+                                       a->hostname = strdup(lease->hostname);
+                               }
+                       } else
+                               free_dhcpv4_assignment(a);
                }
 
                // Clean invalid assignments
                struct dhcpv4_assignment *a, *n;
                list_for_each_entry_safe(a, n, &iface->dhcpv4_assignments, head) {
                        if ((htonl(a->addr) & smask->sin_addr.s_addr) !=
-                                       (saddr->sin_addr.s_addr & smask->sin_addr.s_addr)) {
-                               list_del(&a->head);
-                               free(a);
-                       }
+                                       (iface->dhcpv4_start.s_addr & smask->sin_addr.s_addr))
+                               free_dhcpv4_assignment(a);
                }
 
 
@@ -174,18 +226,21 @@ int setup_dhcpv4_interface(struct interface *iface, bool enable)
                iface->dhcpv4_event.handle_dgram = handle_dhcpv4;
                odhcpd_register(&iface->dhcpv4_event);
        } else if (iface->dhcpv4_assignments.next) {
-               while (!list_empty(&iface->dhcpv4_assignments)) {
-                       struct dhcpv4_assignment *a = list_first_entry(&iface->dhcpv4_assignments,
-                                       struct dhcpv4_assignment, head);
-                       list_del(&a->head);
-                       free(a->hostname);
-                       free(a);
-               }
-
+               while (!list_empty(&iface->dhcpv4_assignments))
+                       free_dhcpv4_assignment(list_first_entry(&iface->dhcpv4_assignments,
+                                                       struct dhcpv4_assignment, head));
        }
        return 0;
 }
 
+static void free_dhcpv4_assignment(struct dhcpv4_assignment *a)
+{
+       if (a->head.next)
+               list_del(&a->head);
+
+       free(a->hostname);
+       free(a);
+}
 
 static void dhcpv4_put(struct dhcpv4_message *msg, uint8_t **cookie,
                uint8_t type, uint8_t len, const void *data)
@@ -201,10 +256,9 @@ static void dhcpv4_put(struct dhcpv4_message *msg, uint8_t **cookie,
        *cookie = c + len;
 }
 
-
-// Simple DHCPv6-server for information requests
+// Handler for DHCPv4 messages
 static void handle_dhcpv4(void *addr, void *data, size_t len,
-               struct interface *iface)
+               struct interface *iface, _unused void *dest_addr)
 {
        if (!iface->dhcpv4)
                return;
@@ -267,8 +321,9 @@ static void handle_dhcpv4(void *addr, void *data, size_t len,
        uint8_t msg = DHCPV4_MSG_ACK;
 
        struct in_addr reqaddr = {INADDR_ANY};
+       uint32_t leasetime = 0;
+       size_t hostname_len = 0;
        char hostname[256];
-       hostname[0] = 0;
 
        uint8_t *start = &req->options[4];
        uint8_t *end = ((uint8_t*)data) + len;
@@ -277,14 +332,23 @@ static void handle_dhcpv4(void *addr, void *data, size_t len,
                if (opt->type == DHCPV4_OPT_MESSAGE && opt->len == 1) {
                        reqmsg = opt->data[0];
                } else if (opt->type == DHCPV4_OPT_HOSTNAME && opt->len > 0) {
-                       memcpy(hostname, opt->data, opt->len);
-                       hostname[opt->len] = 0;
+                       hostname_len = opt->len;
+                       memcpy(hostname, opt->data, hostname_len);
+                       hostname[hostname_len] = 0;
                } else if (opt->type == DHCPV4_OPT_IPADDRESS && opt->len == 4) {
                        memcpy(&reqaddr, opt->data, 4);
                } else if (opt->type == DHCPV4_OPT_SERVERID && opt->len == 4) {
                        if (memcmp(opt->data, &ifaddr.sin_addr, 4))
                                return;
-               }
+               } else if (iface->filter_class && opt->type == DHCPV4_OPT_USER_CLASS) {
+                       uint8_t *c = opt->data, *cend = &opt->data[opt->len];
+                       for (; c < cend && &c[*c] < cend; c = &c[1 + *c]) {
+                               size_t elen = strlen(iface->filter_class);
+                               if (*c == elen && !memcmp(&c[1], iface->filter_class, elen))
+                                       return; // Ignore from homenet
+                       }
+               } else if (opt->type == DHCPV4_OPT_LEASETIME && opt->len == 4)
+                       memcpy(&leasetime, opt->data, 4);
        }
 
        if (reqmsg != DHCPV4_MSG_DISCOVER && reqmsg != DHCPV4_MSG_REQUEST &&
@@ -294,7 +358,8 @@ static void handle_dhcpv4(void *addr, void *data, size_t len,
 
        struct dhcpv4_assignment *lease = NULL;
        if (reqmsg != DHCPV4_MSG_INFORM)
-               lease = dhcpv4_lease(iface, reqmsg, req->chaddr, reqaddr, hostname);
+               lease = dhcpv4_lease(iface, reqmsg, req->chaddr, reqaddr,
+                                       &leasetime, hostname, hostname_len);
 
        if (!lease) {
                if (reqmsg == DHCPV4_MSG_REQUEST)
@@ -303,8 +368,26 @@ static void handle_dhcpv4(void *addr, void *data, size_t len,
                        return;
        } else if (reqmsg == DHCPV4_MSG_DISCOVER) {
                msg = DHCPV4_MSG_OFFER;
+       } else if (reqmsg == DHCPV4_MSG_REQUEST && reqaddr.s_addr &&
+                       reqaddr.s_addr != htonl(lease->addr)) {
+               msg = DHCPV4_MSG_NAK;
+               /*
+                * DHCP client requested an IP which we can't offer to him. Probably the
+                * client changed the network. The reply type is set to DHCPV4_MSG_NAK,
+                * because the client should not use that IP.
+                *
+                * For modern devices we build an answer that includes a valid IP, like
+                * a DHCPV4_MSG_ACK. The client will use that IP and doesn't need to
+                * perform additional DHCP round trips.
+                *
+                */
        }
 
+       syslog(LOG_WARNING, "received %s from %x:%x:%x:%x:%x:%x",
+                       dhcpv4_msg_to_string(reqmsg),
+                       req->chaddr[0],req->chaddr[1],req->chaddr[2],
+                       req->chaddr[3],req->chaddr[4],req->chaddr[5]);
+
        if (reqmsg == DHCPV4_MSG_DECLINE || reqmsg == DHCPV4_MSG_RELEASE)
                return;
 
@@ -312,20 +395,24 @@ static void handle_dhcpv4(void *addr, void *data, size_t len,
        dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SERVERID, 4, &ifaddr.sin_addr);
 
        if (lease) {
+               uint32_t val;
+
                reply.yiaddr.s_addr = htonl(lease->addr);
 
-               uint32_t val = htonl(iface->dhcpv4_leasetime);
+               val = htonl(leasetime);
                dhcpv4_put(&reply, &cookie, DHCPV4_OPT_LEASETIME, 4, &val);
 
-               val = htonl(500 * iface->dhcpv4_leasetime / 1000);
-               dhcpv4_put(&reply, &cookie, DHCPV4_OPT_RENEW, 4, &val);
+               if (leasetime != UINT32_MAX) {
+                       val = htonl(500 * leasetime / 1000);
+                       dhcpv4_put(&reply, &cookie, DHCPV4_OPT_RENEW, 4, &val);
 
-               val = htonl(875 * iface->dhcpv4_leasetime / 1000);
-               dhcpv4_put(&reply, &cookie, DHCPV4_OPT_REBIND, 4, &val);
+                       val = htonl(875 * leasetime / 1000);
+                       dhcpv4_put(&reply, &cookie, DHCPV4_OPT_REBIND, 4, &val);
+               }
 
                dhcpv4_put(&reply, &cookie, DHCPV4_OPT_NETMASK, 4, &ifnetmask.sin_addr);
 
-               if (lease->hostname[0])
+               if (lease->hostname)
                        dhcpv4_put(&reply, &cookie, DHCPV4_OPT_HOSTNAME,
                                        strlen(lease->hostname), lease->hostname);
 
@@ -340,18 +427,23 @@ static void handle_dhcpv4(void *addr, void *data, size_t len,
                dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MTU, 2, &mtu);
        }
 
-       if (iface->search) {
-               char b[256];
-               if (dn_expand(iface->search, iface->search + iface->search_len,
-                               iface->search, b, sizeof(b)) > 0)
-                       dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DOMAIN, strlen(b), b);
+       if (iface->search && iface->search_len <= 255) {
+               dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
+                               iface->search_len, iface->search);
        } else if (!res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
-               dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DOMAIN,
-                               strlen(_res.dnsrch[0]), _res.dnsrch[0]);
+               uint8_t search_buf[256];
+               int len = dn_comp(_res.dnsrch[0], search_buf,
+                                               sizeof(search_buf), NULL, NULL);
+               if (len > 0)
+                       dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
+                                       len, search_buf);
        }
 
-       dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER, 4, &ifaddr.sin_addr);
-
+       if (iface->dhcpv4_router_cnt == 0)
+               dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER, 4, &ifaddr.sin_addr);
+       else
+               dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER,
+                               4 * iface->dhcpv4_router_cnt, iface->dhcpv4_router);
 
 
        if (iface->dhcpv4_dns_cnt == 0)
@@ -365,16 +457,36 @@ static void handle_dhcpv4(void *addr, void *data, size_t len,
 
        struct sockaddr_in dest = *((struct sockaddr_in*)addr);
        if (req->giaddr.s_addr) {
+               /*
+                * relay agent is configured, send reply to the agent
+                */
                dest.sin_addr = req->giaddr;
                dest.sin_port = htons(DHCPV4_SERVER_PORT);
        } else if (req->ciaddr.s_addr && req->ciaddr.s_addr != dest.sin_addr.s_addr) {
+               /*
+                * client has existing configuration (ciaddr is set) AND this address is
+                * not the address it used for the dhcp message
+                */
                dest.sin_addr = req->ciaddr;
                dest.sin_port = htons(DHCPV4_CLIENT_PORT);
        } else if ((ntohs(req->flags) & DHCPV4_FLAG_BROADCAST) ||
-                       req->hlen != reply.hlen) {
+                       req->hlen != reply.hlen || !reply.yiaddr.s_addr) {
+               /*
+                * client requests a broadcast reply OR we can't offer an IP
+                */
+               dest.sin_addr.s_addr = INADDR_BROADCAST;
+               dest.sin_port = htons(DHCPV4_CLIENT_PORT);
+       } else if (!req->ciaddr.s_addr && msg == DHCPV4_MSG_NAK) {
+               /*
+                * client has no previous configuration -> no IP, so we need to reply
+                * with a broadcast packet
+                */
                dest.sin_addr.s_addr = INADDR_BROADCAST;
                dest.sin_port = htons(DHCPV4_CLIENT_PORT);
        } else {
+               /*
+                * send reply to the newly (in this proccess) allocated IP
+                */
                dest.sin_addr = reply.yiaddr;
                dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 
@@ -385,61 +497,104 @@ static void handle_dhcpv4(void *addr, void *data, size_t len,
                ioctl(sock, SIOCSARP, &arp);
        }
 
+       if (dest.sin_addr.s_addr == INADDR_BROADCAST) {
+               /*
+                * reply goes to IP broadcast -> MAC broadcast
+                */
+               syslog(LOG_WARNING, "sending %s to ff:ff:ff:ff:ff:ff - %s",
+                               dhcpv4_msg_to_string(msg),
+                               inet_ntoa(dest.sin_addr));
+       } else {
+               /*
+                * reply is send directly to IP,
+                * MAC is assumed to be the same as the request
+                */
+               syslog(LOG_WARNING, "sending %s to %x:%x:%x:%x:%x:%x - %s",
+                               dhcpv4_msg_to_string(msg),
+                               req->chaddr[0],req->chaddr[1],req->chaddr[2],
+                               req->chaddr[3],req->chaddr[4],req->chaddr[5],
+                               inet_ntoa(dest.sin_addr));
+       }
+
        sendto(sock, &reply, sizeof(reply), MSG_DONTWAIT,
                        (struct sockaddr*)&dest, sizeof(dest));
 }
 
+static bool dhcpv4_test(struct interface *iface, uint32_t try)
+{
+       struct dhcpv4_assignment *c;
+       list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
+               if (c->addr == try) {
+                       return false;
+               }
+       }
+       return true;
+}
 
 static bool dhcpv4_assign(struct interface *iface,
                struct dhcpv4_assignment *assign, uint32_t raddr)
 {
-       const unsigned tries = 10;
        uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
        uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
        uint32_t count = end - start + 1;
 
-       // Seed RNG with checksum of DUID
+       // try to assign the IP the client asked for
+       if (start <= raddr && raddr <= end && dhcpv4_test(iface, raddr)) {
+               assign->addr = raddr;
+               list_add(&assign->head, &iface->dhcpv4_assignments);
+               syslog(LOG_DEBUG, "assigning the IP the client asked for: %u.%u.%u.%u",
+                               (assign->addr & 0xff000000) >> 24,
+                               (assign->addr & 0x00ff0000) >> 16,
+                               (assign->addr & 0x0000ff00) >> 8,
+                               (assign->addr & 0x000000ff));
+               return true;
+       }
+
+       // Seed RNG with checksum of hwaddress
        uint32_t seed = 0;
-       for (size_t i = 0; i < sizeof(assign->hwaddr); ++i)
-               seed += assign->hwaddr[i];
+       for (size_t i = 0; i < sizeof(assign->hwaddr); ++i) {
+               // Knuth's multiplicative method
+               uint8_t o = assign->hwaddr[i];
+               seed += (o*2654435761) % UINT32_MAX;
+       }
        srand(seed);
 
-       // Try to assign up to 100x
-       for (unsigned i = 0; i < tries; ++i) {
-               uint32_t try = (((uint32_t)rand()) % count) + start;
-               if (i == 0 && raddr >= start && raddr <= end)
-                       try = raddr;
-               else if (i == tries - 1)
-                       try = start;
+       uint32_t try = (((uint32_t)rand()) % count) + start;
+
+       if (list_empty(&iface->dhcpv4_assignments)) {
+               assign->addr = try;
+               list_add(&assign->head, &iface->dhcpv4_assignments);
+               syslog(LOG_DEBUG, "assigning mapped IP (empty list): %u.%u.%u.%u",
+                               (assign->addr & 0xff000000) >> 24,
+                               (assign->addr & 0x00ff0000) >> 16,
+                               (assign->addr & 0x0000ff00) >> 8,
+                               (assign->addr & 0x000000ff));
+               return true;
+       }
 
-               if (list_empty(&iface->dhcpv4_assignments)) {
+       for (uint32_t i = 0; i < count; ++i) {
+               if (dhcpv4_test(iface, try)) {
+                       /* test was successful: IP address is not assigned, assign it */
                        assign->addr = try;
                        list_add(&assign->head, &iface->dhcpv4_assignments);
+                       syslog(LOG_DEBUG, "assigning mapped IP: %u.%u.%u.%u (try %u of %u)",
+                                       (assign->addr & 0xff000000) >> 24,
+                                       (assign->addr & 0x00ff0000) >> 16,
+                                       (assign->addr & 0x0000ff00) >> 8,
+                                       (assign->addr & 0x000000ff), i, count);
                        return true;
                }
-
-               struct dhcpv4_assignment *c;
-               list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
-                       if (c->addr > try) {
-                               assign->addr = try;
-                               list_add_tail(&assign->head, &c->head);
-                               return true;
-                       } else if (c->addr == try) {
-                               if (i < tries - 1)
-                                       break;
-                               else
-                                       ++try;
-                       }
-               }
+               try = (((try - start) + 1) % count) + start;
        }
 
+       syslog(LOG_DEBUG, "can't assign any IP address -> address space is full");
        return false;
 }
 
 
 static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
                enum dhcpv4_msg msg, const uint8_t *mac, struct in_addr reqaddr,
-               const char *hostname)
+               uint32_t *leasetime, const char *hostname, const size_t hostname_len)
 {
        struct dhcpv4_assignment *lease = NULL;
        uint32_t raddr = ntohl(reqaddr.s_addr);
@@ -447,61 +602,83 @@ static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
 
        struct dhcpv4_assignment *c, *n, *a = NULL;
        list_for_each_entry_safe(c, n, &iface->dhcpv4_assignments, head) {
-               if (c->addr == raddr && !memcmp(c->hwaddr, mac, 6)) {
+               if (!memcmp(c->hwaddr, mac, 6)) {
                        a = c;
-                       break;
-               } else if (c->valid_until < now) {
-                       list_del(&c->head);
-                       free(c);
-               }
+                       if (c->addr == raddr)
+                               break;
+               } else if (!INFINITE_VALID(c->valid_until) && c->valid_until < now)
+                       free_dhcpv4_assignment(c);
        }
 
-       bool update_state = false;
        if (msg == DHCPV4_MSG_DISCOVER || msg == DHCPV4_MSG_REQUEST) {
                bool assigned = !!a;
-               size_t hostlen = strlen(hostname) + 1;
+               uint32_t my_leasetime;
 
                if (!a && !iface->no_dynamic_dhcp) { // Create new binding
-                       a = calloc(1, sizeof(*a) + hostlen);
+                       a = calloc(1, sizeof(*a));
+                       if (!a) {
+                               syslog(LOG_ERR, "Failed to calloc binding on interface %s", iface->ifname);
+                               return NULL;
+                       }
                        memcpy(a->hwaddr, mac, sizeof(a->hwaddr));
-                       memcpy(a->hostname, hostname, hostlen);
+                       // Don't consider new assignment as infinite
+                       a->valid_until = now;
 
                        assigned = dhcpv4_assign(iface, a, raddr);
                }
 
-               if (assigned && !a->hostname[0] && hostname) {
-                       a = realloc(a, sizeof(*a) + hostlen);
-                       memcpy(a->hostname, hostname, hostlen);
-
-                       // Fixup list
-                       a->head.next->prev = &a->head;
-                       a->head.prev->next = &a->head;
+               if (a->leasetime >= 60) {
+                       my_leasetime = a->leasetime;
+               } else {
+                       my_leasetime = iface->dhcpv4_leasetime;
                }
 
-               // Was only a solicitation: mark binding for removal
-               if (assigned && a->valid_until < now) {
-                       a->valid_until = (msg == DHCPV4_MSG_DISCOVER) ? 0 :
-                                       (now + iface->dhcpv4_leasetime);
+               if ((*leasetime == 0) || (my_leasetime < *leasetime))
+                       *leasetime = my_leasetime;
+
+               if (assigned) {
+                       if (msg == DHCPV4_MSG_DISCOVER) {
+                               a->flags &= ~OAF_BOUND;
+
+                               if (!(a->flags & OAF_STATIC))
+                                       a->valid_until = now;
+                       } else {
+                               if (hostname_len > 0) {
+                                       a->hostname = realloc(a->hostname, hostname_len + 1);
+                                       if (a->hostname) {
+                                               memcpy(a->hostname, hostname, hostname_len);
+                                               a->hostname[hostname_len] = 0;
+                                       }
+                               }
+
+                               a->flags |= OAF_BOUND;
+
+                               if (!(a->flags & OAF_STATIC))
+                                       a->valid_until = ((*leasetime == UINT32_MAX) ? 0 : (time_t)(now + *leasetime));
+                       }
                } else if (!assigned && a) { // Cleanup failed assignment
-                       free(a);
+                       free_dhcpv4_assignment(a);
                        a = NULL;
                }
 
                if (assigned && a)
                        lease = a;
-       } else if (msg == DHCPV4_MSG_RELEASE) {
-               if (a) {
-                       a->valid_until = 0;
-                       update_state = true;
+       } else if (msg == DHCPV4_MSG_RELEASE && a) {
+               a->flags &= ~OAF_BOUND;
+
+               if (!(a->flags & OAF_STATIC))
+                       a->valid_until = now - 1;
+
+       } else if (msg == DHCPV4_MSG_DECLINE && a) {
+               a->flags &= ~OAF_BOUND;
+
+               if (!(a->flags & OAF_STATIC)) {
+                       memset(a->hwaddr, 0, sizeof(a->hwaddr));
+                       a->valid_until = now + 3600; // Block address for 1h
                }
-       } else if (msg == DHCPV4_MSG_DECLINE) {
-               memset(a->hwaddr, 0, sizeof(a->hwaddr));
-               a->valid_until = now + 3600; // Block address for 1h
-               update_state = true;
        }
 
-       if (update_state)
-               dhcpv6_write_statefile();
+       dhcpv6_write_statefile();
 
        return lease;
 }