dhcpv4: remove comment code lines
[project/odhcpd.git] / src / dhcpv4.c
index 4b69467..0f613b2 100644 (file)
@@ -20,6 +20,7 @@
 #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>
@@ -33,7 +34,7 @@
 
 
 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);
@@ -44,6 +45,29 @@ 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)
 {
@@ -95,26 +119,19 @@ int setup_dhcpv4_interface(struct interface *iface, bool enable)
                }
 
                // Create a range if not specified
-               struct ifreq ifreq;
-               strncpy(ifreq.ifr_name, iface->ifname, sizeof(ifreq.ifr_name));
-
-               struct sockaddr_in *saddr = (struct sockaddr_in*)&ifreq.ifr_addr;
-               struct sockaddr_in *smask = (struct sockaddr_in*)&ifreq.ifr_netmask;
                if (!(iface->dhcpv4_start.s_addr & htonl(0xffff0000)) &&
-                               !(iface->dhcpv4_end.s_addr & htonl(0xffff0000)) &&
-                               !ioctl(sock, SIOCGIFADDR, &ifreq)) {
-                       struct in_addr addr = saddr->sin_addr;
+                               !(iface->dhcpv4_end.s_addr & htonl(0xffff0000))) {
+                       struct in_addr addr = ubus_get_address4(iface->ifname);
 
-                       ioctl(sock, SIOCGIFNETMASK, &ifreq);
-                       struct in_addr mask = smask->sin_addr;
+                       struct in_addr mask = ubus_get_mask4(iface->ifname);
 
                        uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
                        uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
 
                        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) |
@@ -155,17 +172,22 @@ int setup_dhcpv4_interface(struct interface *iface, bool enable)
                        a->addr = ntohl(lease->ipaddr.s_addr);
                        memcpy(a->hwaddr, lease->mac.ether_addr_octet, sizeof(a->hwaddr));
                        memcpy(a->hostname, lease->hostname, hostlen);
+                       a->valid_until = LONG_MAX;
 
                        // 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);
@@ -175,7 +197,7 @@ int setup_dhcpv4_interface(struct interface *iface, bool enable)
                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)) {
+                                       (iface->dhcpv4_start.s_addr & smask->sin_addr.s_addr)) {
                                list_del(&a->head);
                                free(a);
                        }
@@ -193,7 +215,6 @@ int setup_dhcpv4_interface(struct interface *iface, bool enable)
                        struct dhcpv4_assignment *a = list_first_entry(&iface->dhcpv4_assignments,
                                        struct dhcpv4_assignment, head);
                        list_del(&a->head);
-                       free(a->hostname);
                        free(a);
                }
 
@@ -219,7 +240,7 @@ static void dhcpv4_put(struct dhcpv4_message *msg, uint8_t **cookie,
 
 // Simple DHCPv6-server for information requests
 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;
@@ -325,8 +346,26 @@ 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;
 
@@ -362,18 +401,23 @@ 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)
@@ -387,16 +431,36 @@ 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);
 
@@ -407,54 +471,97 @@ 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;
 }
 
@@ -469,16 +576,16 @@ 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;
+                       if (c->addr == raddr)
+                               break;
                } else if (c->valid_until < now) {
                        list_del(&c->head);
                        free(c);
                }
        }
 
-       bool update_state = false;
        if (msg == DHCPV4_MSG_DISCOVER || msg == DHCPV4_MSG_REQUEST) {
                bool assigned = !!a;
                size_t hostlen = strlen(hostname) + 1;
@@ -520,18 +627,14 @@ static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
                if (assigned && a)
                        lease = a;
        } else if (msg == DHCPV4_MSG_RELEASE) {
-               if (a) {
+               if (a && a->valid_until != LONG_MAX)
                        a->valid_until = 0;
-                       update_state = true;
-               }
-       } else if (msg == DHCPV4_MSG_DECLINE) {
+       } else if (msg == DHCPV4_MSG_DECLINE && a && a->valid_until != LONG_MAX) {
                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;
 }