| /* vi: set sw=4 ts=4: */ |
| /* |
| * udhcp server |
| * Copyright (C) 1999 Matthew Ramsay <matthewr@moreton.com.au> |
| * Chris Trew <ctrew@moreton.com.au> |
| * |
| * Rewrite by Russ Dill <Russ.Dill@asu.edu> July 2001 |
| * |
| * 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; either version 2 of the License, or |
| * (at your option) any later version. |
| * |
| * 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, write to the Free Software |
| * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. |
| */ |
| //applet:IF_UDHCPD(APPLET(udhcpd, BB_DIR_USR_SBIN, BB_SUID_DROP)) |
| |
| //kbuild:lib-$(CONFIG_UDHCPD) += common.o packet.o signalpipe.o socket.o |
| //kbuild:lib-$(CONFIG_UDHCPD) += dhcpd.o arpping.o |
| //kbuild:lib-$(CONFIG_FEATURE_UDHCP_RFC3397) += domain_codec.o |
| |
| //usage:#define udhcpd_trivial_usage |
| //usage: "[-fS] [-I ADDR]" IF_FEATURE_UDHCP_PORT(" [-P N]") " [CONFFILE]" |
| //usage:#define udhcpd_full_usage "\n\n" |
| //usage: "DHCP server\n" |
| //usage: "\n -f Run in foreground" |
| //usage: "\n -S Log to syslog too" |
| //usage: "\n -I ADDR Local address" |
| //usage: "\n -a MSEC Timeout for ARP ping (default 2000)" |
| //usage: IF_FEATURE_UDHCP_PORT( |
| //usage: "\n -P N Use port N (default 67)" |
| //usage: ) |
| |
| #include <netinet/ether.h> |
| #include <syslog.h> |
| #include "common.h" |
| #include "dhcpc.h" |
| #include "dhcpd.h" |
| |
| /* globals */ |
| #define g_leases ((struct dyn_lease*)ptr_to_globals) |
| /* struct server_config_t server_config is in bb_common_bufsiz1 */ |
| |
| /* Takes the address of the pointer to the static_leases linked list, |
| * address to a 6 byte mac address, |
| * 4 byte IP address */ |
| static void add_static_lease(struct static_lease **st_lease_pp, |
| uint8_t *mac, |
| uint32_t nip) |
| { |
| struct static_lease *st_lease; |
| |
| /* Find the tail of the list */ |
| while ((st_lease = *st_lease_pp) != NULL) { |
| st_lease_pp = &st_lease->next; |
| } |
| |
| /* Add new node */ |
| *st_lease_pp = st_lease = xzalloc(sizeof(*st_lease)); |
| memcpy(st_lease->mac, mac, 6); |
| st_lease->nip = nip; |
| /*st_lease->next = NULL;*/ |
| } |
| |
| /* Find static lease IP by mac */ |
| static uint32_t get_static_nip_by_mac(struct static_lease *st_lease, void *mac) |
| { |
| while (st_lease) { |
| if (memcmp(st_lease->mac, mac, 6) == 0) |
| return st_lease->nip; |
| st_lease = st_lease->next; |
| } |
| |
| return 0; |
| } |
| |
| static int is_nip_reserved(struct static_lease *st_lease, uint32_t nip) |
| { |
| while (st_lease) { |
| if (st_lease->nip == nip) |
| return 1; |
| st_lease = st_lease->next; |
| } |
| |
| return 0; |
| } |
| |
| #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 2 |
| /* Print out static leases just to check what's going on */ |
| /* Takes the address of the pointer to the static_leases linked list */ |
| static void log_static_leases(struct static_lease **st_lease_pp) |
| { |
| struct static_lease *cur; |
| |
| if (dhcp_verbose < 2) |
| return; |
| |
| cur = *st_lease_pp; |
| while (cur) { |
| bb_error_msg("static lease: mac:%02x:%02x:%02x:%02x:%02x:%02x nip:%x", |
| cur->mac[0], cur->mac[1], cur->mac[2], |
| cur->mac[3], cur->mac[4], cur->mac[5], |
| cur->nip |
| ); |
| cur = cur->next; |
| } |
| } |
| #else |
| # define log_static_leases(st_lease_pp) ((void)0) |
| #endif |
| |
| /* Find the oldest expired lease, NULL if there are no expired leases */ |
| static struct dyn_lease *oldest_expired_lease(void) |
| { |
| struct dyn_lease *oldest_lease = NULL; |
| leasetime_t oldest_time = time(NULL); |
| unsigned i; |
| |
| /* Unexpired leases have g_leases[i].expires >= current time |
| * and therefore can't ever match */ |
| for (i = 0; i < server_config.max_leases; i++) { |
| if (g_leases[i].expires == 0 /* empty entry */ |
| || g_leases[i].expires < oldest_time |
| ) { |
| oldest_time = g_leases[i].expires; |
| oldest_lease = &g_leases[i]; |
| } |
| } |
| return oldest_lease; |
| } |
| |
| /* Clear out all leases with matching nonzero chaddr OR yiaddr. |
| * If chaddr == NULL, this is a conflict lease. |
| */ |
| static void clear_leases(const uint8_t *chaddr, uint32_t yiaddr) |
| { |
| unsigned i; |
| |
| for (i = 0; i < server_config.max_leases; i++) { |
| if ((chaddr && memcmp(g_leases[i].lease_mac, chaddr, 6) == 0) |
| || (yiaddr && g_leases[i].lease_nip == yiaddr) |
| ) { |
| memset(&g_leases[i], 0, sizeof(g_leases[i])); |
| } |
| } |
| } |
| |
| /* Add a lease into the table, clearing out any old ones. |
| * If chaddr == NULL, this is a conflict lease. |
| */ |
| static struct dyn_lease *add_lease( |
| const uint8_t *chaddr, uint32_t yiaddr, |
| leasetime_t leasetime, |
| const char *hostname, int hostname_len) |
| { |
| struct dyn_lease *oldest; |
| |
| /* clean out any old ones */ |
| clear_leases(chaddr, yiaddr); |
| |
| oldest = oldest_expired_lease(); |
| |
| if (oldest) { |
| memset(oldest, 0, sizeof(*oldest)); |
| if (hostname) { |
| char *p; |
| |
| hostname_len++; /* include NUL */ |
| if (hostname_len > sizeof(oldest->hostname)) |
| hostname_len = sizeof(oldest->hostname); |
| p = safe_strncpy(oldest->hostname, hostname, hostname_len); |
| /* |
| * Sanitization (s/bad_char/./g). |
| * The intent is not to allow only "DNS-valid" hostnames, |
| * but merely make dumpleases output safe for shells to use. |
| * We accept "0-9A-Za-z._-", all other chars turn to dots. |
| */ |
| while (*p) { |
| if (!isalnum(*p) && *p != '-' && *p != '_') |
| *p = '.'; |
| p++; |
| } |
| } |
| if (chaddr) |
| memcpy(oldest->lease_mac, chaddr, 6); |
| oldest->lease_nip = yiaddr; |
| oldest->expires = time(NULL) + leasetime; |
| } |
| |
| return oldest; |
| } |
| |
| /* True if a lease has expired */ |
| static int is_expired_lease(struct dyn_lease *lease) |
| { |
| return (lease->expires < (leasetime_t) time(NULL)); |
| } |
| |
| /* Find the first lease that matches MAC, NULL if no match */ |
| static struct dyn_lease *find_lease_by_mac(const uint8_t *mac) |
| { |
| unsigned i; |
| |
| for (i = 0; i < server_config.max_leases; i++) |
| if (memcmp(g_leases[i].lease_mac, mac, 6) == 0) |
| return &g_leases[i]; |
| |
| return NULL; |
| } |
| |
| /* Find the first lease that matches IP, NULL is no match */ |
| static struct dyn_lease *find_lease_by_nip(uint32_t nip) |
| { |
| unsigned i; |
| |
| for (i = 0; i < server_config.max_leases; i++) |
| if (g_leases[i].lease_nip == nip) |
| return &g_leases[i]; |
| |
| return NULL; |
| } |
| |
| /* Check if the IP is taken; if it is, add it to the lease table */ |
| static int nobody_responds_to_arp(uint32_t nip, const uint8_t *safe_mac, unsigned arpping_ms) |
| { |
| struct in_addr temp; |
| int r; |
| |
| r = arpping(nip, safe_mac, |
| server_config.server_nip, |
| server_config.server_mac, |
| server_config.interface, |
| arpping_ms); |
| if (r) |
| return r; |
| |
| temp.s_addr = nip; |
| bb_error_msg("%s belongs to someone, reserving it for %u seconds", |
| inet_ntoa(temp), (unsigned)server_config.conflict_time); |
| add_lease(NULL, nip, server_config.conflict_time, NULL, 0); |
| return 0; |
| } |
| |
| /* Find a new usable (we think) address */ |
| static uint32_t find_free_or_expired_nip(const uint8_t *safe_mac, unsigned arpping_ms) |
| { |
| uint32_t addr; |
| struct dyn_lease *oldest_lease = NULL; |
| |
| #if ENABLE_FEATURE_UDHCPD_BASE_IP_ON_MAC |
| uint32_t stop; |
| unsigned i, hash; |
| |
| /* hash hwaddr: use the SDBM hashing algorithm. Seems to give good |
| * dispersal even with similarly-valued "strings". |
| */ |
| hash = 0; |
| for (i = 0; i < 6; i++) |
| hash += safe_mac[i] + (hash << 6) + (hash << 16) - hash; |
| |
| /* pick a seed based on hwaddr then iterate until we find a free address. */ |
| addr = server_config.start_ip |
| + (hash % (1 + server_config.end_ip - server_config.start_ip)); |
| stop = addr; |
| #else |
| addr = server_config.start_ip; |
| #define stop (server_config.end_ip + 1) |
| #endif |
| do { |
| uint32_t nip; |
| struct dyn_lease *lease; |
| |
| /* ie, 192.168.55.0 */ |
| if ((addr & 0xff) == 0) |
| goto next_addr; |
| /* ie, 192.168.55.255 */ |
| if ((addr & 0xff) == 0xff) |
| goto next_addr; |
| nip = htonl(addr); |
| /* skip our own address */ |
| if (nip == server_config.server_nip) |
| goto next_addr; |
| /* is this a static lease addr? */ |
| if (is_nip_reserved(server_config.static_leases, nip)) |
| goto next_addr; |
| |
| lease = find_lease_by_nip(nip); |
| if (!lease) { |
| //TODO: DHCP servers do not always sit on the same subnet as clients: should *ping*, not arp-ping! |
| if (nobody_responds_to_arp(nip, safe_mac, arpping_ms)) |
| return nip; |
| } else { |
| if (!oldest_lease || lease->expires < oldest_lease->expires) |
| oldest_lease = lease; |
| } |
| |
| next_addr: |
| addr++; |
| #if ENABLE_FEATURE_UDHCPD_BASE_IP_ON_MAC |
| if (addr > server_config.end_ip) |
| addr = server_config.start_ip; |
| #endif |
| } while (addr != stop); |
| |
| if (oldest_lease |
| && is_expired_lease(oldest_lease) |
| && nobody_responds_to_arp(oldest_lease->lease_nip, safe_mac, arpping_ms) |
| ) { |
| return oldest_lease->lease_nip; |
| } |
| |
| return 0; |
| } |
| |
| /* On these functions, make sure your datatype matches */ |
| static int FAST_FUNC read_str(const char *line, void *arg) |
| { |
| char **dest = arg; |
| |
| free(*dest); |
| *dest = xstrdup(line); |
| return 1; |
| } |
| |
| static int FAST_FUNC read_u32(const char *line, void *arg) |
| { |
| *(uint32_t*)arg = bb_strtou32(line, NULL, 10); |
| return errno == 0; |
| } |
| |
| static int FAST_FUNC read_staticlease(const char *const_line, void *arg) |
| { |
| char *line; |
| char *mac_string; |
| char *ip_string; |
| struct ether_addr mac_bytes; /* it's "struct { uint8_t mac[6]; }" */ |
| uint32_t nip; |
| |
| /* Read mac */ |
| line = (char *) const_line; |
| mac_string = strtok_r(line, " \t", &line); |
| if (!mac_string || !ether_aton_r(mac_string, &mac_bytes)) |
| return 0; |
| |
| /* Read ip */ |
| ip_string = strtok_r(NULL, " \t", &line); |
| if (!ip_string || !udhcp_str2nip(ip_string, &nip)) |
| return 0; |
| |
| add_static_lease(arg, (uint8_t*) &mac_bytes, nip); |
| |
| log_static_leases(arg); |
| |
| return 1; |
| } |
| |
| static int FAST_FUNC read_optset(const char *line, void *arg) { |
| return udhcp_str2optset(line, arg, dhcp_optflags, dhcp_option_strings); |
| } |
| |
| struct config_keyword { |
| const char *keyword; |
| int (*handler)(const char *line, void *var) FAST_FUNC; |
| unsigned ofs; |
| const char *def; |
| }; |
| |
| #define OFS(field) offsetof(struct server_config_t, field) |
| |
| static const struct config_keyword keywords[] = { |
| /* keyword handler variable address default */ |
| {"start" , udhcp_str2nip , OFS(start_ip ), "192.168.0.20"}, |
| {"end" , udhcp_str2nip , OFS(end_ip ), "192.168.0.254"}, |
| {"interface" , read_str , OFS(interface ), "eth0"}, |
| /* Avoid "max_leases value not sane" warning by setting default |
| * to default_end_ip - default_start_ip + 1: */ |
| {"max_leases" , read_u32 , OFS(max_leases ), "235"}, |
| {"auto_time" , read_u32 , OFS(auto_time ), "7200"}, |
| {"decline_time" , read_u32 , OFS(decline_time ), "3600"}, |
| {"conflict_time", read_u32 , OFS(conflict_time), "3600"}, |
| {"offer_time" , read_u32 , OFS(offer_time ), "60"}, |
| {"min_lease" , read_u32 , OFS(min_lease_sec), "60"}, |
| {"lease_file" , read_str , OFS(lease_file ), LEASES_FILE}, |
| {"pidfile" , read_str , OFS(pidfile ), "/var/run/udhcpd.pid"}, |
| {"siaddr" , udhcp_str2nip , OFS(siaddr_nip ), "0.0.0.0"}, |
| /* keywords with no defaults must be last! */ |
| {"option" , read_optset , OFS(options ), ""}, |
| {"opt" , read_optset , OFS(options ), ""}, |
| {"notify_file" , read_str , OFS(notify_file ), NULL}, |
| {"sname" , read_str , OFS(sname ), NULL}, |
| {"boot_file" , read_str , OFS(boot_file ), NULL}, |
| {"static_lease" , read_staticlease, OFS(static_leases), ""}, |
| }; |
| enum { KWS_WITH_DEFAULTS = ARRAY_SIZE(keywords) - 6 }; |
| |
| static NOINLINE void read_config(const char *file) |
| { |
| parser_t *parser; |
| const struct config_keyword *k; |
| unsigned i; |
| char *token[2]; |
| |
| for (i = 0; i < KWS_WITH_DEFAULTS; i++) |
| keywords[i].handler(keywords[i].def, (char*)&server_config + keywords[i].ofs); |
| |
| parser = config_open(file); |
| while (config_read(parser, token, 2, 2, "# \t", PARSE_NORMAL)) { |
| for (k = keywords, i = 0; i < ARRAY_SIZE(keywords); k++, i++) { |
| if (strcasecmp(token[0], k->keyword) == 0) { |
| if (!k->handler(token[1], (char*)&server_config + k->ofs)) { |
| bb_error_msg("can't parse line %u in %s", |
| parser->lineno, file); |
| /* reset back to the default value */ |
| k->handler(k->def, (char*)&server_config + k->ofs); |
| } |
| break; |
| } |
| } |
| } |
| config_close(parser); |
| |
| server_config.start_ip = ntohl(server_config.start_ip); |
| server_config.end_ip = ntohl(server_config.end_ip); |
| } |
| |
| static void write_leases(void) |
| { |
| int fd; |
| unsigned i; |
| leasetime_t curr; |
| int64_t written_at; |
| |
| fd = open_or_warn(server_config.lease_file, O_WRONLY|O_CREAT|O_TRUNC); |
| if (fd < 0) |
| return; |
| |
| curr = written_at = time(NULL); |
| |
| written_at = SWAP_BE64(written_at); |
| full_write(fd, &written_at, sizeof(written_at)); |
| |
| for (i = 0; i < server_config.max_leases; i++) { |
| leasetime_t tmp_time; |
| |
| if (g_leases[i].lease_nip == 0) |
| continue; |
| |
| /* Screw with the time in the struct, for easier writing */ |
| tmp_time = g_leases[i].expires; |
| |
| g_leases[i].expires -= curr; |
| if ((signed_leasetime_t) g_leases[i].expires < 0) |
| g_leases[i].expires = 0; |
| g_leases[i].expires = htonl(g_leases[i].expires); |
| |
| /* No error check. If the file gets truncated, |
| * we lose some leases on restart. Oh well. */ |
| full_write(fd, &g_leases[i], sizeof(g_leases[i])); |
| |
| /* Then restore it when done */ |
| g_leases[i].expires = tmp_time; |
| } |
| close(fd); |
| |
| if (server_config.notify_file) { |
| char *argv[3]; |
| argv[0] = server_config.notify_file; |
| argv[1] = server_config.lease_file; |
| argv[2] = NULL; |
| spawn_and_wait(argv); |
| } |
| } |
| |
| static NOINLINE void read_leases(const char *file) |
| { |
| struct dyn_lease lease; |
| int64_t written_at, time_passed; |
| int fd; |
| #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1 |
| unsigned i = 0; |
| #endif |
| |
| fd = open_or_warn(file, O_RDONLY); |
| if (fd < 0) |
| return; |
| |
| if (full_read(fd, &written_at, sizeof(written_at)) != sizeof(written_at)) |
| goto ret; |
| written_at = SWAP_BE64(written_at); |
| |
| time_passed = time(NULL) - written_at; |
| /* Strange written_at, or lease file from old version of udhcpd |
| * which had no "written_at" field? */ |
| if ((uint64_t)time_passed > 12 * 60 * 60) |
| goto ret; |
| |
| while (full_read(fd, &lease, sizeof(lease)) == sizeof(lease)) { |
| uint32_t y = ntohl(lease.lease_nip); |
| if (y >= server_config.start_ip && y <= server_config.end_ip) { |
| signed_leasetime_t expires = ntohl(lease.expires) - (signed_leasetime_t)time_passed; |
| uint32_t static_nip; |
| |
| if (expires <= 0) |
| /* We keep expired leases: add_lease() will add |
| * a lease with 0 seconds remaining. |
| * Fewer IP address changes this way for mass reboot scenario. |
| */ |
| expires = 0; |
| |
| /* Check if there is a different static lease for this IP or MAC */ |
| static_nip = get_static_nip_by_mac(server_config.static_leases, lease.lease_mac); |
| if (static_nip) { |
| /* NB: we do not add lease even if static_nip == lease.lease_nip. |
| */ |
| continue; |
| } |
| if (is_nip_reserved(server_config.static_leases, lease.lease_nip)) |
| continue; |
| |
| /* NB: add_lease takes "relative time", IOW, |
| * lease duration, not lease deadline. */ |
| if (add_lease(lease.lease_mac, lease.lease_nip, |
| expires, |
| lease.hostname, sizeof(lease.hostname) |
| ) == 0 |
| ) { |
| bb_error_msg("too many leases while loading %s", file); |
| break; |
| } |
| #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1 |
| i++; |
| #endif |
| } |
| } |
| log1("read %d leases", i); |
| ret: |
| close(fd); |
| } |
| |
| /* Send a packet to a specific mac address and ip address by creating our own ip packet */ |
| static void send_packet_to_client(struct dhcp_packet *dhcp_pkt, int force_broadcast) |
| { |
| const uint8_t *chaddr; |
| uint32_t ciaddr; |
| |
| // Was: |
| //if (force_broadcast) { /* broadcast */ } |
| //else if (dhcp_pkt->ciaddr) { /* unicast to dhcp_pkt->ciaddr */ } |
| //else if (dhcp_pkt->flags & htons(BROADCAST_FLAG)) { /* broadcast */ } |
| //else { /* unicast to dhcp_pkt->yiaddr */ } |
| // But this is wrong: yiaddr is _our_ idea what client's IP is |
| // (for example, from lease file). Client may not know that, |
| // and may not have UDP socket listening on that IP! |
| // We should never unicast to dhcp_pkt->yiaddr! |
| // dhcp_pkt->ciaddr, OTOH, comes from client's request packet, |
| // and can be used. |
| |
| if (force_broadcast |
| || (dhcp_pkt->flags & htons(BROADCAST_FLAG)) |
| || dhcp_pkt->ciaddr == 0 |
| ) { |
| log1("broadcasting packet to client"); |
| ciaddr = INADDR_BROADCAST; |
| chaddr = MAC_BCAST_ADDR; |
| } else { |
| log1("unicasting packet to client ciaddr"); |
| ciaddr = dhcp_pkt->ciaddr; |
| chaddr = dhcp_pkt->chaddr; |
| } |
| |
| udhcp_send_raw_packet(dhcp_pkt, |
| /*src*/ server_config.server_nip, SERVER_PORT, |
| /*dst*/ ciaddr, CLIENT_PORT, chaddr, |
| server_config.ifindex); |
| } |
| |
| /* Send a packet to gateway_nip using the kernel ip stack */ |
| static void send_packet_to_relay(struct dhcp_packet *dhcp_pkt) |
| { |
| log1("forwarding packet to relay"); |
| |
| udhcp_send_kernel_packet(dhcp_pkt, |
| server_config.server_nip, SERVER_PORT, |
| dhcp_pkt->gateway_nip, SERVER_PORT, |
| /*send_flags:*/ 0 |
| ); |
| } |
| |
| static void send_packet(struct dhcp_packet *dhcp_pkt, int force_broadcast) |
| { |
| if (dhcp_pkt->gateway_nip) |
| send_packet_to_relay(dhcp_pkt); |
| else |
| send_packet_to_client(dhcp_pkt, force_broadcast); |
| } |
| |
| static void init_packet(struct dhcp_packet *packet, struct dhcp_packet *oldpacket, char type) |
| { |
| /* Sets op, htype, hlen, cookie fields |
| * and adds DHCP_MESSAGE_TYPE option */ |
| udhcp_init_header(packet, type); |
| |
| packet->xid = oldpacket->xid; |
| memcpy(packet->chaddr, oldpacket->chaddr, sizeof(oldpacket->chaddr)); |
| packet->flags = oldpacket->flags; |
| packet->gateway_nip = oldpacket->gateway_nip; |
| packet->ciaddr = oldpacket->ciaddr; |
| udhcp_add_simple_option(packet, DHCP_SERVER_ID, server_config.server_nip); |
| } |
| |
| /* Fill options field, siaddr_nip, and sname and boot_file fields. |
| * TODO: teach this code to use overload option. |
| */ |
| static void add_server_options(struct dhcp_packet *packet) |
| { |
| struct option_set *curr = server_config.options; |
| |
| while (curr) { |
| if (curr->data[OPT_CODE] != DHCP_LEASE_TIME) |
| udhcp_add_binary_option(packet, curr->data); |
| curr = curr->next; |
| } |
| |
| packet->siaddr_nip = server_config.siaddr_nip; |
| |
| if (server_config.sname) |
| strncpy((char*)packet->sname, server_config.sname, sizeof(packet->sname) - 1); |
| if (server_config.boot_file) |
| strncpy((char*)packet->file, server_config.boot_file, sizeof(packet->file) - 1); |
| } |
| |
| static uint32_t select_lease_time(struct dhcp_packet *packet) |
| { |
| uint32_t lease_time_sec = server_config.max_lease_sec; |
| uint8_t *lease_time_opt = udhcp_get_option(packet, DHCP_LEASE_TIME); |
| if (lease_time_opt) { |
| move_from_unaligned32(lease_time_sec, lease_time_opt); |
| lease_time_sec = ntohl(lease_time_sec); |
| if (lease_time_sec > server_config.max_lease_sec) |
| lease_time_sec = server_config.max_lease_sec; |
| if (lease_time_sec < server_config.min_lease_sec) |
| lease_time_sec = server_config.min_lease_sec; |
| } |
| return lease_time_sec; |
| } |
| |
| /* We got a DHCP DISCOVER. Send an OFFER. */ |
| /* NOINLINE: limit stack usage in caller */ |
| static NOINLINE void send_offer(struct dhcp_packet *oldpacket, |
| uint32_t static_lease_nip, |
| struct dyn_lease *lease, |
| uint8_t *requested_ip_opt, |
| unsigned arpping_ms) |
| { |
| struct dhcp_packet packet; |
| uint32_t lease_time_sec; |
| struct in_addr addr; |
| |
| init_packet(&packet, oldpacket, DHCPOFFER); |
| |
| /* If it is a static lease, use its IP */ |
| packet.yiaddr = static_lease_nip; |
| /* Else: */ |
| if (!static_lease_nip) { |
| /* We have no static lease for client's chaddr */ |
| uint32_t req_nip; |
| const char *p_host_name; |
| |
| if (lease) { |
| /* We have a dynamic lease for client's chaddr. |
| * Reuse its IP (even if lease is expired). |
| * Note that we ignore requested IP in this case. |
| */ |
| packet.yiaddr = lease->lease_nip; |
| } |
| /* Or: if client has requested an IP */ |
| else if (requested_ip_opt != NULL |
| /* (read IP) */ |
| && (move_from_unaligned32(req_nip, requested_ip_opt), 1) |
| /* and the IP is in the lease range */ |
| && ntohl(req_nip) >= server_config.start_ip |
| && ntohl(req_nip) <= server_config.end_ip |
| /* and */ |
| && ( !(lease = find_lease_by_nip(req_nip)) /* is not already taken */ |
| || is_expired_lease(lease) /* or is taken, but expired */ |
| ) |
| ) { |
| packet.yiaddr = req_nip; |
| } |
| else { |
| /* Otherwise, find a free IP */ |
| packet.yiaddr = find_free_or_expired_nip(oldpacket->chaddr, arpping_ms); |
| } |
| |
| if (!packet.yiaddr) { |
| bb_error_msg("no free IP addresses. OFFER abandoned"); |
| return; |
| } |
| /* Reserve the IP for a short time hoping to get DHCPREQUEST soon */ |
| p_host_name = (const char*) udhcp_get_option(oldpacket, DHCP_HOST_NAME); |
| lease = add_lease(packet.chaddr, packet.yiaddr, |
| server_config.offer_time, |
| p_host_name, |
| p_host_name ? (unsigned char)p_host_name[OPT_LEN - OPT_DATA] : 0 |
| ); |
| if (!lease) { |
| bb_error_msg("no free IP addresses. OFFER abandoned"); |
| return; |
| } |
| } |
| |
| lease_time_sec = select_lease_time(oldpacket); |
| udhcp_add_simple_option(&packet, DHCP_LEASE_TIME, htonl(lease_time_sec)); |
| add_server_options(&packet); |
| |
| addr.s_addr = packet.yiaddr; |
| bb_error_msg("sending OFFER of %s", inet_ntoa(addr)); |
| /* send_packet emits error message itself if it detects failure */ |
| send_packet(&packet, /*force_bcast:*/ 0); |
| } |
| |
| /* NOINLINE: limit stack usage in caller */ |
| static NOINLINE void send_NAK(struct dhcp_packet *oldpacket) |
| { |
| struct dhcp_packet packet; |
| |
| init_packet(&packet, oldpacket, DHCPNAK); |
| |
| log1("sending %s", "NAK"); |
| send_packet(&packet, /*force_bcast:*/ 1); |
| } |
| |
| /* NOINLINE: limit stack usage in caller */ |
| static NOINLINE void send_ACK(struct dhcp_packet *oldpacket, uint32_t yiaddr) |
| { |
| struct dhcp_packet packet; |
| uint32_t lease_time_sec; |
| struct in_addr addr; |
| const char *p_host_name; |
| |
| init_packet(&packet, oldpacket, DHCPACK); |
| packet.yiaddr = yiaddr; |
| |
| lease_time_sec = select_lease_time(oldpacket); |
| udhcp_add_simple_option(&packet, DHCP_LEASE_TIME, htonl(lease_time_sec)); |
| |
| add_server_options(&packet); |
| |
| addr.s_addr = yiaddr; |
| bb_error_msg("sending ACK to %s", inet_ntoa(addr)); |
| send_packet(&packet, /*force_bcast:*/ 0); |
| |
| p_host_name = (const char*) udhcp_get_option(oldpacket, DHCP_HOST_NAME); |
| add_lease(packet.chaddr, packet.yiaddr, |
| lease_time_sec, |
| p_host_name, |
| p_host_name ? (unsigned char)p_host_name[OPT_LEN - OPT_DATA] : 0 |
| ); |
| if (ENABLE_FEATURE_UDHCPD_WRITE_LEASES_EARLY) { |
| /* rewrite the file with leases at every new acceptance */ |
| write_leases(); |
| } |
| } |
| |
| /* NOINLINE: limit stack usage in caller */ |
| static NOINLINE void send_inform(struct dhcp_packet *oldpacket) |
| { |
| struct dhcp_packet packet; |
| |
| /* "If a client has obtained a network address through some other means |
| * (e.g., manual configuration), it may use a DHCPINFORM request message |
| * to obtain other local configuration parameters. Servers receiving a |
| * DHCPINFORM message construct a DHCPACK message with any local |
| * configuration parameters appropriate for the client without: |
| * allocating a new address, checking for an existing binding, filling |
| * in 'yiaddr' or including lease time parameters. The servers SHOULD |
| * unicast the DHCPACK reply to the address given in the 'ciaddr' field |
| * of the DHCPINFORM message. |
| * ... |
| * The server responds to a DHCPINFORM message by sending a DHCPACK |
| * message directly to the address given in the 'ciaddr' field |
| * of the DHCPINFORM message. The server MUST NOT send a lease |
| * expiration time to the client and SHOULD NOT fill in 'yiaddr'." |
| */ |
| //TODO: do a few sanity checks: is ciaddr set? |
| //Better yet: is ciaddr == IP source addr? |
| init_packet(&packet, oldpacket, DHCPACK); |
| add_server_options(&packet); |
| |
| send_packet(&packet, /*force_bcast:*/ 0); |
| } |
| |
| int udhcpd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; |
| int udhcpd_main(int argc UNUSED_PARAM, char **argv) |
| { |
| int server_socket = -1, retval; |
| uint8_t *state; |
| unsigned timeout_end; |
| unsigned num_ips; |
| unsigned opt; |
| struct option_set *option; |
| char *str_I = str_I; |
| const char *str_a = "2000"; |
| unsigned arpping_ms; |
| IF_FEATURE_UDHCP_PORT(char *str_P;) |
| |
| setup_common_bufsiz(); |
| |
| IF_FEATURE_UDHCP_PORT(SERVER_PORT = 67;) |
| IF_FEATURE_UDHCP_PORT(CLIENT_PORT = 68;) |
| |
| opt = getopt32(argv, "^" |
| "fSI:va:"IF_FEATURE_UDHCP_PORT("P:") |
| "\0" |
| #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1 |
| "vv" |
| #endif |
| , &str_I |
| , &str_a |
| IF_FEATURE_UDHCP_PORT(, &str_P) |
| IF_UDHCP_VERBOSE(, &dhcp_verbose) |
| ); |
| if (!(opt & 1)) { /* no -f */ |
| bb_daemonize_or_rexec(0, argv); |
| logmode = LOGMODE_NONE; |
| } |
| /* update argv after the possible vfork+exec in daemonize */ |
| argv += optind; |
| if (opt & 2) { /* -S */ |
| openlog(applet_name, LOG_PID, LOG_DAEMON); |
| logmode |= LOGMODE_SYSLOG; |
| } |
| if (opt & 4) { /* -I */ |
| len_and_sockaddr *lsa = xhost_and_af2sockaddr(str_I, 0, AF_INET); |
| server_config.server_nip = lsa->u.sin.sin_addr.s_addr; |
| free(lsa); |
| } |
| #if ENABLE_FEATURE_UDHCP_PORT |
| if (opt & 32) { /* -P */ |
| SERVER_PORT = xatou16(str_P); |
| CLIENT_PORT = SERVER_PORT + 1; |
| } |
| #endif |
| arpping_ms = xatou(str_a); |
| |
| /* Would rather not do read_config before daemonization - |
| * otherwise NOMMU machines will parse config twice */ |
| read_config(argv[0] ? argv[0] : DHCPD_CONF_FILE); |
| |
| /* Make sure fd 0,1,2 are open */ |
| bb_sanitize_stdio(); |
| /* Equivalent of doing a fflush after every \n */ |
| setlinebuf(stdout); |
| |
| /* Create pidfile */ |
| write_pidfile(server_config.pidfile); |
| /* if (!..) bb_perror_msg("can't create pidfile %s", pidfile); */ |
| |
| bb_error_msg("started, v"BB_VER); |
| |
| option = udhcp_find_option(server_config.options, DHCP_LEASE_TIME); |
| server_config.max_lease_sec = DEFAULT_LEASE_TIME; |
| if (option) { |
| move_from_unaligned32(server_config.max_lease_sec, option->data + OPT_DATA); |
| server_config.max_lease_sec = ntohl(server_config.max_lease_sec); |
| } |
| |
| /* Sanity check */ |
| num_ips = server_config.end_ip - server_config.start_ip + 1; |
| if (server_config.max_leases > num_ips) { |
| bb_error_msg("max_leases=%u is too big, setting to %u", |
| (unsigned)server_config.max_leases, num_ips); |
| server_config.max_leases = num_ips; |
| } |
| |
| /* this sets g_leases */ |
| SET_PTR_TO_GLOBALS(xzalloc(server_config.max_leases * sizeof(g_leases[0]))); |
| |
| read_leases(server_config.lease_file); |
| |
| if (udhcp_read_interface(server_config.interface, |
| &server_config.ifindex, |
| (server_config.server_nip == 0 ? &server_config.server_nip : NULL), |
| server_config.server_mac) |
| ) { |
| retval = 1; |
| goto ret; |
| } |
| |
| /* Setup the signal pipe */ |
| udhcp_sp_setup(); |
| |
| continue_with_autotime: |
| timeout_end = monotonic_sec() + server_config.auto_time; |
| while (1) { /* loop until universe collapses */ |
| struct pollfd pfds[2]; |
| struct dhcp_packet packet; |
| int bytes; |
| int tv; |
| uint8_t *server_id_opt; |
| uint8_t *requested_ip_opt; |
| uint32_t requested_nip = requested_nip; /* for compiler */ |
| uint32_t static_lease_nip; |
| struct dyn_lease *lease, fake_lease; |
| |
| if (server_socket < 0) { |
| server_socket = udhcp_listen_socket(/*INADDR_ANY,*/ SERVER_PORT, |
| server_config.interface); |
| } |
| |
| udhcp_sp_fd_set(pfds, server_socket); |
| tv = timeout_end - monotonic_sec(); |
| retval = 0; |
| if (!server_config.auto_time || tv > 0) { |
| retval = poll(pfds, 2, server_config.auto_time ? tv * 1000 : -1); |
| } |
| if (retval == 0) { |
| write_leases(); |
| goto continue_with_autotime; |
| } |
| if (retval < 0 && errno != EINTR) { |
| log1("error on select"); |
| continue; |
| } |
| |
| switch (udhcp_sp_read(pfds)) { |
| case SIGUSR1: |
| bb_error_msg("received %s", "SIGUSR1"); |
| write_leases(); |
| /* why not just reset the timeout, eh */ |
| goto continue_with_autotime; |
| case SIGTERM: |
| bb_error_msg("received %s", "SIGTERM"); |
| write_leases(); |
| goto ret0; |
| case 0: /* no signal: read a packet */ |
| break; |
| default: /* signal or error (probably EINTR): back to select */ |
| continue; |
| } |
| |
| bytes = udhcp_recv_kernel_packet(&packet, server_socket); |
| if (bytes < 0) { |
| /* bytes can also be -2 ("bad packet data") */ |
| if (bytes == -1 && errno != EINTR) { |
| log1("read error: "STRERROR_FMT", reopening socket" STRERROR_ERRNO); |
| close(server_socket); |
| server_socket = -1; |
| } |
| continue; |
| } |
| if (packet.hlen != 6) { |
| bb_error_msg("MAC length != 6, ignoring packet"); |
| continue; |
| } |
| if (packet.op != BOOTREQUEST) { |
| bb_error_msg("not a REQUEST, ignoring packet"); |
| continue; |
| } |
| state = udhcp_get_option(&packet, DHCP_MESSAGE_TYPE); |
| if (state == NULL || state[0] < DHCP_MINTYPE || state[0] > DHCP_MAXTYPE) { |
| bb_error_msg("no or bad message type option, ignoring packet"); |
| continue; |
| } |
| |
| /* Get SERVER_ID if present */ |
| server_id_opt = udhcp_get_option(&packet, DHCP_SERVER_ID); |
| if (server_id_opt) { |
| uint32_t server_id_network_order; |
| move_from_unaligned32(server_id_network_order, server_id_opt); |
| if (server_id_network_order != server_config.server_nip) { |
| /* client talks to somebody else */ |
| log1("server ID doesn't match, ignoring"); |
| continue; |
| } |
| } |
| |
| /* Look for a static/dynamic lease */ |
| static_lease_nip = get_static_nip_by_mac(server_config.static_leases, &packet.chaddr); |
| if (static_lease_nip) { |
| bb_error_msg("found static lease: %x", static_lease_nip); |
| memcpy(&fake_lease.lease_mac, &packet.chaddr, 6); |
| fake_lease.lease_nip = static_lease_nip; |
| fake_lease.expires = 0; |
| lease = &fake_lease; |
| } else { |
| lease = find_lease_by_mac(packet.chaddr); |
| } |
| |
| /* Get REQUESTED_IP if present */ |
| requested_ip_opt = udhcp_get_option(&packet, DHCP_REQUESTED_IP); |
| if (requested_ip_opt) { |
| move_from_unaligned32(requested_nip, requested_ip_opt); |
| } |
| |
| switch (state[0]) { |
| |
| case DHCPDISCOVER: |
| log1("received %s", "DISCOVER"); |
| |
| send_offer(&packet, static_lease_nip, lease, requested_ip_opt, arpping_ms); |
| break; |
| |
| case DHCPREQUEST: |
| log1("received %s", "REQUEST"); |
| /* RFC 2131: |
| |
| o DHCPREQUEST generated during SELECTING state: |
| |
| Client inserts the address of the selected server in 'server |
| identifier', 'ciaddr' MUST be zero, 'requested IP address' MUST be |
| filled in with the yiaddr value from the chosen DHCPOFFER. |
| |
| Note that the client may choose to collect several DHCPOFFER |
| messages and select the "best" offer. The client indicates its |
| selection by identifying the offering server in the DHCPREQUEST |
| message. If the client receives no acceptable offers, the client |
| may choose to try another DHCPDISCOVER message. Therefore, the |
| servers may not receive a specific DHCPREQUEST from which they can |
| decide whether or not the client has accepted the offer. |
| |
| o DHCPREQUEST generated during INIT-REBOOT state: |
| |
| 'server identifier' MUST NOT be filled in, 'requested IP address' |
| option MUST be filled in with client's notion of its previously |
| assigned address. 'ciaddr' MUST be zero. The client is seeking to |
| verify a previously allocated, cached configuration. Server SHOULD |
| send a DHCPNAK message to the client if the 'requested IP address' |
| is incorrect, or is on the wrong network. |
| |
| Determining whether a client in the INIT-REBOOT state is on the |
| correct network is done by examining the contents of 'giaddr', the |
| 'requested IP address' option, and a database lookup. If the DHCP |
| server detects that the client is on the wrong net (i.e., the |
| result of applying the local subnet mask or remote subnet mask (if |
| 'giaddr' is not zero) to 'requested IP address' option value |
| doesn't match reality), then the server SHOULD send a DHCPNAK |
| message to the client. |
| |
| If the network is correct, then the DHCP server should check if |
| the client's notion of its IP address is correct. If not, then the |
| server SHOULD send a DHCPNAK message to the client. If the DHCP |
| server has no record of this client, then it MUST remain silent, |
| and MAY output a warning to the network administrator. This |
| behavior is necessary for peaceful coexistence of non- |
| communicating DHCP servers on the same wire. |
| |
| If 'giaddr' is 0x0 in the DHCPREQUEST message, the client is on |
| the same subnet as the server. The server MUST broadcast the |
| DHCPNAK message to the 0xffffffff broadcast address because the |
| client may not have a correct network address or subnet mask, and |
| the client may not be answering ARP requests. |
| |
| If 'giaddr' is set in the DHCPREQUEST message, the client is on a |
| different subnet. The server MUST set the broadcast bit in the |
| DHCPNAK, so that the relay agent will broadcast the DHCPNAK to the |
| client, because the client may not have a correct network address |
| or subnet mask, and the client may not be answering ARP requests. |
| |
| o DHCPREQUEST generated during RENEWING state: |
| |
| 'server identifier' MUST NOT be filled in, 'requested IP address' |
| option MUST NOT be filled in, 'ciaddr' MUST be filled in with |
| client's IP address. In this situation, the client is completely |
| configured, and is trying to extend its lease. This message will |
| be unicast, so no relay agents will be involved in its |
| transmission. Because 'giaddr' is therefore not filled in, the |
| DHCP server will trust the value in 'ciaddr', and use it when |
| replying to the client. |
| |
| A client MAY choose to renew or extend its lease prior to T1. The |
| server may choose not to extend the lease (as a policy decision by |
| the network administrator), but should return a DHCPACK message |
| regardless. |
| |
| o DHCPREQUEST generated during REBINDING state: |
| |
| 'server identifier' MUST NOT be filled in, 'requested IP address' |
| option MUST NOT be filled in, 'ciaddr' MUST be filled in with |
| client's IP address. In this situation, the client is completely |
| configured, and is trying to extend its lease. This message MUST |
| be broadcast to the 0xffffffff IP broadcast address. The DHCP |
| server SHOULD check 'ciaddr' for correctness before replying to |
| the DHCPREQUEST. |
| |
| The DHCPREQUEST from a REBINDING client is intended to accommodate |
| sites that have multiple DHCP servers and a mechanism for |
| maintaining consistency among leases managed by multiple servers. |
| A DHCP server MAY extend a client's lease only if it has local |
| administrative authority to do so. |
| */ |
| if (!requested_ip_opt) { |
| requested_nip = packet.ciaddr; |
| if (requested_nip == 0) { |
| log1("no requested IP and no ciaddr, ignoring"); |
| break; |
| } |
| } |
| if (lease && requested_nip == lease->lease_nip) { |
| /* client requested or configured IP matches the lease. |
| * ACK it, and bump lease expiration time. */ |
| send_ACK(&packet, lease->lease_nip); |
| break; |
| } |
| /* No lease for this MAC, or lease IP != requested IP */ |
| |
| if (server_id_opt /* client is in SELECTING state */ |
| || requested_ip_opt /* client is in INIT-REBOOT state */ |
| ) { |
| /* "No, we don't have this IP for you" */ |
| send_NAK(&packet); |
| } /* else: client is in RENEWING or REBINDING, do not answer */ |
| |
| break; |
| |
| case DHCPDECLINE: |
| /* RFC 2131: |
| * "If the server receives a DHCPDECLINE message, |
| * the client has discovered through some other means |
| * that the suggested network address is already |
| * in use. The server MUST mark the network address |
| * as not available and SHOULD notify the local |
| * sysadmin of a possible configuration problem." |
| * |
| * SERVER_ID must be present, |
| * REQUESTED_IP must be present, |
| * chaddr must be filled in, |
| * ciaddr must be 0 (we do not check this) |
| */ |
| log1("received %s", "DECLINE"); |
| if (server_id_opt |
| && requested_ip_opt |
| && lease /* chaddr matches this lease */ |
| && requested_nip == lease->lease_nip |
| ) { |
| memset(lease->lease_mac, 0, sizeof(lease->lease_mac)); |
| lease->expires = time(NULL) + server_config.decline_time; |
| } |
| break; |
| |
| case DHCPRELEASE: |
| /* "Upon receipt of a DHCPRELEASE message, the server |
| * marks the network address as not allocated." |
| * |
| * SERVER_ID must be present, |
| * REQUESTED_IP must not be present (we do not check this), |
| * chaddr must be filled in, |
| * ciaddr must be filled in |
| */ |
| log1("received %s", "RELEASE"); |
| if (server_id_opt |
| && lease /* chaddr matches this lease */ |
| && packet.ciaddr == lease->lease_nip |
| ) { |
| lease->expires = time(NULL); |
| } |
| break; |
| |
| case DHCPINFORM: |
| log1("received %s", "INFORM"); |
| send_inform(&packet); |
| break; |
| } |
| } |
| ret0: |
| retval = 0; |
| ret: |
| /*if (server_config.pidfile) - server_config.pidfile is never NULL */ |
| remove_pidfile(server_config.pidfile); |
| return retval; |
| } |