/* vi: set sw=4 ts=4: */ /* * udhcp DHCP client * * Russ Dill 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. */ #include /* Override ENABLE_FEATURE_PIDFILE - ifupdown needs our pidfile to always exist */ #define WANT_PIDFILE 1 #include "common.h" #include "dhcpd.h" #include "dhcpc.h" #include "options.h" #include #if (defined(__GLIBC__) && __GLIBC__ >= 2 && __GLIBC_MINOR__ >= 1) || defined(_NEWLIB_VERSION) # include # include #else # include # include #endif #include static int sockfd = -1; #define LISTEN_NONE 0 #define LISTEN_KERNEL 1 #define LISTEN_RAW 2 static smallint listen_mode; /* initial state: (re)start DHCP negotiation */ #define INIT_SELECTING 0 /* discover was sent, DHCPOFFER reply received */ #define REQUESTING 1 /* select/renew was sent, DHCPACK reply received */ #define BOUND 2 /* half of lease passed, want to renew it by sending unicast renew requests */ #define RENEWING 3 /* renew requests were not answered, lease is almost over, send broadcast renew */ #define REBINDING 4 /* manually requested renew (SIGUSR1) */ #define RENEW_REQUESTED 5 /* release, possibly manually requested (SIGUSR2) */ #define RELEASED 6 static smallint state; /* struct client_config_t client_config is in bb_common_bufsiz1 */ /* Create a random xid */ static ALWAYS_INLINE uint32_t random_xid(void) { return rand(); } /* Initialize the packet with the proper defaults */ static void init_packet(struct dhcp_packet *packet, char type) { udhcp_init_header(packet, type); memcpy(packet->chaddr, client_config.client_mac, 6); if (client_config.clientid) add_option_string(packet->options, client_config.clientid); if (client_config.hostname) add_option_string(packet->options, client_config.hostname); if (client_config.fqdn) add_option_string(packet->options, client_config.fqdn); if (type != DHCPDECLINE && type != DHCPRELEASE && client_config.vendorclass ) { add_option_string(packet->options, client_config.vendorclass); } } /* Add a parameter request list for stubborn DHCP servers. Pull the data * from the struct in options.c. Don't do bounds checking here because it * goes towards the head of the packet. */ static void add_param_req_option(struct dhcp_packet *packet) { uint8_t c; int end = end_option(packet->options); int i, len = 0; for (i = 0; (c = dhcp_options[i].code) != 0; i++) { if (( (dhcp_options[i].flags & OPTION_REQ) && !client_config.no_default_options ) || (client_config.opt_mask[c >> 3] & (1 << (c & 7))) ) { packet->options[end + OPT_DATA + len] = c; len++; } } if (len) { packet->options[end + OPT_CODE] = DHCP_PARAM_REQ; packet->options[end + OPT_LEN] = len; packet->options[end + OPT_DATA + len] = DHCP_END; } } /* RFC 2131 * 4.4.4 Use of broadcast and unicast * * The DHCP client broadcasts DHCPDISCOVER, DHCPREQUEST and DHCPINFORM * messages, unless the client knows the address of a DHCP server. * The client unicasts DHCPRELEASE messages to the server. Because * the client is declining the use of the IP address supplied by the server, * the client broadcasts DHCPDECLINE messages. * * When the DHCP client knows the address of a DHCP server, in either * INIT or REBOOTING state, the client may use that address * in the DHCPDISCOVER or DHCPREQUEST rather than the IP broadcast address. * The client may also use unicast to send DHCPINFORM messages * to a known DHCP server. If the client receives no response to DHCP * messages sent to the IP address of a known DHCP server, the DHCP * client reverts to using the IP broadcast address. */ static int raw_bcast_from_client_config_ifindex(struct dhcp_packet *packet) { return udhcp_send_raw_packet(packet, /*src*/ INADDR_ANY, CLIENT_PORT, /*dst*/ INADDR_BROADCAST, SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex); } /* Broadcast a DHCP discover packet to the network, with an optionally requested IP */ static int send_discover(uint32_t xid, uint32_t requested) { struct dhcp_packet packet; init_packet(&packet, DHCPDISCOVER); packet.xid = xid; if (requested) add_simple_option(packet.options, DHCP_REQUESTED_IP, requested); /* Explicitly saying that we want RFC-compliant packets helps * some buggy DHCP servers to NOT send bigger packets */ add_simple_option(packet.options, DHCP_MAX_SIZE, htons(576)); add_param_req_option(&packet); bb_info_msg("Sending discover..."); return raw_bcast_from_client_config_ifindex(&packet); } /* Broadcast a DHCP request message */ /* RFC 2131 3.1 paragraph 3: * "The client _broadcasts_ a DHCPREQUEST message..." */ static int send_select(uint32_t xid, uint32_t server, uint32_t requested) { struct dhcp_packet packet; struct in_addr addr; init_packet(&packet, DHCPREQUEST); packet.xid = xid; add_simple_option(packet.options, DHCP_REQUESTED_IP, requested); add_simple_option(packet.options, DHCP_SERVER_ID, server); add_param_req_option(&packet); addr.s_addr = requested; bb_info_msg("Sending select for %s...", inet_ntoa(addr)); return raw_bcast_from_client_config_ifindex(&packet); } /* Unicast or broadcast a DHCP renew message */ static int send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr) { struct dhcp_packet packet; init_packet(&packet, DHCPREQUEST); packet.xid = xid; packet.ciaddr = ciaddr; add_param_req_option(&packet); bb_info_msg("Sending renew..."); if (server) return udhcp_send_kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT); return raw_bcast_from_client_config_ifindex(&packet); } #if ENABLE_FEATURE_UDHCPC_ARPING /* Broadcast a DHCP decline message */ static int send_decline(uint32_t xid, uint32_t server, uint32_t requested) { struct dhcp_packet packet; init_packet(&packet, DHCPDECLINE); packet.xid = xid; add_simple_option(packet.options, DHCP_REQUESTED_IP, requested); add_simple_option(packet.options, DHCP_SERVER_ID, server); bb_info_msg("Sending decline..."); return raw_bcast_from_client_config_ifindex(&packet); } #endif /* Unicast a DHCP release message */ static int send_release(uint32_t server, uint32_t ciaddr) { struct dhcp_packet packet; init_packet(&packet, DHCPRELEASE); packet.xid = random_xid(); packet.ciaddr = ciaddr; add_simple_option(packet.options, DHCP_SERVER_ID, server); bb_info_msg("Sending release..."); return udhcp_send_kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT); } /* Returns -1 on errors that are fatal for the socket, -2 for those that aren't */ static NOINLINE int udhcp_recv_raw_packet(struct dhcp_packet *dhcp_pkt, int fd) { int bytes; struct ip_udp_dhcp_packet packet; uint16_t check; memset(&packet, 0, sizeof(packet)); bytes = safe_read(fd, &packet, sizeof(packet)); if (bytes < 0) { log1("Packet read error, ignoring"); /* NB: possible down interface, etc. Caller should pause. */ return bytes; /* returns -1 */ } if (bytes < (int) (sizeof(packet.ip) + sizeof(packet.udp))) { log1("Packet is too short, ignoring"); return -2; } if (bytes < ntohs(packet.ip.tot_len)) { /* packet is bigger than sizeof(packet), we did partial read */ log1("Oversized packet, ignoring"); return -2; } /* ignore any extra garbage bytes */ bytes = ntohs(packet.ip.tot_len); /* make sure its the right packet for us, and that it passes sanity checks */ if (packet.ip.protocol != IPPROTO_UDP || packet.ip.version != IPVERSION || packet.ip.ihl != (sizeof(packet.ip) >> 2) || packet.udp.dest != htons(CLIENT_PORT) /* || bytes > (int) sizeof(packet) - can't happen */ || ntohs(packet.udp.len) != (uint16_t)(bytes - sizeof(packet.ip)) ) { log1("Unrelated/bogus packet, ignoring"); return -2; } /* verify IP checksum */ check = packet.ip.check; packet.ip.check = 0; if (check != udhcp_checksum(&packet.ip, sizeof(packet.ip))) { log1("Bad IP header checksum, ignoring"); return -2; } /* verify UDP checksum. IP header has to be modified for this */ memset(&packet.ip, 0, offsetof(struct iphdr, protocol)); /* ip.xx fields which are not memset: protocol, check, saddr, daddr */ packet.ip.tot_len = packet.udp.len; /* yes, this is needed */ check = packet.udp.check; packet.udp.check = 0; if (check && check != udhcp_checksum(&packet, bytes)) { log1("Packet with bad UDP checksum received, ignoring"); return -2; } memcpy(dhcp_pkt, &packet.data, bytes - (sizeof(packet.ip) + sizeof(packet.udp))); if (dhcp_pkt->cookie != htonl(DHCP_MAGIC)) { bb_info_msg("Packet with bad magic, ignoring"); return -2; } log1("Got valid DHCP packet"); udhcp_dump_packet(dhcp_pkt); return bytes - (sizeof(packet.ip) + sizeof(packet.udp)); } static int udhcp_raw_socket(int ifindex) { int fd; struct sockaddr_ll sock; /* * Comment: * * I've selected not to see LL header, so BPF doesn't see it, too. * The filter may also pass non-IP and non-ARP packets, but we do * a more complete check when receiving the message in userspace. * * and filter shamelessly stolen from: * * http://www.flamewarmaster.de/software/dhcpclient/ * * There are a few other interesting ideas on that page (look under * "Motivation"). Use of netlink events is most interesting. Think * of various network servers listening for events and reconfiguring. * That would obsolete sending HUP signals and/or make use of restarts. * * Copyright: 2006, 2007 Stefan Rompf . * License: GPL v2. * * TODO: make conditional? */ #define SERVER_AND_CLIENT_PORTS ((67 << 16) + 68) static const struct sock_filter filter_instr[] = { /* check for udp */ BPF_STMT(BPF_LD|BPF_B|BPF_ABS, 9), BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, IPPROTO_UDP, 2, 0), /* L5, L1, is UDP? */ /* ugly check for arp on ethernet-like and IPv4 */ BPF_STMT(BPF_LD|BPF_W|BPF_ABS, 2), /* L1: */ BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, 0x08000604, 3, 4), /* L3, L4 */ /* skip IP header */ BPF_STMT(BPF_LDX|BPF_B|BPF_MSH, 0), /* L5: */ /* check udp source and destination ports */ BPF_STMT(BPF_LD|BPF_W|BPF_IND, 0), BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, SERVER_AND_CLIENT_PORTS, 0, 1), /* L3, L4 */ /* returns */ BPF_STMT(BPF_RET|BPF_K, 0x0fffffff ), /* L3: pass */ BPF_STMT(BPF_RET|BPF_K, 0), /* L4: reject */ }; static const struct sock_fprog filter_prog = { .len = sizeof(filter_instr) / sizeof(filter_instr[0]), /* casting const away: */ .filter = (struct sock_filter *) filter_instr, }; log1("Opening raw socket on ifindex %d", ifindex); //log2? fd = xsocket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP)); log1("Got raw socket fd %d", fd); //log2? if (SERVER_PORT == 67 && CLIENT_PORT == 68) { /* Use only if standard ports are in use */ /* Ignoring error (kernel may lack support for this) */ if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter_prog, sizeof(filter_prog)) >= 0) log1("Attached filter to raw socket fd %d", fd); // log? } sock.sll_family = AF_PACKET; sock.sll_protocol = htons(ETH_P_IP); sock.sll_ifindex = ifindex; xbind(fd, (struct sockaddr *) &sock, sizeof(sock)); log1("Created raw socket"); return fd; } /* just a little helper */ static void change_listen_mode(int new_mode) { log1("Entering listen mode: %s", new_mode != LISTEN_NONE ? (new_mode == LISTEN_KERNEL ? "kernel" : "raw") : "none" ); listen_mode = new_mode; if (sockfd >= 0) { close(sockfd); sockfd = -1; } if (new_mode == LISTEN_KERNEL) sockfd = udhcp_listen_socket(/*INADDR_ANY,*/ CLIENT_PORT, client_config.interface); else if (new_mode != LISTEN_NONE) sockfd = udhcp_raw_socket(client_config.ifindex); /* else LISTEN_NONE: sockfd stays closed */ } /* perform a renew */ static void perform_renew(void) { bb_info_msg("Performing a DHCP renew"); switch (state) { case BOUND: change_listen_mode(LISTEN_KERNEL); case RENEWING: case REBINDING: state = RENEW_REQUESTED; break; case RENEW_REQUESTED: /* impatient are we? fine, square 1 */ udhcp_run_script(NULL, "deconfig"); case REQUESTING: case RELEASED: change_listen_mode(LISTEN_RAW); state = INIT_SELECTING; break; case INIT_SELECTING: break; } } /* perform a release */ static void perform_release(uint32_t requested_ip, uint32_t server_addr) { char buffer[sizeof("255.255.255.255")]; struct in_addr temp_addr; /* send release packet */ if (state == BOUND || state == RENEWING || state == REBINDING) { temp_addr.s_addr = server_addr; strcpy(buffer, inet_ntoa(temp_addr)); temp_addr.s_addr = requested_ip; bb_info_msg("Unicasting a release of %s to %s", inet_ntoa(temp_addr), buffer); send_release(server_addr, requested_ip); /* unicast */ udhcp_run_script(NULL, "deconfig"); } bb_info_msg("Entering released state"); change_listen_mode(LISTEN_NONE); state = RELEASED; } #if BB_MMU static void client_background(void) { bb_daemonize(0); logmode &= ~LOGMODE_STDIO; /* rewrite pidfile, as our pid is different now */ write_pidfile(client_config.pidfile); } #endif static uint8_t* alloc_dhcp_option(int code, const char *str, int extra) { uint8_t *storage; int len = strnlen(str, 255); storage = xzalloc(len + extra + OPT_DATA); storage[OPT_CODE] = code; storage[OPT_LEN] = len + extra; memcpy(storage + extra + OPT_DATA, str, len); return storage; } int udhcpc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; int udhcpc_main(int argc UNUSED_PARAM, char **argv) { uint8_t *temp, *message; const char *str_c, *str_V, *str_h, *str_F, *str_r; IF_FEATURE_UDHCP_PORT(char *str_P;) llist_t *list_O = NULL; int tryagain_timeout = 20; int discover_timeout = 3; int discover_retries = 3; uint32_t server_addr = server_addr; /* for compiler */ uint32_t requested_ip = 0; uint32_t xid = 0; uint32_t lease_seconds = 0; /* can be given as 32-bit quantity */ int packet_num; int timeout; /* must be signed */ unsigned already_waited_sec; unsigned opt; int max_fd; int retval; struct timeval tv; struct dhcp_packet packet; fd_set rfds; #if ENABLE_LONG_OPTS static const char udhcpc_longopts[] ALIGN1 = "clientid\0" Required_argument "c" "clientid-none\0" No_argument "C" "vendorclass\0" Required_argument "V" "hostname\0" Required_argument "H" "fqdn\0" Required_argument "F" "interface\0" Required_argument "i" "now\0" No_argument "n" "pidfile\0" Required_argument "p" "quit\0" No_argument "q" "release\0" No_argument "R" "request\0" Required_argument "r" "script\0" Required_argument "s" "timeout\0" Required_argument "T" "version\0" No_argument "v" "retries\0" Required_argument "t" "tryagain\0" Required_argument "A" "syslog\0" No_argument "S" "request-option\0" Required_argument "O" "no-default-options\0" No_argument "o" "foreground\0" No_argument "f" "background\0" No_argument "b" IF_FEATURE_UDHCPC_ARPING("arping\0" No_argument "a") IF_FEATURE_UDHCP_PORT("client-port\0" Required_argument "P") ; #endif enum { OPT_c = 1 << 0, OPT_C = 1 << 1, OPT_V = 1 << 2, OPT_H = 1 << 3, OPT_h = 1 << 4, OPT_F = 1 << 5, OPT_i = 1 << 6, OPT_n = 1 << 7, OPT_p = 1 << 8, OPT_q = 1 << 9, OPT_R = 1 << 10, OPT_r = 1 << 11, OPT_s = 1 << 12, OPT_T = 1 << 13, OPT_t = 1 << 14, OPT_S = 1 << 15, OPT_A = 1 << 16, OPT_O = 1 << 17, OPT_o = 1 << 18, OPT_f = 1 << 19, /* The rest has variable bit positions, need to be clever */ OPTBIT_f = 19, USE_FOR_MMU( OPTBIT_b,) IF_FEATURE_UDHCPC_ARPING(OPTBIT_a,) IF_FEATURE_UDHCP_PORT( OPTBIT_P,) USE_FOR_MMU( OPT_b = 1 << OPTBIT_b,) IF_FEATURE_UDHCPC_ARPING(OPT_a = 1 << OPTBIT_a,) IF_FEATURE_UDHCP_PORT( OPT_P = 1 << OPTBIT_P,) }; /* Default options. */ IF_FEATURE_UDHCP_PORT(SERVER_PORT = 67;) IF_FEATURE_UDHCP_PORT(CLIENT_PORT = 68;) client_config.interface = "eth0"; client_config.script = DEFAULT_SCRIPT; str_V = "udhcp "BB_VER; /* Parse command line */ /* Cc: mutually exclusive; O: list; -T,-t,-A take numeric param */ opt_complementary = "c--C:C--c:O::T+:t+:A+" #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1 ":vv" #endif ; IF_LONG_OPTS(applet_long_options = udhcpc_longopts;) opt = getopt32(argv, "c:CV:H:h:F:i:np:qRr:s:T:t:SA:O:of" USE_FOR_MMU("b") IF_FEATURE_UDHCPC_ARPING("a") IF_FEATURE_UDHCP_PORT("P:") "v" , &str_c, &str_V, &str_h, &str_h, &str_F , &client_config.interface, &client_config.pidfile, &str_r /* i,p */ , &client_config.script /* s */ , &discover_timeout, &discover_retries, &tryagain_timeout /* T,t,A */ , &list_O IF_FEATURE_UDHCP_PORT(, &str_P) #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1 , &dhcp_verbose #endif ); if (opt & (OPT_h|OPT_H)) client_config.hostname = alloc_dhcp_option(DHCP_HOST_NAME, str_h, 0); if (opt & OPT_F) { /* FQDN option format: [0x51][len][flags][0][0] */ client_config.fqdn = alloc_dhcp_option(DHCP_FQDN, str_F, 3); /* Flag bits: 0000NEOS * S: 1 = Client requests server to update A RR in DNS as well as PTR * O: 1 = Server indicates to client that DNS has been updated regardless * E: 1 = Name is in DNS format, i.e. <4>host<6>domain<3>com<0>, * not "host.domain.com". Format 0 is obsolete. * N: 1 = Client requests server to not update DNS (S must be 0 then) * Two [0] bytes which follow are deprecated and must be 0. */ client_config.fqdn[OPT_DATA + 0] = 0x1; /*client_config.fqdn[OPT_DATA + 1] = 0; - xzalloc did it */ /*client_config.fqdn[OPT_DATA + 2] = 0; */ } if (opt & OPT_r) requested_ip = inet_addr(str_r); #if ENABLE_FEATURE_UDHCP_PORT if (opt & OPT_P) { CLIENT_PORT = xatou16(str_P); SERVER_PORT = CLIENT_PORT - 1; } #endif if (opt & OPT_o) client_config.no_default_options = 1; while (list_O) { char *optstr = llist_pop(&list_O); int n = index_in_strings(dhcp_option_strings, optstr); if (n < 0) bb_error_msg_and_die("unknown option '%s'", optstr); n = dhcp_options[n].code; client_config.opt_mask[n >> 3] |= 1 << (n & 7); } if (udhcp_read_interface(client_config.interface, &client_config.ifindex, NULL, client_config.client_mac) ) { return 1; } if (opt & OPT_c) { client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, str_c, 0); } else if (!(opt & OPT_C)) { /* not set and not suppressed, set the default client ID */ client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, "", 7); client_config.clientid[OPT_DATA] = 1; /* type: ethernet */ memcpy(client_config.clientid + OPT_DATA+1, client_config.client_mac, 6); } if (str_V[0] != '\0') client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, str_V, 0); #if !BB_MMU /* on NOMMU reexec (i.e., background) early */ if (!(opt & OPT_f)) { bb_daemonize_or_rexec(0 /* flags */, argv); logmode = LOGMODE_NONE; } #endif if (opt & OPT_S) { openlog(applet_name, LOG_PID, LOG_DAEMON); logmode |= LOGMODE_SYSLOG; } /* 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(client_config.pidfile); /* Goes to stdout (unless NOMMU) and possibly syslog */ bb_info_msg("%s (v"BB_VER") started", applet_name); /* Set up the signal pipe */ udhcp_sp_setup(); /* We want random_xid to be random... */ srand(monotonic_us()); state = INIT_SELECTING; udhcp_run_script(NULL, "deconfig"); change_listen_mode(LISTEN_RAW); packet_num = 0; timeout = 0; already_waited_sec = 0; /* Main event loop. select() waits on signal pipe and possibly * on sockfd. * "continue" statements in code below jump to the top of the loop. */ for (;;) { /* silence "uninitialized!" warning */ unsigned timestamp_before_wait = timestamp_before_wait; //bb_error_msg("sockfd:%d, listen_mode:%d", sockfd, listen_mode); /* Was opening raw or udp socket here * if (listen_mode != LISTEN_NONE && sockfd < 0), * but on fast network renew responses return faster * than we open sockets. Thus this code is moved * to change_listen_mode(). Thus we open listen socket * BEFORE we send renew request (see "case BOUND:"). */ max_fd = udhcp_sp_fd_set(&rfds, sockfd); tv.tv_sec = timeout - already_waited_sec; tv.tv_usec = 0; retval = 0; /* If we already timed out, fall through with retval = 0, else... */ if ((int)tv.tv_sec > 0) { timestamp_before_wait = (unsigned)monotonic_sec(); log1("Waiting on select..."); retval = select(max_fd + 1, &rfds, NULL, NULL, &tv); if (retval < 0) { /* EINTR? A signal was caught, don't panic */ if (errno == EINTR) { already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait; continue; } /* Else: an error occured, panic! */ bb_perror_msg_and_die("select"); } } /* If timeout dropped to zero, time to become active: * resend discover/renew/whatever */ if (retval == 0) { /* We will restart the wait in any case */ already_waited_sec = 0; switch (state) { case INIT_SELECTING: if (packet_num < discover_retries) { if (packet_num == 0) xid = random_xid(); /* broadcast */ send_discover(xid, requested_ip); timeout = discover_timeout; packet_num++; continue; } leasefail: udhcp_run_script(NULL, "leasefail"); #if BB_MMU /* -b is not supported on NOMMU */ if (opt & OPT_b) { /* background if no lease */ bb_info_msg("No lease, forking to background"); client_background(); /* do not background again! */ opt = ((opt & ~OPT_b) | OPT_f); } else #endif if (opt & OPT_n) { /* abort if no lease */ bb_info_msg("No lease, failing"); retval = 1; goto ret; } /* wait before trying again */ timeout = tryagain_timeout; packet_num = 0; continue; case REQUESTING: if (packet_num < discover_retries) { /* send broadcast select packet */ send_select(xid, server_addr, requested_ip); timeout = discover_timeout; packet_num++; continue; } /* Timed out, go back to init state. * "discover...select...discover..." loops * were seen in the wild. Treat them similarly * to "no response to discover" case */ change_listen_mode(LISTEN_RAW); state = INIT_SELECTING; goto leasefail; case BOUND: /* 1/2 lease passed, enter renewing state */ state = RENEWING; change_listen_mode(LISTEN_KERNEL); log1("Entering renew state"); /* fall right through */ case RENEW_REQUESTED: /* manual (SIGUSR1) renew */ case_RENEW_REQUESTED: case RENEWING: if (timeout > 60) { /* send an unicast renew request */ /* Sometimes observed to fail (EADDRNOTAVAIL) to bind * a new UDP socket for sending inside send_renew. * I hazard to guess existing listening socket * is somehow conflicting with it, but why is it * not deterministic then?! Strange. * Anyway, it does recover by eventually failing through * into INIT_SELECTING state. */ send_renew(xid, server_addr, requested_ip); timeout >>= 1; continue; } /* Timed out, enter rebinding state */ log1("Entering rebinding state"); state = REBINDING; /* fall right through */ case REBINDING: /* Switch to bcast receive */ change_listen_mode(LISTEN_RAW); /* Lease is *really* about to run out, * try to find DHCP server using broadcast */ if (timeout > 0) { /* send a broadcast renew request */ send_renew(xid, 0 /*INADDR_ANY*/, requested_ip); timeout >>= 1; continue; } /* Timed out, enter init state */ bb_info_msg("Lease lost, entering init state"); udhcp_run_script(NULL, "deconfig"); state = INIT_SELECTING; /*timeout = 0; - already is */ packet_num = 0; continue; /* case RELEASED: */ } /* yah, I know, *you* say it would never happen */ timeout = INT_MAX; continue; /* back to main loop */ } /* if select timed out */ /* select() didn't timeout, something happened */ /* Is it a signal? */ /* note: udhcp_sp_read checks FD_ISSET before reading */ switch (udhcp_sp_read(&rfds)) { case SIGUSR1: perform_renew(); if (state == RENEW_REQUESTED) goto case_RENEW_REQUESTED; /* Start things over */ packet_num = 0; /* Kill any timeouts, user wants this to hurry along */ timeout = 0; continue; case SIGUSR2: perform_release(requested_ip, server_addr); timeout = INT_MAX; continue; case SIGTERM: bb_info_msg("Received SIGTERM"); if (opt & OPT_R) /* release on quit */ perform_release(requested_ip, server_addr); goto ret0; } /* Is it a packet? */ if (listen_mode == LISTEN_NONE || !FD_ISSET(sockfd, &rfds)) continue; /* no */ { int len; /* A packet is ready, read it */ if (listen_mode == LISTEN_KERNEL) len = udhcp_recv_kernel_packet(&packet, sockfd); else len = udhcp_recv_raw_packet(&packet, sockfd); if (len == -1) { /* Error is severe, reopen socket */ bb_info_msg("Read error: %s, reopening socket", strerror(errno)); sleep(discover_timeout); /* 3 seconds by default */ change_listen_mode(listen_mode); /* just close and reopen */ } /* If this packet will turn out to be unrelated/bogus, * we will go back and wait for next one. * Be sure timeout is properly decreased. */ already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait; if (len < 0) continue; } if (packet.xid != xid) { log1("xid %x (our is %x), ignoring packet", (unsigned)packet.xid, (unsigned)xid); continue; } /* Ignore packets that aren't for us */ if (packet.hlen != 6 || memcmp(packet.chaddr, client_config.client_mac, 6) ) { //FIXME: need to also check that last 10 bytes are zero log1("chaddr does not match, ignoring packet"); // log2? continue; } message = get_option(&packet, DHCP_MESSAGE_TYPE); if (message == NULL) { bb_error_msg("no message type option, ignoring packet"); continue; } switch (state) { case INIT_SELECTING: /* Must be a DHCPOFFER to one of our xid's */ if (*message == DHCPOFFER) { /* TODO: why we don't just fetch server's IP from IP header? */ temp = get_option(&packet, DHCP_SERVER_ID); if (!temp) { bb_error_msg("no server ID in message"); continue; /* still selecting - this server looks bad */ } /* it IS unaligned sometimes, don't "optimize" */ move_from_unaligned32(server_addr, temp); xid = packet.xid; requested_ip = packet.yiaddr; /* enter requesting state */ state = REQUESTING; timeout = 0; packet_num = 0; already_waited_sec = 0; } continue; case REQUESTING: case RENEWING: case RENEW_REQUESTED: case REBINDING: if (*message == DHCPACK) { temp = get_option(&packet, DHCP_LEASE_TIME); if (!temp) { bb_error_msg("no lease time with ACK, using 1 hour lease"); lease_seconds = 60 * 60; } else { /* it IS unaligned sometimes, don't "optimize" */ move_from_unaligned32(lease_seconds, temp); lease_seconds = ntohl(lease_seconds); lease_seconds &= 0x0fffffff; /* paranoia: must not be prone to overflows */ if (lease_seconds < 10) /* and not too small */ lease_seconds = 10; } #if ENABLE_FEATURE_UDHCPC_ARPING if (opt & OPT_a) { /* RFC 2131 3.1 paragraph 5: * "The client receives the DHCPACK message with configuration * parameters. The client SHOULD perform a final check on the * parameters (e.g., ARP for allocated network address), and notes * the duration of the lease specified in the DHCPACK message. At this * point, the client is configured. If the client detects that the * address is already in use (e.g., through the use of ARP), * the client MUST send a DHCPDECLINE message to the server and restarts * the configuration process..." */ if (!arpping(packet.yiaddr, NULL, (uint32_t) 0, client_config.client_mac, client_config.interface) ) { bb_info_msg("Offered address is in use " "(got ARP reply), declining"); send_decline(xid, server_addr, packet.yiaddr); if (state != REQUESTING) udhcp_run_script(NULL, "deconfig"); change_listen_mode(LISTEN_RAW); state = INIT_SELECTING; requested_ip = 0; timeout = tryagain_timeout; packet_num = 0; already_waited_sec = 0; continue; /* back to main loop */ } } #endif /* enter bound state */ timeout = lease_seconds / 2; { struct in_addr temp_addr; temp_addr.s_addr = packet.yiaddr; bb_info_msg("Lease of %s obtained, lease time %u", inet_ntoa(temp_addr), (unsigned)lease_seconds); } requested_ip = packet.yiaddr; udhcp_run_script(&packet, state == REQUESTING ? "bound" : "renew"); state = BOUND; change_listen_mode(LISTEN_NONE); if (opt & OPT_q) { /* quit after lease */ if (opt & OPT_R) /* release on quit */ perform_release(requested_ip, server_addr); goto ret0; } /* future renew failures should not exit (JM) */ opt &= ~OPT_n; #if BB_MMU /* NOMMU case backgrounded earlier */ if (!(opt & OPT_f)) { client_background(); /* do not background again! */ opt = ((opt & ~OPT_b) | OPT_f); } #endif already_waited_sec = 0; continue; /* back to main loop */ } if (*message == DHCPNAK) { /* return to init state */ bb_info_msg("Received DHCP NAK"); udhcp_run_script(&packet, "nak"); if (state != REQUESTING) udhcp_run_script(NULL, "deconfig"); change_listen_mode(LISTEN_RAW); sleep(3); /* avoid excessive network traffic */ state = INIT_SELECTING; requested_ip = 0; timeout = 0; packet_num = 0; already_waited_sec = 0; } continue; /* case BOUND: - ignore all packets */ /* case RELEASED: - ignore all packets */ } /* back to main loop */ } /* for (;;) - main loop ends */ ret0: retval = 0; ret: /*if (client_config.pidfile) - remove_pidfile has its own check */ remove_pidfile(client_config.pidfile); return retval; }