/* vi: set sw=4 ts=4: */ /* * udhcp 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 #include #include /* "struct client_config_t client_config" is in bb_common_bufsiz1 */ #if ENABLE_LONG_OPTS static const char udhcpc_longopts[] ALIGN1 = "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" "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" "broadcast\0" No_argument "B" IF_FEATURE_UDHCPC_ARPING("arping\0" No_argument "a") IF_FEATURE_UDHCP_PORT("client-port\0" Required_argument "P") ; #endif /* Must match getopt32 option string order */ enum { OPT_C = 1 << 0, OPT_V = 1 << 1, OPT_H = 1 << 2, OPT_h = 1 << 3, OPT_F = 1 << 4, OPT_i = 1 << 5, OPT_n = 1 << 6, OPT_p = 1 << 7, OPT_q = 1 << 8, OPT_R = 1 << 9, OPT_r = 1 << 10, OPT_s = 1 << 11, OPT_T = 1 << 12, OPT_t = 1 << 13, OPT_S = 1 << 14, OPT_A = 1 << 15, OPT_O = 1 << 16, OPT_o = 1 << 17, OPT_x = 1 << 18, OPT_f = 1 << 19, OPT_B = 1 << 20, /* The rest has variable bit positions, need to be clever */ OPTBIT_B = 20, 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,) }; /*** Script execution code ***/ /* get a rough idea of how long an option will be (rounding up...) */ static const uint8_t len_of_option_as_string[] = { [OPTION_IP ] = sizeof("255.255.255.255 "), [OPTION_IP_PAIR ] = sizeof("255.255.255.255 ") * 2, [OPTION_STATIC_ROUTES ] = sizeof("255.255.255.255/32 255.255.255.255 "), [OPTION_6RD ] = sizeof("32 128 ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff 255.255.255.255 "), [OPTION_STRING ] = 1, #if ENABLE_FEATURE_UDHCP_RFC3397 [OPTION_DNS_STRING ] = 1, /* unused */ /* Hmmm, this severely overestimates size if SIP_SERVERS option * is in domain name form: N-byte option in binary form * mallocs ~16*N bytes. But it is freed almost at once. */ [OPTION_SIP_SERVERS ] = sizeof("255.255.255.255 "), #endif // [OPTION_BOOLEAN ] = sizeof("yes "), [OPTION_U8 ] = sizeof("255 "), [OPTION_U16 ] = sizeof("65535 "), // [OPTION_S16 ] = sizeof("-32768 "), [OPTION_U32 ] = sizeof("4294967295 "), [OPTION_S32 ] = sizeof("-2147483684 "), }; /* note: ip is a pointer to an IP in network order, possibly misaliged */ static int sprint_nip(char *dest, const char *pre, const uint8_t *ip) { return sprintf(dest, "%s%u.%u.%u.%u", pre, ip[0], ip[1], ip[2], ip[3]); } /* really simple implementation, just count the bits */ static int mton(uint32_t mask) { int i = 0; mask = ntohl(mask); /* 111110000-like bit pattern */ while (mask) { i++; mask <<= 1; } return i; } /* Create "opt_name=opt_value" string */ static NOINLINE char *xmalloc_optname_optval(uint8_t *option, const struct dhcp_optflag *optflag, const char *opt_name) { unsigned upper_length; int len, type, optlen; char *dest, *ret; /* option points to OPT_DATA, need to go back to get OPT_LEN */ len = option[-OPT_DATA + OPT_LEN]; type = optflag->flags & OPTION_TYPE_MASK; optlen = dhcp_option_lengths[type]; upper_length = len_of_option_as_string[type] * ((unsigned)(len + optlen - 1) / (unsigned)optlen); dest = ret = xmalloc(upper_length + strlen(opt_name) + 2); dest += sprintf(ret, "%s=", opt_name); while (len >= optlen) { switch (type) { case OPTION_IP: case OPTION_IP_PAIR: dest += sprint_nip(dest, "", option); if (type == OPTION_IP) break; dest += sprint_nip(dest, "/", option + 4); break; // case OPTION_BOOLEAN: // dest += sprintf(dest, *option ? "yes" : "no"); // break; case OPTION_U8: dest += sprintf(dest, "%u", *option); break; // case OPTION_S16: case OPTION_U16: { uint16_t val_u16; move_from_unaligned16(val_u16, option); dest += sprintf(dest, "%u", ntohs(val_u16)); break; } case OPTION_S32: case OPTION_U32: { uint32_t val_u32; move_from_unaligned32(val_u32, option); dest += sprintf(dest, type == OPTION_U32 ? "%lu" : "%ld", (unsigned long) ntohl(val_u32)); break; } /* Note: options which use 'return' instead of 'break' * (for example, OPTION_STRING) skip the code which handles * the case of list of options. */ case OPTION_STRING: memcpy(dest, option, len); dest[len] = '\0'; return ret; case OPTION_STATIC_ROUTES: { /* Option binary format: * mask [one byte, 0..32] * ip [big endian, 0..4 bytes depending on mask] * router [big endian, 4 bytes] * may be repeated * * We convert it to a string "IP/MASK ROUTER IP2/MASK2 ROUTER2" */ const char *pfx = ""; while (len >= 1 + 4) { /* mask + 0-byte ip + router */ uint32_t nip; uint8_t *p; unsigned mask; int bytes; mask = *option++; if (mask > 32) break; len--; nip = 0; p = (void*) &nip; bytes = (mask + 7) / 8; /* 0 -> 0, 1..8 -> 1, 9..16 -> 2 etc */ while (--bytes >= 0) { *p++ = *option++; len--; } if (len < 4) break; /* print ip/mask */ dest += sprint_nip(dest, pfx, (void*) &nip); pfx = " "; dest += sprintf(dest, "/%u ", mask); /* print router */ dest += sprint_nip(dest, "", option); option += 4; len -= 4; } return ret; } case OPTION_6RD: /* Option binary format (see RFC 5969): * 0 1 2 3 * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ * | OPTION_6RD | option-length | IPv4MaskLen | 6rdPrefixLen | * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ * | 6rdPrefix | * ... (16 octets) ... * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ * ... 6rdBRIPv4Address(es) ... * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ * We convert it to a string * "IPv4MaskLen 6rdPrefixLen 6rdPrefix 6rdBRIPv4Address..." * * Sanity check: ensure that our length is at least 22 bytes, that * IPv4MaskLen <= 32, * 6rdPrefixLen <= 128, * 6rdPrefixLen + (32 - IPv4MaskLen) <= 128 * (2nd condition need no check - it follows from 1st and 3rd). * Else, return envvar with empty value ("optname=") */ if (len >= (1 + 1 + 16 + 4) && option[0] <= 32 && (option[1] + 32 - option[0]) <= 128 ) { /* IPv4MaskLen */ dest += sprintf(dest, "%u ", *option++); /* 6rdPrefixLen */ dest += sprintf(dest, "%u ", *option++); /* 6rdPrefix */ dest += sprint_nip6(dest, /* "", */ option); option += 16; len -= 1 + 1 + 16 + 4; /* "+ 4" above corresponds to the length of IPv4 addr * we consume in the loop below */ while (1) { /* 6rdBRIPv4Address(es) */ dest += sprint_nip(dest, " ", option); option += 4; len -= 4; /* do we have yet another 4+ bytes? */ if (len < 0) break; /* no */ } } return ret; #if ENABLE_FEATURE_UDHCP_RFC3397 case OPTION_DNS_STRING: /* unpack option into dest; use ret for prefix (i.e., "optname=") */ dest = dname_dec(option, len, ret); if (dest) { free(ret); return dest; } /* error. return "optname=" string */ return ret; case OPTION_SIP_SERVERS: /* Option binary format: * type: byte * type=0: domain names, dns-compressed * type=1: IP addrs */ option++; len--; if (option[-1] == 0) { dest = dname_dec(option, len, ret); if (dest) { free(ret); return dest; } } else if (option[-1] == 1) { const char *pfx = ""; while (1) { len -= 4; if (len < 0) break; dest += sprint_nip(dest, pfx, option); pfx = " "; option += 4; } } return ret; #endif } /* switch */ /* If we are here, try to format any remaining data * in the option as another, similarly-formatted option */ option += optlen; len -= optlen; // TODO: it can be a list only if (optflag->flags & OPTION_LIST). // Should we bail out/warn if we see multi-ip option which is // not allowed to be such (for example, DHCP_BROADCAST)? - if (len < optlen /* || !(optflag->flags & OPTION_LIST) */) break; *dest++ = ' '; *dest = '\0'; } /* while */ return ret; } /* put all the parameters into the environment */ static char **fill_envp(struct dhcp_packet *packet) { int envc; int i; char **envp, **curr; const char *opt_name; uint8_t *temp; uint8_t overload = 0; #define BITMAP unsigned #define BBITS (sizeof(BITMAP) * 8) #define BMASK(i) (1 << (i & (sizeof(BITMAP) * 8 - 1))) #define FOUND_OPTS(i) (found_opts[(unsigned)i / BBITS]) BITMAP found_opts[256 / BBITS]; memset(found_opts, 0, sizeof(found_opts)); /* We need 6 elements for: * "interface=IFACE" * "ip=N.N.N.N" from packet->yiaddr * "siaddr=IP" from packet->siaddr_nip (unless 0) * "boot_file=FILE" from packet->file (unless overloaded) * "sname=SERVER_HOSTNAME" from packet->sname (unless overloaded) * terminating NULL */ envc = 6; /* +1 element for each option, +2 for subnet option: */ if (packet) { /* note: do not search for "pad" (0) and "end" (255) options */ for (i = 1; i < 255; i++) { temp = udhcp_get_option(packet, i); if (temp) { if (i == DHCP_OPTION_OVERLOAD) overload = *temp; else if (i == DHCP_SUBNET) envc++; /* for $mask */ envc++; /*if (i != DHCP_MESSAGE_TYPE)*/ FOUND_OPTS(i) |= BMASK(i); } } } curr = envp = xzalloc(sizeof(envp[0]) * envc); *curr = xasprintf("interface=%s", client_config.interface); putenv(*curr++); if (!packet) return envp; /* Export BOOTP fields. Fields we don't (yet?) export: * uint8_t op; // always BOOTREPLY * uint8_t htype; // hardware address type. 1 = 10mb ethernet * uint8_t hlen; // hardware address length * uint8_t hops; // used by relay agents only * uint32_t xid; * uint16_t secs; // elapsed since client began acquisition/renewal * uint16_t flags; // only one flag so far: bcast. Never set by server * uint32_t ciaddr; // client IP (usually == yiaddr. can it be different * // if during renew server wants to give us differn IP?) * uint32_t gateway_nip; // relay agent IP address * uint8_t chaddr[16]; // link-layer client hardware address (MAC) * TODO: export gateway_nip as $giaddr? */ /* Most important one: yiaddr as $ip */ *curr = xmalloc(sizeof("ip=255.255.255.255")); sprint_nip(*curr, "ip=", (uint8_t *) &packet->yiaddr); putenv(*curr++); if (packet->siaddr_nip) { /* IP address of next server to use in bootstrap */ *curr = xmalloc(sizeof("siaddr=255.255.255.255")); sprint_nip(*curr, "siaddr=", (uint8_t *) &packet->siaddr_nip); putenv(*curr++); } if (!(overload & FILE_FIELD) && packet->file[0]) { /* watch out for invalid packets */ *curr = xasprintf("boot_file=%."DHCP_PKT_FILE_LEN_STR"s", packet->file); putenv(*curr++); } if (!(overload & SNAME_FIELD) && packet->sname[0]) { /* watch out for invalid packets */ *curr = xasprintf("sname=%."DHCP_PKT_SNAME_LEN_STR"s", packet->sname); putenv(*curr++); } /* Export known DHCP options */ opt_name = dhcp_option_strings; i = 0; while (*opt_name) { uint8_t code = dhcp_optflags[i].code; BITMAP *found_ptr = &FOUND_OPTS(code); BITMAP found_mask = BMASK(code); if (!(*found_ptr & found_mask)) goto next; *found_ptr &= ~found_mask; /* leave only unknown options */ temp = udhcp_get_option(packet, code); *curr = xmalloc_optname_optval(temp, &dhcp_optflags[i], opt_name); putenv(*curr++); if (code == DHCP_SUBNET) { /* Subnet option: make things like "$ip/$mask" possible */ uint32_t subnet; move_from_unaligned32(subnet, temp); *curr = xasprintf("mask=%u", mton(subnet)); putenv(*curr++); } next: opt_name += strlen(opt_name) + 1; i++; } /* Export unknown options */ for (i = 0; i < 256;) { BITMAP bitmap = FOUND_OPTS(i); if (!bitmap) { i += BBITS; continue; } if (bitmap & BMASK(i)) { unsigned len, ofs; temp = udhcp_get_option(packet, i); /* udhcp_get_option returns ptr to data portion, * need to go back to get len */ len = temp[-OPT_DATA + OPT_LEN]; *curr = xmalloc(sizeof("optNNN=") + 1 + len*2); ofs = sprintf(*curr, "opt%u=", i); *bin2hex(*curr + ofs, (void*) temp, len) = '\0'; putenv(*curr++); } i++; } return envp; } /* Call a script with a par file and env vars */ static void udhcp_run_script(struct dhcp_packet *packet, const char *name) { char **envp, **curr; char *argv[3]; envp = fill_envp(packet); /* call script */ log1("Executing %s %s", client_config.script, name); argv[0] = (char*) client_config.script; argv[1] = (char*) name; argv[2] = NULL; spawn_and_wait(argv); for (curr = envp; *curr; curr++) { log2(" %s", *curr); bb_unsetenv_and_free(*curr); } free(envp); } /*** Sending/receiving packets ***/ 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) { uint16_t secs; /* Fill in: op, htype, hlen, cookie fields; message type option: */ udhcp_init_header(packet, type); packet->xid = random_xid(); client_config.last_secs = monotonic_sec(); if (client_config.first_secs == 0) client_config.first_secs = client_config.last_secs; secs = client_config.last_secs - client_config.first_secs; packet->secs = htons(secs); memcpy(packet->chaddr, client_config.client_mac, 6); if (client_config.clientid) udhcp_add_binary_option(packet, client_config.clientid); } static void add_client_options(struct dhcp_packet *packet) { uint8_t c; int i, end, len; udhcp_add_simple_option(packet, DHCP_MAX_SIZE, htons(IP_UDP_DHCP_SIZE)); /* Add a "param req" option with the list of options we'd like to have * from stubborn DHCP servers. Pull the data from the struct in common.c. * No bounds checking because it goes towards the head of the packet. */ end = udhcp_end_option(packet->options); len = 0; for (i = 0; (c = dhcp_optflags[i].code) != 0; i++) { if (( (dhcp_optflags[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; } if (client_config.vendorclass) udhcp_add_binary_option(packet, client_config.vendorclass); if (client_config.hostname) udhcp_add_binary_option(packet, client_config.hostname); if (client_config.fqdn) udhcp_add_binary_option(packet, client_config.fqdn); /* Request broadcast replies if we have no IP addr */ if ((option_mask32 & OPT_B) && packet->ciaddr == 0) packet->flags |= htons(BROADCAST_FLAG); /* Add -x options if any */ { struct option_set *curr = client_config.options; while (curr) { udhcp_add_binary_option(packet, curr->data); curr = curr->next; } // if (client_config.sname) // strncpy((char*)packet->sname, client_config.sname, sizeof(packet->sname) - 1); // if (client_config.boot_file) // strncpy((char*)packet->file, client_config.boot_file, sizeof(packet->file) - 1); } // This will be needed if we remove -V VENDOR_STR in favor of // -x vendor:VENDOR_STR //if (!udhcp_find_option(packet.options, DHCP_VENDOR)) // /* not set, set the default vendor ID */ // ...add (DHCP_VENDOR, "udhcp "BB_VER) opt... } /* 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 */ /* NOINLINE: limit stack usage in caller */ static NOINLINE int send_discover(uint32_t xid, uint32_t requested) { struct dhcp_packet packet; /* Fill in: op, htype, hlen, cookie, chaddr fields, * random xid field (we override it below), * client-id option (unless -C), message type option: */ init_packet(&packet, DHCPDISCOVER); packet.xid = xid; if (requested) udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested); /* Add options: maxsize, * optionally: hostname, fqdn, vendorclass, * "param req" option according to -O, options specified with -x */ add_client_options(&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..." */ /* NOINLINE: limit stack usage in caller */ static NOINLINE int send_select(uint32_t xid, uint32_t server, uint32_t requested) { struct dhcp_packet packet; struct in_addr addr; /* * RFC 2131 4.3.2 DHCPREQUEST message * ... * If the DHCPREQUEST message contains a 'server identifier' * option, the message is in response to a DHCPOFFER message. * Otherwise, the message is a request to verify or extend an * existing lease. If the client uses a 'client identifier' * in a DHCPREQUEST message, it MUST use that same 'client identifier' * in all subsequent messages. If the client included a list * of requested parameters in a DHCPDISCOVER message, it MUST * include that list in all subsequent messages. */ /* Fill in: op, htype, hlen, cookie, chaddr fields, * random xid field (we override it below), * client-id option (unless -C), message type option: */ init_packet(&packet, DHCPREQUEST); packet.xid = xid; udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested); udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server); /* Add options: maxsize, * optionally: hostname, fqdn, vendorclass, * "param req" option according to -O, and options specified with -x */ add_client_options(&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 */ /* NOINLINE: limit stack usage in caller */ static NOINLINE int send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr) { struct dhcp_packet packet; /* * RFC 2131 4.3.2 DHCPREQUEST message * ... * 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. */ /* Fill in: op, htype, hlen, cookie, chaddr fields, * random xid field (we override it below), * client-id option (unless -C), message type option: */ init_packet(&packet, DHCPREQUEST); packet.xid = xid; packet.ciaddr = ciaddr; /* Add options: maxsize, * optionally: hostname, fqdn, vendorclass, * "param req" option according to -O, and options specified with -x */ add_client_options(&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 */ /* NOINLINE: limit stack usage in caller */ static NOINLINE int send_decline(/*uint32_t xid,*/ uint32_t server, uint32_t requested) { struct dhcp_packet packet; /* Fill in: op, htype, hlen, cookie, chaddr, random xid fields, * client-id option (unless -C), message type option: */ init_packet(&packet, DHCPDECLINE); #if 0 /* RFC 2131 says DHCPDECLINE's xid is randomly selected by client, * but in case the server is buggy and wants DHCPDECLINE's xid * to match the xid which started entire handshake, * we use the same xid we used in initial DHCPDISCOVER: */ packet.xid = xid; #endif /* DHCPDECLINE uses "requested ip", not ciaddr, to store offered IP */ udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested); udhcp_add_simple_option(&packet, 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; /* Fill in: op, htype, hlen, cookie, chaddr, random xid fields, * client-id option (unless -C), message type option: */ init_packet(&packet, DHCPRELEASE); /* DHCPRELEASE uses ciaddr, not "requested ip", to store IP being released */ packet.ciaddr = ciaddr; udhcp_add_simple_option(&packet, 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 */ /* NOINLINE: limit stack usage in caller */ 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; 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 != inet_cksum((uint16_t *)&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 != inet_cksum((uint16_t *)&packet, bytes)) { log1("Packet with bad UDP checksum received, ignoring"); return -2; } if (packet.data.cookie != htonl(DHCP_MAGIC)) { bb_info_msg("Packet with bad magic, ignoring"); return -2; } log1("Received a packet"); udhcp_dump_packet(&packet.data); bytes -= sizeof(packet.ip) + sizeof(packet.udp); memcpy(dhcp_pkt, &packet.data, bytes); return bytes; } /*** Main ***/ 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; 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? */ static const struct sock_filter filter_instr[] = { /* load 9th byte (protocol) */ BPF_STMT(BPF_LD|BPF_B|BPF_ABS, 9), /* jump to L1 if it is IPPROTO_UDP, else to L4 */ BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, IPPROTO_UDP, 0, 6), /* L1: load halfword from offset 6 (flags and frag offset) */ BPF_STMT(BPF_LD|BPF_H|BPF_ABS, 6), /* jump to L4 if any bits in frag offset field are set, else to L2 */ BPF_JUMP(BPF_JMP|BPF_JSET|BPF_K, 0x1fff, 4, 0), /* L2: skip IP header (load index reg with header len) */ BPF_STMT(BPF_LDX|BPF_B|BPF_MSH, 0), /* load udp destination port from halfword[header_len + 2] */ BPF_STMT(BPF_LD|BPF_H|BPF_IND, 2), /* jump to L3 if udp dport is CLIENT_PORT, else to L4 */ BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, 68, 0, 1), /* L3: accept packet */ BPF_STMT(BPF_RET|BPF_K, 0xffffffff), /* L4: discard packet */ BPF_STMT(BPF_RET|BPF_K, 0), }; 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? sock.sll_family = AF_PACKET; sock.sll_protocol = htons(ETH_P_IP); sock.sll_ifindex = ifindex; xbind(fd, (struct sockaddr *) &sock, sizeof(sock)); if (CLIENT_PORT == 68) { /* Use only if standard port is 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? } log1("Created raw socket"); return fd; } 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 */ } /* Called only on SIGUSR1 */ 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; } } static void perform_release(uint32_t server_addr, uint32_t requested_ip) { 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; } 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; } #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 //usage:#if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1 //usage:# define IF_UDHCP_VERBOSE(...) __VA_ARGS__ //usage:#else //usage:# define IF_UDHCP_VERBOSE(...) //usage:#endif //usage:#define udhcpc_trivial_usage //usage: "[-fbnq"IF_UDHCP_VERBOSE("v")"oCRB] [-i IFACE] [-r IP] [-s PROG] [-p PIDFILE]\n" //usage: " [-V VENDOR] [-x OPT:VAL]... [-O OPT]..." IF_FEATURE_UDHCP_PORT(" [-P N]") //usage:#define udhcpc_full_usage "\n" //usage: IF_LONG_OPTS( //usage: "\n -i,--interface IFACE Interface to use (default eth0)" //usage: "\n -p,--pidfile FILE Create pidfile" //usage: "\n -s,--script PROG Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")" //usage: "\n -B,--broadcast Request broadcast replies" //usage: "\n -t,--retries N Send up to N discover packets" //usage: "\n -T,--timeout N Pause between packets (default 3 seconds)" //usage: "\n -A,--tryagain N Wait N seconds after failure (default 20)" //usage: "\n -f,--foreground Run in foreground" //usage: USE_FOR_MMU( //usage: "\n -b,--background Background if lease is not obtained" //usage: ) //usage: "\n -n,--now Exit if lease is not obtained" //usage: "\n -q,--quit Exit after obtaining lease" //usage: "\n -R,--release Release IP on exit" //usage: "\n -S,--syslog Log to syslog too" //usage: IF_FEATURE_UDHCP_PORT( //usage: "\n -P,--client-port N Use port N (default 68)" //usage: ) //usage: IF_FEATURE_UDHCPC_ARPING( //usage: "\n -a,--arping Use arping to validate offered address" //usage: ) //usage: "\n -O,--request-option OPT Request option OPT from server (cumulative)" //usage: "\n -o,--no-default-options Don't request any options (unless -O is given)" //usage: "\n -r,--request IP Request this IP address" //usage: "\n -x OPT:VAL Include option OPT in sent packets (cumulative)" //usage: "\n Examples of string, numeric, and hex byte opts:" //usage: "\n -x hostname:bbox - option 12" //usage: "\n -x lease:3600 - option 51 (lease time)" //usage: "\n -x 0x3d:0100BEEFC0FFEE - option 61 (client id)" //usage: "\n -F,--fqdn NAME Ask server to update DNS mapping for NAME" //usage: "\n -V,--vendorclass VENDOR Vendor identifier (default 'udhcp VERSION')" //usage: "\n -C,--clientid-none Don't send MAC as client identifier" //usage: IF_UDHCP_VERBOSE( //usage: "\n -v Verbose" //usage: ) //usage: ) //usage: IF_NOT_LONG_OPTS( //usage: "\n -i IFACE Interface to use (default eth0)" //usage: "\n -p FILE Create pidfile" //usage: "\n -s PROG Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")" //usage: "\n -B Request broadcast replies" //usage: "\n -t N Send up to N discover packets" //usage: "\n -T N Pause between packets (default 3 seconds)" //usage: "\n -A N Wait N seconds (default 20) after failure" //usage: "\n -f Run in foreground" //usage: USE_FOR_MMU( //usage: "\n -b Background if lease is not obtained" //usage: ) //usage: "\n -n Exit if lease is not obtained" //usage: "\n -q Exit after obtaining lease" //usage: "\n -R Release IP on exit" //usage: "\n -S Log to syslog too" //usage: IF_FEATURE_UDHCP_PORT( //usage: "\n -P N Use port N (default 68)" //usage: ) //usage: IF_FEATURE_UDHCPC_ARPING( //usage: "\n -a Use arping to validate offered address" //usage: ) //usage: "\n -O OPT Request option OPT from server (cumulative)" //usage: "\n -o Don't request any options (unless -O is given)" //usage: "\n -r IP Request this IP address" //usage: "\n -x OPT:VAL Include option OPT in sent packets (cumulative)" //usage: "\n Examples of string, numeric, and hex byte opts:" //usage: "\n -x hostname:bbox - option 12" //usage: "\n -x lease:3600 - option 51 (lease time)" //usage: "\n -x 0x3d:0100BEEFC0FFEE - option 61 (client id)" //usage: "\n -F NAME Ask server to update DNS mapping for NAME" //usage: "\n -V VENDOR Vendor identifier (default 'udhcp VERSION')" //usage: "\n -C Don't send MAC as client identifier" //usage: IF_UDHCP_VERBOSE( //usage: "\n -v Verbose" //usage: ) //usage: ) //usage: "\nSignals:" //usage: "\n USR1 Renew lease" //usage: "\n USR2 Release lease" 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_V, *str_h, *str_F, *str_r; IF_FEATURE_UDHCP_PORT(char *str_P;) void *clientid_mac_ptr; llist_t *list_O = NULL; llist_t *list_x = 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 = xid; /* for compiler */ int packet_num; int timeout; /* must be signed */ unsigned already_waited_sec; unsigned opt; int max_fd; int retval; fd_set rfds; /* Default options */ IF_FEATURE_UDHCP_PORT(SERVER_PORT = 67;) IF_FEATURE_UDHCP_PORT(CLIENT_PORT = 68;) client_config.interface = "eth0"; client_config.script = CONFIG_UDHCPC_DEFAULT_SCRIPT; str_V = "udhcp "BB_VER; /* Parse command line */ /* O,x: list; -T,-t,-A take numeric param */ opt_complementary = "O::x::T+:t+:A+" IF_UDHCP_VERBOSE(":vv") ; IF_LONG_OPTS(applet_long_options = udhcpc_longopts;) opt = getopt32(argv, "CV:H:h:F:i:np:qRr:s:T:t:SA:O:ox:fB" USE_FOR_MMU("b") IF_FEATURE_UDHCPC_ARPING("a") IF_FEATURE_UDHCP_PORT("P:") "v" , &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 , &list_x IF_FEATURE_UDHCP_PORT(, &str_P) IF_UDHCP_VERBOSE(, &dhcp_verbose) ); if (opt & (OPT_h|OPT_H)) { //msg added 2011-11 bb_error_msg("option -h NAME is deprecated, use -x hostname:NAME"); 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); unsigned n = bb_strtou(optstr, NULL, 0); if (errno || n > 254) { n = udhcp_option_idx(optstr); n = dhcp_optflags[n].code; } client_config.opt_mask[n >> 3] |= 1 << (n & 7); } while (list_x) { char *optstr = llist_pop(&list_x); char *colon = strchr(optstr, ':'); if (colon) *colon = ' '; /* now it looks similar to udhcpd's config file line: * "optname optval", using the common routine: */ udhcp_str2optset(optstr, &client_config.options); } if (udhcp_read_interface(client_config.interface, &client_config.ifindex, NULL, client_config.client_mac) ) { return 1; } clientid_mac_ptr = NULL; if (!(opt & OPT_C) && !udhcp_find_option(client_config.options, DHCP_CLIENT_ID)) { /* not suppressed and not set, set the default client ID */ client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, "", 7); client_config.clientid[OPT_DATA] = 1; /* type: ethernet */ clientid_mac_ptr = client_config.clientid + OPT_DATA+1; memcpy(clientid_mac_ptr, client_config.client_mac, 6); } if (str_V[0] != '\0') { // can drop -V, str_V, client_config.vendorclass, // but need to add "vendor" to the list of recognized // string opts for this to work; // and need to tweak add_client_options() too... // ...so the question is, should we? //bb_error_msg("option -V VENDOR is deprecated, use -x vendor:VENDOR"); 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 (;;) { struct timeval tv; struct dhcp_packet packet; /* 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) { /* When running on a bridge, the ifindex may have changed * (e.g. if member interfaces were added/removed * or if the status of the bridge changed). * Refresh ifindex and client_mac: */ if (udhcp_read_interface(client_config.interface, &client_config.ifindex, NULL, client_config.client_mac) ) { goto ret0; /* iface is gone? */ } if (clientid_mac_ptr) memcpy(clientid_mac_ptr, client_config.client_mac, 6); /* 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; client_config.first_secs = 0; /* make secs field count from 0 */ 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; client_config.first_secs = 0; /* make secs field count from 0 */ /*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: client_config.first_secs = 0; /* make secs field count from 0 */ already_waited_sec = 0; perform_renew(); if (state == RENEW_REQUESTED) { /* We might be either on the same network * (in which case renew might work), * or we might be on a completely different one * (in which case renew won't ever succeed). * For the second case, must make sure timeout * is not too big, or else we can send * futile renew requests for hours. * (Ab)use -A TIMEOUT value (usually 20 sec) * as a cap on the timeout. */ if (timeout > tryagain_timeout) timeout = tryagain_timeout; 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(server_addr, requested_ip); timeout = INT_MAX; continue; case SIGTERM: bb_info_msg("Received SIGTERM"); 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) != 0 ) { //FIXME: need to also check that last 10 bytes are zero log1("chaddr does not match, ignoring packet"); // log2? continue; } message = udhcp_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 */ if (*message == DHCPOFFER) { /* What exactly is server's IP? There are several values. * Example DHCP offer captured with tchdump: * * 10.34.25.254:67 > 10.34.25.202:68 // IP header's src * BOOTP fields: * Your-IP 10.34.25.202 * Server-IP 10.34.32.125 // "next server" IP * Gateway-IP 10.34.25.254 // relay's address (if DHCP relays are in use) * DHCP options: * DHCP-Message Option 53, length 1: Offer * Server-ID Option 54, length 4: 10.34.255.7 // "server ID" * Default-Gateway Option 3, length 4: 10.34.25.254 // router * * We think that real server IP (one to use in renew/release) * is one in Server-ID option. But I am not 100% sure. * IP header's src and Gateway-IP (same in this example) * might work too. * "Next server" and router are definitely wrong ones to use, though... */ temp = udhcp_get_option(&packet, DHCP_SERVER_ID); if (!temp) { bb_error_msg("no server ID, ignoring packet"); continue; /* still selecting - this server looks bad */ } /* it IS unaligned sometimes, don't "optimize" */ move_from_unaligned32(server_addr, temp); /*xid = packet.xid; - already is */ 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) { uint32_t lease_seconds; struct in_addr temp_addr; temp = udhcp_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); /* paranoia: must not be too small and not prone to overflows */ if (lease_seconds < 0x10) lease_seconds = 0x10; if (lease_seconds >= 0x10000000) lease_seconds = 0x0fffffff; } #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; client_config.first_secs = 0; /* make secs field count from 0 */ 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; 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 */ 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 /* make future renew packets use different xid */ /* xid = random_xid(); ...but why bother? */ 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; client_config.first_secs = 0; /* make secs field count from 0 */ 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: if (opt & OPT_R) /* release on quit */ perform_release(server_addr, requested_ip); retval = 0; ret: /*if (client_config.pidfile) - remove_pidfile has its own check */ remove_pidfile(client_config.pidfile); return retval; }