/* 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. */ //applet:IF_UDHCPC(APPLET(udhcpc, BB_DIR_SBIN, BB_SUID_DROP)) //kbuild:lib-$(CONFIG_UDHCPC) += common.o packet.o signalpipe.o socket.o //kbuild:lib-$(CONFIG_UDHCPC) += dhcpc.o //kbuild:lib-$(CONFIG_FEATURE_UDHCPC_ARPING) += arpping.o //kbuild:lib-$(CONFIG_FEATURE_UDHCP_RFC3397) += domain_codec.o #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 #ifndef PACKET_AUXDATA # define PACKET_AUXDATA 8 struct tpacket_auxdata { uint32_t tp_status; uint32_t tp_len; uint32_t tp_snaplen; uint16_t tp_mac; uint16_t tp_net; uint16_t tp_vlan_tci; uint16_t tp_padding; }; #endif /* "struct client_data_t client_data" 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" //deprecated "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" USE_FOR_MMU( "background\0" No_argument "b" ) "broadcast\0" No_argument "B" IF_FEATURE_UDHCPC_ARPING("arping\0" Optional_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_F = 1 << 2, OPT_i = 1 << 3, OPT_n = 1 << 4, OPT_p = 1 << 5, OPT_q = 1 << 6, OPT_R = 1 << 7, OPT_r = 1 << 8, OPT_s = 1 << 9, OPT_T = 1 << 10, OPT_t = 1 << 11, OPT_S = 1 << 12, OPT_A = 1 << 13, OPT_O = 1 << 14, OPT_o = 1 << 15, OPT_x = 1 << 16, OPT_f = 1 << 17, OPT_B = 1 << 18, /* The rest has variable bit positions, need to be clever */ OPTBIT_B = 18, 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 ***/ struct dhcp_optitem { unsigned len; uint8_t code; uint8_t malloced; uint8_t *data; char *env; }; /* get a rough idea of how long an option will be (rounding up...) */ static const uint8_t len_of_option_as_string[] ALIGN1 = { [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("132 128 ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff 255.255.255.255 "), [OPTION_STRING ] = 1, [OPTION_STRING_HOST ] = 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; } #if ENABLE_FEATURE_UDHCPC_SANITIZEOPT /* Check if a given name represents a valid DNS name */ /* See RFC1035, 2.3.1 */ /* We don't need to be particularly anal. For example, allowing _, hyphen * at the end, or leading and trailing dots would be ok, since it * can't be used for attacks. (Leading hyphen can be, if someone uses cmd "$hostname" * in the script: then hostname may be treated as an option) */ static int good_hostname(const char *name) { if (*name == '-') /* Can't start with '-' */ return 0; while (*name) { unsigned char ch = *name++; if (!isalnum(ch)) /* DNS allows only '-', but we are more permissive */ if (ch != '-' && ch != '_' && ch != '.') return 0; // TODO: do we want to validate lengths against NS_MAXLABEL and NS_MAXDNAME? } return 1; } #else # define good_hostname(name) 1 #endif /* Create "opt_name=opt_value" string */ static NOINLINE char *xmalloc_optname_optval(const struct dhcp_optitem *opt_item, const struct dhcp_optflag *optflag, const char *opt_name) { unsigned upper_length; int len, type, optlen; char *dest, *ret; uint8_t *option; option = opt_item->data; len = opt_item->len; type = optflag->flags & OPTION_TYPE_MASK; optlen = dhcp_option_lengths[type]; upper_length = len_of_option_as_string[type] * ((unsigned)(len + optlen) / (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_PAIR) 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: case OPTION_STRING_HOST: memcpy(dest, option, len); dest[len] = '\0'; //TODO: it appears option 15 DHCP_DOMAIN_NAME is often abused //by DHCP admins to contain a space-separated list of domains, //not one domain name (presumably, to work as list of search domains, //instead of using proper option 119 DHCP_DOMAIN_SEARCH). //Currently, good_hostname() balks on strings containing spaces. //Do we need to allow it? Only for DHCP_DOMAIN_NAME option? if (type == OPTION_STRING_HOST && !good_hostname(dest)) safe_strncpy(dest, "bad", len); 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 needs 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; *dest++ = ' '; /* 6rdBRIPv4Address(es), use common IPv4 logic to process them */ type = OPTION_IP; optlen = 4; continue; } 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] == 1) { /* use common IPv4 logic to process IP addrs */ type = OPTION_IP; optlen = 4; continue; } if (option[-1] == 0) { dest = dname_dec(option, len, ret); if (dest) { free(ret); return dest; } } 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; } static void optitem_unset_env_and_free(void *item) { struct dhcp_optitem *opt_item = item; bb_unsetenv_and_free(opt_item->env); if (opt_item->malloced) free(opt_item->data); free(opt_item); } /* Used by static options (interface, siaddr, etc) */ static void putenvp(char *new_opt) { struct dhcp_optitem *opt_item; opt_item = xzalloc(sizeof(*opt_item)); /* opt_item->code = 0, so it won't appear in concat_option's lookup */ /* opt_item->malloced = 0 */ /* opt_item->data = NULL */ opt_item->env = new_opt; llist_add_to(&client_data.envp, opt_item); log2(" %s", new_opt); putenv(new_opt); } /* Support RFC3396 Long Encoded Options */ static struct dhcp_optitem *concat_option(uint8_t *data, uint8_t len, uint8_t code) { llist_t *item; struct dhcp_optitem *opt_item; /* Check if an option with the code already exists. * A possible optimization is to create a bitmap of all existing options in the packet, * and iterate over the option list only if they exist. * This will result in bigger code, and because dhcp packets don't have too many options it * shouldn't have a big impact on performance. */ for (item = client_data.envp; item != NULL; item = item->link) { opt_item = (struct dhcp_optitem *)item->data; if (opt_item->code == code) { /* This option was seen already, concatenate */ uint8_t *new_data; new_data = xmalloc(len + opt_item->len); memcpy( mempcpy(new_data, opt_item->data, opt_item->len), data, len ); opt_item->len += len; if (opt_item->malloced) free(opt_item->data); opt_item->malloced = 1; opt_item->data = new_data; return opt_item; } } /* This is a new option, add a new dhcp_optitem to the list */ opt_item = xzalloc(sizeof(*opt_item)); opt_item->code = code; /* opt_item->malloced = 0 */ opt_item->data = data; opt_item->len = len; llist_add_to(&client_data.envp, opt_item); return opt_item; } static const char* get_optname(uint8_t code, const struct dhcp_optflag **dh) { /* Find the option: * dhcp_optflags is sorted so we stop searching when dh->code >= code, which is faster * than iterating over the entire array. * Options which don't have a match in dhcp_option_strings[], e.g DHCP_REQUESTED_IP, * are located after the sorted array, so these entries will never be reached * and they'll count as unknown options. */ for (*dh = dhcp_optflags; (*dh)->code && (*dh)->code < code; (*dh)++) continue; if ((*dh)->code == code) return nth_string(dhcp_option_strings, (*dh - dhcp_optflags)); return NULL; } /* put all the parameters into the environment */ static void fill_envp(struct dhcp_packet *packet) { uint8_t *optptr; struct dhcp_scan_state scan_state; char *new_opt; putenvp(xasprintf("interface=%s", client_data.interface)); if (!packet) return; init_scan_state(packet, &scan_state); /* Iterate over the packet options. * Handle each option based on whether it's an unknown / known option. * Long options are supported in compliance with RFC 3396. */ while ((optptr = udhcp_scan_options(packet, &scan_state)) != NULL) { const struct dhcp_optflag *dh; const char *opt_name; struct dhcp_optitem *opt_item; uint8_t code = optptr[OPT_CODE]; uint8_t len = optptr[OPT_LEN]; uint8_t *data = optptr + OPT_DATA; opt_item = concat_option(data, len, code); opt_name = get_optname(code, &dh); if (opt_name) { new_opt = xmalloc_optname_optval(opt_item, dh, opt_name); if (opt_item->code == DHCP_SUBNET && opt_item->len == 4) { /* Generate extra envvar for DHCP_SUBNET, $mask */ uint32_t subnet; move_from_unaligned32(subnet, opt_item->data); putenvp(xasprintf("mask=%u", mton(subnet))); } } else { unsigned ofs; new_opt = xmalloc(sizeof("optNNN=") + 1 + opt_item->len*2); ofs = sprintf(new_opt, "opt%u=", opt_item->code); bin2hex(new_opt + ofs, (char *)opt_item->data, opt_item->len)[0] = '\0'; } log2(" %s", new_opt); putenv(new_opt); /* putenv will replace the existing environment variable in case of a duplicate. * Free the previous occurrence (NULL if it's the first one). */ free(opt_item->env); opt_item->env = new_opt; } /* 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 different IP?) * uint8_t chaddr[16]; // link-layer client hardware address (MAC) */ /* Most important one: yiaddr as $ip */ new_opt = xmalloc(sizeof("ip=255.255.255.255")); sprint_nip(new_opt, "ip=", (uint8_t *) &packet->yiaddr); putenvp(new_opt); if (packet->siaddr_nip) { /* IP address of next server to use in bootstrap */ new_opt = xmalloc(sizeof("siaddr=255.255.255.255")); sprint_nip(new_opt, "siaddr=", (uint8_t *) &packet->siaddr_nip); putenvp(new_opt); } if (packet->gateway_nip) { /* IP address of DHCP relay agent */ new_opt = xmalloc(sizeof("giaddr=255.255.255.255")); sprint_nip(new_opt, "giaddr=", (uint8_t *) &packet->gateway_nip); putenvp(new_opt); } if (!(scan_state.overload & FILE_FIELD) && packet->file[0]) { /* watch out for invalid packets */ new_opt = xasprintf("boot_file=%."DHCP_PKT_FILE_LEN_STR"s", packet->file); putenvp(new_opt); } if (!(scan_state.overload & SNAME_FIELD) && packet->sname[0]) { /* watch out for invalid packets */ new_opt = xasprintf("sname=%."DHCP_PKT_SNAME_LEN_STR"s", packet->sname); putenvp(new_opt); } } /* Call a script with a par file and env vars */ static void udhcp_run_script(struct dhcp_packet *packet, const char *name) { char *argv[3]; fill_envp(packet); /* call script */ log1("executing %s %s", client_data.script, name); argv[0] = (char*) client_data.script; argv[1] = (char*) name; argv[2] = NULL; spawn_and_wait(argv); /* Free all allocated environment variables */ llist_free(client_data.envp, optitem_unset_env_and_free); client_data.envp = NULL; } /*** 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) { unsigned secs; /* Fill in: op, htype, hlen, cookie fields; message type option: */ udhcp_init_header(packet, type); packet->xid = random_xid(); client_data.last_secs = monotonic_sec(); if (client_data.first_secs == 0) client_data.first_secs = client_data.last_secs; secs = client_data.last_secs - client_data.first_secs; packet->secs = (secs < 0xffff) ? htons(secs) : 0xffff; memcpy(packet->chaddr, client_data.client_mac, 6); } static void add_client_options(struct dhcp_packet *packet) { 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 = 1; i < DHCP_END; i++) { if (client_data.opt_mask[i >> 3] & (1 << (i & 7))) { packet->options[end + OPT_DATA + len] = i; 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; } /* 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_data.options; while (curr) { udhcp_add_binary_option(packet, curr->data); curr = curr->next; } // if (client_data.sname) // strncpy((char*)packet->sname, client_data.sname, sizeof(packet->sname) - 1); // if (client_data.boot_file) // strncpy((char*)packet->file, client_data.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_data_ifindex(struct dhcp_packet *packet, uint32_t src_nip) { return udhcp_send_raw_packet(packet, /*src*/ src_nip, CLIENT_PORT, /*dst*/ INADDR_BROADCAST, SERVER_PORT, MAC_BCAST_ADDR, client_data.ifindex); } static int bcast_or_ucast(struct dhcp_packet *packet, uint32_t ciaddr, uint32_t server) { if (server) return udhcp_send_kernel_packet(packet, ciaddr, CLIENT_PORT, server, SERVER_PORT, client_data.interface); return raw_bcast_from_client_data_ifindex(packet, ciaddr); } /* 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), * message type option: */ init_packet(&packet, DHCPDISCOVER); packet.xid = xid; if (requested) udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested); /* Add options: maxsize, * "param req" option according to -O, options specified with -x */ add_client_options(&packet); bb_simple_info_msg("broadcasting discover"); return raw_bcast_from_client_data_ifindex(&packet, INADDR_ANY); } /* 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 temp_addr; char server_str[sizeof("255.255.255.255")]; /* * 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), * 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, * "param req" option according to -O, and options specified with -x */ add_client_options(&packet); temp_addr.s_addr = server; strcpy(server_str, inet_ntoa(temp_addr)); temp_addr.s_addr = requested; bb_info_msg("broadcasting select for %s, server %s", inet_ntoa(temp_addr), server_str ); return raw_bcast_from_client_data_ifindex(&packet, INADDR_ANY); } /* 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), * message type option: */ init_packet(&packet, DHCPREQUEST); packet.xid = xid; packet.ciaddr = ciaddr; /* Add options: maxsize, * "param req" option according to -O, and options specified with -x */ add_client_options(&packet); if (server) { struct in_addr temp_addr; temp_addr.s_addr = server; bb_info_msg("sending renew to server %s", inet_ntoa(temp_addr)); } else { bb_simple_info_msg("broadcasting renew"); } return bcast_or_ucast(&packet, ciaddr, server); } #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, * 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); //TODO: add client-id opt? bb_simple_info_msg("broadcasting decline"); return raw_bcast_from_client_data_ifindex(&packet, INADDR_ANY); } #endif /* Unicast a DHCP release message */ static ALWAYS_INLINE /* one caller, help compiler to use this fact */ int send_release(uint32_t server, uint32_t ciaddr) { struct dhcp_packet packet; struct option_set *ci; /* Fill in: op, htype, hlen, cookie, chaddr, random xid fields, * 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); /* RFC 2131 section 3.1.6: * If the client used a 'client identifier' when it obtained the lease, * it MUST use the same 'client identifier' in the DHCPRELEASE message. */ ci = udhcp_find_option(client_data.options, DHCP_CLIENT_ID); if (ci) udhcp_add_binary_option(&packet, ci->data); bb_info_msg("sending %s", "release"); /* Note: normally we unicast here since "server" is not zero. * However, there _are_ people who run "address-less" DHCP servers, * and reportedly ISC dhcp client and Windows allow that. */ return bcast_or_ucast(&packet, ciaddr, server); } /* 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; unsigned char cmsgbuf[CMSG_LEN(sizeof(struct tpacket_auxdata))]; struct iovec iov; struct msghdr msg; struct cmsghdr *cmsg; /* used to use just safe_read(fd, &packet, sizeof(packet)) * but we need to check for TP_STATUS_CSUMNOTREADY :( */ iov.iov_base = &packet; iov.iov_len = sizeof(packet); memset(&msg, 0, sizeof(msg)); msg.msg_iov = &iov; msg.msg_iovlen = 1; msg.msg_control = cmsgbuf; msg.msg_controllen = sizeof(cmsgbuf); for (;;) { bytes = recvmsg(fd, &msg, 0); if (bytes < 0) { if (errno == EINTR) continue; log1s("packet read error, ignoring"); /* NB: possible down interface, etc. Caller should pause. */ return bytes; /* returns -1 */ } break; } if (bytes < (int) (sizeof(packet.ip) + sizeof(packet.udp))) { log1s("packet is too short, ignoring"); return -2; } if (bytes < ntohs(packet.ip.tot_len)) { /* packet is bigger than sizeof(packet), we did partial read */ log1s("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)) ) { log1s("unrelated/bogus packet, ignoring"); return -2; } /* verify IP checksum */ check = packet.ip.check; packet.ip.check = 0; if (check != inet_cksum(&packet.ip, sizeof(packet.ip))) { log1s("bad IP header checksum, ignoring"); return -2; } for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) { if (cmsg->cmsg_level == SOL_PACKET && cmsg->cmsg_type == PACKET_AUXDATA ) { /* some VMs don't checksum UDP and TCP data * they send to the same physical machine, * here we detect this case: */ struct tpacket_auxdata *aux = (void *)CMSG_DATA(cmsg); if (aux->tp_status & TP_STATUS_CSUMNOTREADY) goto skip_udp_sum_check; } } /* 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(&packet, bytes)) { log1s("packet with bad UDP checksum received, ignoring"); return -2; } skip_udp_sum_check: if (packet.data.cookie != htonl(DHCP_MAGIC)) { log1s("packet with bad magic, ignoring"); return -2; } log2("received %s", "a packet"); /* log2 because more informative msg for valid packets is printed later at log1 level */ udhcp_dump_packet(&packet.data); bytes -= sizeof(packet.ip) + sizeof(packet.udp); memcpy(dhcp_pkt, &packet.data, bytes); return bytes; } /*** Main ***/ /* Values for client_data.listen_mode */ #define LISTEN_NONE 0 #define LISTEN_KERNEL 1 #define LISTEN_RAW 2 /* Values for client_data.state */ /* 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 int udhcp_raw_socket(int ifindex) { int fd; struct sockaddr_ll sock; log2("opening raw socket on ifindex %d", ifindex); fd = xsocket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP)); /* ^^^^^ * SOCK_DGRAM: remove link-layer headers on input (SOCK_RAW keeps them) * ETH_P_IP: want to receive only packets with IPv4 eth type */ memset(&sock, 0, sizeof(sock)); /* let's be deterministic */ sock.sll_family = AF_PACKET; sock.sll_protocol = htons(ETH_P_IP); sock.sll_ifindex = ifindex; /*sock.sll_hatype = ARPHRD_???;*/ /*sock.sll_pkttype = PACKET_???;*/ /*sock.sll_halen = ???;*/ /*sock.sll_addr[8] = ???;*/ xbind(fd, (struct sockaddr *) &sock, sizeof(sock)); #if 0 /* Several users reported breakage when BPF filter is used */ if (CLIENT_PORT == 68) { /* Use only if standard port is in use */ /* * 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. */ 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 ("accept 0x7fffffff bytes") */ /* Accepting 0xffffffff works too but kernel 2.6.19 is buggy */ BPF_STMT(BPF_RET|BPF_K, 0x7fffffff), /* L4: discard packet ("accept zero bytes") */ 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, }; /* 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"); // log? } #endif if (setsockopt_1(fd, SOL_PACKET, PACKET_AUXDATA) != 0) { if (errno != ENOPROTOOPT) log1s("can't set PACKET_AUXDATA on 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" ); client_data.listen_mode = new_mode; if (client_data.sockfd >= 0) { close(client_data.sockfd); client_data.sockfd = -1; } if (new_mode == LISTEN_KERNEL) client_data.sockfd = udhcp_listen_socket(/*INADDR_ANY,*/ CLIENT_PORT, client_data.interface); else if (new_mode != LISTEN_NONE) client_data.sockfd = udhcp_raw_socket(client_data.ifindex); /* else LISTEN_NONE: client_data.sockfd stays closed */ } static void perform_release(uint32_t server_addr, uint32_t requested_ip) { char buffer[sizeof("255.255.255.255")]; struct in_addr temp_addr; change_listen_mode(LISTEN_NONE); /* send release packet */ if (client_data.state == BOUND || client_data.state == RENEWING || client_data.state == REBINDING || client_data.state == RENEW_REQUESTED ) { 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 */ } bb_simple_info_msg("entering released state"); /* * We can be here on: SIGUSR2, * or on exit (SIGTERM) and -R "release on quit" is specified. * Users requested to be notified in all cases, even if not in one * of the states above. */ udhcp_run_script(NULL, "deconfig"); client_data.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_data.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: "[-fbq"IF_UDHCP_VERBOSE("v")"RB]"IF_FEATURE_UDHCPC_ARPING(" [-a[MSEC]]")" [-t N] [-T SEC] [-A SEC/-n]\n" //usage: " [-i IFACE]"IF_FEATURE_UDHCP_PORT(" [-P PORT]")" [-s PROG] [-p PIDFILE]\n" //usage: " [-oC] [-r IP] [-V VENDOR] [-F NAME] [-x OPT:VAL]... [-O OPT]..." //usage:#define udhcpc_full_usage "\n" //usage: "\n -i IFACE Interface to use (default "CONFIG_UDHCPC_DEFAULT_INTERFACE")" //usage: IF_FEATURE_UDHCP_PORT( //usage: "\n -P PORT Use PORT (default 68)" //usage: ) //usage: "\n -s PROG Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")" //usage: "\n -p FILE Create pidfile" //usage: "\n -B Request broadcast replies" //usage: "\n -t N Send up to N discover packets (default 3)" //usage: "\n -T SEC Pause between packets (default 3)" //usage: "\n -A SEC Wait if lease is not obtained (default 20)" //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 -f Run in foreground" //usage: "\n -S Log to syslog too" //usage: IF_FEATURE_UDHCPC_ARPING( //usage: "\n -a[MSEC] Validate offered address with ARP ping" //usage: ) //usage: "\n -r IP Request this IP address" //usage: "\n -o Don't request any options (unless -O is given)" //usage: "\n -O OPT Request option OPT from server (cumulative)" //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 -x 14:'\"dumpfile\"' - option 14 (shell-quoted)" //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: "\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 *message; const char *str_V, *str_F, *str_r; IF_FEATURE_UDHCPC_ARPING(const char *str_a = "2000";) IF_FEATURE_UDHCP_PORT(char *str_P;) uint8_t *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 */ int lease_remaining; /* must be signed */ unsigned opt; IF_FEATURE_UDHCPC_ARPING(unsigned arpping_ms;) int retval; setup_common_bufsiz(); /* Default options */ IF_FEATURE_UDHCP_PORT(SERVER_PORT = 67;) IF_FEATURE_UDHCP_PORT(CLIENT_PORT = 68;) client_data.interface = CONFIG_UDHCPC_DEFAULT_INTERFACE; client_data.script = CONFIG_UDHCPC_DEFAULT_SCRIPT; client_data.sockfd = -1; str_V = "udhcp "BB_VER; /* Make sure fd 0,1,2 are open */ /* Set up the signal pipe on fds 3,4 - must be before openlog() */ udhcp_sp_setup(); /* Parse command line */ opt = getopt32long(argv, "^" /* O,x: list; -T,-t,-A take numeric param */ "CV: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" "\0" IF_UDHCP_VERBOSE("vv") /* -v is a counter */ , udhcpc_longopts , &str_V, &str_F , &client_data.interface, &client_data.pidfile /* i,p */ , &str_r /* r */ , &client_data.script /* s */ , &discover_timeout, &discover_retries, &tryagain_timeout /* T,t,A */ , &list_O , &list_x IF_FEATURE_UDHCPC_ARPING(, &str_a) IF_FEATURE_UDHCP_PORT(, &str_P) IF_UDHCP_VERBOSE(, &dhcp_verbose) ); if (opt & OPT_F) { char *p; unsigned len; /* FQDN option format: [0x51][len][flags][0][0] */ len = strlen(str_F); p = udhcp_insert_new_option( &client_data.options, DHCP_FQDN, len + 3, /*dhcp6:*/ 0); /* 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. */ p[OPT_DATA + 0] = 0x1; /*p[OPT_DATA + 1] = 0; - xzalloc did it */ /*p[OPT_DATA + 2] = 0; */ memcpy(p + OPT_DATA + 3, str_F, len); /* do not store NUL byte */ } 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_FEATURE_UDHCPC_ARPING(arpping_ms = xatou(str_a);) 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, dhcp_option_strings); n = dhcp_optflags[n].code; } client_data.opt_mask[n >> 3] |= 1 << (n & 7); } if (!(opt & OPT_o)) { unsigned i, n; for (i = 0; (n = dhcp_optflags[i].code) != 0; i++) { if (dhcp_optflags[i].flags & OPTION_REQ) { client_data.opt_mask[n >> 3] |= 1 << (n & 7); } } } while (list_x) { char *optstr = xstrdup(llist_pop(&list_x)); udhcp_str2optset(optstr, &client_data.options, dhcp_optflags, dhcp_option_strings, /*dhcpv6:*/ 0 ); free(optstr); } if (str_V[0] != '\0') { char *p; unsigned len; //msg added 2021-06 bb_error_msg("option -V VENDOR is deprecated, use -x vendor:VENDOR"); len = strlen(str_V); p = udhcp_insert_new_option( &client_data.options, DHCP_VENDOR, len, /*dhcp6:*/ 0); memcpy(p + OPT_DATA, str_V, len); /* do not store NUL byte */ } clientid_mac_ptr = NULL; if (!(opt & OPT_C) && !udhcp_find_option(client_data.options, DHCP_CLIENT_ID)) { /* not suppressed and not set, create default client ID */ clientid_mac_ptr = udhcp_insert_new_option( &client_data.options, DHCP_CLIENT_ID, 1 + 6, /*dhcp6:*/ 0); clientid_mac_ptr[OPT_DATA] = 1; /* type: ethernet */ clientid_mac_ptr += OPT_DATA + 1; /* skip option code, len, ethernet */ } /* Not really necessary (we redo it on every iteration) * but allows early (before daemonization) detection * of bad interface name. */ if (udhcp_read_interface(client_data.interface, &client_data.ifindex, NULL, client_data.client_mac) ) { return 1; } #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; } /* Create pidfile */ write_pidfile(client_data.pidfile); /* Goes to stdout (unless NOMMU) and possibly syslog */ bb_simple_info_msg("started, v"BB_VER); /* We want random_xid to be random... */ srand(monotonic_us()); client_data.state = INIT_SELECTING; udhcp_run_script(NULL, "deconfig"); packet_num = 0; timeout = 0; lease_remaining = 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 pollfd pfds[2]; struct dhcp_packet packet; //bb_error_msg("sockfd:%d, listen_mode:%d", client_data.sockfd, client_data.listen_mode); /* Was opening raw or udp socket here * if (client_data.listen_mode != LISTEN_NONE && client_data.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:"). */ udhcp_sp_fd_set(pfds, client_data.sockfd); retval = 0; /* If we already timed out, fall through with retval = 0, else... */ if (timeout > 0) { unsigned diff; if (timeout > INT_MAX/1000) timeout = INT_MAX/1000; log1("waiting %u seconds", timeout); diff = (unsigned)monotonic_sec(); retval = poll(pfds, 2, timeout * 1000); diff = (unsigned)monotonic_sec() - diff; lease_remaining -= diff; if (lease_remaining < 0) lease_remaining = 0; timeout -= diff; if (timeout < 0) timeout = 0; if (retval < 0) { /* EINTR? A signal was caught, don't panic */ if (errno == EINTR) { continue; } /* Else: an error occurred, panic! */ bb_simple_perror_msg_and_die("poll"); } } /* 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_data.interface, &client_data.ifindex, NULL, client_data.client_mac) ) { goto ret0; /* iface is gone? */ } if (clientid_mac_ptr) memcpy(clientid_mac_ptr, client_data.client_mac, 6); switch (client_data.state) { case INIT_SELECTING: if (!discover_retries || packet_num < discover_retries) { if (packet_num == 0) { change_listen_mode(LISTEN_RAW); xid = random_xid(); } /* broadcast */ send_discover(xid, requested_ip); timeout = discover_timeout; packet_num++; continue; } leasefail: change_listen_mode(LISTEN_NONE); udhcp_run_script(NULL, "leasefail"); #if BB_MMU /* -b is not supported on NOMMU */ if (opt & OPT_b) { /* background if no lease */ bb_simple_info_msg("no lease, forking to background"); client_background(); /* do not background again! */ opt = ((opt & ~(OPT_b|OPT_n)) | OPT_f); /* ^^^ also disables -n (-b takes priority over -n): * ifup's default udhcpc options are -R -n, * and users want to be able to add -b * (in a config file) to make it background * _and not exit_. */ } else #endif if (opt & OPT_n) { /* abort if no lease */ bb_simple_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 < 3) { /* 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 */ client_data.state = INIT_SELECTING; goto leasefail; case BOUND: /* 1/2 lease passed, enter renewing state */ client_data.state = RENEWING; client_data.first_secs = 0; /* make secs field count from 0 */ change_listen_mode(LISTEN_KERNEL); log1s("entering renew state"); /* fall right through */ case RENEW_REQUESTED: /* manual (SIGUSR1) renew */ case_RENEW_REQUESTED: case RENEWING: if (packet_num < 3) { /* 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. */ if (send_renew(xid, server_addr, requested_ip) >= 0) { timeout = discover_timeout; /* ^^^ used to be = lease_remaining / 2 - WAY too long */ packet_num++; continue; } /* else: error sending. * example: ENETUNREACH seen with server * which gave us bogus server ID 1.1.1.1 * which wasn't reachable (and probably did not exist). */ } //TODO: if 3 renew's failed (no reply) but remaining lease is large enough, //it might make sense to go back to BOUND and try later? a-la // if (lease_remaining > 30) change_listen_mode(LISTEN_NONE) + goto BOUND_for_half_lease; //If we do that, "packet_num < 3" test below might be superfluous //(lease_remaining will run out anyway) /* Timed out or error, enter rebinding state */ log1s("entering rebinding state"); client_data.state = REBINDING; /* Switch to bcast receive */ change_listen_mode(LISTEN_RAW); packet_num = 0; /* fall right through */ case REBINDING: /* Lease is *really* about to run out, * try to find DHCP server using broadcast */ if (lease_remaining > 0 && packet_num < 3) { /* send a broadcast renew request */ send_renew(xid, 0 /*INADDR_ANY*/, requested_ip); timeout = discover_timeout; packet_num++; continue; } /* Timed out, enter init state */ change_listen_mode(LISTEN_NONE); bb_simple_info_msg("lease lost, entering init state"); udhcp_run_script(NULL, "deconfig"); client_data.state = INIT_SELECTING; client_data.first_secs = 0; /* make secs field count from 0 */ timeout = 0; packet_num = 0; continue; /* case RELEASED: */ } /* RELEASED state (when we got SIGUSR2) ends up here. * (wait for SIGUSR1 to re-init, or for TERM, etc) */ timeout = INT_MAX; continue; /* back to main loop */ } /* if poll timed out */ /* poll() didn't timeout, something happened */ /* Is it a signal? */ switch (udhcp_sp_read()) { case SIGUSR1: client_data.first_secs = 0; /* make secs field count from 0 */ bb_simple_info_msg("performing DHCP renew"); switch (client_data.state) { /* Try to renew/rebind */ case BOUND: case RENEWING: case REBINDING: change_listen_mode(LISTEN_KERNEL); client_data.state = RENEW_REQUESTED; goto case_RENEW_REQUESTED; /* Start things over */ case RENEW_REQUESTED: /* two or more SIGUSR1 received */ change_listen_mode(LISTEN_NONE); udhcp_run_script(NULL, "deconfig"); default: /* case REQUESTING: */ /* case RELEASED: */ /* case INIT_SELECTING: */ change_listen_mode(LISTEN_NONE); } client_data.state = INIT_SELECTING; packet_num = 0; /* Kill any timeouts, user wants this to hurry along */ timeout = 0; continue; case SIGUSR2: perform_release(server_addr, requested_ip); /* ^^^ switches to LISTEN_NONE */ timeout = INT_MAX; continue; case SIGTERM: bb_info_msg("received %s", "SIGTERM"); goto ret0; } /* Is it a packet? */ if (!pfds[1].revents) continue; /* no */ { int len; /* A packet is ready, read it */ if (client_data.listen_mode == LISTEN_KERNEL) len = udhcp_recv_kernel_packet(&packet, client_data.sockfd); else len = udhcp_recv_raw_packet(&packet, client_data.sockfd); if (len == -1) { /* Error is severe, reopen socket */ bb_error_msg("read error: "STRERROR_FMT", reopening socket" STRERROR_ERRNO); sleep(discover_timeout); /* 3 seconds by default */ change_listen_mode(client_data.listen_mode); /* just close and reopen */ } if (len < 0) continue; } if (packet.xid != xid) { log1("xid %x (our is %x)%s", (unsigned)packet.xid, (unsigned)xid, ", ignoring packet" ); continue; } /* Ignore packets that aren't for us */ if (packet.hlen != 6 || memcmp(packet.chaddr, client_data.client_mac, 6) != 0 ) { //FIXME: need to also check that last 10 bytes are zero log1("chaddr does not match%s", ", ignoring packet"); continue; } message = udhcp_get_option(&packet, DHCP_MESSAGE_TYPE); if (message == NULL) { log1("no message type option%s", ", ignoring packet"); continue; } switch (client_data.state) { case INIT_SELECTING: /* Must be a DHCPOFFER */ if (*message == DHCPOFFER) { struct in_addr temp_addr; uint8_t *temp; /* 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... */ /* We used to ignore packets without DHCP_SERVER_ID. * I've got user reports from people who run "address-less" servers. * They either supply DHCP_SERVER_ID of 0.0.0.0 or don't supply it at all. * They say ISC DHCP client supports this case. */ server_addr = 0; temp = udhcp_get_option32(&packet, DHCP_SERVER_ID); if (!temp) { bb_simple_info_msg("no server ID, using 0.0.0.0"); } else { /* it IS unaligned sometimes, don't "optimize" */ move_from_unaligned32(server_addr, temp); } /*xid = packet.xid; - already is */ temp_addr.s_addr = requested_ip = packet.yiaddr; log1("received offer of %s", inet_ntoa(temp_addr)); /* enter requesting state */ client_data.state = REQUESTING; timeout = 0; packet_num = 0; } continue; case REQUESTING: case RENEWING: case RENEW_REQUESTED: case REBINDING: if (*message == DHCPACK) { unsigned start; struct in_addr temp_addr; char server_str[sizeof("255.255.255.255")]; uint8_t *temp; change_listen_mode(LISTEN_NONE); temp_addr.s_addr = server_addr; strcpy(server_str, inet_ntoa(temp_addr)); temp_addr.s_addr = packet.yiaddr; temp = udhcp_get_option32(&packet, DHCP_LEASE_TIME); if (!temp) { lease_remaining = 60 * 60; } else { uint32_t lease; /* it IS unaligned sometimes, don't "optimize" */ move_from_unaligned32(lease, temp); lease_remaining = ntohl(lease); } /* Log message _before_ we sanitize lease */ bb_info_msg("lease of %s obtained from %s, lease time %u%s", inet_ntoa(temp_addr), server_str, (unsigned)lease_remaining, temp ? "" : " (default)" ); /* paranoia: must not be too small and not prone to overflows */ /* NB: 60s leases _are_ used in real world * (temporary IPs while ISP modem initializes) * do not break this case by bumping it up. */ if (lease_remaining < 0) /* signed overflow? */ lease_remaining = INT_MAX; if (lease_remaining < 30) lease_remaining = 30; requested_ip = packet.yiaddr; #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(requested_ip, NULL, (uint32_t) 0, client_data.client_mac, client_data.interface, arpping_ms) ) { bb_simple_info_msg("offered address is in use " "(got ARP reply), declining"); send_decline(/*xid,*/ server_addr, packet.yiaddr); if (client_data.state != REQUESTING) udhcp_run_script(NULL, "deconfig"); client_data.state = INIT_SELECTING; client_data.first_secs = 0; /* make secs field count from 0 */ requested_ip = 0; timeout = tryagain_timeout; packet_num = 0; continue; /* back to main loop */ } } #endif /* enter bound state */ start = monotonic_sec(); udhcp_run_script(&packet, client_data.state == REQUESTING ? "bound" : "renew"); lease_remaining -= (unsigned)monotonic_sec() - start; if (lease_remaining < 0) lease_remaining = 0; 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 // BOUND_for_half_lease: timeout = (unsigned)lease_remaining / 2; client_data.state = BOUND; /* make future renew packets use different xid */ /* xid = random_xid(); ...but why bother? */ packet_num = 0; continue; /* back to main loop */ } if (*message == DHCPNAK) { /* If network has more than one DHCP server, * "wrong" server can reply first, with a NAK. * Do not interpret it as a NAK from "our" server. */ if (server_addr != 0) { uint32_t svid; uint8_t *temp; temp = udhcp_get_option32(&packet, DHCP_SERVER_ID); if (!temp) { non_matching_svid: log1("received DHCP NAK with wrong" " server ID%s", ", ignoring packet"); continue; } move_from_unaligned32(svid, temp); if (svid != server_addr) goto non_matching_svid; } /* return to init state */ change_listen_mode(LISTEN_NONE); bb_info_msg("received %s", "DHCP NAK"); udhcp_run_script(&packet, "nak"); if (client_data.state != REQUESTING) udhcp_run_script(NULL, "deconfig"); sleep(3); /* avoid excessive network traffic */ client_data.state = INIT_SELECTING; client_data.first_secs = 0; /* make secs field count from 0 */ requested_ip = 0; timeout = 0; packet_num = 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_data.pidfile) - remove_pidfile has its own check */ remove_pidfile(client_data.pidfile); return retval; }