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busybox/networking/udhcp/dhcpc.c
Denys Vlasenko e2318bbad7 udhcpc: ignore NAKs from "wrong" servers. Closes 4267 
function                                             old     new   delta
udhcpc_main                                         2716    2814     +98

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2014-02-27 18:15:50 +01:00

1822 lines
56 KiB
C
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/* vi: set sw=4 ts=4: */
/*
* udhcp client
*
* Russ Dill <Russ.Dill@asu.edu> July 2001
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <syslog.h>
/* 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 <netinet/if_ether.h>
#include <linux/filter.h>
#include <linux/if_packet.h>
/* "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,
[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;
}
/* Check if a given label represents a valid DNS label
* Return pointer to the first character after the label upon success,
* NULL otherwise.
* 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 const char *valid_domain_label(const char *label)
{
unsigned char ch;
unsigned pos = 0;
for (;;) {
ch = *label;
if ((ch|0x20) < 'a' || (ch|0x20) > 'z') {
if (pos == 0) {
/* label must begin with letter */
return NULL;
}
if (ch < '0' || ch > '9') {
if (ch == '\0' || ch == '.')
return label;
/* DNS allows only '-', but we are more permissive */
if (ch != '-' && ch != '_')
return NULL;
}
}
label++;
pos++;
//Do we want this?
//if (pos > 63) /* NS_MAXLABEL; labels must be 63 chars or less */
// return NULL;
}
}
/* Check if a given name represents a valid DNS name */
/* See RFC1035, 2.3.1 */
static int good_hostname(const char *name)
{
//const char *start = name;
for (;;) {
name = valid_domain_label(name);
if (!name)
return 0;
if (!name[0])
return 1;
//Do we want this?
//return ((name - start) < 1025); /* NS_MAXDNAME */
name++;
}
}
/* 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:
case OPTION_STRING_HOST:
memcpy(dest, option, len);
dest[len] = '\0';
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 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 */
//TODO: change logic to scan packet _once_
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)
{
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_config.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;
}
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);
}
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);
return raw_bcast_from_client_config_ifindex(packet);
}
/* 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...");
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,
* 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...");
/* 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;
log1("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))) {
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;
}
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((uint16_t *)&packet, bytes)) {
log1("Packet with bad UDP checksum received, ignoring");
return -2;
}
skip_udp_sum_check:
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;
log1("Opening raw socket on ifindex %d", ifindex); //log2?
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
*/
log1("Got raw socket 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 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 <sux@loplof.de>.
* 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(fd, SOL_PACKET, PACKET_AUXDATA,
&const_int_1, sizeof(int)) < 0
) {
if (errno != ENOPROTOOPT)
log1("Can't set PACKET_AUXDATA on raw socket");
}
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: "[-fbq"IF_UDHCP_VERBOSE("v")IF_FEATURE_UDHCPC_ARPING("a")"RB] [-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: IF_LONG_OPTS(
//usage: "\n -i,--interface IFACE Interface to use (default eth0)"
//usage: IF_FEATURE_UDHCP_PORT(
//usage: "\n -P,--client-port PORT Use PORT (default 68)"
//usage: )
//usage: "\n -s,--script PROG Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")"
//usage: "\n -p,--pidfile FILE Create pidfile"
//usage: "\n -B,--broadcast Request broadcast replies"
//usage: "\n -t,--retries N Send up to N discover packets (default 3)"
//usage: "\n -T,--timeout SEC Pause between packets (default 3)"
//usage: "\n -A,--tryagain SEC Wait if lease is not obtained (default 20)"
//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 -f,--foreground Run in foreground"
//usage: USE_FOR_MMU(
//usage: "\n -b,--background Background if lease is not obtained"
//usage: )
//usage: "\n -S,--syslog Log to syslog too"
//usage: IF_FEATURE_UDHCPC_ARPING(
//usage: "\n -a,--arping Use arping to validate offered address"
//usage: )
//usage: "\n -r,--request IP Request this IP address"
//usage: "\n -o,--no-default-options Don't request any options (unless -O is given)"
//usage: "\n -O,--request-option 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 -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: 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: "\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: USE_FOR_MMU(
//usage: "\n -b Background if lease is not obtained"
//usage: )
//usage: "\n -S Log to syslog too"
//usage: IF_FEATURE_UDHCPC_ARPING(
//usage: "\n -a Use arping to validate offered address"
//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 -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 *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]<fqdn> */
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
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);
}
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_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) {
log1("Waiting on select %u seconds", (int)tv.tv_sec);
timestamp_before_wait = (unsigned)monotonic_sec();
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 (!discover_retries || 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 (!discover_retries || 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) {
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 pcakets 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_option(&packet, DHCP_SERVER_ID);
if (!temp) {
bb_error_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 */
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;
uint8_t *temp;
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) {
/* 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_option(&packet, DHCP_SERVER_ID);
if (!temp) {
non_matching_svid:
log1("%s with wrong server ID, ignoring packet",
"Received DHCP NAK"
);
continue;
}
move_from_unaligned32(svid, temp);
if (svid != server_addr)
goto non_matching_svid;
}
/* 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;
}
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