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busybox/networking/udhcp/dhcpc.c
Hans Dedecker abe8f7515a dhcpc: Use client IP address as source address for DHCP renew/rebind messages 
RFC2131 paragraph 4.1 states DHCP messages broadcast by a client prior to
that client obtaining its IP address must have the source IP address
field in the header set to 0.
Request messages transmitted in renewing and rebinding state need to use
the obtained IP address as source IP address in the header; this behavior
lines up with other implementations like ISC dhcp client.

Signed-off-by: Hans Dedecker <dedeckeh@gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2016-03-03 02:05:53 +01:00

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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>
#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_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" 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_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("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 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 (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++;
if (*name == '\0')
return 1; // We allow trailing dot too
}
}
#else
# define good_hostname(name) 1
#endif
/* 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) / (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, uint32_t src_nip)
{
return udhcp_send_raw_packet(packet,
/*src*/ src_nip, 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, 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),
* 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, 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 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, 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),
* 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, INADDR_ANY);
}
#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_1(fd, SOL_PACKET, PACKET_AUXDATA) != 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")"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: 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[MSEC],--arping[=MSEC] Validate offered address with ARP ping"
//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[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 -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_UDHCPC_ARPING(const char *str_a = "2000";)
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;
IF_FEATURE_UDHCPC_ARPING(unsigned arpping_ms;)
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_UDHCPC_ARPING(, &str_a)
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
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);
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) {
unsigned start;
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,
arpping_ms)
) {
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 */
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;
start = monotonic_sec();
udhcp_run_script(&packet, state == REQUESTING ? "bound" : "renew");
already_waited_sec = (unsigned)monotonic_sec() - start;
timeout = lease_seconds / 2;
if ((unsigned)timeout < already_waited_sec) {
/* Something went wrong. Back to discover state */
timeout = already_waited_sec = 0;
}
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? */
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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