udhcpc: make it possible to disable vendor id; improve help text

function                                             old     new   delta
init_packet                                          135     139      +4
packed_usage                                       26789   26786      -3
alloc_dhcp_option                                     67      63      -4
udhcpc_main                                         2467    2447     -20
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/3 up/down: 4/-27)             Total: -23 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

6 files changed, 88 insertions, 82 deletions

diff --git a/examples/udhcp/udhcpd.conf b/examples/udhcp/udhcpd.conf
index 7fc37ab..0ad982b 100644
--- a/examples/udhcp/udhcpd.conf
+++ b/examples/udhcp/udhcpd.conf
@@ -20,18 +20,18 @@ interface	eth0
 #auto_time	7200
 
 # The amount of time that an IP will be reserved (leased to nobody)
-# if a DHCP decline message is received (seconds).
+# if a DHCP decline message is received (seconds)
 #decline_time	3600
 
 # The amount of time that an IP will be reserved
-# if an ARP conflict occurs (seconds).
+# if an ARP conflict occurs (seconds)
 #conflict_time	3600
 
-# How long an offered address is reserved (seconds).
+# How long an offered address is reserved (seconds)
 #offer_time	60
 
 # If client asks for lease below this value, it will be rounded up
-# to this value (seconds).
+# to this value (seconds)
 #min_lease	60
 
 # The location of the leases file
@@ -40,15 +40,19 @@ interface	eth0
 # The location of the pid file
 #pidfile	/var/run/udhcpd.pid
 
-# Every time udhcpd writes a leases file, the below script will be called.
+# Every time udhcpd writes a leases file, the below script will be called
 #notify_file			# default: no script
 #notify_file	dumpleases	# useful for debugging
 
-# The following are bootp specific options, settable by udhcpd.
+# The following are bootp specific options
 #siaddr		192.168.0.22		#default: 0.0.0.0
 #sname		zorak			#default: none
 #boot_file	/var/nfs_root		#default: none
 
+# Static leases map
+#static_lease 00:60:08:11:CE:4E 192.168.0.54
+#static_lease 00:60:08:11:CE:3E 192.168.0.44
+
 # The remainder of options are DHCP options and can be specified with the
 # keyword 'opt' or 'option'. If an option can take multiple items, such
 # as the dns option, they can be listed on the same line, or multiple
@@ -60,7 +64,7 @@ opt	router	192.168.10.2
 opt	wins	192.168.10.10
 option	dns	129.219.13.81	# appended to above DNS servers for a total of 3
 option	domain	local
-option	lease	864000		# 10 days of seconds
+option	lease	864000		# 10 days
 
 # Currently supported options (for more info, see options.c):
 #opt lease      NUM
@@ -92,7 +96,3 @@ option	lease	864000		# 10 days of seconds
 #opt swapsrv    IP
 #opt timesrv    IP_LIST
 #opt ntpsrv     IP_LIST
-
-# Static leases map
-#static_lease 00:60:08:11:CE:4E 192.168.0.54
-#static_lease 00:60:08:11:CE:3E 192.168.0.44
diff --git a/include/usage.h b/include/usage.h
index 093efc8..a7855cd 100644
--- a/include/usage.h
+++ b/include/usage.h
@@ -4810,66 +4810,68 @@
        "Adjust filesystem options on ext[23] filesystems"
 
 #define udhcpc_trivial_usage \
-       "[-Cfbnqtvo] [-c CID] [-V VCLS] [-H HOSTNAME] [-i INTERFACE]\n" \
-       "	[-p pidfile] [-r IP] [-s script] [-O dhcp-option]..." IF_FEATURE_UDHCP_PORT(" [-P N]")
-#define udhcpc_full_usage "\n\n" \
+       "[-fbnqvoCR] [-i IFACE] [-r IP] [-s PROG] [-p PIDFILE]\n" \
+       "	[-H HOSTNAME] [-c CID] [-V VENDOR] [-O DHCP_OPT]..." IF_FEATURE_UDHCP_PORT(" [-P N]")
+#define udhcpc_full_usage "\n" \
 	IF_LONG_OPTS( \
-       "	-V,--vendorclass=CLASSID	Vendor class identifier" \
-     "\n	-i,--interface=INTERFACE	Interface to use (default eth0)" \
-     "\n	-H,-h,--hostname=HOSTNAME	Client hostname" \
-     "\n	-c,--clientid=CLIENTID	Client identifier" \
-     "\n	-C,--clientid-none	Suppress default client identifier" \
-     "\n	-p,--pidfile=FILE	Create pidfile" \
-     "\n	-r,--request=IP		IP address to request" \
-     "\n	-s,--script=FILE	Run FILE at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")" \
-     "\n	-t,--retries=N		Send up to N discover packets" \
-     "\n	-T,--timeout=N		Pause between packets (default 3 seconds)" \
-     "\n	-A,--tryagain=N		Wait N seconds (default 20) after failure" \
-     "\n	-O,--request-option=OPT	Request DHCP option OPT (cumulative)" \
-     "\n	-o,--no-default-options	Don't request any options (unless -O is also given)" \
-     "\n	-f,--foreground	Run in foreground" \
+     "\n	-i,--interface IFACE	Interface to use (default eth0)" \
+     "\n	-p,--pidfile FILE	Create pidfile" \
+     "\n	-r,--request IP		IP address to request" \
+     "\n	-s,--script PROG	Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")" \
+     "\n	-t,--retries N		Send up to N discover packets" \
+     "\n	-T,--timeout N		Pause between packets (default 3 seconds)" \
+     "\n	-A,--tryagain N		Wait N seconds (default 20) after failure" \
+     "\n	-O,--request-option OPT	Request DHCP option OPT (cumulative)" \
+     "\n	-o,--no-default-options	Don't request any options (unless -O is given)" \
+     "\n	-f,--foreground		Run in foreground" \
 	USE_FOR_MMU( \
-     "\n	-b,--background	Background if lease is not immediately obtained" \
+     "\n	-b,--background		Background if lease is not obtained" \
 	) \
-     "\n	-S,--syslog	Log to syslog too" \
-     "\n	-n,--now	Exit with failure if lease is not immediately obtained" \
-     "\n	-q,--quit	Quit after obtaining lease" \
-     "\n	-R,--release	Release IP on quit" \
+     "\n	-S,--syslog		Log to syslog too" \
+     "\n	-n,--now		Exit if lease is not obtained" \
+     "\n	-q,--quit		Exit after obtaining lease" \
+     "\n	-R,--release		Release IP on exit" \
 	IF_FEATURE_UDHCP_PORT( \
-     "\n	-P,--client-port N  Use port N instead of default 68" \
+     "\n	-P,--client-port N	Use port N (default 68)" \
 	) \
 	IF_FEATURE_UDHCPC_ARPING( \
-     "\n	-a,--arping	Use arping to validate offered address" \
+     "\n	-a,--arping		Use arping to validate offered address" \
 	) \
+     "\n	-F,--fqdn NAME		Ask server to update DNS mapping for NAME" \
+     "\n	-H,-h,--hostname NAME	Send NAME as client hostname (default none)" \
+     "\n	-V,--vendorclass VENDOR	Vendor identifier (default 'udhcp VERSION')" \
+     "\n	-c,--clientid CLIENTID	Client identifier (default own MAC)" \
+     "\n	-C,--clientid-none	Don't send client identifier" \
 	) \
 	IF_NOT_LONG_OPTS( \
-       "	-V CLASSID	Vendor class identifier" \
-     "\n	-i INTERFACE	Interface to use (default: eth0)" \
-     "\n	-H,-h HOSTNAME	Client hostname" \
-     "\n	-c CLIENTID	Client identifier" \
-     "\n	-C		Suppress default client identifier" \
+     "\n	-i IFACE	Interface to use (default eth0)" \
      "\n	-p FILE		Create pidfile" \
      "\n	-r IP		IP address to request" \
-     "\n	-s FILE		Run FILE at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")" \
-     "\n	-t N		Send up to N request packets" \
-     "\n	-T N		Try to get a lease for N seconds (default 3)" \
+     "\n	-s PROG		Run PROG at DHCP events (default "CONFIG_UDHCPC_DEFAULT_SCRIPT")" \
+     "\n	-t N		Send up to N discover packets" \
+     "\n	-T N		Pause between packets (default 3 seconds)" \
      "\n	-A N		Wait N seconds (default 20) after failure" \
      "\n	-O OPT		Request DHCP option OPT (cumulative)" \
-     "\n	-o		Don't request any options (unless -O is also given)" \
+     "\n	-o		Don't request any options (unless -O is given)" \
      "\n	-f		Run in foreground" \
 	USE_FOR_MMU( \
-     "\n	-b		Background if lease is not immediately obtained" \
+     "\n	-b		Background if lease is not obtained" \
 	) \
      "\n	-S		Log to syslog too" \
-     "\n	-n		Exit with failure if lease is not immediately obtained" \
-     "\n	-q		Quit after obtaining lease" \
-     "\n	-R		Release IP on quit" \
+     "\n	-n		Exit if lease is not obtained" \
+     "\n	-q		Exit after obtaining lease" \
+     "\n	-R		Release IP on exit" \
 	IF_FEATURE_UDHCP_PORT( \
-     "\n	-P N		Use port N instead of default 68" \
+     "\n	-P N		Use port N (default 68)" \
 	) \
 	IF_FEATURE_UDHCPC_ARPING( \
      "\n	-a		Use arping to validate offered address" \
 	) \
+     "\n	-F NAME		Ask server to update DNS mapping for NAME" \
+     "\n	-H,-h NAME	Send NAME as client hostname (default none)" \
+     "\n	-V VENDOR	Vendor identifier (default 'udhcp VERSION')" \
+     "\n	-c CLIENTID	Client identifier (default own MAC)" \
+     "\n	-C		Don't send client identifier" \
 	)
 
 #define udhcpd_trivial_usage \
@@ -4880,7 +4882,7 @@
      "\n	-f	Run in foreground" \
      "\n	-S	Log to syslog too" \
 	IF_FEATURE_UDHCP_PORT( \
-     "\n	-P N	Use port N instead of default 67" \
+     "\n	-P N	Use port N (default 67)" \
 	)
 
 #define umount_trivial_usage \
diff --git a/networking/udhcp/clientpacket.c b/networking/udhcp/clientpacket.c
index f091d80..a255d6e 100644
--- a/networking/udhcp/clientpacket.c
+++ b/networking/udhcp/clientpacket.c
@@ -47,8 +47,12 @@ static void init_packet(struct dhcp_packet *packet, char type)
 		add_option_string(packet->options, client_config.hostname);
 	if (client_config.fqdn)
 		add_option_string(packet->options, client_config.fqdn);
-	if ((type != DHCPDECLINE) && (type != DHCPRELEASE))
+	if (type != DHCPDECLINE
+	 && type != DHCPRELEASE
+	 && client_config.vendorclass
+	) {
 		add_option_string(packet->options, client_config.vendorclass);
+	}
 }
 
 
diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
index 9a2fe35..3e2cd12 100644
--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -125,8 +125,7 @@ static void client_background(void)
 static uint8_t* alloc_dhcp_option(int code, const char *str, int extra)
 {
 	uint8_t *storage;
-	int len = strlen(str);
-	if (len > 255) len = 255;
+	int len = strnlen(str, 255);
 	storage = xzalloc(len + extra + OPT_DATA);
 	storage[OPT_CODE] = code;
 	storage[OPT_LEN] = len + extra;
@@ -139,7 +138,7 @@ int udhcpc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int udhcpc_main(int argc UNUSED_PARAM, char **argv)
 {
 	uint8_t *temp, *message;
-	char *str_c, *str_V, *str_h, *str_F, *str_r;
+	const char *str_c, *str_V, *str_h, *str_F, *str_r;
 	IF_FEATURE_UDHCP_PORT(char *str_P;)
 	llist_t *list_O = NULL;
 	int tryagain_timeout = 20;
@@ -222,6 +221,7 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
 	IF_FEATURE_UDHCP_PORT(CLIENT_PORT = 68;)
 	client_config.interface = "eth0";
 	client_config.script = DEFAULT_SCRIPT;
+	str_V = "udhcp "BB_VER;
 
 	/* Parse command line */
 	/* Cc: mutually exclusive; O: list; -T,-t,-A take numeric param */
@@ -246,23 +246,22 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
 		, &dhcp_verbose
 #endif
 		);
-	if (opt & OPT_c)
-		client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, str_c, 0);
-	if (opt & OPT_V)
-		client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, str_V, 0);
 	if (opt & (OPT_h|OPT_H))
 		client_config.hostname = alloc_dhcp_option(DHCP_HOST_NAME, str_h, 0);
 	if (opt & OPT_F) {
+		/* FQDN option format: [0x51][len][flags][0][0]<fqdn> */
 		client_config.fqdn = alloc_dhcp_option(DHCP_FQDN, str_F, 3);
-		/* Flags: 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 data is DNS format, i.e. <4>host<6>domain<3>com<0> not "host.domain.com"
-		N: 1 => Client requests Server to not update DNS
-		*/
+		/* 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; - redundant */
-		/* client_config.fqdn[OPT_DATA + 2] = 0; - redundant */
+		/*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);
@@ -291,6 +290,16 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
 		return 1;
 	}
 
+	if (opt & OPT_c) {
+		client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, str_c, 0);
+	} else if (!(opt & OPT_C)) {
+		/* not set and not suppressed, set the default client ID */
+		client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, "", 7);
+		client_config.clientid[OPT_DATA] = 1; /* type: ethernet */
+		memcpy(client_config.clientid + OPT_DATA+1, client_config.client_mac, 6);
+	}
+	if (str_V[0] != '\0')
+		client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, str_V, 0);
 #if !BB_MMU
 	/* on NOMMU reexec (i.e., background) early */
 	if (!(opt & OPT_f)) {
@@ -314,16 +323,6 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
 	/* Goes to stdout (unless NOMMU) and possibly syslog */
 	bb_info_msg("%s (v"BB_VER") started", applet_name);
 
-	/* If not set, and not suppressed, set up the default client ID */
-	if (!client_config.clientid && !(opt & OPT_C)) {
-		client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, "", 7);
-		client_config.clientid[OPT_DATA] = 1;
-		memcpy(client_config.clientid + OPT_DATA+1, client_config.client_mac, 6);
-	}
-
-	if (!client_config.vendorclass)
-		client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, "udhcp "BB_VER, 0);
-
 	/* Set up the signal pipe */
 	udhcp_sp_setup();
 
diff --git a/networking/udhcp/options.c b/networking/udhcp/options.c
index c2a2305..09d31c69 100644
--- a/networking/udhcp/options.c
+++ b/networking/udhcp/options.c
@@ -13,6 +13,7 @@
 
 /* Supported options are easily added here.
  * See RFC2132 for more options.
+ * OPTION_REQ: these options are requested by udhcpc (unless -o).
  */
 const struct dhcp_option dhcp_options[] = {
 	/* flags                                    code */
diff --git a/networking/udhcp/options.h b/networking/udhcp/options.h
index 2d9c15f..75087fa 100644
--- a/networking/udhcp/options.h
+++ b/networking/udhcp/options.h
@@ -46,9 +46,9 @@ enum {
 #define DHCP_LOG_SERVER         0x07
 //#define DHCP_COOKIE_SERVER    0x08 /* "quote of the day" server */
 #define DHCP_LPR_SERVER         0x09
-#define DHCP_HOST_NAME          0x0c
+#define DHCP_HOST_NAME          0x0c /* either client informs server or server gives name to client */
 #define DHCP_BOOT_SIZE          0x0d
-#define DHCP_DOMAIN_NAME        0x0f
+#define DHCP_DOMAIN_NAME        0x0f /* server gives domain suffix */
 #define DHCP_SWAP_SERVER        0x10
 #define DHCP_ROOT_PATH          0x11
 #define DHCP_IP_TTL             0x17
@@ -61,14 +61,14 @@ enum {
 #define DHCP_OPTION_OVERLOAD    0x34
 #define DHCP_MESSAGE_TYPE       0x35
 #define DHCP_SERVER_ID          0x36 /* by default server's IP */
-#define DHCP_PARAM_REQ          0x37
+#define DHCP_PARAM_REQ          0x37 /* list of options client wants */
 #define DHCP_MESSAGE            0x38 /* error message when sending NAK etc */
 #define DHCP_MAX_SIZE           0x39
 //#define DHCP_T1               0x3a
 //#define DHCP_T2               0x3b
-#define DHCP_VENDOR             0x3c /* client's vendor */
-#define DHCP_CLIENT_ID          0x3d /* by default client's MAC addr */
-#define DHCP_FQDN               0x51
+#define DHCP_VENDOR             0x3c /* client's vendor (a string) */
+#define DHCP_CLIENT_ID          0x3d /* by default client's MAC addr, but may be arbitrarily long */
+#define DHCP_FQDN               0x51 /* client asks to update DNS to map its FQDN to its new IP */
 #define DHCP_STATIC_ROUTES      0x79
 #define DHCP_END                0xFF
 /* Offsets in option byte sequence */