udhcpd: add option for tweaking arpping

Some clients have a very short timeout for sending the DHCP
DISCOVER, shorter than the arpping timeout of 2000 milliseconds
that udhcpd uses by default.

This patch allows tweaking the timeout, or disabling of arpping
altogether, at the risk of handing out addresses which are
already in use.

function                                             old     new   delta
udhcpd_main                                         1460    1501     +41
udhcpc_main                                         2814    2851     +37
packed_usage                                       29957   29974     +17
arpping                                              477     493     +16
find_free_or_expired_nip                             161     174     +13
send_offer                                           285     292      +7
nobody_responds_to_arp                                85      89      +4
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 7/0 up/down: 135/0)             Total: 135 bytes

Signed-off-by: Michel Stam <m.stam@fugro.nl>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 11 insertions, 6 deletions

diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
index e468b7b..35e7c20 100644
--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -54,7 +54,7 @@ static const char udhcpc_longopts[] ALIGN1 =
 	"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_UDHCPC_ARPING("arping\0"	Optional_argument "a")
 	IF_FEATURE_UDHCP_PORT("client-port\0"	Required_argument "P")
 	;
 #endif
@@ -1150,7 +1150,7 @@ static void client_background(void)
 //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:       "[-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"
@@ -1174,7 +1174,7 @@ static void client_background(void)
 //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:     "\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)"
@@ -1211,7 +1211,7 @@ static void client_background(void)
 //usage:	)
 //usage:     "\n	-S		Log to syslog too"
 //usage:	IF_FEATURE_UDHCPC_ARPING(
-//usage:     "\n	-a		Use arping to validate offered address"
+//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)"
@@ -1238,6 +1238,7 @@ 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;
@@ -1252,6 +1253,7 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
 	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;
@@ -1269,7 +1271,7 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
 	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_UDHCPC_ARPING("a::")
 		IF_FEATURE_UDHCP_PORT("P:")
 		"v"
 		, &str_V, &str_h, &str_h, &str_F
@@ -1278,6 +1280,7 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
 		, &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)
 	);
@@ -1309,6 +1312,7 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
 		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);
@@ -1726,7 +1730,8 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
 							NULL,
 							(uint32_t) 0,
 							client_config.client_mac,
-							client_config.interface)
+							client_config.interface,
+							arpping_ms)
 					) {
 						bb_info_msg("Offered address is in use "
 							"(got ARP reply), declining");