udhcpc: emit "correct" secs field

In theory, sending secs set to constant zero should be ok too.
But some bleeping servers can actually be configured to answer ONLY
if secs is bigger than a preset value (!!)
http://developer.apple.com/library/mac/#documentation/Darwin/Reference/ManPages/man8/bootpd.8.html
grep for "reply_threshold_seconds"

function                                             old     new   delta
udhcpc_main                                         2573    2623     +50

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

2 files changed, 17 insertions, 0 deletions

diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
index e9a8412..ca82d37 100644
--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -407,11 +407,19 @@ static ALWAYS_INLINE uint32_t random_xid(void)
 /* 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);
@@ -848,6 +856,7 @@ static void change_listen_mode(int new_mode)
 	/* else LISTEN_NONE: sockfd stays closed */
 }
 
+/* Called only on SIGUSR1 */
 static void perform_renew(void)
 {
 	bb_info_msg("Performing a DHCP renew");
@@ -1260,6 +1269,7 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
 			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 */
@@ -1299,6 +1309,7 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
 				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;
@@ -1315,6 +1326,7 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
 		/* 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 */
 			perform_renew();
 			if (state == RENEW_REQUESTED)
 				goto case_RENEW_REQUESTED;
@@ -1446,6 +1458,7 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
 							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;
@@ -1493,6 +1506,7 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
 				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;
diff --git a/networking/udhcp/dhcpc.h b/networking/udhcp/dhcpc.h
index 9ef053a..2b35991 100644
--- a/networking/udhcp/dhcpc.h
+++ b/networking/udhcp/dhcpc.h
@@ -21,6 +21,9 @@ struct client_config_t {
 	uint8_t *vendorclass;           /* Optional vendor class-id to use */
 	uint8_t *hostname;              /* Optional hostname to use */
 	uint8_t *fqdn;                  /* Optional fully qualified domain name to use */
+
+	uint16_t first_secs;
+	uint16_t last_secs;
 } FIX_ALIASING;
 
 /* server_config sits in 1st half of bb_common_bufsiz1 */