udhcpc: simplify renewal of the lease

1 files changed, 19 insertions, 22 deletions

diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
index eeef435de..7138389b8 100644
--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -143,10 +143,7 @@ int udhcpc_main(int argc ATTRIBUTE_UNUSED, char **argv)
         uint32_t xid = 0;
         uint32_t lease_seconds = 0; /* can be given as 32-bit quantity */
         int packet_num;
-        /* t1, t2... what a wonderful names... */
-        unsigned t1 = t1; /* for gcc */
-        unsigned t2 = t2;
-        unsigned timestamp_got_lease = timestamp_got_lease;
+        unsigned already_waited_sec;
         unsigned opt;
         int max_fd;
         int retval;
@@ -337,6 +334,7 @@ int udhcpc_main(int argc ATTRIBUTE_UNUSED, char **argv)
         udhcp_run_script(NULL, "deconfig");
         change_listen_mode(LISTEN_RAW);
         packet_num = 0;
+        already_waited_sec = 0;
 
         /* Main event loop. select() waits on signal pipe and possibly
          * on sockfd.
@@ -353,7 +351,7 @@ int udhcpc_main(int argc ATTRIBUTE_UNUSED, char **argv)
                 }
                 max_fd = udhcp_sp_fd_set(&rfds, sockfd);
 
-                tv.tv_sec = timeout;
+                tv.tv_sec = timeout - already_waited_sec;
                 tv.tv_usec = 0;
                 retval = 0; /* If we already timed out, fall through, else... */
                 if (tv.tv_sec > 0) {
@@ -373,6 +371,9 @@ int udhcpc_main(int argc ATTRIBUTE_UNUSED, char **argv)
                  * resend discover/renew/whatever
                  */
                 if (retval == 0) {
+                        /* We will restart wait afresh in any case */
+                        already_waited_sec = 0;
+
                         switch (state) {
                         case INIT_SELECTING:
                                 if (packet_num < discover_retries) {
@@ -420,33 +421,29 @@ int udhcpc_main(int argc ATTRIBUTE_UNUSED, char **argv)
                                 packet_num = 0;
                                 continue;
                         case BOUND:
-                                /* Lease is starting to run out, time to enter renewing state */
+                                /* Half of the lease passed, time to enter renewing state */
                                 change_listen_mode(LISTEN_KERNEL);
                                 DEBUG("Entering renew state");
                                 state = RENEWING;
                                 /* fall right through */
                         case RENEWING:
-                                /* Either set a new T1, or enter REBINDING state */
-                                if ((t2 - t1) > (lease_seconds / (4*60*60) + 1)) {
+                                if (timeout > 60) {
                                         /* send a request packet */
                                         send_renew(xid, server_addr, requested_ip); /* unicast */
-                                        t1 += (t2 - t1) / 2;
-                                        timeout = t1 - ((unsigned)monotonic_sec() - timestamp_got_lease);
+                                        timeout >>= 1;
                                         continue;
                                 }
                                 /* Timed out, enter rebinding state */
                                 DEBUG("Entering rebinding state");
                                 state = REBINDING;
-                                timeout = (t2 - t1);
                                 continue;
                         case REBINDING:
                                 /* Lease is *really* about to run out,
                                  * try to find DHCP server using broadcast */
-                                if ((lease_seconds - t2) > (lease_seconds / (4*60*60) + 1)) {
+                                if (timeout > 0) {
                                         /* send a request packet */
                                         send_renew(xid, 0, requested_ip); /* broadcast */
-                                        t2 += (lease_seconds - t2) / 2;
-                                        timeout = t2 - ((unsigned)monotonic_sec() - timestamp_got_lease);
+                                        timeout >>= 1;
                                         continue;
                                 }
                                 /* Timed out, enter init state */
@@ -454,7 +451,7 @@ int udhcpc_main(int argc ATTRIBUTE_UNUSED, char **argv)
                                 udhcp_run_script(NULL, "deconfig");
                                 change_listen_mode(LISTEN_RAW);
                                 state = INIT_SELECTING;
-                                timeout = 0;
+                                /*timeout = 0; - already is */
                                 packet_num = 0;
                                 continue;
                         /* case RELEASED: */
@@ -477,7 +474,7 @@ int udhcpc_main(int argc ATTRIBUTE_UNUSED, char **argv)
                         /* 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. */
-                        timeout -= (unsigned)monotonic_sec() - timestamp_before_wait;
+                        already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
 
                         if (len == -1) { /* error is severe, reopen socket */
                                 DEBUG("error on read, %s, reopening socket", strerror(errno));
@@ -523,6 +520,7 @@ int udhcpc_main(int argc ATTRIBUTE_UNUSED, char **argv)
                                         state = REQUESTING;
                                         timeout = 0;
                                         packet_num = 0;
+                                        already_waited_sec = 0;
                                 }
                                 continue;
                         case RENEW_REQUESTED:
@@ -538,6 +536,7 @@ int udhcpc_main(int argc ATTRIBUTE_UNUSED, char **argv)
                                                 /* can be misaligned, thus memcpy */
                                                 memcpy(&lease_seconds, temp, 4);
                                                 lease_seconds = ntohl(lease_seconds);
+                                                lease_seconds &= 0x0fffffff; /* paranoia: must not be negative */
                                         }
 #if ENABLE_FEATURE_UDHCPC_ARPING
                                         if (opt & OPT_a) {
@@ -557,20 +556,16 @@ int udhcpc_main(int argc ATTRIBUTE_UNUSED, char **argv)
                                                         requested_ip = 0;
                                                         timeout = tryagain_timeout;
                                                         packet_num = 0;
+                                                        already_waited_sec = 0;
                                                         continue; /* back to main loop */
                                                 }
                                         }
 #endif
                                         /* enter bound state */
-                                        t1 = lease_seconds / 2;
-
-                                        /* little fixed point for n * .875 */
-                                        t2 = (lease_seconds * 7) >> 3;
+                                        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);
-                                        timestamp_got_lease = monotonic_sec();
-                                        timeout = t1;
                                         requested_ip = packet.yiaddr;
                                         udhcp_run_script(&packet,
                                                    ((state == RENEWING || state == REBINDING) ? "renew" : "bound"));
@@ -585,6 +580,7 @@ int udhcpc_main(int argc ATTRIBUTE_UNUSED, char **argv)
                                         if (!client_config.foreground)
                                                 client_background();
 
+                                        already_waited_sec = 0;
                                         continue; /* back to main loop */
                                 }
                                 if (*message == DHCPNAK) {
@@ -599,6 +595,7 @@ int udhcpc_main(int argc ATTRIBUTE_UNUSED, char **argv)
                                         requested_ip = 0;
                                         timeout = 0;
                                         packet_num = 0;
+                                        already_waited_sec = 0;
                                 }
                                 continue;
                         /* case BOUND, RELEASED: - ignore all packets */