udhcpc[6]: fix "untangle timeout and remaining lease" fallout

As reported in bug 13776, before this fix the renew never times out.

function                                             old     new   delta
udhcpc_main                                         2541    2585     +44
udhcpc6_main                                        2567    2558      -9
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/1 up/down: 44/-9)              Total: 35 bytes

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

2 files changed, 47 insertions, 30 deletions

diff --git a/networking/udhcp/d6_dhcpc.c b/networking/udhcp/d6_dhcpc.c
index 0a5cae310..5bca4a824 100644
--- a/networking/udhcp/d6_dhcpc.c
+++ b/networking/udhcp/d6_dhcpc.c
@@ -1356,14 +1356,17 @@ int udhcpc6_main(int argc UNUSED_PARAM, char **argv)
                         log1("waiting %u seconds", timeout);
                         diff = (unsigned)monotonic_sec();
                         retval = poll(pfds, 2, timeout * 1000);
+                        diff = (unsigned)monotonic_sec() - diff;
+                        lease_remaining -= diff;
+                        if (lease_remaining < 0)
+                                lease_remaining = 0;
+                        timeout -= diff;
+                        if (timeout < 0)
+                                timeout = 0;
+
                         if (retval < 0) {
                                 /* EINTR? A signal was caught, don't panic */
                                 if (errno == EINTR) {
-                                        diff = (unsigned)monotonic_sec() - diff;
-                                        lease_remaining -= diff;
-                                        if (lease_remaining < 0)
-                                                lease_remaining = 0;
-                                        timeout -= diff;
                                         continue;
                                 }
                                 /* Else: an error occured, panic! */
@@ -1455,7 +1458,6 @@ int udhcpc6_main(int argc UNUSED_PARAM, char **argv)
                         case_RENEW_REQUESTED:
                         case RENEWING:
                                 if (packet_num < 3) {
-                                        packet_num++;
                                         /* send an unicast renew request */
                         /* Sometimes observed to fail (EADDRNOTAVAIL) to bind
                          * a new UDP socket for sending inside send_renew.
@@ -1471,23 +1473,26 @@ int udhcpc6_main(int argc UNUSED_PARAM, char **argv)
                                                 send_d6_renew(xid, &srv6_buf, requested_ipv6);
                                         timeout = discover_timeout;
                                         /* ^^^ used to be = lease_remaining / 2 - WAY too long */
+                                        packet_num++;
                                         continue;
                                 }
                                 /* Timed out, enter rebinding state */
                                 log1s("entering rebinding state");
                                 client_data.state = REBINDING;
+                                packet_num = 0;
                                 /* 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 (lease_remaining > 0) {
+                                if (lease_remaining > 0 && packet_num < 3) {
                                         if (opt & OPT_l)
                                                 send_d6_info_request(xid);
                                         else /* send a broadcast renew request */
                                                 send_d6_renew(xid, /*server_ipv6:*/ NULL, requested_ipv6);
                                         timeout = discover_timeout;
+                                        packet_num++;
                                         continue;
                                 }
                                 /* Timed out, enter init state */
@@ -1809,12 +1814,9 @@ int udhcpc6_main(int argc UNUSED_PARAM, char **argv)
                                 start = monotonic_sec();
                                 d6_run_script(packet.d6_options, packet_end,
                                         (client_data.state == REQUESTING ? "bound" : "renew"));
-                                timeout = (unsigned)lease_remaining / 2;
-                                timeout -= (unsigned)monotonic_sec() - start;
-                                packet_num = 0;
-
-                                client_data.state = BOUND;
-                                change_listen_mode(LISTEN_NONE);
+                                lease_remaining -= (unsigned)monotonic_sec() - start;
+                                if (lease_remaining < 0)
+                                        lease_remaining = 0;
                                 if (opt & OPT_q) { /* quit after lease */
                                         goto ret0;
                                 }
@@ -1827,6 +1829,12 @@ int udhcpc6_main(int argc UNUSED_PARAM, char **argv)
                                         opt = ((opt & ~OPT_b) | OPT_f);
                                 }
 #endif
+
+// BOUND_for_half_lease:
+                                timeout = (unsigned)lease_remaining / 2;
+                                client_data.state = BOUND;
+                                change_listen_mode(LISTEN_NONE);
+                                packet_num = 0;
                                 continue; /* back to main loop */
                         }
                         continue;
diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
index 6666cbce6..ea06405ba 100644
--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -1417,14 +1417,17 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
                         log1("waiting %u seconds", timeout);
                         diff = (unsigned)monotonic_sec();
                         retval = poll(pfds, 2, timeout * 1000);
+                        diff = (unsigned)monotonic_sec() - diff;
+                        lease_remaining -= diff;
+                        if (lease_remaining < 0)
+                                lease_remaining = 0;
+                        timeout -= diff;
+                        if (timeout < 0)
+                                timeout = 0;
+
                         if (retval < 0) {
                                 /* EINTR? A signal was caught, don't panic */
                                 if (errno == EINTR) {
-                                        diff = (unsigned)monotonic_sec() - diff;
-                                        lease_remaining -= diff;
-                                        if (lease_remaining < 0)
-                                                lease_remaining = 0;
-                                        timeout -= diff;
                                         continue;
                                 }
                                 /* Else: an error occurred, panic! */
@@ -1513,7 +1516,6 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
                         case_RENEW_REQUESTED:
                         case RENEWING:
                                 if (packet_num < 3) {
-                                        packet_num++;
                                         /* send an unicast renew request */
                         /* Sometimes observed to fail (EADDRNOTAVAIL) to bind
                          * a new UDP socket for sending inside send_renew.
@@ -1526,6 +1528,7 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
                                         if (send_renew(xid, server_addr, requested_ip) >= 0) {
                                                 timeout = discover_timeout;
                                                 /* ^^^ used to be = lease_remaining / 2 - WAY too long */
+                                                packet_num++;
                                                 continue;
                                         }
                                         /* else: error sending.
@@ -1534,21 +1537,26 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
                                          * which wasn't reachable (and probably did not exist).
                                          */
                                 }
-//TODO: if 3 renew's failed (no reply) but remaining lease is large,
-//it might make sense to make a large pause (~1 hour?) and try later?
+//TODO: if 3 renew's failed (no reply) but remaining lease is large enough,
+//it might make sense to go back to BOUND and try later? a-la
+// if (lease_remaining > 30) goto BOUND_for_half_lease;
+//If we do that, "packet_num < 3" test below might be superfluous
+//(lease_remaining will run out anyway)
                                 /* Timed out or error, enter rebinding state */
                                 log1s("entering rebinding state");
                                 client_data.state = REBINDING;
+                                packet_num = 0;
                                 /* 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 (lease_remaining > 0) {
+                                if (lease_remaining > 0 && packet_num < 3) {
                                         /* send a broadcast renew request */
                                         send_renew(xid, 0 /*INADDR_ANY*/, requested_ip);
                                         timeout = discover_timeout;
+                                        packet_num++;
                                         continue;
                                 }
                                 /* Timed out, enter init state */
@@ -1773,13 +1781,9 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
                                 /* enter bound state */
                                 start = monotonic_sec();
                                 udhcp_run_script(&packet, client_data.state == REQUESTING ? "bound" : "renew");
-                                timeout = (unsigned)lease_remaining / 2;
-//TODO: why / 2?
-                                timeout -= (unsigned)monotonic_sec() - start;
-                                packet_num = 0;
-
-                                client_data.state = BOUND;
-                                change_listen_mode(LISTEN_NONE);
+                                lease_remaining -= (unsigned)monotonic_sec() - start;
+                                if (lease_remaining < 0)
+                                        lease_remaining = 0;
                                 if (opt & OPT_q) { /* quit after lease */
                                         goto ret0;
                                 }
@@ -1792,9 +1796,14 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
                                         opt = ((opt & ~OPT_b) | OPT_f);
                                 }
 #endif
+
+// BOUND_for_half_lease:
+                                timeout = (unsigned)lease_remaining / 2;
+                                client_data.state = BOUND;
+                                change_listen_mode(LISTEN_NONE);
                                 /* make future renew packets use different xid */
                                 /* xid = random_xid(); ...but why bother? */
-
+                                packet_num = 0;
                                 continue; /* back to main loop */
                         }
                         if (*message == DHCPNAK) {