Track pending events in time by using absolute times rather than relative

timeouts.

ndhc/arp.c

@@ -67,7 +67,7 @@ typedef enum {
     AS_MAX,
 } arp_state_t;
 
-static int arp_timeout[AS_MAX] = { -1, -1, -1, -1, -1 };
+static long long arp_wake_ts[AS_MAX] = { -1, -1, -1, -1, -1 };
 
 typedef enum {
     ASEND_COLLISION_CHECK,
@@ -273,7 +273,7 @@ int arp_close_fd(struct client_state_t *cs)
 {
     arp_min_close_fd(cs);
     for (int i = 0; i < AS_MAX; ++i)
-        arp_timeout[i] = -1;
+        arp_wake_ts[i] = -1;
     return 1;
 }
 
@@ -372,7 +372,8 @@ int arp_check(struct client_state_t *cs, struct dhcpmsg *packet)
     cs->arpPrevState = cs->dhcpState;
     cs->dhcpState = DS_COLLISION_CHECK;
     arp_check_start_ts = arp_send_stats[ASEND_COLLISION_CHECK].ts;
-    arp_timeout[AS_COLLISION_CHECK] = probe_wait_time = PROBE_WAIT;
+    probe_wait_time = PROBE_WAIT;
+    arp_wake_ts[AS_COLLISION_CHECK] = arp_check_start_ts + probe_wait_time;
     return 0;
 }
 
@@ -387,7 +388,8 @@ int arp_gw_check(struct client_state_t *cs)
     arp_switch_state(cs, AS_GW_CHECK);
     cs->arpPrevState = cs->dhcpState;
     cs->dhcpState = DS_BOUND_GW_CHECK;
-    arp_timeout[AS_GW_CHECK] = ARP_RETRANS_DELAY + 250;
+    arp_wake_ts[AS_GW_CHECK] =
+        arp_send_stats[ASEND_GW_PING].ts + ARP_RETRANS_DELAY + 250;
     return 0;
 }
 
@@ -399,7 +401,8 @@ static int arp_get_gw_hwaddr(struct client_state_t *cs)
     log_line("arp: Searching for gw address...");
     if (arp_ping(cs, cs->routerAddr) == -1)
         return -1;
-    arp_timeout[AS_GW_QUERY] = ARP_RETRANS_DELAY + 250;
+    arp_wake_ts[AS_GW_QUERY] =
+        arp_send_stats[ASEND_GW_PING].ts + ARP_RETRANS_DELAY + 250;
     return 0;
 }
 
@@ -407,7 +410,7 @@ static void arp_failed(struct client_state_t *cs)
 {
     log_line("arp: Offered address is in use -- declining");
     send_decline(cs, arp_dhcp_packet.yiaddr);
-    arp_timeout[AS_COLLISION_CHECK] = -1;
+    arp_wake_ts[AS_COLLISION_CHECK] = -1;
     reinit_selecting(cs, total_conflicts < MAX_CONFLICTS ?
                      0 : RATE_LIMIT_INTERVAL);
 }
@@ -415,7 +418,7 @@ static void arp_failed(struct client_state_t *cs)
 static void arp_gw_failed(struct client_state_t *cs)
 {
     log_line("arp: Gateway appears to have changed, getting new lease.");
-    arp_timeout[AS_GW_CHECK] = -1;
+    arp_wake_ts[AS_GW_CHECK] = -1;
     reinit_selecting(cs, 0);
 }
 
@@ -435,8 +438,6 @@ void arp_set_defense_mode(struct client_state_t *cs)
 
 void arp_success(struct client_state_t *cs)
 {
-    cs->dhcp_timeout = (cs->renewTime * 1000) - (curms() - cs->leaseStartTime);
-
     struct in_addr temp_addr = {.s_addr = arp_dhcp_packet.yiaddr};
     log_line("arp: Lease of %s obtained, lease time %ld",
              inet_ntoa(temp_addr), cs->lease);
@@ -444,7 +445,7 @@ void arp_success(struct client_state_t *cs)
     cs->dhcpState = DS_BOUND;
     cs->init = 0;
     last_conflict_ts = 0;
-    arp_timeout[AS_COLLISION_CHECK] = -1;
+    arp_wake_ts[AS_COLLISION_CHECK] = -1;
     ifchange_bind(&arp_dhcp_packet);
     if (cs->arpPrevState == DS_RENEWING || cs->arpPrevState == DS_REBINDING) {
         arp_switch_state(cs, AS_DEFENSE);
@@ -472,7 +473,7 @@ static void arp_gw_success(struct client_state_t *cs)
     arp_switch_state(cs, AS_DEFENSE);
     arp_announcement(cs);
 
-    arp_timeout[AS_GW_CHECK] = -1;
+    arp_wake_ts[AS_GW_CHECK] = -1;
     cs->dhcpState = cs->arpPrevState;
 }
 
@@ -534,10 +535,10 @@ static int arp_gen_probe_wait(void)
 
 static void arp_defense_timeout(struct client_state_t *cs, long long nowts)
 {
-    if (arp_timeout[AS_DEFENSE] != -1) {
+    if (arp_wake_ts[AS_DEFENSE] != -1) {
         log_line("arp: Defending our lease IP.");
         arp_announcement(cs);
-        arp_timeout[AS_DEFENSE] = -1;
+        arp_wake_ts[AS_DEFENSE] = -1;
     }
 }
 
@@ -549,7 +550,7 @@ static void arp_check_timeout(struct client_state_t *cs, long long nowts)
         return;
     long long rtts = arp_send_stats[ASEND_GW_PING].ts + ARP_RETRANS_DELAY;
     if (nowts < rtts) {
-        arp_timeout[arpState] = rtts - nowts;
+        arp_wake_ts[arpState] = rtts;
         return;
     }
     log_line(arpState == AS_GW_CHECK ?
@@ -557,7 +558,8 @@ static void arp_check_timeout(struct client_state_t *cs, long long nowts)
              "arp: Still looking for gateway hardware address...");
     if (arp_ping(cs, cs->routerAddr) == -1)
         log_warning("arp: Failed to send ARP ping in retransmission.");
-    arp_timeout[arpState] = ARP_RETRANS_DELAY;
+    arp_wake_ts[arpState] =
+        arp_send_stats[ASEND_GW_PING].ts + ARP_RETRANS_DELAY;
 }
 
 static void arp_collision_timeout(struct client_state_t *cs, long long nowts)
@@ -572,19 +574,21 @@ static void arp_collision_timeout(struct client_state_t *cs, long long nowts)
     long long rtts = arp_send_stats[ASEND_COLLISION_CHECK].ts +
         probe_wait_time;
     if (nowts < rtts) {
-        arp_timeout[AS_COLLISION_CHECK] = rtts - nowts;
+        arp_wake_ts[AS_COLLISION_CHECK] = rtts;
         return;
     }
     if (arp_ip_anon_ping(cs, arp_dhcp_packet.yiaddr) == -1)
         log_warning("arp: Failed to send ARP ping in retransmission.");
-    arp_timeout[AS_COLLISION_CHECK] = probe_wait_time = arp_gen_probe_wait();
+    probe_wait_time = arp_gen_probe_wait();
+    arp_wake_ts[AS_COLLISION_CHECK] =
+        arp_send_stats[ASEND_COLLISION_CHECK].ts + probe_wait_time;
 }
 
 static void arp_do_defense(struct client_state_t *cs)
 {
     log_line("arp: detected a peer attempting to use our IP!");
     long long nowts = curms();
-    arp_timeout[AS_DEFENSE] = -1;
+    arp_wake_ts[AS_DEFENSE] = -1;
     if (!last_conflict_ts ||
         nowts - last_conflict_ts < DEFEND_INTERVAL) {
         log_line("arp: Defending our lease IP.");
@@ -594,8 +598,8 @@ static void arp_do_defense(struct client_state_t *cs)
         send_release(cs);
         reinit_selecting(cs, 0);
     } else {
-        arp_timeout[AS_DEFENSE] =
+        arp_wake_ts[AS_DEFENSE] =
-            arp_send_stats[ASEND_ANNOUNCE].ts + DEFEND_INTERVAL - nowts;
+            arp_send_stats[ASEND_ANNOUNCE].ts + DEFEND_INTERVAL;
     }
     total_conflicts++;
     last_conflict_ts = nowts;
@@ -605,7 +609,7 @@ static void arp_do_gw_query(struct client_state_t *cs)
 {
     if (arp_is_query_reply(&arpreply) &&
         !memcmp(arpreply.sip4, &cs->routerAddr, 4)) {
-        arp_timeout[AS_GW_QUERY] = -1;
+        arp_wake_ts[AS_GW_QUERY] = -1;
         memcpy(cs->routerArp, arpreply.smac, 6);
         log_line("arp: Gateway hardware address %02x:%02x:%02x:%02x:%02x:%02x",
                  cs->routerArp[0], cs->routerArp[1],
@@ -714,27 +718,15 @@ void handle_arp_timeout(struct client_state_t *cs, long long nowts)
         arp_states[arpState].timeout_fn(cs, nowts);
 }
 
-int get_arp_timeout(void)
+long long arp_get_wake_ts(void)
 {
-    int mt = INT_MAX;
+    long long mt = -1;
     for (int i = 0; i < AS_MAX; ++i) {
-        log_line("DEBUG: arp_timeout[%u] == %d", i, arp_timeout[i]);
+        if (arp_wake_ts[i] == -1)
-        if (arp_timeout[i] < mt && arp_timeout[i] >= 0)
+            continue;
-            mt = arp_timeout[i];
+        if (mt == -1 || mt > arp_wake_ts[i])
+            mt = arp_wake_ts[i];
     }
-    if (mt == INT_MAX)
-        return -1;
     return mt;
 }
 
-void arp_timeout_adj(int off)
-{
-    for (int i = 0; i < AS_MAX; ++i) {
-        if (arp_timeout[i] == -1)
-            continue;
-        arp_timeout[i] -= off;
-        if (arp_timeout[i] < 0)
-            arp_timeout[i] = 0;
-    }
-}
-

ndhc/arp.h

@@ -55,7 +55,6 @@ void arp_set_defense_mode(struct client_state_t *cs);
 void arp_success(struct client_state_t *cs);
 void handle_arp_response(struct client_state_t *cs);
 void handle_arp_timeout(struct client_state_t *cs, long long nowts);
-int get_arp_timeout(void);
+long long arp_get_wake_ts(void);
-void arp_timeout_adj(int off);
 
 #endif /* ARP_H_ */

ndhc/config.h

@@ -30,7 +30,6 @@ struct client_state_t {
     int ifsPrevState;
     int listenMode;
     int epollFd, signalFd, listenFd, arpFd, nlFd;
-    int dhcp_timeout;
     uint32_t clientAddr, serverAddr, routerAddr;
     uint32_t lease, renewTime, rebindTime, xid;
     int using_dhcp_bpf;

ndhc/ndhc.c

@@ -161,8 +161,8 @@ static int get_clientid_mac_string(char *str, size_t slen)
 static void do_work(void)
 {
     struct epoll_event events[3];
-    long long last_awake, nowts;
+    long long nowts;
-    int timeout, timeout_delta;
+    int timeout;
 
     cs.epollFd = epoll_create1(0);
     if (cs.epollFd == -1)
@@ -174,7 +174,6 @@ static void do_work(void)
     goto jumpstart;
 
     for (;;) {
-        log_line("DEBUG: before epoll_wait()");
         int r = epoll_wait(cs.epollFd, events, 3, timeout);
         if (r == -1) {
             if (errno == EINTR)
@@ -182,7 +181,6 @@ static void do_work(void)
             else
                 suicide("epoll_wait failed");
         }
-        log_line("DEBUG: after epoll_wait()");
         for (int i = 0; i < r; ++i) {
             int fd = events[i].data.fd;
             if (fd == cs.signalFd)
@@ -197,39 +195,31 @@ static void do_work(void)
                 suicide("epoll_wait: unknown fd");
         }
 
-        nowts = curms();
+        for (;;) {
-        timeout_delta = nowts - last_awake;
+            nowts = curms();
+            long long arp_wake_ts = arp_get_wake_ts();
+            long long dhcp_wake_ts = dhcp_get_wake_ts();
+            if (arp_wake_ts == -1) {
+                if (dhcp_wake_ts != -1) {
+                    timeout = dhcp_wake_ts - nowts;
+                    if (timeout < 0)
+                        timeout = 0;
+                } else
+                    timeout = -1;
+            } else {
+                // If dhcp_wake_ts is -1 then we want to sleep anyway.
+                timeout = (arp_wake_ts < dhcp_wake_ts ?
+                           arp_wake_ts : dhcp_wake_ts) - nowts;
+                if (timeout < 0)
+                    timeout = 0;
+            }
 
-        cs.dhcp_timeout -= timeout_delta;
+            if (!timeout) {
-        if (cs.dhcp_timeout < 0)
-            cs.dhcp_timeout = 0;
-        arp_timeout_adj(timeout_delta);
-
-        int arp_timeout = get_arp_timeout();
-        log_line("DEBUG: arp_timeout = %d, dhcp_timeout = %d",
-                 arp_timeout, cs.dhcp_timeout);
-        if (arp_timeout == -1)
-            timeout = cs.dhcp_timeout;
-        else if (arp_timeout < cs.dhcp_timeout)
-            timeout = arp_timeout;
-        else
-            timeout = cs.dhcp_timeout;
-        
-        if (timeout <= 0) {
 jumpstart:
-            timeout_action(&cs, nowts);
+                timeout_action(&cs, nowts);
-
+            } else
-            int arp_timeout = get_arp_timeout();
+                break;
-            log_line("DEBUG: arp_timeout = %d, dhcp_timeout = %d",
-                     arp_timeout, cs.dhcp_timeout);
-            if (arp_timeout == -1)
-                timeout = cs.dhcp_timeout;
-            else if (arp_timeout < cs.dhcp_timeout)
-                timeout = arp_timeout;
-            else
-                timeout = cs.dhcp_timeout;
         }
-        last_awake = nowts;
     }
 }
 

ndhc/state.c

@@ -12,6 +12,8 @@
 #include "sys.h"
 #include "random.h"
 
+static long long dhcp_wake_ts = -1;
+
 static void selecting_packet(struct client_state_t *cs, struct dhcpmsg *packet,
                              uint8_t *message);
 static void an_packet(struct client_state_t *cs, struct dhcpmsg *packet,
@@ -62,7 +64,7 @@ void reinit_selecting(struct client_state_t *cs, int timeout)
     ifchange_deconfig();
     arp_close_fd(cs);
     cs->dhcpState = DS_SELECTING;
-    cs->dhcp_timeout = timeout;
+    dhcp_wake_ts = curms() + timeout;
     cs->clientAddr = 0;
     num_dhcp_requests = 0;
     arp_reset_send_stats();
@@ -74,7 +76,7 @@ static void set_released(struct client_state_t *cs)
     ifchange_deconfig();
     arp_close_fd(cs);
     cs->dhcpState = DS_RELEASED;
-    cs->dhcp_timeout = -1;
+    dhcp_wake_ts = -1;
     cs->clientAddr = 0;
     num_dhcp_requests = 0;
     arp_reset_send_stats();
@@ -89,7 +91,7 @@ static void requesting_timeout(struct client_state_t *cs, long long nowts)
 {
     if (num_dhcp_requests < 5) {
         send_selecting(cs);
-        cs->dhcp_timeout = delay_timeout(num_dhcp_requests);
+        dhcp_wake_ts = nowts + delay_timeout(num_dhcp_requests);
         num_dhcp_requests++;
     } else
         reinit_selecting(cs, 0);
@@ -101,7 +103,7 @@ static void bound_timeout(struct client_state_t *cs, long long nowts)
 {
     long long rnt = cs->leaseStartTime + cs->renewTime * 1000;
     if (nowts < rnt) {
-        cs->dhcp_timeout = rnt - nowts;
+        dhcp_wake_ts = rnt;
         return;
     }
     cs->dhcpState = DS_RENEWING;
@@ -126,21 +128,17 @@ static void renewing_timeout(struct client_state_t *cs, long long nowts)
 {
     long long rbt = cs->leaseStartTime + cs->rebindTime * 1000;
     if (nowts < rbt) {
-        long long wt = (rbt - nowts) / 2;
+        if (rbt - nowts < 30000) {
-        if (wt >= 30000)
+            dhcp_wake_ts = rbt;
-            send_renew(cs);
+            return;
-        else
+        }
-            wt = rbt - nowts;
+        send_renew(cs);
-        cs->dhcp_timeout = wt;
+        dhcp_wake_ts = nowts + ((rbt - nowts) / 2);
-        return;
+    } else {
-    }
-    long long elt = cs->leaseStartTime + cs->lease * 1000;
-    if (nowts < elt) {
         cs->dhcpState = DS_REBINDING;
-        cs->dhcp_timeout = (elt - nowts) / 2;
         log_line("Entering rebinding state.");
-    } else
+        rebinding_timeout(cs, nowts);
-        lease_timedout(cs);
+    }
 }
 
 // Triggered when a DHCP rebind request has been sent and no reply has been
@@ -151,19 +149,19 @@ static void rebinding_timeout(struct client_state_t *cs, long long nowts)
 {
     long long elt = cs->leaseStartTime + cs->lease * 1000;
     if (nowts < elt) {
-        long long wt = (elt - nowts) / 2;
+        if (elt - nowts < 30000) {
-        if (wt >= 30000)
+            dhcp_wake_ts = elt;
-            send_rebind(cs);
+            return;
-        else
+        }
-            wt = elt - nowts;
+        send_rebind(cs);
-        cs->dhcp_timeout = wt;
+        dhcp_wake_ts = nowts + ((elt - nowts) / 2);
     } else
         lease_timedout(cs);
 }
 
 static void released_timeout(struct client_state_t *cs, long long nowts)
 {
-    cs->dhcp_timeout = -1;
+    dhcp_wake_ts = -1;
 }
 
 // Can transition to DS_BOUND or DS_SELECTING.
@@ -189,6 +187,7 @@ static void an_packet(struct client_state_t *cs, struct dhcpmsg *packet,
         // the remote server values, if they even exist, for sanity.
         cs->renewTime = cs->lease >> 1;
         cs->rebindTime = (cs->lease >> 3) * 0x7; // * 0.875
+        dhcp_wake_ts = cs->leaseStartTime + cs->renewTime * 1000;
 
         // Only check if we are either in the REQUESTING state, or if we
         // have received a lease with a different IP than what we had before.
@@ -200,7 +199,6 @@ static void an_packet(struct client_state_t *cs, struct dhcpmsg *packet,
             }
         } else {
             cs->dhcpState = DS_BOUND;
-            cs->dhcp_timeout = cs->renewTime * 1000;
             arp_set_defense_mode(cs);
             set_listen_none(cs);
         }
@@ -222,7 +220,7 @@ static void selecting_packet(struct client_state_t *cs, struct dhcpmsg *packet,
             cs->xid = packet->xid;
             cs->clientAddr = packet->yiaddr;
             cs->dhcpState = DS_REQUESTING;
-            cs->dhcp_timeout = 0;
+            dhcp_wake_ts = curms();
             num_dhcp_requests = 0;
         } else {
             log_line("No server ID in message");
@@ -249,7 +247,7 @@ static void selecting_timeout(struct client_state_t *cs, long long nowts)
     if (num_dhcp_requests == 0)
         cs->xid = libc_random_u32();
     send_discover(cs);
-    cs->dhcp_timeout = delay_timeout(num_dhcp_requests);
+    dhcp_wake_ts = nowts + delay_timeout(num_dhcp_requests);
     num_dhcp_requests++;
 }
 
@@ -335,3 +333,8 @@ void force_release_action(struct client_state_t *cs)
         dhcp_states[cs->dhcpState].force_release_fn(cs);
 }
 
+long long dhcp_get_wake_ts(void)
+{
+    return dhcp_wake_ts;
+}
+

ndhc/state.h

@@ -27,6 +27,7 @@ void force_release_action(struct client_state_t *cs);
 void ifup_action(struct client_state_t *cs);
 void ifnocarrier_action(struct client_state_t *cs);
 void ifdown_action(struct client_state_t *cs);
+long long dhcp_get_wake_ts(void);
 
 #endif