Handle carrier interruptions in arp_collision_timeout() better.

Still not ideal; we need to note and retry these errors, but these
changes are preparatory and do not introduce regressions.

src/arp.c

@@ -484,6 +484,33 @@ int arp_gw_query_timeout(struct client_state_t cs[static 1], long long nowts)
     return ARPR_OK;
 }
 
+// Failure here is difficult to handle gracefully, as we do have a valid
+// IP but have not yet announced it to other hosts on our ethernet
+// segment.  We try to do so for one minute.  We must measure the time
+// directly so that carrier loss or suspend are handled properly.
+__attribute__((noreturn))
+static void quit_after_lease_handler(struct client_state_t cs[static 1])
+{
+    struct timespec res;
+    if (clock_gettime(CLOCK_MONOTONIC, &res) < 0) {
+        suicide("%s: (%) clock_gettime failed: %s",
+                client_config.interface, __func__, strerror(errno));
+    }
+    time_t init_ts = res.tv_sec;
+    for (;;) {
+        if (arp_announcement(cs) >= 0)
+            exit(EXIT_SUCCESS);
+        log_warning("%s: (%s) Failed to send ARP announcement: %s",
+                    client_config.interface, __func__, strerror(errno));
+        if (clock_gettime(CLOCK_MONOTONIC, &res) < 0) {
+            suicide("%s: (%) clock_gettime failed: %s",
+                    client_config.interface, __func__, strerror(errno));
+        }
+        if (res.tv_sec - init_ts > 60) break;
+    }
+    exit(EXIT_FAILURE);
+}
+
 int arp_collision_timeout(struct client_state_t cs[static 1], long long nowts)
 {
     if (nowts >= garp.arp_check_start_ts + ANNOUNCE_WAIT ||
@@ -503,22 +530,10 @@ int arp_collision_timeout(struct client_state_t cs[static 1], long long nowts)
                     client_config.interface);
         }
         cs->routerAddr = get_option_router(&garp.dhcp_packet);
-        if (arp_get_gw_hwaddr(cs) < 0) {
-            log_warning("%s: (%s) Failed to send request to get gateway and agent hardware addresses: %s",
-                        client_config.interface, __func__, strerror(errno));
-            return ARPR_FAIL;
-        }
         stop_dhcp_listen(cs);
         write_leasefile(temp_addr);
-        if (arp_announcement(cs) < 0) {
-            log_warning("%s: (%s) Failed to send first ARP announcement: %s",
-                        client_config.interface, __func__, strerror(errno));
-            // If we return ARPR_FAIL here, the state machine will get messed up since we
-            // do have a binding, we've just not announced it yet.  Ideally, we will note
-            // this issue and will try to announce again.
-        }
         if (client_config.quit_after_lease)
-            exit(EXIT_SUCCESS);
+            quit_after_lease_handler(cs);
         return ARPR_FREE;
     }
     long long rtts = garp.send_stats[ASEND_COLLISION_CHECK].ts +
@@ -538,6 +553,26 @@ int arp_collision_timeout(struct client_state_t cs[static 1], long long nowts)
     return ARPR_OK;
 }
 
+int arp_query_gateway(struct client_state_t cs[static 1])
+{
+    if (arp_get_gw_hwaddr(cs) < 0) {
+        log_warning("%s: (%s) Failed to send request to get gateway and agent hardware addresses: %s",
+                    client_config.interface, __func__, strerror(errno));
+        return ARPR_FAIL;
+    }
+    return ARPR_OK;
+}
+
+int arp_announce(struct client_state_t cs[static 1])
+{
+    if (arp_announcement(cs) < 0) {
+        log_warning("%s: (%s) Failed to send ARP announcement: %s",
+                    client_config.interface, __func__, strerror(errno));
+        return ARPR_FAIL;
+    }
+    return ARPR_OK;
+}
+
 int arp_do_defense(struct client_state_t cs[static 1])
 {
     // Even though the BPF will usually catch this case, sometimes there are

src/arp.h

@@ -117,6 +117,10 @@ int arp_gw_failed(struct client_state_t cs[static 1]);
 
 int arp_do_collision_check(struct client_state_t cs[static 1]);
 int arp_collision_timeout(struct client_state_t cs[static 1], long long nowts);
+
+int arp_query_gateway(struct client_state_t cs[static 1]);
+int arp_announce(struct client_state_t cs[static 1]);
+
 int arp_do_defense(struct client_state_t cs[static 1]);
 int arp_defense_timeout(struct client_state_t cs[static 1], long long nowts);
 int arp_do_gw_query(struct client_state_t cs[static 1]);

src/state.c

@@ -537,6 +537,8 @@ skip_to_requesting:
         if (arp_timeout) {
             int r = arp_collision_timeout(cs, nowts);
             if (r == ARPR_FREE) {
+                arp_query_gateway(cs); // XXX: Handle failure
+                arp_announce(cs); // XXX: Handle failure
                 break;
             } else if (r == ARPR_OK) {
             } else if (r == ARPR_FAIL) {