Make the ARP-based lease address collision checks configurable in delay times

and number of probes.

ndhc/arp.c

@@ -1,6 +1,6 @@
 /* arp.c - arp ping checking
  *
- * Copyright (c) 2010-2011 Nicholas J. Kain <njkain at gmail dot com>
+ * Copyright (c) 2010-2013 Nicholas J. Kain <njkain at gmail dot com>
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -53,10 +53,10 @@
 #define ARP_RETRANS_DELAY 5000 // ms
 
 // From RFC5227
-#define PROBE_WAIT 1000            // initial random delay
+int arp_probe_wait = 1000;         // initial random delay (ms)
-#define PROBE_NUM 3                // number of probe packets
+int arp_probe_num = 3;             // number of probe packets
-#define PROBE_MIN 1000             // minimum delay until repeated probe
+int arp_probe_min = 1000;          // minimum delay until repeated probe (ms)
-#define PROBE_MAX 2000             // maximum delay until repeated probe
+int arp_probe_max = 2000;          // maximum delay until repeated probe (ms)
 #define ANNOUNCE_WAIT 2000         // delay before announcing
 #define ANNOUNCE_NUM 2             // number of Announcement packets
 #define ANNOUNCE_INTERVAL 2000     // time between Announcement packets
@@ -64,6 +64,7 @@
 #define RATE_LIMIT_INTERVAL 60000  // delay between successive attempts
 #define DEFEND_INTERVAL 10000      // minimum interval between defensive ARPs
 
+
 typedef enum {
     AS_NONE = 0,        // Nothing to react to wrt ARP
     AS_COLLISION_CHECK, // Checking to see if another host has our IP before
@@ -383,7 +384,7 @@ 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;
-    probe_wait_time = PROBE_WAIT;
+    probe_wait_time = arp_probe_wait;
     arp_wake_ts[AS_COLLISION_CHECK] = arp_check_start_ts + probe_wait_time;
     return 0;
 }
@@ -561,7 +562,7 @@ static int arp_is_query_reply(struct arpMsg *am)
 static int arp_gen_probe_wait(void)
 {
     // This is not a uniform distribution but it doesn't matter here.
-    return PROBE_MIN + rand() % (PROBE_MAX - PROBE_MIN);
+    return arp_probe_min + rand() % (arp_probe_max - arp_probe_min);
 }
 
 static void arp_defense_timeout(struct client_state_t *cs, long long nowts)
@@ -626,7 +627,7 @@ static void arp_collision_timeout(struct client_state_t *cs, long long nowts)
     arp_defense_timeout(cs, nowts);
 
     if (nowts >= arp_check_start_ts + ANNOUNCE_WAIT ||
-        arp_send_stats[ASEND_COLLISION_CHECK].count >= PROBE_NUM) {
+        arp_send_stats[ASEND_COLLISION_CHECK].count >= arp_probe_num) {
         arp_success(cs);
         return;
     }

ndhc/arp.h

@@ -53,6 +53,10 @@ struct arpMsg {
     uint8_t  pad[18];       // 2a pad for min. ethernet payload (60 bytes)
 };
 
+extern int arp_probe_wait;
+extern int arp_probe_num;
+extern int arp_probe_min;
+extern int arp_probe_max;
 extern int arp_relentless_def;
 
 void arp_reset_send_stats(void);

ndhc/ndhc.c

@@ -1,6 +1,6 @@
 /* ndhc.c - DHCP client
  *
- * Copyright (c) 2004-2012 Nicholas J. Kain <njkain at gmail dot com>
+ * Copyright (c) 2004-2013 Nicholas J. Kain <njkain at gmail dot com>
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -107,6 +107,10 @@ static void show_usage(void)
 "  -C, --chroot=DIR                Chroot to this directory\n"
 "  -d, --relentless-defense        Never back off in defending IP against\n"
 "                                  conflicting hosts (servers only)\n"
+"  -w, --arp-probe-wait            Time to delay before first ARP probe\n"
+"  -W, --arp-probe-num             Number of ARP probes before lease is ok\n"
+"  -m, --arp-probe-min             Min ms to wait for ARP response\n"
+"  -M, --arp-probe-max             Max ms to wait for ARP response\n"
 "  -v, --version                   Display version\n"
            );
     exit(EXIT_SUCCESS);
@@ -324,6 +328,10 @@ int main(int argc, char **argv)
         {"user",        required_argument,  0, 'u'},
         {"chroot",      required_argument,  0, 'C'},
         {"relentless-defense", no_argument, 0, 'd'},
+        {"arp-probe-wait", required_argument, 0, 'w'},
+        {"arp-probe-num", required_argument, 0, 'W'},
+        {"arp-probe-min", required_argument, 0, 'm'},
+        {"arp-probe-max", required_argument, 0, 'M'},
         {"version",     no_argument,        0, 'v'},
         {"help",        no_argument,        0, '?'},
         {0, 0, 0, 0}
@@ -331,8 +339,8 @@ int main(int argc, char **argv)
 
     while (1) {
         int option_index = 0;
-        c = getopt_long(argc, argv, "c:fbp:h:i:np:l:qr:V:u:C:dv", arg_options,
+        c = getopt_long(argc, argv, "c:fbp:h:i:np:l:qr:V:u:C:dw:W:m:M:v",
-                        &option_index);
+                        arg_options, &option_index);
         if (c == -1) break;
 
         switch (c) {
@@ -389,9 +397,34 @@ int main(int argc, char **argv)
             case 'd':
                 arp_relentless_def = 1;
                 break;
+            case 'w':
+            case 'W': {
+                int t = atoi(optarg);
+                if (t < 0)
+                    break;
+                if (c == 'w')
+                    arp_probe_wait = t;
+                else
+                    arp_probe_num = t;
+                break;
+            }
+            case 'm':
+            case 'M': {
+                int t = atoi(optarg);
+                if (c == 'm')
+                    arp_probe_min = t;
+                else
+                    arp_probe_max = t;
+                if (arp_probe_min > arp_probe_max) {
+                    t = arp_probe_max;
+                    arp_probe_max = arp_probe_min;
+                    arp_probe_min = t;
+                }
+                break;
+            }
             case 'v':
                 printf("ndhc %s, dhcp client.\n", NDHC_VERSION);
-                printf("Copyright (c) 2004-2012 Nicholas J. Kain\n"
+                printf("Copyright (c) 2004-2013 Nicholas J. Kain\n"
                        "All rights reserved.\n\n"
                        "Redistribution and use in source and binary forms, with or without\n"
                        "modification, are permitted provided that the following conditions are met:\n\n"