From de23d2241d6fd8923c353296ab5c5b7db412970d Mon Sep 17 00:00:00 2001
From: "Nicholas J. Kain" <nicholas@kain.us>
Date: Wed, 30 Mar 2011 18:58:09 -0400
Subject: [PATCH] Improve timeout backoff.  It's a capped linear backoff.  RFC
 specifies capped randomized exponential, but I don't feel like incurring the
 cost when the cap is so low. Add comments for the dhcpMessage structure
 members.

---
 ndhc/options.c |  2 +-
 ndhc/packet.h  | 31 +++++++++++++++++--------------
 ndhc/timeout.c |  5 ++++-
 3 files changed, 22 insertions(+), 16 deletions(-)

diff --git a/ndhc/options.c b/ndhc/options.c
index bbd1f76..017635d 100644
--- a/ndhc/options.c
+++ b/ndhc/options.c
@@ -1,5 +1,5 @@
 /* options.c - DHCP options handling
- * Time-stamp: <2011-03-30 16:41:03 nk>
+ * Time-stamp: <2011-03-30 18:29:18 nk>
  *
  * (c) 2004-2011 Nicholas J. Kain <njkain at gmail dot com>
  *
diff --git a/ndhc/packet.h b/ndhc/packet.h
index aec2141..e7b4360 100644
--- a/ndhc/packet.h
+++ b/ndhc/packet.h
@@ -7,20 +7,23 @@
 #include "config.h"
 
 struct dhcpMessage {
-    uint8_t op;
-    uint8_t htype;
-    uint8_t hlen;
-    uint8_t hops;
-    uint32_t xid;
-    uint16_t secs;
-    uint16_t flags;
-    uint32_t ciaddr;
-    uint32_t yiaddr;
-    uint32_t siaddr;
-    uint32_t giaddr;
-    uint8_t chaddr[16];
-    uint8_t sname[64];
-    uint8_t file[128];
+    uint8_t op; // Message type: 1 = BOOTREQUEST for clients.
+    uint8_t htype; // ARP HW address type: always '1' for 10MB ethernet.
+    uint8_t hlen; // Hardware address length: always '6' for 10MB ethernet.
+    uint8_t hops; // Client sets to zero.
+    uint32_t xid;  // Transaction ID: random number identifying session
+    uint16_t secs; // Filled by client: seconds since client began address
+                   // aquisition or renewal process.
+    uint16_t flags; // DHCP flags
+    uint32_t ciaddr; // Client IP: only filled in if client is inBOUND, RENEW,
+                     // or REBINDING and can reply to ARP requests
+    uint32_t yiaddr; // 'your' (client) IP address
+    uint32_t siaddr; // IP address of next server to use in bootstrap; returned
+                     // in DHCPOFFER or DHCPACK by server
+    uint32_t giaddr; // relay agent IP: used when booting via relay agent
+    uint8_t chaddr[16]; // Client MAC address
+    uint8_t sname[64]; // Server host name (optional); null-terminated string
+    uint8_t file[128]; // boot file name, null-terminated string
     uint32_t cookie;
     uint8_t options[308]; /* 312 - cookie */
 };
diff --git a/ndhc/timeout.c b/ndhc/timeout.c
index 88dc3f3..9d2f2cb 100644
--- a/ndhc/timeout.c
+++ b/ndhc/timeout.c
@@ -9,6 +9,8 @@
 #include "arp.h"
 #include "log.h"
 
+
+#define DELAY_SEC (((RETRY_DELAY - (RETRY_DELAY / NUMPACKETS)) / NUMPACKETS) + 1)
 static void init_selecting_timeout(struct client_state_t *cs)
 {
     if (cs->packetNum < NUMPACKETS) {
@@ -17,7 +19,7 @@ static void init_selecting_timeout(struct client_state_t *cs)
         /* broadcast */
         send_discover(cs->xid, cs->requestedIP);
 
-        cs->timeout = ((cs->packetNum == NUMPACKETS - 1) ? 4 : 2) * 1000;
+        cs->timeout = DELAY_SEC * (cs->packetNum + 1);
         cs->packetNum++;
     } else {
         if (client_config.background_if_no_lease) {
@@ -32,6 +34,7 @@ static void init_selecting_timeout(struct client_state_t *cs)
         cs->timeout = RETRY_DELAY * 1000;
     }
 }
+#undef DELAY_SEC
 
 static void renew_requested_timeout(struct client_state_t *cs)
 {