patch #6463 (IGMP - Adding Random Delay): added define LWIP_RAND() for lwip-wide randomization (to be defined in cc.h)

CHANGELOG

@@ -19,6 +19,10 @@ HISTORY
 
   ++ New features:
 
+  2010-01-10: Simon Goldschmidt
+  * init.c, igmp.c: patch #6463 (IGMP - Adding Random Delay): added define
+    LWIP_RAND() for lwip-wide randomization (to be defined in cc.h)
+
   2009-12-31: Simon Goldschmidt
   * tcpip.c, init.c, memp.c, sys.c, memp_std.h, sys.h, tcpip.h
     added timers.c/.h: Separated timer implementation from semaphore/mbox

src/core/init.c

@@ -145,7 +145,7 @@
   #error "One and exactly one of LWIP_EVENT_API and LWIP_CALLBACK_API has to be enabled in your lwipopts.h"
 #endif
 /* There must be sufficient timeouts, taking into account requirements of the subsystems. */
-#if ((NO_SYS==0) && (MEMP_NUM_SYS_TIMEOUT < (LWIP_TCP + IP_REASSEMBLY + LWIP_ARP + (2*LWIP_DHCP) + LWIP_AUTOIP + LWIP_IGMP + LWIP_DNS + PPP_SUPPORT)))
+#if (MEMP_NUM_SYS_TIMEOUT < (LWIP_TCP + IP_REASSEMBLY + LWIP_ARP + (2*LWIP_DHCP) + LWIP_AUTOIP + LWIP_IGMP + LWIP_DNS + PPP_SUPPORT))
   #error "MEMP_NUM_SYS_TIMEOUT is too low to accomodate all required timeouts"
 #endif
 #if (IP_REASSEMBLY && (MEMP_NUM_REASSDATA > IP_REASS_MAX_PBUFS))
@@ -172,6 +172,9 @@
 #if !LWIP_ETHERNET && (LWIP_ARP || PPPOE_SUPPORT)
   #error "LWIP_ETHERNET needs to be turned on for LWIP_ARP or PPPOE_SUPPORT"
 #endif
+#ifndef LWIP_RAND
+  #error "LWIP_RAND() needs to be defined to a random-function returning an u32_t random value"
+#endif
 
 
 /* Compile-time checks for deprecated options.

src/core/ipv4/igmp.c

@@ -641,10 +641,7 @@ igmp_timeout(struct igmp_group *group)
 void
 igmp_start_timer(struct igmp_group *group, u8_t max_time)
 {
-  /**
-   * @todo Important !! this should be random 0 -> max_time. Find out how to do this
-   */
-  group->timer = max_time;
+  group->timer = LWIP_RAND() % max_time;
 }
 
 /**