commit 102a50fa96ff797100631641bda0183669824223
author Dirk Ziegelmeier <dirk@ziegelmeier.net> Sat Dec 17 13:36:24 2016 +0100
committer Dirk Ziegelmeier <dirk@ziegelmeier.net> Sat Dec 17 13:36:24 2016 +0100
tree 95e27661cdd44069ba0b7047f431a4425dc8a8e8
parent bb8088d4986d9ac5a3a52706ec441f32b09ffdf6

Fix bug #39145: IGMP membership report for 224.0.0.1
Ensure allsystems group is always first in linked list

src/core/ipv4/igmp.c

diff --git a/src/core/ipv4/igmp.c b/src/core/ipv4/igmp.c
index 5ae7d9c..5ea2fda 100644
--- a/src/core/ipv4/igmp.c
+++ b/src/core/ipv4/igmp.c
@@ -244,6 +244,7 @@
 igmp_lookup_group(struct netif *ifp, const ip4_addr_t *addr)
 {
   struct igmp_group *group;
+  struct igmp_group *list_head = netif_igmp_data(ifp);
 
   /* Search if the group already exists */
   group = igmp_lookfor_group(ifp, addr);
@@ -251,7 +252,7 @@
     /* Group already exists. */
     return group;
   }
-
+  
   /* Group doesn't exist yet, create a new one */
   group = (struct igmp_group *)memp_malloc(MEMP_IGMP_GROUP);
   if (group != NULL) {
@@ -260,9 +261,21 @@
     group->group_state        = IGMP_GROUP_NON_MEMBER;
     group->last_reporter_flag = 0;
     group->use                = 0;
-    group->next               = netif_igmp_data(ifp);
 
-    netif_set_client_data(ifp, LWIP_NETIF_CLIENT_DATA_INDEX_IGMP, group);
+    /* Ensure allsystems group is always first in list */    
+    if (list_head == NULL) {
+      /* this is the first entry in linked list */
+      LWIP_ASSERT("igmp_lookup_group: first group must be allsystems",
+        (ip4_addr_cmp(addr, &allsystems) != 0));
+      group->next = NULL;
+      netif_set_client_data(ifp, LWIP_NETIF_CLIENT_DATA_INDEX_IGMP, group);
+    } else {
+      /* append _after_ first entry */
+      LWIP_ASSERT("igmp_lookup_group: all except first group must not be allsystems",
+        (ip4_addr_cmp(addr, &allsystems) == 0));
+      group->next = list_head->next;
+      list_head->next = group;
+    }
   }
 
   LWIP_DEBUGF(IGMP_DEBUG, ("igmp_lookup_group: %sallocated a new group with address ", (group?"":"impossible to ")));