Segmentation Fault error in nesC for Flooding packet acknowledgement using TinyOS - tinyos

Question

For my assignment, I am meant to implement Flooding on a network topology. The following is the code for which the when the packet has reached its final destination and I want to return an acknowledgement. The segmentation fault seems to happen at the if-statement: if(myMsg->protocol == PROTOCOL_PING). Why is this happening and how can it be fixed?
event message_t* receiveFlood.receive(message_t* msg, void* payload, uint8_t len){
dbg(FLOODING_CHANNEL, "Packet Received: %s\n", msg);
if(len==sizeof(pack)){
pack* myMsg=(pack*) payload;
if(myMsg->TTL == 0){
return msg;
}
if(CheckCache(myMsg)){
return msg;
}
//We have reached the destination of the packet
else if(TOS_NODE_ID == myMsg->dest){
dbg(GENERAL_CHANNEL, "The packet has reached its destination with the message: %s\n", myMsg->payload);
dbg(FLOODING_CHANNEL, "[Src:Dest] %d : %d\n", myMsg->src, myMsg->dest);
printf("Hello what is going on \n");
//This statement is the acknowledgement to the src NODE
if(myMsg->protocol == PROTOCOL_PING){
dbg(GENERAL_CHANNEL, "Acknowledged: %s\n");
dbg(FLOODING_CHANNEL, "[Dest:Src] %d : %d\n", myMsg->dest, myMsg->src);
dbg(GENERAL_CHANNEL, "Payload: %s\n:", myMsg->payload);
//Cache the packet
dbg(GENERAL_CHANNEL, "Now Storing msg into cache... %s\n");
NodeCache(myMsg);
return msg;
}
return msg;
}
dbg(FLOODING_CHANNEL, "Package Payload: %s\n", myMsg->payload);
return msg;
}
dbg(GENERAL_CHANNEL, "Unknown Packet Type %d\n", len);
return msg;
}
The following is the output result:
enter code here
Creating Topo!
Number of Motes 19
1 2 -54.0
2 3 -54.0
3 4 -54.0
4 5 -54.0
5 6 -54.0
6 7 -54.0
7 8 -54.0
8 9 -54.0
9 10 -54.0
10 11 -54.0
11 12 -54.0
12 13 -54.0
13 14 -54.0
14 15 -54.0
15 16 -54.0
16 17 -54.0
17 18 -54.0
18 19 -54.0
2 1 -54.0
3 2 -54.0
4 3 -54.0
5 4 -54.0
6 5 -54.0
7 6 -54.0
8 7 -54.0
9 8 -54.0
10 9 -54.0
11 10 -54.0
12 11 -54.0
13 12 -54.0
14 13 -54.0
15 14 -54.0
16 15 -54.0
17 16 -54.0
18 17 -54.0
19 18 -54.0
Creating noise model for 1
Creating noise model for 2
Creating noise model for 3
Creating noise model for 4
Creating noise model for 5
Creating noise model for 6
Creating noise model for 7
Creating noise model for 8
Creating noise model for 9
Creating noise model for 10
Creating noise model for 11
Creating noise model for 12
Creating noise model for 13
Creating noise model for 14
Creating noise model for 15
Creating noise model for 16
Creating noise model for 17
Creating noise model for 18
Creating noise model for 19
Adding Channel command
Adding Channel general
Adding Channel flooding
0:0:0.000000133 DEBUG (1): Booted
0:0:0.000000143 DEBUG (1): Radio On
0:0:0.000000266 DEBUG (2): Booted
0:0:0.000000276 DEBUG (2): Radio On
0:0:0.000000399 DEBUG (3): Booted
0:0:0.000000409 DEBUG (3): Radio On
0:0:0.000000533 DEBUG (4): Booted
0:0:0.000000543 DEBUG (4): Radio On
0:0:0.000000666 DEBUG (5): Booted
0:0:0.000000676 DEBUG (5): Radio On
0:0:0.000000799 DEBUG (6): Booted
0:0:0.000000809 DEBUG (6): Radio On
0:0:0.000000933 DEBUG (7): Booted
0:0:0.000000943 DEBUG (7): Radio On
0:0:0.000001066 DEBUG (8): Booted
0:0:0.000001076 DEBUG (8): Radio On
0:0:0.000001199 DEBUG (9): Booted
0:0:0.000001209 DEBUG (9): Radio On
0:0:0.000001333 DEBUG (10): Booted
0:0:0.000001343 DEBUG (10): Radio On
0:0:0.000001466 DEBUG (11): Booted
0:0:0.000001476 DEBUG (11): Radio On
0:0:0.000001599 DEBUG (12): Booted
0:0:0.000001609 DEBUG (12): Radio On
0:0:0.000001732 DEBUG (13): Booted
0:0:0.000001742 DEBUG (13): Radio On
0:0:0.000001866 DEBUG (14): Booted
0:0:0.000001876 DEBUG (14): Radio On
0:0:0.000001999 DEBUG (15): Booted
0:0:0.000002009 DEBUG (15): Radio On
0:0:0.000002132 DEBUG (16): Booted
0:0:0.000002142 DEBUG (16): Radio On
0:0:0.000002266 DEBUG (17): Booted
0:0:0.000002276 DEBUG (17): Radio On
0:0:0.000002399 DEBUG (18): Booted
0:0:0.000002409 DEBUG (18): Radio On
0:0:0.000002532 DEBUG (19): Booted
0:0:0.000002542 DEBUG (19): Radio On
0:1:57.945314110 DEBUG (1): A Command has been Issued.
0:1:57.945314110 DEBUG (1): Command Type: Ping
0:1:57.945314110 DEBUG (1): PING EVENT
0:1:57.945314110 DEBUG (1): Hello?
0:1:57.945314110 DEBUG (1): before floodsender
0:1:57.945314110 DEBUG (1): Flooding Network: Hello, World
0:1:57.945314110 DEBUG (1): after floodsender
0:1:57.967224226 DEBUG (2): Packet Received:
0:1:57.967224226 DEBUG (2): The packet has reached its destination with the message: Hello, World
0:1:57.967224226 DEBUG (2): [Src:Dest] 1 : 2
Hello what is going on
Segmentation fault (core dumped)