Socket code works in main but fails in other function - c

Question

The first code snippet is just of main all I am doing is calling the outOfMain function
int main(int argc , char* argv[]) {
outOfMain();
}
The second is outOfMain - The code I want to work
void outOfMain() {
printf("%s\n", "project 2 started");
int mpSockDescriptor = mp_socket(AF_INET, SOCK_MPTCP, 0);
struct sockaddr_in serverAddress;
serverAddress.sin_family = AF_INET;
serverAddress.sin_port = htons(5233);
serverAddress.sin_addr.s_addr = inet_addr("xxx.xxx.xx.xx");
struct sockaddr* sAddr = (struct sockaddr*)&serverAddress;
int mpConn = mp_connect( mpSockDescriptor, (struct sockaddr*)&serverAddress, sizeof(struct sockaddr));
if(mpConn) {
printf("failure to connect\n");
}
printf("adsf\n");
struct sockaddr_in clientAddress;
clientAddress.sin_family = AF_INET;
clientAddress.sin_port = htons(5233);
clientAddress.sin_addr.s_addr = inet_addr("localhost");
struct mptcp_header mpHeader;
mpHeader.seq_num = 1;
mpHeader.dest_addr = serverAddress;
mpHeader.src_addr = clientAddress;
mpHeader.total_bytes = sizeof("MPREQ 1");
mpHeader.ack_num = 1;
struct packet packing;
packing.header = &mpHeader;
char* sendReq = (char*) malloc(128*sizeof(char));
strcpy(sendReq, "MPREQ 1");
packing.data = (char*) malloc(128*sizeof(char));
strcpy(packing.data, sendReq);
printf("%s\n", packing.data);
printf("%d\n", mpSockDescriptor);
printf("%zu\n",mp_send(mpSockDescriptor, &packing, sizeof(packing), 0));
struct packet packRecv;
printf("adf\n");
printf("%d\n", mpSockDescriptor);
mp_recv(mpSockDescriptor, &packRecv, sizeof(struct packet), 0);
}
Then the third is the header file just to show that I am including outOfMain so the act of calling it isn't giving me the error
#ifndef MPTCP_H
#define MPTCP_H
// C libraries
#include <errno.h>
#include <netinet/in.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
// MPTCP macros
#define SOCK_MPTCP 2 // socket type for mptcp connections
#define RWIN 2048 // maximum receiver window
#define MSS 128 // sender maximum segment size
/******************************************************************************
* TCP data structures *
******************************************************************************/
/******************************************************************************
* packet header holds information about the current packet + connection *
******************************************************************************/
void outOfMain();
struct mptcp_header {
struct sockaddr_in dest_addr; // remote destination address
struct sockaddr_in src_addr; // local sender address
int seq_num; // sequence number ( first data byte )
int ack_num; // ACK number ( next expected data byte )
int total_bytes; // total bytes of data to transmit
};
/******************************************************************************
* packet holds information about the data contained + connection *
******************************************************************************/
struct packet {
struct mptcp_header * header; // pointer to packet header
char * data; // segment of data
};
struct sendStruct {
char** buff;
int portNumber;
struct sockaddr_in* cInfo;
};
/******************************************************************************
* TCP wrapper functions *
******************************************************************************/
/******************************************************************************
* receive UDP datagram(s) as TCP packet *
* - returns total bytes of data received *
******************************************************************************/
ssize_t mp_recv ( int sockfd, struct packet * recv_pkt, size_t data_len, int flags );
/******************************************************************************
* send UDP datagram(s) as TCP packet *
* - returns total bytes of data sent *
******************************************************************************/
ssize_t mp_send ( int sockfd, const struct packet * send_pkt, size_t data_len, int flags );
/******************************************************************************
* create connection with hostname, port *
* - returns 0 on success *
******************************************************************************/
int mp_connect( int sockfd, const struct sockaddr * addr, socklen_t addrlen );
/******************************************************************************
* create MPTCP socket *
* - returns socket descriptor for new connection *
******************************************************************************/
int mp_socket ( int domain, int type, int protocol );
/******************************************************************************
* prints packet header information + data load *
* - returns nothing, prints to standard out *
******************************************************************************/
void print_pkt( const struct packet * );
void failSuccess();
#endif // MPTCP_H
What I am doing in order is:
creating a multi-thread socket
Connecting that socket to a specific port and server address.
Sending a specific string to the server
Waiting for a response using mp_recv
What I don't understand is that when this exact same code is inside of main (), it works perfectly. But, when it is not in main(), it has a segfault 11 at the mp_recv function call. So I feel like the solution must have more to do with how C works and not my specific code.
Also, I need to have it outside of main() because I need to be able to use multi-threading.
I feel like I must be missing some elementary lesson in C right now.

Answer 1

You got lucky once, unlucky the other time. You have not initialized struct packet packRecv;.