Question

I’m trying to reproduce an example from Network Security with OpenSSL (by Chandra et al). The program consists of client.c server.c common.h and common.c. client.c simply creates a connection to the server on port 6012 and reads data from stdin and then send those data to the server. The server.c reads data from socket and writes it back out to stdout.

The problem is that server.c always get stuck in if(BIO_do_accept(acc) <= 0) at line 62 and never gets data sent from client.c, which runs perfectly fine. I later found the problem is that pthread_create(...) at line 66 ( which is defined as THREAD_CREATE(...) in common.h) failed and it returned 4294967295. Because THREAD_CREATE(...) failed, the program never get a chance to run do_server_loop in server_thread(...), which explains why the server never got the data from client.

How should I interpret the return values from pthread_create and how should I fix it?
PS. I later used strerror to convert 4294967295 and it returned “Unknown error”.

Any help will be much appreciated!

//////////////////////////////////////////////////

Here is server.c:

#include "common.h" 
void do_server_loop(BIO *conn)
{
    int err, nread;
    char buf[80];

    do
    {
        fprintf(stderr, "server_loop executed.\n");
        for(nread = 0; nread < sizeof(buf); nread += err)
        {
            err = BIO_read(conn, buf + nread, sizeof(buf) - nread);
            if(err <= 0){
                break;
            }
        }
        fwrite(buf, 1, nread, stdout);
    }
    while (err > 0);
}

void THREAD_CC server_thread(void *arg)
{
    fprintf(stderr, "server_thread(void *arg) executed.\n");
    BIO *client = (BIO *)arg;
#ifndef WIN32
    pthread_detach(pthread_self());
#endif
    fprintf(stderr, "Connection opened.\n");
    do_server_loop(client);
    fprintf(stderr, "Connection closed.\n");

    BIO_free(client);
    ERR_remove_state(0);
#ifdef WIN32
    _endthread();
#else
    return 0;
#endif
}


int main(int argc, char *argv[])
{
    BIO     *acc, *client;
    int thread_create_result;
    THREAD_TYPE tid;

    init_OpenSSL();

    acc = BIO_new_accept(PORT);
    if(!acc){
        int_error("Error creating server socket");
    }

    if(BIO_do_accept(acc) <= 0){
        int_error("Error binding server socket");   
    }
    for(;;)
    {
        if(BIO_do_accept(acc) <= 0){
            int_error("Error accepting connection");
        }
        client = BIO_pop(acc);
        thread_create_result = THREAD_CREATE(tid, server_thread, client);
        if(thread_create_result != 0){
            fprintf(stderr, "THREAD_CREATE failed! returns: %s.\n", \
                                            strerror(thread_create_result));
            fprintf(stderr, "thread_create_result has the value: %u.\n", \
                                            thread_create_result);
            exit(-1);
        }
    }

    BIO_free(acc);
    return 0;
}

Here is common.h

#include <errno.h>
#include <fcntl.h>
#include <netdb.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <openssl/bio.h>
#include <openssl/err.h>
#include <openssl/hmac.h>
#include <openssl/objects.h>
#include <openssl/rand.h>
#include <openssl/ssl.h>
#include <openssl/x509.h>
#include <openssl/x509v3.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <strings.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>


#ifndef WIN32
#include <pthread.h>
#define THREAD_CC *
#define THREAD_TYPE         pthread_t
#define THREAD_CREATE(tid, entry, arg)  pthread_create(&(tid), NULL, \
                                   (entry), (arg))
#else
#include <windows.h>
#include <process.h>
#define THREAD_CC              __cdecl
#define THREAD_TYPE            DWORD
#define THREAD_CREATE(tid, entry, arg) do { _beginthread((entry), 0, (arg));\
                        (tid) = GetCurrentThreadId();\
                       } while (0)
#endif

#define PORT    "6012"      //port
#define SERVER  "10.1.251.24"   //server address
#define CLIENT  "10.1.21.46"    //client address

#define int_error(msg) handle_error(__FILE__, __LINE__, msg)
void handle_error(const char *file, int lineno, const char *msg);

void init_OpenSSL(void);

Makefile:

CC = gcc
OPENSSLDIR = /usr/local/ssl
#CFLAGS = -g -Wall -W -I${OPENSSLDIR}/include -O2 -D_REENTRANT -D__EXTENSIONS__  
CFLAGS = -g -Wall -W -I${OPENSSLDIR}/include -O2

RPATH = -R${OPENSSLDIR}/lib
#LD = ${RPATH} -L${OPENSSLDIR}/lib -lssl -lcrypto -lsocket -lnsl -lpthread
LD = -L${OPENSSLDIR}/lib -lssl -lcrypto -lsocket -lnsl -pthread

OBJS = common.o

PROGS = server

all: ${PROGS}

server: server.o ${OBJS}
        ${CC} server.o ${OBJS} -o server ${LD}


clean:;
        ${RM} ${PROGS} *.ln *.BAK *.bak *.o

Answer 1

add -D_REENTRANT on compile command lines and -lpthread on the link command line.
-D_REENTRANT will tell C/C++ libraries that your program is in multithread mode and -lpthread just load the shared library libpthread.so at runtime. I found this at William Garrison’s POSIX threads tutorial and this link.

Here is the Makefile:

CC = gcc
OPENSSLDIR = /usr/local/ssl
CFLAGS = -g -Wall -W -I${OPENSSLDIR}/include -O2 -D_REENTRANT -D__EXTENSIONS__  

RPATH = -R${OPENSSLDIR}/lib
LD = ${RPATH} -L${OPENSSLDIR}/lib -lssl -lcrypto -lsocket -lnsl -lpthread

OBJS = common.o

PROGS = server

all: ${PROGS}

server: server.o ${OBJS}
        ${CC} server.o ${OBJS} -o server ${LD}


clean:;
        ${RM} ${PROGS} *.ln *.BAK *.bak *.o