test for catch infinite freezing (on TCP-sockets by default) on GNU/Linux

to-test.c

// -*- mode: c; coding: utf-8 -*-
//
// $ gcc -Wall -Werror -o to-test to-test.c && sudo ./to-test

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <strings.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <sys/types.h>
#include <sys/socket.h>

// ########## begin of configuration ##########

static const char * iface = "eth0"; // <--- !!! NEED TO CONFIG THIS !!!

static const char * remote_host = "google.com";
static const uint16_t remote_port = 443;

// ########## end of configuration ##########

int main (int argc, char *argv[]) {
    const size_t buf_size = 1024;
    char buffer[buf_size];
    const size_t cmd_buf_size = 1024;
    char cmd_buf[cmd_buf_size];
    int sock_fd = -1;
    int is_error = 0;
    int sock_optval;
    socklen_t sock_optlen = sizeof sock_optval;
    struct hostent *sock_hostent = 0;
    struct sockaddr_in sock_serv_addr = {0};
    
    printf("***** %s *****\n", "begin of test");
    
    printf("%s\n", "[step 1] creating socket...");
    
    sock_fd = socket(AF_INET, SOCK_STREAM, 0);
    if (sock_fd < 0) {
        printf("%s\n", "socket() error");
        return EXIT_FAILURE;
    }
    
    is_error = getsockopt(sock_fd, SOL_SOCKET, SO_KEEPALIVE, &sock_optval, &sock_optlen);
    if (is_error) {
        printf("%s\n", "getsockopt() error");
        return EXIT_FAILURE;
    }
    
    printf(
            "***** %s%d *****\n",
            "INFO: is used SO_KEEPALIVE by default for TCP-sockets? answer: ",
            sock_optval
            );
    
    printf("%s\n", "[step 2] connecting socket...");
    
    sock_hostent = gethostbyname(remote_host);
    if (!sock_hostent) {
        printf("%s\n", "gethostbyname() error");
        return EXIT_FAILURE;
    }
    
    bzero((char *)&sock_serv_addr, sizeof(sock_serv_addr));
    sock_serv_addr.sin_family = AF_INET;
    bcopy(
            (char *)sock_hostent->h_addr,
            (char *)&sock_serv_addr.sin_addr.s_addr,
            sock_hostent->h_length
            );
    sock_serv_addr.sin_port = htons(remote_port);
    
    is_error = connect(sock_fd, (struct sockaddr *)&sock_serv_addr, sizeof(sock_serv_addr));
    if (is_error) {
        printf("%s\n", "connect() error");
        return EXIT_FAILURE;
    }
    
    printf("%s\n", "[step 3] time waiting (1s)...");
    sleep(1);
    
    printf("%s\t[%s]\n", "[step 4] breaking down network...", iface);
    bzero(cmd_buf, sizeof(cmd_buf));
    sprintf(cmd_buf, "%s %s", "ip link set down dev", iface);
    printf("# %s\n", cmd_buf);
    system(cmd_buf);
    
    printf("%s\n", "[step 5] time waiting (15s)...");
    sleep(15);
    
    printf("%s\t[%s]\n", "[step 6] reestablishing up network...", iface);
    bzero(cmd_buf, sizeof(cmd_buf));
    sprintf(cmd_buf, "%s %s", "ip link set up dev", iface);
    printf("# %s\n", cmd_buf);
    system(cmd_buf);
    
    printf("%s\n", "[step 7] time waiting (1s)...");
    sleep(1);
    
    printf("%s\n", "[step 8] waiting of socket timeout (or we are freezed *infinity*?)...");
    recv(sock_fd, &buffer, sizeof(buffer), 0);
    
    printf("%s\n", "[step 9] closing socket...");
    is_error = close(sock_fd);
    if (is_error) {
        printf("%s\n", "close() error");
        return EXIT_FAILURE;
    }
    
    printf("***** %s *****\n", "end of test");
    
    return EXIT_SUCCESS;
}