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//
// Created by Keuin on 2021/12/29.
//
#include <netdb.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include "logging.h"
#include "netcheck.h"
#include "validate.h"
/**
* Check network availability by testing a tcp communication.
* @return Zero if success, non-zero if failed.
*/
int check_tcp(void *logger) {
#define RETURN(r) do { rv = (r); goto RET; } while(0)
#define READ_SIZE 32
int sock = -1, rv = 0;
struct sockaddr_in serv_addr;
const char *msg = "GET / HTTP/1.1\r\n"
"Host: www.gov.cn\r\n"
"\r\n";
if ((sock = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
perror("socket()");
log_error(logger, "socket() failed.");
RETURN(-1);
}
const struct hostent *host = gethostbyname("www.gov.cn"); // TODO cache this
if (!host) {
herror("gethostbyname()");
log_error(logger, "Cannot resolve test host.");
RETURN(-1);
}
if (host->h_length <= 0) {
log_error(logger, "Test host does not have at least one address.");
RETURN(-1);
}
serv_addr.sin_family = AF_INET;
serv_addr.sin_port = htons(80);
serv_addr.sin_addr = **((struct in_addr **) host->h_addr_list);
if (connect(sock, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0) {
log_error(logger, "connect() failed.");
RETURN(-1);
}
ssize_t ss = 0; // send size
while (ss < strlen(msg)) {
ssize_t rd = send(sock, msg, strlen(msg), 0);
if (rd < 0) {
perror("send()");
log_error(logger, "send() failed.");
RETURN(-1);
}
ss += rd;
}
log_debug(logger, "HTTP request is sent. Reading response.");
char response[READ_SIZE] = {0};
ssize_t rs = 0; // receive size
while (rs < READ_SIZE) {
ssize_t rd = read(sock, response, READ_SIZE - rs);
if (rd < 0) {
perror("read()");
log_error(logger, "read() failed.");
RETURN(-1);
} else {
rs += rd;
}
}
const char *expected = "HTTP/1.1 200 OK\r\n";
if (memcmp(response, expected, strlen(expected)) != 0) {
char buf[64];
snprintf(buf, 63, "Unexpected response: %s", response);
log_error(logger, buf);
RETURN(-1);
}
RETURN(0);
RET:
if (sock >= 0) close(sock);
return rv;
#undef RETURN
#undef READ_SIZE
}
/**
* Check network availability by pinging a remote host.
* Note that this routine requires an external ping program.
* @return Zero if success, non-zero if failed.
* @param logger the logger.
* @param dest the destination host, whether a domain or an ip address.
* @param ping path to the ping executable. If null, will use `/bin/ping`.
* @return Zero if success, non-zero if failed.
*/
int check_ping(void *logger, const char *dest, const char *ping) {
if (!is_valid_ipv4(dest)) {
log_error(logger, "dest is not a valid IPv4 address.");
return -1;
}
#define BUFLEN 1024
#define RETURN(r) do { rv = (r); goto CP_RET; } while(0)
int rv = 0;
// Copied from https://stackoverflow.com/questions/8189935/is-there-any-way-to-ping-a-specific-ip-address-with-c
if (ping == NULL) ping = "/bin/ping";
int pipe_arr[2] = {-1};
char buf[BUFLEN] = {0};
// Create pipe - pipe_arr[0] is "reading end", pipe_arr[1] is "writing end"
if (pipe(pipe_arr)) {
perror("pipe()");
log_error(logger, "pipe() failed.");
return -1;
}
if (fork() == 0) {
// child
if (dup2(pipe_arr[1], STDOUT_FILENO) < 0) {
log_error(logger, "dup2() failed.");
exit(-1);
}
execl(ping, "ping", "-c 3", dest, (char *) NULL);
} else {
// parent
if (wait(NULL) < 0) {
perror("wait()");
log_error(logger, "wait() failed.");
RETURN(-1);
}
if (read(pipe_arr[0], buf, BUFLEN) < 0) {
perror("read()");
log_error(logger, "read() failed.");
RETURN(-1);
}
}
CP_RET:
if (pipe_arr[0] >= 0) close(pipe_arr[0]);
if (pipe_arr[1] >= 0) close(pipe_arr[1]);
return (rv) ? (rv) : (strstr(buf, "time=") == NULL);
#undef BUFLEN
#undef RETURN
}
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