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//
// Created by Keuin on 2021/12/29.
//
#include <netdb.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include "logging.h"
#include "netcheck.h"
/**
* Check network availability.
* @return Zero if success, non-zero if failed.
*/
int check_network(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
}
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