C 语言 : gethostbyaddr() return : 不允许操作
C language : gethostbyaddr() return : Operation not permitted
目前我正在尝试制作一个类似 ping 的程序并且它工作得很好但是我在 DNS_lookup()
上遇到了问题
这是我的函数：
char *DNS_reverse_lookup(struct sockaddr_in *host_addr)
{
if (host_addr == NULL)
{
printf("host_addr is empty.\n");
return NULL;
}
struct hostent *host_info = NULL;
host_info = gethostbyaddr(&host_addr->sin_addr.s_addr, sizeof(*host_addr), host_addr->sin_family);
if (host_info == NULL)
{
printf("%s:%d : gethostbyaddr() failed : %s\n", __FILE__, __LINE__, strerror(h_errno));
return NULL;
}
return host_info->h_name;
}
这里是 gethostbyaddr() return 某些域不允许操作，例如 google.com 但对于我的 ovh 服务器，它是 return 预期的结果，我不知道为什么
有人可以解释一下吗？
这是我的全部代码：
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <errno.h>
#include <netdb.h>
#include <sys/types.h>
#include <sys/time.h>
#include <time.h>
#include <netinet/ip_icmp.h>
#include <signal.h>
#include <ifaddrs.h>
#include "globaldata/gd.h"
#include "netsocket/netsocket.h"
// packet size
#define PING_PKT_S 64
// Automatic port number
#define PORT_NB 0
#define PING_SLEEP_RATE 1000000
// Give the timeout delay for receiving packets
// In seconds
#define RECV_TIMEOUT 2
struct icmp_pkt {
struct icmphdr header;
char msg[PING_PKT_S - sizeof(struct icmphdr)];
};
void sigintHandler(int sig_num);
unsigned short checksum(void *b, int len);
struct sockaddr_in *DNS_lookup(char *host_domain_name);
char *DNS_reverse_lookup(struct sockaddr_in *host_addr);
void send_ping(Socket_t *socket, char *ping_ip, char *host_domain_name);
GlobalData gd;
int main(int argc, char *argv[])
{
/* Declaration */
// information about the host
struct sockaddr_in *host_addr = NULL;
socklen_t host_addr_len = sizeof(*host_addr);
Socket_t *socket = NULL;
char *host_domain_name;
int opt_value = 0, i = 0;
FILE *socket_file = NULL;
int arg_port = 0;
int port = 0;
struct ifaddrs *ifaces;
struct ifaddrs *tmp = NULL;
/* Allocation */
socket = SOCKET_New();
/* Initialisation */
// Correct syntax
if (argc < 2)
{
printf("\nFormat %s <address>\n", argv[0]);
goto FatalError;
}
for (i = 0 ; argv[i] != 0 ; i++)
{
if (strcmp(argv[i], "-p") == 0)
{
arg_port = i;
}
}
if (arg_port)
{
port = atoi(argv[arg_port+1]);
printf("port = %d\n", port);
}
// loop while the ping is performed
gd.ping_loop = 1;
// Open socket
if (SOCKET_OpenSocket(socket, AF_INET, SOCK_RAW, IPPROTO_ICMP) == NULL)
{
printf("SOCKET_OpenSocket() failed.\n");
goto FatalError;
}
opt_value = 1;
if (setsockopt(socket->sockfd, SOL_SOCKET, SO_REUSEADDR, &opt_value, sizeof(opt_value)) == -1)
{
printf("setsockopt() failed : %s\n", strerror(errno));
}
if (SOCKET_SetAddr(socket, inet_addr(argv[1]), AF_INET, port, 5) == NULL)
{
printf("SOCKET_SetAddr() failed?\n");
goto FatalError;
}
// Get host domain name (if there is)
host_domain_name = DNS_reverse_lookup(&socket->addr);
if (host_domain_name == NULL)
{
printf("DNS_reverse_lookup() failed.\n");
host_domain_name = 0;
// goto FatalError;
}
printf("host domain name = %s (%s)\n", host_domain_name, argv[1]);
// printf("\nsockaddr :\nIP = %x\nPort = %d\nFamily = %d\n", socket->addr.sin_addr.s_addr, socket->addr.sin_port, socket->addr.sin_family);
// if (SOCKET_BindToSocket(socket) == NULL)
// {
// printf("SOCKET_BindToSocket() failed.\n");
// goto FatalError;
// }
// handle interrupt signal
signal(SIGINT, sigintHandler);
send_ping(socket, argv[1], host_domain_name);
/* Leave */
if (socket != NULL)
{
if (socket->sockfd > 0)
{
shutdown(socket->sockfd, SHUT_RDWR);
close(socket->sockfd);
printf("\nsocket closed.\n");
}
socket = SOCKET_Free(socket);
}
printf("Terminated : Without Error.\n");
return EXIT_SUCCESS;
FatalError:
if (socket != NULL)
{
if (socket->sockfd > 0)
{
shutdown(socket->sockfd, SHUT_RDWR);
close(socket->sockfd);
printf("\nsocket closed.\n");
}
socket = SOCKET_Free(socket);
}
printf("Terminated : Fatal Error.\n");
return EXIT_FAILURE;
}
void sigintHandler(int sig_num)
{
gd.ping_loop = 0;
}
unsigned short checksum(void *b, int len)
{
unsigned short *buf = b;
unsigned int sum = 0;
unsigned short result;
for (sum = 0 ; len > 1 ; len -= 2)
{
sum += *buf++;
}
if (len == 1)
{
sum += *(unsigned char *)buf;
}
sum = (sum >> 16) + (sum & 0xFFFF);
sum += (sum >> 16);
result = ~sum;
return result;
}
// Return struct sockaddr_in *ptr on success or 0 on error
struct sockaddr_in *DNS_lookup(char *host_domain_name)
{
printf("\nResolving DNS...\n");
// store host info in struct hostent
struct hostent *host_info = NULL;
static struct sockaddr_in host_addr;
memset(&host_addr, 0, sizeof(host_addr));
if ((host_info = gethostbyname(host_domain_name)) == NULL)
{
printf("%s:%d : gethostbyname() failed %s\n", __FILE__, __LINE__, strerror(h_errno));
return NULL;
}
host_addr.sin_addr.s_addr = inet_addr(host_info->h_addr_list[0]);
host_addr.sin_family = host_info->h_addrtype;
host_addr.sin_port = htons(PORT_NB);
printf("Resolved.\n\n");
return &host_addr;
}
// Return char *host_domain_name on success or 0 on error
char *DNS_reverse_lookup(struct sockaddr_in *host_addr)
{
if (host_addr == NULL)
{
printf("host_addr is empty.\n");
return NULL;
}
struct hostent *host_info = NULL;
host_info = gethostbyaddr(&host_addr->sin_addr.s_addr, sizeof(*host_addr), host_addr->sin_family);
if (host_info == NULL)
{
printf("%s:%d : gethostbyaddr() failed : %s\n", __FILE__, __LINE__, strerror(h_errno));
return NULL;
}
return host_info->h_name;
}
void send_ping(Socket_t *socket, char *ping_ip, char *host_domain_name)
{
if (socket == NULL)
{
printf("%s:%d : Bad socket.\n", __FILE__, __LINE__);
return;
}
if (socket->sockfd <= 0)
{
printf("%s:%d : Bad socket file descriptor.\n", __FILE__, __LINE__);
}
int ttl_value, msg_count, i, addr_len, flag, msg_received_count;
struct icmp_pkt packet;
struct sockaddr_in r_addr;
long double rtt_msec, total_msec;
struct timespec time_start, time_end, tfs, tfe;
struct timeval tv_out;
tv_out.tv_sec = RECV_TIMEOUT;
tv_out.tv_usec = 0;
ttl_value = 64;
msg_count = 0;
i = 0;
addr_len = 0;
flag = 1;
msg_received_count = 0;
rtt_msec = total_msec = 0.0;
// time start
clock_gettime(CLOCK_MONOTONIC, &tfs);
// SOL = Set Option Level
// SO = Set Option
// Set time to live value
if (setsockopt(socket->sockfd, SOL_IP, IP_TTL, &ttl_value, sizeof(ttl_value)) == -1)
{
printf("%s:%d : setsockopt() failed : %s\n", __FILE__, __LINE__, strerror(errno));
return;
}
printf("Socket set to TTL : %d\n", ttl_value);
// Set timeout of receiving setting
if (setsockopt(socket->sockfd, SOL_SOCKET, SO_RCVTIMEO, (const char *)&tv_out, sizeof(tv_out)) == -1)
{
printf("%s:%d : setsockopt() failed : %s\n", __FILE__, __LINE__, strerror(errno));
return;
}
printf("Ping to %s (%s).\n", host_domain_name, ping_ip);
while (gd.ping_loop)
{
// flag is whether packet was sent or not
flag = 1;
// filling packet
memset(&packet, 0, sizeof(packet));
packet.header.type = ICMP_ECHO;
packet.header.un.echo.id = getpid();
for (i = 0 ; i < sizeof(packet.msg) ; i++)
{
packet.msg[i] = '[=12=]';
}
char message[] = "Anything";
strncpy(packet.msg, message, strlen(message));
packet.header.un.echo.sequence = msg_count++;
packet.header.checksum = checksum(&packet, sizeof(packet));
usleep(PING_SLEEP_RATE);
// send packet
clock_gettime(CLOCK_MONOTONIC, &time_start);
// if (write(socket->sockfd, &packet, sizeof(packet)) == -1)
// {
// printf("%s:%d : write() failed : %s\n", __FILE__, __LINE__, strerror(errno));
// flag = 0;
// }
if (sendto(socket->sockfd, &packet, sizeof(packet), 0, (struct sockaddr *)&socket->addr, socket->addr_len) == -1)
{
printf("%s:%d : sento() failed : %s\n", __FILE__, __LINE__, strerror(errno));
return;
}
// receiving packet
// printf("reading packet...\n");
// if (read(socket->sockfd, &packet, sizeof(packet)) == -1 && msg_count > 1)
// {
// printf("%s:%d : read() failed : %s\n", __FILE__, __LINE__, strerror(errno));
// flag = 0;
// }
if (recvfrom(socket->sockfd, &packet, sizeof(packet), 0, (struct sockaddr *)&socket->addr, &socket->addr_len) == -1)
{
printf("%s:%d : recvfrom() failed : %s\n", __FILE__, __LINE__, strerror(errno));
return;
}
else
{
clock_gettime(CLOCK_MONOTONIC, &time_end);
double time_elapsed = ((double)time_end.tv_nsec - (double)time_start.tv_nsec) / 1000000.0;
printf("time elapsed = %.4f\n", time_elapsed);
rtt_msec = (double)(time_end.tv_sec - time_start.tv_sec) * 1000.0 + time_elapsed;
// case packet wasn't sent or received
if (!flag)
{
printf("%s:%d : ERROR : Packet received with ICMP type %d code %d\n", __FILE__, __LINE__, packet.header.type, packet.header.code);
}else{
printf("%d bytes from %d (h: %s) (%s) msg_seq=%d ttl=%d rtt = %Lf ms.\n", PING_PKT_S, socket->addr.sin_family, host_domain_name, ping_ip, msg_count, ttl_value, rtt_msec);
msg_received_count++;
}
}
}
clock_gettime(CLOCK_MONOTONIC, &tfe);
double time_elapsed = ((double)(tfe.tv_nsec - tfs.tv_nsec)) / 1000000.0;
total_msec = (tfe.tv_sec - tfs.tv_sec) * 1000 + time_elapsed;
printf("\n===%s ping statistics===\n", ping_ip);
printf("\n%d packets sent, %d packets received, %f percent packet loss. Total time: %Lf ms.\n\n", msg_count, msg_received_count, (double)((msg_count - msg_received_count)/msg_count) * 100.0, total_msec);
}
终端执行：
kali@kali:~/Code/Network/Ping$ sudo ./pingto 151.101.65.69
main.c:232 : gethostbyaddr() failed : Operation not permitted
DNS_reverse_lookup() failed.
host domain name = (null) (151.101.65.69)
Socket set to TTL : 64
Ping to (null) (151.101.65.69).
time elapsed = 8.1787
64 bytes from 2 (h: (null)) (151.101.65.69) msg_seq=1 ttl=64 rtt = 8.178748 ms.
time elapsed = 7.9054
64 bytes from 2 (h: (null)) (151.101.65.69) msg_seq=2 ttl=64 rtt = 7.905438 ms.
time elapsed = 8.2425
64 bytes from 2 (h: (null)) (151.101.65.69) msg_seq=3 ttl=64 rtt = 8.242489 ms.
^Ctime elapsed = 7.9805
64 bytes from 2 (h: (null)) (151.101.65.69) msg_seq=4 ttl=64 rtt = 7.980547 ms.
===151.101.65.69 ping statistics===
4 packets sent, 4 packets received, 0.000000 percent packet loss. Total time: 3494.951433 ms.
socket closed.
Terminated : Without Error.
您没有正确解码错误代码。
h_errno的值与errno对应的值不对应，所以无法使用strerror获取错误文本。
有一个名为 hstrerror 的函数，其功能与 strerror 相同，但用于 gethostbyname 和其他相关函数返回的错误代码。
手册页中列出的错误代码如下：
HOST_NOT_FOUND
The specified host is unknown.
NO_ADDRESS or NO_DATA
The requested name is valid but does not have an IP address.
NO_RECOVERY
A nonrecoverable name server error occurred.
TRY_AGAIN
A temporary error occurred on an authoritative name server. Try
again later.
“不允许操作”代码是 EPERM，在我的系统上是 1。该代码在我的系统上对应于 HOST_NOT_FOUND，所以假设您的错误代码与实际的相同您看到的错误。
目前我正在尝试制作一个类似 ping 的程序并且它工作得很好但是我在 DNS_lookup()
上遇到了问题这是我的函数：
char *DNS_reverse_lookup(struct sockaddr_in *host_addr)
{
if (host_addr == NULL)
{
printf("host_addr is empty.\n");
return NULL;
}
struct hostent *host_info = NULL;
host_info = gethostbyaddr(&host_addr->sin_addr.s_addr, sizeof(*host_addr), host_addr->sin_family);
if (host_info == NULL)
{
printf("%s:%d : gethostbyaddr() failed : %s\n", __FILE__, __LINE__, strerror(h_errno));
return NULL;
}
return host_info->h_name;
}
这里是 gethostbyaddr() return 某些域不允许操作，例如 google.com 但对于我的 ovh 服务器，它是 return 预期的结果，我不知道为什么
有人可以解释一下吗？
这是我的全部代码：
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <errno.h>
#include <netdb.h>
#include <sys/types.h>
#include <sys/time.h>
#include <time.h>
#include <netinet/ip_icmp.h>
#include <signal.h>
#include <ifaddrs.h>
#include "globaldata/gd.h"
#include "netsocket/netsocket.h"
// packet size
#define PING_PKT_S 64
// Automatic port number
#define PORT_NB 0
#define PING_SLEEP_RATE 1000000
// Give the timeout delay for receiving packets
// In seconds
#define RECV_TIMEOUT 2
struct icmp_pkt {
struct icmphdr header;
char msg[PING_PKT_S - sizeof(struct icmphdr)];
};
void sigintHandler(int sig_num);
unsigned short checksum(void *b, int len);
struct sockaddr_in *DNS_lookup(char *host_domain_name);
char *DNS_reverse_lookup(struct sockaddr_in *host_addr);
void send_ping(Socket_t *socket, char *ping_ip, char *host_domain_name);
GlobalData gd;
int main(int argc, char *argv[])
{
/* Declaration */
// information about the host
struct sockaddr_in *host_addr = NULL;
socklen_t host_addr_len = sizeof(*host_addr);
Socket_t *socket = NULL;
char *host_domain_name;
int opt_value = 0, i = 0;
FILE *socket_file = NULL;
int arg_port = 0;
int port = 0;
struct ifaddrs *ifaces;
struct ifaddrs *tmp = NULL;
/* Allocation */
socket = SOCKET_New();
/* Initialisation */
// Correct syntax
if (argc < 2)
{
printf("\nFormat %s <address>\n", argv[0]);
goto FatalError;
}
for (i = 0 ; argv[i] != 0 ; i++)
{
if (strcmp(argv[i], "-p") == 0)
{
arg_port = i;
}
}
if (arg_port)
{
port = atoi(argv[arg_port+1]);
printf("port = %d\n", port);
}
// loop while the ping is performed
gd.ping_loop = 1;
// Open socket
if (SOCKET_OpenSocket(socket, AF_INET, SOCK_RAW, IPPROTO_ICMP) == NULL)
{
printf("SOCKET_OpenSocket() failed.\n");
goto FatalError;
}
opt_value = 1;
if (setsockopt(socket->sockfd, SOL_SOCKET, SO_REUSEADDR, &opt_value, sizeof(opt_value)) == -1)
{
printf("setsockopt() failed : %s\n", strerror(errno));
}
if (SOCKET_SetAddr(socket, inet_addr(argv[1]), AF_INET, port, 5) == NULL)
{
printf("SOCKET_SetAddr() failed?\n");
goto FatalError;
}
// Get host domain name (if there is)
host_domain_name = DNS_reverse_lookup(&socket->addr);
if (host_domain_name == NULL)
{
printf("DNS_reverse_lookup() failed.\n");
host_domain_name = 0;
// goto FatalError;
}
printf("host domain name = %s (%s)\n", host_domain_name, argv[1]);
// printf("\nsockaddr :\nIP = %x\nPort = %d\nFamily = %d\n", socket->addr.sin_addr.s_addr, socket->addr.sin_port, socket->addr.sin_family);
// if (SOCKET_BindToSocket(socket) == NULL)
// {
// printf("SOCKET_BindToSocket() failed.\n");
// goto FatalError;
// }
// handle interrupt signal
signal(SIGINT, sigintHandler);
send_ping(socket, argv[1], host_domain_name);
/* Leave */
if (socket != NULL)
{
if (socket->sockfd > 0)
{
shutdown(socket->sockfd, SHUT_RDWR);
close(socket->sockfd);
printf("\nsocket closed.\n");
}
socket = SOCKET_Free(socket);
}
printf("Terminated : Without Error.\n");
return EXIT_SUCCESS;
FatalError:
if (socket != NULL)
{
if (socket->sockfd > 0)
{
shutdown(socket->sockfd, SHUT_RDWR);
close(socket->sockfd);
printf("\nsocket closed.\n");
}
socket = SOCKET_Free(socket);
}
printf("Terminated : Fatal Error.\n");
return EXIT_FAILURE;
}
void sigintHandler(int sig_num)
{
gd.ping_loop = 0;
}
unsigned short checksum(void *b, int len)
{
unsigned short *buf = b;
unsigned int sum = 0;
unsigned short result;
for (sum = 0 ; len > 1 ; len -= 2)
{
sum += *buf++;
}
if (len == 1)
{
sum += *(unsigned char *)buf;
}
sum = (sum >> 16) + (sum & 0xFFFF);
sum += (sum >> 16);
result = ~sum;
return result;
}
// Return struct sockaddr_in *ptr on success or 0 on error
struct sockaddr_in *DNS_lookup(char *host_domain_name)
{
printf("\nResolving DNS...\n");
// store host info in struct hostent
struct hostent *host_info = NULL;
static struct sockaddr_in host_addr;
memset(&host_addr, 0, sizeof(host_addr));
if ((host_info = gethostbyname(host_domain_name)) == NULL)
{
printf("%s:%d : gethostbyname() failed %s\n", __FILE__, __LINE__, strerror(h_errno));
return NULL;
}
host_addr.sin_addr.s_addr = inet_addr(host_info->h_addr_list[0]);
host_addr.sin_family = host_info->h_addrtype;
host_addr.sin_port = htons(PORT_NB);
printf("Resolved.\n\n");
return &host_addr;
}
// Return char *host_domain_name on success or 0 on error
char *DNS_reverse_lookup(struct sockaddr_in *host_addr)
{
if (host_addr == NULL)
{
printf("host_addr is empty.\n");
return NULL;
}
struct hostent *host_info = NULL;
host_info = gethostbyaddr(&host_addr->sin_addr.s_addr, sizeof(*host_addr), host_addr->sin_family);
if (host_info == NULL)
{
printf("%s:%d : gethostbyaddr() failed : %s\n", __FILE__, __LINE__, strerror(h_errno));
return NULL;
}
return host_info->h_name;
}
void send_ping(Socket_t *socket, char *ping_ip, char *host_domain_name)
{
if (socket == NULL)
{
printf("%s:%d : Bad socket.\n", __FILE__, __LINE__);
return;
}
if (socket->sockfd <= 0)
{
printf("%s:%d : Bad socket file descriptor.\n", __FILE__, __LINE__);
}
int ttl_value, msg_count, i, addr_len, flag, msg_received_count;
struct icmp_pkt packet;
struct sockaddr_in r_addr;
long double rtt_msec, total_msec;
struct timespec time_start, time_end, tfs, tfe;
struct timeval tv_out;
tv_out.tv_sec = RECV_TIMEOUT;
tv_out.tv_usec = 0;
ttl_value = 64;
msg_count = 0;
i = 0;
addr_len = 0;
flag = 1;
msg_received_count = 0;
rtt_msec = total_msec = 0.0;
// time start
clock_gettime(CLOCK_MONOTONIC, &tfs);
// SOL = Set Option Level
// SO = Set Option
// Set time to live value
if (setsockopt(socket->sockfd, SOL_IP, IP_TTL, &ttl_value, sizeof(ttl_value)) == -1)
{
printf("%s:%d : setsockopt() failed : %s\n", __FILE__, __LINE__, strerror(errno));
return;
}
printf("Socket set to TTL : %d\n", ttl_value);
// Set timeout of receiving setting
if (setsockopt(socket->sockfd, SOL_SOCKET, SO_RCVTIMEO, (const char *)&tv_out, sizeof(tv_out)) == -1)
{
printf("%s:%d : setsockopt() failed : %s\n", __FILE__, __LINE__, strerror(errno));
return;
}
printf("Ping to %s (%s).\n", host_domain_name, ping_ip);
while (gd.ping_loop)
{
// flag is whether packet was sent or not
flag = 1;
// filling packet
memset(&packet, 0, sizeof(packet));
packet.header.type = ICMP_ECHO;
packet.header.un.echo.id = getpid();
for (i = 0 ; i < sizeof(packet.msg) ; i++)
{
packet.msg[i] = '[=12=]';
}
char message[] = "Anything";
strncpy(packet.msg, message, strlen(message));
packet.header.un.echo.sequence = msg_count++;
packet.header.checksum = checksum(&packet, sizeof(packet));
usleep(PING_SLEEP_RATE);
// send packet
clock_gettime(CLOCK_MONOTONIC, &time_start);
// if (write(socket->sockfd, &packet, sizeof(packet)) == -1)
// {
// printf("%s:%d : write() failed : %s\n", __FILE__, __LINE__, strerror(errno));
// flag = 0;
// }
if (sendto(socket->sockfd, &packet, sizeof(packet), 0, (struct sockaddr *)&socket->addr, socket->addr_len) == -1)
{
printf("%s:%d : sento() failed : %s\n", __FILE__, __LINE__, strerror(errno));
return;
}
// receiving packet
// printf("reading packet...\n");
// if (read(socket->sockfd, &packet, sizeof(packet)) == -1 && msg_count > 1)
// {
// printf("%s:%d : read() failed : %s\n", __FILE__, __LINE__, strerror(errno));
// flag = 0;
// }
if (recvfrom(socket->sockfd, &packet, sizeof(packet), 0, (struct sockaddr *)&socket->addr, &socket->addr_len) == -1)
{
printf("%s:%d : recvfrom() failed : %s\n", __FILE__, __LINE__, strerror(errno));
return;
}
else
{
clock_gettime(CLOCK_MONOTONIC, &time_end);
double time_elapsed = ((double)time_end.tv_nsec - (double)time_start.tv_nsec) / 1000000.0;
printf("time elapsed = %.4f\n", time_elapsed);
rtt_msec = (double)(time_end.tv_sec - time_start.tv_sec) * 1000.0 + time_elapsed;
// case packet wasn't sent or received
if (!flag)
{
printf("%s:%d : ERROR : Packet received with ICMP type %d code %d\n", __FILE__, __LINE__, packet.header.type, packet.header.code);
}else{
printf("%d bytes from %d (h: %s) (%s) msg_seq=%d ttl=%d rtt = %Lf ms.\n", PING_PKT_S, socket->addr.sin_family, host_domain_name, ping_ip, msg_count, ttl_value, rtt_msec);
msg_received_count++;
}
}
}
clock_gettime(CLOCK_MONOTONIC, &tfe);
double time_elapsed = ((double)(tfe.tv_nsec - tfs.tv_nsec)) / 1000000.0;
total_msec = (tfe.tv_sec - tfs.tv_sec) * 1000 + time_elapsed;
printf("\n===%s ping statistics===\n", ping_ip);
printf("\n%d packets sent, %d packets received, %f percent packet loss. Total time: %Lf ms.\n\n", msg_count, msg_received_count, (double)((msg_count - msg_received_count)/msg_count) * 100.0, total_msec);
}
终端执行：
kali@kali:~/Code/Network/Ping$ sudo ./pingto 151.101.65.69
main.c:232 : gethostbyaddr() failed : Operation not permitted
DNS_reverse_lookup() failed.
host domain name = (null) (151.101.65.69)
Socket set to TTL : 64
Ping to (null) (151.101.65.69).
time elapsed = 8.1787
64 bytes from 2 (h: (null)) (151.101.65.69) msg_seq=1 ttl=64 rtt = 8.178748 ms.
time elapsed = 7.9054
64 bytes from 2 (h: (null)) (151.101.65.69) msg_seq=2 ttl=64 rtt = 7.905438 ms.
time elapsed = 8.2425
64 bytes from 2 (h: (null)) (151.101.65.69) msg_seq=3 ttl=64 rtt = 8.242489 ms.
^Ctime elapsed = 7.9805
64 bytes from 2 (h: (null)) (151.101.65.69) msg_seq=4 ttl=64 rtt = 7.980547 ms.
===151.101.65.69 ping statistics===
4 packets sent, 4 packets received, 0.000000 percent packet loss. Total time: 3494.951433 ms.
socket closed.
Terminated : Without Error.
您没有正确解码错误代码。
h_errno的值与errno对应的值不对应，所以无法使用strerror获取错误文本。
有一个名为 hstrerror 的函数，其功能与 strerror 相同，但用于 gethostbyname 和其他相关函数返回的错误代码。
手册页中列出的错误代码如下：
HOST_NOT_FOUND
The specified host is unknown.
NO_ADDRESS or NO_DATA
The requested name is valid but does not have an IP address.
NO_RECOVERY
A nonrecoverable name server error occurred.
TRY_AGAIN
A temporary error occurred on an authoritative name server. Try
again later.
“不允许操作”代码是 EPERM，在我的系统上是 1。该代码在我的系统上对应于 HOST_NOT_FOUND，所以假设您的错误代码与实际的相同您看到的错误。