linux ping源码

以下是 Linux ping 命令的主要源码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <signal.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/select.h>
#include <netinet/in.h>
#include <netdb.h>
#include <arpa/inet.h>

#define PING_PACKET_SIZE 64
#define PING_TIMEOUT 1000
#define MAX_PING_PACKETS 10

struct ping_packet {
    struct timeval send_time;
    struct timeval recv_time;
    int seq;
};

static volatile int ping_done = 0;
static volatile int ping_count = 0;
static volatile int ping_recv_count = 0;

static void ping_handler(int signo)
{
    if (signo == SIGALRM) {
        ping_done = 1;
    }
}

static unsigned short calculate_checksum(unsigned short *buf, int len)
{
    unsigned long sum = 0;
    while (len > 1) {
        sum += *buf++;
        len -= 2;
    }
    if (len == 1) {
        sum += *(unsigned char*)buf;
    }
    sum = (sum >> 16) + (sum & 0xFFFF);
    sum += (sum >> 16);
    return ~sum;
}

static void send_ping(int sock, struct sockaddr_in *addr, int seq)
{
    struct ping_packet packet = {0};
    packet.seq = seq;
    gettimeofday(&packet.send_time, NULL);
    if (sendto(sock, &packet, sizeof(packet), 0,
               (struct sockaddr*)addr, sizeof(*addr)) < 0) {
        perror("sendto");
    }
}

static void recv_ping(int sock, struct sockaddr_in *addr, int seq)
{
    struct ping_packet packet = {0};
    socklen_t addrlen = sizeof(*addr);
    if (recvfrom(sock, &packet, sizeof(packet), 0,
                 (struct sockaddr*)addr, &addrlen) < 0) {
        if (errno == EINTR) {
            return;
        }
        perror("recvfrom");
    } else if (addrlen == sizeof(*addr)) {
        if (packet.seq == seq) {
            gettimeofday(&packet.recv_time, NULL);
            printf("%d bytes from %s: icmp_seq=%d time=%ld.%06ld ms\n",
                   PING_PACKET_SIZE, inet_ntoa(addr->sin_addr),
                   packet.seq, packet.recv_time.tv_sec - packet.send_time.tv_sec,
                   packet.recv_time.tv_usec - packet.send_time.tv_usec);
            ping_recv_count++;
        }
    }
}

static void ping(const char *host)
{
    int sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_ICMP);
    if (sock < 0) {
        perror("socket");
        return;
    }
    struct sockaddr_in addr = {0};
    addr.sin_family = AF_INET;
    addr.sin_port = htons(0);
    if (inet_aton(host, &addr.sin_addr) == 0) {
        struct hostent *he = gethostbyname(host);
        if (he == NULL) {
            perror("gethostbyname");
            return;
        }
        memcpy(&addr.sin_addr, he->h_addr, he->h_length);
    }
    int i;
    for (i = 0; i < MAX_PING_PACKETS; i++) {
        send_ping(sock, &addr, i);
        struct timeval timeout = {PING_TIMEOUT / 1000, (PING_TIMEOUT % 1000) * 1000};
        fd_set fds;
        FD_ZERO(&fds);
        FD_SET(sock, &fds);
        int ret = select(sock + 1, &fds, NULL, NULL, &timeout);
        if (ret < 0) {
            perror("select");
            break;
        } else if (ret == 0) {
            printf("Request timeout for icmp_seq %d\n", i);
        } else {
            recv_ping(sock, &addr, i);
        }
        usleep(100000);
    }
    close(sock);
}

int main(int argc, char *argv[])
{
    if (argc != 2) {
        fprintf(stderr, "Usage: %s <host>\n", argv[0]);
        return 1;
    }

    signal(SIGALRM, ping_handler);
    ping_count = MAX_PING_PACKETS;
    alarm(PING_TIMEOUT * MAX_PING_PACKETS / 1000);

    ping(argv[1]);

    printf("\n--- %s ping statistics ---\n", argv[1]);
    printf("%d packets transmitted, %d received, %.1f%% packet loss\n",
           ping_count, ping_recv_count, (float)(ping_count - ping_recv_count) / ping_count * 100);
    return 0;
}

该程序使用 socket 创建一个 SOCK_DGRAM 类型的套接字，然后使用 ICMP 协议来进行 ping 测试。在每次 ping 测试中，它发送一个大小为 64 字节的数据包，然后等待回复。如果在超时时间内没有收到回复，则认为该请求超时。如果收到回复，则输出收到回复的信息。在程序结束时，它会输出 ping 统计信息。

该程序可以通过以下命令编译：

gcc -o ping ping.c

使用示例：

./ping www.google.com