RAW ICMP 套接字:recvfrom(） 未接收任何数据

RAW ICMP socket: recvfrom() not recieving any data

本文关键字：任何 数据 ICMP 套接字 recvfrom RAW      更新时间：2023-10-16

以下代码是一个旨在发送 ICMP 回显请求和接收回复的程序。

/*
    Forgive my lack of error handling :)
*/
SOCKET ASOCKET = INVALID_SOCKET;
struct sockaddr saddr;
struct sockaddr_in *to = (struct sockaddr_in *) &saddr;
struct sockaddr_in from;
int fromsize = sizeof(from);
std::string ip = "[arbitrary ip address]";
struct ICMP {
    USHORT type;
    USHORT code;
    USHORT cksum;
    USHORT id;
    USHORT seq;
}*_ICMP;
char sendBuffer[sizeof(struct ICMP)];
char recvBuffer[256];
WSADATA wsaData;
WSAStartup(MAKEWORD(2, 2), &wsaData);
memset(&saddr, NULL, sizeof(saddr));
ASOCKET = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
//  Configure timeout
DWORD timeoutmilsec = 3000;
setsockopt(ASOCKET, SOL_SOCKET, SO_RCVTIMEO, (char *)&timeoutmilsec, sizeof(timeoutmilsec));
to->sin_family = AF_INET;
inet_pton(AF_INET, ip.c_str(), &(to->sin_addr));
_ICMP = new ICMP();
_ICMP->type = 8;
_ICMP->code = 0;
_ICMP->cksum = 0;
_ICMP->id = rand();
_ICMP->seq++;
// I have omitted my declaration of checksum() for simplicity
_ICMP->cksum = checksum((u_short *)_ICMP, sizeof(struct ICMP));
memcpy(sendBuffer, _ICMP, sizeof(struct ICMP));
if (sendto(ASOCKET, sendBuffer, sizeof(sendBuffer), NULL, (sockaddr *)&saddr, sizeof(saddr)) == SOCKET_ERROR)
{
    printf("sendto() failed with error: %un", WSAGetLastError());
    return false;
}
if (recvfrom(ASOCKET, recvBuffer, sizeof(recvBuffer), NULL, (sockaddr *)&from, &fromsize) == SOCKET_ERROR)
{
    if (WSAGetLastError() == TIMEOUTERROR)
    {
        printf("Timed outnn");
        return false;
    }
    printf("recvfrom() failed with error: %un", WSAGetLastError());
    return false;
}
我的

问题是我的recvfrom()调用没有收到任何数据并返回超时错误(10060(，尽管ping已被回复(Wireshark捕获请求并发送回复(。 sendto()有效，但recvfrom()行为奇怪，我无法弄清楚问题出在哪里。

我觉得有趣的是recvfrom()只有当网关告诉我主机无法访问时，它才会接收数据;如果主机可访问并且响应了ping，则不会接收数据。

问题出在struct ICMP .

ICMP的type和code应unsigned char。

ICMP 的标头应为 8 字节，但 struct ICMP 的大小为 10 字节。

所以应该改为：

struct ICMP {
    unsigned char type;
    unsigned char code;
    USHORT cksum;
    USHORT id;
    USHORT seq;
}*_ICMP;

事实证明，整个过程中都是我的防火墙阻止了响应。我的代码中唯一的错误是我的 ICMP 结构的大小(由 cshu 提到(。

感谢大家的帮助。

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