CODEWITHSUNDEEP
cudprecvfrom
zawalida
zawalida

Reputation: 21

How can I recvive the ICMP packet (ICMP_PORT_UNREACH)?

I can find udp packet and ICMP packet in Wireshark, but recvfrom() return -1 when I use it to recvive ICMP packet in my program. I use GetLastError() and the error code is 10022.

send_sa.sin_family = AF_INET;
send_sa.sin_addr.s_addr = inet_addr(treeRoot);
SOCKET sockSend = socket(AF_INET, SOCK_DGRAM, 0);
……
send_sa.sin_port = htons(portCurr);


SOCKET sockRecv = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
……
//int res = sendto(sockSend, NULL, 0, 0, (struct sockaddr*)&send_sa, sizeof(send_sa));
    connect(sockSend, (struct sockaddr*)&send_sa, sizeof(send_sa));
    send(sockSend, NULL, 0, 0);
……
re = recvfrom(sockRecv, buff, sizeof(buff), 0, (struct sockaddr*)&send_sa, (socklen_t*)&structlen);

Upvotes: 0

Views: 102

Answers (1)

HP_perfect
HP_perfect

Reputation: 93

To read packets and detect ICMP messages for unreachable ports, you can use raw sockets.
When a UDP packet is sent to a closed port, the session layer will generate an ICMP "Port Unreachable" message back to the source.

Here’s an example code snippet that demonstrates how to capture these packets using a raw socket:

#include <iostream>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/if_ether.h>
#include <netinet/ip_icmp.h>
#include <netinet/udp.h>
#include <arpa/inet.h>
#include <cstring>

constexpr int SOCK_BUF_SIZE = 65536;
int sockFd_;
uint8_t buffer_[SOCK_BUF_SIZE];
const int ethHeaderSize_ = sizeof(struct ether_header);

int main() {
    struct sockaddr_ll sa;
    socklen_t sa_len = sizeof(sa);

    // Create a raw socket
    sockFd_ = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
    if (sockFd_ < 0) {
        std::cerr << "Socket creation error" << std::endl;
        exit(EXIT_FAILURE);
    }

    while (true) {
        ssize_t packet_len = recvfrom(sockFd_, buffer_, SOCK_BUF_SIZE, 0, reinterpret_cast<struct sockaddr *>(&sa), &sa_len);
        if (packet_len < 0) {
            std::cerr << "Error receiving packet" << std::endl;
            continue;
        }

        const auto* eth = reinterpret_cast<const ether_header *>(buffer_);
        if (ntohs(eth->ether_type) == ETHERTYPE_IP) {
            const auto* ipHeader = reinterpret_cast<const ip*>(buffer_ + ethHeaderSize_);
            if (ipHeader->ip_p == IPPROTO_ICMP) {
                const auto* icmpHeader = reinterpret_cast<const icmphdr*>(buffer_ + ethHeaderSize_ + ipHeader->ip_hl * 4);
                if (icmpHeader->type == ICMP_DEST_UNREACH && icmpHeader->code == ICMP_PORT_UNREACH) {
                    const auto* origIph = reinterpret_cast<const ip*>(buffer_ + ethHeaderSize_ + ipHeader->ip_hl * 4 + sizeof(struct icmphdr));
                    const auto* origUdph = reinterpret_cast<const udphdr*>(reinterpret_cast<const uint8_t*>(origIph) + origIph->ip_hl * 4);
                    std::cout << "Unreachable port in ICMP message: " << ntohs(origUdph->uh_dport) << std::endl;
                }
            }
        }
    }

    close(sockFd_);
    return 0;
}

Upvotes: 0

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