socket获取客户端mac地址

在Socket编程中，获取客户端MAC地址需要使用操作系统提供的相关API。以下是在Linux和Windows平台中获取客户端MAC地址的方法。

在Linux平台中，可以通过获取客户端IP地址，然后通过ARP协议查询对应的MAC地址。具体实现步骤如下：

1. 使用getpeername函数获取客户端的IP地址
2. 使用ioctl函数发送SIOCGARP命令，查询对应IP地址的MAC地址
3. 解析返回的ARP缓存表项，获取MAC地址

以下是示例代码：

#include <sys/socket.h>
#include <arpa/inet.h>
#include <net/if.h>
#include <netinet/in.h>
#include <netdb.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <sys/ioctl.h>
#include <net/if_arp.h>

int get_client_mac(int sockfd, unsigned char *mac) {
    struct sockaddr_in cli_addr;
    socklen_t cli_len = sizeof(cli_addr);
    char ip_str[INET_ADDRSTRLEN];
    char mac_str[18];

    // 获取客户端IP地址
    if (getpeername(sockfd, (struct sockaddr *)&cli_addr, &cli_len) == -1) {
        perror("getpeername() failed");
        return -1;
    }
    inet_ntop(AF_INET, &cli_addr.sin_addr, ip_str, INET_ADDRSTRLEN);

    // 查询ARP缓存表项，获取MAC地址
    struct arpreq areq;
    memset(&areq, 0, sizeof(areq));
    struct sockaddr_in *sin = (struct sockaddr_in *)&areq.arp_pa;
    sin->sin_family = AF_INET;
    sin->sin_addr.s_addr = cli_addr.sin_addr.s_addr;

    int fd = socket(AF_INET, SOCK_DGRAM, 0);
    if (fd == -1) {
        perror("socket() failed");
        return -1;
    }
    if (ioctl(fd, SIOCGARP, &areq) == -1) {
        close(fd);
        perror("ioctl(SIOCGARP) failed");
        return -1;
    }
    close(fd);

    // 解析MAC地址
    unsigned char *ptr = (unsigned char *)&areq.arp_ha.sa_data[0];
    snprintf(mac_str, sizeof(mac_str), "%02X:%02X:%02X:%02X:%02X:%02X", ptr[0], ptr[1], ptr[2], ptr[3], ptr[4], ptr[5]);
    sscanf(mac_str, "%hhx:%hhx:%hhx:%hhx:%hhx:%hhx", &mac[0], &mac[1], &mac[2], &mac[3], &mac[4], &mac[5]);

    return 0;
}

在Windows平台中，可以使用GetAdaptersAddresses函数获取本地网卡信息，然后通过比对客户端IP地址和本地网卡的IP地址，获取对应的MAC地址。以下是示例代码：

#include <winsock2.h>
#include <iphlpapi.h>
#include <stdio.h>

#pragma comment(lib, "iphlpapi.lib")
#pragma comment(lib, "ws2_32.lib")

int get_client_mac(SOCKET sockfd, unsigned char *mac) {
    struct sockaddr_in cli_addr;
    int cli_len = sizeof(cli_addr);
    char ip_str[INET_ADDRSTRLEN];
    char mac_str[18];

    // 获取客户端IP地址
    if (getpeername(sockfd, (struct sockaddr *)&cli_addr, &cli_len) == -1) {
        perror("getpeername() failed");
        return -1;
    }
    inet_ntop(AF_INET, &cli_addr.sin_addr, ip_str, INET_ADDRSTRLEN);

    // 获取本地网卡信息
    ULONG size = 0;
    PIP_ADAPTER_ADDRESSES pAddresses = NULL;
    DWORD dwRetVal = GetAdaptersAddresses(AF_INET, GAA_FLAG_INCLUDE_PREFIX, NULL, pAddresses, &size);
    if (dwRetVal == ERROR_BUFFER_OVERFLOW) {
        pAddresses = (IP_ADAPTER_ADDRESSES *)malloc(size);
        dwRetVal = GetAdaptersAddresses(AF_INET, GAA_FLAG_INCLUDE_PREFIX, NULL, pAddresses, &size);
    }
    if (dwRetVal != NO_ERROR) {
        perror("GetAdaptersAddresses() failed");
        return -1;
    }

    // 比对IP地址，获取对应的MAC地址
    PIP_ADAPTER_ADDRESSES pCurrAddresses = pAddresses;
    while (pCurrAddresses) {
        if (pCurrAddresses->FirstUnicastAddress) {
            for (PIP_ADAPTER_UNICAST_ADDRESS pUnicast = pCurrAddresses->FirstUnicastAddress; pUnicast; pUnicast = pUnicast->Next) {
                struct sockaddr_in *sin = (struct sockaddr_in *)pUnicast->Address.lpSockaddr;
                if (strcmp(ip_str, inet_ntoa(sin->sin_addr)) == 0) {
                    snprintf(mac_str, sizeof(mac_str), "%02X:%02X:%02X:%02X:%02X:%02X", pCurrAddresses->PhysicalAddress[0], pCurrAddresses->PhysicalAddress[1], pCurrAddresses->PhysicalAddress[2], pCurrAddresses->PhysicalAddress[3], pCurrAddresses->PhysicalAddress[4], pCurrAddresses->PhysicalAddress[5]);
                    sscanf(mac_str, "%hhx:%hhx:%hhx:%hhx:%hhx:%hhx", &mac[0], &mac[1], &mac[2], &mac[3], &mac[4], &mac[5]);
                    free(pAddresses);
                    return 0;
                }
            }
        }
        pCurrAddresses = pCurrAddresses->Next;
    }

    free(pAddresses);
    return -1;
}