Windows 系统下怎么获取 UDP 本机地址

2023-06-28
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我们知道 UDP 获取远端地址非常简单，通常接口 recvfrom 就可以直接获取到远端的地址和端口；如果获取 UDP 的本机地址就需要点特殊处理了，特别是本机有多网卡的情况下，我们想知道是那个 IP 接收的 UDP 包。对于 linux 我们知道，现在有了对应的解决方法，就是利用套接字选项 IP_PKTINFO 和 recvmsg 接口，就能轻松完成这个动作。

const int on = 1;// 开启获取包信息 , 结果存放在辅助数据当中setsockopt(sock,IPPROTO_IP,IP_PKTINFO,&on,sizeof(on));...// 接收数据包if ((retvalue=recvmsg(sock,&msg,0)) < 0){    break;}//开始获取辅助数据,由于辅助数据可以是一个也可以是一个数组,因此循环;for ( pcmsg = CMSG_FIRSTHDR(&msg) ; pcmsg != NULL ; pcmsg = CMSG_NXTHDR(&msg,pcmsg) ) {    //判断是否是包信息    if ( pcmsg->cmsg_level == IPPROTO_IP &&        pcmsg->cmsg_type == IP_PKTINFO ) {        //获取我们的自定义数据 struct in_pktinfo ;        unsigned char * pData = CMSG_DATA(pcmsg);        struct in_pktinfo * pInfo = (struct in_pktinfo *)pData;        //转换        inet_ntop(AF_INET,&pInfo->ipi_addr,dst_ip_buf,sizeof(dst_ip_buf));        inet_ntop(AF_INET,&pInfo->ipi_spec_dst,route_ip_buf,sizeof(route_ip_buf));        //下面都是打印信息        printf("client_addr:%s,port:%d\n",inet_ntoa(cli_addr.sin_addr), ntohs(cli_addr.sin_port));        printf("route ip :%s, dst ip:%s , ifindex:%d\n" , route_ip_buf,dst_ip_buf, pInfo->ipi_ifindex);        recvbuf[retvalue] = 0;        printf("recv bytes:%d , recvbuf:%s \n", retvalue, recvbuf);    }}

复制代码

Windows 系统下该怎么处理？

其实 Windows 系统下也是类似的操作，套接字选项也是需要开启 IP_PKTINFO 选项，但接收函数 recvmsg 是 linux 系统的函数，windows 系统的对应函数是 WSARecvMsg，利用此接口，我们也能轻松实现获取 UDP 包本机地址的需求

啥都没代码有说服力（代码有点烂，凑合看吧）

#include <stdio.h>#include <WinSock2.h>#include <mswsock.h>#include <ws2ipdef.h>#include <WS2tcpip.h>
#pragma comment(lib, "ws2_32.lib")
typedef unsigned char uint8_t;LPFN_WSARECVMSG WSARecvMsg = nullptr;
void get_wsarecvmsg_fptr(void){    DWORD dwBytesRecvd = 0;    GUID guidWSARecvMsg = WSAID_WSARECVMSG;    SOCKET sock = socket(AF_INET, SOCK_STREAM, 0);    WSAIoctl(sock, SIO_GET_EXTENSION_FUNCTION_POINTER,        &guidWSARecvMsg, sizeof(guidWSARecvMsg),        &WSARecvMsg, sizeof(WSARecvMsg),        &dwBytesRecvd, NULL, NULL);    closesocket(sock);}
int recv_localaddr(SOCKET s, uint8_t* buf, size_t buf_sz,    struct sockaddr_in* remote_addr,    struct sockaddr_in* local_addr){    DWORD bytes_received;    WSAMSG msg = { 0 };    WSABUF sbuf = { 0 };    uint8_t cmdbuf[512];    WSACMSGHDR* cmsg;    PIN_PKTINFO pi;
    sbuf.buf = (char FAR*)buf;    sbuf.len = (u_long)buf_sz;    msg.lpBuffers = &sbuf;    msg.dwBufferCount = 1;    msg.name = (LPSOCKADDR)remote_addr;    msg.namelen = sizeof(*remote_addr);    msg.Control.buf = (char FAR*)cmdbuf;    msg.Control.len = (u_long)sizeof(cmdbuf);
    /* Receive a packet */    (WSARecvMsg)(s, &msg, &bytes_received, NULL, NULL);
    /* Parse the header info, look for the local address */    cmsg = WSA_CMSG_FIRSTHDR(&msg);    for ( ; cmsg != NULL; cmsg = WSA_CMSG_NXTHDR(&msg, cmsg) ) {        if ((cmsg->cmsg_level == IPPROTO_IP) &&            (cmsg->cmsg_type == IP_PKTINFO)) {            char ipbuf[128] = { 0 };            size_t iplen = 128;            pi = (PIN_PKTINFO)WSA_CMSG_DATA(cmsg);            local_addr->sin_family = AF_INET;            local_addr->sin_addr = pi->ipi_addr;            printf("local ip: %s, local port: %d\n",                 inet_ntop(AF_INET, &(local_addr->sin_addr), ipbuf, iplen), ntohs(local_addr->sin_port));            printf("recv msg: %s", buf);            break;        }    }
    return (int)bytes_received;}
int main(int argc, char* argv[]){    WSADATA wsaData = {};    if ( WSAStartup(MAKEWORD(2, 1), &wsaData) == -1 ) {        return -1;    }    get_wsarecvmsg_fptr();
    SOCKET sock = socket(AF_INET, SOCK_DGRAM, 0);    struct sockaddr_in serv_addr, cli_addr;    memset(&serv_addr, 0, sizeof(serv_addr));    memset(&cli_addr, 0, sizeof(cli_addr));    serv_addr.sin_family = AF_INET;    serv_addr.sin_port = htons(8090);    serv_addr.sin_addr.s_addr = 0;    if (bind(sock, (sockaddr*)&serv_addr, sizeof(serv_addr)) < 0) {        closesocket(sock);        WSACleanup();        return -1;    }
    int sockopt = 1;    setsockopt(sock, IPPROTO_IP, IP_PKTINFO, (char*)&sockopt, sizeof(sockopt));
    size_t length = 2048;    char buffer[2048] = { 0 };    recv_localaddr(sock, (uint8_t*)buffer, length, &cli_addr, &serv_addr);    closesocket(sock);    WSACleanup();    return 0;}