Linux下通过ioctl系统调用来获取和设置网络信息

#include <stdio.h> 
#include <stdlib.h> 
#include <string.h> 
#include <unistd.h> 
#include <sys/ioctl.h> 
#include <net/if.h> 
#include <arpa/inet.h> 
#include <linux/netlink.h> 
#include <linux/rtnetlink.h> 
 
// 获取IP地址，子网掩码，MAC地址 
int GetLocalNetInfo( 
    const char* lpszEth, 
    char* szIpAddr, 
    char* szNetmask, 
    char* szMacAddr 
) 
{ 
    int ret = 0; 
 
    struct ifreq req; 
    struct sockaddr_in* host = NULL; 
 
    int sockfd = socket(AF_INET, SOCK_DGRAM, 0); 
    if ( -1 == sockfd ) 
    { 
        return -1; 
    } 
 
    bzero(&req, sizeof(struct ifreq)); 
    strcpy(req.ifr_name, lpszEth); 
    if ( ioctl(sockfd, SIOCGIFADDR, &req) >= 0 ) 
    { 
        host = (struct sockaddr_in*)&req.ifr_addr; 
        strcpy(szIpAddr, inet_ntoa(host->sin_addr)); 
    } 
    else 
    { 
        ret = -1; 
    } 
 
    bzero(&req, sizeof(struct ifreq)); 
    strcpy(req.ifr_name, lpszEth); 
    if ( ioctl(sockfd, SIOCGIFNETMASK, &req) >= 0 ) 
    { 
        host = (struct sockaddr_in*)&req.ifr_addr; 
        strcpy(szNetmask, inet_ntoa(host->sin_addr)); 
    } 
    else 
    { 
        ret = -1; 
    } 
 
    bzero(&req, sizeof(struct ifreq)); 
    strcpy(req.ifr_name, lpszEth); 
    if ( ioctl(sockfd, SIOCGIFHWADDR, &req) >= 0 ) 
    { 
        sprintf( 
            szMacAddr, "%02x:%02x:%02x:%02x:%02x:%02x", 
            (unsigned char)req.ifr_hwaddr.sa_data[0], 
            (unsigned char)req.ifr_hwaddr.sa_data[1], 
            (unsigned char)req.ifr_hwaddr.sa_data[2], 
            (unsigned char)req.ifr_hwaddr.sa_data[3], 
            (unsigned char)req.ifr_hwaddr.sa_data[4], 
            (unsigned char)req.ifr_hwaddr.sa_data[5] 
        ); 
    } 
    else 
    { 
        ret = -1; 
    } 
 
    if ( sockfd != -1 ) 
    { 
        close(sockfd); 
        sockfd = -1; 
    } 
 
    return ret; 
} 
 
// ------------------------------------------------------ 
 
#define BUFSIZE 8192 
 
struct route_info  
{ 
    char ifName[IF_NAMESIZE]; 
    u_int gateWay; 
    u_int srcAddr; 
    u_int dstAddr; 
}; 
 
static int ReadNlSock( 
    int sockFd, 
    char* bufPtr, 
    int seqNum, 
    int pId 
) 
{ 
    struct nlmsghdr* nlHdr = NULL; 
    int readLen = 0, msgLen = 0; 
 
    while (true) 
    { 
        if ( (readLen = recv(sockFd, bufPtr, BUFSIZE - msgLen, 0)) < 0 ) 
        { 
            return -1; 
        } 
 
        nlHdr = (struct nlmsghdr *)bufPtr; 
 
        if ( (NLMSG_OK(nlHdr, (unsigned int)readLen) == 0) 
                || (nlHdr->nlmsg_type == NLMSG_ERROR) ) 
        { 
            return -1; 
        } 
 
        if ( nlHdr->nlmsg_type == NLMSG_DONE ) 
        { 
            break; 
        } 
        else 
        { 
            bufPtr += readLen; 
            msgLen += readLen; 
        } 
 
        if ( (nlHdr->nlmsg_flags & NLM_F_MULTI) == 0 ) 
        { 
            break; 
        } 
 
        if ( (nlHdr->nlmsg_seq != (unsigned int)seqNum) 
                || (nlHdr->nlmsg_pid != (unsigned int)pId) ) 
        { 
            break; 
        } 
    } 
 
    return msgLen; 
} 
 
static int ParseRoutes( 
    struct nlmsghdr* nlHdr, 
    struct route_info* rtInfo, 
    char* default_gateway 
) 
{ 
    int rtLen = 0; 
    struct in_addr dst; 
    struct in_addr gate; 
    struct rtmsg* rtMsg = NULL; 
    struct rtattr* rtAttr = NULL; 
 
    rtMsg = (struct rtmsg*)NLMSG_DATA(nlHdr); 
 
    if ( (rtMsg->rtm_family != AF_INET) 
            || (rtMsg->rtm_table != RT_TABLE_MAIN) ) 
    { 
        return -1; 
    } 
 
    rtAttr = (struct rtattr*)RTM_RTA(rtMsg); 
    rtLen = RTM_PAYLOAD(nlHdr); 
    for ( ; RTA_OK(rtAttr, rtLen); rtAttr = RTA_NEXT(rtAttr, rtLen) ) 
    { 
        switch (rtAttr->rta_type) 
        { 
        case RTA_OIF: 
            if_indextoname(*(int*)RTA_DATA(rtAttr), rtInfo->ifName); 
            break; 
        case RTA_GATEWAY: 
            rtInfo->gateWay = *(u_int*)RTA_DATA(rtAttr); 
            break; 
        case RTA_PREFSRC: 
            rtInfo->srcAddr = *(u_int*)RTA_DATA(rtAttr); 
            break; 
        case RTA_DST: 
            rtInfo->dstAddr = *(u_int*)RTA_DATA(rtAttr); 
            break; 
        } 
    } 
 
    dst.s_addr = rtInfo->dstAddr; 
    if (strstr((char*)inet_ntoa(dst), "0.0.0.0")) 
    { 
        gate.s_addr = rtInfo->gateWay; 
        strcpy(default_gateway, (char*)inet_ntoa(gate)); 
    } 
 
    return 0; 
} 
 
// 获取默认网关 
int GetDefaultGateway( 
    const char* lpszEth, 
    char* szDefaultGateway 
) 
{ 
    static char szGatewayTemp[32] = {0}; 
    static char msgBuf[BUFSIZE] = {0}; 
    static struct route_info ri; 
 
    int ret = -1; 
 
    struct nlmsghdr* nlMsg = NULL; 
    struct rtmsg* rtMsg = NULL; 
    struct route_info* rtInfo = &ri; 
 
    int len = 0, msgSeq = 0; 
 
    int sock = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_ROUTE); 
    if ( -1 == sock ) 
    { 
        goto END; 
    } 
 
    nlMsg = (struct nlmsghdr*)msgBuf; 
    rtMsg = (struct rtmsg*)NLMSG_DATA(nlMsg); 
 
    nlMsg->nlmsg_len = NLMSG_LENGTH(sizeof(struct rtmsg)); 
    nlMsg->nlmsg_type = RTM_GETROUTE; 
    nlMsg->nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST; 
    nlMsg->nlmsg_seq = msgSeq++; 
    nlMsg->nlmsg_pid = getpid(); 
 
    if ( send(sock, nlMsg, nlMsg->nlmsg_len, 0) < 0 ) 
    { 
        goto END; 
    } 
 
    if ( (len = ReadNlSock(sock, msgBuf, msgSeq, getpid())) < 0 ) 
    { 
        goto END; 
    } 
 
    if ( rtInfo != NULL ) 
    { 
        for ( ; NLMSG_OK(nlMsg, (unsigned int)len); nlMsg = NLMSG_NEXT(nlMsg, len) ) 
        { 
            memset(szGatewayTemp, 0, 64); 
            memset(rtInfo, 0, sizeof(struct route_info)); 
            if ( 0 == ParseRoutes(nlMsg, rtInfo, szGatewayTemp) ) 
            { 
                if ( strcmp(rtInfo->ifName, lpszEth) == 0 
                        && strcmp(szGatewayTemp, "0.0.0.0") != 0 
                        && strlen(szGatewayTemp) > 0 ) 
                { 
                    strcpy(szDefaultGateway, szGatewayTemp); 
                    ret = 0; 
                }  
            } 
        } 
    } 
 
END: 
 
    if ( sock != -1 ) 
    { 
        close(sock); 
        sock = -1; 
    } 
 
    return ret; 
} 
 
// ------------------------------------------------------ 
 
// 设置IP地址和子网掩码 
int SetLocalNetInfo( 
    const char* lpszEth, 
    const char* lpszIpAddr, 
    const char* lpszNetmask 
) 
{ 
    int ret = -1; 
 
    struct ifreq req; 
    struct sockaddr_in* host = NULL; 
 
    int sockfd = socket(AF_INET, SOCK_DGRAM, 0); 
    if ( -1 == sockfd ) 
    { 
        goto END; 
    } 
 
    bzero(&req, sizeof(struct ifreq)); 
    strcpy(req.ifr_name, lpszEth); 
    host = (struct sockaddr_in*)&req.ifr_addr; 
    host->sin_family = AF_INET; 
    if ( 1 != inet_pton(AF_INET, lpszIpAddr, &(host->sin_addr)) ) 
    { 
        goto END; 
    } 
    if ( ioctl(sockfd, SIOCSIFADDR, &req) < 0 ) 
    { 
        goto END; 
    } 
 
    bzero(&req, sizeof(struct ifreq)); 
    strcpy(req.ifr_name, lpszEth); 
    host = (struct sockaddr_in*)&req.ifr_addr; 
    host->sin_family = AF_INET; 
    if ( 1 != inet_pton(AF_INET, lpszNetmask, &(host->sin_addr)) ) 
    { 
        goto END; 
    } 
    if ( ioctl(sockfd, SIOCSIFNETMASK, &req) < 0 ) 
    { 
        goto END; 
    } 
 
    ret = 0; 
 
END: 
 
    if ( sockfd != -1 ) 
    { 
        close(sockfd); 
        sockfd = -1; 
    } 
 
    return ret; 
} 
 
// 设置指定网口的mtu值 
int SetMTU(const char* lpszEth, unsigned int mtu) 
{ 
    int ret = -1; 
 
    struct ifreq ifr; 
 
    int sockfd = socket(AF_INET, SOCK_DGRAM, 0); 
    if ( -1 == sockfd ) 
    { 
        goto END; 
    } 
 
    strcpy(ifr.ifr_name, lpszEth); 
    ifr.ifr_ifru.ifru_mtu = mtu; 
    if ( ioctl(sockfd, SIOCSIFMTU, &ifr) < 0 ) 
    { 
        goto END; 
    } 
 
    ret = 0; 
 
END: 
 
    if ( sockfd != -1 ) 
    { 
        close(sockfd); 
        sockfd = -1; 
    } 
 
    return ret; 
} 
 
// 关闭指定网口 
int SetIfDown(const char* lpszEth) 
{ 
    int ret = -1; 
 
    struct ifreq ifr; 
 
    int sockfd = socket(AF_INET, SOCK_DGRAM, 0); 
    if ( -1 == sockfd ) 
    { 
        goto END; 
    } 
 
    strcpy(ifr.ifr_name, lpszEth); 
 
    if ( ioctl(sockfd, SIOCGIFFLAGS, &ifr) < 0 ) 
    { 
        goto END; 
    } 
 
    ifr.ifr_flags &= ~IFF_UP; 
 
    if ( ioctl(sockfd, SIOCSIFFLAGS, &ifr) < 0 ) 
    { 
        goto END; 
    } 
 
    ret = 0; 
 
END: 
 
    if ( sockfd != -1 ) 
    { 
        close(sockfd); 
        sockfd = -1; 
    } 
 
    return ret; 
} 
 
// 打开指定网口 
int SetIfUp(const char* lpszEth) 
{ 
    int ret = -1; 
 
    struct ifreq ifr; 
 
    int sockfd = socket(AF_INET, SOCK_DGRAM, 0); 
    if ( -1 == sockfd ) 
    { 
        goto END; 
    } 
 
    strcpy(ifr.ifr_name, lpszEth); 
 
    if ( ioctl(sockfd, SIOCGIFFLAGS, &ifr) < 0 ) 
    { 
        goto END; 
    } 
 
    ifr.ifr_flags |= IFF_UP; 
 
    if ( ioctl(sockfd, SIOCSIFFLAGS, &ifr) < 0 ) 
    { 
        goto END; 
    } 
 
    ret = 0; 
 
END: 
 
    if ( sockfd != -1 ) 
    { 
        close(sockfd); 
        sockfd = -1; 
    } 
 
    return ret; 
} 
 
小记：前端时间因为需要在Linux下获取和设置网络信息，所以就简单的学习了一下，写出了以上的几个工具函数。最开始是用了一种比较土的方式，就是通过system函数执行命令，然后命令是通过调用ifconfig这个程序来到达设置网络信息的目的，但是感觉很别扭，还是应该使用相应的API比较好，但是又没有找到Linux有对应的API，上网查也似乎没能找到什么比较好的现成函数，所以最后只好自己写了