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, 32);
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。