c#怎么通过iphlpapi.dll 这个api操作路由表

2025-04-14 05:50:21
推荐回答(1个)
回答1:

最简单的方式是在C#里调用cmd的route命令,优点是简单,开发速度快。缺点显而易见,运行效率非常低,添加一条记录可能需要200ms以上。如果添加记录极多的话,这个效率就让人难以接受了。

这里我就讲一下第二种用法,通过调用win api来修改路由表,达到高效率添加的目的。这个问题看似很简单。实际操作起来却遇到很多麻烦。一些细节的描述在网上很少有人提及。

核心函数是:

[DllImport("Iphlpapi.dll")]

[return: MarshalAs(UnmanagedType.U4)]

public static extern int CreateIpForwardEntry(ref MIB_IPFORWARDROW pRoute);

CreateIpForwardEntry 这个函数,入口参数是一个结构,如下所示

[StructLayout(LayoutKind.Sequential)]

public struct MIB_IPFORWARDROW

{

public UInt32 dwForwardDest; //destination IP address.

public UInt32 dwForwardMask; //Subnet mask

public UInt32 dwForwardPolicy; //conditions for multi-path route. Unused, specify 0.

public UInt32 dwForwardNextHop; //IP address of the next hop. Own address?

public UInt32 dwForwardIfIndex; //index of interface

public UInt32 dwForwardType; //route type

public UInt32 dwForwardProto; //routing protocol.

public UInt32 dwForwardAge; //age of route.

public UInt32 dwForwardNextHopAS; //autonomous system number. 0 if not relevant

public int dwForwardMetric1; //-1 if not used (goes for all metrics)

public int dwForwardMetric2;

public int dwForwardMetric3;

public int dwForwardMetric4;

public int dwForwardMetric5;

}

我们把上面这个api函数稍微改造一下,适合C#调用

public static int createIpForwardEntry(UInt32 destIPAddress, UInt32
destMask, UInt32 nextHopIPAddress, UInt32 ifIndex, int metric)

{

MIB_IPFORWARDROW mifr = new MIB_IPFORWARDROW();

mifr.dwForwardDest = destIPAddress;

mifr.dwForwardMask = destMask;

mifr.dwForwardNextHop = nextHopIPAddress;

mifr.dwForwardIfIndex = ifIndex;

mifr.dwForwardPolicy = Convert.ToUInt32(0);

mifr.dwForwardType = Convert.ToUInt32(4);

mifr.dwForwardProto = Convert.ToUInt32(3);

mifr.dwForwardAge = Convert.ToUInt32(0);

mifr.dwForwardNextHopAS = Convert.ToUInt32(0);

mifr.dwForwardMetric1 = metric;

mifr.dwForwardMetric2 = -1;

mifr.dwForwardMetric3 = -1;

mifr.dwForwardMetric4 = -1;

mifr.dwForwardMetric5 = -1;

return CreateIpForwardEntry(ref mifr);

}

其中 mifr.dwForwardDest 是ip地址,

mifr.dwForwardMask 是子网掩码。

mifr.dwForwardNextHop 是网关地址

以上三个参数比较好理解和使用,有一个注意点就是这三个参数都是32位无符号整形,我们平时使用的ip地址都是字符串形式的,比如"192.168.0.1",这就涉及到一个ip地址由string转换成uint32过程

ip地址4个字节,无符号32位整形正好能够保存ip的所有数据

//IP转换成数字地址

public static uint IPToInt(string ipAddress)

{

string disjunctiveStr = ".,:";

char[] delimiter = disjunctiveStr.ToCharArray();

string[] startIP = null;

for (int i = 1; i <= 5; i++)

{

startIP = ipAddress.Split(delimiter, i);

}

string a1 = startIP[0].ToString();

string a2 = startIP[1].ToString();

string a3 = startIP[2].ToString();

string a4 = startIP[3].ToString();

uint U1 = uint.Parse(a1);

uint U2 = uint.Parse(a2);

uint U3 = uint.Parse(a3);

uint U4 = uint.Parse(a4);

uint U = U4 << 24;

U += U3 << 16;

U += U2 << 8;

U += U1;

return U;

}

转换函数如上,需要注意的是msdn上明确指出,转换的ip地址,需要是低字节在前,就是说192.168.0.1这个ip地址,最后的0x01要放在uint的32位的前面8个字节上。

问题最大的就是 dwForwardIfIndex 和 dwForwardMetric1 这两个参数如何获得

方法如下:

uint forwardMetric = 0;

int pdwSize = 20000;

pIPForwardTable = new byte[pdwSize];

iphlpapi.GetIpForwardTable(pIPForwardTable, out pdwSize, true);

ForwardIfIndex = pIPForwardTable[20];

以上代码获得ForwardIfIndex 的值,这个值被存放在 pIPForwardTable 下标为20的地方 囧

可以参考
参考链接 这个非常隐蔽。

[DllImport("Iphlpapi.dll")]

public static extern uint GetIpInterfaceEntry(ref MIB_IPINTERFACE_ROW pRoute);

[DllImport("iphlpapi.dll", CharSet = CharSet.Auto)]

public static extern int GetBestInterface(UInt32 DestAddr, out UInt32 BestIfIndex);

iphlpapi.GetBestInterface(GetNetworkInfo.IPToInt(strIP), out interfaceIndex);

iphlpapi.MIB_IPINTERFACE_ROW aRow = new iphlpapi.MIB_IPINTERFACE_ROW();

aRow.Family = 2;

aRow.InterfaceLuid = 0;

aRow.InterfaceIndex = interfaceIndex;

//GetIpInterfaceEntry is available in Vista/2008 server or higher

uint errorCode = iphlpapi.GetIpInterfaceEntry(ref aRow);

if (errorCode != 0)

{

AppendRichTextBox("Can't get Metric number");

sr.Close();

return;

}

forwardMetric = aRow.Metric;

以上代码可以获得 forwardMetric 的值,这样,所有参数就都全了,最终调用:

if (iphlpapi.createIpForwardEntry(GetNetworkInfo.IPToInt(strIP),

GetNetworkInfo.IPToInt(SubnetMask),

GetNetworkInfo.IPToInt(defaultGateway), ForwardIfIndex, (int)forwardMetric + 5) != 0)

{

//添加错误

}

forwardMetric 最终要加上一个offset,不能比 aRow.Metric 小

要删除记录,那就比较简单了,把结构当中的 mifr.dwForwardMetric1 = -1 即可

public static int deleteIpForwardEntry(UInt32 destIPAddress, UInt32 destMask, UInt32 nextHopIPAddress, UInt32 ifIndex)

{

MIB_IPFORWARDROW mifr = new MIB_IPFORWARDROW();

mifr.dwForwardDest = destIPAddress;

mifr.dwForwardMask = destMask;

mifr.dwForwardNextHop = nextHopIPAddress;

mifr.dwForwardIfIndex = ifIndex;

mifr.dwForwardPolicy = Convert.ToUInt32(0);

mifr.dwForwardType = Convert.ToUInt32(4);

mifr.dwForwardProto = Convert.ToUInt32(3);

mifr.dwForwardAge = Convert.ToUInt32(0);

mifr.dwForwardNextHopAS = Convert.ToUInt32(0);

mifr.dwForwardMetric1 = -1;

mifr.dwForwardMetric2 = -1;

mifr.dwForwardMetric3 = -1;

mifr.dwForwardMetric4 = -1;

mifr.dwForwardMetric5 = -1;

return DeleteIpForwardEntry(ref mifr);

}

以上的做法虽然有点复杂,但是好处是显而易见的,运行效率非常高,运行createIpForwardEntry方法几百次仅仅需要不到1s的时间。