在 Windows C/C++ 之中一共有三种方法可以设置网卡的MTU大小。

方法一：

SetIpInterfaceEntry 法

            static bool SetInterfaceMtu2(int interface_index, int mtu) noexcept{PIP_ADAPTER_ADDRESSES pAddresses = NULL;ULONG ulBufLen = 0;GetAdaptersAddresses(AF_UNSPEC, 0, NULL, pAddresses, &ulBufLen);char* szBuf = (char*)Malloc(ulBufLen);pAddresses = (IP_ADAPTER_ADDRESSES*)szBuf;if (NULL == pAddresses){return false;}NETIOAPI_API dwErr = GetAdaptersAddresses(AF_INET, GAA_FLAG_SKIP_ANYCAST, NULL, pAddresses, &ulBufLen);if (dwErr == NO_ERROR){while (NULL != pAddresses){if (pAddresses->IfIndex == interface_index) {MIB_IPINTERFACE_ROW ifRow;InitializeIpInterfaceEntry(&ifRow);//interested nameifRow.InterfaceLuid = pAddresses->Luid;ifRow.Family = AF_INET;ifRow.NlMtu = mtu;dwErr = SetIpInterfaceEntry(&ifRow);break;}pAddresses = pAddresses->Next;}}Mfree(szBuf);return dwErr == NO_ERROR;}

方法二：

SetIfEntry 法

            std::shared_ptr<MIB_IFROW> GetIfEntry(int interface_index) noexcept{if (interface_index < 0){return NULL;}std::shared_ptr<MIB_IFROW> pIfRow = std::shared_ptr<MIB_IFROW>((MIB_IFROW*)Malloc(sizeof(MIB_IFROW)),[](MIB_IFROW* p) noexcept{Mfree(p);});if (NULL == pIfRow){return NULL;}pIfRow->dwIndex = interface_index;if (::GetIfEntry(pIfRow.get()) != NO_ERROR){return NULL;}return pIfRow;}int GetInterfaceMtu(int interface_index) noexcept{std::shared_ptr<MIB_IFROW> ifRow = GetIfEntry(interface_index);if (NULL == ifRow){return -1;}else{return ifRow->dwMtu;}}bool SetInterfaceMtu(int interface_index, int mtu) noexcept{// https://learn.microsoft.com/en-us/windows/win32/api/netioapi/nf-netioapi-getifentry2// https://learn.microsoft.com/en-us/windows/win32/api/iphlpapi/nf-iphlpapi-getifentrystd::shared_ptr<MIB_IFROW> ifRow = GetIfEntry(interface_index);if (NULL == ifRow){return false;}if (ifRow->dwMtu == mtu){return true;}else{ifRow->dwMtu = mtu;}DWORD dwErr = SetIfEntry(ifRow.get());if (dwErr == NO_ERROR){if (GetInterfaceMtu(interface_index) == mtu){return true;}}return SetInterfaceMtu2(interface_index, mtu);}

方法三：

命令行法

查看网络接口设置（MTU列项）

netsh interface ipv4 show subinterfaces

通过网络接口索引来管理，MTU是大小，10为网络接口索引

 netsh interface ipv4 set subinterface 10 mtu=1400 store=persistent

通过网络接口名字来管理，MTU是大小，eth0为网络接口名

netsh interface ipv4 set subinterface eth0 mtu=1400 store=persistent