Linux 上利用 getifaddrs 函数枚举，获取理论上可用物理网卡设备

 本文所示代码可以在 __ANDROID_API__ >= 24 上编译或者在 Linux 上面。

            bool Network::GetLocalExitInterface(std::string& interface_, UInt32& address, UInt32& gw, UInt32& mask) {
                bool b = false;
                #if (!defined(ANDROID) || __ANDROID_API__ >= 24)
                struct ifaddrs* ifList = NULL;
                if (getifaddrs(&ifList) < 0) {
                    return b;
                }
                UInt32 invalidIPAddr = inet_addr("169.254.0.0");
                UInt32 invalidIPMask = inet_addr("255.255.0.0");
                for (struct ifaddrs* ifa = ifList; ifa != NULL; ifa = ifa->ifa_next) {
                    struct sockaddr_in* sin = (struct sockaddr_in*)ifa->ifa_addr; // ifa_dstaddr
                    if (NULL == sin || sin->sin_family != AF_INET) {
                        continue;
                    }
                    UInt32 ipAddr = sin->sin_addr.s_addr;
                    if ((ipAddr & invalidIPMask) == invalidIPAddr) {
                        continue;
                    }
                    ipAddr = ntohl(ipAddr);
                    if (ipAddr != INADDR_ANY && ipAddr != INADDR_NONE && ipAddr != INADDR_LOOPBACK) {
                        sin = (struct sockaddr_in*)ifa->ifa_netmask;
                        if (NULL == sin|| sin->sin_family != AF_INET) {
                            continue;
                        }
                        b = true;
                        interface_ = ifa->ifa_name;
                        address = htonl(ipAddr);
                        mask = sin->sin_addr.s_addr;
                        if (mask == UINT_MAX) {
                            gw = address;
                        }
                        else {
                            gw = htonl(ntohl(mask & address) + 1);
                        }
                        break;
                    }
                }
                freeifaddrs(ifList);
                #endif
                return b;
            }