如何解决C++ 上的设备联网
我需要访问我设备上的网络接口。我有下面的代码可以做到这一点，但我缺少那些处于活动状态但没有与它们关联的 IP 地址的代码。关于如何以编程方式收集这些信息的任何想法？
发布的代码具有从接口获取信息的功能、列出所有接口的功能和用于测试的主要功能。
谢谢
struct iface {
std::string name;
std::string address;
std::string netmask;
std::string broadcast;
std::string hwaddr;
int mtu;
};
void print_iface(iface s) {
std::cout << s.name << ": <UP,RUNNING>" << std::endl;
std::cout << " mtu: " << s.mtu << std::endl;
std::cout << " hwaddr: " << s.hwaddr << " " << std::endl;
std::cout << " inet: " << s.address << " " << std::endl;
std::cout << " netmask: " << s.netmask << " " << std::endl;
std::cout << " broadcast: " << s.broadcast << std::endl;
}
std::tuple<char*,int> get_active_interfaces() {
int socketfd;
struct ifconf conf;
char data[4096];
socketfd = socket(AF_INET,SOCK_DGRAM,0);
conf.ifc_len = sizeof(data);
conf.ifc_buf = (caddr_t) data;
if (ioctl(socketfd,SIOCGIFCONF,&conf) < 0) {
fprintf(stderr,"ioctl error: %s",std::strerror(errno));
return std::make_tuple(nullptr,0);
} else {
return std::make_tuple(data,conf.ifc_len);
}
}
std::string get_ifname(struct ifreq *ifr) {
return ifr->ifr_name;
}
std::string get_ipv4_addr(struct ifreq *ifr) {
std::string addr(45,0);
inet_ntop(ifr->ifr_addr.sa_family,&((struct sockaddr_in*) &ifr->ifr_addr)->sin_addr,&addr[0],addr.size());
return addr;
}
#define MAC_TEMPLATE "%02X:%02X:%02X:%02X:%02X:%02X"
#define LOOPBACK_TEMPLATE "LOOPBAK INTERFACE"
std::string get_mac_addr(struct ifreq *ifr) {
std::string addr;
u_int8_t hd[6];
struct ifreq ifl;
int sock = socket(AF_INET,IPPROTO_IP);
if (sock >= 0) {
strcpy(ifl.ifr_name,ifr->ifr_name);
if (ioctl(sock,SIOCGIFFLAGS,&ifl) == 0) {
if (!(ifl.ifr_flags & IFF_LOOPBACK)) {
if (ioctl(sock,SIOCGIFHWADDR,&ifl) == 0) {
memcpy(hd,ifl.ifr_hwaddr.sa_data,sizeof(hd));
size_t n = snprintf(nullptr,MAC_TEMPLATE,hd[0],hd[1],hd[2],hd[3],hd[4],hd[5]);
addr.resize(n + 1,0);
sprintf(&addr[0],hd[5]);
}
} else {
addr = LOOPBACK_TEMPLATE;
}
}
}
return addr;
}
std::string get_netmask(struct ifreq *ifr) {
std::string addr(45,0);
struct ifreq ifl;
int sock = socket(AF_INET,SIOCGIFNETMASK,&ifl) == 0) {
inet_ntop(ifl.ifr_addr.sa_family,&((struct sockaddr_in*) &ifl.ifr_addr)->sin_addr,addr.size());
}
}
return addr;
}
std::string get_broadcast(struct ifreq *ifr) {
std::string addr(45,SIOCGIFBRDADDR,&ifl) == 0) {
inet_ntop(ifl.ifr_addr.sa_family,addr.size());
}
} else {
addr = LOOPBACK_TEMPLATE;
}
}
}
return addr;
}
int get_mtu(struct ifreq *ifr) {
int mtu = 0;
struct ifreq ifl;
int sock = socket(AF_INET,SIOCGIFMTU,&ifl) == 0) {
mtu = ifl.ifr_mtu;
}
}
return mtu;
}
/**
* Return a list of interface (network layer) addresses.
* Accept or return only AF_INET socket addresses are
* IP-specific and perhaps should rather be documented in ip(7).
* [https://www.man7.org/linux/man-pages/man7/ip.7.html]
* This currently means only addresses of the AF_INET (IPv4)
* family for compatibility.
* The names of interfaces with no addresses or that don't have the
* IFF_RUNNING flag set can be found via /proc/net/dev.
*/
std::vector<iface> get_ifce_list() {
std::vector<iface> ifaces;
int socketfd;
printf("Opening socket...");
socketfd = socket(AF_INET,0);
if (socketfd >= 0) {
printf(" OK\n");
printf("Discovering interfaces...\n");
auto data = get_active_interfaces();
for (struct ifreq *ifr = (struct ifreq*) std::get<0>(data);
(char*) ifr < std::get<0>(data) + std::get<1>(data); ifr++) {
switch (ifr->ifr_addr.sa_family) {
case AF_INET: {
iface ifc;
ifc.name = get_ifname(ifr);
ifc.address = get_ipv4_addr(ifr);
ifc.netmask = get_netmask(ifr);
ifc.broadcast = get_broadcast(ifr);
ifc.hwaddr = get_mac_addr(ifr);
ifc.mtu = get_mtu(ifr);
ifaces.emplace_back(ifc);
break;
}
#if USE_IPV6
case AF_INET6:
break;
#endif
}
}
close(socketfd);
} else {
printf(" Failed!\n");
}
return ifaces;
}
// This is the main function
int main() {
std::time_t start = std::time(nullptr),stop;
std::vector<iface> _ifaces = get_ifce_list();
for (auto &_iface : _ifaces) {
print_iface(_iface);
}
stop = std::time(nullptr);
std::cout << "End of code. ran for: " << stop - start << " seconds. "
<< std::endl;
return 0;
}
解决方法
这段代码有几个方面的问题：
std::tuple<char*,int> get_active_interfaces() {
int socketfd;
struct ifconf conf;
char data[4096];
socketfd = socket(AF_INET,SOCK_DGRAM,0);
conf.ifc_len = sizeof(data);
conf.ifc_buf = (caddr_t) data;
if (ioctl(socketfd,SIOCGIFCONF,&conf) < 0) {
fprintf(stderr,"ioctl error: %s",std::strerror(errno));
return std::make_tuple(nullptr,0);
} else {
return std::make_tuple(data,conf.ifc_len);
}
}
基本问题是你返回的元组包含一个指向data的指针，它是一个局部变量。任何在函数外使用该指针都是错误的。
IIUC，你想要做的是迭代 ifc_req，它被定义为不超过 ifc_len 字节长的接口列表。
根据我的 Ubuntu 手册页，最通用的方法是首先使用 ifc_req == NULL 进行一次调用，在这种情况下，系统将使用所需的大小填充 ifc_len。使用
size_t N = ifc_len / sizeof(ifc_req[0]);
conf.ifc_req = new ifreq(N);
我将重新定义函数以返回 std::tuple<struct ifreq *,size_t>，并将 second 的含义更改为元素数，而不是字节数。这样，调用者可以围绕结构数组进行组织，您就可以完成字节和强制转换的工作。由于您使用的是 C++，因此您可以非常巧妙地使用 std::for_each 遍历数组。
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