本文共 30659 字，大约阅读时间需要 102 分钟。
#ifdef WIN32//#include//#include //#include #include #else#include #include #include #include #include #include #endif//返回IP地址static std::string GetLocalIPAddress(void){ std::string strRetip;#ifdef WIN32 //windows WSADATA wsaData; if (WSAStartup(MAKEWORD(2, 0), &wsaData) == 0) { char name[255] = { 0 }; if (gethostname(name, sizeof(name)) == 0) { PHOSTENT hostinfo; if ((hostinfo = gethostbyname(name)) != NULL) { char* tmpip = inet_ntoa(*(struct in_addr*)*hostinfo->h_addr_list); strRetip = tmpip; } } WSACleanup(); }#else //linux#if 1 struct ifaddrs* ifAddrStruct = NULL; getifaddrs(&ifAddrStruct); for (struct ifaddrs* ifa = ifAddrStruct; ifa != NULL; ifa = ifa->ifa_next) { if (ifa->ifa_addr != nullptr && ifa->ifa_addr->sa_family == AF_INET) { //check it is a valid IP4 Address void* tmpAddrPtr = &((struct sockaddr_in*)ifa->ifa_addr)->sin_addr; char addressBuffer[INET_ADDRSTRLEN]; inet_ntop(AF_INET, tmpAddrPtr, addressBuffer, INET_ADDRSTRLEN); std::string strname = ifa->ifa_name; if (strcmp(ifa->ifa_name, "lo") != 0 && strcmp("127.0.0.1", addressBuffer) != 0) { strRetip = addressBuffer; if (!strRetip.empty()) { break; } } } } if (ifAddrStruct != NULL) { freeifaddrs(ifAddrStruct); }#else int sock_fd, intrface; struct ifreq buf[INET_ADDRSTRLEN]; struct ifconf ifc; char* local_ip = NULL; if ((sock_fd = socket(AF_INET, SOCK_DGRAM, 0)) >= 0) { ifc.ifc_len = sizeof(buf); ifc.ifc_buf = (caddr_t)buf; if (!ioctl(sock_fd, SIOCGIFCONF, (char*)&ifc)) { intrface = ifc.ifc_len / sizeof(struct ifreq); while (intrface-- > 0) { if (!(ioctl(sock_fd, SIOCGIFADDR, (char*)&buf[intrface]))) { local_ip = NULL; local_ip = inet_ntoa(((struct sockaddr_in*)(&buf[intrface].ifr_addr))->sin_addr); if (local_ip) { if (strcmp("127.0.0.1", local_ip) != 0) { strRetip = local_ip; break; } } } } } close(sock_fd); }#endif#endif return strRetip;}
ifaddrs结构体定义如下：
//C代码 struct ifaddrs { struct ifaddrs *ifa_next; /* Next item in list */ char *ifa_name; /* Name of interface */ unsigned int ifa_flags; /* Flags from SIOCGIFFLAGS */ struct sockaddr *ifa_addr; /* Address of interface */ struct sockaddr *ifa_netmask; /* Netmask of interface */ union { struct sockaddr *ifu_broadaddr; /* Broadcast address of interface */ struct sockaddr *ifu_dstaddr; /* Point-to-point destination address */ } ifa_ifu; #define ifa_broadaddr ifa_ifu.ifu_broadaddr #define ifa_dstaddr ifa_ifu.ifu_dstaddr void *ifa_data; /* Address-specific data */ };
ifa_next指向链表的下一个成员；ifa_name是接口名称，以0结尾的字符串，比如eth0，lo；ifa_flags是接口的标识位（比如当IFF_BROADCAST或IFF_POINTOPOINT设置到此标识位时，影响联合体变量ifu_broadaddr存储广播地址或ifu_dstaddr记录点对点地址）；ifa_netmask存储该接口的子网掩码；结构体变量存储广播地址或点对点地址（见括弧介绍ifa_flags）；ifa_data存储了该接口协议族的特殊信息，它通常是NULL（一般不关注他）。
函数getifaddrs（int getifaddrs (struct ifaddrs **__ifap)）获取本地网络接口信息，将之存储于链表中，链表头结点指针存储于__ifap中带回，函数执行成功返回0，失败返回-1，且为errno赋值。
很显然，函数getifaddrs用于获取本机接口信息，比如最典型的获取本机IP地址。
tcp/ip协议中，专门保留了三个IP地址区域作为私有地址，其地址范围如下：
10.0.0.0/8：10.0.0.0～10.255.255.255 172.16.0.0/12：172.16.0.0～172.31.255.255 192.168.0.0/16：192.168.0.0～192.168.255.255 使用保留地址的 网络只能在内部进行通信，而不能与其他 网络互连。如果要与外部通信，那么必须通过网关与外部通信，这里使用了NAT, NAPT技术就是用来保证通信的代理机制。 另外，一些宽带运营商尽管也使用了非私有地址分配给用户使用，但是由于路由设置的原因，Internet上的其他用户并不能访问到这些ip。上面2部分IP都可称为内网IP，下面这部分IP不列入本次讨论范围。 如果自己机器上 网络接口的ip地址落在上述保留地址的范围内，则可以肯定自己处于内网模式下。 NAT要求整个服务的连接是从内网向外网主动发起的，而外网的用户无法直接（主动）向内网的服务发起连接请求，除非在NAT的（所有）网关上针对服务的端口作了端口映射。NAT方式要求最外围的网关至少有一个公网的IP，可以访问显IP的外部服务器如： http://ipid.shat.net/ 获取到外部IP，将这个IP与自己机器上 网络接口的ip比较，即可知道自己的ip是不是内网IP。// 0xa -- "10.0.0.0">>24; 0xc0a8--"192.168.0.0.">>16; 0x2b0--"127.17.0.1">>22int isInnerIP( uint32_t a_ip ){ int bValid = -1; if( (a_ip>>24 == 0xa) || (a_ip>>16 == 0xc0a8) || (a_ip>>22 == 0x2b0) ) { bValid = 0; } return bValid;}int isInnerIP( char* a_strip ){ return 0;}
int getHostIP() //return int{ struct sockaddr_in localAddr, destAddr; struct hostent* h; char temp[128]; int nRect = gethostname(temp, 128); printf("ipaddr src3 is: %s/n", temp); if(nRect !=0) { printf("error"); } h = gethostbyname(temp); if(h) { for(int nAdapter=0; h->h_addr_list[nAdapter]; nAdapter++) { memcpy(&destAddr.sin_addr.s_addr, h->h_addr_list[nAdapter], h->h_length); // 输出机器的IP地址. printf("Address string: %s/n", inet_ntoa(destAddr.sin_addr)); // 显示地址串 printf("Address int: %d/n", destAddr.sin_addr.s_addr); // 转化为整形数字 } } return 0;} int isCheckTrue(char* strip){ int value; for( int i = 0; i < strlen(strip); i++) { // let's check if all entered char in entered // IP address are digits if(strip[i] == '.') continue; if(isdigit(strip[i]) == 0) { return -1; } } return 0;}
int str2intIP(char* strip) //return int ip{ int intIP; if(!(intIP = inet_addr(strip))) { perror("inet_addr failed./n"); return -1; } return intIP;}
这 是一项不太清晰而且没有多大意义的工作。一个原因是网络地址的设置非常灵活而且都是允许用户进行个性化设置的，比如一台计算机上可以有多块物理网卡或者虚 拟网卡，一个网卡上可以绑定多个IP地址，用户可以为网卡设置别名，可以重命名网卡，用户计算机所在网络拓扑结构未知，主机名设置是一个可选项并且同样可 以为一个计算机绑定多个主机名等，这些信息都会有影响。脱离了网络连接，单独的网络地址没有任何意义。编程中遇到必须获取计算机IP的场景，应该考虑将这 一选项放到配置文件中，由用户自己来选择。
编程获取IP地址大约有以下三种思路：#include运行： [whb@jcwkyl c]$ ./local_ip hostname: jcwkyl.jlu.edu.cn address list: 10.60.56.90#include #include #include #include #include int main() { char hname[128]; struct hostent *hent; int i; gethostname(hname, sizeof(hname)); //hent = gethostent(); hent = gethostbyname(hname); printf("hostname: %s/naddress list: ", hent->h_name); for(i = 0; hent->h_addr_list[i]; i++) { printf("%s/t", inet_ntoa(*(struct in_addr*)(hent->h_addr_list[i]))); } return 0;}
#include运行 ： [whb@jcwkyl c]$ ./local_ip2 lo IP Address 127.0.0.1 eth0 IP Address 10.60.56.90 eth0:1 IP Address 192.168.1.3 lo IP Address :: eth0 IP Address ::2001:da8:b000:6213:20f:1fff eth0 IP Address 0:0:fe80::20f:1fff#include #include #include #include #include int main (int argc, const char * argv[]) { struct ifaddrs * ifAddrStruct=NULL; void * tmpAddrPtr=NULL; getifaddrs(&ifAddrStruct); while (ifAddrStruct!=NULL) { if (ifAddrStruct->ifa_addr->sa_family==AF_INET) { // check it is IP4 // is a valid IP4 Address tmpAddrPtr=&((struct sockaddr_in *)ifAddrStruct->ifa_addr)->sin_addr; char addressBuffer[INET_ADDRSTRLEN]; inet_ntop(AF_INET, tmpAddrPtr, addressBuffer, INET_ADDRSTRLEN); printf("%s IP Address %s/n", ifAddrStruct->ifa_name, addressBuffer); } else if (ifAddrStruct->ifa_addr->sa_family==AF_INET6) { // check it is IP6 // is a valid IP6 Address tmpAddrPtr=&((struct sockaddr_in *)ifAddrStruct->ifa_addr)->sin_addr; char addressBuffer[INET6_ADDRSTRLEN]; inet_ntop(AF_INET6, tmpAddrPtr, addressBuffer, INET6_ADDRSTRLEN); printf("%s IP Address %s/n", ifAddrStruct->ifa_name, addressBuffer); } ifAddrStruct=ifAddrStruct->ifa_next; } return 0;}
略
std::string GetLocalIp() { int sock_get_ip; char ipaddr[50]; struct sockaddr_in *sin; struct ifreq ifr_ip; if ((sock_get_ip=socket(AF_INET, SOCK_STREAM, 0)) == -1) { printf("socket create failse...GetLocalIp!/n"); return ""; } memset(&ifr_ip, 0, sizeof(ifr_ip)); strncpy(ifr_ip.ifr_name, "eth0", sizeof(ifr_ip.ifr_name) - 1); if( ioctl( sock_get_ip, SIOCGIFADDR, &ifr_ip) < 0 ) { return ""; } sin = (struct sockaddr_in *)&ifr_ip.ifr_addr; strcpy(ipaddr,inet_ntoa(sin->sin_addr)); printf("local ip:%s /n",ipaddr); close( sock_get_ip ); return std::string( ipaddr ); }
int SetLocalIp( const char *ipaddr ) { int sock_set_ip; struct sockaddr_in sin_set_ip; struct ifreq ifr_set_ip; bzero( &ifr_set_ip,sizeof(ifr_set_ip)); if( ipaddr == NULL ) return -1; if(sock_set_ip = socket( AF_INET, SOCK_STREAM, 0 ) == -1); { perror("socket create failse...SetLocalIp!/n"); return -1; } memset( &sin_set_ip, 0, sizeof(sin_set_ip)); strncpy(ifr_set_ip.ifr_name, "eth0", sizeof(ifr_set_ip.ifr_name)-1); sin_set_ip.sin_family = AF_INET; sin_set_ip.sin_addr.s_addr = inet_addr(ipaddr); memcpy( &ifr_set_ip.ifr_addr, &sin_set_ip, sizeof(sin_set_ip)); if( ioctl( sock_set_ip, SIOCSIFADDR, &ifr_set_ip) < 0 ) { perror( "Not setup interface/n"); return -1; } //设置激活标志 ifr_set_ip.ifr_flags |= IFF_UP |IFF_RUNNING; //get the status of the device if( ioctl( sock_set_ip, SIOCSIFFLAGS, &ifr_set_ip ) < 0 ) { perror("SIOCSIFFLAGS"); return -1; } close( sock_set_ip ); return 0; }
std:string GetLocalMac() { int sock_mac; struct ifreq ifr_mac; char mac_addr[30]; sock_mac = socket( AF_INET, SOCK_STREAM, 0 ); if( sock_mac == -1) { perror("create socket falise...mac/n"); return ""; } memset(&ifr_mac,0,sizeof(ifr_mac)); strncpy(ifr_mac.ifr_name, "eth0", sizeof(ifr_mac.ifr_name)-1); if( (ioctl( sock_mac, SIOCGIFHWADDR, &ifr_mac)) < 0) { printf("mac ioctl error/n"); return ""; } sprintf(mac_addr,"%02x%02x%02x%02x%02x%02x", (unsigned char)ifr_mac.ifr_hwaddr.sa_data[0], (unsigned char)ifr_mac.ifr_hwaddr.sa_data[1], (unsigned char)ifr_mac.ifr_hwaddr.sa_data[2], (unsigned char)ifr_mac.ifr_hwaddr.sa_data[3], (unsigned char)ifr_mac.ifr_hwaddr.sa_data[4], (unsigned char)ifr_mac.ifr_hwaddr.sa_data[5]); printf("local mac:%s /n",mac_addr); close( sock_mac ); return std:string( mac_addr ); }
std:string GetLocalNetMask() { int sock_netmask; char netmask_addr[50]; struct ifreq ifr_mask; struct sockaddr_in *net_mask; sock_netmask = socket( AF_INET, SOCK_STREAM, 0 ); if( sock_netmask == -1) { perror("create socket failture...GetLocalNetMask/n"); return ""; } memset(&ifr_mask, 0, sizeof(ifr_mask)); strncpy(ifr_mask.ifr_name, ifname, sizeof(ifr_mask.ifr_name )-1); if( (ioctl( sock_netmask, SIOCGIFNETMASK, &ifr_mask ) ) < 0 ) { printf("mac ioctl error/n"); return ""; } net_mask = ( struct sockaddr_in * )&( ifr_mask.ifr_netmask ); strcpy( netmask_addr, inet_ntoa( net_mask -> sin_addr ) ); printf("local netmask:%s/n",netmask_addr); close( sock_netmask ); return std:string( netmask_addr ); }
bool SetLocalNetMask(const char *szNetMask) { int sock_netmask; char netmask_addr[32]; struct ifreq ifr_mask; struct sockaddr_in *sin_net_mask; sock_netmask = socket( AF_INET, SOCK_STREAM, 0 ); if( sock_netmask == -1) { perror("Not create network socket connect/n"); return false; } memset(&ifr_mask, 0, sizeof(ifr_mask)); strncpy(ifr_mask.ifr_name, "eth0", sizeof(ifr_mask.ifr_name )-1); sin_net_mask = (struct sockaddr_in *)&ifr_mask.ifr_addr; sin_net_mask -> sin_family = AF_INET; inet_pton(AF_INET, szNetMask, &sin_net_mask ->sin_addr); if(ioctl(sock_netmask, SIOCSIFNETMASK, &ifr_mask ) < 0) { printf("sock_netmask ioctl error/n"); return false; } return true;}
std::string GetGateWay() { FILE *fp; char buf[512]; char cmd[128]; char gateway[30]; char *tmp; strcpy(cmd, "ip route"); fp = popen(cmd, "r"); if(NULL == fp) { perror("popen error"); return ""; } while(fgets(buf, sizeof(buf), fp) != NULL) { tmp =buf; while(*tmp && isspace(*tmp)) ++ tmp; if(strncmp(tmp, "default", strlen("default")) == 0) break; } sscanf(buf, "%*s%*s%s", gateway); printf("default gateway:%s/n", gateway); pclose(fp); return std::string(gateway); }
int SetGateWay(const char *szGateWay) { int ret = 0; char cmd[128]; QString DefGW = GetGateWay(); const char *strGW = DefGW.latin1(); strcpy(cmd, "route del default gw "); strcat(cmd, strGW); ret = system(cmd); if(ret < 0) { perror("route error"); return -1; } strcpy(cmd, "route add default gw "); strcat(cmd, szGateWay); ret = system(cmd); if(ret < 0) { perror("route error"); return -1; } return ret; }
有时候，写程序的时候需要获取计算机的网络信息，比如IP地址、电脑名称、DNS等信息。IP地址和电脑名称是比较容易获取到的，而要想获取地址掩码、DNS、网关等信息就有些麻烦了。
在Windows下我们一般都是通过从注册表读取这些信息。在Linux怎么做呢？其实，Linux下更加容易一些。因为我们可以拿现成的程序看它的源代码。通过阅读其源代码找到解决该问题的方法。那么，看哪个程序的源代码呢？如果你使用过Linux，并且比较熟悉的话就肯定知道一个命令ifconfig。这个命令和Windows下的ipconfig差不多，都可以输出网卡的信息，其中就包含DNS、掩码等信息。所以，我们可以通过看它的源代码来找到解决该问题的方法。
并没有那个系统调用提供网卡数量的获取。但是，我们可以通过强大的proc文件系统获取网卡数量的信息。实际上，ifconfig也是这样做的，请看示例代码如下：
#include#include #include int GetNetCardCount(){ int nCount = 0; FILE* f = fopen("/proc/net/dev", "r"); if (!f) { fprintf(stderr, "Open /proc/net/dev failed!errno:%d\n", errno); return nCount; } char szLine[512]; fgets(szLine, sizeof(szLine), f); /* eat line */ fgets(szLine, sizeof(szLine), f); while(fgets(szLine, sizeof(szLine), f)) { char szName[128] = {0}; sscanf(szLine, "%s", szName); int nLen = strlen(szName); if (nLen <= 0)continue; if (szName[nLen - 1] == ':') szName[nLen - 1] = 0; if (strcmp(szName, "lo") == 0)continue; nCount++; } fclose(f); f = NULL; return nCount; } int main(int argc, char* argv[]) { printf("NetCardCount: %d\n", GetNetCardCount()); return 0; }
获取IP、掩码、MAC和广播地址是比较容易的，只需要调用对应的IOCTL即可。只是大家对Linux下的IOCTL可能不太熟悉。请看示例代码
void DispNetInfo(const char* szDevName){ int s = socket(AF_INET, SOCK_DGRAM, 0); if (s < 0) { fprintf(stderr, "Create socket failed!errno=%d", errno); return; } struct ifreq ifr; unsigned char mac[6]; unsigned long nIP, nNetmask, nBroadIP; printf("%s:\n", szDevName); strcpy(ifr.ifr_name, szDevName); if (ioctl(s, SIOCGIFHWADDR, &ifr) < 0) { return; } memcpy(mac, ifr.ifr_hwaddr.sa_data, sizeof(mac)); printf("\tMAC: %02x-%02x-%02x-%02x-%02x-%02x\n", mac[0], mac[1], mac[2], mac[3], mac[4], mac[5]); strcpy(ifr.ifr_name, szDevName); if (ioctl(s, SIOCGIFADDR, &ifr) < 0) { nIP = 0; } else { nIP = *(unsigned long*)&ifr.ifr_broadaddr.sa_data[2]; } printf("\tIP: %s\n", inet_ntoa(*(in_addr*)&nIP)); strcpy(ifr.ifr_name, szDevName); if (ioctl(s, SIOCGIFBRDADDR, &ifr) < 0) { nBroadIP = 0; } else { nBroadIP = *(unsigned long*)&ifr.ifr_broadaddr.sa_data[2]; } printf("\tBroadIP: %s\n", inet_ntoa(*(in_addr*)&nBroadIP)); strcpy(ifr.ifr_name, szDevName); if (ioctl(s, SIOCGIFNETMASK, &ifr) < 0) { nNetmask = 0; } else { nNetmask = *(unsigned long*)&ifr.ifr_netmask.sa_data[2]; } printf("\tNetmask: %s\n", inet_ntoa(*(in_addr*)&nNetmask)); close(s);}
怎么获取网关呢？这个稍微有点麻烦一些，不过和获取网卡数量相似，都是通过proc文件系统。这次分析的/proc/net/route文件。我就不再贴出示例代码了。
最后，我把运行示例程序获取到的信息附上，以供大家有个直观的认识：
eth0:
MAC: 08-00-27-98-bf-f3
IP: 192.168.1.106
BroadIP: 255.255.255.255
Netmask: 255.255.255.0
Gateway: 192.168.1.1
eth1:
MAC: 08-00-27-16-f4-bf
IP: 192.168.1.108
BroadIP: 192.168.1.255
Netmask: 255.255.255.0
Gateway: 0.0.0.0
eth2:
MAC: 08-00-27-37-9c-91
IP: 0.0.0.0
BroadIP: 0.0.0.0
Netmask: 0.0.0.0
Gateway: 0.0.0.0
eth3:
MAC: 08-00-27-5a-d2-39
IP: 0.0.0.0
BroadIP: 0.0.0.0
Netmask: 0.0.0.0
Gateway: 0.0.0.0
NetCardCount: 4
DNS 0: 218.2.135.1
DNS 1: 61.147.37.1
//代码根据UNP和man手册编写 //适用于LINUX/BSD(FreeBSD, MacOS X) #include#include #include #include #include #include #include #include #include int main(void) { struct ifaddrs *ifc, *ifc1; char ip[64]; char nm[64]; if (0 != getifaddrs(&ifc)) return(-1); ifc1 = ifc; printf("Iface\tIP address\tNetmask\n"); for(; NULL != ifc; ifc = (*ifc).ifa_next) { printf("%s", (*ifc).ifa_name); if (NULL != (*ifc).ifa_addr) { inet_ntop(AF_INET, &(((struct sockaddr_in*)((*ifc).ifa_addr))->sin_addr), ip, 64); printf("\t%s", ip); } else { printf("\t\t"); } if (NULL != (*ifc).ifa_netmask) { inet_ntop(AF_INET, &(((struct sockaddr_in*)((*ifc).ifa_netmask))->sin_addr), nm, 64); printf("\t%s", nm); } else { printf("\t\t"); } printf("\n"); } freeifaddrs(ifc1); return(0); }
//============原来的============ struct ifaddrs *ifap, *ifaphead, *ifaTmp; getifaddrs(&ifap); ifaphead = ifap; while((ifapTmp = ifap) != NULL) { //实际任务代码 ifap = ifapTmp->ifa_next; } freeifaddrs(ifaphead); //=========修改后======== struct ifaddrs *ifap, *ifaphead; getifaddrs(&ifap); ifaphead = ifap; while(ifap != NULL) { //实际任务代码 ifap = ifa_next; } freeifaddrs(ifaphead); //================== 仅仅是用了一个ifapTmp来代替ifap做事,区别仅此而已(而且我也忘了一开始为什么要用ifapTmp....) 但是最后都是用了freeifaddrs(ifaphead)啊,并没有传错指针啊???? 中间的代码并没有对这段数据做任何修改啊..... 请指教一下,这唯一的区别为什么会造成我原先的代码freeifaddrs失败?谢谢! ifaphead = ifap; //这里用ifaphead保存ifap指针地址 while((ifapTmp = ifap) != NULL) { ifap = ifapTmp->ifa_next; //这里修改了ifap的地址 } freeifaddrs(ifaphead); //由于ifap的地址修改，所以ifaphead已经是无效指针。 ioctl及getifaddrs读取IPv4,IPv6网卡信息
使用ioctl的SIOCGIFCONF可以读取所有网卡信息。ioctl调用后返回指向ifconf的结构链表，其中包含了指向ifreq的结构指针。ifconf及ifreq定义在net/if.h中。
《UNIX网络编程》中提供了get_ifi_info函数的实现方法，使用这种方式来获取网络信息。在LINUX下，这种方式不能获得IPV6的网卡信息。《UNIX网络编程》中有如下描述：
在支持IPV6的系统中，没有关于对SIOCGIFCONF请求是否返回IPV6地址的标准。我们给支持IPV6的新系统增加了一个case语句， 这是为了预防万一。问题在于ifreq中的联合把返回的地址定义成一个通用的16字节套接口地址结构，适合16字节的IPV4 socket_in结构，但对于24字节的IPV6 socket_in6结构太小了。如果返回IPV6地址，将可能破环现有的在每个ifreq结构中采用固定大小的套接口地址结构的代码。
经测试，在fedor6-2.6.18kernel中无法返回ipv6地址，事实上，返回的地址簇总是AF_INET,而并非AF_INET6。
这种方法的实现代码如下： net_if.h#ifndef __NET_INF_H#define __NET_INF_H#define IFI_NAME 16#define IFI_HADDR 8typedef struct ifi_info{ char ifi_name[IFI_NAME]; u_char ifi_haddr[IFI_HADDR]; u_short ifi_hlen; short ifi_flags; short ifi_myflags; struct sockaddr *ifi_addr; struct sockaddr *ifi_brdaddr; struct sockaddr *ifi_dstaddr; struct ifi_info *ifi_next;}ifi_info;#define IFI_ALIAS 1struct ifi_info *get_ifi_info(int, int);void free_ifi_info(struct ifi_info *);#endif net_if.c
#include "net_if.h"ifi_info *get_ifi_info(int family, int doaliases){ ifi_info *ifi, *ifihead, **ifipnext; int sockfd, len, lastlen, flags, myflags; char *ptr, *buf, lastname[IFNAMSIZ], *cptr; struct ifconf ifc; struct ifreq *ifr, ifrcopy; struct sockaddr_in *sinptr; if ((sockfd=socket(family, SOCK_DGRAM, 0))<0) { printf("socket error.\n"); exit(1); } lastlen = 0; len = 10*sizeof(struct ifreq); while (1) { buf = (char*)malloc(len); ifc.ifc_len = len; ifc.ifc_buf = buf; if (ioctl(sockfd, SIOCGIFCONF, &ifc)<0) { if (errno!=EINVAL||lastlen!=0) { printf("ioctl error.\n"); } } else { if (ifc.ifc_len == lastlen) break; lastlen = ifc.ifc_len; } len += 10*sizeof(struct ifreq); free(buf); } ifihead = NULL; ifipnext = &ifihead; lastname[0] = 0; for (ptr = buf; ptrifr->ifr_addr.sa_len?sizeof(struct sockaddr):ifr->ifr_addr.sa_len;#else switch (ifr->ifr_addr.sa_family) {#ifdef IPV6 case AF_INET6: len = sizeof(struct sockaddr_in6); break;#endif case AF_INET: default: len = sizeof(struct sockaddr); break; }#endif ptr += sizeof(ifr->ifr_name) + len; if (ifr->ifr_addr.sa_family != family) continue; myflags = 0; if ((cptr=strchr(ifr->ifr_name, ':'))!=NULL) *cptr = 0; if (strncmp(lastname, ifr->ifr_name, IFNAMSIZ)==0) { if (doaliases == 0) continue; myflags = IFI_ALIAS; } memcpy(lastname, ifr->ifr_name, IFNAMSIZ); ifrcopy = *ifr; ioctl(sockfd, SIOCGIFFLAGS, &ifrcopy); flags = ifrcopy.ifr_flags; if ((flags&IFF_UP)==0) continue; /* if ((flags&IFF_BROADCAST)==0) continue; */ ifi = calloc(1, sizeof(struct ifi_info)); *ifipnext = ifi; ifipnext = &ifi->ifi_next; ifi->ifi_flags = flags; ifi->ifi_myflags = myflags; memcpy(ifi->ifi_name, ifr->ifr_name, IFI_NAME); ifi->ifi_name[IFI_NAME-1] = '\0'; switch (ifr->ifr_addr.sa_family) { case AF_INET: sinptr = (struct sockaddr_in *)&ifr->ifr_addr; if (ifi->ifi_addr == NULL) { ifi->ifi_addr = calloc(1, sizeof(struct sockaddr_in)); memcpy(ifi->ifi_addr, sinptr, sizeof(struct sockaddr_in));#ifdef SIOCGIFBRDADDR if (flags & IFF_BROADCAST) { ioctl(sockfd, SIOCGIFBRDADDR, &ifrcopy); sinptr = (struct sockaddr_in *)&ifrcopy.ifr_broadaddr; ifi->ifi_brdaddr = calloc(1, sizeof(struct sockaddr_in)); memcpy(ifi->ifi_brdaddr, sinptr, sizeof(struct sockaddr_in)); }#endif#ifdef SIOCGIFDSTADDR if (flags & IFF_POINTOPOINT) { ioctl(sockfd, SIOCGIFDSTADDR, &ifrcopy); sinptr = (struct sockaddr_in*)&ifrcopy.ifr_dstaddr; ifi->ifi_dstaddr = calloc(1, sizeof(struct sockaddr_in)); memcpy(ifi->ifi_dstaddr, sinptr, sizeof(struct sockaddr_in)); }#endif } break; default: break; } } free(buf); return(ifihead);}void free_ifi_info(ifi_info *ifihead){ ifi_info *ifi, *ifinext; for (ifi=ifihead; ifi!=NULL; ifi=ifinext) { if (ifi->ifi_addr!=NULL) free(ifi->ifi_addr); if (ifi->ifi_brdaddr!=NULL) free(ifi->ifi_brdaddr); if (ifi->ifi_dstaddr!=NULL) free(ifi->ifi_dstaddr); ifinext = ifi->ifi_next; free(ifi); }}char *sock_ntop(const struct sockaddr *sa, socklen_t salen){ char portstr[7]; static char str[128]; switch (sa->sa_family) { case AF_INET: { struct sockaddr_in *sin = (struct sockaddr_in *)sa; if (inet_ntop(AF_INET, &sin->sin_addr, str, sizeof(str))==NULL) return NULL; if (ntohs(sin->sin_port)!=0) { snprintf(portstr, sizeof(portstr), ".%d", ntohs(sin->sin_port)); strcat(str, portstr); } return str; } break; case AF_INET6: { struct sockaddr_in6 *sin = (struct sockaddr_in6 *)sa; if (inet_ntop(AF_INET6, &sin->sin6_addr, str, sizeof(str))==NULL) return NULL; if (ntohs(sin->sin6_port)!=0) { snprintf(portstr, sizeof(portstr), ".%d", ntohs(sin->sin6_port)); strcat(str, portstr); } return str; } break; default: return NULL; break; }}int main(int argc, char *argv[]){ ifi_info *ifi, *ifihead; struct sockaddr *sa; u_char *ptr; int i, family, doaliases; if (argc!=3) { printf("usage: ./prifinfo "); exit(1); } if (strcmp(argv[1], "inet4") == 0) family = AF_INET;#ifdef IPV6 else if (strcmp(argv[1], "inet6") == 0) family =AF_INET6;#endif else { printf("invalid"); exit(1); } doaliases = atoi(argv[2]); for(ifihead = ifi = get_ifi_info(family, doaliases); ifi!=NULL;ifi=ifi->ifi_next) { printf("%s:<", ifi->ifi_name); if (ifi->ifi_flags&IFF_UP) printf("UP"); if (ifi->ifi_flags&IFF_BROADCAST) printf("BCAST"); if (ifi->ifi_flags&IFF_MULTICAST) printf("MCAST"); if (ifi->ifi_flags&IFF_LOOPBACK) printf("LOOP"); if (ifi->ifi_flags&IFF_POINTOPOINT) printf("P2P"); printf(">\n"); if ((i=ifi->ifi_hlen)>0) { ptr = ifi->ifi_haddr; do { printf("%s%x", (i==ifi->ifi_hlen)?" ":":", *ptr++); }while(--i>0); printf("\n"); } if ((sa=ifi->ifi_addr)!=NULL) printf(" IP addr: %s\n", sock_ntop(sa, sizeof(*sa))); if ((sa=ifi->ifi_brdaddr)!=NULL) printf(" broadcast addr: %s\n", sock_ntop(sa, sizeof(*sa))); if ((sa=ifi->ifi_dstaddr)!=NULL) printf(" destnation addr: %s\n", sock_ntop(sa, sizeof(*sa))); } free_ifi_info(ifihead); exit(0);} 使用gcc net_if.c -o net_if -DIPV6编译，在IPV4模式下运行输出为：
[root@localhost net_if]./net_if inet4 1
lo: IP addr: 127.0.0.1 eth1: IP addr: 192.168.1.2 broadcast addr: 192.168.1.255 eth0: IP addr: 192.168.125.99 broadcast addr: 192.168.125.255
执行./net_if inet6 1在输出为空。
第二种方式是使用getifaddrs函数获取，需要包含ifaddrs.h头文件，这种方式可以获得IPV6地址，改写的《UNIX网络编程》中的get_ifi_info函数如下所示：
znet.h
#ifndef __ZNET_H__#define __ZNET_H__#define IFI_NAME 16 /* same as IFNAMSIZ in */#define IFI_HADDR 8 /* allow for 64-bit EUI-64 in future */struct ifi_info { char ifi_name[IFI_NAME]; /* interface name, null-terminated */ short ifi_index; /* interface index */ short ifi_flags; /* IFF_xxx constants from */ struct sockaddr *ifi_addr; /* primary address */ struct sockaddr *ifi_brdaddr;/* broadcast address */ struct ifi_info *ifi_next; /* next of these structures */};struct ifi_info* get_ifi_info(int, int);void free_ifi_info(struct ifi_info *);#endif znet.c
#include "znet.h"struct ifi_info* get_ifi_info(int family, int doaliases) { struct ifi_info *ifi, *ifihead, **ifipnext,*p; struct sockaddr_in *sinptr; struct sockaddr_in6 *sin6ptr; struct ifaddrs *ifas;// char addr[128]; int sockfd; ifihead = NULL; ifipnext = &ifihead; if(getifaddrs(&ifas)!=0) return ; for(;ifas!=NULL;ifas=(*ifas).ifa_next) { if (((*ifas).ifa_addr)->sa_family != family) continue; // ignore if not desired address family/* printf("%s %d\n",(*ifas).ifa_name,((*ifas).ifa_addr)->sa_family); if(((*ifas).ifa_addr)->sa_family!=AF_INET6) inet_ntop(AF_INET,&(((struct sockaddr_in *)((*ifas).ifa_addr))->sin_addr),addr,sizeof(addr)); else inet_ntop(AF_INET6,&(((struct sockaddr_in6 *)((*ifas).ifa_addr))->sin6_addr),addr,sizeof(addr)); printf("%s\t",addr); printf("\n");*/ ifi = (struct ifi_info*)calloc(1,sizeof(struct ifi_info)); *ifipnext = ifi; ifipnext = &ifi->ifi_next; ifi->ifi_flags = (*ifas).ifa_flags; memcpy(ifi->ifi_name, (*ifas).ifa_name, IFI_NAME); ifi->ifi_name[IFI_NAME-1] = '\0'; switch (((*ifas).ifa_addr)->sa_family) { case AF_INET: sinptr = (struct sockaddr_in *) (*ifas).ifa_addr; ifi->ifi_addr = (struct sockaddr*)calloc(1, sizeof(struct sockaddr_in)); memcpy(ifi->ifi_addr, sinptr, sizeof(struct sockaddr_in));#ifdef SIOCGIFBRDADDR if (ifi->ifi_flags & IFF_BROADCAST) { sinptr = (struct sockaddr_in *) (*ifas).ifa_broadaddr; ifi->ifi_brdaddr = (struct sockaddr*)calloc(1, sizeof(struct sockaddr_in)); memcpy(ifi->ifi_brdaddr, sinptr, sizeof(struct sockaddr_in)); }#endif break; case AF_INET6: sin6ptr = (struct sockaddr_in6 *) (*ifas).ifa_addr; ifi->ifi_addr = (struct sockaddr*)calloc(1, sizeof(struct sockaddr_in6)); memcpy(ifi->ifi_addr, sin6ptr, sizeof(struct sockaddr_in6)); break; default: break; } } freeifaddrs(ifas); return(ifihead);}int main(int argc, char *argv[]) { int family; if (argc!=2) { printf("usage: ./znet \n"); exit(1); } if (strcmp(argv[1], "inet4") == 0) family = AF_INET; else if (strcmp(argv[1], "inet6") == 0) family =AF_INET6; else { printf("invalid\n"); exit(1); } char addr[128]; struct ifi_info *ifi, *ifihead; printf("name\tflag\tIP\t\tbroadcastaddr\n"); for (ifihead = ifi = get_ifi_info(family,1); ifi != NULL; ifi = ifi->ifi_next) { printf("%s\t",ifi->ifi_name); printf("%d\t",ifi->ifi_flags); if((ifi->ifi_addr)->sa_family!=AF_INET6) inet_ntop(AF_INET,&(((struct sockaddr_in *)(ifi->ifi_addr))->sin_addr),addr,sizeof(addr)); else inet_ntop(AF_INET6,&(((struct sockaddr_in6 *)(ifi->ifi_addr))->sin6_addr),addr,sizeof(addr)); printf("%s\t",addr);#ifdef SIOCGIFBRDADDR if ((ifi->ifi_flags & IFF_BROADCAST) && (ifi->ifi_addr)->sa_family!=AF_INET6) { inet_ntop(AF_INET,&(((struct sockaddr_in *) (ifi->ifi_brdaddr))->sin_addr),addr,sizeof(addr)); printf("%s\t",addr); }#endif printf("\n+++++++++++++++++++++++++++++++++++++++++++\n"); } return 0;} 这段代码输出如下：
[root@localhost net_if]./znet inet4
name flag IP broadcastaddr lo 73 127.0.0.1 ++++++++++++++++++++++++++++++ eth1 4099 192.168.1.2 192.168.1.255 ++++++++++++++++++++++++++++++ eth0 4163 192.168.125.99 192.168.125.255 ++++++++++++++++++++++++++++++ [root@localhost net_if]./znet inet6 name flag IP broadcastaddr lo 73 ::1 ++++++++++++++++++++++++++++++ eth1 4163 2001:250:1800:1::1 ++++++++++++++++++++++++++++++ eth0 4163 2001:250:1888:1::1
转载地址：http://cvfci.baihongyu.com/