使用 getifaddrs函数获取Linux的IPV6地址

admin · 发表于 2023-5-23 14:59:38

getifaddrs()函数
头文件：
#include <sys/types.h>
#include <ifaddrs.h>
函数说明：获取本地网络接口的信息。在路由器上可以用这个接口来获取wan/lan等接口当前的ip地址，广播地址等信息。
int getifaddrs(struct ifaddrs **ifap);
getifaddrs创建一个链表，链表上的每个节点都是一个struct ifaddrs结构，getifaddrs()返回链表第一个元素的指针

返回值：成功返回0, 失败返回-1,同时errno会被赋允相应错误码。
事例：

#include <arpa/inet.h>
#include <sys/socket.h>
#include <netdb.h>
#include <ifaddrs.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <net/if.h>
int
main(int argc, char *argv[])
{
struct ifaddrs *ifaddr, *ifa;
int family, s;
char host[NI_MAXHOST];
if (getifaddrs(&ifaddr) == -1) {
perror("getifaddrs");
exit(EXIT_FAILURE);
}
/* Walk through linked list, maintaining head pointer so we
can free list later */
for (ifa = ifaddr; ifa != NULL; ifa = ifa->ifa_next) {
if (ifa->ifa_addr == NULL)
continue;
family = ifa->ifa_addr->sa_family;
/* Display interface name and family (including symbolic
form of the latter for the common families) */
printf("%s address family: %d%s\n",
ifa->ifa_name, family,
(family == AF_PACKET) ? " (AF_PACKET)" :
(family == AF_INET) ? " (AF_INET)" :
(family == AF_INET6) ? " (AF_INET6)" : "");
if (ifa->ifa_flags & IFF_BROADCAST)
/* For an AF_INET* interface address, display the address */
if (family == AF_INET || family == AF_INET6) {
s = getnameinfo(ifa->ifa_addr,
(family == AF_INET) ? sizeof(struct sockaddr_in) :
sizeof(struct sockaddr_in6),
host, NI_MAXHOST, NULL, 0, NI_NUMERICHOST);
if (s != 0) {
printf("getnameinfo() failed: %s\n", gai_strerror(s));
exit(EXIT_FAILURE);
}
printf("\taddress: <%s>\n", host);
if (ifa->ifa_flags & IFF_BROADCAST) {
s = getnameinfo(ifa->ifa_broadaddr,
(family == AF_INET) ? sizeof(struct sockaddr_in) :
sizeof(struct sockaddr_in6),
host, NI_MAXHOST, NULL, 0, NI_NUMERICHOST);
printf("\tbroadcast address: <%s>\n", host);
}
if (ifa->ifa_flags & IFF_POINTOPOINT) {
s = getnameinfo(ifa->ifa_dstaddr,
(family == AF_INET) ? sizeof(struct sockaddr_in) :
sizeof(struct sockaddr_in6),
host, NI_MAXHOST, NULL, 0, NI_NUMERICHOST);
printf("\tbroadcast address: <%s>\n", host);
}
}
}
freeifaddrs(ifaddr);
exit(EXIT_SUCCESS);
}

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struct ifaddrs结构体：

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 */
};

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ifa_next 指向链表中下一个struct ifaddr结构
ifa_name 网络接口名
ifa_flags 网络接口标志，这些标志见下面描述。
ifa_addr 指向一个包含网络地址的sockaddr结构
ifa_netmask 指向一个包含网络掩码的结构
ifu_broadaddr 如果(ifa_flags&IFF_BROADCAST)有效，ifu_broadaddr指向一个包含广播地址的结构。
ifu_dstaddr 如果(ifa_flags&IFF_POINTOPOINT)有效，ifu_dstaddr指向一个包含p2p目的地址的结构。
ifa_addr 指向一个缓冲区，其中包含地址族私有数据。没有私有数据则为NULL。

ifa_flags 标志位：
Device flags
IFF_UP Interface is running.
IFF_BROADCAST Valid broadcast address set.

IFF_DEBUG Internal debugging flag.
IFF_LOOPBACK Interface is a loopback interface.
IFF_POINTOPOINT Interface is a point-to-point link.
IFF_RUNNING Resources allocated.
IFF_NOARP No arp protocol, L2 destination address not
set.
IFF_PROMISC Interface is in promiscuous mode.
IFF_NOTRAILERS Avoid use of trailers.
IFF_ALLMULTI Receive all multicast packets.
IFF_MASTER Master of a load balancing bundle.
IFF_SLAVE Slave of a load balancing bundle.
IFF_MULTICAST Supports multicast
IFF_PORTSEL Is able to select media type via ifmap.
IFF_AUTOMEDIA Auto media selection active.
IFF_DYNAMIC The addresses are lost when the interface
goes down.
IFF_LOWER_UP Driver signals L1 up (since Linux 2.6.17)
IFF_DORMANT Driver signals dormant (since Linux 2.6.17)
IFF_ECHO Echo sent packets (since Linux 2.6.25)

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