Use getifaddrs to obtain the IP address of the local network interface

getifaddrs Function is used to get the data on the local network card ip Address information , As shown below, we implement a tool class , And test and verify .

#include <string>
#include <vector>
#include <map>
#include <sys/socket.h>
#include <sys/types.h>
#include <netdb.h>
#include <ifaddrs.h>
#include <stdio.h>
#include <string.h>

struct IfaceIpInfo {
    
    std::string ifName;
    std::vector<std::string> ipv4;
    std::vector<std::string> ipv6;
};

class IpTool {
    
public:
    static bool FetchAllIpAddress(std::map<std::string, IfaceIpInfo> &local)
    {
    
        struct ifaddrs *ifaddr = nullptr;
        struct ifaddrs *ifa = nullptr;
        if (getifaddrs(&ifaddr) == -1) {
    
            printf("getifaddrs failed, %s", strerror(errno));
            return false;
        }
        for (ifa = ifaddr; ifa != nullptr; ifa = ifa->ifa_next) {
    
            if (ifa->ifa_addr == nullptr) {
    
                continue;
            }
            int family = ifa->ifa_addr->sa_family;
            if (family != AF_INET && family != AF_INET6) {
    
                continue;
            }
            char addr[NI_MAXHOST] = {
    0};
            int ret = getnameinfo(ifa->ifa_addr,
                (family == AF_INET) ? sizeof(struct sockaddr_in) : sizeof(struct sockaddr_in6),
                addr, NI_MAXHOST, nullptr, 0, NI_NUMERICHOST);
            if (ret != 0) {
    
                printf("getnameinfo() failed: %s\n", gai_strerror(ret));
                freeifaddrs(ifaddr);
                return false;
            }
            std::string ifName = ifa->ifa_name;
            std::map<std::string, IfaceIpInfo>::iterator iter = local.find(ifName);
            if (iter == local.end()) {
    
                IfaceIpInfo tmp;
                iter = local.emplace(ifName, tmp).first;
            }
            if (family == AF_INET) {
    
                iter->second.ipv4.push_back(addr);
            } else {
    
                /* For an IPv6 address, the suffix %wlan0 exists. */
                char *sepNum = strchr(addr, '%');
                if (sepNum != nullptr) {
    
                    *sepNum = '\0';
                }
                iter->second.ipv6.push_back(addr);
            }
        }
        freeifaddrs(ifaddr);
        return true;
    }
};

int main(void)
{
    
    std::map<std::string, IfaceIpInfo> local;
    if (!IpTool::FetchAllIpAddress(local)) {
    
        printf("fetch ip address failed!");
        return -1;
    }
    for (auto iter = local.begin(); iter != local.end(); ++iter) {
    
        printf("iface [%s]\n", iter->first.c_str());
        printf(" ipv4 address is [\n");
        for (auto it = iter->second.ipv4.begin(); it != iter->second.ipv4.end(); ++it) {
    
            printf(" %s\n", it->c_str());
        }
        printf("]\n ipv6 address is [\n");
        for (auto it = iter->second.ipv6.begin(); it != iter->second.ipv6.end(); ++it) {
    
            printf(" %s\n", it->c_str());
        }
        printf("]\n");
    }
    return 0;
}