utils.cpp

#include "utils.h"

#include <unistd.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <ifaddrs.h>

using namespace std;

string peer_ip(int fd){
    sockaddr_storage ss{};
    socklen_t sl = sizeof(ss);
    if (getpeername(fd, reinterpret_cast<sockaddr*>(&ss), &sl) == -1)
        ERR_THROW("getpeername");

    char ipstr[INET_ADDRSTRLEN];
    void* src = static_cast<void*>(&reinterpret_cast<sockaddr_in*>(&ss)->sin_addr);

    if (!inet_ntop(ss.ss_family, src, ipstr, sizeof(ipstr)))
        ERR_THROW("inet_ntop");
    return ipstr;
}

bool is_local_ipv4(const string& ip) {
    ifaddrs* ifaddr = nullptr;
    if (getifaddrs(&ifaddr) != 0) return false;

    bool found = false;
    for (ifaddrs* ifa = ifaddr; ifa != nullptr; ifa = ifa->ifa_next) {
        if (!ifa->ifa_addr) continue;
        if (ifa->ifa_addr->sa_family != AF_INET) continue;

        char buf[INET_ADDRSTRLEN];
        auto* sin = reinterpret_cast<sockaddr_in*>(ifa->ifa_addr);
        if (!inet_ntop(AF_INET, &sin->sin_addr, buf, sizeof(buf))) continue;

        if (ip == buf) {
            found = true;
            break; 
        }
    }
    freeifaddrs(ifaddr);
    return found;
}


int init_client(string server_ip, uint16_t server_port){
    int conn_fd;
    sockaddr_in serv_addr{}; // zeroed

    conn_fd = socket(AF_INET, SOCK_STREAM, 0);
    if(conn_fd<0)
        ERR_EXIT("socket");

    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(server_port);

    if(inet_pton(AF_INET, server_ip.c_str(), &serv_addr.sin_addr)<=0){
        close(conn_fd);
        ERR_EXIT("Invalid IP");
    }

    while(connect(conn_fd, reinterpret_cast<sockaddr*>(&serv_addr), sizeof(serv_addr))<0){
        if (errno == EINTR) continue;
        close(conn_fd);
        ERR_EXIT("connect");
    }

    fprintf(stderr, "Connected to %.80s:%d\n", server_ip.c_str(), server_port);
    return conn_fd;
}


int init_server(uint16_t &port){
    int listen_fd;
    sockaddr_in serv_addr{}; // zeroed

    listen_fd = socket(AF_INET, SOCK_STREAM, 0);
    if (listen_fd < 0) ERR_EXIT("socket");

    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = htonl(INADDR_ANY); // ANY == 0.0.0.0
    serv_addr.sin_port = htons(port);

    int tmp = 1;
    if (setsockopt(listen_fd, SOL_SOCKET, SO_REUSEADDR, (void*)&tmp, sizeof(tmp)) < 0) {
        close(listen_fd);
        ERR_EXIT("setsockopt");
    }
    if (bind(listen_fd, reinterpret_cast<sockaddr*>(&serv_addr), sizeof(serv_addr)) < 0) {
        close(listen_fd);
        ERR_EXIT("bind");
    }
    if (port==0){
        /* port == 0 -> let kernel choose the port */
        /* so we obtain the port kernel has chosen here */
        socklen_t slen = sizeof(serv_addr);
        if (getsockname(listen_fd, reinterpret_cast<sockaddr*>(&serv_addr), &slen) < 0){
            close(listen_fd);
            ERR_EXIT("getsockname");
        }
        port = ntohs(serv_addr.sin_port);
    }
    if (listen(listen_fd, MY_SOMAXCONN) < 0) {
        close(listen_fd);
        ERR_EXIT("listen");
    }

    fprintf(stderr, "Server listening on %.80s:%d\n", inet_ntoa(serv_addr.sin_addr), port);
    return listen_fd;
}