Test getaddrinfo NAT64 synthesis on macOS

gaitest.c

#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <sys/socket.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <err.h>
 

int main(int argc, char *argv[]) {
    uint8_t ipv4[4] = {192, 0, 2, 1};
    struct addrinfo hints, *res, *res0;
    int error, s;
    const char *cause = NULL;

    char ipv4_str_buf[INET_ADDRSTRLEN] = { 0 };
    const char *ipv4_str = inet_ntop(AF_INET, &ipv4, ipv4_str_buf, sizeof(ipv4_str_buf));

    memset(&hints, 0, sizeof(hints));
    hints.ai_family = PF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_flags = AI_DEFAULT;
    error = getaddrinfo(ipv4_str, "http", &hints, &res0);
    if (error) {
        errx(1, "%s", gai_strerror(error));
        /*NOTREACHED*/
    }
    s = -1;
    for (res = res0; res; res = res->ai_next) {
	printf("family: %d, socktype: %d\n", res->ai_family, res->ai_socktype);
        s = socket(res->ai_family, res->ai_socktype,
                   res->ai_protocol);
        if (s < 0) {
            cause = "socket";
            continue;
        }
        char hbuf[NI_MAXHOST], sbuf[NI_MAXSERV];

        if (getnameinfo(res->ai_addr, res->ai_addrlen, hbuf, sizeof(hbuf), sbuf,
            sizeof(sbuf), NI_NUMERICHOST | NI_NUMERICSERV)) {
                errx(1, "could not get numeric hostname");
                /*NOTREACHED*/
        }
        printf("host=%s, serv=%s\n", hbuf, sbuf);

        if (connect(s, res->ai_addr, res->ai_addrlen) < 0) {
            cause = "connect";
            close(s);
            s = -1;
            continue;
        }
 
        break;  /* okay we got one */
    }
    if (s < 0) {
        err(1, "%s", cause);
        /*NOTREACHED*/
    }
    freeaddrinfo(res0);
}