pfclientのログを黙らせ、NTP問い合わせをNICTに変更

pfnull.c

/*
 $ gcc -Wall -fPIC -shared -o pfnull.so pfnull.c -ldl
 export LD_PRELOAD=/usr/local/lib/pfnull.so
*/

#define _GNU_SOURCE
#include <stdio.h>
#include <dlfcn.h>
#include <stdarg.h>
#include <string.h>
#include <errno.h>

#include <netdb.h>
#include <arpa/inet.h>

FILE *fopen(const char *pathname, const char *mode) {
    static FILE *(*original_fopen)(const char *, const char *) = NULL;
    if (!original_fopen) {
        original_fopen = dlsym(RTLD_NEXT, "fopen");
    }

    if (pathname != NULL && strstr(pathname, "pfclient-log") != NULL) {
        //fprintf(stderr, "[FAKE ERROR] Simulating Disk Full (ENOSPC) for: %s\n", pathname);
        errno = ENOSPC;
        return NULL;
    }

    return original_fopen(pathname, mode);
}

int getaddrinfo(const char *node, const char *service,
                const struct addrinfo *hints,
                struct addrinfo **res) {
    static int (*original_getaddrinfo)(const char *, const char *,
                                       const struct addrinfo *,
                                       struct addrinfo **) = NULL;

    if (!original_getaddrinfo) {
        original_getaddrinfo = dlsym(RTLD_NEXT, "getaddrinfo");
    }

    const char *final_node = node;

    if (node != NULL && strstr(node, ".planefinder.pool.ntp.org") != NULL) {
        if (service != NULL && strcmp(service, "123") == 0) {
            final_node = "ntp.nict.jp";
        }
    }

    return original_getaddrinfo(final_node, service, hints, res);
}