blob: 960bf5efb41f70786096800f043af58f3b3f3afc [file] [log] [blame]
/* dnsmasq is Copyright (c) 2000-2014 Simon Kelley
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 dated June, 1991, or
(at your option) version 3 dated 29 June, 2007.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <>.
#include "dnsmasq.h"
#include <sys/inotify.h>
/* the strategy is to set a inotify on the directories containing
resolv files, for any files in the directory which are close-write
or moved into the directory.
When either of those happen, we look to see if the file involved
is actually a resolv-file, and if so, call poll-resolv with
the "force" argument, to ensure it's read.
This adds one new error condition: the directories containing
all specified resolv-files must exist at start-up, even if the actual
files don't.
static char *inotify_buffer;
#define INOTIFY_SZ (sizeof(struct inotify_event) + NAME_MAX + 1)
void inotify_dnsmasq_init()
struct resolvc *res;
inotify_buffer = safe_malloc(INOTIFY_SZ);
daemon->inotifyfd = inotify_init1(IN_NONBLOCK | IN_CLOEXEC);
if (daemon->inotifyfd == -1)
die(_("failed to create inotify: %s"), NULL, EC_MISC);
for (res = daemon->resolv_files; res; res = res->next)
char *d = NULL, *path;
if (!(path = realpath(res->name, NULL)))
/* realpath will fail if the file doesn't exist, but
dnsmasq copes with missing files, so fall back
and assume that symlinks are not in use in that case. */
if (errno == ENOENT)
path = res->name;
die(_("cannot cannonicalise resolv-file %s: %s"), res->name, EC_MISC);
if ((d = strrchr(path, '/')))
*d = 0; /* make path just directory */
res->wd = inotify_add_watch(daemon->inotifyfd, path, IN_CLOSE_WRITE | IN_MOVED_TO);
res->file = d+1; /* pointer to filename */
*d = '/';
if (res->wd == -1 && errno == ENOENT)
die(_("directory %s for resolv-file is missing, cannot poll"), res->name, EC_MISC);
if (res->wd == -1)
die(_("failed to create inotify for %s: %s"), res->name, EC_MISC);
int inotify_check(void)
int hit = 0;
while (1)
int rc;
char *p;
struct resolvc *res;
struct inotify_event *in;
while ((rc = read(daemon->inotifyfd, inotify_buffer, INOTIFY_SZ)) == -1 && errno == EINTR);
if (rc <= 0)
for (p = inotify_buffer; rc - (p - inotify_buffer) >= (int)sizeof(struct inotify_event); p += sizeof(struct inotify_event) + in->len)
in = (struct inotify_event*)p;
for (res = daemon->resolv_files; res; res = res->next)
if (res->wd == in->wd && in->len != 0 && strcmp(res->file, in->name) == 0)
hit = 1;
return hit;