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/* dnsmasq is Copyright (c) 2000-2024 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
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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 <http://www.gnu.org/licenses/>.
*/
#include "dnsmasq.h"
#ifdef HAVE_INOTIFY
#include <sys/inotify.h>
#include <sys/param.h> /* For MAXSYMLINKS */
/* the strategy is to set an 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)
/* If path is a symbolic link, return the path it
points to, made absolute if relative.
If path doesn't exist or is not a symlink, return NULL.
Return value is malloc'ed */
static char *my_readlink(char *path)
{
ssize_t rc, size = 64;
char *buf;
while (1)
{
buf = safe_malloc(size);
rc = readlink(path, buf, (size_t)size);
if (rc == -1)
{
/* Not link or doesn't exist. */
if (errno == EINVAL || errno == ENOENT)
{
free(buf);
return NULL;
}
else
die(_("cannot access path %s: %s"), path, EC_MISC);
}
else if (rc < size-1)
{
char *d;
buf[rc] = 0;
if (buf[0] != '/' && ((d = strrchr(path, '/'))))
{
/* Add path to relative link */
char *new_buf = safe_malloc((d - path) + strlen(buf) + 2);
*(d+1) = 0;
strcpy(new_buf, path);
strcat(new_buf, buf);
free(buf);
buf = new_buf;
}
return buf;
}
/* Buffer too small, increase and retry */
size += 64;
free(buf);
}
}
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);
if (daemon->port == 0 || option_bool(OPT_NO_RESOLV))
return;
for (res = daemon->resolv_files; res; res = res->next)
{
char *d, *new_path, *path = safe_malloc(strlen(res->name) + 1);
int links = MAXSYMLINKS;
strcpy(path, res->name);
/* Follow symlinks until we reach a non-symlink, or a non-existent file. */
while ((new_path = my_readlink(path)))
{
if (links-- == 0)
die(_("too many symlinks following %s"), res->name, EC_MISC);
free(path);
path = new_path;
}
res->wd = -1;
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);
}
}
static struct hostsfile *dyndir_addhosts(struct dyndir *dd, char *path)
{
/* Check if this file is already known in dd->files */
struct hostsfile *ah = NULL;
for(ah = dd->files; ah; ah = ah->next)
if(ah && ah->fname && strcmp(path, ah->fname) == 0)
return ah;
/* Not known, create new hostsfile record for this dyndir */
struct hostsfile *newah = NULL;
if(!(newah = whine_malloc(sizeof(struct hostsfile))))
return NULL;
/* Add this file to the tip of the linked list */
newah->next = dd->files;
dd->files = newah;
/* Copy flags, set index and the full file path */
newah->flags = dd->flags;
newah->index = daemon->host_index++;
newah->fname = path;
return newah;
}
/* initialisation for dynamic-dir. Set inotify watch for each directory, and read pre-existing files */
void set_dynamic_inotify(int flag, int total_size, struct crec **rhash, int revhashsz)
{
struct dyndir *dd;
for (dd = daemon->dynamic_dirs; dd; dd = dd->next)
{
DIR *dir_stream = NULL;
struct dirent *ent;
struct stat buf;
if (!(dd->flags & flag))
continue;
if (stat(dd->dname, &buf) == -1)
{
my_syslog(LOG_ERR, _("bad dynamic directory %s: %s"),
dd->dname, strerror(errno));
continue;
}
if (!(S_ISDIR(buf.st_mode)))
{
my_syslog(LOG_ERR, _("bad dynamic directory %s: %s"),
dd->dname, _("not a directory"));
continue;
}
if (!(dd->flags & AH_WD_DONE))
{
dd->wd = inotify_add_watch(daemon->inotifyfd, dd->dname, IN_CLOSE_WRITE | IN_MOVED_TO | IN_DELETE);
dd->flags |= AH_WD_DONE;
}
/* Read contents of dir _after_ calling add_watch, in the hope of avoiding
a race which misses files being added as we start */
if (dd->wd == -1 || !(dir_stream = opendir(dd->dname)))
{
my_syslog(LOG_ERR, _("failed to create inotify for %s: %s"),
dd->dname, strerror(errno));
continue;
}
while ((ent = readdir(dir_stream)))
{
size_t lendir = strlen(dd->dname);
size_t lenfile = strlen(ent->d_name);
char *path;
/* ignore emacs backups and dotfiles */
if (lenfile == 0 ||
ent->d_name[lenfile - 1] == '~' ||
(ent->d_name[0] == '#' && ent->d_name[lenfile - 1] == '#') ||
ent->d_name[0] == '.')
continue;
if ((path = whine_malloc(lendir + lenfile + 2)))
{
struct hostsfile *ah;
strcpy(path, dd->dname);
strcat(path, "/");
strcat(path, ent->d_name);
if (!(ah = dyndir_addhosts(dd, path)))
{
free(path);
continue;
}
/* ignore non-regular files */
if (stat(path, &buf) != -1 && S_ISREG(buf.st_mode))
{
if (dd->flags & AH_HOSTS)
total_size = read_hostsfile(path, ah->index, total_size, rhash, revhashsz);
#ifdef HAVE_DHCP
else if (dd->flags & (AH_DHCP_HST | AH_DHCP_OPT))
option_read_dynfile(path, dd->flags);
#endif
}
}
}
closedir(dir_stream);
}
}
int inotify_check(time_t now)
{
int hit = 0;
struct dyndir *dd;
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)
break;
for (p = inotify_buffer; rc - (p - inotify_buffer) >= (int)sizeof(struct inotify_event); p += sizeof(struct inotify_event) + in->len)
{
size_t namelen;
in = (struct inotify_event*)p;
/* ignore emacs backups and dotfiles */
if (in->len == 0 || (namelen = strlen(in->name)) == 0 ||
in->name[namelen - 1] == '~' ||
(in->name[0] == '#' && in->name[namelen - 1] == '#') ||
in->name[0] == '.')
continue;
for (res = daemon->resolv_files; res; res = res->next)
if (res->wd == in->wd && strcmp(res->file, in->name) == 0)
hit = 1;
for (dd = daemon->dynamic_dirs; dd; dd = dd->next)
if (dd->wd == in->wd)
{
size_t lendir = strlen(dd->dname);
char *path;
if ((path = whine_malloc(lendir + in->len + 2)))
{
struct hostsfile *ah = NULL;
strcpy(path, dd->dname);
strcat(path, "/");
strcat(path, in->name);
/* Is this is a deletion event? */
if (in->mask & IN_DELETE)
my_syslog(LOG_INFO, _("inotify: %s removed"), path);
else
my_syslog(LOG_INFO, _("inotify: %s new or modified"), path);
if (dd->flags & AH_HOSTS)
{
if ((ah = dyndir_addhosts(dd, path)))
{
const unsigned int removed = cache_remove_uid(ah->index);
if (removed > 0)
my_syslog(LOG_INFO, _("inotify: flushed %u names read from %s"), removed, path);
/* (Re-)load hostsfile only if this event isn't triggered by deletion */
if (!(in->mask & IN_DELETE))
read_hostsfile(path, ah->index, 0, NULL, 0);
#ifdef HAVE_DHCP
if (daemon->dhcp || daemon->doing_dhcp6)
{
/* Propagate the consequences of loading a new dhcp-host */
dhcp_update_configs(daemon->dhcp_conf);
lease_update_from_configs();
lease_update_file(now);
lease_update_dns(1);
}
#endif
}
}
#ifdef HAVE_DHCP
else if (dd->flags & AH_DHCP_HST)
{
if (option_read_dynfile(path, AH_DHCP_HST))
{
/* Propagate the consequences of loading a new dhcp-host */
dhcp_update_configs(daemon->dhcp_conf);
lease_update_from_configs();
lease_update_file(now);
lease_update_dns(1);
}
}
else if (dd->flags & AH_DHCP_OPT)
option_read_dynfile(path, AH_DHCP_OPT);
#endif
if (!ah)
free(path);
}
}
}
}
return hit;
}
#endif /* INOTIFY */