src/inotify.c - thekelleys/dnsmasq - Gitiles

 /* dnsmasq is Copyright (c) 2000-2021 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 (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);

     }
 }


 /* 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 hostsfile *ah;

   for (ah = daemon->dynamic_dirs; ah; ah = ah->next)
     {
       DIR *dir_stream = NULL;
       struct dirent *ent;
       struct stat buf;

       if (!(ah->flags & flag))
 	continue;

       if (stat(ah->fname, &buf) == -1 || !(S_ISDIR(buf.st_mode)))
 	{
 	  my_syslog(LOG_ERR, _("bad dynamic directory %s: %s"),
 		    ah->fname, strerror(errno));
 	  continue;
 	}

        if (!(ah->flags & AH_WD_DONE))
 	 {
 	   ah->wd = inotify_add_watch(daemon->inotifyfd, ah->fname, IN_CLOSE_WRITE | IN_MOVED_TO);
 	   ah->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 (ah->wd == -1 || !(dir_stream = opendir(ah->fname)))
 	 {
 	   my_syslog(LOG_ERR, _("failed to create inotify for %s: %s"),
 		     ah->fname, strerror(errno));
 	   continue;
 	 }

        while ((ent = readdir(dir_stream)))
 	 {
 	   size_t lendir = strlen(ah->fname);
 	   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)))
 	     {
 	       strcpy(path, ah->fname);
 	       strcat(path, "/");
 	       strcat(path, ent->d_name);

 	       /* ignore non-regular files */
 	       if (stat(path, &buf) != -1 && S_ISREG(buf.st_mode))
 		 {
 		   if (ah->flags & AH_HOSTS)
 		     total_size = read_hostsfile(path, ah->index, total_size, rhash, revhashsz);
 #ifdef HAVE_DHCP
 		   else if (ah->flags & (AH_DHCP_HST | AH_DHCP_OPT))
 		     option_read_dynfile(path, ah->flags);
 #endif
 		 }

 	       free(path);
 	     }
 	 }

        closedir(dir_stream);
     }
 }

 int inotify_check(time_t now)
 {
   int hit = 0;
   struct hostsfile *ah;

   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 (ah = daemon->dynamic_dirs; ah; ah = ah->next)
 	    if (ah->wd == in->wd)
 	      {
 		size_t lendir = strlen(ah->fname);
 		char *path;

 		if ((path = whine_malloc(lendir + in->len + 2)))
 		  {
 		    strcpy(path, ah->fname);
 		    strcat(path, "/");
 		    strcat(path, in->name);

 		    my_syslog(LOG_INFO, _("inotify, new or changed file %s"), path);

 		    if (ah->flags & AH_HOSTS)
 		      {
 			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 (ah->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 (ah->flags & AH_DHCP_OPT)
 		      option_read_dynfile(path, AH_DHCP_OPT);
 #endif

 		    free(path);
 		  }
 	      }
 	}
     }
   return hit;
 }

 #endif  /* INOTIFY */
	/* dnsmasq is Copyright (c) 2000-2021 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 (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);

	}
	}


	/* 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 hostsfile *ah;

	for (ah = daemon->dynamic_dirs; ah; ah = ah->next)
	{
	DIR *dir_stream = NULL;
	struct dirent *ent;
	struct stat buf;

	if (!(ah->flags & flag))
	continue;

	if (stat(ah->fname, &buf) == -1 \|\| !(S_ISDIR(buf.st_mode)))
	{
	my_syslog(LOG_ERR, _("bad dynamic directory %s: %s"),
	ah->fname, strerror(errno));
	continue;
	}

	if (!(ah->flags & AH_WD_DONE))
	{
	ah->wd = inotify_add_watch(daemon->inotifyfd, ah->fname, IN_CLOSE_WRITE \| IN_MOVED_TO);
	ah->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 (ah->wd == -1 \|\| !(dir_stream = opendir(ah->fname)))
	{
	my_syslog(LOG_ERR, _("failed to create inotify for %s: %s"),
	ah->fname, strerror(errno));
	continue;
	}

	while ((ent = readdir(dir_stream)))
	{
	size_t lendir = strlen(ah->fname);
	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)))
	{
	strcpy(path, ah->fname);
	strcat(path, "/");
	strcat(path, ent->d_name);

	/* ignore non-regular files */
	if (stat(path, &buf) != -1 && S_ISREG(buf.st_mode))
	{
	if (ah->flags & AH_HOSTS)
	total_size = read_hostsfile(path, ah->index, total_size, rhash, revhashsz);
	#ifdef HAVE_DHCP
	else if (ah->flags & (AH_DHCP_HST \| AH_DHCP_OPT))
	option_read_dynfile(path, ah->flags);
	#endif
	}

	free(path);
	}
	}

	closedir(dir_stream);
	}
	}

	int inotify_check(time_t now)
	{
	int hit = 0;
	struct hostsfile *ah;

	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 (ah = daemon->dynamic_dirs; ah; ah = ah->next)
	if (ah->wd == in->wd)
	{
	size_t lendir = strlen(ah->fname);
	char *path;

	if ((path = whine_malloc(lendir + in->len + 2)))
	{
	strcpy(path, ah->fname);
	strcat(path, "/");
	strcat(path, in->name);

	my_syslog(LOG_INFO, _("inotify, new or changed file %s"), path);

	if (ah->flags & AH_HOSTS)
	{
	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 (ah->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 (ah->flags & AH_DHCP_OPT)
	option_read_dynfile(path, AH_DHCP_OPT);
	#endif

	free(path);
	}
	}
	}
	}
	return hit;
	}

	#endif /* INOTIFY */