From: Florian Weimer <fweimer@redhat.com>

Date: Tue, 21 Jan 2020 16:25:39 +0000 (+0100)

Subject: resolv: Enhance __resolv_conf_load to capture file change data

X-Git-Url: https://sourceware.org/git/?p=glibc.git;a=commitdiff_plain;h=dd0b4df329ff7ff2a656404db271c8ee8379ff9d

resolv: Enhance __resolv_conf_load to capture file change data

The data is captured after reading the file.  This allows callers

to check the change data against an earlier measurement.

Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>

---

diff --git a/resolv/res_init.c b/resolv/res_init.c

index 09345718cd..98d84f264d 100644

--- a/resolv/res_init.c

+++ b/resolv/res_init.c

@@ -103,6 +103,7 @@

 #include <inet/net-internal.h>

 #include <errno.h>

 #include <resolv_conf.h>

+#include <file_change_detection.h>

 static uint32_t net_mask (struct in_addr);

@@ -549,7 +550,8 @@ res_vinit_1 (FILE *fp, struct resolv_conf_parser *parser)

 }

 struct resolv_conf *

-__resolv_conf_load (struct __res_state *preinit)

+__resolv_conf_load (struct __res_state *preinit,

+                    struct file_change_detection *change)

 {

   /* Ensure that /etc/hosts.conf has been loaded (once).  */

   _res_hconf_init ();

@@ -577,7 +579,13 @@ __resolv_conf_load (struct __res_state *preinit)

   resolv_conf_parser_init (&parser, preinit);

   struct resolv_conf *conf = NULL;

-  if (res_vinit_1 (fp, &parser))

+  bool ok = res_vinit_1 (fp, &parser);

+  if (ok && change != NULL)

+    /* Update the file change information if the configuration was

+       loaded successfully.  */

+    ok = file_change_detection_for_fp (change, fp);

+

+  if (ok)

     {

       parser.template.nameserver_list

         = nameserver_list_begin (&parser.nameserver_list);

@@ -615,7 +623,7 @@ __res_vinit (res_state statp, int preinit)

   if (preinit && has_preinit_values (statp))

     /* For the preinit case, we cannot use the cached configuration

        because some settings could be different.  */

-    conf = __resolv_conf_load (statp);

+    conf = __resolv_conf_load (statp, NULL);

   else

     conf = __resolv_conf_get_current ();

   if (conf == NULL)

diff --git a/resolv/resolv_conf.c b/resolv/resolv_conf.c

index d954ba9a5a..bdd2ebb909 100644

--- a/resolv/resolv_conf.c

+++ b/resolv/resolv_conf.c

@@ -136,7 +136,7 @@ __resolv_conf_get_current (void)

     {

       /* Parse configuration while holding the lock.  This avoids

          duplicate work.  */

-      conf = __resolv_conf_load (NULL);

+      conf = __resolv_conf_load (NULL, NULL);

       if (conf != NULL)

         {

           if (global_copy->conf_current != NULL)

diff --git a/resolv/resolv_conf.h b/resolv/resolv_conf.h

index 01cbff9111..101e14bfe5 100644

--- a/resolv/resolv_conf.h

+++ b/resolv/resolv_conf.h

@@ -63,12 +63,16 @@ struct resolv_conf

    and the struct resolv_context facility.  */

 struct __res_state;

+struct file_change_detection;

 /* Read /etc/resolv.conf and return a configuration object, or NULL if

    /etc/resolv.conf cannot be read due to memory allocation errors.

-   If PREINIT is not NULL, some configuration values are taken from the

-   struct __res_state object.  */

-struct resolv_conf *__resolv_conf_load (struct __res_state *preinit)

+   If PREINIT is not NULL, some configuration values are taken from

+   the struct __res_state object.  If CHANGE is not null, file change

+   detection data is written to *CHANGE, based on the state of the

+   file after reading it.  */

+struct resolv_conf *__resolv_conf_load (struct __res_state *preinit,

+                                        struct file_change_detection *change)

   attribute_hidden __attribute__ ((warn_unused_result));

 /* Return a configuration object for the current /etc/resolv.conf