nfs-server-generator: avoid using external services.

nfs-server-generator is run very early when a lot of services are not yet started, so it mustn't depend on them. Currently it can try to use hostname lookup and syslog.

Hostname-lookup is not needed, as we don't use the host issue, and sending message to stderr is sufficient for the generator.

Disabling syslog is easy - call a function that sets a static variable.

Disabling hostname lookup isn't quite so easy, so add a static variable which can be set to disable it.

Signed-off-by NeilBrown <[email protected]>

---

hi,
I contemplated passing another arg to export_read() and export_d_read() to resolve this, but it didn't seem worth it.

Is this approach OK to people?

Thanks,
NeilBrown

 support/export/export.c        | 12 ++++++++++--
 support/include/exportfs.h     |  1 +
 systemd/nfs-server-generator.c |  4 ++++
 3 files changed, 15 insertions(+), 2 deletions(-)

support/export/export.c +0 -0

index 0b8a858c2c74..c65dc8807a4e 100644

support/export/export.c +10 -2

+static int assume_canonical = 0;
+
+void
+export_avoid_host_lookup(int i)
+{
+	assume_canonical = i;
+}
+
 /**
  * export_read - read entries from /etc/exports
  * @fname: name of file to read from

@@ -83,9 +91,9 @@ export_read(char *fname)
 
 	setexportent(fname, "r");
 	while ((eep = getexportent(0,1)) != NULL) {
-		exp = export_lookup(eep->e_hostname, eep->e_path, 0);
+		exp = export_lookup(eep->e_hostname, eep->e_path, assume_canonical);
 		if (!exp) {
-			if (export_create(eep, 0))
+			if (export_create(eep, assume_canonical))
 				/* possible complaints already logged */
 				volumes++;
 		}

support/include/exportfs.h +1 -0

index f033329b5fd2..ba45b2dee199 100644
@@ -134,6 +134,7 @@ struct addrinfo *		client_resolve(const struct sockaddr *sap);
 int 				client_member(const char *client,
 						const char *name);
 
+void				export_avoid_host_lookup(int i);
 int				export_read(char *fname);
 int				export_d_read(const char *dname);
 void				export_reset(nfs_export *);

systemd/nfs-server-generator.c +4 -0

index af8bb52bfbd7..7ae6dd1c4b20 100644
@@ -93,6 +93,10 @@ int main(int argc, char *argv[])
 	FILE		*f, *fstab;
 	struct mntent	*mnt;
 
+	/* Avoid using any external services */
+	xlog_syslog(0);
+	export_avoid_host_lookup(1);
+
 	if (argc != 4 || argv[1][0] != '/') {
 		fprintf(stderr, "nfs-server-generator: create systemd dependencies for nfs-server\n");
 		fprintf(stderr, "Usage: normal-dir early-dir late-dir\n");

Hello,

Quoted 20 lines · NeilBrown

nfs-server-generator is run very early when a lot of services are not yet started, so it mustn't depend on them. Currently it can try to use hostname lookup and syslog.

Hostname-lookup is not needed, as we don't use the host issue, and sending message to stderr is sufficient for the generator.

Disabling syslog is easy - call a function that sets a static variable.

Disabling hostname lookup isn't quite so easy, so add a static variable which can be set to disable it.

Signed-off-by NeilBrown <[email protected]>

---

hi,
I contemplated passing another arg to export_read() and export_d_read() to resolve this, but it didn't seem worth it.

Quoted 1 line

Is this approach OK to people?

It's not the most eloquent interface I've ever seen... ;-)

What are the failures this is fixing? When a hostname lookup is done what happens? Failure hangs stopping the server from coming up?

Quoted 12 lines

Thanks,
NeilBrown

 support/export/export.c        | 12 ++++++++++--
 support/include/exportfs.h     |  1 +
 systemd/nfs-server-generator.c |  4 ++++
 3 files changed, 15 insertions(+), 2 deletions(-)

support/export/export.c static void warn_duplicated_exports(nfs_export *exp, struct exportent *eep) · line 68

Quoted 7 lines

support/export/export.c +0 -0

index 0b8a858c2c74..c65dc8807a4e 100644
@@ -67,6 +67,14 @@ static void warn_duplicated_exports(nfs_export *exp, struct exportent *eep)
 	}
 }

If we do have to stay with this approach, I definitely think comment explaining why its needed and what it does.

Finally, on an unrelated issue I'm seeing SELinux preventing nfs-server-generator from accessing nfs-server.service.d/order-with-mounts.conf because of a labeling issue. I guess the label should be nfsd_unit_file_t not systemd_unit_file_t

Quoted 23 lines · Steve Dickson

Hello,

Quoted 20 lines · NeilBrown

nfs-server-generator is run very early when a lot of services are not yet started, so it mustn't depend on them. Currently it can try to use hostname lookup and syslog.

Hostname-lookup is not needed, as we don't use the host issue, and sending message to stderr is sufficient for the generator.

Disabling syslog is easy - call a function that sets a static variable.

Disabling hostname lookup isn't quite so easy, so add a static variable which can be set to disable it.

Signed-off-by NeilBrown <[email protected]>

---

hi,
I contemplated passing another arg to export_read() and export_d_read() to resolve this, but it didn't seem worth it.

Quoted 7 lines

Quoted 1 line

Is this approach OK to people?

It's not the most eloquent interface I've ever seen... ;-)

What are the failures this is fixing? When a hostname lookup is done what happens? Failure hangs stopping the server from coming up?

I never actually reproduced it myself, but I think that when hostname lookup failed (possibly after a timeout) it tried to log an error via syslog and writing to syslog blocked indefinitely.
The systemd.generator manpage explicitly rules out trying to talk to syslog.

Quoted 14 lines

Quoted 14 lines

Thanks,
NeilBrown

 support/export/export.c        | 12 ++++++++++--
 support/include/exportfs.h     |  1 +
 systemd/nfs-server-generator.c |  4 ++++
 3 files changed, 15 insertions(+), 2 deletions(-)

Quoted 10 lines

support/export/export.c static void warn_duplicated_exports(nfs_export *exp, struct exportent *eep) · line 68

Quoted 7 lines

support/export/export.c +0 -0

index 0b8a858c2c74..c65dc8807a4e 100644
@@ -67,6 +67,14 @@ static void warn_duplicated_exports(nfs_export *exp, struct exportent *eep)
 	}
 }

If we do have to stay with this approach, I definitely think comment explaining why its needed and what it does.

That's sensible. I'll resend with some nice friendly comments.

Quoted 7 lines

Finally, on an unrelated issue I'm seeing SELinux preventing nfs-server-generator from accessing nfs-server.service.d/order-with-mounts.conf because of a labeling issue. I guess the label should be nfsd_unit_file_t not systemd_unit_file_t

I wouldn't know about that :-(

Thanks,
NeilBrown

nfs-server-generator is run very early when a lot of services are not yet started, so it mustn't depend on them. Currently it can try to use hostname lookup and syslog. Using hostname lookup can cause errors and when these are logged via syslog, it can cause the generator to block indefinitely

Hostname-lookup is not needed, as we don't use the host issue, and sending message to stderr is sufficient for the generator.

Disabling syslog is easy - call a function that sets a static variable.

Disabling hostname lookup requires adding an "ignore_hosts" flags to export_read and export_d_read().

Signed-off-by NeilBrown <[email protected]>

---

Hi Steve,
I decided that you were right and the interface wasn't really very nice.
And it wasn't that hard to make a more sensible interface. So I did that. Less need for comments, but I put an appropriate comment in anyway.

Thanks,
NeilBrown

 support/export/export.c        | 13 +++++++++----
 support/include/exportfs.h     |  4 ++--
 systemd/nfs-server-generator.c |  4 ++--
 utils/exportfs/exportfs.c      |  4 ++--
 4 files changed, 15 insertions(+), 10 deletions(-)

support/export/export.c +9 -4

index 0b8a858c2c74..15e91cb3eb71 100644
@@ -70,11 +70,15 @@ static void warn_duplicated_exports(nfs_export *exp, struct exportent *eep)
 /**
  * export_read - read entries from /etc/exports
  * @fname: name of file to read from
+ * @ignore_hosts: don't check validity of host names
  *
  * Returns number of read entries.
+ * @ignore_hosts can be set when the host names won't be used
+ * and when getting delays or errors due to problems with
+ * hostname looking is not acceptable.
  */
 int
-export_read(char *fname)
+export_read(char *fname, int ignore_hosts)
 {
 	struct exportent	*eep;
 	nfs_export		*exp;

@@ -83,7 +87,7 @@ export_read(char *fname)
 
 	setexportent(fname, "r");
 	while ((eep = getexportent(0,1)) != NULL) {
-		exp = export_lookup(eep->e_hostname, eep->e_path, 0);
+		exp = export_lookup(eep->e_hostname, eep->e_path, ignore_hosts);
 		if (!exp) {
 			if (export_create(eep, 0))
 				/* possible complaints already logged */

@@ -100,13 +104,14 @@ export_read(char *fname)
 /**
  * export_d_read - read entries from /etc/exports.
  * @fname: name of directory to read from
+ * @ignore_hosts: don't check validity of host names
  *
  * Returns number of read entries.
  * Based on mnt_table_parse_dir() in
  *  util-linux-ng/shlibs/mount/src/tab_parse.c
  */
 int
-export_d_read(const char *dname)
+export_d_read(const char *dname, int ignore_hosts)
 {
 	int n = 0, i;
 	struct dirent **namelist = NULL;

@@ -150,7 +155,7 @@ export_d_read(const char *dname)
 			continue;
 		}
 
-		volumes += export_read(fname);
+		volumes += export_read(fname, ignore_hosts);
 	}
 
 	for (i = 0; i < n; i++)

support/include/exportfs.h +2 -2

index f033329b5fd2..32d4fe95fd7e 100644
@@ -134,8 +134,8 @@ struct addrinfo *		client_resolve(const struct sockaddr *sap);
 int 				client_member(const char *client,
 						const char *name);
 
-int				export_read(char *fname);
-int				export_d_read(const char *dname);
+int				export_read(char *fname, int ignore_hosts);
+int				export_d_read(const char *dname, int ignore_hosts);
 void				export_reset(nfs_export *);
 nfs_export *			export_lookup(char *hname, char *path, int caconical);
 nfs_export *			export_find(const struct addrinfo *ai,

systemd/nfs-server-generator.c +2 -2

index af8bb52bfbd7..44895f1f8582 100644
@@ -102,8 +102,8 @@ int main(int argc, char *argv[])
 	path = malloc(strlen(argv[1]) + sizeof(dirbase) + sizeof(filebase));
 	if (!path)
 		exit(2);
-	if (export_read(_PATH_EXPORTS) +
-	    export_d_read(_PATH_EXPORTS_D) == 0)
+	if (export_read(_PATH_EXPORTS, 1) +
+	    export_d_read(_PATH_EXPORTS_D, 1) == 0)
 		/* Nothing is exported, so nothing to do */
 		exit(0);
 

utils/exportfs/exportfs.c +2 -2

index 4ac2c15ae13e..5136810029d0 100644
@@ -183,8 +183,8 @@ main(int argc, char **argv)
 	atexit(release_lockfile);
 
 	if (f_export && ! f_ignore) {
-		if (! (export_read(_PATH_EXPORTS) +
-		       export_d_read(_PATH_EXPORTS_D))) {
+		if (! (export_read(_PATH_EXPORTS, 0) +
+		       export_d_read(_PATH_EXPORTS_D, 0))) {
 			if (f_verbose)
 				xlog(L_WARNING, "No file systems exported!");
 		}