autofs-5.1.6 - improve sss getautomntent() error handling

From: Ian Kent <raven@themaw.net>

Recent versions of the sss autofs access library will return EHOSTDOWN
if the backend server is down.

The presence of this improvement in error handling is determined by an
added function to get the sss autofs protocol version.

Update the getautomntent() function to use this.

Also introduce a wait function so we can wait (for a while) for the host
to come back up.

Signed-off-by: Ian Kent <raven@themaw.net>
---
 CHANGELOG            |    1 
 modules/lookup_sss.c |  126 ++++++++++++++++++++++++++++++++++++++++++++++----
 2 files changed, 116 insertions(+), 11 deletions(-)

diff --git a/CHANGELOG b/CHANGELOG
index ecd54e9..434e23d 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -101,6 +101,7 @@ xx/xx/2018 autofs-5.1.5
 - refactor sss setautomntent().
 - improve sss setautomntent() error handling.
 - refactor sss getautomntent().
+- improve sss getautomntent() error handling.
 
 19/12/2017 autofs-5.1.4
 - fix spec file url.
diff --git a/modules/lookup_sss.c b/modules/lookup_sss.c
index 5addd87..f366b48 100644
--- a/modules/lookup_sss.c
+++ b/modules/lookup_sss.c
@@ -377,38 +377,136 @@ static int endautomntent(unsigned int logopt,
 	return ret;
 }
 
+static int getautomntent_wait(unsigned int logopt,
+			 struct lookup_context *ctxt,
+			 char **key, char **value, void *sss_ctxt)
+{
+	unsigned int retries;
+	unsigned int retry = 0;
+	int ret = 0;
+
+	retries = defaults_get_sss_master_map_wait();
+
+	/* Use the sss_master_map_wait configuration option
+	 * for the time to wait when reading a map too. If
+	 * it isn't set in the antofs configuration give it
+	 * a sensible value since we want to wait for a host
+	 * that's down in case it comes back up.
+	 */
+	if (retries <= 0) {
+		/* Protocol version 0 cant't tell us about
+		 * a host being down, return not found.
+		 */
+		if (proto_version(ctxt) == 0)
+			return ENOENT;
+		retries = 10;
+	}
+
+	warn(logopt,
+	 "can't contact sssd to to get map entry, retry for %d seconds",
+	 retries);
+
+	while (++retry <= retries) {
+		struct timespec t = { SSS_WAIT_INTERVAL, 0 };
+		struct timespec r;
+
+		ret = ctxt->getautomntent_r(key, value, sss_ctxt);
+		if (proto_version(ctxt) == 0) {
+			if (ret != ENOENT)
+				break;
+		} else {
+			if (ret != EHOSTDOWN)
+				break;
+		}
+
+		while (nanosleep(&t, &r) == -1 && errno == EINTR)
+			memcpy(&t, &r, sizeof(struct timespec));
+	}
+
+	if (!ret)
+		info(logopt,
+		     "successfully contacted sssd to get map entry");
+	else {
+		if (retry == retries)
+			ret = ETIMEDOUT;
+	}
+	return ret;
+}
+
 static int getautomntent(unsigned int logopt,
 			 struct lookup_context *ctxt,
 			 char **key, char **value, int count, void *sss_ctxt)
 {
 	char buf[MAX_ERR_BUF];
 	char *estr;
-	int ret = NSS_STATUS_UNAVAIL;
+	int err = NSS_STATUS_UNAVAIL;
+	int ret;
 
 	ret = ctxt->getautomntent_r(key, value, sss_ctxt);
 	if (ret) {
 		/* Host has gone down */
-		if (ret == ECONNREFUSED)
-			return NSS_STATUS_UNKNOWN;
-		if (ret != ENOENT)
+		if (ret == ECONNREFUSED) {
+			err = NSS_STATUS_UNKNOWN;
 			goto error;
-		if (!count) {
-			ret = NSS_STATUS_NOTFOUND;
+		}
+
+		if (proto_version(ctxt) == 0) {
+			if (ret != ENOENT)
+				goto error;
+			/* For prorocol version 0 ENOENT can only be
+			 * used to indicate we've read all entries.
+			 * So even if we haven't got any values yet we
+			 * can't use it to determine if we need to wait
+			 * on sss.
+			 */
+			err = NSS_STATUS_NOTFOUND;
+			if (count)
+				err = NSS_STATUS_SUCCESS;
 			goto free;
+		} else {
+			if (ret == ENOENT) {
+				err = NSS_STATUS_NOTFOUND;
+				if (count)
+					err = NSS_STATUS_SUCCESS;
+				goto free;
+			}
+			if (ret != EHOSTDOWN)
+				goto error;
+		}
+
+		ret = getautomntent_wait(logopt, ctxt,
+					 key, value, sss_ctxt);
+		if (ret) {
+			if (ret == ECONNREFUSED) {
+				err = NSS_STATUS_UNKNOWN;
+				goto free;
+			}
+			if (ret == ETIMEDOUT)
+				goto error;
+			if (ret == ENOENT) {
+				err = NSS_STATUS_NOTFOUND;
+				if (count)
+					err = NSS_STATUS_SUCCESS;
+				goto free;
+			}
+			goto error;
 		}
-		goto error;
 	}
-	return ret;
+	return NSS_STATUS_SUCCESS;
 
 error:
 	estr = strerror_r(ret, buf, MAX_ERR_BUF);
 	error(logopt, MODPREFIX "getautomntent: %s", estr);
 free:
-	if (*key)
+	if (*key) {
 		free(*key);
-	if (*value)
+		*key = NULL;
+	}
+	if (*value) {
 		free(*value);
-	return ret;
+		*value = NULL;
+	}
+	return err;
 }
 
 int lookup_read_master(struct master *master, time_t age, void *context)
@@ -439,6 +537,9 @@ int lookup_read_master(struct master *master, time_t age, void *context)
 			return ret;
 		}
 
+		if (!key || !value)
+			break;
+
 		count++;
 
 		buffer_len = strlen(key) + 1 + strlen(value) + 2;
@@ -523,6 +624,9 @@ int lookup_read_map(struct autofs_point *ap, time_t age, void *context)
 			return ret;
 		}
 
+		if (!key || !value)
+			break;
+
 		/*
 		 * Ignore keys beginning with '+' as plus map
 		 * inclusion is only valid in file maps.