autofs-5.1.6 - improve sss getautomntbyname() 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 getautomntbyname() 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 |  106 ++++++++++++++++++++++++++++++++++++++++++++------
 2 files changed, 95 insertions(+), 12 deletions(-)

diff --git a/CHANGELOG b/CHANGELOG
index 8b662d7..309def2 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -107,6 +107,7 @@ xx/xx/2018 autofs-5.1.5
 - sss introduce a flag to indicate map being read.
 - update sss timeout documentation.
 - refactor sss getautomntbyname().
+- improve sss getautomntbyname() 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 1a56ea1..70efc11 100644
--- a/modules/lookup_sss.c
+++ b/modules/lookup_sss.c
@@ -566,27 +566,106 @@ free:
 	return err;
 }
 
+static int getautomntbyname_wait(unsigned int logopt,
+			 struct lookup_context *ctxt,
+			 char *key, char **value, void *sss_ctxt,
+			 unsigned int flags)
+{
+	unsigned int retries;
+	unsigned int retry = 0;
+	int ret = 0;
+
+	retries = calculate_retry_count(ctxt, flags);
+	if (retries == 0) {
+		if (proto_version(ctxt) == 0)
+			return EINVAL;
+		return ENOENT;
+	}
+
+	warn(logopt,
+	"can't contact sssd to to lookup key value, retry for %d seconds",
+	retries);
+
+	while (++retry <= retries) {
+		struct timespec t = { SSS_WAIT_INTERVAL, 0 };
+		struct timespec r;
+
+		ret = ctxt->getautomntbyname_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 lookup key value");
+	else {
+		if (proto_version(ctxt) == 0 && retry > retries)
+			ret = ETIMEDOUT;
+	}
+	return ret;
+}
+
 static int getautomntbyname(unsigned int logopt,
 			    struct lookup_context *ctxt,
-			    char *key, char **value, void *sss_ctxt)
+			    char *key, char **value, void *sss_ctxt,
+			    unsigned int flags)
 {
 	char buf[MAX_ERR_BUF];
 	char *estr;
-	int ret = NSS_STATUS_UNAVAIL;
+	int err = NSS_STATUS_UNAVAIL;
+	int ret;
 
 	ret = ctxt->getautomntbyname_r(key, value, sss_ctxt);
 	if (ret) {
 		/* Host has gone down */
 		if (ret == ECONNREFUSED)
-			return NSS_STATUS_UNKNOWN;
-
-		if (ret != ENOENT)
 			goto error;
 
-		ret = NSS_STATUS_NOTFOUND;
-		goto free;
+		if (proto_version(ctxt) == 0) {
+			if (ret != ENOENT)
+				goto error;
+			/* For prorocol version 0 ENOENT can only be
+			 * used to indicate no entry was found. So it
+			 * can't be used to determine if we need to wait
+			 * on sss.
+			 */
+			err = NSS_STATUS_NOTFOUND;
+			goto free;
+		} else {
+			if (ret == ENOENT) {
+				err = NSS_STATUS_NOTFOUND;
+				goto free;
+			}
+			if (ret != EHOSTDOWN)
+				goto error;
+		}
+
+		ret = getautomntbyname_wait(logopt, ctxt,
+					    key, value, sss_ctxt, flags);
+		if (ret) {
+			if (ret == ECONNREFUSED)
+				goto free;
+			if (ret == ETIMEDOUT)
+				goto error;
+			/* sss proto version 0 and sss timeout not set */
+			if (ret == EINVAL)
+				goto free;
+			if (ret == ENOENT) {
+				err = NSS_STATUS_NOTFOUND;
+				goto free;
+			}
+			goto error;
+		}
 	}
-	return ret;
+	return NSS_STATUS_SUCCESS;
 
 error:
 	estr = strerror_r(ret, buf, MAX_ERR_BUF);
@@ -596,7 +675,7 @@ free:
 		free(*value);
 		*value = NULL;
 	}
-	return ret;
+	return err;
 }
 
 int lookup_read_master(struct master *master, time_t age, void *context)
@@ -802,7 +881,8 @@ static int lookup_one(struct autofs_point *ap,
 	if (ret)
 		return ret;
 
-	ret = getautomntbyname(ap->logopt, ctxt, qKey, &value, sss_ctxt);
+	ret = getautomntbyname(ap->logopt, ctxt,
+			       qKey, &value, sss_ctxt, SSS_LOOKUP_KEY);
 	if (ret == NSS_STATUS_NOTFOUND)
 		goto wild;
 	if (ret) {
@@ -829,13 +909,15 @@ static int lookup_one(struct autofs_point *ap,
 	return NSS_STATUS_SUCCESS;
 
 wild:
-	ret = getautomntbyname(ap->logopt, ctxt, "/", &value, sss_ctxt);
+	ret = getautomntbyname(ap->logopt, ctxt,
+			       "/", &value, sss_ctxt, SSS_LOOKUP_KEY);
 	if (ret) {
 		if (ret != NSS_STATUS_NOTFOUND) {
 			endautomntent(ap->logopt, ctxt, &sss_ctxt);
 			return ret;
 		}
-		ret = getautomntbyname(ap->logopt, ctxt, "*", &value, sss_ctxt);
+		ret = getautomntbyname(ap->logopt, ctxt,
+				       "*", &value, sss_ctxt, SSS_LOOKUP_KEY);
 		if (ret && ret != NSS_STATUS_NOTFOUND) {
 			endautomntent(ap->logopt, ctxt, &sss_ctxt);
 			return ret;