[3/3] discover/pxe-parser: Retrieve configs asynchronously
diff mbox

Message ID 20160609045909.17049-3-sam@mendozajonas.com
State Superseded
Headers show

Commit Message

samjonas June 9, 2016, 4:59 a.m. UTC
Depending on the configuration of the DHCP server and the network, tftp
requests made by the pxe parser can timeout. The pxe parser makes these
requests synchronously so several timeouts can block the server
completely for several minutes, leaving the server unresponsive to UI
requests.

Rework the pxe parser such that it handles the result of each tftp
request in a callback, which can complete after iterate_parsers() has
returned. A discover_context and conf_context are cloned for each
request so that the callbacks can handle new boot options even after the
iterate loop has completed.

Signed-off-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>
---
 discover/pxe-parser.c | 171 ++++++++++++++++++++++++++++++++++++++------------
 lib/url/url.c         |   2 +-
 lib/url/url.h         |   1 +
 3 files changed, 132 insertions(+), 42 deletions(-)

Patch
diff mbox

diff --git a/discover/pxe-parser.c b/discover/pxe-parser.c
index 4812c37..9e880b2 100644
--- a/discover/pxe-parser.c
+++ b/discover/pxe-parser.c
@@ -8,6 +8,7 @@ 
 #include <talloc/talloc.h>
 #include <url/url.h>
 #include <log/log.h>
+#include <file/file.h>
 
 #include "parser.h"
 #include "parser-conf.h"
@@ -197,87 +198,175 @@  static void pxe_process_pair(struct conf_context *ctx,
 
 }
 
-static int pxe_parse(struct discover_context *dc)
+/*
+ * Callback for asynchronous loads from pxe_parse()
+ * @param result Result of load_url_async()
+ * @param data   Pointer to associated conf_context
+ */
+static void pxe_conf_parse_cb(struct load_url_result *result, void *data)
 {
-	struct pb_url *pxe_base_url, *url;
-	struct pxe_parser_info *parser_info;
-	char **pxe_conf_files, **filename;
-	struct conf_context *conf;
-	bool complete_url;
+	struct conf_context *conf = data;
+	struct device_handler *handler;
+	struct boot_status status = {0};
+	char *buf = NULL;
 	int len, rc;
-	char *buf;
 
-	/* Expects dhcp event parameters to support network boot */
-	if (!dc->event)
-		return -1;
+	if (!data || !result || result->status != LOAD_OK)
+		return;
+
+	rc = read_file(conf, result->local, &buf, &len);
+	if (rc) {
+		pb_log("Read failed during pxe callback for %s\n", result->local);
+		goto out_clean;
+	}
+
+	conf_parse_buf(conf, buf, len);
+
+	/* We may be called well after the original caller of iterate_parsers(),
+	 * commit any new boot options ourselves */
+	handler = talloc_parent(conf);
+	device_handler_discover_context_commit(handler, conf->dc);
 
-	conf = talloc_zero(dc, struct conf_context);
+	status.type = BOOT_STATUS_INFO;
+	status.message = talloc_asprintf(conf, "pxe: parsed config for %s",
+					conf->dc->conf_url->host);
+	device_handler_boot_status(handler, &status);
+
+	talloc_free(buf);
+out_clean:
+	if (result->cleanup_local)
+		unlink(result->local);
+	talloc_free(conf);
+}
+
+/**
+ * Return a new conf_context and copy an existing discover_context under the
+ * same talloc context.
+ * @param  ctx  Parent talloc context
+ * @param  orig Original discover_context to copy
+ * @return      Pointer to new conf_context
+ */
+static struct conf_context *copy_context(void *ctx,
+					   struct discover_context *orig)
+{
+	struct conf_context *conf;
+	struct discover_context *dc;
+	struct pxe_parser_info *info;
+
+	conf = talloc_zero(ctx, struct conf_context);
 
 	if (!conf)
-		goto out;
+		return NULL;
 
-	conf->dc = dc;
 	conf->get_pair = conf_get_pair_space;
 	conf->process_pair = pxe_process_pair;
 	conf->finish = pxe_finish;
+	info = talloc_zero(conf, struct pxe_parser_info);
+	conf->parser_info = info;
+
+	/*
+	 * Small workaround for the test suite; pxe tests will call
+	 * check_boot_option_count() which counts boot_options held by the
+	 * discover_context, not the device_handler. Since the test suite will
+	 * perform the pxe tests synchronously, just hold on to the original
+	 * discover_context
+	 */
+#ifdef PETITBOOT_TEST
+	conf->dc = orig;
+	return conf;
+#endif
+
+	dc = talloc(conf, struct discover_context);
+	dc->device = orig->device;
+	dc->network = orig->network;
+	dc->event = orig->event;
+	dc->test_data = orig->test_data;
+	dc->conf_url = pb_url_copy(dc, orig->conf_url);
+	list_init(&dc->boot_options);
 
-	parser_info = talloc_zero(conf, struct pxe_parser_info);
-	conf->parser_info = parser_info;
+	conf->dc = dc;
+
+	return conf;
+}
+
+static int pxe_parse(struct discover_context *dc)
+{
+	struct pb_url *pxe_base_url, *url;
+	char **pxe_conf_files, **filename;
+	struct conf_context *conf = NULL;
+	struct load_url_result *result;
+	void *ctx = talloc_parent(dc);
+	bool complete_url;
+
+	/* Expects dhcp event parameters to support network boot */
+	if (!dc->event)
+		return -1;
+
+	/*
+	 * Retrieving PXE configs over the network can take some time depending
+	 * on factors such as slow network, malformed paths, bad DNS, and
+	 * overzealous firewalls. Instead of blocking the discover server while
+	 * we wait for these, spawn an asynchronous job for each URL we can
+	 * parse and process the resulting files in a callback.
+	 * Since the caller will free the discover_context once
+	 * iterate_parsers() completes, we need to copy the discover_context
+	 * under a different talloc context so that it survives until the
+	 * callback is finished with it.
+	 */
 
 	dc->conf_url = user_event_parse_conf_url(dc, dc->event, &complete_url);
 	if (!dc->conf_url)
-		goto out_conf;
+		return -1;
+	conf = copy_context(ctx, dc);
+	if (!conf)
+		return -1;
 
 	if (complete_url) {
 		/* we have a complete URL; use this and we're done. */
-		rc = parser_request_url(dc, dc->conf_url, &buf, &len);
-		if (rc)
+		result = load_url_async(conf->dc, conf->dc->conf_url,
+					pxe_conf_parse_cb, conf);
+		if (!result) {
+			pb_log("load_url_async fails for %s\n", dc->conf_url->path);
 			goto out_conf;
+		}
 	} else {
-		pxe_conf_files = user_event_parse_conf_filenames(dc, dc->event);
+		pxe_conf_files = user_event_parse_conf_filenames(dc,
+								dc->event);
 		if (!pxe_conf_files)
 			goto out_conf;
 
-		rc = -1;
-
-		pxe_base_url = pb_url_join(dc, dc->conf_url, pxelinux_prefix);
+		pxe_base_url = pb_url_join(dc, dc->conf_url,
+					   pxelinux_prefix);
 		if (!pxe_base_url)
 			goto out_pxe_conf;
 
 		for (filename = pxe_conf_files; *filename; filename++) {
-			url = pb_url_join(dc, pxe_base_url, *filename);
+			if (!conf) {
+				conf = copy_context(ctx, dc);
+			}
+			url = pb_url_join(conf->dc, pxe_base_url, *filename);
 			if (!url)
 				continue;
-
-			rc = parser_request_url(dc, url, &buf, &len);
-			if (!rc) /* found one, just break */
-				break;
-
-			talloc_free(url);
+			result = load_url_async(conf, url, pxe_conf_parse_cb, conf);
+			if (!result) {
+				pb_log("load_url_async fails for %s\n",
+				       conf->dc->conf_url->path);
+				talloc_free(conf);
+			}
+			/* conf now needed by callback, don't reuse */
+			conf = NULL;
 		}
 
 		talloc_free(pxe_base_url);
-
-		/* No configuration file found on the boot server */
-		if (rc)
-			goto out_pxe_conf;
-
 		talloc_free(pxe_conf_files);
 	}
 
-	/* Call the config file parser with the data read from the file */
-	conf_parse_buf(conf, buf, len);
-
-	talloc_free(buf);
-	talloc_free(conf);
-
 	return 0;
 
 out_pxe_conf:
 	talloc_free(pxe_conf_files);
 out_conf:
 	talloc_free(conf);
-out:
 	return -1;
 }
 
diff --git a/lib/url/url.c b/lib/url/url.c
index 7202f49..6eeced3 100644
--- a/lib/url/url.c
+++ b/lib/url/url.c
@@ -246,7 +246,7 @@  static void pb_url_update_full(struct pb_url *url)
 	url->full = pb_url_to_string(url);
 }
 
-static struct pb_url *pb_url_copy(void *ctx, const struct pb_url *url)
+struct pb_url *pb_url_copy(void *ctx, const struct pb_url *url)
 {
 	struct pb_url *new_url;
 
diff --git a/lib/url/url.h b/lib/url/url.h
index 25e1ad8..9043615 100644
--- a/lib/url/url.h
+++ b/lib/url/url.h
@@ -62,6 +62,7 @@  struct pb_url {
 
 bool is_url(const char *str);
 struct pb_url *pb_url_parse(void *ctx, const char *url_str);
+struct pb_url *pb_url_copy(void *ctx, const struct pb_url *url);
 struct pb_url *pb_url_join(void *ctx, const struct pb_url *url, const char *s);
 char *pb_url_to_string(struct pb_url *url);