From a3d9ed2388e96798b60441bba36f29657e4d7d8e Mon Sep 17 00:00:00 2001
From: Kienan Stewart <kstewart@efficios.com>
Date: Mon, 27 Nov 2023 11:32:42 -0500
Subject: [PATCH] sessiond: Add initial support for multiple
 LTTNG_UST_CTL_PATHs
MIME-Version: 1.0
Content-Type: text/plain; charset=utf8
Content-Transfer-Encoding: 8bit

LTTNG_UST_CTL_PATH may be separated with ':'. There is no provision
for escaping the ':' path separator (similar to `$PATH`). Subsequent
paths after the first are ignored.

Signed-off-by: Kienan Stewart <kstewart@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Change-Id: I80f7d63e4be164f7afe3fe478794bd55c71c31fb
---
 src/bin/lttng-sessiond/sessiond-config.cpp |  7 ++--
 src/common/utils.cpp                       | 38 ++++++++++++++++++----
 src/common/utils.hpp                       |  2 +-
 3 files changed, 36 insertions(+), 11 deletions(-)

diff --git a/src/bin/lttng-sessiond/sessiond-config.cpp b/src/bin/lttng-sessiond/sessiond-config.cpp
index 774a2c143..0a12d9d7f 100644
--- a/src/bin/lttng-sessiond/sessiond-config.cpp
+++ b/src/bin/lttng-sessiond/sessiond-config.cpp
@@ -45,7 +45,7 @@ static struct sessiond_config sessiond_config_build_defaults = {
 
 	.apps_unix_sock_path = { nullptr, false },
 	.client_unix_sock_path = { nullptr, false },
-	.wait_shm = { false, {nullptr, false}},
+	.wait_shm = { false, { nullptr, false } },
 	.health_unix_sock_path = { nullptr, false },
 	.lttng_ust_clock_plugin = { nullptr, false },
 	.pid_file_path = { nullptr, false },
@@ -272,10 +272,11 @@ end:
 
 int sessiond_config_init(struct sessiond_config *config)
 {
-	const char *lttng_ust_ctl_path_override = utils_get_lttng_ust_ctl_path_override_dir();
 	int ret;
 	const bool is_root = (getuid() == 0);
 	char *str;
+	auto lttng_ust_ctl_path_override = lttng::make_unique_wrapper<char, lttng::memory::free>(
+		utils_get_lttng_ust_ctl_path_override_dir());
 
 	LTTNG_ASSERT(config);
 	memcpy(config, &sessiond_config_build_defaults, sizeof(*config));
@@ -297,7 +298,7 @@ int sessiond_config_init(struct sessiond_config *config)
 		 *   - wait_shm_path
 		 *   - agent_port_file_path
 		 */
-		ret = config_set_ust_ctl_paths(config, lttng_ust_ctl_path_override);
+		ret = config_set_ust_ctl_paths(config, lttng_ust_ctl_path_override.get());
 		if (ret < 0) {
 			goto error;
 		}
diff --git a/src/common/utils.cpp b/src/common/utils.cpp
index 314003330..0f9fae763 100644
--- a/src/common/utils.cpp
+++ b/src/common/utils.cpp
@@ -20,10 +20,12 @@
 #include <common/format.hpp>
 #include <common/readwrite.hpp>
 #include <common/runas.hpp>
+#include <common/string-utils/c-string-view.hpp>
 #include <common/string-utils/format.hpp>
 
 #include <lttng/constant.h>
 
+#include <algorithm>
 #include <ctype.h>
 #include <fcntl.h>
 #include <grp.h>
@@ -742,20 +744,42 @@ end:
 }
 
 /*
- * Obtain the value of LTTNG_UST_CTL_PATH environment variable, if
- * exists.  Otherwise return NULL.
+ * Obtain the value of the LTTNG_UST_CTL_PATH environment variable, if
+ * it is set. Otherwise NULL is returned. Dynamically allocated, must be
+ * freed by the caller.
  */
-const char *utils_get_lttng_ust_ctl_path_override_dir()
+char *utils_get_lttng_ust_ctl_path_override_dir()
 {
-	const auto *val = lttng_secure_getenv(DEFAULT_LTTNG_UST_CTL_PATH_ENV_VAR);
-	if (val == nullptr) {
+	const lttng::c_string_view env_val(lttng_secure_getenv(DEFAULT_LTTNG_UST_CTL_PATH_ENV_VAR));
+	if (env_val.data() == nullptr) {
 		return nullptr;
 	}
 
 	DBG_FMT("LTTng ust-ctl override path specified: {}=`{}`",
 		DEFAULT_LTTNG_UST_CTL_PATH_ENV_VAR,
-		val);
-	return val;
+		env_val);
+
+	const auto separator_location = std::find(env_val.begin(), env_val.end(), ':');
+	if (separator_location == env_val.end()) {
+		auto new_val = ::strdup(env_val);
+		if (!new_val) {
+			PERROR("Failed to allocate LTTng ust-ctl override path override value");
+		}
+
+		return new_val;
+	}
+
+	WARN("LTTng ust-ctl override path contains multiple values; only the first will be considered");
+
+	const auto length = std::distance(env_val.begin(), separator_location);
+	auto new_val = zmalloc<char>(length + 1);
+	if (new_val == nullptr) {
+		PERROR("Failed to allocate LTTng ust-ctl override path override value");
+		return nullptr;
+	}
+
+	std::strncpy(new_val, env_val.data(), length);
+	return new_val;
 }
 
 /*
diff --git a/src/common/utils.hpp b/src/common/utils.hpp
index e1ff53fc4..ed9cff805 100644
--- a/src/common/utils.hpp
+++ b/src/common/utils.hpp
@@ -44,7 +44,7 @@ int utils_get_count_order_u32(uint32_t x);
 int utils_get_count_order_u64(uint64_t x);
 const char *utils_get_home_dir();
 char *utils_get_user_home_dir(uid_t uid);
-const char *utils_get_lttng_ust_ctl_path_override_dir();
+char *utils_get_lttng_ust_ctl_path_override_dir();
 
 size_t utils_get_current_time_str(const char *format, char *dst, size_t len)
 	ATTR_FORMAT_STRFTIME(1);
-- 
2.34.1