From 26c944125bde337329180b65d3c12fa89c413d77 Mon Sep 17 00:00:00 2001
From: "Alexander A. Klimov" <alexander.klimov@icinga.com>
Date: Tue, 12 Jan 2021 17:32:28 +0100
Subject: [PATCH] Close FDs based on /proc/self/fd

... not to waste time with close(2)ing RLIMIT_NOFILE-3 non-existing FDs.

Newer kernel = higher RLIMIT_NOFILE = more time wasted

refs #8437
---
 icinga-app/icinga.cpp | 19 +++-----------
 lib/base/process.cpp  | 12 +--------
 lib/base/utility.cpp  | 61 +++++++++++++++++++++++++++++++++++++++++--
 lib/base/utility.hpp  |  3 +++
 4 files changed, 67 insertions(+), 28 deletions(-)

diff --git a/icinga-app/icinga.cpp b/icinga-app/icinga.cpp
index 7aef1ca03..05f4944f6 100644
--- a/icinga-app/icinga.cpp
+++ b/icinga-app/icinga.cpp
@@ -906,24 +906,13 @@ int main(int argc, char **argv)
 #ifndef _WIN32
 	String keepFDs = Utility::GetFromEnvironment("ICINGA2_KEEP_FDS");
 	if (keepFDs.IsEmpty()) {
-		rlimit rl;
-		if (getrlimit(RLIMIT_NOFILE, &rl) >= 0) {
-			rlim_t maxfds = rl.rlim_max;
-
-			if (maxfds == RLIM_INFINITY)
-				maxfds = 65536;
-
-			for (rlim_t i = 3; i < maxfds; i++) {
-				int rc = close(i);
-
 #ifdef I2_DEBUG
-				if (rc >= 0)
-					std::cerr << "Closed FD " << i << " which we inherited from our parent process." << std::endl;
+		Utility::CloseAllFDs({0, 1, 2}, [](int fd) {
+			std::cerr << "Closed FD " << fd << " which we inherited from our parent process." << std::endl;
+		});
 #else /* I2_DEBUG */
-				(void)rc;
+		Utility::CloseAllFDs({0, 1, 2});
 #endif /* I2_DEBUG */
-			}
-		}
 	}
 #endif /* _WIN32 */
 
diff --git a/lib/base/process.cpp b/lib/base/process.cpp
index c16eaa7c1..16106d21d 100644
--- a/lib/base/process.cpp
+++ b/lib/base/process.cpp
@@ -240,17 +240,7 @@ static void ProcessHandler()
 	sigfillset(&mask);
 	sigprocmask(SIG_SETMASK, &mask, nullptr);
 
-	rlimit rl;
-	if (getrlimit(RLIMIT_NOFILE, &rl) >= 0) {
-		rlim_t maxfds = rl.rlim_max;
-
-		if (maxfds == RLIM_INFINITY)
-			maxfds = 65536;
-
-		for (rlim_t i = 3; i < maxfds; i++)
-			if (i != static_cast<rlim_t>(l_ProcessControlFD))
-				(void)close(i);
-	}
+	Utility::CloseAllFDs({0, 1, 2, l_ProcessControlFD});
 
 	for (;;) {
 		size_t length;
diff --git a/lib/base/utility.cpp b/lib/base/utility.cpp
index d8e6f20b0..1c3ec0a9c 100644
--- a/lib/base/utility.cpp
+++ b/lib/base/utility.cpp
@@ -9,10 +9,10 @@
 #include "base/utility.hpp"
 #include "base/json.hpp"
 #include "base/objectlock.hpp"
+#include <algorithm>
 #include <cstdint>
 #include <mmatch.h>
-#include <boost/filesystem/path.hpp>
-#include <boost/filesystem/operations.hpp>
+#include <boost/filesystem.hpp>
 #include <boost/lexical_cast.hpp>
 #include <boost/system/error_code.hpp>
 #include <boost/thread/tss.hpp>
@@ -27,6 +27,7 @@
 #include <iterator>
 #include <stdlib.h>
 #include <future>
+#include <set>
 #include <utf8.h>
 #include <vector>
 
@@ -44,6 +45,7 @@
 #	include <pwd.h>
 #	include <grp.h>
 #	include <errno.h>
+#	include <unistd.h>
 #endif /* _WIN32 */
 
 #ifdef _WIN32
@@ -833,6 +835,61 @@ void Utility::SetCloExec(int fd, bool cloexec)
 			<< boost::errinfo_errno(errno));
 	}
 }
+
+void Utility::CloseAllFDs(const std::vector<int>& except, std::function<void(int)> onClose)
+{
+#if defined(__linux__) || defined(__APPLE__)
+	namespace fs = boost::filesystem;
+
+	std::set<int> fds;
+
+#ifdef __linux__
+	const char *dir = "/proc/self/fd";
+#endif /* __linux__ */
+#ifdef __APPLE__
+	const char *dir = "/dev/fd";
+#endif /* __APPLE__ */
+
+	for (fs::directory_iterator current {fs::path(dir)}, end; current != end; ++current) {
+		auto entry (current->path().filename());
+		int fd;
+
+		try {
+			fd = boost::lexical_cast<int>(entry.c_str());
+		} catch (...) {
+			continue;
+		}
+
+		fds.emplace(fd);
+	}
+
+	for (auto fd : except) {
+		fds.erase(fd);
+	}
+
+	for (auto fd : fds) {
+		if (close(fd) >= 0 && onClose) {
+			onClose(fd);
+		}
+	}
+#else /* __linux__ || __APPLE__ */
+	rlimit rl;
+
+	if (getrlimit(RLIMIT_NOFILE, &rl) >= 0) {
+		rlim_t maxfds = rl.rlim_max;
+
+		if (maxfds == RLIM_INFINITY) {
+			maxfds = 65536;
+		}
+
+		for (int fd = 0; fd < maxfds; ++fd) {
+			if (std::find(except.begin(), except.end(), fd) == except.end() && close(fd) >= 0 && onClose) {
+				onClose(fd);
+			}
+		}
+	}
+#endif /* __linux__ || __APPLE__ */
+}
 #endif /* _WIN32 */
 
 void Utility::SetNonBlockingSocket(SOCKET s, bool nb)
diff --git a/lib/base/utility.hpp b/lib/base/utility.hpp
index 676016089..0fb216d9e 100644
--- a/lib/base/utility.hpp
+++ b/lib/base/utility.hpp
@@ -8,6 +8,7 @@
 #include "base/array.hpp"
 #include "base/threadpool.hpp"
 #include <boost/thread/tss.hpp>
+#include <functional>
 #include <typeinfo>
 #include <vector>
 
@@ -80,6 +81,8 @@ public:
 #ifndef _WIN32
 	static void SetNonBlocking(int fd, bool nb = true);
 	static void SetCloExec(int fd, bool cloexec = true);
+
+	static void CloseAllFDs(const std::vector<int>& except, std::function<void(int)> onClose = nullptr);
 #endif /* _WIN32 */
 
 	static void SetNonBlockingSocket(SOCKET s, bool nb = true);