Fixed file descriptor closing issues on FreeBSD: issue phusion#597.

Phusion Passenger child processes didn't correct close file descriptors on FreeBSD because it queries /dev/fd to do that. On FreeBSD /dev/fd only returns meaningful results if fdescfs is mounted, which it isn't by default.
fr34k8 · Dec 11, 2010 · 9a81106 · 9a81106
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diff --git a/NEWS b/NEWS
@@ -9,6 +9,11 @@ Release 3.0.2
    There was a typo in a NetBSD-specific fcntl() call. It also turns out that
    NetBSD doesn't support some ISO C99 math functions like llroundl(); this
    has been worked around by using other functions. Issue #593.
+ * Fixed file descriptor closing issues on FreeBSD
+   Phusion Passenger child processes didn't correct close file descriptors
+   on FreeBSD because it queries /dev/fd to do that. On FreeBSD /dev/fd
+   only returns meaningful results if fdescfs is mounted, which it isn't
+   by default. Issue #597.
 
 
 Release 3.0.1

diff --git a/ext/common/Utils.cpp b/ext/common/Utils.cpp
@@ -837,7 +837,26 @@ getHighestFileDescriptor() {
 		sigaction(SIGFPE, &action, NULL);
 		sigaction(SIGABRT, &action, NULL);
 
-		DIR *dir = opendir("/dev/fd");
+		DIR *dir = NULL;
+		#ifdef __APPLE__
+			/* /dev/fd can always be trusted on OS X. */
+			dir = opendir("/dev/fd");
+		#else
+			/* On FreeBSD and possibly other operating systems, /dev/fd only
+			 * works if fdescfs is mounted. If it isn't mounted then /dev/fd
+			 * still exists but always returns [0, 1, 2] and thus can't be
+			 * trusted. If /dev and /dev/fd are on different filesystems
+			 * then that probably means fdescfs is mounted.
+			 */
+			struct stat dirbuf1, dirbuf2;
+			if (stat("/dev", &dirbuf1) == -1
+			 || stat("/dev/fd", &dirbuf2) == -1) {
+				_exit(1);
+			}
+			if (dirbuf1.st_dev != dirbuf2.st_dev) {
+				dir = opendir("/dev/fd");
+			}
+		#endif
 		if (dir == NULL) {
 			dir = opendir("/proc/self/fd");
 			if (dir == NULL) {