[tor-commits] [tor/release-0.2.9] Always allow extra file descriptors when setting the connection maximum

[nickm at torproject.org]

commit 878e0d45a5d1469965d456a5d8a436b45ac59c3a
Author: teor <teor2345 at gmail.com>
Date:   Mon Jul 3 15:30:52 2017 +1000

    Always allow extra file descriptors when setting the connection maximum
    
    When setting the maximum number of connections allowed by the OS,
    always allow some extra file descriptors for other files.
    
    Fixes bug 22797; bugfix on 0.2.0.10-alpha.
---
 changes/bug22797    |  4 ++++
 src/common/compat.c | 19 ++++++++++++-------
 2 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/changes/bug22797 b/changes/bug22797
new file mode 100644
index 000000000..619baaa40
--- /dev/null
+++ b/changes/bug22797
@@ -0,0 +1,4 @@
+  o Minor bugfixes (file limits):
+    - When setting the maximum number of connections allowed by the OS,
+      always allow some extra file descriptors for other files.
+      Fixes bug 22797; bugfix on 0.2.0.10-alpha.
diff --git a/src/common/compat.c b/src/common/compat.c
index e25ecc462..eee52ad34 100644
--- a/src/common/compat.c
+++ b/src/common/compat.c
@@ -1568,19 +1568,24 @@ set_max_file_descriptors(rlim_t limit, int *max_out)
   if (setrlimit(RLIMIT_NOFILE, &rlim) != 0) {
     int bad = 1;
 #ifdef OPEN_MAX
-    if (errno == EINVAL && OPEN_MAX < rlim.rlim_cur) {
+    uint64_t try_limit = OPEN_MAX - ULIMIT_BUFFER;
+    if (errno == EINVAL && try_limit < rlim.rlim_cur) {
       /* On some platforms, OPEN_MAX is the real limit, and getrlimit() is
        * full of nasty lies.  I'm looking at you, OSX 10.5.... */
-      rlim.rlim_cur = OPEN_MAX;
+      rlim.rlim_cur = try_limit;
       if (setrlimit(RLIMIT_NOFILE, &rlim) == 0) {
         if (rlim.rlim_cur < (rlim_t)limit) {
           log_warn(LD_CONFIG, "We are limited to %lu file descriptors by "
-                 "OPEN_MAX, and ConnLimit is %lu.  Changing ConnLimit; sorry.",
-                   (unsigned long)OPEN_MAX, (unsigned long)limit);
+                   "OPEN_MAX (%lu), and ConnLimit is %lu.  Changing "
+                   "ConnLimit; sorry.",
+                   (unsigned long)try_limit, (unsigned long)OPEN_MAX,
+                   (unsigned long)limit);
         } else {
-          log_info(LD_CONFIG, "Dropped connection limit to OPEN_MAX (%lu); "
-                   "Apparently, %lu was too high and rlimit lied to us.",
-                   (unsigned long)OPEN_MAX, (unsigned long)rlim.rlim_max);
+          log_info(LD_CONFIG, "Dropped connection limit to %lu based on "
+                   "OPEN_MAX (%lu); Apparently, %lu was too high and rlimit "
+                   "lied to us.",
+                   (unsigned long)try_limit, (unsigned long)OPEN_MAX,
+                   (unsigned long)rlim.rlim_max);
         }
         bad = 0;
       }