[PATCH] Redo max_sd() for (hopefully) better results

The attached patch (/nmap-exp/kris SVN r4351) redoes max_sd() (tcpip.cc)
so that we can try to get more out of it. The documentation (comments)
in the patch and the SVN log below should explain it all.

------------------------------------------------------------------------
r4351 | kris | 2007-01-13 18:19:04 -0600 (Sat, 13 Jan 2007) | 1 line

This basically redoes max_sd() (tcpip.cc). If we're root, we attempt to
set the limit to RLIM_INFINITY or (if that fails) POSIX _SC_OPEN_MAX (if
available). If that fails or we weren't root to begin with, we just set
rlim_cur=rlim_max. It's still "experimental" (because I kinda tossed it
together), but I don't have any problems with it. Hopefully I can get
some feedback from people with other OS's on nmap-dev.
------------------------------------------------------------------------

I'd really appreciate any feedback on it.

Thanks,
Kris Katterjohn

Index: tcpip.cc
===================================================================
--- tcpip.cc (revision 4350)
+++ tcpip.cc (revision 4351)
@@ -3051,39 +3051,87 @@
 }
 
 /* Maximize the open file descriptor limit for this process go up to the
- max allowed */
+ * max allowed. If we're root, we try setting rlim_cur and rlim_max to
+ * RLIM_INFINITY to try to "remove" the limit. Some OS's have a problem
+ * with that, so if that fails we try to set them to the POSIX _SC_OPEN_MAX
+ * (if available and bigger than rlim_max but smaller than RLIM_INFINITY).
+ * If that fails too we resort to rlim_cur=rlim_max. If we're not root we
+ * just do rlim_cur=rlim_max.
+ */
 int max_sd() {
 #ifndef WIN32
- struct rlimit r;
+ struct rlimit r, sr;
+ int ret = -1;
   static int maxfds = -1;
+#ifdef _SC_OPEN_MAX
+ static long openmax = sysconf(_SC_OPEN_MAX);
+#else
+ static long openmax;
+#endif
 
   if (maxfds > 0)
     return maxfds;
 
-#if(defined(RLIMIT_NOFILE))
+ /* if sysconf() failed for some reason */
+ if (openmax == -1)
+ openmax = 0;
+
+#ifdef RLIMIT_NOFILE
+ if (o.isr00t) {
+ sr.rlim_cur = sr.rlim_max = RLIM_INFINITY;
+ ret = setrlimit(RLIMIT_NOFILE, &sr);
+ }
+
+ if (ret && !getrlimit(RLIMIT_NOFILE, &r)) {
+ if (o.isr00t && ((rlim_t) openmax > r.rlim_max) && ((rlim_t) openmax < RLIM_INFINITY)) {
+ sr.rlim_cur = sr.rlim_max = openmax;
+
+ ret = setrlimit(RLIMIT_NOFILE, &sr);
+ }
+
+ if (ret) {
+ r.rlim_cur = r.rlim_max;
+
+ if (setrlimit(RLIMIT_NOFILE, &r))
+ if (o.debugging)
+ perror("setrlimit RLIMIT_NOFILE failed");
+ }
+ }
+
   if (!getrlimit(RLIMIT_NOFILE, &r)) {
- r.rlim_cur = r.rlim_max;
- if (setrlimit(RLIMIT_NOFILE, &r))
- if (o.debugging) perror("setrlimit RLIMIT_NOFILE failed");
- if (!getrlimit(RLIMIT_NOFILE, &r)) {
- maxfds = r.rlim_cur;
- return maxfds;
- } else return 0;
+ maxfds = r.rlim_cur;
+ return maxfds;
   }
-#endif
-#if(defined(RLIMIT_OFILE) && !defined(RLIMIT_NOFILE))
- if (!getrlimit(RLIMIT_OFILE, &r)) {
- r.rlim_cur = r.rlim_max;
- if (setrlimit(RLIMIT_OFILE, &r))
- if (o.debugging) perror("setrlimit RLIMIT_OFILE failed");
- if (!getrlimit(RLIMIT_OFILE, &r)) {
- maxfds = r.rlim_cur;
- return maxfds;
+#elif defined RLIMIT_OFILE
+ if (o.isr00t) {
+ sr.rlim_cur = sr.rlim_max = RLIM_INFINITY;
+ ret = setrlimit(RLIMIT_OFILE, &sr);
+ }
+
+ if (ret && !getrlimit(RLIMIT_OFILE, &r)) {
+ if (o.isr00t && ((rlim_t) openmax > r.rlim_max) && ((rlim_t) openmax < RLIM_INFINITY)) {
+ sr.rlim_cur = sr.rlim_max = openmax;
+
+ ret = setrlimit(RLIMIT_OFILE, &sr);
     }
- else return 0;
+
+ if (ret) {
+ r.rlim_cur = r.rlim_max;
+
+ if (setrlimit(RLIMIT_OFILE, &r))
+ if (o.debugging)
+ perror("setrlimit RLIMIT_OFILE failed");
+ }
   }
+
+ if (!getrlimit(RLIMIT_OFILE, &r)) {
+ maxfds = r.rlim_cur;
+ return maxfds;
+ }
 #endif
 #endif /* WIN32 */
+
+ /* something went wrong */
   return 0;
 }
 

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Received on Jan 13 2007