patch: properly zeroing fd_set in clientloop

[Pekka Savola]

Hello all,

This is a problem and patch reported to Red Hat Bugzilla by
Jonathan Kamens <jik at kamens.brookline.ma.us>. I'm just acting as a relay
:-)

jik has experienced some weird crashes relating to window size changes or
some similar activity.  These are rather hard to trace.

Problem was fixed by patching clientloop, where fd_set structures appear
to be improperly zeroed (bytes vs bits).

FD_ZERO does not appear to work as fd_sets are just pointers in this case,
so alternative method is used.

Patch by jik attached (does not apply cleantly to CVS but the idea should
be apparent).

-- 
Pekka Savola                 "Tell me of difficulties surmounted,
Netcore Oy                   not those you stumble over and fall"
Systems. Networks. Security.  -- Robert Jordan: A Crown of Swords

-------------- next part --------------
--- channels.h~	Wed Jun 13 15:18:05 2001
+++ channels.h	Thu Jul 12 08:31:58 2001
@@ -168,6 +168,13 @@
 void    channel_free(int channel);
 
 /*
+ * Zero out a select file-descriptor set.  Analogous to the FD_ZERO
+ * macro, but works with different-sized sets.
+ */
+void
+channel_zero_set(fd_set *setp, int maxfdp);
+
+/*
  * Allocate/update select bitmasks and add any bits relevant to channels in
  * select bitmasks.
  */
--- channels.c~	Wed Jun 13 15:18:05 2001
+++ channels.c	Thu Jul 12 08:32:53 2001
@@ -1160,6 +1160,14 @@
 }
 
 void
+channel_zero_set(fd_set *setp, int maxfdp)
+{
+  u_int sz = howmany(maxfdp+1, NFDBITS) * sizeof(fd_mask);
+
+  memset(setp, 0, sz);
+}
+
+void
 channel_prepare_select(fd_set **readsetp, fd_set **writesetp, int *maxfdp,
     int rekeying)
 {
@@ -1178,8 +1186,8 @@
 		*writesetp = xmalloc(sz);
 		*maxfdp = n;
 	}
-	memset(*readsetp, 0, sz);
-	memset(*writesetp, 0, sz);
+	channel_zero_set(*readsetp, *maxfdp);
+	channel_zero_set(*writesetp, *maxfdp);
 
 	if (!rekeying)
 		channel_handler(channel_pre, *readsetp, *writesetp);
--- clientloop.c~	Fri Apr 20 08:50:51 2001
+++ clientloop.c	Thu Jul 12 08:33:33 2001
@@ -370,8 +370,8 @@
 		 * We have to return, because the mainloop checks for the flags
 		 * set by the signal handlers.
 		 */
-		memset(*readsetp, 0, *maxfdp);
-		memset(*writesetp, 0, *maxfdp);
+		channel_zero_set(*readsetp, *maxfdp);
+		channel_zero_set(*writesetp, *maxfdp);
 
 		if (errno == EINTR)
 			return;