[Bro] a odd problem

[Vern Paxson]

>     [cliff at oradata bro-pub-0.9a3]$ ./bro mt -i eth0
>     input in flex scanner failed

I tracked this down (and fixed it).  The problem is that reading the file
"mt" fails in some fashion.  The example I was able to reproduce was when
"mt" was a directory rather than a text file.  (The same could happen if
"mt.bro" is a directory).  Inspect your $BROPATH to see what file it's
opening.

The fix is for a better error message in this case.  For example, if "mt"
is a subdirectory in the current directory, you'll get:

./mt, line 1: error: read failed with "Operation not permitted"

I've appended a patch for it, which will be included in the next release.

		Vern


RCS file: /home/portnoy/u2/src/projects/bro/src/scan.l,v
retrieving revision 1.4
retrieving revision 1.5
diff -Lsrc/scan.l -Lsrc/scan.l -u -r1.4 -r1.5
--- src/scan.l
+++ src/scan.l
@@ -19,6 +19,8 @@
 // WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
 // MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 
+#include <errno.h>
+
 #include "input.h"
 #include "util.h"
 #include "Scope.h"
@@ -53,6 +55,14 @@
 
 #define YY_USER_ACTION	strncpy(last_tok, yytext, sizeof(last_tok) - 1);
 #define YY_USER_INIT	last_tok[0] = '\0';
+
+extern "C" const char* const sys_errlist[];
+
+// We define our own YY_INPUT because we want to trap the case where
+// a read fails.
+#define YY_INPUT(buf,result,max_size) \
+	if ( ((result = fread(buf, 1, max_size, yyin)) == 0) && ferror(yyin) ) \
+		error(fmt("read failed with \"%s\"", sys_errlist[errno]));
 
 // Files we have already scanned (or are in the process of scanning).
 static PList(char) files_scanned;