GH-928: use realpath() instead of inode to de-duplicate scripts

Duplicate script `@load` directives are now detected by comparing
against canonical paths formed by realpath().  This fixes the previous,
unexpected behavior of treating scripts that hardlink to same
inode as duplicates: such links will now be loaded as distinct scripts
since their canonical path differs.

src/Net.h

@@ -86,24 +86,23 @@ extern iosource::IOSource* current_iosrc;
 extern iosource::PktDumper* pkt_dumper;	// where to save packets
 
 // Script file we have already scanned (or are in the process of scanning).
-// They are identified by device and inode number.
+// They are identified by normalized realpath.
 struct ScannedFile {
-	dev_t dev;
-	ino_t inode;
 	int include_level;
 	bool skipped;		// This ScannedFile was @unload'd.
 	bool prefixes_checked;	// If loading prefixes for this file has been tried.
 	std::string name;
+	std::string canonical_path; // normalized, absolute path via realpath()
 
-	ScannedFile(dev_t arg_dev, ino_t arg_inode, int arg_include_level,
-	            const std::string& arg_name, bool arg_skipped = false,
-	            bool arg_prefixes_checked = false)
-		: dev(arg_dev), inode(arg_inode),
-		  include_level(arg_include_level),
-		  skipped(arg_skipped),
-		  prefixes_checked(arg_prefixes_checked),
-		  name(arg_name)
-		{ }
+	ScannedFile(int arg_include_level,
+	            std::string arg_name, bool arg_skipped = false,
+	            bool arg_prefixes_checked = false);
+
+	/**
+	 * Compares the canonical path of this file against every canonical path
+	 * in files_scanned and returns whether there's any match.
+	 */
+	bool AlreadyScanned() const;
 };
 
 extern std::list<ScannedFile> files_scanned;

src/scan.l

@@ -3,6 +3,9 @@
 
 #include <errno.h>
 
+#include <climits>
+#include <cstdlib>
+
 #include <stack>
 #include <list>
 #include <string>
@@ -39,13 +42,6 @@
 
 using namespace zeek::detail;
 
-namespace {
-struct ZeekINode {
-	dev_t dev;
-	ino_t ino;
-};
-}
-
 extern YYLTYPE yylloc;	// holds start line and column of token
 extern zeek::EnumType* cur_enum_type;
 
@@ -101,30 +97,6 @@ static std::string find_relative_script_file(const std::string& filename)
 		return find_script_file(filename, bro_path());
 	}
 
-static ZeekINode get_inode(FILE* f, const std::string& path)
-	{
-	struct stat b;
-
-	if ( fstat(fileno(f), &b) )
-		reporter->FatalError("fstat of %s failed: %s\n", path.c_str(),
-		                     strerror(errno));
-
-	return {b.st_dev, b.st_ino};
-	}
-
-static ZeekINode get_inode(const std::string& path)
-	{
-	FILE* f = open_file(path);
-
-	if ( ! f )
-		reporter->FatalError("failed to open %s\n", path.c_str());
-
-	auto inode = get_inode(f, path);
-	fclose(f);
-
-	return inode;
-	}
-
 class FileInfo {
 public:
 	FileInfo(std::string restore_module = "");
@@ -430,9 +402,8 @@ when	return TOK_WHEN;
 	else
 		{
 		// All we have to do is pretend we've already scanned it.
-		auto i = get_inode(path);
-		ScannedFile sf(i.dev, i.ino, file_stack.length(), path, true);
-		files_scanned.push_back(sf);
+		ScannedFile sf(file_stack.length(), std::move(path), true);
+		files_scanned.push_back(std::move(sf));
 		}
 	}
 
@@ -598,19 +569,7 @@ YYLTYPE zeek::detail::GetCurrentLocation()
 	return currloc;
 	}
 
-static bool already_scanned(ZeekINode in)
-	{
-	for ( const auto& it : files_scanned )
-		if ( it.dev == in.dev && it.inode == in.ino )
-			return true;
-
-	return false;
-	}
-
-static bool already_scanned(const std::string& path)
-	{
-	return already_scanned(get_inode(path));
-	}
+static auto constexpr canonical_stdin_path = "<stdin>";
 
 static int load_files(const char* orig_file)
 	{
@@ -641,7 +600,7 @@ static int load_files(const char* orig_file)
 	if ( streq(orig_file, "-") )
 		{
 		f = stdin;
-		file_path = "<stdin>";
+		file_path = canonical_stdin_path;
 
 		if ( g_policy_debug )
 			{
@@ -664,9 +623,9 @@ static int load_files(const char* orig_file)
 			reporter->FatalError("can't open %s", file_path.c_str());
 		}
 
-	auto i = get_inode(f, file_path);
+	ScannedFile sf(file_stack.length(), file_path);
 
-	if ( already_scanned(i) )
+	if ( sf.AlreadyScanned() )
 		{
 		if ( f != stdin )
 			fclose(f);
@@ -674,8 +633,7 @@ static int load_files(const char* orig_file)
 		return 0;
 		}
 
-	ScannedFile sf(i.dev, i.ino, file_stack.length(), file_path);
-	files_scanned.push_back(sf);
+	files_scanned.push_back(std::move(sf));
 
 	if ( g_policy_debug && ! file_path.empty() )
 		{
@@ -1079,3 +1037,42 @@ FileInfo::~FileInfo()
 	if ( restore_module != "" )
 		zeek::detail::current_module = restore_module;
 	}
+
+ScannedFile::ScannedFile(int arg_include_level,
+                         std::string arg_name,
+                         bool arg_skipped,
+                         bool arg_prefixes_checked)
+	: include_level(arg_include_level),
+	  skipped(arg_skipped),
+	  prefixes_checked(arg_prefixes_checked),
+	  name(std::move(arg_name))
+	{
+	if ( name == canonical_stdin_path )
+		canonical_path = canonical_stdin_path;
+	else
+		{
+		char buf[PATH_MAX];
+		auto res = realpath(name.data(), buf);
+
+		if ( ! res )
+			reporter->FatalError("failed to get realpath() of %s: %s",
+			                     name.data(), strerror(errno));
+
+		canonical_path = res;
+		}
+	}
+
+bool ScannedFile::AlreadyScanned() const
+	{
+	auto rval = false;
+
+	for ( const auto& it : files_scanned )
+		if ( it.canonical_path == canonical_path )
+			{
+			rval = true;
+			break;
+			}
+
+	DBG_LOG(DBG_SCRIPTS, "AlreadyScanned result (%d) %s", rval, canonical_path.data());
+	return rval;
+	}

testing/btest/Baseline/core.load-duplicates-links/out

@@ -0,0 +1,3 @@
+foo
+bar
+baz

testing/btest/core/load-duplicates-links.zeek

@@ -0,0 +1,20 @@
+# This tests Zeek's mechanism to prevent duplicate script loading on links.
+#
+# @TEST-EXEC: mkdir foo
+# @TEST-EXEC: mkdir bar
+# @TEST-EXEC: mkdir baz
+
+# @TEST-EXEC: echo 'event zeek_init() &priority=3 { print "foo"; }' >foo/main.zeek
+# @TEST-EXEC: echo 'event zeek_init() &priority=2 { print "bar"; }' >bar/main.zeek
+# @TEST-EXEC: echo 'event zeek_init() &priority=1 { print "baz"; }' >baz/main.zeek
+
+# @TEST-EXEC: echo "@load ./main" >common-load.zeek
+# @TEST-EXEC: ln common-load.zeek foo/__load__.zeek
+# @TEST-EXEC: ln common-load.zeek bar/__load__.zeek
+
+# @TEST-EXEC: echo "@load ./main" >baz/__load__.zeek
+# @TEST-EXEC: echo "@load ./main-sym" >>baz/__load__.zeek
+# @TEST-EXEC: (cd baz && ln -s main.zeek main-sym.zeek)
+
+# @TEST-EXEC: zeek -b foo bar baz foo/../foo bar/../bar baz/../baz $(pwd)/foo $(pwd)/bar $(pwd)/baz >out
+# @TEST-EXEC: btest-diff out