Add support for mandatory tags in included config files

If the mandatory tag is not found in the included config, the rehash is aborted. This is especially useful for remote includes, as it allows users to have a dummy tag at the end of the included config to indicate that the config has been wholly read.
This method does not depend on exit codes so even situations where wget returns an empty or a wrong page that we would otherwise accept can be detected and an error can be generated before we assume that the contents have disappeared (and unload all modules, if the included file is supposed to contain module tags, for example).

Usage: <include ... mandatorytag="namehere"> - if the included config doesn't contain a <namehere> tag then the rehash is aborted

Fixes #30 reported by @Justasic

2 files changed, 23 insertions, 10 deletions

diff --git a/include/configparser.h b/include/configparser.h
index f44b7c8a5..999d79e24 100644
--- a/include/configparser.h
+++ b/include/configparser.h
@@ -51,8 +51,8 @@ struct ParseStack
 		vars["quot"] = "\"";
 		vars["newline"] = vars["nl"] = "\n";
 	}
-	bool ParseFile(const std::string& name, int flags);
-	bool ParseExec(const std::string& name, int flags);
+	bool ParseFile(const std::string& name, int flags, const std::string& mandatory_tag = "");
+	bool ParseExec(const std::string& name, int flags, const std::string& mandatory_tag = "");
 	void DoInclude(ConfigTag* includeTag, int flags);
 	void DoReadFile(const std::string& key, const std::string& file, int flags, bool exec);
 };
diff --git a/src/configparser.cpp b/src/configparser.cpp
index b6e3f7187..7d9eab651 100644
--- a/src/configparser.cpp
+++ b/src/configparser.cpp
@@ -30,9 +30,10 @@ struct Parser
 	fpos last_tag;
 	reference<ConfigTag> tag;
 	int ungot;
+	std::string mandatory_tag;
 
-	Parser(ParseStack& me, int myflags, FILE* conf, const std::string& name)
-		: stack(me), flags(myflags), file(conf), current(name), last_tag(name), ungot(-1)
+	Parser(ParseStack& me, int myflags, FILE* conf, const std::string& name, const std::string& mandatorytag)
+		: stack(me), flags(myflags), file(conf), current(name), last_tag(name), ungot(-1), mandatory_tag(mandatorytag)
 	{ }
 
 	int next(bool eof_ok = false)
@@ -184,6 +185,12 @@ struct Parser
 
 		while (kv(items, seen));
 
+		if (name == mandatory_tag)
+		{
+			// Found the mandatory tag
+			mandatory_tag.clear();
+		}
+
 		if (name == "include")
 		{
 			stack.DoInclude(tag, flags);
@@ -241,6 +248,8 @@ struct Parser
 				{
 					case EOF:
 						// this is the one place where an EOF is not an error
+						if (!mandatory_tag.empty())
+							throw CoreException("Mandatory tag \"" + mandatory_tag + "\" not found");
 						return true;
 					case '#':
 						comment();
@@ -277,6 +286,10 @@ void ParseStack::DoInclude(ConfigTag* tag, int flags)
 {
 	if (flags & FLAG_NO_INC)
 		throw CoreException("Invalid <include> tag in file included with noinclude=\"yes\"");
+
+	std::string mandatorytag;
+	tag->readString("mandatorytag", mandatorytag);
+
 	std::string name;
 	if (tag->readString("file", name))
 	{
@@ -284,7 +297,7 @@ void ParseStack::DoInclude(ConfigTag* tag, int flags)
 			flags |= FLAG_NO_INC;
 		if (tag->getBool("noexec", false))
 			flags |= FLAG_NO_EXEC;
-		if (!ParseFile(name, flags))
+		if (!ParseFile(name, flags, mandatorytag))
 			throw CoreException("Included");
 	}
 	else if (tag->readString("executable", name))
@@ -295,7 +308,7 @@ void ParseStack::DoInclude(ConfigTag* tag, int flags)
 			flags |= FLAG_NO_INC;
 		if (tag->getBool("noexec", true))
 			flags |= FLAG_NO_EXEC;
-		if (!ParseExec(name, flags))
+		if (!ParseExec(name, flags, mandatorytag))
 			throw CoreException("Included");
 	}
 }
@@ -327,7 +340,7 @@ void ParseStack::DoReadFile(const std::string& key, const std::string& name, int
 	}
 }
 
-bool ParseStack::ParseFile(const std::string& name, int flags)
+bool ParseStack::ParseFile(const std::string& name, int flags, const std::string& mandatory_tag)
 {
 	ServerInstance->Logs->Log("CONFIG", DEBUG, "Reading file %s", name.c_str());
 	for (unsigned int t = 0; t < reading.size(); t++)
@@ -345,13 +358,13 @@ bool ParseStack::ParseFile(const std::string& name, int flags)
 		throw CoreException("Could not read \"" + name + "\" for include");
 
 	reading.push_back(name);
-	Parser p(*this, flags, file, name);
+	Parser p(*this, flags, file, name, mandatory_tag);
 	bool ok = p.outer_parse();
 	reading.pop_back();
 	return ok;
 }
 
-bool ParseStack::ParseExec(const std::string& name, int flags)
+bool ParseStack::ParseExec(const std::string& name, int flags, const std::string& mandatory_tag)
 {
 	ServerInstance->Logs->Log("CONFIG", DEBUG, "Reading executable %s", name.c_str());
 	for (unsigned int t = 0; t < reading.size(); t++)
@@ -369,7 +382,7 @@ bool ParseStack::ParseExec(const std::string& name, int flags)
 		throw CoreException("Could not open executable \"" + name + "\" for include");
 
 	reading.push_back(name);
-	Parser p(*this, flags, file, name);
+	Parser p(*this, flags, file, name, mandatory_tag);
 	bool ok = p.outer_parse();
 	reading.pop_back();
 	return ok;