From 12d03388626048c4e8136b2770ac3288b7eefc25 Mon Sep 17 00:00:00 2001
From: Gleb Mazovetskiy <glex.spb@gmail.com>
Date: Sat, 15 Feb 2020 16:28:42 +0000
Subject: [PATCH] dvlnet: Better error on packet type mismatch

---
 SourceX/dvlnet/packet.cpp  | 70 +++++++++++++++++++++++++++++++-------
 SourceX/dvlnet/packet.h    | 16 +++++++++
 SourceX/dvlnet/udp_p2p.cpp |  6 +++-
 3 files changed, 78 insertions(+), 14 deletions(-)

diff --git a/SourceX/dvlnet/packet.cpp b/SourceX/dvlnet/packet.cpp
index 8c822879c..5165b3268 100644
--- a/SourceX/dvlnet/packet.cpp
+++ b/SourceX/dvlnet/packet.cpp
@@ -7,6 +7,57 @@ namespace net {
 static constexpr bool disable_encryption = false;
 #endif
 
+const char *packet_type_to_string(uint8_t packet_type)
+{
+	switch (packet_type) {
+	case PT_MESSAGE:
+		return "PT_MESSAGE";
+	case PT_TURN:
+		return "PT_TURN";
+	case PT_JOIN_REQUEST:
+		return "PT_JOIN_REQUEST";
+	case PT_JOIN_ACCEPT:
+		return "PT_JOIN_ACCEPT";
+	case PT_CONNECT:
+		return "PT_CONNECT";
+	case PT_DISCONNECT:
+		return "PT_DISCONNECT";
+	default:
+		return nullptr;
+	}
+}
+
+wrong_packet_type_exception::wrong_packet_type_exception(std::initializer_list<packet_type> expected_types, std::uint8_t actual)
+{
+	message_ = "Expected packet of type ";
+	const auto append_packet_type = [this](std::uint8_t t) {
+		const char *type_str = packet_type_to_string(t);
+		if (type_str != nullptr)
+			message_.append(type_str);
+		else
+			message_.append(std::to_string(t));
+	};
+
+	constexpr char kJoinTypes[] = " or ";
+	for (const packet_type t : expected_types) {
+		append_packet_type(t);
+		message_.append(kJoinTypes);
+	}
+	message_.resize(message_.size() - (sizeof(kJoinTypes) - 1));
+	message_.append(", got");
+	append_packet_type(actual);
+}
+
+namespace {
+
+void CheckPacketTypeOneOf(std::initializer_list<packet_type> expected_types, std::uint8_t actual_type) {
+	for (std::uint8_t packet_type : expected_types)
+		if (actual_type == packet_type) return;
+	throw wrong_packet_type_exception(std::move(expected_types), actual_type);
+}
+
+} // namespace
+
 const buffer_t &packet::data()
 {
 	if (!have_decrypted || !have_encrypted)
@@ -39,8 +90,7 @@ const buffer_t &packet::message()
 {
 	if (!have_decrypted)
 		ABORT();
-	if (m_type != PT_MESSAGE)
-		throw packet_exception();
+	CheckPacketTypeOneOf({PT_MESSAGE}, m_type);
 	return m_message;
 }
 
@@ -48,8 +98,7 @@ turn_t packet::turn()
 {
 	if (!have_decrypted)
 		ABORT();
-	if (m_type != PT_TURN)
-		throw packet_exception();
+	CheckPacketTypeOneOf({PT_TURN}, m_type);
 	return m_turn;
 }
 
@@ -57,8 +106,7 @@ cookie_t packet::cookie()
 {
 	if (!have_decrypted)
 		ABORT();
-	if (m_type != PT_JOIN_REQUEST && m_type != PT_JOIN_ACCEPT)
-		throw packet_exception();
+	CheckPacketTypeOneOf({PT_JOIN_REQUEST, PT_JOIN_ACCEPT}, m_type);
 	return m_cookie;
 }
 
@@ -66,9 +114,7 @@ plr_t packet::newplr()
 {
 	if (!have_decrypted)
 		ABORT();
-	if (m_type != PT_JOIN_ACCEPT && m_type != PT_CONNECT
-		&& m_type != PT_DISCONNECT)
-		throw packet_exception();
+	CheckPacketTypeOneOf({PT_JOIN_ACCEPT, PT_CONNECT, PT_DISCONNECT}, m_type);
 	return m_newplr;
 }
 
@@ -76,8 +122,7 @@ const buffer_t &packet::info()
 {
 	if (!have_decrypted)
 		ABORT();
-	if (m_type != PT_JOIN_REQUEST && m_type != PT_JOIN_ACCEPT)
-		throw packet_exception();
+	CheckPacketTypeOneOf({PT_JOIN_REQUEST, PT_JOIN_ACCEPT}, m_type);
 	return m_info;
 }
 
@@ -85,8 +130,7 @@ leaveinfo_t packet::leaveinfo()
 {
 	if (!have_decrypted)
 		ABORT();
-	if (m_type != PT_DISCONNECT)
-		throw packet_exception();
+	CheckPacketTypeOneOf({PT_DISCONNECT}, m_type);
 	return m_leaveinfo;
 }
 
diff --git a/SourceX/dvlnet/packet.h b/SourceX/dvlnet/packet.h
index d5584e605..4f1e1e804 100644
--- a/SourceX/dvlnet/packet.h
+++ b/SourceX/dvlnet/packet.h
@@ -23,6 +23,9 @@ enum packet_type : uint8_t {
 	PT_DISCONNECT = 0x14,
 };
 
+// Returns nullptr for an invalid packet type.
+const char *packet_type_to_string(uint8_t packet_type);
+
 typedef uint8_t plr_t;
 typedef uint32_t cookie_t;
 typedef int turn_t;      // change int to something else in devilution code later
@@ -42,6 +45,19 @@ public:
 	}
 };
 
+class wrong_packet_type_exception : public packet_exception {
+public:
+	wrong_packet_type_exception(std::initializer_list<packet_type> expected_types, std::uint8_t actual);
+
+	const char *what() const throw() override
+	{
+		return message_.c_str();
+	}
+
+private:
+	std::string message_;
+};
+
 class packet {
 protected:
 	packet_type m_type;
diff --git a/SourceX/dvlnet/udp_p2p.cpp b/SourceX/dvlnet/udp_p2p.cpp
index 0a065704e..4a9d15fec 100644
--- a/SourceX/dvlnet/udp_p2p.cpp
+++ b/SourceX/dvlnet/udp_p2p.cpp
@@ -2,6 +2,10 @@
 
 #include <SDL.h>
 
+#ifdef USE_SDL1
+#include "sdl2_to_1_2_backports.h"
+#endif
+
 namespace dvl {
 namespace net {
 
@@ -92,7 +96,7 @@ void udp_p2p::recv()
 				auto pkt = pktfty->make_packet(pkt_buf);
 				recv_decrypted(*pkt, sender);
 			} catch (packet_exception &e) {
-				SDL_Log("Incorrect package size");
+				SDL_Log(e.what());
 				// drop packet
 			}
 		}