From f7c4d6ccc1fd3c452481a2d085486f8dec3860fb Mon Sep 17 00:00:00 2001
From: Thadeu Lima de Souza Cascardo <cascardo@cascardo.info>
Date: Thu, 10 Oct 2013 18:33:07 -0300
Subject: [PATCH] Respond pings with pongs.

Set the state of a friend as offline if timeout goes without receiving
PONG. If PING is received, send PONG. If PONG is received, set state as
online.
---
 friend.c  | 24 ++++++++++++++++++++++++
 friend.h  |  3 +++
 message.c | 16 +++++++++++++---
 message.h |  1 +
 4 files changed, 41 insertions(+), 3 deletions(-)

diff --git a/friend.c b/friend.c
index 68deccd..03d306d 100644
--- a/friend.c
+++ b/friend.c
@@ -27,11 +27,18 @@
 #include <stdio.h>
 #include "message.h"
 
+enum {
+	STATE_OFFLINE,
+	STATE_PINGED,
+	STATE_ONLINE,
+};
+
 struct friend {
 	char *name;
 	char *address;
 	uint16_t port;
 	GInetSocketAddress *saddr;
+	int state;
 };
 
 static GSocket *usock;
@@ -64,6 +71,22 @@ int friend_send_message(struct friend *friend, char *buffer, size_t len)
 	return 0;
 }
 
+void friend_timeout(struct friend *friend)
+{
+	if (friend->state == STATE_PINGED) {
+		friend->state = STATE_OFFLINE;
+	}
+}
+
+void friend_got_message(struct friend *friend, char *buffer, size_t len)
+{
+	if (len >= 4 && !strncmp(buffer, "PING", 4)) {
+		pong(friend);
+	} else if (len >= 4 && !strncmp(buffer, "PONG", 4)) {
+		friend->state = STATE_ONLINE;
+	}
+}
+
 struct cache {
 	GList *friends;
 };
@@ -123,6 +146,7 @@ int cache_add_friend(struct cache *cache, char *name, char *address, uint16_t po
 	g_object_unref(addr);
 	cache->friends = g_list_append(cache->friends, friend);
 	ping(friend);
+	friend->state = STATE_PINGED;
 	return 0;
 }
 
diff --git a/friend.h b/friend.h
index 76a22bd..efe5f65 100644
--- a/friend.h
+++ b/friend.h
@@ -38,4 +38,7 @@ struct friend *friend_get_by_address(GInetAddress *address, uint16_t port);
 
 char *friend_get_name();
 
+void friend_timeout(struct friend *friend);
+void friend_got_message(struct friend *friend, char *buffer, size_t len);
+
 #endif
diff --git a/message.c b/message.c
index 25b5160..8c6dafd 100644
--- a/message.c
+++ b/message.c
@@ -26,6 +26,7 @@
 gboolean ping_timeout(gpointer data)
 {
 	struct friend *friend = data;
+	friend_timeout(friend);
 	return G_SOURCE_REMOVE;
 }
 
@@ -58,7 +59,7 @@ gboolean message_incoming(GIOChannel *channel, GIOCondition cond, gpointer data)
 		friend = friend_get_by_address(iaddress, port);
 		if (friend) {
 			printf("got message from %s\n", friend_get_name(friend));
-			g_source_remove_by_user_data(friend);
+			friend_got_message(friend, buffer, len);
 		} else {
 			printf("could not find friend from address %s\n", g_inet_address_to_string(iaddress));
 		}
@@ -77,7 +78,16 @@ int message_init(GSocket *sock)
 
 int ping(struct friend *friend)
 {
+	int err;
 	char ping[5] = "PING";
-	friend_send_message(friend, ping, 4);
-	g_timeout_add(2000, ping_timeout, friend);
+	err = friend_send_message(friend, ping, 4);
+	if (!err)
+		g_timeout_add(2000, ping_timeout, friend);
+	return err;
+}
+
+int pong(struct friend *friend)
+{
+	char pong[5] = "PONG";
+	return friend_send_message(friend, pong, 4);
 }
diff --git a/message.h b/message.h
index d2fbcc1..cd018c9 100644
--- a/message.h
+++ b/message.h
@@ -24,5 +24,6 @@
 
 int message_init(GSocket *sock);
 int ping(struct friend *friend);
+int pong(struct friend *friend);
 
 #endif
-- 
2.20.1