Created a connection establishment API.

This API provides transparent asynchronous DNS lookups
with both IPv4 and IPv6 support, and in addition will try
to connect to all addresses until one of them work.

This implements the "happy eyeballs" algorithm provided that the client supports IPv6
and that the DNS records provides both IPv6 and IPv4 addresses.

src/network/connection.c

@@ -1,6 +1,6 @@
 /*
  * uhub - A tiny ADC p2p connection hub
- * Copyright (C) 2007-2012, Jan Vidar Krey
+ * Copyright (C) 2007-2013, Jan Vidar Krey
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -145,3 +145,364 @@ void net_con_callback(struct net_connection* con, int events)
 		con->callback(con, events, con->ptr);
 }
 
+struct net_connect_job
+{
+	struct net_connection* con;
+	struct net_connect_handle* handle;
+	struct sockaddr_storage addr;
+	struct net_connect_job* next;
+};
+
+struct net_connect_handle
+{
+	const char* address;
+	uint16_t port;
+	void* ptr;
+	net_connect_cb callback;
+	struct net_dns_job* dns;
+	const struct net_dns_result* result;
+	struct net_connect_job* job4;
+	struct net_connect_job* job6;
+};
+
+static void net_connect_callback(struct net_connect_handle* handle, enum net_connect_status status, struct net_connection* con);
+static void net_connect_job_internal_cb(struct net_connection* con, int event, void* ptr);
+
+/**
+ * Check if a connection job is completed.
+ * @return -1 on completed with an error, 0 on not yet completed, or 1 if completed successfully (connected).
+ */
+static int net_connect_job_check(struct net_connect_job* job)
+{
+	struct net_connection* con = job->con;
+	int af = job->addr.ss_family;
+	enum net_connect_status status;
+
+	int ret = net_connect(net_con_get_sd(con), (struct sockaddr*) &job->addr, af == AF_INET ? sizeof(struct sockaddr_in6) : sizeof(struct sockaddr_in));
+	if (ret == 0 || (ret == -1 && net_error() == EISCONN))
+	{
+		LOG_TRACE("net_connect_job_check(): Socket connected!");
+		job->con = NULL;
+		net_connect_callback(job->handle, net_connect_status_ok, con);
+		return 1;
+	}
+	else if (ret == -1 && (net_error() == EALREADY || net_error() == EINPROGRESS || net_error() == EWOULDBLOCK || net_error() == EINTR))
+	{
+		return 0;
+	}
+	LOG_TRACE("net_connect_job_check(): Socket error!");
+
+	switch (net_error())
+	{
+		case ECONNREFUSED:
+			status = net_connect_status_refused;
+			break;
+		case ENETUNREACH:
+			status = net_connect_status_unreachable;
+			break;
+
+		default:
+			status = net_connect_status_socket_error;
+	}
+
+	net_connect_callback(job->handle, status, NULL);
+	return -1;
+}
+
+static void net_connect_job_free(struct net_connect_job* job)
+{
+	if (job->con)
+		net_con_close(job->con);
+	job->handle = NULL;
+	job->next = NULL;
+	hub_free(job);
+}
+
+static void net_connect_job_stop(struct net_connect_job* job)
+{
+	if (job->addr.ss_family == AF_INET6)
+	{
+		job->handle->job6 = job->next;
+	}
+	else
+	{
+		job->handle->job4 = job->next;
+	}
+
+	net_connect_job_free(job);
+}
+
+static int net_connect_depleted(struct net_connect_handle* handle)
+{
+	return (!handle->job6 && !handle->job4);
+}
+
+static int net_connect_job_process(struct net_connect_job* job)
+{
+	int sd;
+	if (!job->con)
+	{
+		sd = net_socket_create(job->addr.ss_family, SOCK_STREAM, IPPROTO_TCP);
+		if (sd == -1)
+		{
+			LOG_DEBUG("net_connect_job_process: Unable to create socket!");
+			net_connect_callback(job->handle, net_connect_status_socket_error, NULL);
+			return -1; // FIXME
+		}
+
+		job->con = 	net_con_create();
+		net_con_initialize(job->con, sd, net_connect_job_internal_cb, job, NET_EVENT_WRITE);
+		net_con_set_timeout(job->con, TIMEOUT_CONNECTED); // FIXME: Use a proper timeout value!
+	}
+
+	return net_connect_job_check(job);
+}
+
+
+/*
+ * Internal callback used to establish an outbound connection.
+ */
+static void net_connect_job_internal_cb(struct net_connection* con, int event, void* ptr)
+{
+	int ret;
+	struct net_connect_job* job = net_con_get_ptr(con);
+	struct net_connect_job* next_job = job->next;
+	struct net_connect_handle* handle = job->handle;
+
+	if (event == NET_EVENT_TIMEOUT)
+	{
+		// FIXME: Try next address, or if no more addresses left declare failure to connect.
+		if (job->addr.ss_family == AF_INET6)
+		{
+			net_connect_job_stop(job);
+
+			if (!next_job)
+			{
+				LOG_TRACE("No more IPv6 addresses to try!");
+			}
+
+		}
+		else
+		{
+			net_connect_job_stop(job);
+
+			if (!next_job)
+			{
+				LOG_TRACE("No more IPv4 addresses to try!");
+			}
+		}
+
+		if (net_connect_depleted(handle))
+		{
+			LOG_TRACE("No more addresses left. Unable to connect!");
+			net_connect_callback(handle, net_connect_status_timeout, NULL);
+		}
+		return;
+	}
+
+	if (event == NET_EVENT_WRITE)
+	{
+		net_connect_job_process(job);
+	}
+}
+
+
+static int net_connect_cancel(struct net_connect_handle* handle)
+{
+	struct net_connect_job* job;
+
+	job = handle->job6;
+	while (job)
+	{
+		job = job->next;
+		net_connect_job_free(handle->job6);
+		handle->job6 = job;
+	}
+
+	job = handle->job4;
+	while (job)
+	{
+		job = job->next;
+		net_connect_job_free(handle->job4);
+		handle->job4 = job;
+	}
+}
+
+
+static int net_connect_process_queue(struct net_connect_handle* handle, struct net_connect_job* job)
+{
+	int ret;
+	while (job)
+	{
+		ret = net_connect_job_process(job);
+		if (ret < 0)
+		{
+			net_connect_job_stop(job);
+			continue;
+		}
+		else if (ret == 0)
+		{
+			// Need to process again
+			return 0;
+		}
+		else
+		{
+			// FIXME: Success!
+			return 1;
+		}
+	}
+	return -1;
+}
+
+static int net_connect_process(struct net_connect_handle* handle)
+{
+	int ret4, ret6;
+
+	ret6 = net_connect_process_queue(handle, handle->job6);
+	if (ret6 == 1)
+		return 1; // Connected - cool!
+
+	net_connect_process_queue(handle, handle->job4);
+}
+
+
+static int net_connect_job_schedule(struct net_connect_handle* handle, struct ip_addr_encap* addr)
+{
+	struct net_connect_job* job;
+	struct sockaddr_in* addr4;
+	struct sockaddr_in6* addr6;
+
+	if (addr->af == AF_INET6 && !net_is_ipv6_supported())
+	{
+		LOG_TRACE("net_connect_job_schedule(): Skipping IPv6 support since IPv6 is not supported.");
+		return 0;
+	}
+	else
+	{
+		job = hub_malloc_zero(sizeof(struct net_connect_job));
+		job->handle = handle;
+		if (addr->af == AF_INET6)
+		{
+			addr6 = (struct sockaddr_in6*) &job->addr;
+			LOG_TRACE("net_connect_job_schedule(): Scheduling IPv6 connect job.");
+			addr6->sin6_family = AF_INET6;
+			addr6->sin6_port = htons(handle->port);
+			memcpy(&addr6->sin6_addr, &addr->internal_ip_data.in6, sizeof(struct in6_addr));
+
+			// prepend
+			job->next = handle->job6;
+			handle->job6 = job;
+		}
+		else
+		{
+			addr4 = (struct sockaddr_in*) &job->addr;
+			LOG_TRACE("net_connect_job_schedule(): Scheduling IPv4 connect job.");
+			addr4->sin_family = AF_INET;
+			addr4->sin_port = htons(handle->port);
+			memcpy(&addr4->sin_addr, &addr->internal_ip_data.in, sizeof(struct in_addr));
+
+			// prepend
+			job->next = handle->job4;
+			handle->job4 = job;
+		}
+	}
+	return 1;
+}
+
+
+/*
+ * Callback when the DNS results are ready.
+ * Create a list of IPv6 and IPv4 addresses, then
+ * start connecting to them one by one until one succeeds.
+ */
+static int net_con_connect_dns_callback(struct net_dns_job* job, const struct net_dns_result* result)
+{
+	struct ip_addr_encap* addr;
+	struct net_connect_handle* handle = (struct net_connect_handle*) net_dns_job_get_ptr(job);
+	handle->dns = NULL;
+	size_t usable = 0;
+	int ret;
+
+	LOG_TRACE("net_con_connect(): async - Got DNS results");
+	if (!result)
+	{
+		LOG_DEBUG("net_con_connect() - Unable to lookup host!");
+		net_connect_callback(handle, net_connect_status_dns_error, NULL);
+		return 1;
+	}
+
+	if (!net_dns_result_size(result))
+	{
+		LOG_DEBUG("net_con_connect() - Host not found!");
+		net_connect_callback(handle, net_connect_status_host_not_found, NULL);
+		return 1;
+	}
+
+	handle->result = result;
+
+	// Extract results into a separate list of IPv4 and IPv6 addresses.
+	addr = net_dns_result_first(result);
+	while (addr)
+	{
+		if (net_connect_job_schedule(handle, addr))
+			usable++;
+		addr = net_dns_result_next(result);
+	}
+
+	net_connect_process(handle);
+
+	return 0;
+}
+
+// typedef void (*net_connect_cb)(struct net_connect_handle*, enum net_connect_handle_code, struct net_connection* con);
+
+struct net_connect_handle* net_con_connect(const char* address, uint16_t port, net_connect_cb callback, void* ptr)
+{
+	struct net_connect_handle* handle = hub_malloc_zero(sizeof(struct net_connect_handle));
+
+	handle->address = hub_strdup(address);
+	handle->port = port;
+	handle->ptr = ptr;
+	handle->callback = callback;
+
+	// FIXME: Check if DNS resolving is necessary ?
+	handle->dns = net_dns_gethostbyname(address, AF_UNSPEC, net_con_connect_dns_callback, handle);
+	if (!handle->dns)
+	{
+		LOG_TRACE("net_con_connect(): Unable to create DNS lookup job.");
+		hub_free((char*) handle->address);
+		hub_free(handle);
+		return NULL;
+	}
+
+	return handle;
+}
+
+void net_connect_destroy(struct net_connect_handle* handle)
+{
+	hub_free((char*) handle->address);
+
+	// cancel DNS job if pending
+	if (handle->dns)
+		net_dns_job_cancel(handle->dns);
+
+	// Stop any connect jobs.
+	net_connect_cancel(handle);
+
+	// free any DNS results
+	net_dns_result_free(handle->result);
+
+	hub_free(handle);
+}
+
+static void net_connect_callback(struct net_connect_handle* handle, enum net_connect_status status, struct net_connection* con)
+{
+	uhub_assert(handle->callback != NULL);
+
+	// Call the callback
+	handle->callback(handle, status, con, handle->ptr);
+	handle->callback = NULL;
+
+	// Cleanup
+	net_connect_destroy(handle);
+}

src/network/connection.h

@@ -1,6 +1,6 @@
 /*
  * uhub - A tiny ADC p2p connection hub
- * Copyright (C) 2007-2012, Jan Vidar Krey
+ * Copyright (C) 2007-2013, Jan Vidar Krey
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -34,10 +34,41 @@ struct net_connection
 	NET_CON_STRUCT_COMMON
 };
 
+struct net_connect_handle;
+
+enum net_connect_status
+{
+	net_connect_status_ok = 0,
+	net_connect_status_host_not_found = -1,
+	net_connect_status_no_address = -2,
+	net_connect_status_dns_error = -3,
+	net_connect_status_refused = -4,
+	net_connect_status_unreachable = -5,
+	net_connect_status_timeout = -6,
+	net_connect_status_socket_error = -7,
+};
+
+typedef void (*net_connect_cb)(struct net_connect_handle*, enum net_connect_status status, struct net_connection* con, void* ptr);
+
 extern int   net_con_get_sd(struct net_connection* con);
 extern void* net_con_get_ptr(struct net_connection* con);
 
 extern struct net_connection* net_con_create();
+
+/**
+ * Establish an outbound TCP connection.
+ * This will resolve the IP-addresses, and connect to
+ * either an IPv4 or IPv6 address depending if it is supported,
+ * and using the happy eyeballs algorithm.
+ *
+ * @param address Hostname, IPv4 or IPv6 address
+ * @param port TCP port number
+ * @param callback A callback to be called once the connection is established, or failed.
+ * @returns a handle to the connection establishment job, or NULL if an immediate error.
+ */
+extern struct net_connect_handle* net_con_connect(const char* address, uint16_t port, net_connect_cb callback, void* ptr);
+extern void net_connect_destroy(struct net_connect_handle* handle);
+
 extern void net_con_destroy(struct net_connection*);
 extern void net_con_initialize(struct net_connection* con, int sd, net_connection_cb callback, const void* ptr, int events);
 extern void net_con_reinitialize(struct net_connection* con, net_connection_cb callback, const void* ptr, int events);

src/network/dnsresolver.c

@@ -1,6 +1,6 @@
 /*
  * uhub - A tiny ADC p2p connection hub
- * Copyright (C) 2007-2012, Jan Vidar Krey
+ * Copyright (C) 2007-2013, Jan Vidar Krey
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -366,21 +366,24 @@ extern size_t net_dns_result_size(const struct net_dns_result* res)
 extern struct ip_addr_encap* net_dns_result_first(const struct net_dns_result* res)
 {
 	struct ip_addr_encap* ipaddr = list_get_first(res->addr_list);
-	LOG_TRACE("net_dns_result_first() - Address: %s", ip_convert_to_string(ipaddr));
+	LOG_TRACE("net_dns_result_first() - Address: %s", ipaddr ? ip_convert_to_string(ipaddr) : "(no address)");
 	return ipaddr;
 }
 
 extern struct ip_addr_encap* net_dns_result_next(const struct net_dns_result* res)
 {
 	struct ip_addr_encap* ipaddr = list_get_next(res->addr_list);
-	LOG_TRACE("net_dns_result_next() - Address: %s", ip_convert_to_string(ipaddr));
+	LOG_TRACE("net_dns_result_next() - Address: %s", ipaddr ? ip_convert_to_string(ipaddr) : "(no more addresses)");
 	return ipaddr;
 }
 
-extern void net_dns_result_free(struct net_dns_result* res)
+extern void net_dns_result_free(const struct net_dns_result* res)
 {
+	if (!res)
+		return;
+
 	list_clear(res->addr_list, &hub_free);
 	list_destroy(res->addr_list);
 	free_job(res->job);
-	hub_free(res);
+	hub_free((struct net_dns_result*) res);
 }

src/network/dnsresolver.h

@@ -1,6 +1,6 @@
 /*
  * uhub - A tiny ADC p2p connection hub
- * Copyright (C) 2007-2012, Jan Vidar Krey
+ * Copyright (C) 2007-2013, Jan Vidar Krey
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -114,6 +114,6 @@ extern struct ip_addr_encap* net_dns_result_first(const struct net_dns_result*);
 extern struct ip_addr_encap* net_dns_result_next(const struct net_dns_result*);
 
 /// When finished with the results
-extern void net_dns_result_free(struct net_dns_result*);
+extern void net_dns_result_free(const struct net_dns_result*);
 
 #endif /* HAVE_UHUB_NETWORK_DNS_RESOLVER_H */