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direwolf/src/dns_sd_avahi.c

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//
// This file is part of Dire Wolf, an amateur radio packet TNC.
//
// Copyright (C) 2020 Heikki Hannikainen, OH7LZB
//
//
// 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
// the Free Software Foundation, either version 2 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
/*------------------------------------------------------------------
*
* Module: dns_sd_avahi.c
*
* Purpose: Announce the KISS over TCP service using DNS-SD via Avahi
*
* Description:
*
* Most people have typed in enough IP addresses and ports by now, and
* would rather just select an available TNC that is automatically
* discovered on the local network. Even more so on a mobile device
* such an Android or iOS phone or tablet.
*
* On Linux, the announcement can be made through Avahi, the mDNS
* framework commonly deployed on Linux systems.
*
* This is largely based on the publishing example of the Avahi library.
*/
#ifdef USE_AVAHI_CLIENT
#include <stdlib.h>
#include <stdio.h>
#include <pthread.h>
#include <avahi-client/client.h>
#include <avahi-client/publish.h>
#include <avahi-common/simple-watch.h>
#include <avahi-common/alternative.h>
#include <avahi-common/malloc.h>
#include <avahi-common/error.h>
#include "dns_sd_dw.h"
#include "dns_sd_common.h"
#include "textcolor.h"
static AvahiEntryGroup *group = NULL;
static AvahiSimplePoll *simple_poll = NULL;
static AvahiClient *client = NULL;
static char *name = NULL;
static int kiss_port = 0;
pthread_t avahi_thread;
static void create_services(AvahiClient *c);
#define PRINT_PREFIX "DNS-SD: Avahi: "
static void entry_group_callback(AvahiEntryGroup *g, AvahiEntryGroupState state, AVAHI_GCC_UNUSED void *userdata)
{
assert(g == group || group == NULL);
group = g;
/* Called whenever the entry group state changes */
switch (state) {
case AVAHI_ENTRY_GROUP_ESTABLISHED :
/* The entry group has been established successfully */
text_color_set(DW_COLOR_INFO);
dw_printf(PRINT_PREFIX "Service '%s' successfully registered.\n", name);
break;
case AVAHI_ENTRY_GROUP_COLLISION: {
char *n;
/* A service name collision with a remote service
* happened. Let's pick a new name. */
n = avahi_alternative_service_name(name);
avahi_free(name);
name = n;
text_color_set(DW_COLOR_INFO);
dw_printf(PRINT_PREFIX "Service name collision, renaming service to '%s'\n", name);
/* And recreate the services */
create_services(avahi_entry_group_get_client(g));
break;
}
case AVAHI_ENTRY_GROUP_FAILURE:
text_color_set(DW_COLOR_ERROR);
dw_printf(PRINT_PREFIX "Entry group failure: %s\n", avahi_strerror(avahi_client_errno(avahi_entry_group_get_client(g))));
/* Some kind of failure happened while we were registering our services */
avahi_simple_poll_quit(simple_poll);
break;
case AVAHI_ENTRY_GROUP_UNCOMMITED:
case AVAHI_ENTRY_GROUP_REGISTERING:
;
}
}
static void create_services(AvahiClient *c)
{
char *n;
int ret;
assert(c);
/* If this is the first time we're called, let's create a new
* entry group if necessary */
if (!group) {
if (!(group = avahi_entry_group_new(c, entry_group_callback, NULL))) {
text_color_set(DW_COLOR_ERROR);
dw_printf(PRINT_PREFIX "avahi_entry_group_new() failed: %s\n", avahi_strerror(avahi_client_errno(c)));
goto fail;
}
} else {
avahi_entry_group_reset(group);
}
/* If the group is empty (either because it was just created, or
* because it was reset previously, add our entries. */
if (avahi_entry_group_is_empty(group)) {
text_color_set(DW_COLOR_INFO);
dw_printf(PRINT_PREFIX "Announcing KISS TCP on port %d as '%s'\n", kiss_port, name);
/* Announce with AVAHI_PROTO_INET instead of AVAHI_PROTO_UNSPEC, since Dire Wolf currently
* only listens on IPv4.
*/
if ((ret = avahi_entry_group_add_service(group, AVAHI_IF_UNSPEC, AVAHI_PROTO_INET, 0, name, DNS_SD_SERVICE, NULL, NULL, kiss_port, NULL)) < 0) {
if (ret == AVAHI_ERR_COLLISION)
goto collision;
text_color_set(DW_COLOR_ERROR);
dw_printf(PRINT_PREFIX "Failed to add _kiss-tnc._tcp service: %s\n", avahi_strerror(ret));
goto fail;
}
/* Tell the server to register the service */
if ((ret = avahi_entry_group_commit(group)) < 0) {
text_color_set(DW_COLOR_ERROR);
dw_printf(PRINT_PREFIX "Failed to commit entry group: %s\n", avahi_strerror(ret));
goto fail;
}
}
return;
collision:
/* A service name collision with a local service happened. Let's
* pick a new name */
n = avahi_alternative_service_name(name);
avahi_free(name);
name = n;
text_color_set(DW_COLOR_INFO);
dw_printf(PRINT_PREFIX "Service name collision, renaming service to '%s'\n", name);
avahi_entry_group_reset(group);
create_services(c);
return;
fail:
avahi_simple_poll_quit(simple_poll);
}
static void client_callback(AvahiClient *c, AvahiClientState state, AVAHI_GCC_UNUSED void * userdata)
{
assert(c);
/* Called whenever the client or server state changes */
switch (state) {
case AVAHI_CLIENT_S_RUNNING:
/* The server has startup successfully and registered its host
* name on the network, so it's time to create our services */
create_services(c);
break;
case AVAHI_CLIENT_FAILURE:
text_color_set(DW_COLOR_ERROR);
dw_printf(PRINT_PREFIX "Client failure: %s\n", avahi_strerror(avahi_client_errno(c)));
avahi_simple_poll_quit(simple_poll);
break;
case AVAHI_CLIENT_S_COLLISION:
/* Let's drop our registered services. When the server is back
* in AVAHI_SERVER_RUNNING state we will register them
* again with the new host name. */
case AVAHI_CLIENT_S_REGISTERING:
/* The server records are now being established. This
* might be caused by a host name change. We need to wait
* for our own records to register until the host name is
* properly esatblished. */
if (group)
avahi_entry_group_reset(group);
break;
case AVAHI_CLIENT_CONNECTING:
;
}
}
static void cleanup(void)
{
/* Cleanup things */
if (client)
avahi_client_free(client);
if (simple_poll)
avahi_simple_poll_free(simple_poll);
avahi_free(name);
}
static void *avahi_mainloop(void *arg)
{
/* Run the main loop */
avahi_simple_poll_loop(simple_poll);
cleanup();
return NULL;
}
void dns_sd_announce (struct misc_config_s *mc)
{
text_color_set(DW_COLOR_DEBUG);
//kiss_port = mc->kiss_port; // now an array.
kiss_port = mc->kiss_port[0]; // FIXME: Quick hack until I can handle multiple TCP ports properly.
int error;
/* Allocate main loop object */
if (!(simple_poll = avahi_simple_poll_new())) {
text_color_set(DW_COLOR_ERROR);
dw_printf(PRINT_PREFIX "Failed to create Avahi simple poll object.\n");
goto fail;
}
if (mc->dns_sd_name[0]) {
name = avahi_strdup(mc->dns_sd_name);
} else {
name = dns_sd_default_service_name();
}
/* Allocate a new client */
client = avahi_client_new(avahi_simple_poll_get(simple_poll), 0, client_callback, NULL, &error);
/* Check whether creating the client object succeeded */
if (!client) {
text_color_set(DW_COLOR_ERROR);
dw_printf(PRINT_PREFIX "Failed to create Avahi client: %s\n", avahi_strerror(error));
goto fail;
}
pthread_create(&avahi_thread, NULL, &avahi_mainloop, NULL);
return;
fail:
cleanup();
}
#endif // USE_AVAHI_CLIENT
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