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iiod: allow multiple "iio" services to be published on DNS-SD
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This fixes #402 by handling more error codes in iiod for avahi.
and more closely matches libavahi examples.

This seems to work for me, I tried creating a few network
contexts, and didn't have any issues finding the various ones,
things were re-named properly if/when collisions happened.

Signed-off-by: Robin Getz <[email protected]>
Signed-off-by: Matej Kenda <[email protected]>
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@rgetz
rgetz committed Mar 20, 2020
1 parent 5e58241 commit f7313ce
Showing 1 changed file with 229 additions and 24 deletions.
253 changes: 229 additions & 24 deletions iiod/iiod.c
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Original file line number Diff line number Diff line change
Expand Up @@ -39,9 +39,13 @@
#include <unistd.h>

#ifdef HAVE_AVAHI
#include <avahi-common/simple-watch.h>
#include <avahi-common/thread-watch.h>
#include <avahi-common/error.h>
#include <avahi-common/alternative.h>
#include <avahi-common/malloc.h>
#include <avahi-client/client.h>
#include <avahi-client/publish.h>
#include <avahi-common/domain.h>
#endif

#define MY_NAME "iiod"
Expand Down Expand Up @@ -106,57 +110,257 @@ static const char *options_descriptions[] = {
};

#ifdef HAVE_AVAHI
static AvahiSimplePoll *avahi_poll;
static AvahiClient *avahi_client;

/***
* Parts of the avahi code are borrowed from the client-publish-service.c
* https://www.avahi.org/doxygen/html/client-publish-service_8c-example.html
* which is an example in the avahi library. Copyright Lennart Poettering
* released under the LGPL 2.1 or (at your option) any later version.
*/

/* Global Data */

static struct avahi_data {
AvahiThreadedPoll *poll;
AvahiClient *client;
AvahiEntryGroup *group;
char * name;
} avahi;

static void create_services(AvahiClient *c);
static AvahiClient * client_new(void);

static void client_free()
{
/* This also frees the entry group, if any. */
if (avahi.client) {
avahi_client_free(avahi.client);
avahi.client = NULL;
avahi.group = NULL;
}
}

static void shutdown_avahi()
{
/* Stop the avahi client, if it's running. */
if (avahi.poll)
avahi_threaded_poll_stop(avahi.poll);

/* Clean up the avahi objects. The order is significant. */
client_free();
if (avahi.poll) {
avahi_threaded_poll_free(avahi.poll);
avahi.poll = NULL;
}
if (avahi.name) {
INFO("Avahi: Removing service '%s'\n", avahi.name);
avahi_free(avahi.name);
avahi.name = NULL;
}
}

static void __avahi_group_cb(AvahiEntryGroup *group,
AvahiEntryGroupState state, void *d)
{
/* Called whenever the entry group state changes */
if (!group) {
ERROR("__avahi_group_cb with no valid group\n");
return;
}

avahi.group = group;

switch (state) {
case AVAHI_ENTRY_GROUP_ESTABLISHED :
INFO("Avahi: Service '%s' successfully established.\n",
avahi.name);
break;
case AVAHI_ENTRY_GROUP_COLLISION : {
char *n;
/* A service name collision, pick a new name */
n = avahi_alternative_service_name(avahi.name);
avahi_free(avahi.name);
avahi.name = n;
INFO("Avahi: Group Service name collision, renaming service to '%s'\n",
avahi.name);
create_services(avahi_entry_group_get_client(group));
break;
}
case AVAHI_ENTRY_GROUP_FAILURE :
ERROR("Entry group failure: %s\n",
avahi_strerror(avahi_client_errno(
avahi_entry_group_get_client(group))));
break;
case AVAHI_ENTRY_GROUP_UNCOMMITED:
/* This is normal,
* since we commit things in the create_services()
*/
DEBUG("Avahi: Group uncommited\n");
break;
case AVAHI_ENTRY_GROUP_REGISTERING:
DEBUG("Avahi: Group registering\n");
break;
}
}

static void __avahi_client_cb(AvahiClient *client,
AvahiClientState state, void *d)
{
AvahiEntryGroup *group;

if (state != AVAHI_CLIENT_S_RUNNING)
if (!client) {
ERROR("__avahi_client_cb with no valid client\n");
return;
}

group = avahi_entry_group_new(client, __avahi_group_cb, NULL);
switch (state) {
case AVAHI_CLIENT_S_RUNNING:
/* Same as AVAHI_SERVER_RUNNING */
DEBUG("Avahi: create services\n");
/* The server has startup successfully, so create our services */
create_services(client);
break;
case AVAHI_CLIENT_FAILURE:
ERROR("Avahi: Client failure: %s\n",
avahi_strerror(avahi_client_errno(client)));
client_free();
avahi.client = client_new();
break;
case AVAHI_CLIENT_S_COLLISION:
/* Same as AVAHI_SERVER_COLLISION */
/* When the server is back in AVAHI_SERVER_RUNNING state
* we will register them again with the new host name. */
DEBUG("Avahi: Client collision\n");
/* Let's drop our registered services.*/
if (avahi.group)
avahi_entry_group_reset(avahi.group);
break;
case AVAHI_CLIENT_S_REGISTERING:
/* Same as AVAHI_SERVER_REGISTERING */
DEBUG("Avahi: Client group reset\n");
if (avahi.group)
avahi_entry_group_reset(avahi.group);
break;
case AVAHI_CLIENT_CONNECTING:
DEBUG("Avahi: Client Connecting\n");
break;
}

/* NOTE: group is freed by avahi_client_free */
}

if (group && !avahi_entry_group_add_service(group,
static AvahiClient * client_new(void)
{
int ret;
AvahiClient * client;

client = avahi_client_new(avahi_threaded_poll_get(avahi.poll),
0, __avahi_client_cb, NULL, &ret);
if (!client) {
ERROR("Avahi: failure creating client: %s (%d)\n",
avahi_strerror(ret), ret);
}

return client;
}


static void create_services(AvahiClient *c)
{
int ret;

if (!c) {
ERROR("create_services called with no valid client\n");
goto fail;
}

if (!avahi.group) {
avahi.group = avahi_entry_group_new(c, __avahi_group_cb, NULL);
if (!avahi.group) {
ERROR("avahi_entry_group_new() failed: %s\n",
avahi_strerror(avahi_client_errno(c)));
goto fail;
}
}

if (!avahi_entry_group_is_empty(avahi.group)) {
DEBUG("Avahi group not empty\n");
return;
}

ret = avahi_entry_group_add_service(avahi.group,
AVAHI_IF_UNSPEC, AVAHI_PROTO_UNSPEC,
0, "iio", "_iio._tcp", NULL, NULL, IIOD_PORT, NULL)) {
avahi_entry_group_commit(group);
INFO("Registered to ZeroConf server %s\n",
avahi_client_get_version_string(client));
0, avahi.name, "_iio._tcp", NULL, NULL, IIOD_PORT, NULL);
if (ret < 0) {
if (ret == AVAHI_ERR_COLLISION) {
char *n;
n = avahi_alternative_service_name(avahi.name);
avahi_free(avahi.name);
avahi.name = n;
DEBUG("Service name collision, renaming service to '%s'\n",
avahi.name);
avahi_entry_group_reset(avahi.group);
create_services(c);
return;
}
ERROR("Failed to add _iio._tcp service: %s\n", avahi_strerror(ret));
goto fail;
}

/* NOTE: group is freed by avahi_client_free */
ret = avahi_entry_group_commit(avahi.group);
if (ret < 0) {
ERROR("Failed to commit entry group: %s\n", avahi_strerror(ret));
goto fail;
}

INFO("Avahi: Registered '%s' to ZeroConf server %s\n",
avahi.name, avahi_client_get_version_string(c));

return;

fail:
avahi_entry_group_reset(avahi.group);
}

#define IIOD_ON "iiod on "

static int start_avahi(void)
{
int ret = ENOMEM;
char label[AVAHI_LABEL_MAX];
char host[AVAHI_LABEL_MAX - sizeof(IIOD_ON)];

ret = gethostname(host, sizeof(host));
if (!ret) {
snprintf(label, sizeof(label), IIOD_ON "%s", host);
} else {
snprintf(label, sizeof(label), "iiod");
}

avahi_poll = avahi_simple_poll_new();
if (!avahi_poll)
avahi.name = avahi_strdup(label);
if (!avahi.name)
return -ENOMEM;

avahi_client = avahi_client_new(avahi_simple_poll_get(avahi_poll),
0, __avahi_client_cb, NULL, &ret);
if (!avahi_client) {
avahi_simple_poll_free(avahi_poll);
return -ret;
avahi.poll = avahi_threaded_poll_new();
if (!avahi.poll) {
shutdown_avahi();
return -ENOMEM;
}

avahi.client = client_new();
if (!avahi.client) {
shutdown_avahi();
return -ENOMEM;
}

avahi_threaded_poll_start(avahi.poll);
INFO("Avahi: Started.\n");

return 0;
}

static void stop_avahi(void)
{
avahi_client_free(avahi_client);
avahi_simple_poll_free(avahi_poll);
shutdown_avahi();
INFO("Avahi: Stopped\n");
}
#endif /* HAVE_AVAHI */

Expand Down Expand Up @@ -226,8 +430,9 @@ static int main_server(struct iio_context *ctx, bool debug)
bool avahi_started;
#endif

INFO("Starting IIO Daemon version %u.%u\n",
LIBIIO_VERSION_MAJOR, LIBIIO_VERSION_MINOR);
INFO("Starting IIO Daemon version %u.%u.%s\n",
LIBIIO_VERSION_MAJOR, LIBIIO_VERSION_MINOR,
LIBIIO_VERSION_GIT);

#ifdef HAVE_IPV6
fd = socket(AF_INET6, SOCK_STREAM | SOCK_NONBLOCK, 0);
Expand Down

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