RE: Change IP address with libnm

[António Mendes <antonio mendes eid pt>]

Hi once again :)
I can finally see the print coming from connection_updated(). I added loop = g_main_loop_new(NULL, FALSE) and 
g_main_loop_run(loop) to my networkManager(). 
I still don't understand when you are saying to free GVariant returned from 
nm_remote_connection_commit_changes_finish(). In documentation, this function returns a gboolean.

Sorry for my noobish questions and thanks again for your help.

Code updated:

#include <glib.h>
#include <stdio.h>
#include <stdlib.h>

#include <NetworkManager.h>
#include <networkManagement.h>

static void connection_updated(GObject *connection,
                   GAsyncResult *result,
                   gpointer user_data)
{
    GMainLoop *loop = user_data;
    GError *error = NULL;
    gboolean success = FALSE;

    success = nm_remote_connection_commit_changes_finish(NM_REMOTE_CONNECTION(connection), result, &error);
    
    if (success == TRUE)
    {
        g_print("Connection Updated successfully\n");
    }
    else
    {
        g_print("Error updating connection: %s", error->message);
        g_error_free(error);
    }
    /* Tell the mainloop we're done and we can quit now */
    g_main_loop_quit(loop);
}

static void changeIpAddress(NMConnection *connection, GMainLoop *loop)
{
    GError *error = NULL;
    NMSettingIPConfig *s_ip4;
    NMIPAddress *address;

    /* Build up the 'ipv4' Setting */
    s_ip4 = NM_SETTING_IP_CONFIG(nm_setting_ip4_config_new());

    address = nm_ip_address_new(AF_INET, "192.168.123.2", 24, &error);
    if (address != NULL)
    {
        g_object_set(G_OBJECT(s_ip4),
                     NM_SETTING_IP_CONFIG_METHOD, NM_SETTING_IP4_CONFIG_METHOD_MANUAL,
                     NM_SETTING_IP_CONFIG_GATEWAY, "192.168.123.254",
                     NULL);

        nm_setting_ip_config_clear_addresses(s_ip4); //clear all addresses

        printf("%s\n", nm_ip_address_get_address(address));

        nm_setting_ip_config_add_address(s_ip4, address);

        g_object_set(G_OBJECT(s_ip4),
                     NM_SETTING_IP_CONFIG_GATEWAY, "192.168.123.254",
                     NULL);

        nm_connection_add_setting(connection, nm_setting_duplicate(NM_SETTING(s_ip4)));

        nm_remote_connection_commit_changes_async(NM_REMOTE_CONNECTION(connection),
                                                  TRUE, NULL, connection_updated, loop);
        nm_ip_address_unref(address);
    }
}

void networkManager()
{
    GError *error = NULL;
    NMConnection *connection;
    GMainLoop *loop;
    NMClient *client;

    loop = g_main_loop_new(NULL, FALSE);

    if (!(client = nm_client_new(NULL, &error)))
    {
        g_message("Error: Could not connect to NetworkManager: %s.", error->message);
        g_error_free(error);
        return;
    }

    if (!nm_client_get_nm_running(client))
    {
        g_message("Error: Can't obtain connections: NetworkManager is not running.");
        return;
    }

    connection = (NMConnection *)nm_client_get_connection_by_id(client, "Wired connection 2");

    changeIpAddress(connection, loop);

    g_main_loop_run(loop);

    g_object_unref(client);
}
________________________________________
From: Thomas Haller <thaller redhat com>
Sent: 26 February 2020 16:20
To: António Mendes; networkmanager-list gnome org
Subject: Re: Change IP address with libnm

On Wed, 2020-02-26 at 16:02 +0000, António Mendes wrote:
> Hello again Thomas.
>
> After read more documentation and follow your guidelines, I achieved
> my objective but if you can, I would appreciate a second opinion in
> the developed code, if you don't mind...

Hi,


You call nm_remote_connection_commit_changes_async(). That will
basically send the D-Bus request via D-Bus (to Update).

Usually, you would have your application to wait for the response from
commit_changes_async().

NMClient is build around GDBusConnection and thus GMainContext. That
means, when you start an async operation, you need to run/iterate the
maincontext for the response callback to be invoked. I think [1] is a
very good introduction to understand how this works.

> From the provided code it's not clear whether you are iterating the
main context (as you have to). However your networkManager() function
doesn't give the caller a way to know when the callback was invoked
(and whether it can stop waiting).


On a minor note, nm_remote_connection_commit_changes_finish() returns a
GVariant on success. You must free that. Also, you don't pass a
user_data argument to nm_remote_connection_commit_changes_async(),
so the g_object_unref(op) is wrong.


[1] https://developer.gnome.org/programming-guidelines/stable/main-contexts.html.en


best,
Thomas
www.eid.pt

EID, S.A.
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