[vlc-devel] [PATCH 6/7] mdns: Add basic ip address detection (Linux)

[Rémi Denis-Courmont]

Le keskiviikkona 24. heinäkuuta 2019, 18.43.49 EEST Roland Bewick a écrit :
> ---
>  modules/services_discovery/microdns.c | 62
> +++++++++++++++++++++++++++++++++-- 1 file changed, 59 insertions(+), 3
> deletions(-)
> 
> diff --git a/modules/services_discovery/microdns.c
> b/modules/services_discovery/microdns.c index c460126b58..fa34ffa8d8 100644
> --- a/modules/services_discovery/microdns.c
> +++ b/modules/services_discovery/microdns.c
> @@ -28,6 +28,12 @@
>  #include <stdatomic.h>
>  #include <assert.h>
> 
> +#if defined( _WIN32 )
> +
> +#else
> +    #include <ifaddrs.h>
> +#endif
> +
>  #include <vlc_common.h>
>  #include <vlc_plugin.h>
>  #include <vlc_modules.h>
> @@ -868,9 +874,59 @@ CloseRD( vlc_object_t *p_this )
>      CleanDiscoveryCommon( p_sys );
>  }
> 
> -static char * detect_ip_address()
> +static char * detect_ip_address( vlc_object_t *p_obj )
>  {
> -    return strdup("127.0.0.1"); /* TODO: actually detect ip address */
> +    char result[16] = "127.0.0.1";
> +    bool found = false;
> +#if defined( _WIN32 )
> +
> +#else
> +    struct ifaddrs *id;
> +    if( getifaddrs( &id ) == 0 )
> +    {
> +        int selected_priority = 0;
> +
> +        for( ; id != NULL; id = id->ifa_next )
> +        {
> +            if( id->ifa_addr->sa_family == AF_INET )
> +            {
> +                struct sockaddr_in *addr_in = (struct sockaddr_in
> *)id->ifa_addr; +
> +                char *ip_address = inet_ntoa( addr_in->sin_addr );
> +
> +                /* TODO: smarter priority function. */
> +                int priority = 0;
> +                if( strncmp( "eth0", id->ifa_name, strlen( "eth0" ) ) == 0
> ) +                {
> +                    priority = 1000;
> +                }
> +                else if( strncmp( "wifi0", id->ifa_name, strlen( "wifi0" )
> ) == 0 ) +                {
> +                    priority = 2000;
> +                }
> +
> +                msg_Dbg( p_obj, "Assigned interface %s priority %d",
> +                         id->ifa_name, priority);
> +
> +                if( priority > selected_priority )
> +                {
> +                    strcpy( result, ip_address );
> +                    selected_priority = priority;
> +                    found = true;
> +                }
> +            }
> +        }
> +    }
> +    else
> +    {
> +        msg_Err( p_obj, "Couldn't get interface addresses");
> +    }

That could have worked in the nineties. Machines, especially laptops, change 
IP addresses and have multiple addresses routinely nowadays, and Linux 
desktops interfaces are not always called eth0 or wifi0.

Besides, you need to respond with the correct IP address for the interface on 
which the request came, usually with IP_PKTINFO/IP6_PKTINFO if you use UDP.

-- 
Rémi Denis-Courmont
http://www.remlab.net/