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

[Rémi Denis-Courmont]

Le keskiviikkona 24. heinäkuuta 2019, 19.10.50 EEST Roland Bewick a écrit :
> Hi Rémi,
> 
> Thanks for the reply.
> 
> On 24/07/2019 10:59 PM, Rémi Denis-Courmont wrote:
> > 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.
> 
> I will take Alexandre's suggestion.
> 
> > 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.
> Respond to what? I don't understand.

Typically, discovery protocols wait for inbound client requests.

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