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

[Roland Bewick]

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.