[jboss-jira] [JBoss JIRA] (JGRP-1880) UDP.ip_ttl is ignored and is always 1

[Bela Ban (JIRA)]

    [ https://issues.jboss.org/browse/JGRP-1880?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13006080#comment-13006080 ] 

Bela Ban commented on JGRP-1880:
--------------------------------

I could use reflection, but that's not nice:
{code:java}
        DatagramSocket sock=new DatagramSocket(7500);
        Method getImpl=sock.getClass().getDeclaredMethod("getImpl");
        getImpl.setAccessible(true);

        DatagramSocketImpl impl=(DatagramSocketImpl)getImpl.invoke(sock);
        System.out.println("impl = " + impl);

        Method setTimeToLive=impl.getClass().getDeclaredMethod("setTimeToLive", int.class);
        Method getTimeToLive=impl.getClass().getDeclaredMethod("getTimeToLive");
        getTimeToLive.setAccessible(true);
        setTimeToLive.setAccessible(true);

        int ttl=0;

        ttl=(int)getTimeToLive.invoke(impl);
        System.out.println("ttl = " + ttl);

        ttl=5;

        setTimeToLive.invoke(impl, ttl);

        ttl=(int)getTimeToLive.invoke(impl);
        System.out.println("ttl = " + ttl);

        byte[] buf={'B', 'e', 'l', 'a'};
        DatagramPacket packet=new DatagramPacket(buf, 0, buf.length, InetAddress.getByName("228.8.8.8"), 7500);
        sock.send(packet);
{code}


> UDP.ip_ttl is ignored and is always 1
> -------------------------------------
>
>                 Key: JGRP-1880
>                 URL: https://issues.jboss.org/browse/JGRP-1880
>             Project: JGroups
>          Issue Type: Bug
>            Reporter: Bela Ban
>            Assignee: Bela Ban
>             Fix For: 3.6
>
>
> Since we switched from using a {{MulticastSocket}} for sending of multicast packets to a {{DatagramSocket}}, the time-to-live (TTL) of a packet is always {{1}}. The reason is that method {{setTimeToLive()}} only exists in {{MulticastSocket}}, but not in {{DatagramSocket}}.
> We cannot revert the code and use a {{MulticastSocket}} to send multicasts, as this won't reveal the real IP address of the sender, but only the multicast address, and the real address is needed to drop packets at the _transport level_.
> Investigate whether we could use reflection to get the {{DatagramSocketImpl}} and call {{setTimeToLive()}}.



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