[Live-devel] Concerning multicast TTL of zero

[Martínez Contador, Daniel [ELIMCO] (CA)]

Hello.
For my application I need to send differently scoped multicast RTP.
I have found that I use both the multicast address and the TTL to try different configurations.
However, I cannot send multicast packets with a TTL of zero (meaning traffic restricted to the same host). They get sent but with a TTL of 1 (meaning traffic restricted to the same subnet, not what I want).
I have seen the problem lies in writeSocket in GroupsockHelper: it skips the setsockopt to set the TTL if it is 0.
Removing the condition seems to work (meaning such packets reach receivers in the same host but are not seen by other hosts in the subnet or traffic analysers), but I wonder if not setting TTL 0 is intentional and by enabling it I will be having "collaterals".
So, should everything work as expected when enabling TTL 0?
Would this be filed as a "bug" and be corrected in the next version?
I could send a patch, but that would make me a "contributor" and for just removing two obvious lines seems to much of a mention.

Best Regards.

Daniel Martínez Contador
Navantia - Sistemas de Control
Ctra. Algameca, s/n
30205 Cartagena (Murcia)
Tlfo: 968 323 387
Email: elimco.dmartinez at navantia.es


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