listen -utility vs. aprsd and its treatment of AX.25 sockets..

listen -utility vs. aprsd and its treatment of AX.25 sockets..

[Matti Aarnio]

   rx_socket = socket(PF_PACKET, SOCK_PACKET, htons(proto));

   tx_socket = socket(PF_AX25, SOCK_DGRAM, 0)


Where the 'proto' is either ETH_P_AX25  or ETH_P_ALL.


In the  'listen'  utility the proto is  ETH_P_AX25  unless '-a' option
is given, then it is ETH_P_ALL.  In  'aprsd' it is always ETH_P_ALL.


Given explanation is that ETH_P_AX25 sees only incoming packets, while
ETH_P_ALL sees also outgoing ones.   Presuming that I am only interested
in AX.25 packets but do want to know also outgoing frames, which one
I should use -- or is the commentary on this utilities sources wrong ?

  73 de Matti, OH2MQK

Re: listen -utility vs. aprsd and its treatment of AX.25 sockets..

[Hamish Moffatt]

On Tue, Nov 06, 2007 at 10:52:47PM +0200, Matti Aarnio wrote:
>    rx_socket = socket(PF_PACKET, SOCK_PACKET, htons(proto));
> 
>    tx_socket = socket(PF_AX25, SOCK_DGRAM, 0)
> 
> Where the 'proto' is either ETH_P_AX25  or ETH_P_ALL.
> 
> 
> In the  'listen'  utility the proto is  ETH_P_AX25  unless '-a' option
> is given, then it is ETH_P_ALL.  In  'aprsd' it is always ETH_P_ALL.

When I added AX.25 sockets functionality to aprsd, I "leveraged" the
code from listen, so you should expect them to be the same.

I can't think now why aprsd would need to monitor outgoing frames
though. Perhaps so that it hears packets sent by other AX.25
applications running on the same host eg aprsdigi. However it does add
the requirement to run as root which aprsd might not have otherwise.


Hamish
-- 
Hamish Moffatt VK3SB <hamish@debian.org> <hamish@cloud.net.au>