Dear Jon,
Sorry for the delayed response.
Anyhow, the constant VL_MSG_FIRST_AVAILABLE is a historical name for a simple
thing: the number of binary API messages defined by a given plugin. I’m not
sure what you’re trying to do, but it’s actually just as well that you ran into
a compile error. I need to explain a number of details so you won’t end up
seriously annoyed after wasting a bunch of your time.
When the vpp data-plane loads plugins, each plugin which defines a binary API
is expected to do something like the following:
name = format (0, "snat_%08x%c", api_version, 0);
/* Ask for a correctly-sized block of API message decode slots */
sm->msg_id_base = vl_msg_api_get_msg_ids
((char *) name, VL_MSG_FIRST_AVAILABLE);
The data-plane plugin asks for a block of message-ID’s.
vl_msg_api_get_msg_ids(...) makes a string-hash entry, to map the string
<plugin-name>_<api-version> to the base of the message-id block.
When it comes time to send binary API messages to a given plugin, the
control-plane agent recovers msg_id_base like so:
/* Ask the vpp engine for the first assigned message-id */
name = format (0, "snat_%08x%c", api_version, 0);
sm->msg_id_base = vl_client_get_first_plugin_msg_id ((char *) name);
and adds it to the enumerated message id values:
mp->_vl_msg_id = ntohs (msg_id_base + VL_API_some_msg_id);
Since the set of plugins can change between runs, absolute message ID’s can’t
be guaranteed.
Thanks… Dave
From: vpp-dev-boun...@lists.fd.io [mailto:vpp-dev-boun...@lists.fd.io] On
Behalf Of Jon Loeliger
Sent: Tuesday, January 24, 2017 6:46 PM
To: vpp-dev <vpp-dev@lists.fd.io>
Subject: [vpp-dev] SNAT Plugin Use
Folks,
What is the expected method to use the SNAT plugin within the
framework of the rest of a VPP system?
Specifically, what is the expected use of VL_MSG_FIRST_AVAILABLE?
It is several (4) enum include files, and they conflict if two or more are
used in the same source file. Here is a terse example.
Did I miss some documentation that shows how to use the SNAT plugin?
I don't think I need to use the "plugin-ness" of SNAT, as we will always
need to have it present in our app.
Thanks,
jdl
CC interface.c
In file included from interface.c:13:0:
/usr/include/vpp_plugins/snat/snat_msg_enum.h:27:5: error: redeclaration of
enumerator ‘VL_MSG_FIRST_AVAILABLE’
VL_MSG_FIRST_AVAILABLE,
^
In file included from interface.c:12:0:
/usr/include/vpp/api/vpe_msg_enum.h:25:3: note: previous definition of
‘VL_MSG_FIRST_AVAILABLE’ was here
VL_MSG_FIRST_AVAILABLE,
^
In file included from interface.c:13:0:
/usr/include/vpp_plugins/snat/snat_msg_enum.h:28:3: error: conflicting types
for ‘vl_msg_id_t’
} vl_msg_id_t;
^
In file included from interface.c:12:0:
/usr/include/vpp/api/vpe_msg_enum.h:26:3: note: previous declaration of
‘vl_msg_id_t’ was here
} vl_msg_id_t;
^
make: *** [interface.o] Error 1
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