[dpdk-dev] [PATCH] app/testpmd: Document what the application does.

[Ben Pfaff <blp@ovn.org>]

I could not find anything in the documentation that says what
testpmd does.  This should save other people time trying to
figure that out in the future.

Signed-off-by: Ben Pfaff <blp@ovn.org>
---
 doc/guides/testpmd_app_ug/run_app.rst | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/doc/guides/testpmd_app_ug/run_app.rst b/doc/guides/testpmd_app_ug/run_app.rst
index 6061674239..7c3406f72b 100644
--- a/doc/guides/testpmd_app_ug/run_app.rst
+++ b/doc/guides/testpmd_app_ug/run_app.rst
@@ -15,6 +15,12 @@ a list of available EAL command-line options.
 Testpmd Command-line Options
 ----------------------------
 
+By default, testpmd receives packets on each configured port and
+forwards the received packets to its paired port.  Ports 0 and 1 are
+paired, as are ports 2 and 3, and so on.  With an odd number of ports,
+the last port is paired with itself: packets received on the port are
+sent back out on the same port.
+
 The following are the command-line options for the testpmd applications.
 They must be separated from the EAL options, shown in the previous section, with a ``--`` separator:
 
-- 
2.31.1