[iptables PATCH 2/2] tests: iptables-test: Extend fast mode docs a bit

[Phil Sutter <phil@nwl.cc>]

To make things less confusing for new readers, describe at least what
the two significant functions do.

Fixes: 0e80cfea3762b ("tests: iptables-test: Implement fast test mode")
Signed-off-by: Phil Sutter <phil@nwl.cc>
---
 iptables-test.py | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/iptables-test.py b/iptables-test.py
index 413e3fdccc9e3..141fec7b4ed16 100755
--- a/iptables-test.py
+++ b/iptables-test.py
@@ -241,10 +241,14 @@ STDERR_IS_TTY = sys.stderr.isatty()
 
 def fast_run_possible(filename):
     '''
-    Keep things simple, run only for simple test files:
+    Return true if fast test run is possible.
+
+    To keep things simple, run only for simple test files:
     - no external commands
     - no multiple tables
     - no variant-specific results
+
+    :param filename: test file to inspect
     '''
     table = None
     rulecount = 0
@@ -267,6 +271,9 @@ STDERR_IS_TTY = sys.stderr.isatty()
     '''
     Run a test file, but fast
 
+    Add all non-failing rules at once by use of iptables-restore, then check
+    all rules' listing at once by use of iptables-save.
+
     :param filename: name of the file with the test rules
     :param netns: network namespace to perform test run in
     '''
-- 
2.47.0