Merge branch '3357-test_send_timeout-add-code-comment' into 'v9_16'

Add code comment to test_send_timeout test

See merge request isc-projects/bind9!6503

bin/tests/system/timeouts/tests-tcp.py

@@ -185,6 +185,11 @@ def test_long_axfr(named_port):
         assert soa is not None
 
 
+# This test relies on the maximum socket send buffer size (wmem_max) being set
+# to 212992 bytes (the typical default value on Linux systems).  Environments
+# that use a different value for this setting (for example, FreeBSD defaults to
+# 32768 bytes) may need their system-level settings to be tweaked in order for
+# this test to pass.
 def test_send_timeout(named_port):
     with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as sock:
         sock.connect(("10.53.0.1", named_port))