DSCP packet marking support in Linuxbridge agent

Linuxbridge agent uses iptable rules in POSTROUTING chain
in the mangle table to mark outgoing packets with the
DSCP mark value configured by the user in QoS policy.

DocImpact: DSCP Marking rule support is extended to the
           Linuxbridge L2 agent

Closes-Bug: #1644369

Change-Id: I47e44cb2e67ab73bd5ee0aa4cca47cb3d07e43f3

neutron/tests/common/agents/l2_extensions.py

@@ -16,6 +16,7 @@
 import re
 
 from neutron.agent.linux import async_process
+from neutron.agent.linux import iptables_manager
 from neutron.common import utils as common_utils
 
 
@@ -38,6 +39,15 @@ def extract_mod_nw_tos_action(flows):
     return tos_mark
 
 
+def extract_dscp_value_from_iptables_rules(rules):
+    pattern = (r"^-A neutron-linuxbri-qos-.* -j DSCP "
+               "--set-dscp (?P<dscp_value>0x[A-Fa-f0-9]+)$")
+    for rule in rules:
+        m = re.match(pattern, rule)
+        if m:
+            return int(m.group("dscp_value"), 16)
+
+
 def wait_until_bandwidth_limit_rule_applied(bridge, port_vif, rule):
     def _bandwidth_limit_rule_applied():
         bw_rule = bridge.get_egress_bw_limit_for_port(port_vif)
@@ -49,7 +59,7 @@ def wait_until_bandwidth_limit_rule_applied(bridge, port_vif, rule):
     common_utils.wait_until_true(_bandwidth_limit_rule_applied)
 
 
-def wait_until_dscp_marking_rule_applied(bridge, port_vif, rule):
+def wait_until_dscp_marking_rule_applied_ovs(bridge, port_vif, rule):
     def _dscp_marking_rule_applied():
         port_num = bridge.get_port_ofport(port_vif)
 
@@ -64,6 +74,20 @@ def wait_until_dscp_marking_rule_applied(bridge, port_vif, rule):
     common_utils.wait_until_true(_dscp_marking_rule_applied)
 
 
+def wait_until_dscp_marking_rule_applied_linuxbridge(
+    namespace, port_vif, expected_rule):
+
+    iptables = iptables_manager.IptablesManager(
+        namespace=namespace)
+
+    def _dscp_marking_rule_applied():
+        mangle_rules = iptables.get_rules_for_table("mangle")
+        dscp_mark = extract_dscp_value_from_iptables_rules(mangle_rules)
+        return dscp_mark == expected_rule
+
+    common_utils.wait_until_true(_dscp_marking_rule_applied)
+
+
 def wait_for_dscp_marked_packet(sender_vm, receiver_vm, dscp_mark):
     cmd = ["tcpdump", "-i", receiver_vm.port.name, "-nlt"]
     if dscp_mark: