From f91cf35f5871ab66f4482a9242c415264314ca84 Mon Sep 17 00:00:00 2001
From: Aaron Conole <aconole@redhat.com>
Date: Tue, 8 Dec 2020 13:20:30 -0500
Subject: [PATCH] tx: when operating in rx-only mode don't send a port shutdown
 pdu

Currently, lldpad correctly transmits a shutdown pdu with ttl = 0s when
transitioning from rxtx or txonly to rxonly.  However, when we shutdown
lldpad it will transmit a shutdown pdu even if the port is configured
to rxonly mode.  For some implementations of LLDP this can create
a confusing state and lead to issues in the network.  Correct this by
only transmitting a shutdown PDU when going from any transmit mode to
a receive only mode, and don't transmit PDUs on shutdown if the port
agent isn't configured to transmit.

Reported-by: Matthew Whitehead <mwhitehe@redhat.com>
Reported-at: https://bugzilla.redhat.com/show_bug.cgi?id=1905210
Signed-off-by: Aaron Conole <aconole@redhat.com>
---
 lldp/agent.c  |  2 +-
 lldp/states.h |  2 +-
 lldp/tx.c     | 15 +++++++++++++--
 3 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/lldp/agent.c b/lldp/agent.c
index aa4a8d1..14fcf71 100644
--- a/lldp/agent.c
+++ b/lldp/agent.c
@@ -200,7 +200,7 @@ void clean_lldp_agents(void)
 			LLDPAD_DBG("Send shutdown frame on port %s\n",
 				port->ifname);
 			LIST_FOREACH(agent, &port->agent_head, entry) {
-				process_tx_shutdown_frame(port, agent);
+				process_tx_shutdown_frame(port, agent, false);
 			}
 		} else {
 			LLDPAD_DBG("No shutdown frame is sent on port %s\n",
diff --git a/lldp/states.h b/lldp/states.h
index 7cf69b8..f7b8ee0 100644
--- a/lldp/states.h
+++ b/lldp/states.h
@@ -85,7 +85,7 @@ u8 txFrame(struct port *port, struct lldp_agent *);
 void run_tx_sm(struct port *, struct lldp_agent *);
 void process_tx_initialize_sm(struct port *);
 void process_tx_idle(struct lldp_agent *);
-void process_tx_shutdown_frame(struct port *, struct lldp_agent *);
+void process_tx_shutdown_frame(struct port *, struct lldp_agent *, bool);
 void process_tx_info_frame(struct port *, struct lldp_agent *);
 void update_tx_timers(struct lldp_agent *);
 void run_tx_timers_sm(struct port *, struct lldp_agent *);
diff --git a/lldp/tx.c b/lldp/tx.c
index 1b95208..9b36071 100644
--- a/lldp/tx.c
+++ b/lldp/tx.c
@@ -270,7 +270,7 @@ void run_tx_sm(struct port *port, struct lldp_agent *agent)
 			process_tx_idle(agent);
 			break;
 		case TX_SHUTDOWN_FRAME:
-			process_tx_shutdown_frame(port, agent);
+			process_tx_shutdown_frame(port, agent, true);
 			break;
 		case TX_INFO_FRAME:
 			process_tx_info_frame(port, agent);
@@ -330,8 +330,19 @@ void process_tx_idle(UNUSED struct lldp_agent *agent)
 	return;
 }
 
-void process_tx_shutdown_frame(struct port *port, struct lldp_agent *agent)
+/* we ignore 'state' value in the case that we have recently transitioned
+ * to the shutdown state (in the case of the 'tx' state change) to allow
+ * for transmitting the ttl==0 as required by the IEEE standard. */
+void process_tx_shutdown_frame(struct port *port, struct lldp_agent *agent,
+				bool ignoreState)
 {
+	if (agent->adminStatus != enabledRxTx &&
+	    agent->adminStatus != enabledTxOnly) {
+		if (!ignoreState) {
+			return;
+		}
+	}
+
 	if (agent->timers.txShutdownWhile == 0) {
 		if (mibConstrShutdownLLDPDU(port, agent))
 			txFrame(port, agent);
-- 
2.33.0