fix: fsm connection write deadline

A deadline of 1 second is set in the connection initialisation.
This deadline is never changed until the connection gets in the
established state.
So, if the connection doesn't send its open message and its first
keepalive under 1 second we never get a peering.
Under heavy load this is an issue, while testing with 10k peers
without routes, we never connect most of the peers.
Instead, it is preferrable to set a deadline of 1s for each write.

Author: Maxime Peim

pkg/server/fsm.go

@@ -208,8 +208,6 @@ func (s *adminStateRaw) Store(state adminState) {
 }
 
 func initializeConn(fsm *fsm, conn net.Conn) {
-	conn.SetWriteDeadline(time.Now().Add(time.Second))
-
 	fsm.lock.Lock()
 	if err := setPeerConnTTL(fsm, conn); err != nil {
 		fsm.logger.Warn("cannot set TTL",
@@ -285,6 +283,7 @@ func (ocm *outgoingConnManager) run(ch chan<- outgoingConn) {
 			fsm.lock.Unlock()
 			b, _ := open.Serialize()
 
+			conn.SetWriteDeadline(time.Now().Add(time.Second))
 			if _, err := conn.Write(b); err != nil {
 				conn.Close()
 				continue
@@ -906,6 +905,7 @@ func (h *fsmHandler) active(ctx context.Context) (bgp.FSMState, *fsmStateReason)
 			fsm.lock.Unlock()
 
 			b, _ := m.Serialize()
+			conn.SetWriteDeadline(time.Now().Add(time.Second))
 			_, err := conn.Write(b)
 			if err == nil {
 				fsm.bgpMessageStateUpdate(m.Header.Type, false)
@@ -914,6 +914,7 @@ func (h *fsmHandler) active(ctx context.Context) (bgp.FSMState, *fsmStateReason)
 			return bgp.BGP_FSM_IDLE, newfsmStateReason(fsmWriteFailed, nil, []byte(err.Error()))
 		case result := <-fsm.outgoingConnCh:
 			b, _ := bgp.NewBGPKeepAliveMessage().Serialize()
+			result.conn.SetWriteDeadline(time.Now().Add(time.Second))
 			if _, err := result.conn.Write(b); err != nil {
 				result.conn.Close()
 				fsm.logger.Warn("failed to send keepalive on outgoing connection", slog.String("Error", err.Error()))
@@ -1408,6 +1409,7 @@ func (h *fsmHandler) opensent(ctx context.Context) (bgp.FSMState, *fsmStateReaso
 			}
 
 			b, _ := bgp.NewBGPKeepAliveMessage().Serialize()
+			fsm.conn.SetWriteDeadline(time.Now().Add(time.Second))
 			if _, err := fsm.conn.Write(b); err != nil {
 				fsm.conn.Close()
 				return bgp.BGP_FSM_IDLE, newfsmStateReason(fsmWriteFailed, nil, nil)
@@ -1452,6 +1454,7 @@ func (h *fsmHandler) opensent(ctx context.Context) (bgp.FSMState, *fsmStateReaso
 				}
 			}
 			b, _ := bgp.NewBGPKeepAliveMessage().Serialize()
+			fsm.conn.SetWriteDeadline(time.Now().Add(time.Second))
 			if _, err := fsm.conn.Write(b); err != nil {
 				fsm.conn.Close()
 				fsm.logger.Warn("failed to send keepalive on outgoing connection", slog.String("Error", err.Error()))
@@ -1552,6 +1555,7 @@ func (h *fsmHandler) openconfirm(ctx context.Context) (bgp.FSMState, *fsmStateRe
 			m := bgp.NewBGPKeepAliveMessage()
 			b, _ := m.Serialize()
 			// TODO: check error
+			fsm.conn.SetWriteDeadline(time.Now().Add(time.Second))
 			fsm.conn.Write(b)
 			fsm.bgpMessageStateUpdate(m.Header.Type, false)
 		case e := <-recvChan: