Wake video transmission on router queue readiness without polling delay

tests/test_call_video_flush.c

@@ -4,12 +4,16 @@
 #define etcp_router_tx_stats test_router_tx_stats
 #define etcp_router_send_q_has_room test_router_send_q_has_room
 #define etcp_router_resume_receive test_router_resume_receive
+#define etcp_router_on_send_ready test_router_on_send_ready
+#define etcp_router_cancel_send_ready test_router_cancel_send_ready
 #include "../src/call/call_video_transport.c"
 #undef etcp_router_conn_get
 #undef etcp_router_conn_send
 #undef etcp_router_tx_stats
 #undef etcp_router_send_q_has_room
 #undef etcp_router_resume_receive
+#undef etcp_router_on_send_ready
+#undef etcp_router_cancel_send_ready
 #include <assert.h>
 #include <stdio.h>
 
@@ -19,6 +23,8 @@ extern void process_immediate_queue(struct UASYNC *ua);
 static struct ETCP_ROUTER_CONN router;
 static unsigned packets, received, room, resumed;
 static uint64_t debt;
+static queue_threshold_callback_fn ready_callback;
+static void *ready_arg;
 enum { FRAME_BYTES = 45001 };
 static uint8_t output[FRAME_BYTES];
 
@@ -44,6 +50,14 @@ int test_router_send_q_has_room(struct UTUN_INSTANCE *inst, uint64_t group, uint
 void test_router_resume_receive(struct UTUN_INSTANCE *inst, uint64_t group, uint64_t peer, uint8_t svc) {
     (void)inst; (void)group; (void)peer; (void)svc; resumed++;
 }
+void test_router_on_send_ready(struct UTUN_INSTANCE *inst, uint64_t group, uint64_t peer, uint8_t svc,
+    struct queue_waiter_handle *h, queue_threshold_callback_fn callback, void *arg) {
+    (void)inst; (void)group; (void)peer; (void)svc; (void)h; ready_callback = callback; ready_arg = arg;
+}
+void test_router_cancel_send_ready(struct UTUN_INSTANCE *inst, uint64_t group, uint64_t peer, uint8_t svc,
+    struct queue_waiter_handle *h) {
+    (void)inst; (void)group; (void)peer; (void)svc; (void)h; ready_callback = NULL; ready_arg = NULL;
+}
 
 static struct call_video_transport *setup(struct call_session *s) {
     struct call_video_transport *v = u_calloc(1, sizeof(*v)); assert(v);
@@ -93,7 +107,10 @@ int main(void) {
         if (gate) debt = 1000000; else room = 0;
         process_immediate_queue(ua); assert(packets == 16 && !v->flush_pending && v->flush_net_wait == 1);
         process_immediate_queue(ua); assert(packets == 16);
-        room = 1; debt = 0; flush(v); uasync_drain_immediate(ua); check_complete(v); cleanup(&s);
+        room = 1; debt = 0;
+        if (!gate) { assert(ready_callback && ready_arg == v); ready_callback(router.send_q, ready_arg); }
+        else flush(v);
+        uasync_drain_immediate(ua); check_complete(v); cleanup(&s);
     }
     puts("PASS: router room and inflight debt stop continuation without spinning; TX resumes exactly once");