lib: Complete retransmission logic

This completes the retransmission (automated repeat-request, ARQ)
logic, sending (delayed) ACK messages when needed.

On deallocation, flows will ACK try to retransmit any remaining
unacknowledged messages (unless the FRCTFLINGER flag is turned off;
this is on by default). Applications can safely shut down as soon as
everything is ACK'd (i.e. the current Delta-t run is done). The
activity timeout is now passed to the IPCP for it to sleep before
completing deallocation (and releasing the flow_id). That should be
moved to the IRMd in due time.

The timerwheel is revised to be multi-level to reduce memory
consumption. The resolution bumps by a factor of 1 << RXMQ_BUMP (16)
and each level has RXMQ_SLOTS (1 << 8) slots.  The lowest level has a
resolution of (1 << RXMQ_RES) (20) ns, which is roughly a
millisecond. Currently, 3 levels are defined, so the largest delay we
can schedule at each level is:

Level 0: 256ms
Level 1: 4s
Level 2: about a minute.

Signed-off-by: Dimitri Staessens <dimitri@ouroboros.rocks>
Signed-off-by: Sander Vrijders <sander@ouroboros.rocks>

3 files changed, 23 insertions, 15 deletions

diff --git a/src/irmd/ipcp.c b/src/irmd/ipcp.c
index 78408185..cbd9ee15 100644
--- a/src/irmd/ipcp.c
+++ b/src/irmd/ipcp.c
@@ -543,16 +543,19 @@ int ipcp_flow_alloc_resp(pid_t        pid,
         return ret;
 }
 
-int ipcp_flow_dealloc(pid_t pid,
-                      int   flow_id)
+int ipcp_flow_dealloc(pid_t  pid,
+                      int    flow_id,
+                      time_t timeo)
 {
         ipcp_msg_t   msg      = IPCP_MSG__INIT;
         ipcp_msg_t * recv_msg = NULL;
         int          ret      = -1;
 
-        msg.code        = IPCP_MSG_CODE__IPCP_FLOW_DEALLOC;
-        msg.has_flow_id = true;
-        msg.flow_id     = flow_id;
+        msg.code          = IPCP_MSG_CODE__IPCP_FLOW_DEALLOC;
+        msg.has_flow_id   = true;
+        msg.flow_id       = flow_id;
+        msg.has_timeo_sec = true;
+        msg.timeo_sec     = timeo;
 
         recv_msg = send_recv_ipcp_msg(pid, &msg);
         if (recv_msg == NULL)
diff --git a/src/irmd/ipcp.h b/src/irmd/ipcp.h
index ae00792b..652316ba 100644
--- a/src/irmd/ipcp.h
+++ b/src/irmd/ipcp.h
@@ -85,7 +85,8 @@ int   ipcp_flow_alloc_resp(pid_t        pid,
                            const void * data,
                            size_t       len);
 
-int   ipcp_flow_dealloc(pid_t pid,
-                        int   flow_id);
+int   ipcp_flow_dealloc(pid_t  pid,
+                        int    flow_id,
+                        time_t timeo);
 
 #endif /* OUROBOROS_IRMD_IPCP_H */
diff --git a/src/irmd/main.c b/src/irmd/main.c
index 3709a3e5..3a0ad544 100644
--- a/src/irmd/main.c
+++ b/src/irmd/main.c
@@ -68,10 +68,11 @@
 #endif
 
 #define IRMD_CLEANUP_TIMER ((IRMD_FLOW_TIMEOUT / 20) * MILLION) /* ns */
-#define SHM_SAN_HOLDOFF 1000 /* ms */
-#define IPCP_HASH_LEN(e) hash_len(e->dir_hash_algo)
-#define IB_LEN SOCK_BUF_SIZE
-#define BIND_TIMEOUT  10 /* ms */
+#define SHM_SAN_HOLDOFF    1000 /* ms */
+#define IPCP_HASH_LEN(e)   hash_len(e->dir_hash_algo)
+#define IB_LEN             SOCK_BUF_SIZE
+#define BIND_TIMEOUT       10   /* ms */
+#define DEALLOC_TIME       300  /*  s */
 
 enum init_state {
         IPCP_NULL = 0,
@@ -1475,7 +1476,8 @@ static int flow_alloc(pid_t              pid,
 }
 
 static int flow_dealloc(pid_t pid,
-                        int   flow_id)
+                        int   flow_id,
+                        time_t timeo)
 {
         pid_t n_1_pid = -1;
         int   ret = 0;
@@ -1521,7 +1523,7 @@ static int flow_dealloc(pid_t pid,
         pthread_rwlock_unlock(&irmd.flows_lock);
 
         if (n_1_pid != -1)
-                ret = ipcp_flow_dealloc(n_1_pid, flow_id);
+                ret = ipcp_flow_dealloc(n_1_pid, flow_id, timeo);
 
         return ret;
 }
@@ -1927,7 +1929,7 @@ void * irm_sanitize(void * o)
                                 ipcpi   = f->n_1_pid;
                                 flow_id = f->flow_id;
                                 pthread_rwlock_unlock(&irmd.flows_lock);
-                                ipcp_flow_dealloc(ipcpi, flow_id);
+                                ipcp_flow_dealloc(ipcpi, flow_id, DEALLOC_TIME);
                                 pthread_rwlock_wrlock(&irmd.flows_lock);
                                 continue;
                         }
@@ -2190,7 +2192,9 @@ static void * mainloop(void * o)
                         }
                         break;
                 case IRM_MSG_CODE__IRM_FLOW_DEALLOC:
-                        result = flow_dealloc(msg->pid, msg->flow_id);
+                        result = flow_dealloc(msg->pid,
+                                              msg->flow_id,
+                                              msg->timeo_sec);
                         break;
                 case IRM_MSG_CODE__IPCP_FLOW_REQ_ARR:
                         assert(msg->pk.len > 0 ? msg->pk.data != NULL