new TCP timer object; solved a bunch of warnings; completely implemented the TCP termination sequence

src/icmp.c

@@ -89,7 +89,7 @@ void icmp_process_packet(icmp_state_t *state, ip_address_t ip, const void *src,
             }
             
             if (state->output_ptr == NULL || state->output_len < len) {
-                ICMP_DEBUG_LOG("Ignoring ECHO REQUEST because the output buffer is too small for an ECHO REPLY (have %ld, need %ld)", state->output_len, len);
+                ICMP_DEBUG_LOG("Ignoring ECHO REQUEST because the output buffer is too small for an ECHO REPLY (have %d, need %d)", (int) state->output_len, (int) len);
                 return;
             }
 

src/ip.c

@@ -239,7 +239,7 @@ void ip_process_packet(ip_state_t *ip_state, const void *packet, size_t len)
 
     size_t option_count = header_length - sizeof(ip_packet_t)/4;
     if (option_count > 0) {
-        #warning "TODO: Handle IP options"
+        // TODO: Handle IP options
         return;
     }
     

src/microtcp.c

@@ -187,7 +187,6 @@ static void send_arp_packet(void *data, mac_address_t dst)
     frame->proto = cpu_to_net_u16(ETHERNET_PROTOCOL_ARP);
 
     // TODO: What about the CRC?
-    #warning "TODO: Calculate Ethernet CRC"
 
     int n = mtcp->callbacks.send(mtcp->callbacks.data, buffer->data, buffer->used);
     if (n < 0)
@@ -828,9 +827,10 @@ microtcp_socket_t *microtcp_open(microtcp_t *mtcp, uint16_t port,
             goto unlock_and_exit; // Socket limit reached
         }
 
-        tcp_listener_t *listener = tcp_listener_create(&mtcp->tcp_state, port, socket, ready_to_accept);
+        tcp_listener_t *listener = tcp_listener_create(&mtcp->tcp_state, port, socket, false, ready_to_accept);
         if (listener == NULL) {
-            #warning "This error code should be more specific, but the TCP module isn't stable yet"
+            // FIXME: This error code should be more specific, 
+            //        but the TCP module isn't stable yet
             errcode2 = MICROTCP_ERRCODE_TCPERROR;
             push_unlinked_socket_into_free_list(mtcp, socket);
             goto unlock_and_exit;
@@ -870,10 +870,22 @@ void microtcp_close(microtcp_socket_t *socket)
 
     microtcp_t *mtcp = socket->mtcp;
 
-    #warning "sockets should unregister from all multiplexers"
-
     LOCK_WHEN_THREADED(mtcp);
     {
+
+#ifdef MICROTCP_USING_MUX
+        // Unregister from all multiplexers
+        while (socket->mux_list) {
+            // The unregister operation only has 
+            // an effect when all of the triggered
+            // events of the socket are consumed,
+            // so to unregister immediately we need
+            // to untrigger the events
+            socket->mux_list->triggered_events = 0;
+            microtcp_mux_unregister(socket->mux_list->mux, socket, ~0);
+        }
+#endif
+
         switch (socket->type) {
             
             case SOCKET_LISTENER:
@@ -1038,7 +1050,10 @@ size_t microtcp_recv(microtcp_socket_t *socket,
                 errcode2 = MICROTCP_ERRCODE_CANTBLOCK;
         }
     }
-unlock_and_exit:
+    
+    goto unlock_and_exit; // Warning
+    unlock_and_exit:
+    
     UNLOCK_WHEN_THREADED(mtcp);
 
     if (errcode)
@@ -1082,7 +1097,8 @@ size_t microtcp_send(microtcp_socket_t *socket,
                 errcode2 = MICROTCP_ERRCODE_CANTBLOCK;
         }
     }
-unlock_and_exit:
+    goto unlock_and_exit; // Warning
+    unlock_and_exit:
     UNLOCK_WHEN_THREADED(mtcp);
 
     if (errcode)

src/tcp.c

@@ -31,19 +31,20 @@ void tcp_init(tcp_state_t *tcp_state, ip_address_t ip, tcp_callbacks_t callbacks
     tcp_state->listener_pool[TCP_MAX_LISTENERS-1].next = NULL;
     tcp_state->free_listener_list = tcp_state->listener_pool;
     tcp_state->used_listener_list = NULL;
+
+    tcp_timerset_init(&tcp_state->timers);
 }
 
-void tcp_free(tcp_state_t *tcp_state)
+void tcp_free(tcp_state_t *state)
 {
-    // Destroy all listening connections
-    while (tcp_state->used_listener_list != NULL)
-        tcp_listener_destroy(tcp_state->used_listener_list);
+    // It's not clear to me how to free 
+    // all of this stuff up at the moment :/
+    tcp_timerset_free(&state->timers);
 }
 
 void tcp_seconds_passed(tcp_state_t *state, size_t seconds)
 {
-    (void) state;
-    (void) seconds;
+    tcp_timerset_step(&state->timers, seconds);
 }
 
 static tcp_connection_t*
@@ -155,7 +156,7 @@ calculate_checksum(const slice_list_t *slices, size_t num_slices)
 }
 
 static void emit_segment(tcp_connection_t *connection, uint8_t flags, size_t payload)
-{   
+{
     tcp_listener_t *listener = connection->listener;
     tcp_state_t    *state    = listener->state;
 
@@ -337,22 +338,79 @@ static bool ack_until(tcp_connection_t *connection, uint32_t ack_no)
     return true;
 }
 
+static void
+really_close_listener(tcp_listener_t *listener)
+{
+    tcp_state_t *state = listener->state;
+
+    // Pop listener from used list
+    {
+        // Update the reference to the listener of
+        // the one that precedes it in the list
+        if (listener->prev)
+            listener->prev->next = listener->next;
+        else
+            state->used_listener_list = listener->next;
+
+        // Update the reference to the listener of
+        // the one that follows it in the list
+        if (listener->next != NULL)
+            listener->next->prev = listener->prev;
+    }
+
+    // Push the listener in the free list
+    listener->next = state->free_listener_list;
+    state->free_listener_list = listener;
+}
+
+static bool listener_has_no_connections(const tcp_listener_t *listener)
+{
+    return listener->accepted_list == NULL 
+        && listener->non_established_list == NULL 
+        && listener->non_accepted_queue_head == NULL;
+}
+
 static void 
 really_close_connection(tcp_connection_t *connection)
 {
     tcp_listener_t *listener = connection->listener;
     tcp_state_t *state = listener->state;
 
-    // Pop connection from the accepted_list
+    // Pop connection from the list it's in
+    tcp_connection_t *next = connection->next;
     if (connection->prev)
-        connection->prev->next = connection->next;
-    else
-        listener->accepted_list = connection->next;
+        connection->prev->next = next;
+    else if (listener->accepted_list == connection)
+        listener->accepted_list = next;
+    else if (listener->non_established_list == connection)
+        listener->non_established_list = next;
+    else if (listener->non_accepted_queue_head == connection)
+        listener->non_accepted_queue_head = next;        
+    tcp_connection_t *prev = connection->prev;
+    if (next)
+        connection->next->prev = prev;
+    else if (listener->non_accepted_queue_tail == connection)
+        listener->non_accepted_queue_tail = prev;
 
     // Push it into the free connection list
     connection->prev = NULL;
     connection->next = state->free_connection_list;
     state->free_connection_list = connection;
+
+    // If the listener is waiting to be closed
+    // and this was the last connection it was
+    // holding, then free the listener
+    if (listener->closed == true && listener_has_no_connections(listener))
+        really_close_listener(listener);
+}
+
+static void timeout_callback_time_wait(void *data)
+{
+    tcp_connection_t *connection = data;
+    assert(connection->state == TCP_STATE_TIME_WAIT);
+
+    // We can finally free up this connection structure!
+    really_close_connection(connection);
 }
 
 void tcp_process_segment(tcp_state_t *state, ip_address_t sender,
@@ -388,6 +446,13 @@ void tcp_process_segment(tcp_state_t *state, ip_address_t sender,
     tcp_connection_t *connection = find_connection_associated_to_listener(listener, sender, reordered_src_port);
     if (!connection) {
 
+        if (listener->closed) {
+            // Listener was closed by the user, so already
+            // open connections are ok but new ones are not
+            // allowed.
+            return;
+        }
+
         TCP_DEBUG_LOG("Connection request from port %d", reordered_src_port);
 
         // Something sent to an open listener. 
@@ -534,10 +599,17 @@ void tcp_process_segment(tcp_state_t *state, ip_address_t sender,
             if (segment->flags & (TCP_FLAG_FIN | TCP_FLAG_ACK)) {
 
                 TCP_DEBUG_LOG("FIN-WAIT-1 -> TIME-WAIT");
+    
                 connection->rcv_nxt++; // FIN ghost byte
                 emit_segment(connection, TCP_FLAG_ACK, 0);
+    
                 connection->state = TCP_STATE_TIME_WAIT;
 
+                // Don't close the connection just now but
+                // wait for a given amount of time first.
+                if (!tcp_timer_create(&state->timers, TCP_TIMEOUT_TIME_WAIT, timeout_callback_time_wait, connection))
+                    assert(0);
+
             } else if (segment->flags & TCP_FLAG_ACK) {
 
                 TCP_DEBUG_LOG("FIN-WAIT-1 -> FIN-WAIT-2");
@@ -567,6 +639,11 @@ void tcp_process_segment(tcp_state_t *state, ip_address_t sender,
             emit_segment(connection, TCP_FLAG_ACK, 0);
 
             connection->state = TCP_STATE_TIME_WAIT;
+
+            // Don't close the connection just now but
+            // wait for a given amount of time first.
+            if (!tcp_timer_create(&state->timers, TCP_TIMEOUT_TIME_WAIT, timeout_callback_time_wait, connection))
+                assert(0);
             break;
 
             case TCP_STATE_CLOSE_WAIT:
@@ -609,70 +686,55 @@ void tcp_process_segment(tcp_state_t *state, ip_address_t sender,
 }
 
 tcp_listener_t*
-tcp_listener_create(tcp_state_t *state, uint16_t port, void *callback_data, 
-                    void (*callback_ready_to_accept)(void*))
+tcp_listener_create(tcp_state_t *state, uint16_t port, bool reuse,
+                    void *callback_data, void (*callback_ready_to_accept)(void*))
 {
-    if (find_listener_with_port(state, port)) {
+    tcp_listener_t *listener;
+
+    listener = find_listener_with_port(state, port);
+    if (listener && (!listener->closed || !reuse)) {
         // ERROR: A connection is already listening on this port
         TCP_DEBUG_LOG("Faile to create listener on port %d because there already exists one", port);
         return NULL;
     }
 
-    // Pop a listener connection structure from the free list
-    if (state->free_listener_list == NULL) {
-        // ERROR: Reached listener connection limit
-        TCP_DEBUG_LOG("TCP connection limit");
-        return NULL;
+    if (listener)
+        listener->closed = false;
+    else {
+
+        // Pop a listener connection structure from the free list
+        if (state->free_listener_list == NULL) {
+            // ERROR: Reached listener connection limit
+            TCP_DEBUG_LOG("TCP connection limit");
+            return NULL;
+        }
+        listener = state->free_listener_list;
+        state->free_listener_list = listener->next;
+
+        // Initialize listener structure
+        listener->state  = state;
+        listener->closed = false;
+        listener->port   = port;
+        listener->accepted_list = NULL;
+        listener->non_established_list    = NULL;
+        listener->non_accepted_queue_head = NULL;
+        listener->non_accepted_queue_tail = NULL;
+        listener->callback_data = callback_data;
+        listener->callback_ready_to_accept = callback_ready_to_accept;
+
+        // Push listener connection structure to the used list
+        listener->prev = NULL;
+        listener->next = state->used_listener_list;
+        if (state->used_listener_list)
+            state->used_listener_list->prev = listener;
+        state->used_listener_list = listener;
     }
-    tcp_listener_t *listener = state->free_listener_list;
-    state->free_listener_list = listener->next;
-
-    // Initialize listener structure
-    listener->state = state;
-    listener->port = port;
-    listener->accepted_list = NULL;
-    listener->non_established_list = NULL;
-    listener->non_accepted_queue_head = NULL;
-    listener->non_accepted_queue_tail = NULL;
-    listener->callback_data = callback_data;
-    listener->callback_ready_to_accept = callback_ready_to_accept;
-
-    // Push listener connection structure to the used list
-    listener->prev = NULL;
-    listener->next = state->used_listener_list;
-    if (state->used_listener_list)
-        state->used_listener_list->prev = listener;
-    state->used_listener_list = listener;
-
     return listener;
 }
 
 void tcp_listener_destroy(tcp_listener_t *listener)
 {
-    #warning "The previously accepted connections should't be closed with their listener.. I think"
-
-    // TODO: Close all connections
-
-    tcp_state_t *state = listener->state;
-
-    // Pop listener from used list
-    {
-        // Update the reference to the listener of
-        // the one that precedes it in the list
-        if (listener->prev)
-            listener->prev->next = listener->next;
-        else
-            state->used_listener_list = listener->next;
-
-        // Update the reference to the listener of
-        // the one that follows it in the list
-        if (listener->next != NULL)
-            listener->next->prev = listener->prev;
-    }
-
-    // Push the listener in the free list
-    listener->next = state->free_listener_list;
-    state->free_listener_list = listener;
+    listener->closed = true;
 }
 
 tcp_connection_t *tcp_listener_accept(tcp_listener_t *listener, void *callback_data, 

src/tcp.h

@@ -3,8 +3,12 @@
 
 #ifndef MICROTCP_AMALGAMATION
 #include "defs.h"
+#include "tcp_timer.h"
 #endif
 
+#define TCP_TIMEOUT_TIME_WAIT 240
+
+#define TCP_MAX_TIMEOUTS 1024
 #define TCP_MAX_LISTENERS 32
 #define TCP_MAX_SOCKETS 1024
 #define TCP_INPUT_BUFFER_SIZE 1024
@@ -35,12 +39,19 @@ typedef struct {
 static_assert(sizeof(tcp_segment_t) == 20);
 
 typedef struct tcp_connection_t tcp_connection_t;
-typedef struct tcp_listener_t tcp_listener_t;
+typedef struct tcp_listener_t   tcp_listener_t;
 
 struct tcp_listener_t {
     tcp_state_t *state;
     tcp_listener_t *prev;
     tcp_listener_t *next;
+    bool closed; // When a listener is closed while one or more connections that is
+                 // previously accepted are open, the structure isn't deallocated
+                 // but just marked lazily as "closed". A listener in the "closed-but-not-deallocated"
+                 // state will not accept new connections but will serve the ones
+                 // its still holding.
+                 // In this state the listener can be reopened by setting the "closed"
+                 // flag to true (and keeping the old connections intact).
     uint16_t port;
     tcp_connection_t *accepted_list;
     tcp_connection_t *non_established_list;
@@ -138,20 +149,26 @@ typedef struct {
 } tcp_callbacks_t;
 
 struct tcp_state_t {
+
     ip_address_t ip;
     tcp_callbacks_t callbacks;
+
+    tcp_timerset_t timers;
+
     tcp_connection_t *free_connection_list;
-    tcp_connection_t connection_pool[TCP_MAX_SOCKETS];
+
     tcp_listener_t *used_listener_list;
     tcp_listener_t *free_listener_list;
-    tcp_listener_t listener_pool[TCP_MAX_LISTENERS];
+
+    tcp_listener_t     listener_pool[TCP_MAX_LISTENERS];
+    tcp_connection_t connection_pool[TCP_MAX_SOCKETS];
 };
 
 void              tcp_init(tcp_state_t *tcp_state, ip_address_t ip, tcp_callbacks_t callbacks);
 void              tcp_free(tcp_state_t *tcp_state);
 void              tcp_seconds_passed(tcp_state_t *state, size_t seconds);
 void              tcp_process_segment(tcp_state_t *state, ip_address_t sender, tcp_segment_t *segment, size_t len);
-tcp_listener_t   *tcp_listener_create(tcp_state_t *state, uint16_t port, void *data, void (*callback)(void*));
+tcp_listener_t   *tcp_listener_create(tcp_state_t *state, uint16_t port, bool reuse, void *data, void (*callback)(void*));
 void              tcp_listener_destroy(tcp_listener_t *listener);
 tcp_connection_t *tcp_listener_accept(tcp_listener_t *listener, void *callback_data, void (*callback_ready_to_recv)(void*), void (*callback_ready_to_send)(void*));
 void              tcp_connection_destroy(tcp_connection_t *connection);

src/tcp_timer.c

@@ -0,0 +1,141 @@
+#ifndef MICROTCP_AMALGAMATION
+#include "tcp_timer.h"
+#endif
+
+void tcp_timerset_init(tcp_timerset_t *set)
+{
+    for (size_t i = 0; i < TCP_MAX_TIMEOUTS-1; i++)
+        set->pool[i].next = set->pool + i+1;
+    set->pool[TCP_MAX_TIMEOUTS-1].next = NULL;
+    set->free_list = set->pool;
+    set->used_list = NULL;
+}
+
+void tcp_timerset_free(tcp_timerset_t *set)
+{
+    (void) set;
+}
+
+void tcp_timer_disable(tcp_timer_t *timer)
+{
+    tcp_timerset_t *set = timer->set;
+
+    // Pop the timer from the used list
+    if (timer->prev)
+        timer->prev->next = timer->next;
+    else
+        set->used_list = timer->next;
+    if (timer->next)
+        timer->next->prev = timer->prev;
+
+    // Push it into the free list
+    timer->prev = NULL;
+    timer->next = set->free_list;
+    set->free_list = timer;
+}
+
+tcp_timer_t *tcp_timer_create(tcp_timerset_t *set, size_t seconds, 
+                              void (*callback)(void*), void *data)
+{
+    assert(callback);
+
+    if (set->free_list == NULL)
+        // Out of timers! This is really bad.
+        // What can be done to mitigate this?
+        return NULL;
+
+    tcp_timer_t *timer = set->free_list;
+    set->free_list = timer->next;
+    // NOTE: Since the free list is singly linked, there's
+    //       no need to change the prev member of the new
+    //       first item of the free list.
+
+    timer->set = set;
+    timer->deadline = set->current_time + seconds;
+    timer->data = data;
+    timer->callback = callback;
+    
+    // Insert the timer structure into the timer list
+    // in an orderly fashon
+    if (set->used_list == NULL) {
+        // This is the first timer of the list
+        set->used_list = timer;
+        timer->prev = NULL;
+        timer->next = NULL;
+    } else if (timer->deadline < set->used_list->deadline) {
+        // This timer should be the first of the list
+        timer->prev = NULL;
+        timer->next = set->used_list;
+        set->used_list->prev = timer;
+    } else {
+        // The timer isn't the first of the list. We need to
+        // determine at which position it should be inserted
+        //
+        // Scan the list until the timer that needs to come
+        // after the inserted one is reached
+        tcp_timer_t *cursor = set->used_list;
+        while (cursor->next && cursor->next->deadline <= timer->deadline)
+            cursor = cursor->next;
+        tcp_timer_t *prev = cursor;
+        cursor = cursor->next;
+
+        if (cursor) {
+            // The cursor points to the element that needs to
+            // come after. Since we know the inserted item won't
+            // be the first, then this one isn't the first element
+            // of the list either, so its "prev" isn't NULL.
+            assert(cursor->prev);
+            timer->prev = cursor->prev;
+            timer->next = cursor;
+            cursor->prev->next = timer;
+            cursor->prev = timer;
+        } else {
+            // No element that needs to come after was found,
+            // so its position should be the last.
+            prev->next = timer;
+            timer->prev = prev;
+            timer->next = NULL;
+        }
+    }
+    return timer;
+}
+
+void tcp_timerset_step(tcp_timerset_t *set, size_t seconds)
+{
+    set->current_time += seconds;
+
+    if (set->used_list == NULL || set->used_list->deadline > set->current_time)
+        // No timeouts triggered
+        return;
+
+    tcp_timer_t *timedout_head = set->used_list; // We know that at least one timeout triggered
+    tcp_timer_t *timedout_tail; // This has to be determined by the following loop
+
+    // Scan through all of the timeouts that just triggered
+    tcp_timer_t *timeout = set->used_list;
+    while (timeout) {
+
+        if (timeout->deadline > set->current_time)
+            // This timeout didn't trigger, so the last 
+            // timed out timeout was the previous one.
+            break;
+        
+        // Trigger the callback
+        timeout->callback(timeout->data);
+
+        timedout_tail = timeout;
+        timeout = timeout->next;
+    }
+
+    // Now put the list of timed out timeouts back
+    // into the free list
+    if (timedout_tail->next)
+        timedout_tail->next->prev = NULL;
+
+    set->used_list = timedout_tail->next;
+
+    timedout_tail->prev = NULL;
+    timedout_tail->next = set->free_list;
+
+    set->free_list = timedout_head;
+}

src/tcp_timer.h

@@ -0,0 +1,29 @@
+#include <stdint.h>
+
+#define TCP_MAX_TIMERS 1024
+
+typedef struct tcp_timerset_t tcp_timerset_t;
+typedef struct tcp_timer_t    tcp_timer_t;
+
+struct tcp_timer_t {
+    tcp_timerset_t *set;
+    tcp_timer_t *prev;
+    tcp_timer_t *next;
+    uint64_t deadline;
+    void (*callback)(void *data);
+    void *data;
+};
+
+struct tcp_timerset_t {
+    uint64_t current_time;
+    tcp_timer_t *used_list;
+    tcp_timer_t *free_list;
+    tcp_timer_t pool[TCP_MAX_TIMERS];
+};
+
+void tcp_timerset_step(tcp_timerset_t *set, size_t seconds);
+void tcp_timerset_init(tcp_timerset_t *set);
+void tcp_timerset_free(tcp_timerset_t *set);
+void tcp_timer_disable(tcp_timer_t *timer);
+tcp_timer_t *tcp_timer_create(tcp_timerset_t *set, size_t seconds, 
+                              void (*callback)(void*), void *data);