lib: Add basic FRCT mechanisms

This adds the basic FRCT mechanisms to the library. Upon flow alloc or
accept an FRCT instance is now created and used when reading or
writing to the flow. The timerwheel has been refactored to allow
recharging timers and removing them and is now part of the
library. The first SDU sent over the connection has the DRF set and
this initializes the connection. Sender and receiver inactivity timers
are added.

18 files changed, 718 insertions, 269 deletions

diff --git a/include/ouroboros/frct_pci.h b/include/ouroboros/frct_pci.h
new file mode 100644
index 00000000..3a93ac1c
--- /dev/null
+++ b/include/ouroboros/frct_pci.h
@@ -0,0 +1,69 @@
+/*
+ * Ouroboros - Copyright (C) 2016 - 2017
+ *
+ * Protocol Control Information of FRCT
+ *
+ *    Dimitri Staessens <dimitri.staessens@ugent.be>
+ *    Sander Vrijders   <sander.vrijders@ugent.be>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public License
+ * version 2.1 as published by the Free Software Foundation.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., http://www.fsf.org/about/contact/.
+ */
+
+#ifndef OUROBOROS_LIB_FRCT_PCI_H
+#define OUROBOROS_LIB_FRCT_PCI_H
+
+#include <ouroboros/shm_du_buff.h>
+
+#include <stdint.h>
+#include <stdbool.h>
+
+struct frct_pci {
+        uint8_t  type;
+        uint8_t  flags;
+        uint64_t seqno;
+        uint64_t lwe;
+        uint64_t rwe;
+};
+
+enum pdu_types {
+        PDU_TYPE_DATA        = 0x01,
+        PDU_TYPE_ACK         = 0x02,
+        PDU_TYPE_FC          = 0x04,
+        PDU_TYPE_ACK_AND_FC  = (PDU_TYPE_ACK | PDU_TYPE_FC),
+        PDU_TYPE_CONFIG      = 0x08,
+        PDU_TYPE_RENDEZ_VOUS = 0x10
+};
+
+enum config_flags {
+        CONF_RESOURCE_CONTROL = 0x01,
+        CONF_RELIABLE         = 0x02,
+        CONF_ERROR_CHECK      = 0x04,
+        CONF_ORDERED          = 0x08,
+        CONF_PARTIAL          = 0x10
+};
+
+enum data_flags {
+        FLAG_DATA_RUN       = 0x01,
+        FLAG_MORE_FRAGMENTS = 0x02
+};
+
+int frct_pci_ser(struct shm_du_buff * sdb,
+                 struct frct_pci *    pci,
+                 bool                 error_check);
+
+int frct_pci_des(struct shm_du_buff * sdb,
+                 struct frct_pci *    pci,
+                 bool                 error_check);
+
+#endif /* OUROBOROS_LIB_FRCT_PCI_H */
diff --git a/include/ouroboros/hash.h b/include/ouroboros/hash.h
index db47c9fe..49160226 100644
--- a/include/ouroboros/hash.h
+++ b/include/ouroboros/hash.h
@@ -29,6 +29,7 @@
 #include <gcrypt.h>
 #endif
 #include <stdint.h>
+#include <stddef.h>
 
 /* Hash algorithms */
 enum hash_algo {
@@ -58,8 +59,13 @@ enum hash_algo {
 
 uint16_t hash_len(enum hash_algo algo);
 
+void mem_hash(enum hash_algo  algo,
+              void *          dst,
+              const uint8_t * buf,
+              size_t          len);
+
 void str_hash(enum hash_algo algo,
-              void *         buf,
+              void *         dst,
               const char *   str);
 
 #endif /* OUROBOROS_LIB_HASH_H */
diff --git a/include/ouroboros/shm_flow_set.h b/include/ouroboros/shm_flow_set.h
index 5c498336..be2f836b 100644
--- a/include/ouroboros/shm_flow_set.h
+++ b/include/ouroboros/shm_flow_set.h
@@ -58,6 +58,6 @@ void                  shm_flow_set_notify(struct shm_flow_set * set,
 ssize_t               shm_flow_set_wait(const struct shm_flow_set * shm_set,
                                         size_t                      idx,
                                         int *                       fqueue,
-                                        const struct timespec *     timeout);
+                                        const struct timespec *     abstime);
 
 #endif /* OUROBOROS_SHM_FLOW_SET_H */
diff --git a/include/ouroboros/shm_rbuff.h b/include/ouroboros/shm_rbuff.h
index 1557e50c..55d03b41 100644
--- a/include/ouroboros/shm_rbuff.h
+++ b/include/ouroboros/shm_rbuff.h
@@ -50,7 +50,7 @@ int                shm_rbuff_write(struct shm_rbuff * rb,
 ssize_t            shm_rbuff_read(struct shm_rbuff * rb);
 
 ssize_t            shm_rbuff_read_b(struct shm_rbuff *      rb,
-                                    const struct timespec * timeout);
+                                    const struct timespec * abstime);
 
 size_t             shm_rbuff_queued(struct shm_rbuff * rb);
 
diff --git a/include/ouroboros/timerwheel.h b/include/ouroboros/timerwheel.h
new file mode 100644
index 00000000..e259c855
--- /dev/null
+++ b/include/ouroboros/timerwheel.h
@@ -0,0 +1,45 @@
+/*
+ * Ouroboros - Copyright (C) 2016 - 2017
+ *
+ * Ring buffer for incoming SDUs
+ *
+ *    Dimitri Staessens <dimitri.staessens@ugent.be>
+ *    Sander Vrijders   <sander.vrijders@ugent.be>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public License
+ * version 2.1 as published by the Free Software Foundation.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., http://www.fsf.org/about/contact/.
+ */
+
+#ifndef OUROBOROS_LIB_TIMERWHEEL_H
+#define OUROBOROS_LIB_TIMERWHEEL_H
+
+struct timerwheel;
+
+struct timerwheel * timerwheel_create(time_t resolution,
+                                      time_t max_delay);
+
+void                timerwheel_destroy(struct timerwheel * tw);
+
+struct tw_f *       timerwheel_start(struct timerwheel * tw,
+                                     void (* func)(void *),
+                                     void *              arg,
+                                     time_t              delay); /* ms */
+
+int                 timerwheel_restart(struct timerwheel * tw,
+                                       struct tw_f *       f,
+                                       time_t              delay); /* ms */
+
+void                timerwheel_stop(struct timerwheel * tw,
+                                    struct tw_f *       f);
+
+#endif /* OUROBOROS_LIB_TIMERWHEEL_H */
diff --git a/src/ipcpd/CMakeLists.txt b/src/ipcpd/CMakeLists.txt
index 0ead1fed..b2f350dd 100644
--- a/src/ipcpd/CMakeLists.txt
+++ b/src/ipcpd/CMakeLists.txt
@@ -2,13 +2,9 @@ set(IPCP_SOURCES
   # Add source files here
   ${CMAKE_CURRENT_SOURCE_DIR}/ipcp.c
   ${CMAKE_CURRENT_SOURCE_DIR}/shim-data.c
-  ${CMAKE_CURRENT_SOURCE_DIR}/timerwheel.c
   )
 
 add_subdirectory(local)
 add_subdirectory(normal)
 add_subdirectory(shim-udp)
 add_subdirectory(shim-eth-llc)
-if (NOT APPLE)
-  add_subdirectory(tests)
-endif ()
diff --git a/src/ipcpd/tests/CMakeLists.txt b/src/ipcpd/tests/CMakeLists.txt
deleted file mode 100644
index 9b5eeaa1..00000000
--- a/src/ipcpd/tests/CMakeLists.txt
+++ /dev/null
@@ -1,34 +0,0 @@
-get_filename_component(CURRENT_SOURCE_PARENT_DIR
-  ${CMAKE_CURRENT_SOURCE_DIR} DIRECTORY)
-get_filename_component(CURRENT_BINARY_PARENT_DIR
-  ${CMAKE_CURRENT_BINARY_DIR} DIRECTORY)
-
-include_directories(${CMAKE_CURRENT_SOURCE_DIR})
-include_directories(${CMAKE_CURRENT_BINARY_DIR})
-
-include_directories(${CURRENT_SOURCE_PARENT_DIR})
-include_directories(${CURRENT_BINARY_PARENT_DIR})
-
-include_directories(${CMAKE_SOURCE_DIR}/include)
-include_directories(${CMAKE_BINARY_DIR}/include)
-
-get_filename_component(PARENT_PATH ${CMAKE_CURRENT_SOURCE_DIR} DIRECTORY)
-get_filename_component(PARENT_DIR ${PARENT_PATH} NAME)
-
-create_test_sourcelist(${PARENT_DIR}_tests test_suite.c
-  # Add new tests here
-  timerwheel_test.c
-  )
-
-add_executable(${PARENT_DIR}_test EXCLUDE_FROM_ALL ${${PARENT_DIR}_tests})
-target_link_libraries(${PARENT_DIR}_test ouroboros)
-
-add_dependencies(check ${PARENT_DIR}_test)
-
-set(tests_to_run ${${PARENT_DIR}_tests})
-remove(tests_to_run test_suite.c)
-
-foreach (test ${tests_to_run})
-  get_filename_component(test_name ${test} NAME_WE)
-  add_test(${test_name} ${C_TEST_PATH}/${PARENT_DIR}_test ${test_name})
-endforeach (test)
diff --git a/src/ipcpd/timerwheel.h b/src/ipcpd/timerwheel.h
deleted file mode 100644
index 37a6d06a..00000000
--- a/src/ipcpd/timerwheel.h
+++ /dev/null
@@ -1,39 +0,0 @@
-/*
- * Ouroboros - Copyright (C) 2016 - 2017
- *
- * Ring buffer for incoming SDUs
- *
- *    Dimitri Staessens <dimitri.staessens@ugent.be>
- *    Sander Vrijders   <sander.vrijders@ugent.be>
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., http://www.fsf.org/about/contact/.
- */
-
-#ifndef OUROBOROS_IPCPD_TIMERWHEEL_H
-#define OUROBOROS_IPCPD_TIMERWHEEL_H
-
-struct timerwheel;
-
-struct timerwheel * timerwheel_create(unsigned int resolution,
-                                      unsigned int max_delay);
-
-void                timerwheel_destroy(struct timerwheel * tw);
-
-int                 timerwheel_add(struct timerwheel * tw,
-                                   void (* func)(void *),
-                                   void *              arg,
-                                   size_t              arg_len,
-                                   unsigned int        delay); /* ms */
-
-#endif /* OUROBOROS_IPCPD_TIMERWHEEL_H */
diff --git a/src/lib/CMakeLists.txt b/src/lib/CMakeLists.txt
index 550bbc08..728d975a 100644
--- a/src/lib/CMakeLists.txt
+++ b/src/lib/CMakeLists.txt
@@ -86,6 +86,7 @@ set(SOURCE_FILES
   cdap_req.c
   crc32.c
   dev.c
+  frct_pci.c
   hash.c
   hashtable.c
   irm.c
@@ -104,6 +105,7 @@ set(SOURCE_FILES
   shm_rdrbuff.c
   sockets.c
   time_utils.c
+  timerwheel.c
   tpm.c
   utils.c
   )
diff --git a/src/lib/dev.c b/src/lib/dev.c
index 9354855b..e81bf105 100644
--- a/src/lib/dev.c
+++ b/src/lib/dev.c
@@ -34,6 +34,8 @@
 #include <ouroboros/utils.h>
 #include <ouroboros/fqueue.h>
 #include <ouroboros/qoscube.h>
+#include <ouroboros/timerwheel.h>
+#include <ouroboros/frct_pci.h>
 
 #include <stdlib.h>
 #include <string.h>
@@ -41,8 +43,14 @@
 
 #define BUF_SIZE 1500
 
+#define TW_ELEMENTS   6000
+#define TW_RESOLUTION 1   /* ms */
+
+#define MPL 2000 /* ms */
+
 struct flow_set {
         size_t idx;
+        bool   np1_set;
 };
 
 struct fqueue {
@@ -59,6 +67,26 @@ enum port_state {
         PORT_DESTROY
 };
 
+struct frcti {
+        bool          used;
+
+        struct tw_f * snd_inact;
+        bool          snd_drf;
+        uint64_t      snd_lwe;
+        uint64_t      snd_rwe;
+
+        struct tw_f * rcv_inact;
+        bool          rcv_drf;
+        uint64_t      rcv_lwe;
+        uint64_t      rcv_rwe;
+
+        bool          resource_control;
+        bool          reliable;
+        bool          error_check;
+        bool          ordered;
+        bool          partial;
+};
+
 struct port {
         int             fd;
 
@@ -89,10 +117,14 @@ struct {
         struct shm_rdrbuff *  rdrb;
         struct shm_flow_set * fqset;
 
+        struct timerwheel *   tw;
+        int                   tw_users;
+
         struct bmp *          fds;
         struct bmp *          fqueues;
         struct flow *         flows;
         struct port *         ports;
+        struct frcti *        frcti;
 
         pthread_rwlock_t      lock;
 } ai;
@@ -203,6 +235,242 @@ static int api_announce(char * ap_name)
         return ret;
 }
 
+/* Call under flows lock */
+static int finalize_write(int    fd,
+                          size_t idx)
+{
+        if (shm_rbuff_write(ai.flows[fd].tx_rb, idx) < 0)
+                return -ENOTALLOC;
+
+        shm_flow_set_notify(ai.flows[fd].set, ai.flows[fd].port_id);
+
+        return 0;
+}
+
+static int frcti_init(int fd)
+{
+        ai.frcti[fd].used = true;
+
+        ai.frcti[fd].snd_drf = true;
+        ai.frcti[fd].snd_lwe = 0;
+        ai.frcti[fd].snd_rwe = 0;
+
+        ai.frcti[fd].rcv_drf = true;
+        ai.frcti[fd].rcv_lwe = 0;
+        ai.frcti[fd].rcv_rwe = 0;
+
+        return 0;
+}
+
+static void frcti_fini(int fd)
+{
+        struct frcti * frcti;
+
+        frcti = &(ai.frcti[fd]);
+
+        frcti->used = false;
+
+        /* FIXME: We actually need to wait until these timers become NULL. */
+        if (frcti->snd_inact != NULL)
+                timerwheel_stop(ai.tw, frcti->snd_inact);
+
+        if (frcti->rcv_inact != NULL)
+                timerwheel_stop(ai.tw, frcti->rcv_inact);
+}
+
+static int frcti_configure(int         fd,
+                           qosspec_t * qos)
+{
+        /* FIXME: Send configuration message here to other side. */
+
+        (void) fd;
+        (void) qos;
+
+        return 0;
+}
+
+static void frcti_snd_inactivity(void * arg)
+{
+        struct frcti *  frcti;
+
+        pthread_rwlock_wrlock(&ai.lock);
+
+        frcti = (struct frcti * ) arg;
+
+        frcti->snd_drf = true;
+        frcti->snd_inact = NULL;
+
+        pthread_rwlock_unlock(&ai.lock);
+}
+
+/* Called under flows lock */
+static int frcti_write(int                  fd,
+                       struct shm_du_buff * sdb)
+{
+        struct frcti *  frcti;
+        struct frct_pci pci;
+
+        memset(&pci, 0, sizeof(pci));
+
+        frcti = &(ai.frcti[fd]);
+
+        /*
+         * Set the DRF in the first packet of a new run of SDUs,
+         * otherwise simply recharge the timer.
+         */
+        if (frcti->snd_drf) {
+                frcti->snd_inact = timerwheel_start(ai.tw, frcti_snd_inactivity,
+                                                    frcti, 2 * MPL);
+                if (frcti->snd_inact == NULL)
+                        return -1;
+
+                pci.flags |= FLAG_DATA_RUN;
+                frcti->snd_drf = false;
+        } else {
+                if (timerwheel_restart(ai.tw, frcti->snd_inact, 2 * MPL))
+                        return -1;
+        }
+
+        pci.seqno = frcti->snd_lwe++;
+        pci.type |= PDU_TYPE_DATA;
+
+        if (frct_pci_ser(sdb, &pci, frcti->error_check))
+                return -1;
+
+        if (finalize_write(fd, shm_du_buff_get_idx(sdb)))
+                return -ENOTALLOC;
+
+        return 0;
+}
+
+static void frcti_rcv_inactivity(void * arg)
+{
+        struct frcti *  frcti;
+
+        pthread_rwlock_wrlock(&ai.lock);
+
+        frcti = (struct frcti * ) arg;
+
+        frcti->rcv_drf = true;
+        frcti->rcv_inact = NULL;
+
+        pthread_rwlock_unlock(&ai.lock);
+}
+
+static ssize_t frcti_read(int fd)
+{
+        ssize_t              idx = -1;
+        struct timespec      abstime;
+        struct frcti *       frcti;
+        struct frct_pci      pci;
+        struct shm_du_buff * sdb;
+
+        pthread_rwlock_rdlock(&ai.lock);
+
+        if (ai.flows[fd].oflags & FLOW_O_NONBLOCK) {
+                idx = shm_rbuff_read(ai.flows[fd].rx_rb);
+                pthread_rwlock_unlock(&ai.lock);
+        } else {
+                struct shm_rbuff * rb   = ai.flows[fd].rx_rb;
+                bool timeo = ai.flows[fd].timesout;
+                struct timespec timeout = ai.flows[fd].rcv_timeo;
+
+                pthread_rwlock_unlock(&ai.lock);
+
+                if (timeo) {
+                        clock_gettime(PTHREAD_COND_CLOCK, &abstime);
+                        ts_add(&abstime, &timeout, &abstime);
+                        idx = shm_rbuff_read_b(rb, &abstime);
+                } else {
+                        idx = shm_rbuff_read_b(rb, NULL);
+                }
+        }
+
+        if (idx < 0)
+                return idx;
+
+        pthread_rwlock_rdlock(&ai.lock);
+
+        frcti = &(ai.frcti[fd]);
+
+        sdb = shm_rdrbuff_get(ai.rdrb, idx);
+
+        /* SDU may be corrupted. */
+        if (frct_pci_des(sdb, &pci, frcti->error_check)) {
+                pthread_rwlock_unlock(&ai.lock);
+                shm_rdrbuff_remove(ai.rdrb, idx);
+                return -1;
+        }
+
+        /* We don't accept packets when there is no inactivity timer. */
+        if (frcti->rcv_drf && !(pci.flags & FLAG_DATA_RUN)) {
+                pthread_rwlock_unlock(&ai.lock);
+                shm_rdrbuff_remove(ai.rdrb, idx);
+                return -1;
+        }
+
+        /*
+         * If there is an inactivity timer and the DRF is set,
+         * reset the state of the connection.
+         */
+        if (pci.flags & FLAG_DATA_RUN) {
+                frcti->rcv_drf = true;
+                if (frcti->rcv_inact != NULL)
+                        timerwheel_stop(ai.tw, frcti->rcv_inact);
+                frcti->rcv_lwe = pci.seqno;
+        }
+
+        /*
+         * Start receiver inactivity if this packet has the DRF,
+         * otherwise simply restart it.
+         */
+        if (frcti->rcv_drf) {
+                frcti->rcv_inact = timerwheel_start(ai.tw, frcti_rcv_inactivity,
+                                                    frcti, 3 * MPL);
+                if (frcti->rcv_inact == NULL) {
+                        pthread_rwlock_unlock(&ai.lock);
+                        shm_rdrbuff_remove(ai.rdrb, idx);
+                        return -1;
+                }
+
+                frcti->rcv_drf = false;
+        } else {
+                if (timerwheel_restart(ai.tw, frcti->rcv_inact, 3 * MPL)) {
+                        pthread_rwlock_unlock(&ai.lock);
+                        shm_rdrbuff_remove(ai.rdrb, idx);
+                        return -1;
+                }
+        }
+
+        pthread_rwlock_unlock(&ai.lock);
+
+        return idx;
+}
+
+static int frcti_event_wait(struct flow_set *       set,
+                            struct fqueue *         fq,
+                            const struct timespec * timeout)
+{
+        int ret;
+
+        assert(set);
+        assert(fq);
+        assert(timeout);
+
+        /*
+         * FIXME: Return the fq only if a data SDU
+         * for the application is available.
+         */
+
+        ret = shm_flow_set_wait(ai.fqset, set->idx, fq->fqueue, timeout);
+        if (ret == -ETIMEDOUT) {
+                fq->fqsize = 0;
+                return -ETIMEDOUT;
+        }
+
+        return ret;
+}
+
 static void flow_clear(int fd)
 {
         assert(!(fd < 0));
@@ -230,6 +498,9 @@ static void flow_fini(int fd)
         if (ai.flows[fd].set != NULL)
                 shm_flow_set_close(ai.flows[fd].set);
 
+        if (ai.frcti[fd].used)
+                frcti_fini(fd);
+
         flow_clear(fd);
 }
 
@@ -316,8 +587,14 @@ int ouroboros_init(const char * ap_name)
         if (ai.flows == NULL)
                 goto fail_flows;
 
-        for (i = 0; i < AP_MAX_FLOWS; ++i)
+        ai.frcti = malloc(sizeof(*ai.frcti) * AP_MAX_FLOWS);
+        if (ai.frcti == NULL)
+                goto fail_frcti;
+
+        for (i = 0; i < AP_MAX_FLOWS; ++i) {
                 flow_clear(i);
+                frcti_fini(i);
+        }
 
         ai.ports = malloc(sizeof(*ai.ports) * IRMD_MAX_FLOWS);
         if (ai.ports == NULL)
@@ -353,8 +630,15 @@ int ouroboros_init(const char * ap_name)
         if (pthread_rwlock_init(&ai.lock, NULL))
                 goto fail_lock;
 
+        ai.tw = timerwheel_create(TW_RESOLUTION,
+                                  TW_RESOLUTION * TW_ELEMENTS);
+        if (ai.tw == NULL)
+                goto fail_timerwheel;
+
         return 0;
 
+ fail_timerwheel:
+        pthread_rwlock_destroy(&ai.lock);
  fail_lock:
         for (i = 0; i < IRMD_MAX_FLOWS; ++i)
                 pthread_cond_destroy(&ai.ports[i].state_cond);
@@ -366,11 +650,13 @@ int ouroboros_init(const char * ap_name)
  fail_ap_name:
         free(ai.ports);
  fail_ports:
+        free(ai.frcti);
+ fail_frcti:
         free(ai.flows);
  fail_flows:
         shm_rdrbuff_close(ai.rdrb);
  fail_rdrb:
-      shm_flow_set_destroy(ai.fqset);
+        shm_flow_set_destroy(ai.fqset);
  fail_fqset:
         bmp_destroy(ai.fqueues);
  fail_fqueues:
@@ -409,6 +695,9 @@ void ouroboros_fini()
 
         shm_rdrbuff_close(ai.rdrb);
 
+        if (ai.tw != NULL)
+                timerwheel_destroy(ai.tw);
+
         free(ai.flows);
         free(ai.ports);
 
@@ -463,9 +752,15 @@ int flow_accept(qosspec_t *             qs,
         if (fd < 0)
                 return fd;
 
+        pthread_rwlock_wrlock(&ai.lock);
+
+        frcti_init(fd);
+
         if (qs != NULL)
                 *qs = ai.flows[fd].spec;
 
+        pthread_rwlock_unlock(&ai.lock);
+
         return fd;
 }
 
@@ -505,7 +800,7 @@ int flow_alloc(const char *            dst_name,
                 return -EIRMD;
         }
 
-        if (recv_msg->result !=  0) {
+        if (recv_msg->result != 0) {
                 int res =  recv_msg->result;
                 irm_msg__free_unpacked(recv_msg, NULL);
                 return res;
@@ -520,6 +815,22 @@ int flow_alloc(const char *            dst_name,
 
         irm_msg__free_unpacked(recv_msg, NULL);
 
+        if (fd < 0)
+                return fd;
+
+        pthread_rwlock_wrlock(&ai.lock);
+
+        frcti_init(fd);
+
+        if (frcti_configure(fd, qs)) {
+                flow_fini(fd);
+                bmp_release(ai.fds, fd);
+                pthread_rwlock_unlock(&ai.lock);
+                return -1;
+        }
+
+        pthread_rwlock_unlock(&ai.lock);
+
         return fd;
 }
 
@@ -720,34 +1031,31 @@ ssize_t flow_write(int          fd,
                         return idx;
                 }
 
-                if (shm_rbuff_write(ai.flows[fd].tx_rb, idx) < 0) {
-                        shm_rdrbuff_remove(ai.rdrb, idx);
-                        pthread_rwlock_unlock(&ai.lock);
-                        return -ENOTALLOC;
-                }
         } else { /* blocking */
-                struct shm_rdrbuff * rdrb = ai.rdrb;
-                struct shm_rbuff * tx_rb  = ai.flows[fd].tx_rb;
-
                 pthread_rwlock_unlock(&ai.lock);
 
-                assert(tx_rb);
-
-                idx = shm_rdrbuff_write_b(rdrb,
+                idx = shm_rdrbuff_write_b(ai.rdrb,
                                           DU_BUFF_HEADSPACE,
                                           DU_BUFF_TAILSPACE,
                                           buf,
                                           count);
 
-                if (shm_rbuff_write(tx_rb, idx) < 0) {
-                        shm_rdrbuff_remove(rdrb, idx);
-                        return -ENOTALLOC;
-                }
-
                 pthread_rwlock_rdlock(&ai.lock);
         }
 
-        shm_flow_set_notify(ai.flows[fd].set, ai.flows[fd].port_id);
+        if (!ai.frcti[fd].used) {
+                if (finalize_write(fd, idx)) {
+                        pthread_rwlock_unlock(&ai.lock);
+                        shm_rdrbuff_remove(ai.rdrb, idx);
+                        return -ENOTALLOC;
+                }
+        } else {
+                if (frcti_write(fd, shm_rdrbuff_get(ai.rdrb, idx))) {
+                        pthread_rwlock_unlock(&ai.lock);
+                        shm_rdrbuff_remove(ai.rdrb, idx);
+                        return -1;
+                }
+        }
 
         pthread_rwlock_unlock(&ai.lock);
 
@@ -772,21 +1080,12 @@ ssize_t flow_read(int    fd,
                 return -ENOTALLOC;
         }
 
-        if (ai.flows[fd].oflags & FLOW_O_NONBLOCK) {
-                idx = shm_rbuff_read(ai.flows[fd].rx_rb);
-                pthread_rwlock_unlock(&ai.lock);
-        } else {
-                struct shm_rbuff * rb   = ai.flows[fd].rx_rb;
-                bool timeo = ai.flows[fd].timesout;
-                struct timespec timeout = ai.flows[fd].rcv_timeo;
-
-                pthread_rwlock_unlock(&ai.lock);
+        pthread_rwlock_unlock(&ai.lock);
 
-                if (timeo)
-                        idx = shm_rbuff_read_b(rb, &timeout);
-                else
-                        idx = shm_rbuff_read_b(rb, NULL);
-        }
+        if (!ai.frcti[fd].used)
+                idx = shm_rbuff_read(ai.flows[fd].rx_rb);
+        else
+                idx = frcti_read(fd);
 
         if (idx < 0) {
                 assert(idx == -EAGAIN || idx == -ETIMEDOUT);
@@ -823,6 +1122,8 @@ struct flow_set * flow_set_create()
                 return NULL;
         }
 
+        set->np1_set = false;
+
         pthread_rwlock_unlock(&ai.lock);
 
         return set;
@@ -891,6 +1192,9 @@ int flow_set_add(struct flow_set * set,
         for (i = 0; i < sdus; i++)
                 shm_flow_set_notify(ai.fqset, ai.flows[fd].port_id);
 
+        if (ai.frcti[fd].used)
+                set->np1_set = true;
+
         pthread_rwlock_unlock(&ai.lock);
 
         return ret;
@@ -960,7 +1264,8 @@ int flow_event_wait(struct flow_set *       set,
                     struct fqueue *         fq,
                     const struct timespec * timeout)
 {
-        ssize_t ret;
+        ssize_t         ret;
+        struct timespec abstime;
 
         if (set == NULL || fq == NULL)
                 return -EINVAL;
@@ -970,7 +1275,17 @@ int flow_event_wait(struct flow_set *       set,
 
         assert(!fq->next);
 
-        ret = shm_flow_set_wait(ai.fqset, set->idx, fq->fqueue, timeout);
+        if (timeout != NULL) {
+                clock_gettime(PTHREAD_COND_CLOCK, &abstime);
+                ts_add(&abstime, timeout, &abstime);
+        }
+
+        if (set->np1_set)
+                ret = frcti_event_wait(set, fq, &abstime);
+        else
+                ret = shm_flow_set_wait(ai.fqset, set->idx,
+                                        fq->fqueue, &abstime);
+
         if (ret == -ETIMEDOUT) {
                 fq->fqsize = 0;
                 return -ETIMEDOUT;
@@ -1132,9 +1447,8 @@ int ipcp_flow_read(int                   fd,
 {
         ssize_t idx = -1;
         int port_id = -1;
-        struct shm_rbuff * rb;
 
-        assert(fd >=0);
+        assert(fd >= 0);
         assert(sdb);
 
         pthread_rwlock_rdlock(&ai.lock);
@@ -1144,11 +1458,13 @@ int ipcp_flow_read(int                   fd,
                 return -ENOTALLOC;
         }
 
-        rb = ai.flows[fd].rx_rb;
-
         pthread_rwlock_unlock(&ai.lock);
 
-        idx = shm_rbuff_read(rb);
+        if (!ai.frcti[fd].used)
+                idx = shm_rbuff_read(ai.flows[fd].rx_rb);
+        else
+                idx = frcti_read(fd);
+
         if (idx < 0)
                 return idx;
 
@@ -1160,8 +1476,6 @@ int ipcp_flow_read(int                   fd,
 int ipcp_flow_write(int                  fd,
                     struct shm_du_buff * sdb)
 {
-        size_t idx;
-
         if (sdb == NULL)
                 return -EINVAL;
 
@@ -1179,10 +1493,17 @@ int ipcp_flow_write(int                  fd,
 
         assert(ai.flows[fd].tx_rb);
 
-        idx = shm_du_buff_get_idx(sdb);
-
-        shm_rbuff_write(ai.flows[fd].tx_rb, idx);
-        shm_flow_set_notify(ai.flows[fd].set, ai.flows[fd].port_id);
+        if (!ai.frcti[fd].used) {
+                if (finalize_write(fd, shm_du_buff_get_idx(sdb))) {
+                        pthread_rwlock_unlock(&ai.lock);
+                        return -ENOTALLOC;
+                }
+        } else {
+                if (frcti_write(fd, sdb)) {
+                        pthread_rwlock_unlock(&ai.lock);
+                        return -1;
+                }
+        }
 
         pthread_rwlock_unlock(&ai.lock);
 
@@ -1274,32 +1595,11 @@ int local_flow_write(int    fd,
                 return -ENOTALLOC;
         }
 
-        shm_rbuff_write(ai.flows[fd].tx_rb, idx);
-
-        shm_flow_set_notify(ai.flows[fd].set, ai.flows[fd].port_id);
-
-        pthread_rwlock_unlock(&ai.lock);
-
-        return 0;
-}
-
-int ipcp_read_shim(int                   fd,
-                   struct shm_du_buff ** sdb)
-{
-        ssize_t idx;
-
-        pthread_rwlock_rdlock(&ai.lock);
-
-        assert(ai.flows[fd].rx_rb);
-
-        idx = shm_rbuff_read(ai.flows[fd].rx_rb);
-        if (idx < 0) {
+        if (finalize_write(fd, idx)) {
                 pthread_rwlock_unlock(&ai.lock);
-                return -EAGAIN;
+                return -ENOTALLOC;
         }
 
-        *sdb = shm_rdrbuff_get(ai.rdrb, idx);
-
         pthread_rwlock_unlock(&ai.lock);
 
         return 0;
diff --git a/src/lib/frct_pci.c b/src/lib/frct_pci.c
new file mode 100644
index 00000000..92cf8cd9
--- /dev/null
+++ b/src/lib/frct_pci.c
@@ -0,0 +1,105 @@
+/*
+ * Ouroboros - Copyright (C) 2016 - 2017
+ *
+ * Protocol Control Information of FRCT
+ *
+ *    Dimitri Staessens <dimitri.staessens@ugent.be>
+ *    Sander Vrijders   <sander.vrijders@ugent.be>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public License
+ * version 2.1 as published by the Free Software Foundation.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., http://www.fsf.org/about/contact/.
+ */
+
+#include <ouroboros/config.h>
+#include <ouroboros/frct_pci.h>
+#include <ouroboros/hash.h>
+#include <ouroboros/errno.h>
+
+#include <assert.h>
+#include <string.h>
+
+#define TYPE_SIZE  1
+#define SEQNO_SIZE 8
+#define FLAGS_SIZE 1
+
+/* FIXME: Head size will differ on type */
+#define HEAD_SIZE TYPE_SIZE + FLAGS_SIZE + SEQNO_SIZE
+
+int frct_pci_ser(struct shm_du_buff * sdb,
+                 struct frct_pci *    pci,
+                 bool                 error_check)
+{
+        uint8_t * head;
+        uint8_t * tail;
+
+        assert(sdb);
+        assert(pci);
+
+        head = shm_du_buff_head_alloc(sdb, HEAD_SIZE);
+        if (head == NULL)
+                return -EPERM;
+
+        memcpy(head, &pci->type, TYPE_SIZE);
+        memcpy(head + TYPE_SIZE, &pci->flags, FLAGS_SIZE);
+        memcpy(head + TYPE_SIZE + FLAGS_SIZE, &pci->seqno, SEQNO_SIZE);
+
+        if (error_check) {
+                tail = shm_du_buff_tail_alloc(sdb, hash_len(HASH_CRC32));
+                if (tail == NULL) {
+                        shm_du_buff_head_release(sdb, HEAD_SIZE);
+                        return -EPERM;
+                }
+
+                *((uint32_t *) tail) = 0;
+                mem_hash(HASH_CRC32, (uint32_t *) tail, head, tail - head);
+        }
+
+        return 0;
+}
+
+int frct_pci_des(struct shm_du_buff * sdb,
+                 struct frct_pci *    pci,
+                 bool                 error_check)
+{
+        uint8_t * head;
+        uint8_t * tail;
+        uint32_t  crc;
+
+        assert(sdb);
+        assert(pci);
+
+        head = shm_du_buff_head(sdb);
+
+         /* FIXME: Depending on the type a different deserialization */
+        memcpy(&pci->type, head, TYPE_SIZE);
+        memcpy(&pci->flags, head + TYPE_SIZE, FLAGS_SIZE);
+        memcpy(&pci->seqno, head + TYPE_SIZE + FLAGS_SIZE, SEQNO_SIZE);
+
+        if (error_check) {
+                tail = shm_du_buff_tail(sdb);
+                if (tail == NULL)
+                        return -EPERM;
+
+                mem_hash(HASH_CRC32, &crc, head, tail - head);
+
+                /* Corrupted SDU */
+                if (crc != 0)
+                        return -1;
+
+                shm_du_buff_tail_release(sdb, hash_len(HASH_CRC32));
+        }
+
+        shm_du_buff_head_release(sdb, HEAD_SIZE);
+
+        return 0;
+}
diff --git a/src/lib/hash.c b/src/lib/hash.c
index d8cabfd3..e062a0ad 100644
--- a/src/lib/hash.c
+++ b/src/lib/hash.c
@@ -64,45 +64,46 @@ uint16_t hash_len(enum hash_algo algo)
 #endif
 }
 
-void str_hash(enum hash_algo algo,
-              void *         buf,
-              const char *   str)
+void mem_hash(enum hash_algo  algo,
+              void *          dst,
+              const uint8_t * buf,
+              size_t          len)
 {
 #ifdef HAVE_LIBGCRYPT
-        gcry_md_hash_buffer(algo, buf, str, strlen(str));
+        gcry_md_hash_buffer(algo, dst, buf, len);
 #else
         struct sha3_ctx sha3_ctx;
         struct md5_ctx md5_ctx;
 
         switch (algo) {
         case HASH_CRC32:
-                memset(buf, 0, CRC32_HASH_LEN);
-                crc32((uint32_t *) buf, str, strlen(str));
+                memset(dst, 0, CRC32_HASH_LEN);
+                crc32((uint32_t *) dst, buf, len);
                 break;
         case HASH_MD5:
                 rhash_md5_init(&md5_ctx);
-                rhash_md5_update(&md5_ctx, str, strlen(str));
-                rhash_md5_final(&md5_ctx, (uint8_t *) buf);
+                rhash_md5_update(&md5_ctx, buf, len);
+                rhash_md5_final(&md5_ctx, (uint8_t *) dst);
                 break;
         case HASH_SHA3_224:
                 rhash_sha3_224_init(&sha3_ctx);
-                rhash_sha3_update(&sha3_ctx, str, strlen(str));
-                rhash_sha3_final(&sha3_ctx, (uint8_t *) buf);
+                rhash_sha3_update(&sha3_ctx, buf, len);
+                rhash_sha3_final(&sha3_ctx, (uint8_t *) dst);
                 break;
         case HASH_SHA3_256:
                 rhash_sha3_256_init(&sha3_ctx);
-                rhash_sha3_update(&sha3_ctx, str, strlen(str));
-                rhash_sha3_final(&sha3_ctx, (uint8_t *) buf);
+                rhash_sha3_update(&sha3_ctx, buf, len);
+                rhash_sha3_final(&sha3_ctx, (uint8_t *) dst);
                 break;
         case HASH_SHA3_384:
                 rhash_sha3_384_init(&sha3_ctx);
-                rhash_sha3_update(&sha3_ctx, str, strlen(str));
-                rhash_sha3_final(&sha3_ctx, (uint8_t *) buf);
+                rhash_sha3_update(&sha3_ctx, buf, len);
+                rhash_sha3_final(&sha3_ctx, (uint8_t *) dst);
                 break;
         case HASH_SHA3_512:
                 rhash_sha3_512_init(&sha3_ctx);
-                rhash_sha3_update(&sha3_ctx, str, strlen(str));
-                rhash_sha3_final(&sha3_ctx, (uint8_t *) buf);
+                rhash_sha3_update(&sha3_ctx, buf, len);
+                rhash_sha3_final(&sha3_ctx, (uint8_t *) dst);
                 break;
         default:
                 assert(false);
@@ -110,3 +111,10 @@ void str_hash(enum hash_algo algo,
         }
 #endif
 }
+
+void str_hash(enum hash_algo algo,
+              void *         dst,
+              const char *   str)
+{
+        return mem_hash(algo, dst, (const uint8_t *) str, strlen(str));
+}
diff --git a/src/lib/shm_flow_set.c b/src/lib/shm_flow_set.c
index cd6946d4..2f1d4e33 100644
--- a/src/lib/shm_flow_set.c
+++ b/src/lib/shm_flow_set.c
@@ -326,10 +326,9 @@ void shm_flow_set_notify(struct shm_flow_set * set,
 ssize_t shm_flow_set_wait(const struct shm_flow_set * set,
                           size_t                      idx,
                           int *                       fqueue,
-                          const struct timespec *     timeout)
+                          const struct timespec *     abstime)
 {
         ssize_t ret = 0;
-        struct timespec abstime;
 
         assert(set);
         assert(idx < AP_MAX_FQUEUES);
@@ -341,19 +340,15 @@ ssize_t shm_flow_set_wait(const struct shm_flow_set * set,
         if (pthread_mutex_lock(set->lock) == EOWNERDEAD)
                 pthread_mutex_consistent(set->lock);
 #endif
-        if (timeout != NULL) {
-                clock_gettime(PTHREAD_COND_CLOCK, &abstime);
-                ts_add(&abstime, timeout, &abstime);
-        }
 
         pthread_cleanup_push((void(*)(void *))pthread_mutex_unlock,
                              (void *) set->lock);
 
         while (set->heads[idx] == 0 && ret != -ETIMEDOUT) {
-                if (timeout != NULL)
+                if (abstime != NULL)
                         ret = -pthread_cond_timedwait(set->conds + idx,
                                                       set->lock,
-                                                      &abstime);
+                                                      abstime);
                 else
                         ret = -pthread_cond_wait(set->conds + idx,
                                                  set->lock);
diff --git a/src/lib/shm_rbuff_ll.c b/src/lib/shm_rbuff_ll.c
index 33e236b0..b420b785 100644
--- a/src/lib/shm_rbuff_ll.c
+++ b/src/lib/shm_rbuff_ll.c
@@ -281,9 +281,8 @@ ssize_t shm_rbuff_read(struct shm_rbuff * rb)
 }
 
 ssize_t shm_rbuff_read_b(struct shm_rbuff *      rb,
-                         const struct timespec * timeout)
+                         const struct timespec * abstime)
 {
-        struct timespec abstime;
         ssize_t idx = -1;
 
         assert(rb);
@@ -293,11 +292,6 @@ ssize_t shm_rbuff_read_b(struct shm_rbuff *      rb,
         if (idx != -EAGAIN)
                 return idx;
 
-        if (timeout != NULL) {
-                clock_gettime(PTHREAD_COND_CLOCK, &abstime);
-                ts_add(&abstime, timeout, &abstime);
-        }
-
 #ifndef HAVE_ROBUST_MUTEX
         pthread_mutex_lock(rb->lock);
 #else
@@ -308,10 +302,10 @@ ssize_t shm_rbuff_read_b(struct shm_rbuff *      rb,
                              (void *) rb->lock);
 
         while (shm_rbuff_empty(rb) && (idx != -ETIMEDOUT)) {
-                if (timeout != NULL)
+                if (abstime != NULL)
                         idx = -pthread_cond_timedwait(rb->add,
                                                       rb->lock,
-                                                      &abstime);
+                                                      abstime);
                 else
                         idx = -pthread_cond_wait(rb->add, rb->lock);
 #ifdef HAVE_ROBUST_MUTEX
diff --git a/src/lib/shm_rbuff_pthr.c b/src/lib/shm_rbuff_pthr.c
index 44001458..7dc5f5d9 100644
--- a/src/lib/shm_rbuff_pthr.c
+++ b/src/lib/shm_rbuff_pthr.c
@@ -284,18 +284,12 @@ ssize_t shm_rbuff_read(struct shm_rbuff * rb)
 }
 
 ssize_t shm_rbuff_read_b(struct shm_rbuff *      rb,
-                         const struct timespec * timeout)
+                         const struct timespec * abstime)
 {
-        struct timespec abstime;
         ssize_t idx = -1;
 
         assert(rb);
 
-        if (timeout != NULL) {
-                clock_gettime(PTHREAD_COND_CLOCK, &abstime);
-                ts_add(&abstime, timeout, &abstime);
-        }
-
 #ifndef HAVE_ROBUST_MUTEX
         pthread_mutex_lock(rb->lock);
 #else
@@ -306,10 +300,10 @@ ssize_t shm_rbuff_read_b(struct shm_rbuff *      rb,
                              (void *) rb->lock);
 
         while (shm_rbuff_empty(rb) && (idx != -ETIMEDOUT)) {
-                if (timeout != NULL)
+                if (abstime != NULL)
                         idx = -pthread_cond_timedwait(rb->add,
                                                       rb->lock,
-                                                      &abstime);
+                                                      abstime);
                 else
                         idx = -pthread_cond_wait(rb->add, rb->lock);
 #ifdef HAVE_ROBUST_MUTEX
diff --git a/src/lib/tests/CMakeLists.txt b/src/lib/tests/CMakeLists.txt
index 41c2074a..fd3c1c6a 100644
--- a/src/lib/tests/CMakeLists.txt
+++ b/src/lib/tests/CMakeLists.txt
@@ -11,6 +11,7 @@ create_test_sourcelist(${PARENT_DIR}_tests test_suite.c
   rib_test.c
   sha3_test.c
   time_utils_test.c
+  timerwheel_test.c
   )
 
 add_executable(${PARENT_DIR}_test EXCLUDE_FROM_ALL ${${PARENT_DIR}_tests})
diff --git a/src/ipcpd/tests/timerwheel_test.c b/src/lib/tests/timerwheel_test.c
index 6ba1b890..d9ca164e 100644
--- a/src/ipcpd/tests/timerwheel_test.c
+++ b/src/lib/tests/timerwheel_test.c
@@ -51,6 +51,9 @@ int timerwheel_test(int argc, char ** argv)
         int check_total = 0;
 
         int i;
+        int var = 5;
+
+        struct tw_f * f;
 
         (void) argc;
         (void) argv;
@@ -75,13 +78,12 @@ int timerwheel_test(int argc, char ** argv)
 
         for (i = 0; i < additions; ++i) {
                 int delay = rand() % (resolution * elements);
-                int var = rand() % 5;
                 check_total += var;
-                if (timerwheel_add(tw,
-                                   (void (*)(void *)) add,
-                                   (void *) &var,
-                                   sizeof(var),
-                                   delay)) {
+                f = timerwheel_start(tw,
+                                     (void (*)(void *)) add,
+                                     (void *) &var,
+                                     delay);
+                if (f == NULL) {
                         printf("Failed to add function.");
                         return -1;
                 }
diff --git a/src/ipcpd/timerwheel.c b/src/lib/timerwheel.c
index 6086181a..7e2779d0 100644
--- a/src/ipcpd/timerwheel.c
+++ b/src/lib/timerwheel.c
@@ -6,17 +6,17 @@
  *    Dimitri Staessens <dimitri.staessens@ugent.be>
  *    Sander Vrijders   <sander.vrijders@ugent.be>
  *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public License
+ * version 2.1 as published by the Free Software Foundation.
  *
- * This program is distributed in the hope that it will be useful,
+ * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
  *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
  * Foundation, Inc., http://www.fsf.org/about/contact/.
  */
 
@@ -83,8 +83,6 @@ static void tw_el_fini(struct tw_el * e)
         list_for_each_safe(p, h, &e->funcs) {
                 struct tw_f * f = list_entry(p, struct tw_f, next);
                 list_del(&f->next);
-                if (f->arg != NULL)
-                        free(f->arg);
         }
 }
 
@@ -140,8 +138,6 @@ static void * worker(void * o)
                         list_del(&f->next);
                         pthread_mutex_unlock(&tw->lock);
                         f->func(f->arg);
-                        if (f->arg != NULL)
-                                free(f->arg);
                         free(f);
 
                         pthread_mutex_lock(&tw->lock);
@@ -194,8 +190,8 @@ static void * movement(void * o)
         return (void *) 0;
 }
 
-struct timerwheel * timerwheel_create(unsigned int resolution,
-                                      unsigned int max_delay)
+struct timerwheel * timerwheel_create(time_t resolution,
+                                      time_t max_delay)
 {
         struct timespec now = {0, 0};
         struct timespec res_ts = {resolution / 1000,
@@ -221,10 +217,8 @@ struct timerwheel * timerwheel_create(unsigned int resolution,
                 tw->elements <<= 1;
 
         tw->wheel = malloc(sizeof(*tw->wheel) * tw->elements);
-        if (tw->wheel == NULL) {
-                free(tw);
-                return NULL;
-        }
+        if (tw->wheel == NULL)
+                goto fail_wheel_malloc;
 
         tw->resolution = resolution;
 
@@ -233,35 +227,20 @@ struct timerwheel * timerwheel_create(unsigned int resolution,
 
         list_head_init(&tw->wq);
 
-        if (pthread_mutex_init(&tw->lock, NULL)) {
-                free(tw->wheel);
-                free(tw);
-                return NULL;
-        }
+        if (pthread_mutex_init(&tw->lock, NULL))
+                goto fail_lock_init;
 
-        if (pthread_mutex_init(&tw->s_lock, NULL)) {
-                pthread_mutex_destroy(&tw->lock);
-                free(tw->wheel);
-                free(tw);
-                return NULL;
-        }
+        if (pthread_mutex_init(&tw->s_lock, NULL))
+                goto fail_s_lock_init;
+
+        if (pthread_condattr_init(&cattr))
+                goto fail_cond_init;
 
-        if (pthread_condattr_init(&cattr)) {
-                pthread_mutex_destroy(&tw->lock);
-                free(tw->wheel);
-                free(tw);
-                return NULL;
-        }
 #ifndef __APPLE__
         pthread_condattr_setclock(&cattr, PTHREAD_COND_CLOCK);
 #endif
-        if (pthread_cond_init(&tw->work, &cattr)) {
-                pthread_mutex_destroy(&tw->s_lock);
-                pthread_mutex_destroy(&tw->lock);
-                free(tw->wheel);
-                free(tw);
-                return NULL;
-        }
+        if (pthread_cond_init(&tw->work, &cattr))
+                goto fail_cond_init;
 
         tw->pos = 0;
         tw->state = TW_RUNNING;
@@ -275,27 +254,29 @@ struct timerwheel * timerwheel_create(unsigned int resolution,
                 ts_add(&now, &res_ts, &now);
         }
 
-        if (pthread_create(&tw->worker, NULL, worker, (void *) tw)) {
-                pthread_cond_destroy(&tw->work);
-                pthread_mutex_destroy(&tw->s_lock);
-                pthread_mutex_destroy(&tw->lock);
-                free(tw->wheel);
-                free(tw);
-                return NULL;
-        }
+        if (pthread_create(&tw->worker, NULL, worker, (void *) tw))
+                goto fail_worker_create;
 
         if (pthread_create(&tw->ticker, NULL, movement, (void *) tw)) {
                 tw_set_state(tw, TW_DESTROY);
-                pthread_join(tw->worker, NULL);
-                pthread_cond_destroy(&tw->work);
-                pthread_mutex_destroy(&tw->s_lock);
-                pthread_mutex_destroy(&tw->lock);
-                free(tw->wheel);
-                free(tw);
-                return NULL;
+                goto fail_ticker_create;
         }
 
         return tw;
+
+ fail_ticker_create:
+         pthread_join(tw->worker, NULL);
+ fail_worker_create:
+         pthread_cond_destroy(&tw->work);
+ fail_cond_init:
+         pthread_mutex_destroy(&tw->s_lock);
+ fail_s_lock_init:
+         pthread_mutex_destroy(&tw->lock);
+ fail_lock_init:
+         free(tw->wheel);
+ fail_wheel_malloc:
+         free(tw);
+         return NULL;
 }
 
 void timerwheel_destroy(struct timerwheel * tw)
@@ -318,8 +299,6 @@ void timerwheel_destroy(struct timerwheel * tw)
         list_for_each_safe(p, h, &tw->wq) {
                 struct tw_f * f = list_entry(p, struct tw_f, next);
                 list_del(&f->next);
-                if (f->arg != NULL)
-                        free(f->arg);
                 free(f);
         }
 
@@ -333,30 +312,43 @@ void timerwheel_destroy(struct timerwheel * tw)
         free(tw);
 }
 
-int timerwheel_add(struct timerwheel * tw,
-                   void (* func)(void *),
-                   void * arg,
-                   size_t arg_len,
-                   unsigned int delay)
+struct tw_f * timerwheel_start(struct timerwheel * tw,
+                               void (* func)(void *),
+                               void *              arg,
+                               time_t              delay)
 {
         int pos;
         struct tw_f * f = malloc(sizeof(*f));
         if (f == NULL)
-                return -ENOMEM;
+                return NULL;
 
         f->func = func;
-        f->arg = malloc(arg_len);
-        if (f->arg == NULL) {
-                free(f);
-                return -ENOMEM;
-        }
+        f->arg = arg;
+
+        assert(delay < tw->elements * tw->resolution);
 
-        memcpy(f->arg, arg, arg_len);
+        pthread_mutex_lock(&tw->lock);
+
+        pos = (tw->pos + delay / tw->resolution) & (tw->elements - 1);
+        list_add(&f->next, &tw->wheel[pos].funcs);
+
+        pthread_mutex_unlock(&tw->lock);
+
+        return f;
+}
+
+int timerwheel_restart(struct timerwheel * tw,
+                       struct tw_f *       f,
+                       time_t              delay)
+{
+        int pos;
 
+        assert(tw);
         assert(delay < tw->elements * tw->resolution);
 
         pthread_mutex_lock(&tw->lock);
 
+        list_del(&f->next);
         pos = (tw->pos + delay / tw->resolution) & (tw->elements - 1);
         list_add(&f->next, &tw->wheel[pos].funcs);
 
@@ -364,3 +356,16 @@ int timerwheel_add(struct timerwheel * tw,
 
         return 0;
 }
+
+void timerwheel_stop(struct timerwheel * tw,
+                     struct tw_f *       f)
+{
+        assert(tw);
+
+        pthread_mutex_lock(&tw->lock);
+
+        list_del(&f->next);
+        free(f);
+
+        pthread_mutex_unlock(&tw->lock);
+}