lib: Refactor shm_du_map to shm_rdrbuff

The shm_du_map is renamed to shm_rdrbuff to reflect the Random
Deletion Ringbuffer used in the implementation. The close_on_exit call
is removed and SDUs are cleaned up by the application in the ap_fini()
call. This required a non-blocking peek() operation in the shm_ap_rbuff.

Some initial implementation for future support of qos cubes has been
added to the shm_rdrbuff.

16 files changed, 1042 insertions, 943 deletions

diff --git a/include/ouroboros/config.h.in b/include/ouroboros/config.h.in
index 3a246235..143ae7c8 100644
--- a/include/ouroboros/config.h.in
+++ b/include/ouroboros/config.h.in
@@ -36,9 +36,9 @@
 #define IPCP_NORMAL_EXEC       "@IPCP_NORMAL_TARGET@"
 #define IPCP_LOCAL_EXEC        "@IPCP_LOCAL_TARGET@"
 #define AP_MAX_FLOWS           256
-#define SHM_DU_BUFF_BLOCK_SIZE sysconf(_SC_PAGESIZE)
-#define SHM_DU_MAP_MULTI_BLOCK
-#define SHM_DU_MAP_FILENAME    "/ouroboros.shm"
+#define SHM_RDRB_BLOCK_SIZE    sysconf(_SC_PAGESIZE)
+#define SHM_RDRB_MULTI_BLOCK
+#define SHM_RDRB_PREFIX        "/ouroboros.rdrb."
 #define LOCKFILE_NAME          "/ouroboros.lockfile"
 #define SHM_BUFFER_SIZE        (1 << 14)
 #define DU_BUFF_HEADSPACE      128
diff --git a/include/ouroboros/shared.h b/include/ouroboros/shared.h
index 9ee9df21..bfd99eb0 100644
--- a/include/ouroboros/shared.h
+++ b/include/ouroboros/shared.h
@@ -26,7 +26,8 @@
 /* FIXME: To be decided which QoS cubes we support */
 enum qos_cube {
         QOS_CUBE_BE = 0,
-        QOS_CUBE_VIDEO
+        QOS_CUBE_VIDEO,
+        QOS_MAX
 };
 
 enum flow_state {
diff --git a/include/ouroboros/shm_ap_rbuff.h b/include/ouroboros/shm_ap_rbuff.h
index a1949122..9dad0863 100644
--- a/include/ouroboros/shm_ap_rbuff.h
+++ b/include/ouroboros/shm_ap_rbuff.h
@@ -42,8 +42,9 @@ void                  shm_ap_rbuff_destroy(struct shm_ap_rbuff * rb);
 int                   shm_ap_rbuff_write(struct shm_ap_rbuff * rb,
                                          struct rb_entry * e);
 struct rb_entry *     shm_ap_rbuff_read(struct shm_ap_rbuff * rb);
-int                   shm_ap_rbuff_peek(struct shm_ap_rbuff * rb,
-                                        const struct timespec * timeout);
+int                   shm_ap_rbuff_peek_idx(struct shm_ap_rbuff * rb);
+int                   shm_ap_rbuff_peek_b(struct shm_ap_rbuff * rb,
+                                          const struct timespec * timeout);
 ssize_t               shm_ap_rbuff_read_port(struct shm_ap_rbuff * rb,
                                              int port_id);
 ssize_t               shm_ap_rbuff_read_port_b(struct shm_ap_rbuff * rb,
diff --git a/include/ouroboros/shm_du_map.h b/include/ouroboros/shm_du_map.h
deleted file mode 100644
index 98013fc9..00000000
--- a/include/ouroboros/shm_du_map.h
+++ /dev/null
@@ -1,72 +0,0 @@
-/*
- * Ouroboros - Copyright (C) 2016
- *
- * Shared memory map for data units
- *
- *    Dimitri Staessens <[email protected]>
- *    Sander Vrijders   <[email protected]>
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * 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., 675 Mass Ave, Cambridge, MA 02139, USA.
- */
-
-#ifndef OUROBOROS_SHM_DU_MAP_H
-#define OUROBOROS_SHM_DU_MAP_H
-
-#include <stdint.h>
-#include <pthread.h>
-#include <sys/types.h>
-
-struct shm_du_buff;
-struct shm_du_map;
-
-struct shm_du_map * shm_du_map_create();
-struct shm_du_map * shm_du_map_open();
-void                shm_du_map_close(struct shm_du_map * dum);
-void                shm_du_map_close_on_exit(struct shm_du_map * dum);
-void                shm_du_map_destroy(struct shm_du_map * dum);
-void *              shm_du_map_sanitize(void * o);
-
-/* returns the index of the buffer in the DU map */
-ssize_t   shm_du_map_write(struct shm_du_map * dum,
-                           pid_t               dst_api,
-                           size_t              headspace,
-                           size_t              tailspace,
-                           uint8_t *           data,
-                           size_t              data_len);
-ssize_t   shm_du_map_write_b(struct shm_du_map * dum,
-                             pid_t               dst_api,
-                             size_t              headspace,
-                             size_t              tailspace,
-                             uint8_t *           data,
-                             size_t              data_len);
-int       shm_du_map_read(uint8_t **          dst,
-                          struct shm_du_map * dum,
-                          ssize_t             idx);
-int       shm_du_map_remove(struct shm_du_map  * dum,
-                            ssize_t              idx);
-
-uint8_t * shm_du_buff_head_alloc(struct shm_du_map * dum,
-                                 int                 idx,
-                                 ssize_t             size);
-uint8_t * shm_du_buff_tail_alloc(struct shm_du_map * dum,
-                                 int                 idx,
-                                 ssize_t             size);
-int       shm_du_buff_head_release(struct shm_du_map * dum,
-                                   int                 idx,
-                                   ssize_t             size);
-int       shm_du_buff_tail_release(struct shm_du_map * dum,
-                                   int                 idx,
-                                   ssize_t             size);
-#endif /* OUROBOROS_SHM_DU_MAP_H */
diff --git a/include/ouroboros/shm_rdrbuff.h b/include/ouroboros/shm_rdrbuff.h
new file mode 100644
index 00000000..09256c56
--- /dev/null
+++ b/include/ouroboros/shm_rdrbuff.h
@@ -0,0 +1,84 @@
+/*
+ * Ouroboros - Copyright (C) 2016
+ *
+ * Random Deletion Ring Buffer for Data Units
+ *
+ *    Dimitri Staessens <[email protected]>
+ *    Sander Vrijders   <[email protected]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * 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., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#ifndef OUROBOROS_SHM_RDRBUFF_H
+#define OUROBOROS_SHM_RDRBUFF_H
+
+#include <ouroboros/shared.h>
+
+#include <stdint.h>
+#include <pthread.h>
+#include <sys/types.h>
+
+struct shm_du_buff;
+struct shm_rdrbuff;
+
+struct shm_rdrbuff * shm_rdrbuff_create();
+
+struct shm_rdrbuff * shm_rdrbuff_open();
+
+void                 shm_rdrbuff_close(struct shm_rdrbuff * rdrb);
+
+void                 shm_rdrbuff_destroy(struct shm_rdrbuff * rdrb);
+
+void *               shm_rdrbuff_sanitize(void * o);
+
+/* returns the index of the buffer in the DU map */
+ssize_t   shm_rdrbuff_write(struct shm_rdrbuff * rdrb,
+                            pid_t                dst_api,
+                            size_t               headspace,
+                            size_t               tailspace,
+                            uint8_t *            data,
+                            size_t               data_len);
+
+ssize_t   shm_rdrbuff_write_b(struct shm_rdrbuff * rdrb,
+                              pid_t                dst_api,
+                              size_t               headspace,
+                              size_t               tailspace,
+                              uint8_t *            data,
+                              size_t               data_len);
+
+int       shm_rdrbuff_read(uint8_t **           dst,
+                           struct shm_rdrbuff * rdrb,
+                           ssize_t              idx);
+
+int       shm_rdrbuff_remove(struct shm_rdrbuff  * rdrb,
+                             ssize_t               idx);
+
+
+uint8_t * shm_du_buff_head_alloc(struct shm_rdrbuff * rdrb,
+                                 int                  idx,
+                                 ssize_t              size);
+
+uint8_t * shm_du_buff_tail_alloc(struct shm_rdrbuff * rdrb,
+                                 int                  idx,
+                                 ssize_t              size);
+
+int       shm_du_buff_head_release(struct shm_rdrbuff * rdrb,
+                                   int                  idx,
+                                   ssize_t              size);
+
+int       shm_du_buff_tail_release(struct shm_rdrbuff * rdrb,
+                                   int                  idx,
+                                   ssize_t              size);
+#endif /* OUROBOROS_SHM_RDRBUFF_H */
diff --git a/src/ipcpd/ipcp-data.c b/src/ipcpd/ipcp-data.c
index 593baeba..c4838d3a 100644
--- a/src/ipcpd/ipcp-data.c
+++ b/src/ipcpd/ipcp-data.c
@@ -22,7 +22,6 @@
  */
 
 #include <ouroboros/config.h>
-#include <ouroboros/shm_du_map.h>
 #include <ouroboros/list.h>
 
 #define OUROBOROS_PREFIX "ipcp-utils"
diff --git a/src/ipcpd/local/main.c b/src/ipcpd/local/main.c
index 547e7e28..4fa7e33f 100644
--- a/src/ipcpd/local/main.c
+++ b/src/ipcpd/local/main.c
@@ -24,7 +24,7 @@
 #include "ipcp.h"
 #include "flow.h"
 #include <ouroboros/errno.h>
-#include <ouroboros/shm_du_map.h>
+#include <ouroboros/shm_rdrbuff.h>
 #include <ouroboros/shm_ap_rbuff.h>
 #include <ouroboros/list.h>
 #include <ouroboros/utils.h>
@@ -67,7 +67,7 @@ struct ipcp * _ipcp;
 /* the shim needs access to these internals */
 struct shim_ap_data {
         pid_t                 api;
-        struct shm_du_map *   dum;
+        struct shm_rdrbuff *  rdrb;
         struct bmp *          fds;
         struct shm_ap_rbuff * rb;
 
@@ -98,8 +98,8 @@ static int shim_ap_init()
                 return -1;
         }
 
-        _ap_instance->dum = shm_du_map_open();
-        if (_ap_instance->dum == NULL) {
+        _ap_instance->rdrb = shm_rdrbuff_open();
+        if (_ap_instance->rdrb == NULL) {
                 bmp_destroy(_ap_instance->fds);
                 free(_ap_instance);
                 return -1;
@@ -107,7 +107,7 @@ static int shim_ap_init()
 
         _ap_instance->rb = shm_ap_rbuff_create();
         if (_ap_instance->rb == NULL) {
-                shm_du_map_close(_ap_instance->dum);
+                shm_rdrbuff_close(_ap_instance->rdrb);
                 bmp_destroy(_ap_instance->fds);
                 free(_ap_instance);
                 return -1;
@@ -139,8 +139,13 @@ void shim_ap_fini()
 
         if (_ap_instance->fds != NULL)
                 bmp_destroy(_ap_instance->fds);
-        if (_ap_instance->dum != NULL)
-                shm_du_map_close_on_exit(_ap_instance->dum);
+
+        /* remove all remaining sdus */
+        while ((i = shm_ap_rbuff_peek_idx(_ap_instance->rb)) >= 0)
+                shm_rdrbuff_remove(_ap_instance->rdrb, i);
+
+        if (_ap_instance->rdrb != NULL)
+                shm_rdrbuff_close(_ap_instance->rdrb);
         if (_ap_instance->rb != NULL)
                 shm_ap_rbuff_destroy(_ap_instance->rb);
 
diff --git a/src/ipcpd/normal/main.c b/src/ipcpd/normal/main.c
index 335330ae..cf4ae3f1 100644
--- a/src/ipcpd/normal/main.c
+++ b/src/ipcpd/normal/main.c
@@ -24,7 +24,7 @@
 
 #include <ouroboros/config.h>
 #include <ouroboros/logs.h>
-#include <ouroboros/shm_du_map.h>
+#include <ouroboros/shm_rdrbuff.h>
 #include <ouroboros/shm_ap_rbuff.h>
 #include <ouroboros/dev.h>
 #include <ouroboros/ipcp.h>
@@ -55,7 +55,7 @@ struct normal_ipcp_data {
         /* Keep ipcp_data first for polymorphism. */
         struct ipcp_data      ipcp_data;
 
-        struct shm_du_map *   dum;
+        struct shm_rdrbuff *  rdrb;
         struct shm_ap_rbuff * rb;
 
         pthread_t             mainloop;
@@ -206,15 +206,15 @@ struct normal_ipcp_data * normal_ipcp_data_create()
                 return NULL;
         }
 
-        normal_data->dum = shm_du_map_open();
-        if (normal_data->dum == NULL) {
+        normal_data->rdrb = shm_rdrbuff_open();
+        if (normal_data->rdrb == NULL) {
                 free(normal_data);
                 return NULL;
         }
 
         normal_data->rb = shm_ap_rbuff_open(getpid());
         if (normal_data->rb == NULL) {
-                shm_du_map_close(normal_data->dum);
+                shm_rdrbuff_close(normal_data->rdrb);
                 free(normal_data);
                 return NULL;
         }
@@ -225,6 +225,8 @@ struct normal_ipcp_data * normal_ipcp_data_create()
 
 void normal_ipcp_data_destroy()
 {
+        int idx = 0;
+
         if (_ipcp == NULL)
                 return;
 
@@ -233,8 +235,12 @@ void normal_ipcp_data_destroy()
         if (ipcp_get_state(_ipcp) != IPCP_SHUTDOWN)
                 LOG_WARN("Cleaning up while not in shutdown.");
 
-        if (normal_data(_ipcp)->dum != NULL)
-                shm_du_map_close_on_exit(normal_data(_ipcp)->dum);
+        /* remove all remaining sdus */
+        while ((idx = shm_ap_rbuff_peek_idx(normal_data(_ipcp)->rb)) >= 0)
+                shm_rdrbuff_remove(normal_data(_ipcp)->rdrb, idx);
+
+        if (normal_data(_ipcp)->rdrb != NULL)
+                shm_rdrbuff_close(normal_data(_ipcp)->rdrb);
         if (normal_data(_ipcp)->rb != NULL)
                 shm_ap_rbuff_close(normal_data(_ipcp)->rb);
 
diff --git a/src/ipcpd/shim-eth-llc/main.c b/src/ipcpd/shim-eth-llc/main.c
index 608b0029..d1100001 100644
--- a/src/ipcpd/shim-eth-llc/main.c
+++ b/src/ipcpd/shim-eth-llc/main.c
@@ -27,7 +27,7 @@
 #include "ipcp.h"
 #include "flow.h"
 #include <ouroboros/errno.h>
-#include <ouroboros/shm_du_map.h>
+#include <ouroboros/shm_rdrbuff.h>
 #include <ouroboros/shm_ap_rbuff.h>
 #include <ouroboros/list.h>
 #include <ouroboros/utils.h>
@@ -122,7 +122,7 @@ struct eth_llc_ipcp_data {
         struct bmp *          indices;
         struct bmp *          saps;
 
-        struct shm_du_map *   dum;
+        struct shm_rdrbuff *  rdrb;
         struct shm_ap_rbuff * rb;
 
         uint8_t *             rx_ring;
@@ -155,15 +155,15 @@ struct eth_llc_ipcp_data * eth_llc_ipcp_data_create()
                 return NULL;
         }
 
-        eth_llc_data->dum = shm_du_map_open();
-        if (eth_llc_data->dum == NULL) {
+        eth_llc_data->rdrb = shm_rdrbuff_open();
+        if (eth_llc_data->rdrb == NULL) {
                 free(eth_llc_data);
                 return NULL;
         }
 
         eth_llc_data->rb = shm_ap_rbuff_create();
         if (eth_llc_data->rb == NULL) {
-                shm_du_map_close(eth_llc_data->dum);
+                shm_rdrbuff_close(eth_llc_data->rdrb);
                 free(eth_llc_data);
                 return NULL;
         }
@@ -171,7 +171,7 @@ struct eth_llc_ipcp_data * eth_llc_ipcp_data_create()
         eth_llc_data->indices = bmp_create(AP_MAX_FLOWS, 0);
         if (eth_llc_data->indices == NULL) {
                 shm_ap_rbuff_destroy(eth_llc_data->rb);
-                shm_du_map_close(eth_llc_data->dum);
+                shm_rdrbuff_close(eth_llc_data->rdrb);
                 free(eth_llc_data);
                 return NULL;
         }
@@ -180,7 +180,7 @@ struct eth_llc_ipcp_data * eth_llc_ipcp_data_create()
         if (eth_llc_data->indices == NULL) {
                 bmp_destroy(eth_llc_data->indices);
                 shm_ap_rbuff_destroy(eth_llc_data->rb);
-                shm_du_map_close(eth_llc_data->dum);
+                shm_rdrbuff_close(eth_llc_data->rdrb);
                 free(eth_llc_data);
                 return NULL;
         }
@@ -202,8 +202,12 @@ void eth_llc_ipcp_data_destroy()
         if (ipcp_get_state(_ipcp) != IPCP_SHUTDOWN)
                 LOG_WARN("Cleaning up while not in shutdown.");
 
-        if (shim_data(_ipcp)->dum != NULL)
-                shm_du_map_close_on_exit(shim_data(_ipcp)->dum);
+        /* remove all remaining sdus */
+        while ((i = shm_ap_rbuff_peek_idx(shim_data(_ipcp)->rb)) >= 0)
+                shm_rdrbuff_remove(shim_data(_ipcp)->rdrb, i);
+
+        if (shim_data(_ipcp)->rdrb != NULL)
+                shm_rdrbuff_close(shim_data(_ipcp)->rdrb);
         if (shim_data(_ipcp)->rb != NULL)
                 shm_ap_rbuff_destroy(shim_data(_ipcp)->rb);
         if (shim_data(_ipcp)->indices != NULL)
@@ -332,7 +336,7 @@ static int eth_llc_ipcp_send_frame(uint8_t   dst_addr[MAC_SIZE],
 
 #if defined(PACKET_RX_RING) && defined(PACKET_TX_RING)
         header = (void *) shim_data(_ipcp)->tx_ring +
-                (shim_data(_ipcp)->tx_offset * SHM_DU_BUFF_BLOCK_SIZE);
+                (shim_data(_ipcp)->tx_offset * SHM_RDRB_BLOCK_SIZE);
 
         while (header->tp_status != TP_STATUS_AVAILABLE) {
                 pfd.fd = fd;
@@ -345,7 +349,7 @@ static int eth_llc_ipcp_send_frame(uint8_t   dst_addr[MAC_SIZE],
                 }
 
                 header = (void *) shim_data(_ipcp)->tx_ring +
-                        (shim_data(_ipcp)->tx_offset * SHM_DU_BUFF_BLOCK_SIZE);
+                        (shim_data(_ipcp)->tx_offset * SHM_RDRB_BLOCK_SIZE);
         }
 
         frame = (void *) header + TPACKET_HDRLEN - sizeof(struct sockaddr_ll);
@@ -671,7 +675,7 @@ static void * eth_llc_ipcp_sdu_reader(void * o)
         while (true) {
 #if defined(PACKET_RX_RING) && defined(PACKET_TX_RING)
                 header = (void *) shim_data(_ipcp)->rx_ring +
-                        (offset * SHM_DU_BUFF_BLOCK_SIZE);
+                        (offset * SHM_RDRB_BLOCK_SIZE);
                 while (!(header->tp_status & TP_STATUS_USER)) {
                         pfd.fd = shim_data(_ipcp)->s_fd;
                         pfd.revents = 0;
@@ -683,7 +687,7 @@ static void * eth_llc_ipcp_sdu_reader(void * o)
                         }
 
                         header = (void *) shim_data(_ipcp)->rx_ring +
-                                (offset * SHM_DU_BUFF_BLOCK_SIZE);
+                                (offset * SHM_RDRB_BLOCK_SIZE);
                 }
 
                 buf = (void * ) header + header->tp_mac;
@@ -740,7 +744,7 @@ static void * eth_llc_ipcp_sdu_reader(void * o)
                         }
 
                         while ((index =
-                                shm_du_map_write(shim_data(_ipcp)->dum,
+                                shm_rdrbuff_write(shim_data(_ipcp)->rdrb,
                                                  ipcp_flow(i)->api,
                                                  0,
                                                  0,
@@ -782,8 +786,8 @@ static void * eth_llc_ipcp_sdu_writer(void * o)
 
                 pthread_rwlock_rdlock(&_ipcp->state_lock);
 
-                len = shm_du_map_read((uint8_t **) &buf,
-                                      shim_data(_ipcp)->dum,
+                len = shm_rdrbuff_read((uint8_t **) &buf,
+                                      shim_data(_ipcp)->rdrb,
                                       e->index);
                 if (len <= 0) {
                         free(e);
@@ -808,8 +812,8 @@ static void * eth_llc_ipcp_sdu_writer(void * o)
 
                 pthread_rwlock_unlock(&shim_data(_ipcp)->flows_lock);
 
-                if (shim_data(_ipcp)->dum != NULL)
-                        shm_du_map_remove(shim_data(_ipcp)->dum, e->index);
+                if (shim_data(_ipcp)->rdrb != NULL)
+                        shm_rdrbuff_remove(shim_data(_ipcp)->rdrb, e->index);
 
                 pthread_rwlock_unlock(&_ipcp->state_lock);
 
@@ -849,7 +853,7 @@ static int eth_llc_ipcp_bootstrap(struct dif_config * conf)
 {
         int fd = -1;
         struct ifreq ifr;
-        int index;
+        int idx;
 #ifdef __FreeBSD__
         struct ifaddrs * ifaddr;
         struct ifaddrs * ifa;
@@ -892,7 +896,7 @@ static int eth_llc_ipcp_bootstrap(struct dif_config * conf)
                 return -1;
         }
 
-        for (ifa = ifaddr, index = 0; ifa != NULL; ifa = ifa->ifa_next, ++index) {
+        for (ifa = ifaddr, idx = 0; ifa != NULL; ifa = ifa->ifa_next, ++idx) {
                 if (strcmp(ifa->ifa_name, conf->if_name))
                         continue;
                 LOG_DBGF("Interface %s found.", conf->if_name);
@@ -916,8 +920,8 @@ static int eth_llc_ipcp_bootstrap(struct dif_config * conf)
                 return -1;
         }
 
-        index = if_nametoindex(conf->if_name);
-        if (index == 0) {
+        idx = if_nametoindex(conf->if_name);
+        if (idx == 0) {
                 LOG_ERR("Failed to retrieve interface index.");
                 return -1;
         }
@@ -927,7 +931,7 @@ static int eth_llc_ipcp_bootstrap(struct dif_config * conf)
 
         memset(&(device), 0, sizeof(device));
 #ifdef __FreeBSD__
-        device.sdl_index = index;
+        device.sdl_index = idx;
         device.sdl_family = AF_LINK;
         memcpy(LLADDR(&device),
                ifr.ifr_addr.sa_data,
@@ -937,7 +941,7 @@ static int eth_llc_ipcp_bootstrap(struct dif_config * conf)
         LOG_MISSING;
         fd = socket(AF_LINK, SOCK_RAW, 0);
 #else
-        device.sll_ifindex = index;
+        device.sll_ifindex = idx;
         device.sll_family = AF_PACKET;
         memcpy(device.sll_addr,
                ifr.ifr_hwaddr.sa_data,
@@ -953,14 +957,14 @@ static int eth_llc_ipcp_bootstrap(struct dif_config * conf)
         }
 
 #if defined(PACKET_RX_RING) && defined(PACKET_TX_RING)
-        if (SHIM_ETH_LLC_MAX_SDU_SIZE > SHM_DU_BUFF_BLOCK_SIZE) {
+        if (SHIM_ETH_LLC_MAX_SDU_SIZE > SHM_RDRB_BLOCK_SIZE) {
                 LOG_ERR("Max SDU size is bigger than DU map block size.");
                 close(fd);
                 return -1;
         }
 
-        req.tp_block_size = SHM_DU_BUFF_BLOCK_SIZE;
-        req.tp_frame_size = SHM_DU_BUFF_BLOCK_SIZE;
+        req.tp_block_size = SHM_RDRB_BLOCK_SIZE;
+        req.tp_frame_size = SHM_RDRB_BLOCK_SIZE;
         req.tp_block_nr = SHM_BUFFER_SIZE;
         req.tp_frame_nr = SHM_BUFFER_SIZE;
 
@@ -987,7 +991,7 @@ static int eth_llc_ipcp_bootstrap(struct dif_config * conf)
 
 #if defined(PACKET_RX_RING) && defined(PACKET_TX_RING)
         shim_data(_ipcp)->rx_ring = mmap(NULL,
-                                         2 * SHM_DU_BUFF_BLOCK_SIZE
+                                         2 * SHM_RDRB_BLOCK_SIZE
                                          * SHM_BUFFER_SIZE,
                                          PROT_READ | PROT_WRITE, MAP_SHARED,
                                          fd, 0);
@@ -997,10 +1001,9 @@ static int eth_llc_ipcp_bootstrap(struct dif_config * conf)
                 return -1;
         }
         shim_data(_ipcp)->tx_ring = shim_data(_ipcp)->rx_ring
-                + (SHM_DU_BUFF_BLOCK_SIZE * SHM_BUFFER_SIZE);
+                + (SHM_RDRB_BLOCK_SIZE * SHM_BUFFER_SIZE);
 
 #endif
-
         pthread_rwlock_wrlock(&_ipcp->state_lock);
 
         if (ipcp_get_state(_ipcp) != IPCP_INIT) {
diff --git a/src/ipcpd/shim-udp/main.c b/src/ipcpd/shim-udp/main.c
index 3f9b20f1..451a2a4c 100644
--- a/src/ipcpd/shim-udp/main.c
+++ b/src/ipcpd/shim-udp/main.c
@@ -24,7 +24,7 @@
 #include "ipcp.h"
 #include "flow.h"
 #include "shim_udp_config.h"
-#include <ouroboros/shm_du_map.h>
+#include <ouroboros/shm_rdrbuff.h>
 #include <ouroboros/shm_ap_rbuff.h>
 #include <ouroboros/list.h>
 #include <ouroboros/utils.h>
@@ -87,7 +87,7 @@ struct ipcp * _ipcp;
 /* the shim needs access to these internals */
 struct shim_ap_data {
         pid_t                 api;
-        struct shm_du_map *   dum;
+        struct shm_rdrbuff *  rdrb;
         struct bmp *          fds;
         struct shm_ap_rbuff * rb;
 
@@ -121,8 +121,8 @@ static int shim_ap_init()
                 return -1;
         }
 
-        _ap_instance->dum = shm_du_map_open();
-        if (_ap_instance->dum == NULL) {
+        _ap_instance->rdrb = shm_rdrbuff_open();
+        if (_ap_instance->rdrb == NULL) {
                 bmp_destroy(_ap_instance->fds);
                 free(_ap_instance);
                 return -1;
@@ -130,7 +130,7 @@ static int shim_ap_init()
 
         _ap_instance->rb = shm_ap_rbuff_create();
         if (_ap_instance->rb == NULL) {
-                shm_du_map_close(_ap_instance->dum);
+                shm_rdrbuff_close(_ap_instance->rdrb);
                 bmp_destroy(_ap_instance->fds);
                 free(_ap_instance);
                 return -1;
@@ -163,8 +163,13 @@ void shim_ap_fini()
 
         if (_ap_instance->fds != NULL)
                 bmp_destroy(_ap_instance->fds);
-        if (_ap_instance->dum != NULL)
-                shm_du_map_close_on_exit(_ap_instance->dum);
+
+        /* remove all remaining sdus */
+        while ((i = shm_ap_rbuff_peek_idx(_ap_instance->rb)) >= 0)
+                shm_rdrbuff_remove(_ap_instance->rdrb, i);
+
+        if (_ap_instance->rdrb != NULL)
+                shm_rdrbuff_close(_ap_instance->rdrb);
         if (_ap_instance->rb != NULL)
                 shm_ap_rbuff_destroy(_ap_instance->rb);
 
@@ -202,7 +207,7 @@ static ssize_t ipcp_udp_flow_write(int fd, void * buf, size_t count)
         pthread_rwlock_rdlock(&_ipcp->state_lock);
         pthread_rwlock_rdlock(&_ap_instance->flows_lock);
 
-        index = shm_du_map_write_b(_ap_instance->dum,
+        index = shm_rdrbuff_write_b(_ap_instance->rdrb,
                                    _ap_instance->flows[fd].api,
                                    0,
                                    0,
@@ -745,8 +750,8 @@ static void * ipcp_udp_sdu_loop(void * o)
 
                 pthread_rwlock_rdlock(&_ipcp->state_lock);
 
-                len = shm_du_map_read((uint8_t **) &buf,
-                                      _ap_instance->dum,
+                len = shm_rdrbuff_read((uint8_t **) &buf,
+                                      _ap_instance->rdrb,
                                       e->index);
                 if (len <= 0) {
                         pthread_rwlock_unlock(&_ipcp->state_lock);
@@ -771,8 +776,8 @@ static void * ipcp_udp_sdu_loop(void * o)
 
                 pthread_rwlock_rdlock(&_ipcp->state_lock);
 
-                if (_ap_instance->dum != NULL)
-                        shm_du_map_remove(_ap_instance->dum, e->index);
+                if (_ap_instance->rdrb != NULL)
+                        shm_rdrbuff_remove(_ap_instance->rdrb, e->index);
 
                 pthread_rwlock_unlock(&_ipcp->state_lock);
 
diff --git a/src/irmd/main.c b/src/irmd/main.c
index cd939360..29f6d9d0 100644
--- a/src/irmd/main.c
+++ b/src/irmd/main.c
@@ -34,7 +34,7 @@
 #include <ouroboros/irm_config.h>
 #include <ouroboros/lockfile.h>
 #include <ouroboros/shm_ap_rbuff.h>
-#include <ouroboros/shm_du_map.h>
+#include <ouroboros/shm_rdrbuff.h>
 #include <ouroboros/bitmap.h>
 #include <ouroboros/flow.h>
 #include <ouroboros/qos.h>
@@ -75,31 +75,31 @@ enum irm_state {
 };
 
 struct irm {
-        struct list_head    registry;
+        struct list_head     registry;
 
-        struct list_head    ipcps;
+        struct list_head     ipcps;
 
-        struct list_head    api_table;
-        struct list_head    apn_table;
-        struct list_head    spawned_apis;
-        pthread_rwlock_t    reg_lock;
+        struct list_head     api_table;
+        struct list_head     apn_table;
+        struct list_head     spawned_apis;
+        pthread_rwlock_t     reg_lock;
 
         /* keep track of all flows in this processing system */
-        struct bmp *        port_ids;
+        struct bmp *         port_ids;
         /* maps port_ids to api pair */
-        struct list_head    irm_flows;
-        pthread_rwlock_t    flows_lock;
+        struct list_head     irm_flows;
+        pthread_rwlock_t     flows_lock;
 
-        struct lockfile *   lf;
-        struct shm_du_map * dum;
-        pthread_t *         threadpool;
-        int                 sockfd;
+        struct lockfile *    lf;
+        struct shm_rdrbuff * rdrb;
+        pthread_t *          threadpool;
+        int                  sockfd;
 
-        enum irm_state      state;
-        pthread_rwlock_t    state_lock;
+        enum irm_state       state;
+        pthread_rwlock_t     state_lock;
 
-        pthread_t           irm_sanitize;
-        pthread_t           shm_sanitize;
+        pthread_t            irm_sanitize;
+        pthread_t            shm_sanitize;
 } * irmd = NULL;
 
 static struct irm_flow * get_irm_flow(int port_id)
@@ -1604,8 +1604,8 @@ static void irm_destroy()
 
         pthread_rwlock_unlock(&irmd->flows_lock);
 
-        if (irmd->dum != NULL)
-                shm_du_map_destroy(irmd->dum);
+        if (irmd->rdrb != NULL)
+                shm_rdrbuff_destroy(irmd->rdrb);
 
         if (irmd->lf != NULL)
                 lockfile_destroy(irmd->lf);
@@ -2072,7 +2072,8 @@ static int irm_create()
 
                 if (kill(lockfile_owner(irmd->lf), 0) < 0) {
                         LOG_INFO("IRMd didn't properly shut down last time.");
-                        shm_du_map_destroy(shm_du_map_open());
+                        /* FIXME: do this for each QOS_CUBE in the system */
+                        shm_rdrbuff_destroy(shm_rdrbuff_open(QOS_CUBE_BE));
                         LOG_INFO("Stale resources cleaned");
                         lockfile_destroy(irmd->lf);
                         irmd->lf = lockfile_create();
@@ -2090,7 +2091,8 @@ static int irm_create()
                 return -1;
         }
 
-        if ((irmd->dum = shm_du_map_create()) == NULL) {
+        /* FIXME: create an rdrb for each QOS_CUBE in the system */
+        if ((irmd->rdrb = shm_rdrbuff_create(QOS_CUBE_BE)) == NULL) {
                 irm_destroy();
                 return -1;
         }
@@ -2201,7 +2203,7 @@ int main(int argc, char ** argv)
 
         pthread_create(&irmd->irm_sanitize, NULL, irm_sanitize, NULL);
         pthread_create(&irmd->shm_sanitize, NULL,
-                       shm_du_map_sanitize, irmd->dum);
+                       shm_rdrbuff_sanitize, irmd->rdrb);
 
         /* wait for (all of them) to return */
         for (t = 0; t < IRMD_THREADPOOL_SIZE; ++t)
diff --git a/src/lib/CMakeLists.txt b/src/lib/CMakeLists.txt
index 5e16c7e2..8c058dd8 100644
--- a/src/lib/CMakeLists.txt
+++ b/src/lib/CMakeLists.txt
@@ -33,7 +33,7 @@ set(SOURCE_FILES
   logs.c
   nsm.c
   shm_ap_rbuff.c
-  shm_du_map.c
+  shm_rdrbuff.c
   sockets.c
   time_utils.c
   utils.c
diff --git a/src/lib/dev.c b/src/lib/dev.c
index 3a5fc8e0..17c473ed 100644
--- a/src/lib/dev.c
+++ b/src/lib/dev.c
@@ -25,7 +25,7 @@
 #include <ouroboros/dev.h>
 #include <ouroboros/sockets.h>
 #include <ouroboros/bitmap.h>
-#include <ouroboros/shm_du_map.h>
+#include <ouroboros/shm_rdrbuff.h>
 #include <ouroboros/shm_ap_rbuff.h>
 #include <ouroboros/utils.h>
 
@@ -45,7 +45,7 @@ struct flow {
 struct ap_data {
         char *                ap_name;
         pid_t                 api;
-        struct shm_du_map *   dum;
+        struct shm_rdrbuff *  rdrb;
         struct bmp *          fds;
         struct shm_ap_rbuff * rb;
         pthread_rwlock_t      data_lock;
@@ -105,8 +105,8 @@ int ap_init(char * ap_name)
                 return -ENOMEM;
         }
 
-        _ap_instance->dum = shm_du_map_open();
-        if (_ap_instance->dum == NULL) {
+        _ap_instance->rdrb = shm_rdrbuff_open();
+        if (_ap_instance->rdrb == NULL) {
                 bmp_destroy(_ap_instance->fds);
                 free(_ap_instance);
                 return -1;
@@ -114,7 +114,7 @@ int ap_init(char * ap_name)
 
         _ap_instance->rb = shm_ap_rbuff_create();
         if (_ap_instance->rb == NULL) {
-                shm_du_map_close(_ap_instance->dum);
+                shm_rdrbuff_close(_ap_instance->rdrb);
                 bmp_destroy(_ap_instance->fds);
                 free(_ap_instance);
                 return -1;
@@ -146,12 +146,16 @@ void ap_fini(void)
 
         pthread_rwlock_wrlock(&_ap_instance->data_lock);
 
+        /* remove all remaining sdus */
+        while ((i = shm_ap_rbuff_peek_idx(_ap_instance->rb)) >= 0)
+                shm_rdrbuff_remove(_ap_instance->rdrb, i);
+
         if (_ap_instance->fds != NULL)
                 bmp_destroy(_ap_instance->fds);
         if (_ap_instance->rb != NULL)
                 shm_ap_rbuff_destroy(_ap_instance->rb);
-        if (_ap_instance->dum != NULL)
-                shm_du_map_close_on_exit(_ap_instance->dum);
+        if (_ap_instance->rdrb != NULL)
+                shm_rdrbuff_close(_ap_instance->rdrb);
 
         pthread_rwlock_rdlock(&_ap_instance->flows_lock);
 
@@ -515,7 +519,7 @@ ssize_t flow_write(int fd, void * buf, size_t count)
         }
 
         if (_ap_instance->flows[fd].oflags & FLOW_O_NONBLOCK) {
-                idx = shm_du_map_write(_ap_instance->dum,
+                idx = shm_rdrbuff_write(_ap_instance->rdrb,
                                        _ap_instance->flows[fd].api,
                                        DU_BUFF_HEADSPACE,
                                        DU_BUFF_TAILSPACE,
@@ -531,18 +535,18 @@ ssize_t flow_write(int fd, void * buf, size_t count)
                 e.port_id = _ap_instance->flows[fd].port_id;
 
                 if (shm_ap_rbuff_write(_ap_instance->flows[fd].rb, &e) < 0) {
-                        shm_du_map_remove(_ap_instance->dum, idx);
+                        shm_rdrbuff_remove(_ap_instance->rdrb, idx);
                         pthread_rwlock_unlock(&_ap_instance->flows_lock);
                         pthread_rwlock_unlock(&_ap_instance->data_lock);
                         return -1;
                 }
         } else { /* blocking */
-                struct shm_du_map * dum = _ap_instance->dum;
-                pid_t               api = _ap_instance->flows[fd].api;
+                struct shm_rdrbuff * rdrb = _ap_instance->rdrb;
+                pid_t                api = _ap_instance->flows[fd].api;
                 pthread_rwlock_unlock(&_ap_instance->flows_lock);
                 pthread_rwlock_unlock(&_ap_instance->data_lock);
 
-                idx = shm_du_map_write_b(dum,
+                idx = shm_rdrbuff_write_b(rdrb,
                                          api,
                                          DU_BUFF_HEADSPACE,
                                          DU_BUFF_TAILSPACE,
@@ -567,7 +571,7 @@ ssize_t flow_write(int fd, void * buf, size_t count)
 
 int flow_select(const struct timespec * timeout)
 {
-        int port_id = shm_ap_rbuff_peek(_ap_instance->rb, timeout);
+        int port_id = shm_ap_rbuff_peek_b(_ap_instance->rb, timeout);
         if (port_id < 0)
                 return port_id;
         return port_id_to_fd(port_id);
@@ -612,7 +616,7 @@ ssize_t flow_read(int fd, void * buf, size_t count)
                 return -EAGAIN;
         }
 
-        n = shm_du_map_read(&sdu, _ap_instance->dum, idx);
+        n = shm_rdrbuff_read(&sdu, _ap_instance->rdrb, idx);
         if (n < 0) {
                 pthread_rwlock_unlock(&_ap_instance->data_lock);
                 return -1;
@@ -620,7 +624,7 @@ ssize_t flow_read(int fd, void * buf, size_t count)
 
         memcpy(buf, sdu, MIN(n, count));
 
-        shm_du_map_remove(_ap_instance->dum, idx);
+        shm_rdrbuff_remove(_ap_instance->rdrb, idx);
 
         pthread_rwlock_unlock(&_ap_instance->data_lock);
 
diff --git a/src/lib/shm_ap_rbuff.c b/src/lib/shm_ap_rbuff.c
index 4ca29636..f21b1e86 100644
--- a/src/lib/shm_ap_rbuff.c
+++ b/src/lib/shm_ap_rbuff.c
@@ -285,8 +285,32 @@ int shm_ap_rbuff_write(struct shm_ap_rbuff * rb, struct rb_entry * e)
         return 0;
 }
 
-int shm_ap_rbuff_peek(struct shm_ap_rbuff * rb,
-                      const struct timespec * timeout)
+int shm_ap_rbuff_peek_idx(struct shm_ap_rbuff * rb)
+{
+        int ret = 0;
+
+        if (rb == NULL)
+                return -EINVAL;
+
+        if (pthread_mutex_lock(rb->lock) == EOWNERDEAD) {
+                LOG_DBG("Recovering dead mutex.");
+                pthread_mutex_consistent(rb->lock);
+        }
+
+        if (shm_rbuff_empty(rb)) {
+                pthread_mutex_unlock(rb->lock);
+                return -1;
+        }
+
+        ret = (rb->shm_base + *rb->ptr_tail)->index;
+
+        pthread_mutex_unlock(rb->lock);
+
+        return ret;
+}
+
+int shm_ap_rbuff_peek_b(struct shm_ap_rbuff * rb,
+                        const struct timespec * timeout)
 {
         struct timespec abstime;
         int ret = 0;
diff --git a/src/lib/shm_du_map.c b/src/lib/shm_du_map.c
deleted file mode 100644
index 9ca282b9..00000000
--- a/src/lib/shm_du_map.c
+++ /dev/null
@@ -1,767 +0,0 @@
-/*
- * Ouroboros - Copyright (C) 2016
- *
- * Shared memory map for data units
- *
- *    Dimitri Staessens <[email protected]>
- *    Sander Vrijders   <[email protected]>
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * 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., 675 Mass Ave, Cambridge, MA 02139, USA.
- */
-
-#include <ouroboros/config.h>
-#include <ouroboros/errno.h>
-#include <ouroboros/shm_du_map.h>
-#include <ouroboros/shm_ap_rbuff.h>
-#include <ouroboros/time_utils.h>
-
-#include <pthread.h>
-#include <sys/mman.h>
-#include <fcntl.h>
-#include <unistd.h>
-#include <stdlib.h>
-#include <string.h>
-#include <signal.h>
-#include <sys/stat.h>
-
-#define OUROBOROS_PREFIX "shm_du_map"
-
-#include <ouroboros/logs.h>
-
-#define SHM_BLOCKS_SIZE (SHM_BUFFER_SIZE * SHM_DU_BUFF_BLOCK_SIZE)
-#define SHM_FILE_SIZE (SHM_BLOCKS_SIZE + 3 * sizeof (size_t)                   \
-                       + sizeof(pthread_mutex_t) + 2 * sizeof(pthread_cond_t)  \
-                       + sizeof(pid_t))
-
-#define get_head_ptr(dum)                                                      \
-((struct shm_du_buff *)(dum->shm_base + (*dum->ptr_head *                      \
-                                         SHM_DU_BUFF_BLOCK_SIZE)))
-
-#define get_tail_ptr(dum)                                                      \
-((struct shm_du_buff *)(dum->shm_base + (*dum->ptr_tail *                      \
-                                         SHM_DU_BUFF_BLOCK_SIZE)))
-
-#define idx_to_du_buff_ptr(dum, idx)                                           \
-        ((struct shm_du_buff *)(dum->shm_base + (idx * SHM_DU_BUFF_BLOCK_SIZE)))
-
-#define block_ptr_to_idx(dum, sdb)                                             \
-        (((uint8_t *)sdb - dum->shm_base) / SHM_DU_BUFF_BLOCK_SIZE)
-
-#define shm_map_used(dum)((*dum->ptr_head + SHM_BUFFER_SIZE - *dum->ptr_tail)\
-                          & (SHM_BUFFER_SIZE - 1))
-#define shm_map_free(dum, i)(shm_map_used(dum) + i < SHM_BUFFER_SIZE)
-
-#define shm_map_empty(dum) (*dum->ptr_tail == *dum->ptr_head)
-
-struct shm_du_buff {
-        size_t size;
-#ifdef SHM_DU_MAP_MULTI_BLOCK
-        size_t blocks;
-#endif
-        size_t du_head;
-        size_t du_tail;
-        pid_t  dst_api;
-};
-
-struct shm_du_map {
-        uint8_t *         shm_base;    /* start of blocks */
-        size_t *          ptr_head;    /* start of ringbuffer head */
-        size_t *          ptr_tail;    /* start of ringbuffer tail */
-        pthread_mutex_t * lock;   /* lock all free space in shm */
-        size_t *          choked;      /* stale sdu detection */
-        pthread_cond_t *  healthy;     /* du map is healthy */
-        pthread_cond_t *  full;        /* run sanitizer when buffer full */
-        pid_t *           api;         /* api of the irmd owner */
-        int               fd;
-};
-
-static void garbage_collect(struct shm_du_map * dum)
-{
-#ifdef SHM_DU_MAP_MULTI_BLOCK
-        struct shm_du_buff * sdb;
-        while (!shm_map_empty(dum) && (sdb = get_tail_ptr(dum))->dst_api == -1)
-                *dum->ptr_tail = (*dum->ptr_tail + sdb->blocks)
-                        & (SHM_BUFFER_SIZE - 1);
-#else
-        while (!shm_map_empty(dum) && get_tail_ptr(dum)->dst_api == -1)
-                *dum->ptr_tail =
-                        (*dum->ptr_tail + 1) & (SHM_BUFFER_SIZE - 1);
-
-#endif
-}
-
-static void clean_sdus(struct shm_du_map * dum, pid_t api, bool exit)
-{
-        size_t idx = *dum->ptr_tail;
-        struct shm_du_buff * buf;
-
-        while (idx != *dum->ptr_head) {
-                buf = idx_to_du_buff_ptr(dum, idx);
-                if (buf->dst_api == api)
-                        buf->dst_api = -1;
-#ifdef SHM_DU_MAP_MULTI_BLOCK
-                idx = (idx + buf->blocks) & (SHM_BUFFER_SIZE - 1);
-#else
-                idx = (idx + 1) & (SHM_BUFFER_SIZE - 1);
-#endif
-        }
-
-        garbage_collect(dum);
-
-        if (!exit && kill(api, 0) == 0) {
-                struct shm_ap_rbuff * rb;
-                rb = shm_ap_rbuff_open(api);
-                if (rb != NULL) {
-                        shm_ap_rbuff_reset(rb);
-                        shm_ap_rbuff_close(rb);
-                }
-        }
-
-        *dum->choked = 0;
-}
-
-struct shm_du_map * shm_du_map_create()
-{
-        struct shm_du_map * dum;
-        int                 shm_fd;
-        uint8_t *           shm_base;
-        pthread_mutexattr_t mattr;
-        pthread_condattr_t  cattr;
-
-        dum = malloc(sizeof *dum);
-        if (dum == NULL) {
-                LOG_DBGF("Could not allocate struct.");
-                return NULL;
-        }
-
-        shm_fd = shm_open(SHM_DU_MAP_FILENAME, O_CREAT | O_EXCL | O_RDWR, 0666);
-        if (shm_fd == -1) {
-                LOG_DBGF("Failed creating shared memory map.");
-                free(dum);
-                return NULL;
-        }
-
-        if (fchmod(shm_fd, 0666)) {
-                LOG_DBGF("Failed to chmod shared memory map.");
-                free(dum);
-                return NULL;
-        }
-
-        if (ftruncate(shm_fd, SHM_FILE_SIZE - 1) < 0) {
-                LOG_DBGF("Failed to extend shared memory map.");
-                free(dum);
-                return NULL;
-        }
-
-        if (write(shm_fd, "", 1) != 1) {
-                LOG_DBGF("Failed to finalise extension of shared memory map.");
-                free(dum);
-                return NULL;
-        }
-
-        shm_base = mmap(NULL,
-                        SHM_FILE_SIZE,
-                        PROT_READ | PROT_WRITE,
-                        MAP_SHARED,
-                        shm_fd,
-                        0);
-
-        if (shm_base == MAP_FAILED) {
-                LOG_DBGF("Failed to map shared memory.");
-                if (shm_unlink(SHM_DU_MAP_FILENAME) == -1)
-                        LOG_DBGF("Failed to remove invalid shm.");
-
-                free(dum);
-                return NULL;
-        }
-
-        dum->shm_base = shm_base;
-        dum->ptr_head = (size_t *)
-                ((uint8_t *) dum->shm_base + SHM_BLOCKS_SIZE);
-        dum->ptr_tail = dum->ptr_head + 1;
-        dum->lock = (pthread_mutex_t *) (dum->ptr_tail + 1);
-        dum->choked = (size_t *) (dum->lock + 1);
-        dum->healthy = (pthread_cond_t *) (dum->choked + 1);
-        dum->full = dum->healthy + 1;
-        dum->api = (pid_t *) (dum->full + 1);
-
-        pthread_mutexattr_init(&mattr);
-        pthread_mutexattr_setpshared(&mattr, PTHREAD_PROCESS_SHARED);
-        pthread_mutexattr_setrobust(&mattr, PTHREAD_MUTEX_ROBUST);
-        pthread_mutex_init(dum->lock, &mattr);
-
-        pthread_condattr_init(&cattr);
-        pthread_condattr_setpshared(&cattr, PTHREAD_PROCESS_SHARED);
-        pthread_cond_init(dum->full, &cattr);
-        pthread_cond_init(dum->healthy, &cattr);
-
-        *dum->ptr_head = 0;
-        *dum->ptr_tail = 0;
-
-        *dum->choked = 0;
-
-        *dum->api = getpid();
-
-        dum->fd = shm_fd;
-
-        return dum;
-}
-
-struct shm_du_map * shm_du_map_open()
-{
-        struct shm_du_map * dum;
-        int                 shm_fd;
-        uint8_t *           shm_base;
-
-        dum = malloc(sizeof *dum);
-        if (dum == NULL) {
-                LOG_DBGF("Could not allocate struct.");
-                return NULL;
-        }
-
-        shm_fd = shm_open(SHM_DU_MAP_FILENAME, O_RDWR, 0666);
-        if (shm_fd < 0) {
-                LOG_DBGF("Failed opening shared memory.");
-                free(dum);
-                return NULL;
-        }
-
-        shm_base = mmap(NULL,
-                        SHM_FILE_SIZE,
-                        PROT_READ | PROT_WRITE,
-                        MAP_SHARED,
-                        shm_fd,
-                        0);
-        if (shm_base == MAP_FAILED) {
-                LOG_DBGF("Failed to map shared memory.");
-                if (close(shm_fd) == -1)
-                        LOG_DBGF("Failed to close invalid shm.");
-                if (shm_unlink(SHM_DU_MAP_FILENAME) == -1)
-                        LOG_DBGF("Failed to unlink invalid shm.");
-                free(dum);
-                return NULL;
-        }
-
-        dum->shm_base = shm_base;
-        dum->ptr_head = (size_t *)
-                ((uint8_t *) dum->shm_base + SHM_BLOCKS_SIZE);
-        dum->ptr_tail = dum->ptr_head + 1;
-        dum->lock = (pthread_mutex_t *) (dum->ptr_tail + 1);
-        dum->choked = (size_t *) (dum->lock + 1);
-        dum->healthy = (pthread_cond_t *) (dum->choked + 1);
-        dum->full = dum->healthy + 1;
-        dum->api = (pid_t *) (dum->full + 1);
-
-        dum->fd = shm_fd;
-
-        return dum;
-}
-
-void * shm_du_map_sanitize(void * o)
-{
-        struct shm_du_map * dum = (struct shm_du_map *) o;
-        struct timespec intv
-                = {SHM_DU_TIMEOUT_MICROS / MILLION,
-                   (SHM_DU_TIMEOUT_MICROS % MILLION) * 1000};
-
-        pid_t   api;
-
-        if (dum == NULL)
-                return (void *) -1;
-        if (pthread_mutex_lock(dum->lock) == EOWNERDEAD) {
-                LOG_WARN("Recovering dead mutex.");
-                pthread_mutex_consistent(dum->lock);
-        }
-
-        pthread_cleanup_push((void (*)(void *)) pthread_mutex_unlock,
-                             (void *) dum->lock);
-
-        while (true) {
-                int ret = 0;
-                struct timespec now;
-                struct timespec dl;
-
-                if (pthread_cond_wait(dum->full, dum->lock) == EOWNERDEAD) {
-                        LOG_WARN("Recovering dead mutex.");
-                        pthread_mutex_consistent(dum->lock);
-                }
-
-                *dum->choked = 1;
-
-                garbage_collect(dum);
-
-                if (shm_map_empty(dum))
-                        continue;
-
-                api = get_tail_ptr(dum)->dst_api;
-
-                if (kill(api, 0)) {
-                        LOG_DBGF("Dead process %d left stale sdu.", api);
-                        clean_sdus(dum, api, false);
-                        continue;
-                }
-
-                clock_gettime(CLOCK_REALTIME, &now);
-                ts_add(&now, &intv, &dl);
-                while (*dum->choked) {
-                        ret = pthread_cond_timedwait(dum->healthy,
-                                                     dum->lock,
-                                                     &dl);
-                        if (!ret)
-                                continue;
-
-                        if (ret == EOWNERDEAD) {
-                                LOG_WARN("Recovering dead mutex.");
-                                pthread_mutex_consistent(dum->lock);
-                        }
-
-                        if (ret == ETIMEDOUT) {
-                                LOG_DBGF("SDU timed out (dst: %d).", api);
-                                clean_sdus(dum, api, false);
-                        }
-                }
-        }
-
-        pthread_cleanup_pop(true);
-
-        return (void *) 0;
-}
-
-void shm_du_map_close_on_exit(struct shm_du_map * dum)
-{
-        if (dum == NULL) {
-                LOG_DBGF("Bogus input. Bugging out.");
-                return;
-        }
-
-        clean_sdus(dum, getpid(), true);
-
-        if (close(dum->fd) < 0)
-                LOG_DBGF("Couldn't close shared memory.");
-
-        if (munmap(dum->shm_base, SHM_FILE_SIZE) == -1)
-                LOG_DBGF("Couldn't unmap shared memory.");
-
-        free(dum);
-}
-
-void shm_du_map_close(struct shm_du_map * dum)
-{
-        if (dum == NULL) {
-                LOG_DBGF("Bogus input. Bugging out.");
-                return;
-        }
-
-        if (close(dum->fd) < 0)
-                LOG_DBGF("Couldn't close shared memory.");
-
-        if (munmap(dum->shm_base, SHM_FILE_SIZE) == -1)
-                LOG_DBGF("Couldn't unmap shared memory.");
-
-        free(dum);
-}
-
-void shm_du_map_destroy(struct shm_du_map * dum)
-{
-        if (dum == NULL) {
-                LOG_DBGF("Bogus input. Bugging out.");
-                return;
-        }
-
-        if (getpid() != *dum->api && kill(*dum->api, 0) == 0) {
-                LOG_DBGF("Only IRMd can destroy %s.", SHM_DU_MAP_FILENAME);
-                return;
-        }
-
-        if (close(dum->fd) < 0)
-                LOG_DBGF("Couldn't close shared memory.");
-
-        if (munmap(dum->shm_base, SHM_FILE_SIZE) == -1)
-                LOG_DBGF("Couldn't unmap shared memory.");
-
-        if (shm_unlink(SHM_DU_MAP_FILENAME) == -1)
-                LOG_DBGF("Failed to unlink shm.");
-
-        free(dum);
-}
-
-ssize_t shm_du_map_write(struct shm_du_map * dum,
-                         pid_t               dst_api,
-                         size_t              headspace,
-                         size_t              tailspace,
-                         uint8_t *           data,
-                         size_t              len)
-{
-        struct shm_du_buff * sdb;
-        size_t               size = headspace + len + tailspace;
-#ifdef SHM_DU_MAP_MULTI_BLOCK
-        long                 blocks = 0;
-        long                 padblocks = 0;
-#endif
-        int                  sz = size + sizeof *sdb;
-        uint8_t *            write_pos;
-        ssize_t              idx = -1;
-
-        if (dum == NULL || data == NULL) {
-                LOG_DBGF("Bogus input, bugging out.");
-                return -1;
-        }
-
-#ifndef SHM_DU_MAP_MULTI_BLOCK
-        if (sz > SHM_DU_BUFF_BLOCK_SIZE) {
-                LOG_DBGF("Multi-block SDU's disabled. Dropping.");
-                return -1;
-        }
-#endif
-        if (pthread_mutex_lock(dum->lock) == EOWNERDEAD) {
-                LOG_DBGF("Recovering dead mutex.");
-                pthread_mutex_consistent(dum->lock);
-        }
-#ifdef SHM_DU_MAP_MULTI_BLOCK
-        while (sz > 0) {
-                sz -= SHM_DU_BUFF_BLOCK_SIZE;
-                ++blocks;
-        }
-
-        if (blocks + *dum->ptr_head > SHM_BUFFER_SIZE)
-                padblocks = SHM_BUFFER_SIZE - *dum->ptr_head;
-
-        if (!shm_map_free(dum, (blocks + padblocks))) {
-#else
-        if (!shm_map_free(dum, 1)) {
-#endif
-                pthread_cond_signal(dum->full);
-                pthread_mutex_unlock(dum->lock);
-                return -1;
-        }
-
-#ifdef SHM_DU_MAP_MULTI_BLOCK
-        if (padblocks) {
-                sdb = get_head_ptr(dum);
-                sdb->size    = 0;
-                sdb->blocks  = padblocks;
-                sdb->dst_api = -1;
-                sdb->du_head = 0;
-                sdb->du_tail = 0;
-
-                *dum->ptr_head = 0;
-        }
-#endif
-        sdb          = get_head_ptr(dum);
-        sdb->size    = size;
-        sdb->dst_api = dst_api;
-        sdb->du_head = headspace;
-        sdb->du_tail = sdb->du_head + len;
-#ifdef  SHM_DU_MAP_MULTI_BLOCK
-        sdb->blocks  = blocks;
-#endif
-        write_pos = ((uint8_t *) (sdb + 1)) + headspace;
-
-        memcpy(write_pos, data, len);
-
-        idx = *dum->ptr_head;
-#ifdef SHM_DU_MAP_MULTI_BLOCK
-        *dum->ptr_head = (*dum->ptr_head + blocks) & (SHM_BUFFER_SIZE - 1);
-#else
-        *dum->ptr_head = (*dum->ptr_head + 1) & (SHM_BUFFER_SIZE - 1);
-#endif
-        pthread_mutex_unlock(dum->lock);
-
-        return idx;
-}
-
-ssize_t shm_du_map_write_b(struct shm_du_map * dum,
-                           pid_t               dst_api,
-                           size_t              headspace,
-                           size_t              tailspace,
-                           uint8_t *           data,
-                           size_t              len)
-{
-        struct shm_du_buff * sdb;
-        size_t               size = headspace + len + tailspace;
-#ifdef SHM_DU_MAP_MULTI_BLOCK
-        long                 blocks = 0;
-        long                 padblocks = 0;
-#endif
-        int                  sz = size + sizeof *sdb;
-        uint8_t *            write_pos;
-        ssize_t              idx = -1;
-
-        if (dum == NULL || data == NULL) {
-                LOG_DBGF("Bogus input, bugging out.");
-                return -1;
-        }
-
-#ifndef SHM_DU_MAP_MULTI_BLOCK
-        if (sz > SHM_DU_BUFF_BLOCK_SIZE) {
-                LOG_DBGF("Multi-block SDU's disabled. Dropping.");
-                return -1;
-        }
-#endif
-        if (pthread_mutex_lock(dum->lock) == EOWNERDEAD) {
-                LOG_DBGF("Recovering dead mutex.");
-                pthread_mutex_consistent(dum->lock);
-        }
-
-        pthread_cleanup_push((void(*)(void *))pthread_mutex_unlock,
-                             (void *) dum->lock);
-
-#ifdef SHM_DU_MAP_MULTI_BLOCK
-        while (sz > 0) {
-                sz -= SHM_DU_BUFF_BLOCK_SIZE;
-                ++blocks;
-        }
-
-        if (blocks + *dum->ptr_head > SHM_BUFFER_SIZE)
-                padblocks = SHM_BUFFER_SIZE - *dum->ptr_head;
-
-        while (!shm_map_free(dum, (blocks + padblocks))) {
-#else
-        while (!shm_map_free(dum, 1)) {
-#endif
-                pthread_cond_signal(dum->full);
-                pthread_cond_wait(dum->healthy, dum->lock);
-        }
-
-#ifdef SHM_DU_MAP_MULTI_BLOCK
-        if (padblocks) {
-                sdb = get_head_ptr(dum);
-                sdb->size    = 0;
-                sdb->blocks  = padblocks;
-                sdb->dst_api = -1;
-                sdb->du_head = 0;
-                sdb->du_tail = 0;
-
-                *dum->ptr_head = 0;
-        }
-#endif
-        sdb          = get_head_ptr(dum);
-        sdb->size    = size;
-        sdb->dst_api = dst_api;
-        sdb->du_head = headspace;
-        sdb->du_tail = sdb->du_head + len;
-#ifdef  SHM_DU_MAP_MULTI_BLOCK
-        sdb->blocks  = blocks;
-#endif
-        write_pos = ((uint8_t *) (sdb + 1)) + headspace;
-
-        memcpy(write_pos, data, len);
-
-        idx = *dum->ptr_head;
-#ifdef SHM_DU_MAP_MULTI_BLOCK
-        *dum->ptr_head = (*dum->ptr_head + blocks) & (SHM_BUFFER_SIZE - 1);
-#else
-        *dum->ptr_head = (*dum->ptr_head + 1) & (SHM_BUFFER_SIZE - 1);
-#endif
-        pthread_cleanup_pop(true);
-
-        return idx;
-}
-
-int shm_du_map_read(uint8_t **          dst,
-                    struct shm_du_map * dum,
-                    ssize_t             idx)
-{
-        size_t len = 0;
-        struct shm_du_buff * sdb;
-
-        if (idx > SHM_BUFFER_SIZE)
-                return -1;
-
-        if (pthread_mutex_lock(dum->lock) == EOWNERDEAD) {
-                LOG_DBGF("Recovering dead mutex.");
-                pthread_mutex_consistent(dum->lock);
-        }
-
-        if (shm_map_empty(dum)) {
-                pthread_mutex_unlock(dum->lock);
-                return -1;
-        }
-
-        sdb = idx_to_du_buff_ptr(dum, idx);
-        len = sdb->du_tail - sdb->du_head;
-        *dst = ((uint8_t *) (sdb + 1)) + sdb->du_head;
-
-        pthread_mutex_unlock(dum->lock);
-
-        return len;
-}
-
-int shm_du_map_remove(struct shm_du_map * dum, ssize_t idx)
-{
-        if (idx > SHM_BUFFER_SIZE)
-                return -1;
-
-        if (pthread_mutex_lock(dum->lock) == EOWNERDEAD) {
-                LOG_DBGF("Recovering dead mutex.");
-                pthread_mutex_consistent(dum->lock);
-        }
-
-        if (shm_map_empty(dum)) {
-                pthread_mutex_unlock(dum->lock);
-                return -1;
-        }
-
-        idx_to_du_buff_ptr(dum, idx)->dst_api = -1;
-
-        if (idx != *dum->ptr_tail) {
-                pthread_mutex_unlock(dum->lock);
-                return 0;
-        }
-
-        garbage_collect(dum);
-
-        *dum->choked = 0;
-
-        pthread_cond_broadcast(dum->healthy);
-
-        pthread_mutex_unlock(dum->lock);
-
-        return 0;
-}
-
-uint8_t * shm_du_buff_head_alloc(struct shm_du_map * dum,
-                                 int                 idx,
-                                 ssize_t             size)
-{
-        struct shm_du_buff * sdb;
-        uint8_t * buf;
-
-        if (dum  == NULL)
-                return NULL;
-
-        if (idx < 0 || idx > SHM_BUFFER_SIZE)
-                return NULL;
-
-        if (pthread_mutex_lock(dum->lock) == EOWNERDEAD) {
-                LOG_DBGF("Recovering dead mutex.");
-                pthread_mutex_consistent(dum->lock);
-        }
-
-        sdb = idx_to_du_buff_ptr(dum, idx);
-
-        if ((long) (sdb->du_head - size) < 0) {
-                pthread_mutex_unlock(dum->lock);
-                LOG_DBGF("Failed to allocate PCI headspace.");
-                return NULL;
-        }
-
-        sdb->du_head -= size;
-
-        buf = (uint8_t *) (sdb + 1) + sdb->du_head;
-
-        pthread_mutex_unlock(dum->lock);
-
-        return buf;
-}
-
-uint8_t * shm_du_buff_tail_alloc(struct shm_du_map * dum,
-                                 int                 idx,
-                                 ssize_t             size)
-{
-        struct shm_du_buff * sdb;
-        uint8_t * buf;
-
-        if (dum  == NULL)
-                return NULL;
-
-        if (idx < 0 || idx > SHM_BUFFER_SIZE)
-                return NULL;
-
-        if (pthread_mutex_lock(dum->lock) == EOWNERDEAD) {
-                LOG_DBGF("Recovering dead mutex.");
-                pthread_mutex_consistent(dum->lock);
-        }
-
-        sdb = idx_to_du_buff_ptr(dum, idx);
-
-        if (sdb->du_tail + size >= sdb->size) {
-                pthread_mutex_unlock(dum->lock);
-                LOG_DBGF("Failed to allocate PCI tailspace.");
-                return NULL;
-        }
-
-        buf = (uint8_t *) (sdb + 1) + sdb->du_tail;
-
-        sdb->du_tail += size;
-
-        pthread_mutex_unlock(dum->lock);
-
-        return buf;
-}
-
-int shm_du_buff_head_release(struct shm_du_map * dum,
-                             int                 idx,
-                             ssize_t             size)
-{
-        struct shm_du_buff * sdb;
-
-        if (dum  == NULL)
-                return -1;
-
-        if (idx < 0 || idx > SHM_BUFFER_SIZE)
-                return -1;
-
-        if (pthread_mutex_lock(dum->lock) == EOWNERDEAD) {
-                LOG_DBGF("Recovering dead mutex.");
-                pthread_mutex_consistent(dum->lock);
-        }
-
-        sdb = idx_to_du_buff_ptr(dum, idx);
-
-        if (size > sdb->du_tail - sdb->du_head) {
-                pthread_mutex_unlock(dum->lock);
-                LOG_DBGF("Tried to release beyond sdu boundary.");
-                return -EOVERFLOW;
-        }
-
-        sdb->du_head += size;
-
-        pthread_mutex_unlock(dum->lock);
-
-        return 0;
-}
-
-int shm_du_buff_tail_release(struct shm_du_map * dum,
-                             int                 idx,
-                             ssize_t             size)
-{
-        struct shm_du_buff * sdb;
-
-        if (dum  == NULL)
-                return -1;
-
-        if (idx < 0 || idx > SHM_BUFFER_SIZE)
-                return -1;
-
-        if (pthread_mutex_lock(dum->lock) == EOWNERDEAD) {
-                LOG_DBGF("Recovering dead mutex.");
-                pthread_mutex_consistent(dum->lock);
-        }
-
-        sdb = idx_to_du_buff_ptr(dum, idx);
-
-        if (size > sdb->du_tail - sdb->du_head) {
-                pthread_mutex_unlock(dum->lock);
-                LOG_DBGF("Tried to release beyond sdu boundary.");
-                return -EOVERFLOW;
-        }
-
-        sdb->du_tail -= size;
-
-        pthread_mutex_unlock(dum->lock);
-
-        return 0;
-}
diff --git a/src/lib/shm_rdrbuff.c b/src/lib/shm_rdrbuff.c
new file mode 100644
index 00000000..d42dbea7
--- /dev/null
+++ b/src/lib/shm_rdrbuff.c
@@ -0,0 +1,804 @@
+/*
+ * Ouroboros - Copyright (C) 2016
+ *
+ * Random Deletion Ring Buffer for Data Units
+ *
+ *    Dimitri Staessens <[email protected]>
+ *    Sander Vrijders   <[email protected]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * 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., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <ouroboros/config.h>
+#include <ouroboros/errno.h>
+#include <ouroboros/shm_rdrbuff.h>
+#include <ouroboros/shm_ap_rbuff.h>
+#include <ouroboros/time_utils.h>
+
+#include <pthread.h>
+#include <sys/mman.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+#include <signal.h>
+#include <sys/stat.h>
+
+#define OUROBOROS_PREFIX "shm_rdrbuff"
+
+#include <ouroboros/logs.h>
+
+#define SHM_BLOCKS_SIZE (SHM_BUFFER_SIZE * SHM_RDRB_BLOCK_SIZE)
+#define SHM_FILE_SIZE (SHM_BLOCKS_SIZE + 3 * sizeof (size_t)                   \
+                       + sizeof(pthread_mutex_t) + 2 * sizeof(pthread_cond_t)  \
+                       + sizeof(pid_t))
+
+#define get_head_ptr(rdrb)                                                     \
+        ((struct shm_du_buff *)(rdrb->shm_base + (*rdrb->ptr_head *            \
+                                                  SHM_RDRB_BLOCK_SIZE)))
+
+#define get_tail_ptr(rdrb)                                                     \
+        ((struct shm_du_buff *)(rdrb->shm_base + (*rdrb->ptr_tail *            \
+                                                  SHM_RDRB_BLOCK_SIZE)))
+
+#define idx_to_du_buff_ptr(rdrb, idx)                                          \
+        ((struct shm_du_buff *)(rdrb->shm_base + (idx * SHM_RDRB_BLOCK_SIZE)))
+
+#define block_ptr_to_idx(rdrb, sdb)                                            \
+        (((uint8_t *)sdb - rdrb->shm_base) / SHM_RDRB_BLOCK_SIZE)
+
+#define shm_rdrb_used(rdrb)                                                    \
+        ((*rdrb->ptr_head + SHM_BUFFER_SIZE - *rdrb->ptr_tail)                 \
+         & (SHM_BUFFER_SIZE - 1))
+#define shm_rdrb_free(rdrb, i)                                                 \
+        (shm_rdrb_used(rdrb) + i < SHM_BUFFER_SIZE)
+
+#define shm_rdrb_empty(rdrb)                                                   \
+        (*rdrb->ptr_tail == *rdrb->ptr_head)
+
+struct shm_du_buff {
+        size_t size;
+#ifdef SHM_DU_MAP_MULTI_BLOCK
+        size_t blocks;
+#endif
+        size_t du_head;
+        size_t du_tail;
+        pid_t  dst_api;
+};
+
+struct shm_rdrbuff {
+        uint8_t *         shm_base;    /* start of blocks */
+        size_t *          ptr_head;    /* start of ringbuffer head */
+        size_t *          ptr_tail;    /* start of ringbuffer tail */
+        pthread_mutex_t * lock;        /* lock all free space in shm */
+        size_t *          choked;      /* stale sdu detection */
+        pthread_cond_t *  healthy;     /* du map is healthy */
+        pthread_cond_t *  full;        /* run sanitizer when buffer full */
+        pid_t *           api;         /* api of the irmd owner */
+        enum qos_cube     qos;         /* qos id which this buffer serves */
+        int               fd;
+};
+
+static void garbage_collect(struct shm_rdrbuff * rdrb)
+{
+#ifdef SHM_RDRBUFF_MULTI_BLOCK
+        struct shm_du_buff * sdb;
+        while (!shm_rdrb_empty(rdrb) &&
+               (sdb = get_tail_ptr(rdrb))->dst_api == -1)
+                *rdrb->ptr_tail = (*rdrb->ptr_tail + sdb->blocks)
+                        & (SHM_BUFFER_SIZE - 1);
+#else
+        while (!shm_rdrb_empty(rdrb) && get_tail_ptr(rdrb)->dst_api == -1)
+                *rdrb->ptr_tail =
+                        (*rdrb->ptr_tail + 1) & (SHM_BUFFER_SIZE - 1);
+
+#endif
+}
+
+static void clean_sdus(struct shm_rdrbuff * rdrb, pid_t api)
+{
+        size_t idx = *rdrb->ptr_tail;
+        struct shm_du_buff * buf;
+
+        while (idx != *rdrb->ptr_head) {
+                buf = idx_to_du_buff_ptr(rdrb, idx);
+                if (buf->dst_api == api)
+                        buf->dst_api = -1;
+#ifdef SHM_RDRBUFF_MULTI_BLOCK
+                idx = (idx + buf->blocks) & (SHM_BUFFER_SIZE - 1);
+#else
+                idx = (idx + 1) & (SHM_BUFFER_SIZE - 1);
+#endif
+        }
+
+        garbage_collect(rdrb);
+
+        *rdrb->choked = 0;
+}
+
+static char * rdrb_filename(enum qos_cube qos)
+{
+        int chars = 0;
+        char * str;
+        int qm = QOS_MAX;
+
+        do {
+                qm /= 10;
+                ++chars;
+        } while (qm > 0);
+
+        str = malloc(strlen(SHM_RDRB_PREFIX) + chars + 2);
+        if (str == NULL) {
+                LOG_ERR("Failed to create shm_rdrbuff: Out of Memory.");
+                return NULL;
+        }
+
+        sprintf(str, "%s.%d", SHM_RDRB_PREFIX, (int) qos);
+
+        return str;
+}
+
+/* FIXME: create a ringbuffer for each qos cube in the system */
+struct shm_rdrbuff * shm_rdrbuff_create()
+{
+        struct shm_rdrbuff * rdrb;
+        int                  shm_fd;
+        uint8_t *            shm_base;
+        pthread_mutexattr_t  mattr;
+        pthread_condattr_t   cattr;
+        enum qos_cube        qos = QOS_CUBE_BE;
+        char *               shm_rdrb_fn = rdrb_filename(qos);
+        if (shm_rdrb_fn == NULL) {
+                LOG_ERR("Could not create rdrbuff. Out of Memory");
+                return NULL;
+        }
+
+        rdrb = malloc(sizeof *rdrb);
+        if (rdrb == NULL) {
+                LOG_DBGF("Could not allocate struct.");
+                return NULL;
+        }
+
+        shm_fd = shm_open(shm_rdrb_fn, O_CREAT | O_EXCL | O_RDWR, 0666);
+        if (shm_fd == -1) {
+                LOG_DBGF("Failed creating shared memory map.");
+                free(shm_rdrb_fn);
+                free(rdrb);
+                return NULL;
+        }
+
+        if (fchmod(shm_fd, 0666)) {
+                LOG_DBGF("Failed to chmod shared memory map.");
+                free(shm_rdrb_fn);
+                free(rdrb);
+                return NULL;
+        }
+
+        if (ftruncate(shm_fd, SHM_FILE_SIZE - 1) < 0) {
+                LOG_DBGF("Failed to extend shared memory map.");
+                free(shm_rdrb_fn);
+                free(rdrb);
+                return NULL;
+        }
+
+        if (write(shm_fd, "", 1) != 1) {
+                LOG_DBGF("Failed to finalise extension of shared memory map.");
+                free(shm_rdrb_fn);
+                free(rdrb);
+                return NULL;
+        }
+
+        shm_base = mmap(NULL,
+                        SHM_FILE_SIZE,
+                        PROT_READ | PROT_WRITE,
+                        MAP_SHARED,
+                        shm_fd,
+                        0);
+
+        if (shm_base == MAP_FAILED) {
+                LOG_DBGF("Failed to map shared memory.");
+                if (shm_unlink(shm_rdrb_fn) == -1)
+                        LOG_DBGF("Failed to remove invalid shm.");
+                free(shm_rdrb_fn);
+                free(rdrb);
+                return NULL;
+        }
+
+        rdrb->shm_base = shm_base;
+        rdrb->ptr_head = (size_t *)
+                ((uint8_t *) rdrb->shm_base + SHM_BLOCKS_SIZE);
+        rdrb->ptr_tail = rdrb->ptr_head + 1;
+        rdrb->lock = (pthread_mutex_t *) (rdrb->ptr_tail + 1);
+        rdrb->choked = (size_t *) (rdrb->lock + 1);
+        rdrb->healthy = (pthread_cond_t *) (rdrb->choked + 1);
+        rdrb->full = rdrb->healthy + 1;
+        rdrb->api = (pid_t *) (rdrb->full + 1);
+
+        pthread_mutexattr_init(&mattr);
+        pthread_mutexattr_setpshared(&mattr, PTHREAD_PROCESS_SHARED);
+        pthread_mutexattr_setrobust(&mattr, PTHREAD_MUTEX_ROBUST);
+        pthread_mutex_init(rdrb->lock, &mattr);
+
+        pthread_condattr_init(&cattr);
+        pthread_condattr_setpshared(&cattr, PTHREAD_PROCESS_SHARED);
+        pthread_cond_init(rdrb->full, &cattr);
+        pthread_cond_init(rdrb->healthy, &cattr);
+
+        *rdrb->ptr_head = 0;
+        *rdrb->ptr_tail = 0;
+
+        *rdrb->choked = 0;
+
+        *rdrb->api = getpid();
+
+        rdrb->qos = qos;
+        rdrb->fd  = shm_fd;
+
+        free(shm_rdrb_fn);
+
+        return rdrb;
+}
+
+/* FIXME: open a ringbuffer for each qos cube in the system */
+struct shm_rdrbuff * shm_rdrbuff_open()
+{
+        struct shm_rdrbuff * rdrb;
+        int                  shm_fd;
+        uint8_t *            shm_base;
+
+        enum qos_cube        qos = QOS_CUBE_BE;
+        char *               shm_rdrb_fn = rdrb_filename(qos);
+        if (shm_rdrb_fn == NULL) {
+                LOG_ERR("Could not create rdrbuff. Out of Memory");
+                return NULL;
+        }
+
+        rdrb = malloc(sizeof *rdrb);
+        if (rdrb == NULL) {
+                LOG_DBGF("Could not allocate struct.");
+                return NULL;
+        }
+
+        shm_fd = shm_open(shm_rdrb_fn, O_RDWR, 0666);
+        if (shm_fd < 0) {
+                LOG_DBGF("Failed opening shared memory.");
+                free(shm_rdrb_fn);
+                free(rdrb);
+                return NULL;
+        }
+
+        shm_base = mmap(NULL,
+                        SHM_FILE_SIZE,
+                        PROT_READ | PROT_WRITE,
+                        MAP_SHARED,
+                        shm_fd,
+                        0);
+        if (shm_base == MAP_FAILED) {
+                LOG_DBGF("Failed to map shared memory.");
+                if (close(shm_fd) == -1)
+                        LOG_DBG("Failed to close invalid shm.");
+                if (shm_unlink(shm_rdrb_fn) == -1)
+                        LOG_DBG("Failed to unlink invalid shm.");
+                free(shm_rdrb_fn);
+                free(rdrb);
+                return NULL;
+        }
+
+        rdrb->shm_base = shm_base;
+        rdrb->ptr_head = (size_t *)
+                ((uint8_t *) rdrb->shm_base + SHM_BLOCKS_SIZE);
+        rdrb->ptr_tail = rdrb->ptr_head + 1;
+        rdrb->lock = (pthread_mutex_t *) (rdrb->ptr_tail + 1);
+        rdrb->choked = (size_t *) (rdrb->lock + 1);
+        rdrb->healthy = (pthread_cond_t *) (rdrb->choked + 1);
+        rdrb->full = rdrb->healthy + 1;
+        rdrb->api = (pid_t *) (rdrb->full + 1);
+
+        rdrb->qos = qos;
+        rdrb->fd = shm_fd;
+
+        free(shm_rdrb_fn);
+
+        return rdrb;
+}
+
+void * shm_rdrbuff_sanitize(void * o)
+{
+        struct shm_rdrbuff * rdrb = (struct shm_rdrbuff *) o;
+        struct timespec intv
+                = {SHM_DU_TIMEOUT_MICROS / MILLION,
+                   (SHM_DU_TIMEOUT_MICROS % MILLION) * 1000};
+
+        pid_t   api;
+
+        if (rdrb == NULL)
+                return (void *) -1;
+
+        if (pthread_mutex_lock(rdrb->lock) == EOWNERDEAD) {
+                LOG_WARN("Recovering dead mutex.");
+                pthread_mutex_consistent(rdrb->lock);
+        }
+
+        pthread_cleanup_push((void (*)(void *)) pthread_mutex_unlock,
+                             (void *) rdrb->lock);
+
+        while (true) {
+                int ret = 0;
+                struct timespec now;
+                struct timespec dl;
+
+                if (pthread_cond_wait(rdrb->full, rdrb->lock) == EOWNERDEAD) {
+                        LOG_WARN("Recovering dead mutex.");
+                        pthread_mutex_consistent(rdrb->lock);
+                }
+
+                *rdrb->choked = 1;
+
+                garbage_collect(rdrb);
+
+                if (shm_rdrb_empty(rdrb))
+                        continue;
+
+                api = get_tail_ptr(rdrb)->dst_api;
+
+                if (kill(api, 0)) {
+                        LOG_DBGF("Dead process %d left stale sdu.", api);
+                        clean_sdus(rdrb, api);
+                        continue;
+                }
+
+                clock_gettime(CLOCK_REALTIME, &now);
+                ts_add(&now, &intv, &dl);
+                while (*rdrb->choked) {
+                        ret = pthread_cond_timedwait(rdrb->healthy,
+                                                     rdrb->lock,
+                                                     &dl);
+                        if (!ret)
+                                continue;
+
+                        if (ret == EOWNERDEAD) {
+                                LOG_WARN("Recovering dead mutex.");
+                                pthread_mutex_consistent(rdrb->lock);
+                        }
+
+                        if (ret == ETIMEDOUT) {
+                                LOG_DBGF("SDU timed out (dst: %d).", api);
+                                clean_sdus(rdrb, api);
+                        }
+                }
+        }
+
+        pthread_cleanup_pop(true);
+
+        return (void *) 0;
+}
+
+void shm_rdrbuff_close(struct shm_rdrbuff * rdrb)
+{
+        if (rdrb == NULL) {
+                LOG_DBGF("Bogus input. Bugging out.");
+                return;
+        }
+
+        if (close(rdrb->fd) < 0)
+                LOG_DBGF("Couldn't close shared memory.");
+
+        if (munmap(rdrb->shm_base, SHM_FILE_SIZE) == -1)
+                LOG_DBGF("Couldn't unmap shared memory.");
+
+        free(rdrb);
+}
+
+void shm_rdrbuff_destroy(struct shm_rdrbuff * rdrb)
+{
+        char * shm_rdrb_fn;
+
+        if (rdrb == NULL) {
+                LOG_DBGF("Bogus input. Bugging out.");
+                return;
+        }
+
+        if (getpid() != *rdrb->api && kill(*rdrb->api, 0) == 0) {
+                LOG_DBG("Process %d tried to destroy active rdrb.", getpid());
+                return;
+        }
+
+        if (close(rdrb->fd) < 0)
+                LOG_DBG("Couldn't close shared memory.");
+
+        if (munmap(rdrb->shm_base, SHM_FILE_SIZE) == -1)
+                LOG_DBG("Couldn't unmap shared memory.");
+
+        shm_rdrb_fn = rdrb_filename(rdrb->qos);
+        if (shm_rdrb_fn == NULL) {
+                LOG_ERR("Could not create rdrbuff. Out of Memory");
+                return;
+        }
+
+        if (shm_unlink(shm_rdrb_fn) == -1)
+                LOG_DBG("Failed to unlink shm.");
+
+        free(rdrb);
+        free(shm_rdrb_fn);
+}
+
+ssize_t shm_rdrbuff_write(struct shm_rdrbuff * rdrb,
+                          pid_t                dst_api,
+                          size_t               headspace,
+                          size_t               tailspace,
+                          uint8_t *            data,
+                          size_t               len)
+{
+        struct shm_du_buff * sdb;
+        size_t               size = headspace + len + tailspace;
+#ifdef SHM_RDRBUFF_MULTI_BLOCK
+        long                 blocks = 0;
+        long                 padblocks = 0;
+#endif
+        int                  sz = size + sizeof *sdb;
+        uint8_t *            write_pos;
+        ssize_t              idx = -1;
+
+        if (rdrb == NULL || data == NULL) {
+                LOG_DBGF("Bogus input, bugging out.");
+                return -1;
+        }
+
+#ifndef SHM_RDRBUFF_MULTI_BLOCK
+        if (sz > SHM_RDRB_BLOCK_SIZE) {
+                LOG_DBGF("Multi-block SDU's disabled. Dropping.");
+                return -1;
+        }
+#endif
+        if (pthread_mutex_lock(rdrb->lock) == EOWNERDEAD) {
+                LOG_DBGF("Recovering dead mutex.");
+                pthread_mutex_consistent(rdrb->lock);
+        }
+#ifdef SHM_RDRBUFF_MULTI_BLOCK
+        while (sz > 0) {
+                sz -= SHM_RDRB_BLOCK_SIZE;
+                ++blocks;
+        }
+
+        if (blocks + *rdrb->ptr_head > SHM_BUFFER_SIZE)
+                padblocks = SHM_BUFFER_SIZE - *rdrb->ptr_head;
+
+        if (!shm_rdrb_free(rdrb, (blocks + padblocks))) {
+#else
+        if (!shm_rdrb_free(rdrb, 1)) {
+#endif
+                pthread_cond_signal(rdrb->full);
+                pthread_mutex_unlock(rdrb->lock);
+                return -1;
+        }
+
+#ifdef SHM_RDRBUFF_MULTI_BLOCK
+        if (padblocks) {
+                sdb = get_head_ptr(rdrb);
+                sdb->size    = 0;
+                sdb->blocks  = padblocks;
+                sdb->dst_api = -1;
+                sdb->du_head = 0;
+                sdb->du_tail = 0;
+
+                *rdrb->ptr_head = 0;
+        }
+#endif
+        sdb          = get_head_ptr(rdrb);
+        sdb->size    = size;
+        sdb->dst_api = dst_api;
+        sdb->du_head = headspace;
+        sdb->du_tail = sdb->du_head + len;
+#ifdef  SHM_RDRBUFF_MULTI_BLOCK
+        sdb->blocks  = blocks;
+#endif
+        write_pos = ((uint8_t *) (sdb + 1)) + headspace;
+
+        memcpy(write_pos, data, len);
+
+        idx = *rdrb->ptr_head;
+#ifdef SHM_RDRBUFF_MULTI_BLOCK
+        *rdrb->ptr_head = (*rdrb->ptr_head + blocks) & (SHM_BUFFER_SIZE - 1);
+#else
+        *rdrb->ptr_head = (*rdrb->ptr_head + 1) & (SHM_BUFFER_SIZE - 1);
+#endif
+        pthread_mutex_unlock(rdrb->lock);
+
+        return idx;
+}
+
+ssize_t shm_rdrbuff_write_b(struct shm_rdrbuff * rdrb,
+                           pid_t               dst_api,
+                           size_t              headspace,
+                           size_t              tailspace,
+                           uint8_t *           data,
+                           size_t              len)
+{
+        struct shm_du_buff * sdb;
+        size_t               size = headspace + len + tailspace;
+#ifdef SHM_RDRBUFF_MULTI_BLOCK
+        long                 blocks = 0;
+        long                 padblocks = 0;
+#endif
+        int                  sz = size + sizeof *sdb;
+        uint8_t *            write_pos;
+        ssize_t              idx = -1;
+
+        if (rdrb == NULL || data == NULL) {
+                LOG_DBGF("Bogus input, bugging out.");
+                return -1;
+        }
+
+#ifndef SHM_RDRBUFF_MULTI_BLOCK
+        if (sz > SHM_RDRB_BLOCK_SIZE) {
+                LOG_DBGF("Multi-block SDU's disabled. Dropping.");
+                return -1;
+        }
+#endif
+        if (pthread_mutex_lock(rdrb->lock) == EOWNERDEAD) {
+                LOG_DBGF("Recovering dead mutex.");
+                pthread_mutex_consistent(rdrb->lock);
+        }
+
+        pthread_cleanup_push((void(*)(void *))pthread_mutex_unlock,
+                             (void *) rdrb->lock);
+
+#ifdef SHM_RDRBUFF_MULTI_BLOCK
+        while (sz > 0) {
+                sz -= SHM_RDRB_BLOCK_SIZE;
+                ++blocks;
+        }
+
+        if (blocks + *rdrb->ptr_head > SHM_BUFFER_SIZE)
+                padblocks = SHM_BUFFER_SIZE - *rdrb->ptr_head;
+
+        while (!shm_rdrb_free(rdrb, (blocks + padblocks))) {
+#else
+        while (!shm_rdrb_free(rdrb, 1)) {
+#endif
+                pthread_cond_signal(rdrb->full);
+                pthread_cond_wait(rdrb->healthy, rdrb->lock);
+        }
+
+#ifdef SHM_RDRBUFF_MULTI_BLOCK
+        if (padblocks) {
+                sdb = get_head_ptr(rdrb);
+                sdb->size    = 0;
+                sdb->blocks  = padblocks;
+                sdb->dst_api = -1;
+                sdb->du_head = 0;
+                sdb->du_tail = 0;
+
+                *rdrb->ptr_head = 0;
+        }
+#endif
+        sdb          = get_head_ptr(rdrb);
+        sdb->size    = size;
+        sdb->dst_api = dst_api;
+        sdb->du_head = headspace;
+        sdb->du_tail = sdb->du_head + len;
+#ifdef  SHM_RDRBUFF_MULTI_BLOCK
+        sdb->blocks  = blocks;
+#endif
+        write_pos = ((uint8_t *) (sdb + 1)) + headspace;
+
+        memcpy(write_pos, data, len);
+
+        idx = *rdrb->ptr_head;
+#ifdef SHM_RDRBUFF_MULTI_BLOCK
+        *rdrb->ptr_head = (*rdrb->ptr_head + blocks) & (SHM_BUFFER_SIZE - 1);
+#else
+        *rdrb->ptr_head = (*rdrb->ptr_head + 1) & (SHM_BUFFER_SIZE - 1);
+#endif
+        pthread_cleanup_pop(true);
+
+        return idx;
+}
+
+int shm_rdrbuff_read(uint8_t **           dst,
+                     struct shm_rdrbuff * rdrb,
+                     ssize_t              idx)
+{
+        size_t len = 0;
+        struct shm_du_buff * sdb;
+
+        if (idx > SHM_BUFFER_SIZE)
+                return -1;
+
+        if (pthread_mutex_lock(rdrb->lock) == EOWNERDEAD) {
+                LOG_DBGF("Recovering dead mutex.");
+                pthread_mutex_consistent(rdrb->lock);
+        }
+
+        if (shm_rdrb_empty(rdrb)) {
+                pthread_mutex_unlock(rdrb->lock);
+                return -1;
+        }
+
+        sdb = idx_to_du_buff_ptr(rdrb, idx);
+        len = sdb->du_tail - sdb->du_head;
+        *dst = ((uint8_t *) (sdb + 1)) + sdb->du_head;
+
+        pthread_mutex_unlock(rdrb->lock);
+
+        return len;
+}
+
+int shm_rdrbuff_remove(struct shm_rdrbuff * rdrb, ssize_t idx)
+{
+        if (idx > SHM_BUFFER_SIZE)
+                return -1;
+
+        if (pthread_mutex_lock(rdrb->lock) == EOWNERDEAD) {
+                LOG_DBGF("Recovering dead mutex.");
+                pthread_mutex_consistent(rdrb->lock);
+        }
+
+        if (shm_rdrb_empty(rdrb)) {
+                pthread_mutex_unlock(rdrb->lock);
+                return -1;
+        }
+
+        idx_to_du_buff_ptr(rdrb, idx)->dst_api = -1;
+
+        if (idx != *rdrb->ptr_tail) {
+                pthread_mutex_unlock(rdrb->lock);
+                return 0;
+        }
+
+        garbage_collect(rdrb);
+
+        *rdrb->choked = 0;
+
+        pthread_cond_broadcast(rdrb->healthy);
+
+        pthread_mutex_unlock(rdrb->lock);
+
+        return 0;
+}
+
+uint8_t * shm_du_buff_head_alloc(struct shm_rdrbuff * rdrb,
+                                 int                  idx,
+                                 ssize_t              size)
+{
+        struct shm_du_buff * sdb;
+        uint8_t * buf;
+
+        if (rdrb  == NULL)
+                return NULL;
+
+        if (idx < 0 || idx > SHM_BUFFER_SIZE)
+                return NULL;
+
+        if (pthread_mutex_lock(rdrb->lock) == EOWNERDEAD) {
+                LOG_DBGF("Recovering dead mutex.");
+                pthread_mutex_consistent(rdrb->lock);
+        }
+
+        sdb = idx_to_du_buff_ptr(rdrb, idx);
+
+        if ((long) (sdb->du_head - size) < 0) {
+                pthread_mutex_unlock(rdrb->lock);
+                LOG_DBGF("Failed to allocate PCI headspace.");
+                return NULL;
+        }
+
+        sdb->du_head -= size;
+
+        buf = (uint8_t *) (sdb + 1) + sdb->du_head;
+
+        pthread_mutex_unlock(rdrb->lock);
+
+        return buf;
+}
+
+uint8_t * shm_du_buff_tail_alloc(struct shm_rdrbuff * rdrb,
+                                 int                  idx,
+                                 ssize_t              size)
+{
+        struct shm_du_buff * sdb;
+        uint8_t * buf;
+
+        if (rdrb  == NULL)
+                return NULL;
+
+        if (idx < 0 || idx > SHM_BUFFER_SIZE)
+                return NULL;
+
+        if (pthread_mutex_lock(rdrb->lock) == EOWNERDEAD) {
+                LOG_DBGF("Recovering dead mutex.");
+                pthread_mutex_consistent(rdrb->lock);
+        }
+
+        sdb = idx_to_du_buff_ptr(rdrb, idx);
+
+        if (sdb->du_tail + size >= sdb->size) {
+                pthread_mutex_unlock(rdrb->lock);
+                LOG_DBGF("Failed to allocate PCI tailspace.");
+                return NULL;
+        }
+
+        buf = (uint8_t *) (sdb + 1) + sdb->du_tail;
+
+        sdb->du_tail += size;
+
+        pthread_mutex_unlock(rdrb->lock);
+
+        return buf;
+}
+
+int shm_du_buff_head_release(struct shm_rdrbuff * rdrb,
+                             int                  idx,
+                             ssize_t              size)
+{
+        struct shm_du_buff * sdb;
+
+        if (rdrb  == NULL)
+                return -1;
+
+        if (idx < 0 || idx > SHM_BUFFER_SIZE)
+                return -1;
+
+        if (pthread_mutex_lock(rdrb->lock) == EOWNERDEAD) {
+                LOG_DBGF("Recovering dead mutex.");
+                pthread_mutex_consistent(rdrb->lock);
+        }
+
+        sdb = idx_to_du_buff_ptr(rdrb, idx);
+
+        if (size > sdb->du_tail - sdb->du_head) {
+                pthread_mutex_unlock(rdrb->lock);
+                LOG_DBGF("Tried to release beyond sdu boundary.");
+                return -EOVERFLOW;
+        }
+
+        sdb->du_head += size;
+
+        pthread_mutex_unlock(rdrb->lock);
+
+        return 0;
+}
+
+int shm_du_buff_tail_release(struct shm_rdrbuff * rdrb,
+                             int                  idx,
+                             ssize_t              size)
+{
+        struct shm_du_buff * sdb;
+
+        if (rdrb  == NULL)
+                return -1;
+
+        if (idx < 0 || idx > SHM_BUFFER_SIZE)
+                return -1;
+
+        if (pthread_mutex_lock(rdrb->lock) == EOWNERDEAD) {
+                LOG_DBGF("Recovering dead mutex.");
+                pthread_mutex_consistent(rdrb->lock);
+        }
+
+        sdb = idx_to_du_buff_ptr(rdrb, idx);
+
+        if (size > sdb->du_tail - sdb->du_head) {
+                pthread_mutex_unlock(rdrb->lock);
+                LOG_DBGF("Tried to release beyond sdu boundary.");
+                return -EOVERFLOW;
+        }
+
+        sdb->du_tail -= size;
+
+        pthread_mutex_unlock(rdrb->lock);
+
+        return 0;
+}