dp-core: Add dynamic offload module registration

Extend the paravirtualized per-host type offloads with infrastructure
that allows arbitrary modules to plug into the framework. This closely
resembles the offload register/unregister callbacks that were present in
versions R3.1 and R4.1, with the addition of dpdk support (under Linux).

RCU is used to ensure integrity of the offload structure upon
plugging/unplugging. The registration interface exposes symbols when
building the vrouter kernel module. A framework for user space plugging
is not yet available, but dynamic loading could be used to achieve this.

Change-Id: Ifa2ea8af5b0abfeb4e732a4f68d48cf42bd8739f
Depends-On: Ieb451b6374918ef4ad2476610ba013b80aa83ce0
Partial-Bug: #1767107
Signed-off-by: Frik Botha <frederick.botha@netronome.com>

dp-core/vr_flow.c

@@ -20,7 +20,7 @@
 #include "vr_ip_mtrie.h"
 #include "vr_bridge.h"
 
-#include "vr_offloads.h"
+#include "vr_offloads_dp.h"
 
 #define VR_NUM_FLOW_TABLES          1
 

dp-core/vr_interface.c

@@ -16,7 +16,7 @@
 #include "vr_btable.h"
 #include "vr_route.h"
 #include "vr_ip_mtrie.h"
-#include "vr_offloads.h"
+#include "vr_offloads_dp.h"
 
 unsigned int vr_interfaces = VR_MAX_INTERFACES;
 

dp-core/vr_mirror.c

@@ -9,7 +9,7 @@
 #include "vr_sandesh.h"
 #include "vr_message.h"
 #include "vr_mirror.h"
-#include "vr_offloads.h"
+#include "vr_offloads_dp.h"
 
 struct vr_mirror_entry *
 vrouter_get_mirror(unsigned int rid, unsigned int index)

dp-core/vr_mpls.c

@@ -13,7 +13,7 @@
 #include "vr_bridge.h"
 #include "vr_datapath.h"
 #include "vr_btable.h"
-#include "vr_offloads.h"
+#include "vr_offloads_dp.h"
 
 unsigned int vr_mpls_labels = VR_DEF_LABELS;
 

dp-core/vr_nexthop.c

@@ -18,7 +18,7 @@
 #include "vr_route.h"
 #include "vr_hash.h"
 #include "vr_mirror.h"
-#include "vr_offloads.h"
+#include "vr_offloads_dp.h"
 
 extern bool vr_has_to_fragment(struct vr_interface *, struct vr_packet *,
         unsigned int);

dp-core/vr_offloads.c

@@ -4,7 +4,7 @@
  * Copyright 2018 Mellanox Technologies, Ltd
  */
 #include <vrouter.h>
-#include <vr_offloads.h>
+#include <vr_offloads_dp.h>
 #include <vr_btable.h>
 #include <vr_packet.h>
 
@@ -357,13 +357,25 @@ int
 vr_offloads_init(struct vrouter *router)
 {
     unsigned int entry_size;
+    struct vr_offload_ops *offload;
 
     if (!datapath_offloads)
         return 0;
 
+    /* Do not initialize twice. E.g. a soft reset would not have unregistered
+     * the offloads. */
+    offload = vr_rcu_dereference(offload_ops);
+    if (offload)
+        return 0;
+
     if (!vr_offload_flow_destroy || !vr_offload_flow_create ||
-        !vr_offload_prepare)
-        return -ENOSYS;
+        !vr_offload_prepare) {
+        /* Not an error necessarily. Offloads are not implemented for this host
+         * type, so don't register anything. External implementation can still
+         * be registered after initialization. */
+        vr_printf("offload: no built-in offload implementation for current context\n");
+        return 0;
+    }
 
     if (!offload_tags) {
         /* Round up to the next divisor */
@@ -387,14 +399,14 @@ vr_offloads_init(struct vrouter *router)
         }
     }
 
-    offload_ops = &vr_offload_ops;
+    vr_offload_register(&vr_offload_ops);
 
     return 0;
 
 }
 
-void
-vr_offloads_exit(struct vrouter *router, bool soft_reset)
+static void
+_vr_offloads_exit(struct vrouter *router, bool soft_reset)
 {
     struct vr_offload_flow *oflow;
     struct vr_offload_tag *otag;
@@ -443,7 +455,6 @@ vr_offloads_exit(struct vrouter *router, bool soft_reset)
 
     pvif = NULL;
     host_ip = 0;
-    offload_ops = NULL;
 }
 
 inline struct vr_offload_flow *
@@ -458,3 +469,68 @@ vr_offloads_flow_get(unsigned int index)
 
     return  oflow;
 }
+
+/*
+ * Called by an external offload module to register itself with vrouter.
+ */
+int
+vr_offload_register(const struct vr_offload_ops *new_handler)
+{
+    struct vr_offload_ops *offload;
+
+    if (!datapath_offloads || !new_handler)
+        return -EINVAL;
+
+    offload = vr_rcu_dereference(offload_ops);
+    if (offload)
+        return -EBUSY;
+
+    offload = vr_malloc(sizeof(*offload), VR_MALLOC_OBJECT);
+    if (!offload)
+        return -ENOMEM;
+    *offload = *new_handler;
+    vr_rcu_assign_pointer(offload_ops, offload);
+    vr_synchronize_rcu();
+
+    return 0;
+}
+#if defined(__linux__) && defined(__KERNEL__)
+EXPORT_SYMBOL(vr_offload_register);
+#endif
+
+/*
+ * Called by an external offload module to unregister itself with vrouter.
+ */
+static void
+_vr_offload_unregister(void)
+{
+    struct vr_offload_ops *offload = vr_rcu_dereference(offload_ops);
+
+    if (offload) {
+        vr_rcu_assign_pointer(offload_ops, NULL);
+        vr_synchronize_rcu();
+        vr_free(offload, VR_MALLOC_OBJECT);
+    }
+}
+
+int
+vr_offload_unregister(void)
+{
+    struct vrouter *router = vrouter_get(0);
+
+    _vr_offloads_exit(router, false);
+    _vr_offload_unregister();
+
+    return 0;
+}
+#if defined(__linux__) && defined(__KERNEL__)
+EXPORT_SYMBOL(vr_offload_unregister);
+#endif
+
+void
+vr_offloads_exit(struct vrouter *router, bool soft_reset)
+{
+    _vr_offloads_exit(router, soft_reset);
+    if (!soft_reset)
+        _vr_offload_unregister();
+}

dp-core/vr_qos.c

@@ -13,7 +13,7 @@
 #include "vr_interface.h"
 #include "vr_datapath.h"
 #include "vr_qos.h"
-#include "vr_offloads.h"
+#include "vr_offloads_dp.h"
 
 unsigned int vr_qos_map_entries = VR_DEF_QOS_MAP_ENTRIES;
 unsigned int vr_fc_map_entries = VR_DEF_FC_MAP_ENTRIES;

dp-core/vr_route.c

@@ -9,7 +9,7 @@
 #include <vr_route.h>
 #include "vr_message.h"
 #include "vr_sandesh.h"
-#include "vr_offloads.h"
+#include "vr_offloads_dp.h"
 
 unsigned int vr_vrfs = VR_DEF_VRFS;
 

dp-core/vr_stats.c

@@ -7,7 +7,7 @@
 #include <vr_os.h>
 #include <vr_types.h>
 #include <vr_packet.h>
-#include <vr_offloads.h>
+#include <vr_offloads_dp.h>
 #include "vr_message.h"
 #include "vr_btable.h"
 

dp-core/vr_vrf_assign.c

@@ -8,7 +8,7 @@
 #include "vr_message.h"
 #include "vr_sandesh.h"
 #include "vr_packet.h"
-#include "vr_offloads.h"
+#include "vr_offloads_dp.h"
 #include <vr_interface.h>
 #include <vr_response.h>
 

dp-core/vr_vxlan.c

@@ -12,7 +12,7 @@
 #include "vr_vxlan.h"
 #include "vr_bridge.h"
 #include "vr_datapath.h"
-#include "vr_offloads.h"
+#include "vr_offloads_dp.h"
 
 int
 vr_vxlan_input(struct vrouter *router, struct vr_packet *pkt,

dp-core/vrouter.c

@@ -23,7 +23,7 @@
 #include <vr_mirror.h>
 #include <vr_vxlan.h>
 #include <vr_qos.h>
-#include <vr_offloads.h>
+#include <vr_offloads_dp.h>
 
 static struct vrouter router;
 struct host_os *vrouter_host;

dpdk/SConscript

@@ -21,7 +21,7 @@ env.Append(LIBPATH = ['../host', '../sandesh', '../dp-core'])
 
 # Libraries
 env.Replace(LIBS = ['dp_core', 'dp_sandesh_c', 'dp_core', 'sandesh-c'])
-env.Append(LIBS = ['rt', 'dl', 'pthread', 'urcu-qsbr'])
+env.Append(LIBS = ['rt', 'dl', 'pthread', 'urcu-qsbr', 'urcu-bp'])
 env.Append(LINKFLAGS = env['DPDK_LINKFLAGS'])
 
 dpdk_objs = env.Object(Glob('*.c'))