ofproto-dpif-sflow: allow sFlow to infer the agent device.

Bug #2407.

AUTHORS

@@ -26,6 +26,7 @@ Joe Perches             joe@perches.com
 Jun Nakajima            jun.nakajima@intel.com
 Justin Pettit           jpettit@nicira.com
 Keith Amidon            keith@nicira.com
+Luca Giraudo            lgiraudo@nicira.com
 Martin Casado           casado@nicira.com
 Natasha Gude            natasha@nicira.com
 Neil McKee              neil.mckee@inmon.com

NEWS

@@ -20,6 +20,8 @@ v1.4.0 - xx xxx xxxx
          now be properly mirrored for any flows, regardless of their
          actions.
        - Track packet and byte statistics sent on mirrors.
+       - The sFlow implementation can now usually infer the correct agent
+         device instead of having to be told explicitly.
     - ovs-appctl:
       - New "fdb/flush" command to flush bridge's MAC learning table.
     - ovs-test:

lib/netdev.c

@@ -692,6 +692,26 @@ netdev_set_in4(struct netdev *netdev, struct in_addr addr, struct in_addr mask)
             : EOPNOTSUPP);
 }
 
+/* Obtains ad IPv4 address from device name and save the address in
+ * in4.  Returns 0 if successful, otherwise a positive errno value.
+ */
+int
+netdev_get_in4_by_name(const char *device_name, struct in_addr *in4)
+{
+    struct netdev *netdev;
+    int error;
+
+    error = netdev_open(device_name, "system", &netdev);
+    if (error) {
+        in4->s_addr = htonl(0);
+        return error;
+    }
+
+    error = netdev_get_in4(netdev, in4, NULL);
+    netdev_close(netdev);
+    return error;
+}
+
 /* Adds 'router' as a default IP gateway for the TCP/IP stack that corresponds
  * to 'netdev'. */
 int

lib/netdev.h

@@ -131,6 +131,7 @@ int netdev_set_advertisements(struct netdev *, uint32_t advertise);
 int netdev_get_in4(const struct netdev *, struct in_addr *address,
                    struct in_addr *netmask);
 int netdev_set_in4(struct netdev *, struct in_addr addr, struct in_addr mask);
+int netdev_get_in4_by_name(const char *device_name, struct in_addr *in4);
 int netdev_get_in6(const struct netdev *, struct in6_addr *);
 int netdev_add_router(struct netdev *, struct in_addr router);
 int netdev_get_next_hop(const struct netdev *, const struct in_addr *host,

ofproto/ofproto-dpif-sflow.c

@@ -18,6 +18,7 @@
 #include <config.h>
 #include "ofproto-dpif-sflow.h"
 #include <inttypes.h>
+#include <net/if.h>
 #include <stdlib.h>
 #include "collectors.h"
 #include "compiler.h"
@@ -30,6 +31,7 @@
 #include "ofproto.h"
 #include "packets.h"
 #include "poll-loop.h"
+#include "route-table.h"
 #include "sflow_api.h"
 #include "socket-util.h"
 #include "timeval.h"
@@ -223,25 +225,35 @@ sflow_agent_get_counters(void *ds_, SFLPoller *poller,
  * The sFlow agent address should be a local IP address that is persistent and
  * reachable over the network, if possible.  The IP address associated with
  * 'agent_device' is used if it has one, and otherwise 'control_ip', the IP
- * address used to talk to the controller. */
+ * address used to talk to the controller.  If the agent device is not
+ * specified then it is figured out by taking a look at the routing table based
+ * on 'targets'. */
 static bool
-sflow_choose_agent_address(const char *agent_device, const char *control_ip,
+sflow_choose_agent_address(const char *agent_device,
+                           const struct sset *targets,
+                           const char *control_ip,
                            SFLAddress *agent_addr)
 {
+    const char *target;
     struct in_addr in4;
 
     memset(agent_addr, 0, sizeof *agent_addr);
     agent_addr->type = SFLADDRESSTYPE_IP_V4;
 
     if (agent_device) {
-        struct netdev *netdev;
+        if (!netdev_get_in4_by_name(agent_device, &in4)) {
+            goto success;
+        }
+    }
 
-        if (!netdev_open(agent_device, "system", &netdev)) {
-            int error = netdev_get_in4(netdev, &in4, NULL);
-            netdev_close(netdev);
-            if (!error) {
-                goto success;
-            }
+    SSET_FOR_EACH (target, targets) {
+        struct sockaddr_in sin;
+        char name[IFNAMSIZ];
+
+        if (inet_parse_active(target, SFL_DEFAULT_COLLECTOR_PORT, &sin)
+            && route_table_get_name(sin.sin_addr.s_addr, name)
+            && !netdev_get_in4_by_name(name, &in4)) {
+            goto success;
         }
     }
 
@@ -289,6 +301,8 @@ dpif_sflow_create(struct dpif *dpif)
     ds->next_tick = time_now() + 1;
     hmap_init(&ds->ports);
     ds->probability = 0;
+    route_table_register();
+
     return ds;
 }
 
@@ -307,6 +321,7 @@ dpif_sflow_destroy(struct dpif_sflow *ds)
     if (ds) {
         struct dpif_sflow_port *dsp, *next;
 
+        route_table_unregister();
         dpif_sflow_clear(ds);
         HMAP_FOR_EACH_SAFE (dsp, next, hmap_node, &ds->ports) {
             dpif_sflow_del_port__(ds, dsp);
@@ -430,6 +445,14 @@ dpif_sflow_set_options(struct dpif_sflow *ds,
         }
     }
 
+    /* Choose agent IP address and agent device (if not yet setup) */
+    if (!sflow_choose_agent_address(options->agent_device,
+                                    &options->targets,
+                                    options->control_ip, &agentIP)) {
+        dpif_sflow_clear(ds);
+        return;
+    }
+
     /* Avoid reconfiguring if options didn't change. */
     if (!options_changed) {
         return;
@@ -437,13 +460,6 @@ dpif_sflow_set_options(struct dpif_sflow *ds,
     ofproto_sflow_options_destroy(ds->options);
     ds->options = ofproto_sflow_options_clone(options);
 
-    /* Choose agent IP address. */
-    if (!sflow_choose_agent_address(options->agent_device,
-                                    options->control_ip, &agentIP)) {
-        dpif_sflow_clear(ds);
-        return;
-    }
-
     /* Create agent. */
     VLOG_INFO("creating sFlow agent %d", options->sub_id);
     if (ds->sflow_agent) {
@@ -572,6 +588,7 @@ dpif_sflow_run(struct dpif_sflow *ds)
 {
     if (dpif_sflow_is_enabled(ds)) {
         time_t now = time_now();
+        route_table_run();
         if (now >= ds->next_tick) {
             sfl_agent_tick(ds->sflow_agent, time_wall());
             ds->next_tick = now + 1;

vswitchd/vswitch.xml

@@ -2771,10 +2771,12 @@
 
     <column name="agent">
       Name of the network device whose IP address should be reported as the
-      ``agent address'' to collectors.  If not specified, the IP address
+      ``agent address'' to collectors.  If not specified, the agent device is
+      figured from the first target address and the routing table.  If the
+      routing table does not contain a route to the target, the IP address
       defaults to the <ref table="Controller" column="local_ip"/> in the
       collector's <ref table="Controller"/>.  If an agent IP address cannot be
-      determined either way, sFlow is disabled.
+      determined any of these ways, sFlow is disabled.
     </column>
 
     <column name="header">