netmap: implement 'threads: auto'

Add until function for retrieving RSS RX count from netmap. Use the
RSS count to create the threads.

src/runmode-netmap.c

@@ -180,7 +180,7 @@ static void *ParseNetmapConfig(const char *iface_name)
         aconf->threads = 1;
     } else {
         if (strcmp(threadsstr, "auto") == 0) {
-            aconf->threads = GetIfaceRSSQueuesNum(aconf->iface);
+            aconf->threads = NetmapGetRSSCount(aconf->iface);
         } else {
             aconf->threads = (uint8_t)atoi(threadsstr);
         }

src/source-netmap.c

@@ -277,6 +277,46 @@ static int NetmapSetIfaceFlags(int fd, const char *ifname, int flags)
     return 0;
 }
 
+/** \brief get RSS RX-queue count
+ *  \retval rx_rings RSS RX queue count or 1 on error
+ */
+int NetmapGetRSSCount(const char *ifname)
+{
+    struct nmreq nm_req;
+    int rx_rings = 1;
+
+    SCMutexLock(&netmap_devlist_lock);
+
+    /* open netmap */
+    int fd = open("/dev/netmap", O_RDWR);
+    if (fd == -1) {
+        SCLogError(SC_ERR_NETMAP_CREATE,
+                "Couldn't open netmap device, error %s",
+                strerror(errno));
+        goto error_open;
+    }
+
+    /* query netmap info */
+    memset(&nm_req, 0, sizeof(nm_req));
+    strlcpy(nm_req.nr_name, ifname, sizeof(nm_req.nr_name));
+    nm_req.nr_version = NETMAP_API;
+
+    if (ioctl(fd, NIOCGINFO, &nm_req) != 0) {
+        SCLogError(SC_ERR_NETMAP_CREATE,
+                "Couldn't query netmap for %s, error %s",
+                ifname, strerror(errno));
+        goto error_fd;
+    };
+
+    rx_rings = nm_req.nr_rx_rings;
+
+error_fd:
+    close(fd);
+error_open:
+    SCMutexUnlock(&netmap_devlist_lock);
+    return rx_rings;
+}
+
 /**
  * \brief Open interface in netmap mode.
  * \param ifname Interface name.

src/source-netmap.h

@@ -67,6 +67,8 @@ typedef struct NetmapPacketVars_
     void *ntv;
 } NetmapPacketVars;
 
+int NetmapGetRSSCount(const char *ifname);
+
 void TmModuleReceiveNetmapRegister (void);
 void TmModuleDecodeNetmapRegister (void);