MLX5: modify if_indextoname syscall to support F-Stack tools.

doc/Launch_F-Stack_on_AWS_EC2_in_one_minute.md

@@ -3,14 +3,13 @@
   If you have a Redhat7.3 EC2 instance，and then execute the following cmds, you will get the F-Stack server in one minute 
 
     sudo -i
-    yum install -y git gcc openssl-devel kernel-devel-$(uname -r) bc numactl-devel mkdir make net-tools vim pciutils iproute pcre-devel zlib-devel elfutils-libelf-devel vim
+    yum install -y git gcc openssl-devel kernel-devel-$(uname -r) bc numactl-devel mkdir make net-tools vim pciutils iproute pcre-devel zlib-devel elfutils-libelf-devel meson
 
     mkdir /data/f-stack
     git clone https://github.com/F-Stack/f-stack.git /data/f-stack
 
     # Compile DPDK
     cd /data/f-stack/dpdk
-    cd dpdk/
     meson -Denable_kmods=true build
     ninja -C build
     ninja -C build install

dpdk/drivers/net/mlx5/linux/mlx5_ethdev_os.c

@@ -23,6 +23,7 @@
 #include <stdalign.h>
 #include <sys/un.h>
 #include <time.h>
+#include <dlfcn.h>
 
 #include <rte_ethdev_driver.h>
 #include <rte_bus_pci.h>
@@ -1027,6 +1028,7 @@ mlx5_sysfs_check_switch_info(bool device_dir,
  * @return
  *   0 on success, a negative errno value otherwise and rte_errno is set.
  */
+static int (*real_if_indextoname)(unsigned int, char *);
 int
 mlx5_sysfs_switch_info(unsigned int ifindex, struct mlx5_switch_info *info)
 {
@@ -1046,7 +1048,16 @@ mlx5_sysfs_switch_info(unsigned int ifindex, struct mlx5_switch_info *info)
 	char c;
 	int ret;
 
-	if (!if_indextoname(ifindex, ifname)) {
+	// for ff tools
+	if (!real_if_indextoname) {
+		real_if_indextoname = dlsym(RTLD_NEXT, "if_indextoname");
+		if (!real_if_indextoname) {
+			rte_errno = errno;
+			return -rte_errno;
+		}
+	}
+
+	if (!real_if_indextoname(ifindex, ifname)) {
 		rte_errno = errno;
 		return -rte_errno;
 	}