ss: fix libbpf version check for ENABLE_BPF_SKSTORAGE_SUPPORT

This patch fixes a problem with the libbpf version comparison to decide
if ENABLE_BPF_SKSTORAGE_SUPPORT could be enabled.

- The code enabled by ENABLE_BPF_SKSTORAGE_SUPPORT uses the function
  btf_dump__new with an API that was introduced in libbpf 0.6.0. So
  check now against libbpf version to be >= 0.6.x instead of 0.5.x.

- This code still depends on the necessity to have LIBBPF_MAJOR_VERSION
  and LIBBPF_MINOR_VERSION defined, even if libbpf_version.h is not
  present in the library development package. This was ensured with
  the previous patch for the configure script.

Fixes: e3ecf048 ("ss: pretty-print BPF socket-local storage")
Signed-off-by: Stefan Mätje <stefan.maetje@esd.eu>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>

misc/ss.c

@@ -53,7 +53,7 @@
 #include <linux/mptcp.h>
 
 #ifdef HAVE_LIBBPF
-/* If libbpf is new enough (0.5+), support for pretty-printing BPF socket-local
+/* If libbpf is new enough (0.6+), support for pretty-printing BPF socket-local
  * storage is enabled, otherwise we emit a warning and disable it.
  * ENABLE_BPF_SKSTORAGE_SUPPORT is only used to gate the socket-local storage
  * feature, so this wouldn't prevent any feature relying on HAVE_LIBBPF to be
@@ -66,8 +66,8 @@
 #include <bpf/libbpf.h>
 #include <linux/btf.h>
 
-#if (LIBBPF_MAJOR_VERSION == 0) && (LIBBPF_MINOR_VERSION < 5)
-#warning "libbpf version 0.5 or later is required, disabling BPF socket-local storage support"
+#if ((LIBBPF_MAJOR_VERSION == 0) && (LIBBPF_MINOR_VERSION < 6))
+#warning "libbpf version 0.6 or later is required, disabling BPF socket-local storage support"
 #undef ENABLE_BPF_SKSTORAGE_SUPPORT
 #endif
 #endif