From 048c960756eb65301a72d2d7c41218906bd63204 Mon Sep 17 00:00:00 2001
From: "Jesper D. Brouer" <netoptimizer@brouer.com>
Date: Tue, 1 Dec 2020 14:27:10 +0100
Subject: [PATCH] iproute2 tc util have recently gotten libbpf support

Implement configure script that detect support, and Makefile
defines that propagate to BPF-C file, making it possible to
use and compile with BTF type maps.

Signed-off-by: Jesper D. Brouer <netoptimizer@brouer.com>
---
 traffic-pacing-edt/Makefile          | 13 ++++++++++++-
 traffic-pacing-edt/configure         | 29 ++++++++++++++++++++++++++++
 traffic-pacing-edt/edt_pacer02.c     | 22 +++++++++++++++++----
 traffic-pacing-edt/iproute2_compat.h |  6 ++++++
 4 files changed, 65 insertions(+), 5 deletions(-)
 create mode 100755 traffic-pacing-edt/configure

diff --git a/traffic-pacing-edt/Makefile b/traffic-pacing-edt/Makefile
index cb3def9..73c1306 100644
--- a/traffic-pacing-edt/Makefile
+++ b/traffic-pacing-edt/Makefile
@@ -4,11 +4,20 @@ USER_TARGETS :=
 BPF_TARGETS := edt_pacer01
 BPF_TARGETS += edt_pacer02
 
+EXTRA_DEPS += config.mk
+
 LIB_DIR = ../lib
 
 include $(LIB_DIR)/common.mk
+include config.mk
 
-# The iproute2 'tc' tool doesn't understand BTF debug info
+all: config.mk
+
+config.mk: configure
+	@sh configure
+
+ifndef HAVE_TC_LIBBPF
+# If the iproute2 'tc' tool doesn't understand BTF debug info
 # use llvm-strip to remove this debug info from object file
 #
 # *BUT* cannot strip everything as it removes ELF elems needed for
@@ -16,6 +25,8 @@ include $(LIB_DIR)/common.mk
 #
 .PHONY: strip_tc_obj
 strip_tc_obj: ${BPF_TARGETS:=.o}
+	$(Q) echo "TC don't support libbpf - strip BTF info"
 	$(Q) llvm-strip --no-strip-all --remove-section .BTF $?
 
 all: strip_tc_obj
+endif
diff --git a/traffic-pacing-edt/configure b/traffic-pacing-edt/configure
new file mode 100755
index 0000000..9b01369
--- /dev/null
+++ b/traffic-pacing-edt/configure
@@ -0,0 +1,29 @@
+#!/bin/bash
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+# This is not an autoconf generated configure
+#
+
+# Output file which is input to Makefile
+CONFIG=config.mk
+
+# Assume tc is in $PATH
+TC=tc
+
+check_tc_libbpf()
+{
+    tc_version=$($TC -V)
+    if echo $tc_version | grep -q libbpf; then
+	libbpf_version=${tc_version##*libbpf }
+	echo "HAVE_TC_LIBBPF:=y" >> $CONFIG
+	echo "CFLAGS += -DHAVE_LIBBPF" >> $CONFIG
+	echo "yes ($libbpf_version)"
+    else
+	echo "no"
+    fi
+}
+
+echo "# Generated config" > $CONFIG
+echo "Detecting available features on system"
+
+echo -n " - libbpf support in tc tool: "
+check_tc_libbpf
diff --git a/traffic-pacing-edt/edt_pacer02.c b/traffic-pacing-edt/edt_pacer02.c
index 5b89d4a..a361079 100644
--- a/traffic-pacing-edt/edt_pacer02.c
+++ b/traffic-pacing-edt/edt_pacer02.c
@@ -2,7 +2,6 @@
 #include <linux/bpf.h>
 #include <bpf/bpf_helpers.h>
 #include <bpf/compiler.h>
-#include "iproute2_compat.h"
 
 #include <stdbool.h>
 
@@ -59,16 +58,31 @@ struct edt_val {
 	struct codel_state codel;
 } __aligned(64); /* Align struct to cache-size to avoid false-sharing */
 
-/* The tc tool (iproute2) use another ELF map layout than libbpf (struct
- * bpf_map_def), see struct bpf_elf_map from iproute2.
+#ifdef HAVE_TC_LIBBPF /* detected by configure script in config.mk */
+/* Use BTF format to create map */
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__uint(max_entries, 4096); /* Max possible VLANs */
+	__type(key, __u32);
+	__type(value, struct edt_val);
+//	__uint(pinning, LIBBPF_PIN_BY_NAME);
+} time_delay_map SEC(".maps");
+
+#else
+/* The (iproute2) tc tool (without libbpf support) use another ELF map
+ * layout than libbpf (struct bpf_map_def), see struct bpf_elf_map
+ * from iproute2.
  */
+#include "iproute2_compat.h"
 struct bpf_elf_map SEC("maps") time_delay_map = {
 	.type		= BPF_MAP_TYPE_ARRAY,
 	.size_key	= sizeof(__u32),
 	.size_value	= sizeof(struct edt_val),
 	.max_elem	= 4096, /* Max possible VLANs */
-	//.pinning	= PIN_GLOBAL_NS,
+//	.pinning	= PIN_GLOBAL_NS,
 };
+#endif
+
 
 /* Role of EDT (Earliest Departure Time) is to schedule departure of packets to
  * be send in the future.
diff --git a/traffic-pacing-edt/iproute2_compat.h b/traffic-pacing-edt/iproute2_compat.h
index a535f5f..3d72546 100644
--- a/traffic-pacing-edt/iproute2_compat.h
+++ b/traffic-pacing-edt/iproute2_compat.h
@@ -1,4 +1,5 @@
 /* SPDX-License-Identifier: GPL-2.0 */
+/* Taken from from #include <iproute2/bpf_elf.h> */
 
 #ifndef __IPROUTE2_COMPAT_H
 #define __IPROUTE2_COMPAT_H
@@ -8,6 +9,11 @@
  * binary layout until "flags". Thus, BPF-progs can use both if careful.
  */
 
+/* Object pinning settings */
+#define PIN_NONE                0
+#define PIN_OBJECT_NS           1
+#define PIN_GLOBAL_NS           2
+
 /* ELF map definition (copied from iproute2 source code) */
 struct bpf_elf_map {
 	__u32 type;