Adds the draft of the XDP scheduler testing tool

This commit contains the XDP scheduling framework. It consists of a
testing program called xdq-tester used to test schedulers using the XDP
and DEQUEUE hooks. It does this using trace files written in Lua that
the xdq-tester program uses to check the XDP schedulers for correctness.

I changed the name to xdq-tester because I found the old name too long.
I reused the XDQ name because I sometimes find it hard to distinguish
between the XDP hook or the XDP and DEQUEUE hooks in text or code. I am
sure we can find a better name later.

Like before, the FIFO and PIFO schedulers are fully functional in this
commit. However, it defines flows as UDP port numbers instead of using
five tuples that I am currently finishing now.

This program version has two issues that I need to resolve, but I have
not spent much time on them. The first issue is that the WFQ scheduler
fails to dequeue its third packet. The second issue is that the upstream
bpf-examples now includes libxdp, and I have not updated my code to work
with it. However, when I have libxdp support, I suspect that I can
finally use the lib/util/logging.h as part of my project to get more
verbose output.

Signed-off-by: Frey Alfredsson <freysteinn@freysteinn.com>

Author: freysteinn

xdq-tester/Makefile

@@ -0,0 +1,10 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+
+USER_TARGETS   := xdq-tester
+BPF_TARGETS    := $(patsubst %.c,%,$(wildcard *.bpf.c))
+
+USER_LIBS = -llua -ldl -lm
+
+LIB_DIR = ../lib
+
+include $(LIB_DIR)/common.mk

xdq-tester/bpf_local_helpers.h

@@ -0,0 +1,77 @@
+// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
+
+#define EEXIST      17  /* File exists */
+
+#define BPF_MAP_TYPE_PIFO_GENERIC 31
+#define BPF_MAP_TYPE_PIFO_XDP 32
+
+/*
+ * bpf_packet_dequeue
+ *
+ *      Dequeue the packet at the head of the PIFO in *map* and return a pointer
+ *      to the packet (or NULL if the PIFO is empty).
+ *
+ * Returns
+ *      On success, a pointer to the packet, or NULL if the PIFO is empty. The
+ *      packet pointer must be freed using *bpf_packet_drop()* or returning
+ *      the packet pointer. The *rank* pointer will be set to the rank of
+ *      the dequeued packet on success, or a negative error code on error.
+ */
+static long (*bpf_packet_dequeue)(void *ctx, void *map, __u64 flags, __u64 *rank) = (void *) 194;
+static long (*bpf_packet_drop)(void *ctx, void *pkt) = (void *) 195;
+
+struct flow_address {
+	struct in6_addr ip;
+	__u16 port;
+	__u16 reserved;
+};
+
+struct network_tuple {
+	struct flow_address saddr;
+	struct flow_address daddr;
+	__u16 proto;
+	__u8 ipv;
+	__u8 reserved;
+};
+
+struct flow_state {
+	__u32 pkts;
+	__u32 finish_bytes;
+};
+
+
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wunused-function"
+static __always_inline void *
+bpf_map_lookup_or_try_init(void *map, const void *key, const void *init)
+{
+        void *val;
+        long err;
+
+        val = bpf_map_lookup_elem(map, key);
+        if (val)
+                return val;
+
+        err = bpf_map_update_elem(map, key, init, BPF_NOEXIST);
+        if (err && err != -EEXIST)
+                return NULL;
+
+        return bpf_map_lookup_elem(map, key);
+}
+
+static __always_inline int bpf_max(__u64 left, __u64 right)
+{
+        return right > left ? right : left;
+}
+
+
+/*
+ * Maps an IPv4 address into an IPv6 address according to RFC 4291 sec 2.5.5.2
+ */
+static void map_ipv4_to_ipv6(struct in6_addr *ipv6, __be32 ipv4)
+{
+	__builtin_memset(&ipv6->in6_u.u6_addr8[0], 0x00, 10);
+	__builtin_memset(&ipv6->in6_u.u6_addr8[10], 0xff, 2);
+	ipv6->in6_u.u6_addr32[3] = ipv4;
+}
+#pragma GCC diagnostic pop

xdq-tester/fifo.lua

@@ -0,0 +1,25 @@
+-- SPDX-License-Identifier: GPL-2.0
+-- Copyright (c) 2022 Freysteinn Alfredsson <freysteinn@freysteinn.com>
+
+-- FIFO scheduler
+config.bpf.file = "./sched_fifo.bpf.o"
+
+-- Setup flows
+packet_flow1 = Udp:new()
+packet_flow1.udp.port = 8080
+
+packet_flow2 = Udp:new()
+packet_flow2.udp.port = 8081
+
+packet_flow3 = Udp:new()
+packet_flow3.udp.port = 8082
+
+
+-- Test scheduler
+enqueue(packet_flow1)
+enqueue(packet_flow2)
+enqueue(packet_flow3)
+
+dequeue_cmp(packet_flow1)
+dequeue_cmp(packet_flow2)
+dequeue_cmp(packet_flow3)