[PATCH bpf-next 02/10] [bpf]: adding tests for bpf_xdp_adjust_tail

["Nikita V. Shirokov" <tehnerd@tehnerd.com>]

adding selftests for bpf_xdp_adjust_tail helper. in this syntetic test
we are testing that 1) if data_end < data helper will return EINVAL
2) for normal use case packet's length would be reduced.

aside from adding new tests i'm changing behaviour of bpf_prog_test_run
so it would recalculate packet's length if only data_end pointer was
changed

Signed-off-by: Nikita V. Shirokov <tehnerd@tehnerd.com>
---
 net/bpf/test_run.c                             |  3 ++-
 tools/include/uapi/linux/bpf.h                 | 11 ++++++++-
 tools/testing/selftests/bpf/Makefile           |  2 +-
 tools/testing/selftests/bpf/bpf_helpers.h      |  3 +++
 tools/testing/selftests/bpf/test_adjust_tail.c | 29 +++++++++++++++++++++++
 tools/testing/selftests/bpf/test_progs.c       | 32 ++++++++++++++++++++++++++
 6 files changed, 77 insertions(+), 3 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/test_adjust_tail.c

diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index 2ced48662c1f..68c3578343b4 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -170,7 +170,8 @@ int bpf_prog_test_run_xdp(struct bpf_prog *prog, const union bpf_attr *kattr,
 	xdp.rxq = &rxqueue->xdp_rxq;
 
 	retval = bpf_test_run(prog, &xdp, repeat, &duration);
-	if (xdp.data != data + XDP_PACKET_HEADROOM + NET_IP_ALIGN)
+	if (xdp.data != data + XDP_PACKET_HEADROOM + NET_IP_ALIGN ||
+	    xdp.data_end != xdp.data + size)
 		size = xdp.data_end - xdp.data;
 	ret = bpf_test_finish(kattr, uattr, xdp.data, size, retval, duration);
 	kfree(data);
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 9d07465023a2..9a2d1a04eb24 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -755,6 +755,13 @@ union bpf_attr {
  *     @addr: pointer to struct sockaddr to bind socket to
  *     @addr_len: length of sockaddr structure
  *     Return: 0 on success or negative error code
+ *
+ * int bpf_xdp_adjust_tail(xdp_md, delta)
+ *     Adjust the xdp_md.data_end by delta. Only shrinking of packet's
+ *     size is supported.
+ *     @xdp_md: pointer to xdp_md
+ *     @delta: A negative integer to be added to xdp_md.data_end
+ *     Return: 0 on success or negative on error
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -821,7 +828,8 @@ union bpf_attr {
 	FN(msg_apply_bytes),		\
 	FN(msg_cork_bytes),		\
 	FN(msg_pull_data),		\
-	FN(bind),
+	FN(bind),			\
+	FN(xdp_adjust_tail),
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
  * function eBPF program intends to call
@@ -864,6 +872,7 @@ enum bpf_func_id {
 /* BPF_FUNC_skb_set_tunnel_key flags. */
 #define BPF_F_ZERO_CSUM_TX		(1ULL << 1)
 #define BPF_F_DONT_FRAGMENT		(1ULL << 2)
+#define BPF_F_SEQ_NUMBER		(1ULL << 3)
 
 /* BPF_FUNC_perf_event_output, BPF_FUNC_perf_event_read and
  * BPF_FUNC_perf_event_read_value flags.
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 0a315ddabbf4..3e819dc70bee 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -31,7 +31,7 @@ TEST_GEN_FILES = test_pkt_access.o test_xdp.o test_l4lb.o test_tcp_estats.o test
 	sockmap_verdict_prog.o dev_cgroup.o sample_ret0.o test_tracepoint.o \
 	test_l4lb_noinline.o test_xdp_noinline.o test_stacktrace_map.o \
 	sample_map_ret0.o test_tcpbpf_kern.o test_stacktrace_build_id.o \
-	sockmap_tcp_msg_prog.o connect4_prog.o connect6_prog.o
+	sockmap_tcp_msg_prog.o connect4_prog.o connect6_prog.o test_adjust_tail.o
 
 # Order correspond to 'make run_tests' order
 TEST_PROGS := test_kmod.sh \
diff --git a/tools/testing/selftests/bpf/bpf_helpers.h b/tools/testing/selftests/bpf/bpf_helpers.h
index d8223d99f96d..50c607014b22 100644
--- a/tools/testing/selftests/bpf/bpf_helpers.h
+++ b/tools/testing/selftests/bpf/bpf_helpers.h
@@ -96,6 +96,9 @@ static int (*bpf_msg_pull_data)(void *ctx, int start, int end, int flags) =
 	(void *) BPF_FUNC_msg_pull_data;
 static int (*bpf_bind)(void *ctx, void *addr, int addr_len) =
 	(void *) BPF_FUNC_bind;
+static int (*bpf_xdp_adjust_tail)(void *ctx, int offset) =
+	(void *) BPF_FUNC_xdp_adjust_tail;
+
 
 /* llvm builtin functions that eBPF C program may use to
  * emit BPF_LD_ABS and BPF_LD_IND instructions
diff --git a/tools/testing/selftests/bpf/test_adjust_tail.c b/tools/testing/selftests/bpf/test_adjust_tail.c
new file mode 100644
index 000000000000..86239e792d6d
--- /dev/null
+++ b/tools/testing/selftests/bpf/test_adjust_tail.c
@@ -0,0 +1,29 @@
+/* Copyright (c) 2016,2017 Facebook
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ */
+#include <linux/bpf.h>
+#include <linux/if_ether.h>
+#include "bpf_helpers.h"
+
+int _version SEC("version") = 1;
+
+SEC("xdp_adjust_tail")
+int _xdp_adjust_tail(struct xdp_md *xdp)
+{
+	void *data_end = (void *)(long)xdp->data_end;
+	void *data = (void *)(long)xdp->data;
+	int offset = 0;
+
+	if (data_end - data == 54)
+		offset = 256;
+	else
+		offset = 20;
+	if (bpf_xdp_adjust_tail(xdp, 0 - offset))
+		return XDP_DROP;
+	return XDP_TX;
+}
+
+char _license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/test_progs.c b/tools/testing/selftests/bpf/test_progs.c
index faadbe233966..eedda98d7bb1 100644
--- a/tools/testing/selftests/bpf/test_progs.c
+++ b/tools/testing/selftests/bpf/test_progs.c
@@ -166,6 +166,37 @@ static void test_xdp(void)
 	bpf_object__close(obj);
 }
 
+static void test_xdp_adjust_tail(void)
+{
+	const char *file = "./test_adjust_tail.o";
+	struct bpf_object *obj;
+	char buf[128];
+	__u32 duration, retval, size;
+	int err, prog_fd;
+
+	err = bpf_prog_load(file, BPF_PROG_TYPE_XDP, &obj, &prog_fd);
+	if (err) {
+		error_cnt++;
+		return;
+	}
+
+	err = bpf_prog_test_run(prog_fd, 1, &pkt_v4, sizeof(pkt_v4),
+				buf, &size, &retval, &duration);
+
+	CHECK(err || errno || retval != XDP_DROP,
+	      "ipv4", "err %d errno %d retval %d size %d\n",
+	      err, errno, retval, size);
+
+	err = bpf_prog_test_run(prog_fd, 1, &pkt_v6, sizeof(pkt_v6),
+				buf, &size, &retval, &duration);
+	CHECK(err || errno || retval != XDP_TX || size != 54,
+	      "ipv6", "err %d errno %d retval %d size %d\n",
+	      err, errno, retval, size);
+	bpf_object__close(obj);
+}
+
+
+
 #define MAGIC_VAL 0x1234
 #define NUM_ITER 100000
 #define VIP_NUM 5
@@ -1177,6 +1208,7 @@ int main(void)
 {
 	test_pkt_access();
 	test_xdp();
+	test_xdp_adjust_tail();
 	test_l4lb_all();
 	test_xdp_noinline();
 	test_tcp_estats();
-- 
2.15.1