Commit ce6f6cff authored by Martin KaFai Lau's avatar Martin KaFai Lau Committed by Andrii Nakryiko
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selftests/bpf: Wait for the netstamp_needed_key static key to be turned on 



After the previous patch that speeded up the test (by avoiding neigh
discovery in IPv6), the BPF CI occasionally hits this error:

rcv tstamp unexpected pkt rcv tstamp: actual 0 == expected 0

The test complains about the cmsg returned from the recvmsg() does not
have the rcv timestamp. Setting skb->tstamp or not is
controlled by a kernel static key "netstamp_needed_key". The static
key is enabled whenever this is at least one sk with the SOCK_TIMESTAMP
set.

The test_redirect_dtime does use setsockopt() to turn on
the SOCK_TIMESTAMP for the reading sk. In the kernel
net_enable_timestamp() has a delay to enable the "netstamp_needed_key"
when CONFIG_JUMP_LABEL is set. This potential delay is the likely reason
for packet missing rcv timestamp occasionally.

This patch is to create udp sockets with SOCK_TIMESTAMP set.
It sends and receives some packets until the received packet
has a rcv timestamp. It currently retries at most 5 times with 1s
in between. This should be enough to wait for the "netstamp_needed_key".
It then holds on to the socket and only closes it at the end of the test.
This guarantees that the test has the "netstamp_needed_key" key turned
on from the beginning.

To simplify the udp sockets setup, they are sending/receiving packets
in the same netns (ns_dst is used) and communicate over the "lo" dev.
Hence, the patch enables the "lo" dev in the ns_dst.

Fixes: c803475f ("bpf: selftests: test skb->tstamp in redirect_neigh")
Signed-off-by: default avatarMartin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240120060518.3604920-2-martin.lau@linux.dev
parent 177f1d08

tools/testing/selftests/bpf/prog_tests/tc_redirect.c

+75 −4
Original line number Diff line number Diff line
@@ -291,6 +291,7 @@ static int netns_setup_links_and_routes(struct netns_setup_result *result) 
	SYS(fail, "ip addr add " IP4_DST "/32 dev dst");

	SYS(fail, "ip addr add " IP6_DST "/128 dev dst nodad");

	SYS(fail, "ip link set dev dst up");

	SYS(fail, "ip link set dev lo up");



	SYS(fail, "ip route add " IP4_SRC "/32 dev dst scope global");

	SYS(fail, "ip route add " IP4_NET "/16 dev dst scope global");
@@ -468,7 +469,7 @@ static int set_forwarding(bool enable) 
	return 0;

}



static void rcv_tstamp(int fd, const char *expected, size_t s)

static int __rcv_tstamp(int fd, const char *expected, size_t s, __u64 *tstamp)

{

	struct __kernel_timespec pkt_ts = {};

	char ctl[CMSG_SPACE(sizeof(pkt_ts))];
@@ -489,7 +490,7 @@ static void rcv_tstamp(int fd, const char *expected, size_t s) 


	ret = recvmsg(fd, &msg, 0);

	if (!ASSERT_EQ(ret, s, "recvmsg"))

		return;

		return -1;

	ASSERT_STRNEQ(data, expected, s, "expected rcv data");



	cmsg = CMSG_FIRSTHDR(&msg);
@@ -498,6 +499,12 @@ static void rcv_tstamp(int fd, const char *expected, size_t s) 
		memcpy(&pkt_ts, CMSG_DATA(cmsg), sizeof(pkt_ts));



	pkt_ns = pkt_ts.tv_sec * NSEC_PER_SEC + pkt_ts.tv_nsec;

	if (tstamp) {

		/* caller will check the tstamp itself */

		*tstamp = pkt_ns;

		return 0;

	}



	ASSERT_NEQ(pkt_ns, 0, "pkt rcv tstamp");



	ret = clock_gettime(CLOCK_REALTIME, &now_ts);
@@ -507,6 +514,60 @@ static void rcv_tstamp(int fd, const char *expected, size_t s) 
	if (ASSERT_GE(now_ns, pkt_ns, "check rcv tstamp"))

		ASSERT_LT(now_ns - pkt_ns, 5 * NSEC_PER_SEC,

			  "check rcv tstamp");

	return 0;

}



static void rcv_tstamp(int fd, const char *expected, size_t s)

{

	__rcv_tstamp(fd, expected, s, NULL);

}



static int wait_netstamp_needed_key(void)

{

	int opt = 1, srv_fd = -1, cli_fd = -1, nretries = 0, err, n;

	char buf[] = "testing testing";

	struct nstoken *nstoken;

	__u64 tstamp = 0;



	nstoken = open_netns(NS_DST);

	if (!nstoken)

		return -1;



	srv_fd = start_server(AF_INET6, SOCK_DGRAM, "::1", 0, 0);

	if (!ASSERT_GE(srv_fd, 0, "start_server"))

		goto done;



	err = setsockopt(srv_fd, SOL_SOCKET, SO_TIMESTAMPNS_NEW,

			 &opt, sizeof(opt));

	if (!ASSERT_OK(err, "setsockopt(SO_TIMESTAMPNS_NEW)"))

		goto done;



	cli_fd = connect_to_fd(srv_fd, TIMEOUT_MILLIS);

	if (!ASSERT_GE(cli_fd, 0, "connect_to_fd"))

		goto done;



again:

	n = write(cli_fd, buf, sizeof(buf));

	if (!ASSERT_EQ(n, sizeof(buf), "send to server"))

		goto done;

	err = __rcv_tstamp(srv_fd, buf, sizeof(buf), &tstamp);

	if (!ASSERT_OK(err, "__rcv_tstamp"))

		goto done;

	if (!tstamp && nretries++ < 5) {

		sleep(1);

		printf("netstamp_needed_key retry#%d\n", nretries);

		goto again;

	}



done:

	if (!tstamp && srv_fd != -1) {

		close(srv_fd);

		srv_fd = -1;

	}

	if (cli_fd != -1)

		close(cli_fd);

	close_netns(nstoken);

	return srv_fd;

}



static void snd_tstamp(int fd, char *b, size_t s)
@@ -843,11 +904,20 @@ static void test_tc_redirect_dtime(struct netns_setup_result *setup_result) 
{

	struct test_tc_dtime *skel;

	struct nstoken *nstoken;

	int err;

	int hold_tstamp_fd, err;



	/* Hold a sk with the SOCK_TIMESTAMP set to ensure there

	 * is no delay in the kernel net_enable_timestamp().

	 * This ensures the following tests must have

	 * non zero rcv tstamp in the recvmsg().

	 */

	hold_tstamp_fd = wait_netstamp_needed_key();

	if (!ASSERT_GE(hold_tstamp_fd, 0, "wait_netstamp_needed_key"))

		return;



	skel = test_tc_dtime__open();

	if (!ASSERT_OK_PTR(skel, "test_tc_dtime__open"))

		return;

		goto done;



	skel->rodata->IFINDEX_SRC = setup_result->ifindex_src_fwd;

	skel->rodata->IFINDEX_DST = setup_result->ifindex_dst_fwd;
@@ -892,6 +962,7 @@ static void test_tc_redirect_dtime(struct netns_setup_result *setup_result) 


done:

	test_tc_dtime__destroy(skel);

	close(hold_tstamp_fd);

}



static void test_tc_redirect_neigh_fib(struct netns_setup_result *setup_result)