selftests/net: ignore background traffic in psock_fanout

The packet fanout test generates UDP traffic and reads this with a pair of packet sockets, testing the various fanout algorithms. Avoid non-determinism from reading unrelated background traffic. Fanout decisions are made before unrelated packets can be dropped with a filter, so that is an insufficient strategy [*]. Run the packet socket tests in a network namespace, similar to msg_zerocopy. It it still good practice to install a filter on a packet socket before accepting traffic. Because this is example code, demonstrate that pattern. Open the socket initially bound to no protocol, install a filter, and only then bind to ETH_P_IP. Another source of non-determinism is hash collisions in FANOUT_HASH. The hash function used to select a socket in the fanout group includes the pseudorandom number hashrnd, which is not visible from userspace. To work around this, the test tries to find a pair of UDP source ports that do not collide. It gives up too soon (5 times, every 32 runs) and output is confusing. Increase tries to 20 and revise the error msg. [*] another approach would be to add a third socket to the fanout group and direct all unexpected traffic here. This is possible only when reimplementing methods like RR or HASH alongside this extra catch-all bucket, using the BPF fanout method.

Willem de Bruijn committed 8 years ago

Commit cc30c931 parent 3c69f793 files · +51 −8Browse files

Unified · Split

3 files

tools/testing/selftests/net/in_netns.sh +23 −0
tools/testing/selftests/net/psock_fanout.c +26 −6
tools/testing/selftests/net/run_afpackettests +2 −2

tools/testing/selftests/net/in_netns.sh+23−0

@@ -0,0 +1,23 @@
	1	#!/bin/sh
	2	# SPDX-License-Identifier: GPL-2.0
	3	#
	4	# Execute a subprocess in a network namespace
	5
	6	set -e
	7
	8	readonly NETNS="ns-$(mktemp -u XXXXXX)"
	9
	10	setup() {
	11	ip netns add "${NETNS}"
	12	ip -netns "${NETNS}" link set lo up
	13	}
	14
	15	cleanup() {
	16	ip netns del "${NETNS}"
	17	}
	18
	19	trap cleanup EXIT
	20	setup
	21
	22	"$@"
	23	exit "$?"

tools/testing/selftests/net/psock_fanout.c+26−6

 #include <linux/filter.h>
 #include <linux/bpf.h>
 #include <linux/if_packet.h>
+#include <net/if.h>
 #include <net/ethernet.h>
 #include <netinet/ip.h>
 #include <netinet/udp.h>
  * @return -1 if mode is bad, a valid socket otherwise */
 static int sock_fanout_open(uint16_t typeflags, uint16_t group_id)
 {
+	struct sockaddr_ll addr = {0};
 	int fd, val;
-	fd = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_IP));
+	fd = socket(PF_PACKET, SOCK_RAW, 0);
 	if (fd < 0) {
 		perror("socket packet");
 		exit(1);
 	}
+	pair_udp_setfilter(fd);
+	addr.sll_family = AF_PACKET;
+	addr.sll_protocol = htons(ETH_P_IP);
+	addr.sll_ifindex = if_nametoindex("lo");
+	if (addr.sll_ifindex == 0) {
+		perror("if_nametoindex");
+		exit(1);
+	}
+	if (bind(fd, (void *) &addr, sizeof(addr))) {
+		perror("bind packet");
+		exit(1);
+	}
 	val = (((int) typeflags) << 16) | group_id;
 	if (setsockopt(fd, SOL_PACKET, PACKET_FANOUT, &val, sizeof(val))) {
 		if (close(fd)) {
 		return -1;
 	}
-	pair_udp_setfilter(fd);
 	return fd;
 }
 	if ((!(ret[0] == expect[0] && ret[1] == expect[1])) &&
 	    (!(ret[0] == expect[1] && ret[1] == expect[0]))) {
-		fprintf(stderr, "ERROR: incorrect queue lengths\n");
+		fprintf(stderr, "warning: incorrect queue lengths\n");
 		return 1;
 	}
 	uint8_t type = typeflags & 0xFF;
 	int fds[2], fds_udp[2][2], ret;
-	fprintf(stderr, "test: datapath 0x%hx\n", typeflags);
+	fprintf(stderr, "\ntest: datapath 0x%hx ports %hu,%hu\n",
+		typeflags, PORT_BASE, PORT_BASE + port_off);
 	fds[0] = sock_fanout_open(typeflags, 0);
 	fds[1] = sock_fanout_open(typeflags, 0);
 	const int expect_cpu1[2][2]	= { { 0, 20 },  { 0, 20 } };
 	const int expect_bpf[2][2]	= { { 15, 5 },  { 15, 20 } };
 	const int expect_uniqueid[2][2] = { { 20, 20},  { 20, 20 } };
-	int port_off = 2, tries = 5, ret;
+	int port_off = 2, tries = 20, ret;
 	test_control_single();
 	test_control_group();
 	/* find a set of ports that do not collide onto the same socket */
 	ret = test_datapath(PACKET_FANOUT_HASH, port_off,
 			    expect_hash[0], expect_hash[1]);
-	while (ret && tries--) {
+	while (ret) {
 		fprintf(stderr, "info: trying alternate ports (%d)\n", tries);
 		ret = test_datapath(PACKET_FANOUT_HASH, ++port_off,
 				    expect_hash[0], expect_hash[1]);
+		if (!--tries) {
+			fprintf(stderr, "too many collisions\n");
+			return 1;
+		}
 	}
 	ret |= test_datapath(PACKET_FANOUT_HASH | PACKET_FANOUT_FLAG_ROLLOVER,

tools/testing/selftests/net/run_afpackettests+2−2

@@ -9,7 +9,7 @@ fi · 8 unmodified lines
9	echo "--------------------"	9	echo "--------------------"
10	echo "running psock_fanout test"	10	echo "running psock_fanout test"
11	echo "--------------------"	11	echo "--------------------"
12	./psock_fanout	12	./in_netns.sh ./psock_fanout
13	if [ $? -ne 0 ]; then	13	if [ $? -ne 0 ]; then
14	echo "[FAIL]"	14	echo "[FAIL]"
15	else	15	else
@@ -19,7 +19,7 @@ fi · 3 unmodified lines
19	echo "--------------------"	19	echo "--------------------"
20	echo "running psock_tpacket test"	20	echo "running psock_tpacket test"
21	echo "--------------------"	21	echo "--------------------"
22	./psock_tpacket	22	./in_netns.sh ./psock_tpacket
23	if [ $? -ne 0 ]; then	23	if [ $? -ne 0 ]; then
24	echo "[FAIL]"	24	echo "[FAIL]"
25	else	25	else