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

@@ -50,6 +50,7 @@ · 49 unmodified lines
50	50	#include <linux/filter.h>
51	51	#include <linux/bpf.h>
52	52	#include <linux/if_packet.h>
	53	+#include <net/if.h>
53	54	#include <net/ethernet.h>
54	55	#include <netinet/ip.h>
55	56	#include <netinet/udp.h>
@@ -73,14 +74,29 @@ · 17 unmodified lines
73	74	* @return -1 if mode is bad, a valid socket otherwise */
74	75	static int sock_fanout_open(uint16_t typeflags, uint16_t group_id)
75	76	{
	77	+ struct sockaddr_ll addr = {0};
76	78	int fd, val;
77	79
78		− fd = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_IP));
	80	+ fd = socket(PF_PACKET, SOCK_RAW, 0);
79	81	if (fd < 0) {
80	82	perror("socket packet");
81	83	exit(1);
82	84	}
83	85
	86	+ pair_udp_setfilter(fd);
	87	+
	88	+ addr.sll_family = AF_PACKET;
	89	+ addr.sll_protocol = htons(ETH_P_IP);
	90	+ addr.sll_ifindex = if_nametoindex("lo");
	91	+ if (addr.sll_ifindex == 0) {
	92	+ perror("if_nametoindex");
	93	+ exit(1);
	94	+ }
	95	+ if (bind(fd, (void *) &addr, sizeof(addr))) {
	96	+ perror("bind packet");
	97	+ exit(1);
	98	+ }
	99	+
84	100	val = (((int) typeflags) << 16) \| group_id;
85	101	if (setsockopt(fd, SOL_PACKET, PACKET_FANOUT, &val, sizeof(val))) {
86	102	if (close(fd)) {
@@ -90,7 +106,6 @@ static int sock_fanout_open(uint16_t typeflags, uint16_t group_id) · 3 unmodified lines
90	106	return -1;
91	107	}
92	108
93		− pair_udp_setfilter(fd);
94	109	return fd;
95	110	}
96	111
@@ -229,7 +244,7 @@ static int sock_fanout_read(int fds[], char *rings[], const int expect[]) · 132 unmodified lines
229	244
230	245	if ((!(ret[0] == expect[0] && ret[1] == expect[1])) &&
231	246	(!(ret[0] == expect[1] && ret[1] == expect[0]))) {
232		− fprintf(stderr, "ERROR: incorrect queue lengths\n");
	247	+ fprintf(stderr, "warning: incorrect queue lengths\n");
233	248	return 1;
234	249	}
235	250
@@ -348,7 +363,8 @@ static int test_datapath(uint16_t typeflags, int port_off, · 112 unmodified lines
348	363	uint8_t type = typeflags & 0xFF;
349	364	int fds[2], fds_udp[2][2], ret;
350	365
351		− fprintf(stderr, "test: datapath 0x%hx\n", typeflags);
	366	+ fprintf(stderr, "\ntest: datapath 0x%hx ports %hu,%hu\n",
	367	+ typeflags, PORT_BASE, PORT_BASE + port_off);
352	368
353	369	fds[0] = sock_fanout_open(typeflags, 0);
354	370	fds[1] = sock_fanout_open(typeflags, 0);
@@ -419,7 +435,7 @@ int main(int argc, char **argv) · 64 unmodified lines
419	435	const int expect_cpu1[2][2] = { { 0, 20 }, { 0, 20 } };
420	436	const int expect_bpf[2][2] = { { 15, 5 }, { 15, 20 } };
421	437	const int expect_uniqueid[2][2] = { { 20, 20}, { 20, 20 } };
422		− int port_off = 2, tries = 5, ret;
	438	+ int port_off = 2, tries = 20, ret;
423	439
424	440	test_control_single();
425	441	test_control_group();
@@ -428,10 +444,14 @@ int main(int argc, char **argv) · 2 unmodified lines
428	444	/* find a set of ports that do not collide onto the same socket */
429	445	ret = test_datapath(PACKET_FANOUT_HASH, port_off,
430	446	expect_hash[0], expect_hash[1]);
431		− while (ret && tries--) {
	447	+ while (ret) {
432	448	fprintf(stderr, "info: trying alternate ports (%d)\n", tries);
433	449	ret = test_datapath(PACKET_FANOUT_HASH, ++port_off,
434	450	expect_hash[0], expect_hash[1]);
	451	+ if (!--tries) {
	452	+ fprintf(stderr, "too many collisions\n");
	453	+ return 1;
	454	+ }
435	455	}
436	456
437	457	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	9	echo "--------------------"
10	10	echo "running psock_fanout test"
11	11	echo "--------------------"
12		−./psock_fanout
	12	+./in_netns.sh ./psock_fanout
13	13	if [ $? -ne 0 ]; then
14	14	echo "[FAIL]"
15	15	else
@@ -19,7 +19,7 @@ fi · 3 unmodified lines
19	19	echo "--------------------"
20	20	echo "running psock_tpacket test"
21	21	echo "--------------------"
22		−./psock_tpacket
	22	+./in_netns.sh ./psock_tpacket
23	23	if [ $? -ne 0 ]; then
24	24	echo "[FAIL]"
25	25	else