1 // SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
2
3 /*
4 * Test suite of lwt BPF programs that reroutes packets
5 * The file tests focus not only if these programs work as expected normally,
6 * but also if they can handle abnormal situations gracefully. This test
7 * suite currently only covers lwt_xmit hook. lwt_in tests have not been
8 * implemented.
9 *
10 * WARNING
11 * -------
12 * This test suite can crash the kernel, thus should be run in a VM.
13 *
14 * Setup:
15 * ---------
16 * all tests are performed in a single netns. A lwt encap route is setup for
17 * each subtest:
18 *
19 * ip route add 10.0.0.0/24 encap bpf xmit <obj> sec "<section_N>" dev link_err
20 *
21 * Here <obj> is statically defined to test_lwt_reroute.bpf.o, and it contains
22 * a single test program entry. This program sets packet mark by last byte of
23 * the IPv4 daddr. For example, a packet going to 1.2.3.4 will receive a skb
24 * mark 4. A packet will only be marked once, and IP x.x.x.0 will be skipped
25 * to avoid route loop. We didn't use generated BPF skeleton since the
26 * attachment for lwt programs are not supported by libbpf yet.
27 *
28 * The test program will bring up a tun device, and sets up the following
29 * routes:
30 *
31 * ip rule add pref 100 from all fwmark <tun_index> lookup 100
32 * ip route add table 100 default dev tun0
33 *
34 * For normal testing, a ping command is running in the test netns:
35 *
36 * ping 10.0.0.<tun_index> -c 1 -w 1 -s 100
37 *
38 * For abnormal testing, fq is used as the qdisc of the tun device. Then a UDP
39 * socket will try to overflow the fq queue and trigger qdisc drop error.
40 *
41 * Scenarios:
42 * --------------------------------
43 * 1. Reroute to a running tun device
44 * 2. Reroute to a device where qdisc drop
45 *
46 * For case 1, ping packets should be received by the tun device.
47 *
48 * For case 2, force UDP packets to overflow fq limit. As long as kernel
49 * is not crashed, it is considered successful.
50 */
51 #define NETNS "ns_lwt_reroute"
52 #include <netinet/in.h>
53 #include "lwt_helpers.h"
54 #include "network_helpers.h"
55 #include <linux/net_tstamp.h>
56
57 #define BPF_OBJECT "test_lwt_reroute.bpf.o"
58 #define LOCAL_SRC "10.0.0.1"
59 #define TEST_CIDR "10.0.0.0/24"
60 #define XMIT_HOOK "xmit"
61 #define XMIT_SECTION "lwt_xmit"
62 #define NSEC_PER_SEC 1000000000ULL
63
64 /* send a ping to be rerouted to the target device */
65 static void ping_once(const char *ip)
66 {
67 /* We won't get a reply. Don't fail here */
68 SYS_NOFAIL("ping %s -c1 -W1 -s %d",
69 ip, ICMP_PAYLOAD_SIZE);
70 }
71
72 /* Send snd_target UDP packets to overflow the fq queue and trigger qdisc drop
73 * error. This is done via TX tstamp to force buffering delayed packets.
74 */
75 static int overflow_fq(int snd_target, const char *target_ip)
76 {
77 struct sockaddr_in addr = {
78 .sin_family = AF_INET,
79 .sin_port = htons(1234),
80 };
81
82 char data_buf[8]; /* only #pkts matter, so use a random small buffer */
83 char control_buf[CMSG_SPACE(sizeof(uint64_t))];
84 struct iovec iov = {
85 .iov_base = data_buf,
86 .iov_len = sizeof(data_buf),
87 };
88 int err = -1;
89 int s = -1;
90 struct sock_txtime txtime_on = {
91 .clockid = CLOCK_MONOTONIC,
92 .flags = 0,
93 };
94 struct msghdr msg = {
95 .msg_name = &addr,
96 .msg_namelen = sizeof(addr),
97 .msg_control = control_buf,
98 .msg_controllen = sizeof(control_buf),
99 .msg_iovlen = 1,
100 .msg_iov = &iov,
101 };
102 struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
103
104 memset(data_buf, 0, sizeof(data_buf));
105
106 s = socket(AF_INET, SOCK_DGRAM, 0);
107 if (!ASSERT_GE(s, 0, "socket"))
108 goto out;
109
110 err = setsockopt(s, SOL_SOCKET, SO_TXTIME, &txtime_on, sizeof(txtime_on));
111 if (!ASSERT_OK(err, "setsockopt(SO_TXTIME)"))
112 goto out;
113
114 err = inet_pton(AF_INET, target_ip, &addr.sin_addr);
115 if (!ASSERT_EQ(err, 1, "inet_pton"))
116 goto out;
117
118 while (snd_target > 0) {
119 struct timespec now;
120
121 memset(control_buf, 0, sizeof(control_buf));
122 cmsg->cmsg_type = SCM_TXTIME;
123 cmsg->cmsg_level = SOL_SOCKET;
124 cmsg->cmsg_len = CMSG_LEN(sizeof(uint64_t));
125
126 err = clock_gettime(CLOCK_MONOTONIC, &now);
127 if (!ASSERT_OK(err, "clock_gettime(CLOCK_MONOTONIC)")) {
128 err = -1;
129 goto out;
130 }
131
132 *(uint64_t *)CMSG_DATA(cmsg) = (now.tv_nsec + 1) * NSEC_PER_SEC +
133 now.tv_nsec;
134
135 /* we will intentionally send more than fq limit, so ignore
136 * the error here.
137 */
138 sendmsg(s, &msg, MSG_NOSIGNAL);
139 snd_target--;
140 }
141
142 /* no kernel crash so far is considered success */
143 err = 0;
144
145 out:
146 if (s >= 0)
147 close(s);
148
149 return err;
150 }
151
152 static int setup(const char *tun_dev)
153 {
154 int target_index = -1;
155 int tap_fd = -1;
156
157 tap_fd = open_tuntap(tun_dev, false);
158 if (!ASSERT_GE(tap_fd, 0, "open_tun"))
159 return -1;
160
161 target_index = if_nametoindex(tun_dev);
162 if (!ASSERT_GE(target_index, 0, "if_nametoindex"))
163 return -1;
164
165 SYS(fail, "ip link add link_err type dummy");
166 SYS(fail, "ip link set lo up");
167 SYS(fail, "ip addr add dev lo " LOCAL_SRC "/32");
168 SYS(fail, "ip link set link_err up");
169 SYS(fail, "ip link set %s up", tun_dev);
170
171 SYS(fail, "ip route add %s dev link_err encap bpf xmit obj %s sec lwt_xmit",
172 TEST_CIDR, BPF_OBJECT);
173
174 SYS(fail, "ip rule add pref 100 from all fwmark %d lookup 100",
175 target_index);
176 SYS(fail, "ip route add t 100 default dev %s", tun_dev);
177
178 return tap_fd;
179
180 fail:
181 if (tap_fd >= 0)
182 close(tap_fd);
183 return -1;
184 }
185
186 static void test_lwt_reroute_normal_xmit(void)
187 {
188 const char *tun_dev = "tun0";
189 int tun_fd = -1;
190 int ifindex = -1;
191 char ip[256];
192 struct timeval timeo = {
193 .tv_sec = 0,
194 .tv_usec = 250000,
195 };
196
197 tun_fd = setup(tun_dev);
198 if (!ASSERT_GE(tun_fd, 0, "setup_reroute"))
199 return;
200
201 ifindex = if_nametoindex(tun_dev);
202 if (!ASSERT_GE(ifindex, 0, "if_nametoindex"))
203 return;
204
205 snprintf(ip, 256, "10.0.0.%d", ifindex);
206
207 /* ping packets should be received by the tun device */
208 ping_once(ip);
209
210 if (!ASSERT_EQ(wait_for_packet(tun_fd, __expect_icmp_ipv4, &timeo), 1,
211 "wait_for_packet"))
212 log_err("%s xmit", __func__);
213 }
214
215 /*
216 * Test the failure case when the skb is dropped at the qdisc. This is a
217 * regression prevention at the xmit hook only.
218 */
219 static void test_lwt_reroute_qdisc_dropped(void)
220 {
221 const char *tun_dev = "tun0";
222 int tun_fd = -1;
223 int ifindex = -1;
224 char ip[256];
225
226 tun_fd = setup(tun_dev);
227 if (!ASSERT_GE(tun_fd, 0, "setup_reroute"))
228 goto fail;
229
230 SYS(fail, "tc qdisc replace dev %s root fq limit 5 flow_limit 5", tun_dev);
231
232 ifindex = if_nametoindex(tun_dev);
233 if (!ASSERT_GE(ifindex, 0, "if_nametoindex"))
234 return;
235
236 snprintf(ip, 256, "10.0.0.%d", ifindex);
237 ASSERT_EQ(overflow_fq(10, ip), 0, "overflow_fq");
238
239 fail:
240 if (tun_fd >= 0)
241 close(tun_fd);
242 }
243
244 static void *test_lwt_reroute_run(void *arg)
245 {
246 netns_delete();
247 RUN_TEST(lwt_reroute_normal_xmit);
248 RUN_TEST(lwt_reroute_qdisc_dropped);
249 return NULL;
250 }
251
252 void test_lwt_reroute(void)
253 {
254 pthread_t test_thread;
255 int err;
256
257 /* Run the tests in their own thread to isolate the namespace changes
258 * so they do not affect the environment of other tests.
259 * (specifically needed because of unshare(CLONE_NEWNS) in open_netns())
260 */
261 err = pthread_create(&test_thread, NULL, &test_lwt_reroute_run, NULL);
262 if (ASSERT_OK(err, "pthread_create"))
263 ASSERT_OK(pthread_join(test_thread, NULL), "pthread_join");
264 }
265
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