There is no lwt selftest for BPF_REROUTE yet. Add test cases for both normal and abnormal situations. The abnormal situation is set up with an fq qdisc on the reroute target device. Without proper fixes, BPF_REROUTE to this device and overflow this qdisc queue limit (to trigger a drop) would panic the kernel, so please run the test in a VM for safety.
Signed-off-by: Yan Zhai yan@cloudflare.com --- .../selftests/bpf/prog_tests/lwt_reroute.c | 256 ++++++++++++++++++ .../selftests/bpf/progs/test_lwt_reroute.c | 36 +++ 2 files changed, 292 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/lwt_reroute.c create mode 100644 tools/testing/selftests/bpf/progs/test_lwt_reroute.c
diff --git a/tools/testing/selftests/bpf/prog_tests/lwt_reroute.c b/tools/testing/selftests/bpf/prog_tests/lwt_reroute.c new file mode 100644 index 000000000000..e5fa5451bd2c --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/lwt_reroute.c @@ -0,0 +1,256 @@ +// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause + +/* + * Test suite of lwt BPF programs that reroutes packets + * The file tests focus not only if these programs work as expected normally, + * but also if they can handle abnormal situations gracefully. This test + * suite currently only covers lwt_xmit hook. lwt_in tests have not been + * implemented. + * + * WARNING + * ------- + * This test suite can crash the kernel, thus should be run in a VM. + * + * Setup: + * --------- + * all tests are performed in a single netns. A lwt encap route is setup for + * each subtest: + * + * ip route add 10.0.0.0/24 encap bpf xmit <obj> sec "<section_N>" dev link_err + * + * Here <obj> is statically defined to test_lwt_reroute.bpf.o, and it contains + * a single test program entry. This program sets packet mark by last byte of + * the IPv4 daddr. For example, a packet going to 1.2.3.4 will receive a skb + * mark 4. A packet will only be marked once, and IP x.x.x.0 will be skipped + * to avoid route loop. We didn't use generated BPF skeleton since the + * attachment for lwt programs are not supported by libbpf yet. + * + * The test program will bring up a tun device, and sets up the following + * routes: + * + * ip rule add pref 100 from all fwmark <tun_index> lookup 100 + * ip route add table 100 default dev tun0 + * + * For normal testing, a ping command is running in the test netns: + * + * ping 10.0.0.<tun_index> -c 1 -w 1 -s 100 + * + * For abnormal testing, fq is used as the qdisc of the tun device. Then a UDP + * socket will try to overflow the fq queue and trigger qdisc drop error. + * + * Scenarios: + * -------------------------------- + * 1. Reroute to a running tun device + * 2. Reroute to a device where qdisc drop + * + * For case 1, ping packets should be received by the tun device. + * + * For case 2, force UDP packets to overflow fq limit. As long as kernel + * is not crashed, it is considered successful. + */ +#include "lwt_helpers.h" +#include "network_helpers.h" +#include <linux/net_tstamp.h> + +#define BPF_OBJECT "test_lwt_reroute.bpf.o" +#define LOCAL_SRC "10.0.0.1" +#define TEST_CIDR "10.0.0.0/24" +#define XMIT_HOOK "xmit" +#define XMIT_SECTION "lwt_xmit" +#define NSEC_PER_SEC 1000000000ULL + +/* send a ping to be rerouted to the target device */ +static void ping_once(const char *ip) +{ + /* We won't get a reply. Don't fail here */ + SYS_NOFAIL("ping %s -c1 -w1 -s %d >/dev/null 2>&1", + ip, ICMP_PAYLOAD_SIZE); +} + +/* Send snd_target UDP packets to overflow the fq queue and trigger qdisc drop + * error. This is done via TX tstamp to force buffering delayed packets. + */ +static int overflow_fq(int snd_target, const char *target_ip) +{ + struct sockaddr_in addr = { + .sin_family = AF_INET, + .sin_port = htons(1234), + }; + + char data_buf[8]; /* only #pkts matter, so use a random small buffer */ + char control_buf[CMSG_SPACE(sizeof(uint64_t))]; + struct iovec iov = { + .iov_base = data_buf, + .iov_len = sizeof(data_buf), + }; + int err = -1; + int s = -1; + struct sock_txtime txtime_on = { + .clockid = CLOCK_MONOTONIC, + .flags = 0, + }; + struct msghdr msg = { + .msg_name = &addr, + .msg_namelen = sizeof(addr), + .msg_control = control_buf, + .msg_controllen = sizeof(control_buf), + .msg_iovlen = 1, + .msg_iov = &iov, + }; + struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg); + + memset(data_buf, 0, sizeof(data_buf)); + + s = socket(AF_INET, SOCK_DGRAM, 0); + if (!ASSERT_GE(s, 0, "socket")) + goto out; + + err = setsockopt(s, SOL_SOCKET, SO_TXTIME, &txtime_on, sizeof(txtime_on)); + if (!ASSERT_OK(err, "setsockopt(SO_TXTIME)")) + goto out; + + err = inet_pton(AF_INET, target_ip, &addr.sin_addr); + if (!ASSERT_EQ(err, 1, "inet_pton")) + goto out; + + while (snd_target > 0) { + struct timespec now; + + memset(control_buf, 0, sizeof(control_buf)); + cmsg->cmsg_type = SCM_TXTIME; + cmsg->cmsg_level = SOL_SOCKET; + cmsg->cmsg_len = CMSG_LEN(sizeof(uint64_t)); + + err = clock_gettime(CLOCK_MONOTONIC, &now); + if (!ASSERT_OK(err, "clock_gettime(CLOCK_MONOTONIC)")) { + err = -1; + goto out; + } + + *(uint64_t *)CMSG_DATA(cmsg) = (now.tv_nsec + 1) * NSEC_PER_SEC + + now.tv_nsec; + + /* we will intentionally send more than fq limit, so ignore + * the error here. + */ + sendmsg(s, &msg, MSG_NOSIGNAL); + snd_target--; + } + + /* no kernel crash so far is considered success */ + err = 0; + +out: + if (s >= 0) + close(s); + + return err; +} + +static int setup(const char *tun_dev) +{ + int target_index = -1; + int tap_fd = -1; + + tap_fd = open_tuntap(tun_dev, false); + if (!ASSERT_GE(tap_fd, 0, "open_tun")) + return -1; + + target_index = if_nametoindex(tun_dev); + if (!ASSERT_GE(target_index, 0, "if_nametoindex")) + return -1; + + SYS(fail, "ip link add link_err type dummy"); + SYS(fail, "ip link set lo up"); + SYS(fail, "ip addr add dev lo " LOCAL_SRC "/32"); + SYS(fail, "ip link set link_err up"); + SYS(fail, "ip link set %s up", tun_dev); + + SYS(fail, "ip route add %s dev link_err encap bpf xmit obj %s sec lwt_xmit", + TEST_CIDR, BPF_OBJECT); + + SYS(fail, "ip rule add pref 100 from all fwmark %d lookup 100", + target_index); + SYS(fail, "ip route add t 100 default dev %s", tun_dev); + + return tap_fd; + +fail: + if (tap_fd >= 0) + close(tap_fd); + return -1; +} + +static void test_lwt_reroute_normal_xmit(void) +{ + const char *tun_dev = "tun0"; + int tun_fd = -1; + int ifindex = -1; + char ip[256]; + struct timeval timeo = { + .tv_sec = 0, + .tv_usec = 250000, + }; + + tun_fd = setup(tun_dev); + if (!ASSERT_GE(tun_fd, 0, "setup_reroute")) + return; + + ifindex = if_nametoindex(tun_dev); + snprintf(ip, 256, "10.0.0.%d", ifindex); + + /* ping packets should be received by the tun device */ + ping_once(ip); + + if (!ASSERT_EQ(wait_for_packet(tun_fd, __expect_icmp_ipv4, &timeo), 1, + "wait_for_packet")) + log_err("%s xmit", __func__); +} + +/* + * Test the failure case when the skb is dropped at the qdisc. This is a + * regression prevention at the xmit hook only. + */ +static void test_lwt_reroute_qdisc_dropped(void) +{ + const char *tun_dev = "tun0"; + int tun_fd = -1; + int ifindex = -1; + char ip[256]; + + tun_fd = setup(tun_dev); + if (!ASSERT_GE(tun_fd, 0, "setup_reroute")) + goto fail; + + SYS(fail, "tc qdisc replace dev %s root fq limit 5 flow_limit 5", tun_dev); + + ifindex = if_nametoindex(tun_dev); + snprintf(ip, 256, "10.0.0.%d", ifindex); + ASSERT_EQ(overflow_fq(10, ip), 0, "overflow_fq"); + +fail: + if (tun_fd >= 0) + close(tun_fd); +} + +static void *test_lwt_reroute_run(void *arg) +{ + netns_delete(); + RUN_TEST(lwt_reroute_normal_xmit); + RUN_TEST(lwt_reroute_qdisc_dropped); + return NULL; +} + +void test_lwt_reroute(void) +{ + pthread_t test_thread; + int err; + + /* Run the tests in their own thread to isolate the namespace changes + * so they do not affect the environment of other tests. + * (specifically needed because of unshare(CLONE_NEWNS) in open_netns()) + */ + err = pthread_create(&test_thread, NULL, &test_lwt_reroute_run, NULL); + if (ASSERT_OK(err, "pthread_create")) + ASSERT_OK(pthread_join(test_thread, NULL), "pthread_join"); +} diff --git a/tools/testing/selftests/bpf/progs/test_lwt_reroute.c b/tools/testing/selftests/bpf/progs/test_lwt_reroute.c new file mode 100644 index 000000000000..1dc64351929c --- /dev/null +++ b/tools/testing/selftests/bpf/progs/test_lwt_reroute.c @@ -0,0 +1,36 @@ +// SPDX-License-Identifier: GPL-2.0 +#include <inttypes.h> +#include <linux/bpf.h> +#include <bpf/bpf_endian.h> +#include <bpf/bpf_helpers.h> +#include <linux/if_ether.h> +#include <linux/ip.h> + +/* This function extracts the last byte of the daddr, and uses it + * as output dev index. + */ +SEC("lwt_xmit") +int test_lwt_reroute(struct __sk_buff *skb) +{ + struct iphdr *iph = NULL; + void *start = (void *)(long)skb->data; + void *end = (void *)(long)skb->data_end; + + /* set mark at most once */ + if (skb->mark != 0) + return BPF_OK; + + if (start + sizeof(*iph) > end) + return BPF_DROP; + + iph = (struct iphdr *)start; + skb->mark = bpf_ntohl(iph->daddr) & 0xff; + + /* do not reroute x.x.x.0 packets */ + if (skb->mark == 0) + return BPF_OK; + + return BPF_LWT_REROUTE; +} + +char _license[] SEC("license") = "GPL";