bpf: selftest: Add test_btf_skc_cls_ingress

This patch attaches a classifier prog to the ingress filter.
It exercises the following helpers with different socket pointer
types in different logical branches:
1. bpf_sk_release()
2. bpf_sk_assign()
3. bpf_skc_to_tcp_request_sock(), bpf_skc_to_tcp_sock()
4. bpf_tcp_gen_syncookie, bpf_tcp_check_syncookie

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200925000458.3859627-1-kafai@fb.com

tools/testing/selftests/bpf/bpf_tcp_helpers.h

@@ -16,6 +16,7 @@ BPF_PROG(name, args)
 
 struct sock_common {
 	unsigned char	skc_state;
+	__u16		skc_num;
 } __attribute__((preserve_access_index));
 
 enum sk_pacing {
@@ -45,6 +46,10 @@ struct inet_connection_sock {
 	__u64			  icsk_ca_priv[104 / sizeof(__u64)];
 } __attribute__((preserve_access_index));
 
+struct request_sock {
+	struct sock_common		__req_common;
+} __attribute__((preserve_access_index));
+
 struct tcp_sock {
 	struct inet_connection_sock	inet_conn;
 

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

@@ -0,0 +1,234 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Facebook */
+
+#define _GNU_SOURCE
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <sched.h>
+#include <linux/compiler.h>
+#include <bpf/libbpf.h>
+
+#include "network_helpers.h"
+#include "test_progs.h"
+#include "test_btf_skc_cls_ingress.skel.h"
+
+struct test_btf_skc_cls_ingress *skel;
+struct sockaddr_in6 srv_sa6;
+static __u32 duration;
+
+#define PROG_PIN_FILE "/sys/fs/bpf/btf_skc_cls_ingress"
+
+static int write_sysctl(const char *sysctl, const char *value)
+{
+	int fd, err, len;
+
+	fd = open(sysctl, O_WRONLY);
+	if (CHECK(fd == -1, "open sysctl", "open(%s): %s (%d)\n",
+		  sysctl, strerror(errno), errno))
+		return -1;
+
+	len = strlen(value);
+	err = write(fd, value, len);
+	close(fd);
+	if (CHECK(err != len, "write sysctl",
+		  "write(%s, %s, %d): err:%d %s (%d)\n",
+		  sysctl, value, len, err, strerror(errno), errno))
+		return -1;
+
+	return 0;
+}
+
+static int prepare_netns(void)
+{
+	if (CHECK(unshare(CLONE_NEWNET), "create netns",
+		  "unshare(CLONE_NEWNET): %s (%d)",
+		  strerror(errno), errno))
+		return -1;
+
+	if (CHECK(system("ip link set dev lo up"),
+		  "ip link set dev lo up", "failed\n"))
+		return -1;
+
+	if (CHECK(system("tc qdisc add dev lo clsact"),
+		  "tc qdisc add dev lo clsact", "failed\n"))
+		return -1;
+
+	if (CHECK(system("tc filter add dev lo ingress bpf direct-action object-pinned " PROG_PIN_FILE),
+		  "install tc cls-prog at ingress", "failed\n"))
+		return -1;
+
+	/* Ensure 20 bytes options (i.e. in total 40 bytes tcp header) for the
+	 * bpf_tcp_gen_syncookie() helper.
+	 */
+	if (write_sysctl("/proc/sys/net/ipv4/tcp_window_scaling", "1") ||
+	    write_sysctl("/proc/sys/net/ipv4/tcp_timestamps", "1") ||
+	    write_sysctl("/proc/sys/net/ipv4/tcp_sack", "1"))
+		return -1;
+
+	return 0;
+}
+
+static void reset_test(void)
+{
+	memset(&skel->bss->srv_sa6, 0, sizeof(skel->bss->srv_sa6));
+	skel->bss->listen_tp_sport = 0;
+	skel->bss->req_sk_sport = 0;
+	skel->bss->recv_cookie = 0;
+	skel->bss->gen_cookie = 0;
+	skel->bss->linum = 0;
+}
+
+static void print_err_line(void)
+{
+	if (skel->bss->linum)
+		printf("bpf prog error at line %u\n", skel->bss->linum);
+}
+
+static void test_conn(void)
+{
+	int listen_fd = -1, cli_fd = -1, err;
+	socklen_t addrlen = sizeof(srv_sa6);
+	int srv_port;
+
+	if (write_sysctl("/proc/sys/net/ipv4/tcp_syncookies", "1"))
+		return;
+
+	listen_fd = start_server(AF_INET6, SOCK_STREAM, "::1", 0, 0);
+	if (CHECK_FAIL(listen_fd == -1))
+		return;
+
+	err = getsockname(listen_fd, (struct sockaddr *)&srv_sa6, &addrlen);
+	if (CHECK(err, "getsockname(listen_fd)", "err:%d errno:%d\n", err,
+		  errno))
+		goto done;
+	memcpy(&skel->bss->srv_sa6, &srv_sa6, sizeof(srv_sa6));
+	srv_port = ntohs(srv_sa6.sin6_port);
+
+	cli_fd = connect_to_fd(listen_fd, 0);
+	if (CHECK_FAIL(cli_fd == -1))
+		goto done;
+
+	if (CHECK(skel->bss->listen_tp_sport != srv_port ||
+		  skel->bss->req_sk_sport != srv_port,
+		  "Unexpected sk src port",
+		  "listen_tp_sport:%u req_sk_sport:%u expected:%u\n",
+		  skel->bss->listen_tp_sport, skel->bss->req_sk_sport,
+		  srv_port))
+		goto done;
+
+	if (CHECK(skel->bss->gen_cookie || skel->bss->recv_cookie,
+		  "Unexpected syncookie states",
+		  "gen_cookie:%u recv_cookie:%u\n",
+		  skel->bss->gen_cookie, skel->bss->recv_cookie))
+		goto done;
+
+	CHECK(skel->bss->linum, "bpf prog detected error", "at line %u\n",
+	      skel->bss->linum);
+
+done:
+	if (listen_fd != -1)
+		close(listen_fd);
+	if (cli_fd != -1)
+		close(cli_fd);
+}
+
+static void test_syncookie(void)
+{
+	int listen_fd = -1, cli_fd = -1, err;
+	socklen_t addrlen = sizeof(srv_sa6);
+	int srv_port;
+
+	/* Enforce syncookie mode */
+	if (write_sysctl("/proc/sys/net/ipv4/tcp_syncookies", "2"))
+		return;
+
+	listen_fd = start_server(AF_INET6, SOCK_STREAM, "::1", 0, 0);
+	if (CHECK_FAIL(listen_fd == -1))
+		return;
+
+	err = getsockname(listen_fd, (struct sockaddr *)&srv_sa6, &addrlen);
+	if (CHECK(err, "getsockname(listen_fd)", "err:%d errno:%d\n", err,
+		  errno))
+		goto done;
+	memcpy(&skel->bss->srv_sa6, &srv_sa6, sizeof(srv_sa6));
+	srv_port = ntohs(srv_sa6.sin6_port);
+
+	cli_fd = connect_to_fd(listen_fd, 0);
+	if (CHECK_FAIL(cli_fd == -1))
+		goto done;
+
+	if (CHECK(skel->bss->listen_tp_sport != srv_port,
+		  "Unexpected tp src port",
+		  "listen_tp_sport:%u expected:%u\n",
+		  skel->bss->listen_tp_sport, srv_port))
+		goto done;
+
+	if (CHECK(skel->bss->req_sk_sport,
+		  "Unexpected req_sk src port",
+		  "req_sk_sport:%u expected:0\n",
+		   skel->bss->req_sk_sport))
+		goto done;
+
+	if (CHECK(!skel->bss->gen_cookie ||
+		  skel->bss->gen_cookie != skel->bss->recv_cookie,
+		  "Unexpected syncookie states",
+		  "gen_cookie:%u recv_cookie:%u\n",
+		  skel->bss->gen_cookie, skel->bss->recv_cookie))
+		goto done;
+
+	CHECK(skel->bss->linum, "bpf prog detected error", "at line %u\n",
+	      skel->bss->linum);
+
+done:
+	if (listen_fd != -1)
+		close(listen_fd);
+	if (cli_fd != -1)
+		close(cli_fd);
+}
+
+struct test {
+	const char *desc;
+	void (*run)(void);
+};
+
+#define DEF_TEST(name) { #name, test_##name }
+static struct test tests[] = {
+	DEF_TEST(conn),
+	DEF_TEST(syncookie),
+};
+
+void test_btf_skc_cls_ingress(void)
+{
+	int i, err;
+
+	skel = test_btf_skc_cls_ingress__open_and_load();
+	if (CHECK(!skel, "test_btf_skc_cls_ingress__open_and_load", "failed\n"))
+		return;
+
+	err = bpf_program__pin(skel->progs.cls_ingress, PROG_PIN_FILE);
+	if (CHECK(err, "bpf_program__pin",
+		  "cannot pin bpf prog to %s. err:%d\n", PROG_PIN_FILE, err)) {
+		test_btf_skc_cls_ingress__destroy(skel);
+		return;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(tests); i++) {
+		if (!test__start_subtest(tests[i].desc))
+			continue;
+
+		if (prepare_netns())
+			break;
+
+		tests[i].run();
+
+		print_err_line();
+		reset_test();
+	}
+
+	bpf_program__unpin(skel->progs.cls_ingress, PROG_PIN_FILE);
+	test_btf_skc_cls_ingress__destroy(skel);
+}

tools/testing/selftests/bpf/progs/test_btf_skc_cls_ingress.c

@@ -0,0 +1,174 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Facebook */
+
+#include <string.h>
+#include <errno.h>
+#include <netinet/in.h>
+#include <linux/stddef.h>
+#include <linux/bpf.h>
+#include <linux/ipv6.h>
+#include <linux/tcp.h>
+#include <linux/if_ether.h>
+#include <linux/pkt_cls.h>
+
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_endian.h>
+#include "bpf_tcp_helpers.h"
+
+struct sockaddr_in6 srv_sa6 = {};
+__u16 listen_tp_sport = 0;
+__u16 req_sk_sport = 0;
+__u32 recv_cookie = 0;
+__u32 gen_cookie = 0;
+__u32 linum = 0;
+
+#define LOG() ({ if (!linum) linum = __LINE__; })
+
+static void test_syncookie_helper(struct ipv6hdr *ip6h, struct tcphdr *th,
+				  struct tcp_sock *tp,
+				  struct __sk_buff *skb)
+{
+	if (th->syn) {
+		__s64 mss_cookie;
+		void *data_end;
+
+		data_end = (void *)(long)(skb->data_end);
+
+		if (th->doff * 4 != 40) {
+			LOG();
+			return;
+		}
+
+		if ((void *)th + 40 > data_end) {
+			LOG();
+			return;
+		}
+
+		mss_cookie = bpf_tcp_gen_syncookie(tp, ip6h, sizeof(*ip6h),
+						   th, 40);
+		if (mss_cookie < 0) {
+			if (mss_cookie != -ENOENT)
+				LOG();
+		} else {
+			gen_cookie = (__u32)mss_cookie;
+		}
+	} else if (gen_cookie) {
+		/* It was in cookie mode */
+		int ret = bpf_tcp_check_syncookie(tp, ip6h, sizeof(*ip6h),
+						  th, sizeof(*th));
+
+		if (ret < 0) {
+			if (ret != -ENOENT)
+				LOG();
+		} else {
+			recv_cookie = bpf_ntohl(th->ack_seq) - 1;
+		}
+	}
+}
+
+static int handle_ip6_tcp(struct ipv6hdr *ip6h, struct __sk_buff *skb)
+{
+	struct bpf_sock_tuple *tuple;
+	struct bpf_sock *bpf_skc;
+	unsigned int tuple_len;
+	struct tcphdr *th;
+	void *data_end;
+
+	data_end = (void *)(long)(skb->data_end);
+
+	th = (struct tcphdr *)(ip6h + 1);
+	if (th + 1 > data_end)
+		return TC_ACT_OK;
+
+	/* Is it the testing traffic? */
+	if (th->dest != srv_sa6.sin6_port)
+		return TC_ACT_OK;
+
+	tuple_len = sizeof(tuple->ipv6);
+	tuple = (struct bpf_sock_tuple *)&ip6h->saddr;
+	if ((void *)tuple + tuple_len > data_end) {
+		LOG();
+		return TC_ACT_OK;
+	}
+
+	bpf_skc = bpf_skc_lookup_tcp(skb, tuple, tuple_len,
+				     BPF_F_CURRENT_NETNS, 0);
+	if (!bpf_skc) {
+		LOG();
+		return TC_ACT_OK;
+	}
+
+	if (bpf_skc->state == BPF_TCP_NEW_SYN_RECV) {
+		struct request_sock *req_sk;
+
+		req_sk = (struct request_sock *)bpf_skc_to_tcp_request_sock(bpf_skc);
+		if (!req_sk) {
+			LOG();
+			goto release;
+		}
+
+		if (bpf_sk_assign(skb, req_sk, 0)) {
+			LOG();
+			goto release;
+		}
+
+		req_sk_sport = req_sk->__req_common.skc_num;
+
+		bpf_sk_release(req_sk);
+		return TC_ACT_OK;
+	} else if (bpf_skc->state == BPF_TCP_LISTEN) {
+		struct tcp_sock *tp;
+
+		tp = bpf_skc_to_tcp_sock(bpf_skc);
+		if (!tp) {
+			LOG();
+			goto release;
+		}
+
+		if (bpf_sk_assign(skb, tp, 0)) {
+			LOG();
+			goto release;
+		}
+
+		listen_tp_sport = tp->inet_conn.icsk_inet.sk.__sk_common.skc_num;
+
+		test_syncookie_helper(ip6h, th, tp, skb);
+		bpf_sk_release(tp);
+		return TC_ACT_OK;
+	}
+
+	if (bpf_sk_assign(skb, bpf_skc, 0))
+		LOG();
+
+release:
+	bpf_sk_release(bpf_skc);
+	return TC_ACT_OK;
+}
+
+SEC("classifier/ingress")
+int cls_ingress(struct __sk_buff *skb)
+{
+	struct ipv6hdr *ip6h;
+	struct ethhdr *eth;
+	void *data_end;
+
+	data_end = (void *)(long)(skb->data_end);
+
+	eth = (struct ethhdr *)(long)(skb->data);
+	if (eth + 1 > data_end)
+		return TC_ACT_OK;
+
+	if (eth->h_proto != bpf_htons(ETH_P_IPV6))
+		return TC_ACT_OK;
+
+	ip6h = (struct ipv6hdr *)(eth + 1);
+	if (ip6h + 1 > data_end)
+		return TC_ACT_OK;
+
+	if (ip6h->nexthdr == IPPROTO_TCP)
+		return handle_ip6_tcp(ip6h, skb);
+
+	return TC_ACT_OK;
+}
+
+char _license[] SEC("license") = "GPL";