selftests/bpf: Test unhashing kTLS socket after removing from map

When a TCP socket gets inserted into a sockmap, its sk_prot callbacks get
replaced with tcp_bpf callbacks built from regular tcp callbacks. If TLS
gets enabled on the same socket, sk_prot callbacks get replaced once again,
this time with kTLS callbacks built from tcp_bpf callbacks.

Now, we allow removing a socket from a sockmap that has kTLS enabled. After
removal, socket remains with kTLS configured. This is where things things
get tricky.

Since the socket has a set of sk_prot callbacks that are a mix of kTLS and
tcp_bpf callbacks, we need to restore just the tcp_bpf callbacks to the
original ones. At the moment, it comes down to the the unhash operation.

We had a regression recently because tcp_bpf callbacks were not cleared in
this particular scenario of removing a kTLS socket from a sockmap. It got
fixed in commit 4da6a196f93b ("bpf: Sockmap/tls, during free we may call
tcp_bpf_unhash() in loop").

Add a test that triggers the regression so that we don't reintroduce it in
the future.

Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200217121530.754315-4-jakub@cloudflare.com

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

@@ -0,0 +1,123 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2020 Cloudflare
+/*
+ * Tests for sockmap/sockhash holding kTLS sockets.
+ */
+
+#include "test_progs.h"
+
+#define MAX_TEST_NAME 80
+
+static int tcp_server(int family)
+{
+	int err, s;
+
+	s = socket(family, SOCK_STREAM, 0);
+	if (CHECK_FAIL(s == -1)) {
+		perror("socket");
+		return -1;
+	}
+
+	err = listen(s, SOMAXCONN);
+	if (CHECK_FAIL(err)) {
+		perror("listen");
+		return -1;
+	}
+
+	return s;
+}
+
+static int disconnect(int fd)
+{
+	struct sockaddr unspec = { AF_UNSPEC };
+
+	return connect(fd, &unspec, sizeof(unspec));
+}
+
+/* Disconnect (unhash) a kTLS socket after removing it from sockmap. */
+static void test_sockmap_ktls_disconnect_after_delete(int family, int map)
+{
+	struct sockaddr_storage addr = {0};
+	socklen_t len = sizeof(addr);
+	int err, cli, srv, zero = 0;
+
+	srv = tcp_server(family);
+	if (srv == -1)
+		return;
+
+	err = getsockname(srv, (struct sockaddr *)&addr, &len);
+	if (CHECK_FAIL(err)) {
+		perror("getsockopt");
+		goto close_srv;
+	}
+
+	cli = socket(family, SOCK_STREAM, 0);
+	if (CHECK_FAIL(cli == -1)) {
+		perror("socket");
+		goto close_srv;
+	}
+
+	err = connect(cli, (struct sockaddr *)&addr, len);
+	if (CHECK_FAIL(err)) {
+		perror("connect");
+		goto close_cli;
+	}
+
+	err = bpf_map_update_elem(map, &zero, &cli, 0);
+	if (CHECK_FAIL(err)) {
+		perror("bpf_map_update_elem");
+		goto close_cli;
+	}
+
+	err = setsockopt(cli, IPPROTO_TCP, TCP_ULP, "tls", strlen("tls"));
+	if (CHECK_FAIL(err)) {
+		perror("setsockopt(TCP_ULP)");
+		goto close_cli;
+	}
+
+	err = bpf_map_delete_elem(map, &zero);
+	if (CHECK_FAIL(err)) {
+		perror("bpf_map_delete_elem");
+		goto close_cli;
+	}
+
+	err = disconnect(cli);
+	if (CHECK_FAIL(err))
+		perror("disconnect");
+
+close_cli:
+	close(cli);
+close_srv:
+	close(srv);
+}
+
+static void run_tests(int family, enum bpf_map_type map_type)
+{
+	char test_name[MAX_TEST_NAME];
+	int map;
+
+	map = bpf_create_map(map_type, sizeof(int), sizeof(int), 1, 0);
+	if (CHECK_FAIL(map == -1)) {
+		perror("bpf_map_create");
+		return;
+	}
+
+	snprintf(test_name, MAX_TEST_NAME,
+		 "sockmap_ktls disconnect_after_delete %s %s",
+		 family == AF_INET ? "IPv4" : "IPv6",
+		 map_type == BPF_MAP_TYPE_SOCKMAP ? "SOCKMAP" : "SOCKHASH");
+	if (!test__start_subtest(test_name))
+		return;
+
+	test_sockmap_ktls_disconnect_after_delete(family, map);
+
+	close(map);
+}
+
+void test_sockmap_ktls(void)
+{
+	run_tests(AF_INET, BPF_MAP_TYPE_SOCKMAP);
+	run_tests(AF_INET, BPF_MAP_TYPE_SOCKHASH);
+	run_tests(AF_INET6, BPF_MAP_TYPE_SOCKMAP);
+	run_tests(AF_INET6, BPF_MAP_TYPE_SOCKHASH);
+}