1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Check if we can fully utilize 4-tuples for connect().
4  *
5  * Rules to bind sockets to the same port when all ephemeral ports are
6  * exhausted.
7  *
8  *   1. if there are TCP_LISTEN sockets on the port, fail to bind.
9  *   2. if there are sockets without SO_REUSEADDR, fail to bind.
10  *   3. if SO_REUSEADDR is disabled, fail to bind.
11  *   4. if SO_REUSEADDR is enabled and SO_REUSEPORT is disabled,
12  *        succeed to bind.
13  *   5. if SO_REUSEADDR and SO_REUSEPORT are enabled and
14  *        there is no socket having the both options and the same EUID,
15  *        succeed to bind.
16  *   6. fail to bind.
17  *
18  * Author: Kuniyuki Iwashima <kuniyu@amazon.co.jp>
19  */
20 #include <arpa/inet.h>
21 #include <netinet/in.h>
22 #include <sys/socket.h>
23 #include <sys/types.h>
24 #include <unistd.h>
25 #include "../kselftest_harness.h"
26 
27 struct reuse_opts {
28 	int reuseaddr[2];
29 	int reuseport[2];
30 };
31 
32 struct reuse_opts unreusable_opts[12] = {
33 	{0, 0, 0, 0},
34 	{0, 0, 0, 1},
35 	{0, 0, 1, 0},
36 	{0, 0, 1, 1},
37 	{0, 1, 0, 0},
38 	{0, 1, 0, 1},
39 	{0, 1, 1, 0},
40 	{0, 1, 1, 1},
41 	{1, 0, 0, 0},
42 	{1, 0, 0, 1},
43 	{1, 0, 1, 0},
44 	{1, 0, 1, 1},
45 };
46 
47 struct reuse_opts reusable_opts[4] = {
48 	{1, 1, 0, 0},
49 	{1, 1, 0, 1},
50 	{1, 1, 1, 0},
51 	{1, 1, 1, 1},
52 };
53 
54 int bind_port(struct __test_metadata *_metadata, int reuseaddr, int reuseport)
55 {
56 	struct sockaddr_in local_addr;
57 	int len = sizeof(local_addr);
58 	int fd, ret;
59 
60 	fd = socket(AF_INET, SOCK_STREAM, 0);
61 	ASSERT_NE(-1, fd) TH_LOG("failed to open socket.");
62 
63 	ret = setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &reuseaddr, sizeof(int));
64 	ASSERT_EQ(0, ret) TH_LOG("failed to setsockopt: SO_REUSEADDR.");
65 
66 	ret = setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &reuseport, sizeof(int));
67 	ASSERT_EQ(0, ret) TH_LOG("failed to setsockopt: SO_REUSEPORT.");
68 
69 	local_addr.sin_family = AF_INET;
70 	local_addr.sin_addr.s_addr = inet_addr("127.0.0.1");
71 	local_addr.sin_port = 0;
72 
73 	if (bind(fd, (struct sockaddr *)&local_addr, len) == -1) {
74 		close(fd);
75 		return -1;
76 	}
77 
78 	return fd;
79 }
80 
81 TEST(reuseaddr_ports_exhausted_unreusable)
82 {
83 	struct reuse_opts *opts;
84 	int i, j, fd[2];
85 
86 	for (i = 0; i < 12; i++) {
87 		opts = &unreusable_opts[i];
88 
89 		for (j = 0; j < 2; j++)
90 			fd[j] = bind_port(_metadata, opts->reuseaddr[j], opts->reuseport[j]);
91 
92 		ASSERT_NE(-1, fd[0]) TH_LOG("failed to bind.");
93 		EXPECT_EQ(-1, fd[1]) TH_LOG("should fail to bind.");
94 
95 		for (j = 0; j < 2; j++)
96 			if (fd[j] != -1)
97 				close(fd[j]);
98 	}
99 }
100 
101 TEST(reuseaddr_ports_exhausted_reusable_same_euid)
102 {
103 	struct reuse_opts *opts;
104 	int i, j, fd[2];
105 
106 	for (i = 0; i < 4; i++) {
107 		opts = &reusable_opts[i];
108 
109 		for (j = 0; j < 2; j++)
110 			fd[j] = bind_port(_metadata, opts->reuseaddr[j], opts->reuseport[j]);
111 
112 		ASSERT_NE(-1, fd[0]) TH_LOG("failed to bind.");
113 
114 		if (opts->reuseport[0] && opts->reuseport[1]) {
115 			EXPECT_EQ(-1, fd[1]) TH_LOG("should fail to bind because both sockets succeed to be listened.");
116 		} else {
117 			EXPECT_NE(-1, fd[1]) TH_LOG("should succeed to bind to connect to different destinations.");
118 		}
119 
120 		for (j = 0; j < 2; j++)
121 			if (fd[j] != -1)
122 				close(fd[j]);
123 	}
124 }
125 
126 TEST(reuseaddr_ports_exhausted_reusable_different_euid)
127 {
128 	struct reuse_opts *opts;
129 	int i, j, ret, fd[2];
130 	uid_t euid[2] = {10, 20};
131 
132 	for (i = 0; i < 4; i++) {
133 		opts = &reusable_opts[i];
134 
135 		for (j = 0; j < 2; j++) {
136 			ret = seteuid(euid[j]);
137 			ASSERT_EQ(0, ret) TH_LOG("failed to seteuid: %d.", euid[j]);
138 
139 			fd[j] = bind_port(_metadata, opts->reuseaddr[j], opts->reuseport[j]);
140 
141 			ret = seteuid(0);
142 			ASSERT_EQ(0, ret) TH_LOG("failed to seteuid: 0.");
143 		}
144 
145 		ASSERT_NE(-1, fd[0]) TH_LOG("failed to bind.");
146 		EXPECT_NE(-1, fd[1]) TH_LOG("should succeed to bind because one socket can be bound in each euid.");
147 
148 		if (fd[1] != -1) {
149 			ret = listen(fd[0], 5);
150 			ASSERT_EQ(0, ret) TH_LOG("failed to listen.");
151 
152 			ret = listen(fd[1], 5);
153 			EXPECT_EQ(-1, ret) TH_LOG("should fail to listen because only one uid reserves the port in TCP_LISTEN.");
154 		}
155 
156 		for (j = 0; j < 2; j++)
157 			if (fd[j] != -1)
158 				close(fd[j]);
159 	}
160 }
161 
162 TEST_HARNESS_MAIN
163