1 /*
2 * SPDX-License-Identifier: BSD-2-Clause
3 *
4 * Copyright (c) 2025 Klara, Inc.
5 */
6
7 /*
8 * A program to demonstrate the effects of the net.inet.tcp.bind_all_fibs and
9 * net.inet.udp.bind_all_fibs sysctls when they are set to 0.
10 *
11 * The program accepts TCP connections (default) or UDP datagrams (-u flag) and
12 * prints the FIB on which they were received, then discards them. If -a is
13 * specific, the program accepts data from all FIBs, otherwise it only accepts
14 * data from the FIB specified by the -f option.
15 */
16
17 #include <sys/event.h>
18 #include <sys/socket.h>
19 #include <sys/sysctl.h>
20
21 #include <netinet/in.h>
22
23 #include <err.h>
24 #include <netdb.h>
25 #include <stdbool.h>
26 #include <stdio.h>
27 #include <stdlib.h>
28 #include <string.h>
29 #include <unistd.h>
30
31 struct sink_softc {
32 struct sockaddr_storage ss;
33 enum { SINK_TCP, SINK_UDP } type;
34 int nfibs;
35 int kq;
36 int *fds;
37 };
38
39 static void _Noreturn
usage(void)40 usage(void)
41 {
42 fprintf(stderr,
43 "usage: sink [-au] [-f <fib>] [<listen addr>] <listen port>\n");
44 exit(1);
45 }
46
47 static void
check_multibind(struct sink_softc * sc)48 check_multibind(struct sink_softc *sc)
49 {
50 const char *sysctl;
51 size_t len;
52 int error, val;
53
54 sysctl = sc->type == SINK_TCP ? "net.inet.tcp.bind_all_fibs" :
55 "net.inet.udp.bind_all_fibs";
56 len = sizeof(val);
57 error = sysctlbyname(sysctl, &val, &len, NULL, 0);
58 if (error != 0)
59 err(1, "sysctlbyname(%s)", sysctl);
60 if (val != 0)
61 errx(1, "multibind is disabled, set %s=0 to enable", sysctl);
62 }
63
64 static void
addrinfo(struct sink_softc * sc,const char * addr,int port)65 addrinfo(struct sink_softc *sc, const char *addr, int port)
66 {
67 struct addrinfo hints, *res, *res1;
68 char portstr[8];
69 int error;
70
71 memset(&sc->ss, 0, sizeof(sc->ss));
72
73 memset(&hints, 0, sizeof(hints));
74 hints.ai_socktype = sc->type == SINK_TCP ? SOCK_STREAM : SOCK_DGRAM;
75 snprintf(portstr, sizeof(portstr), "%d", port);
76 error = getaddrinfo(addr, portstr, &hints, &res);
77 if (error != 0)
78 errx(1, "%s", gai_strerror(error));
79 for (res1 = res; res != NULL; res = res->ai_next) {
80 if ((res->ai_protocol == IPPROTO_TCP && sc->type == SINK_TCP) ||
81 (res->ai_protocol == IPPROTO_UDP && sc->type == SINK_UDP)) {
82 memcpy(&sc->ss, res->ai_addr, res->ai_addrlen);
83 break;
84 }
85 }
86 if (res == NULL) {
87 errx(1, "no %s address found for '%s'",
88 sc->type == SINK_TCP ? "TCP" : "UDP", addr);
89 }
90 freeaddrinfo(res1);
91 }
92
93 int
main(int argc,char ** argv)94 main(int argc, char **argv)
95 {
96 struct sink_softc sc;
97 const char *laddr;
98 int ch, error, fib, lport;
99 bool all;
100
101 all = false;
102 sc.type = SINK_TCP;
103 fib = -1;
104 while ((ch = getopt(argc, argv, "af:u")) != -1) {
105 switch (ch) {
106 case 'a':
107 all = true;
108 break;
109 case 'f':
110 fib = atoi(optarg);
111 break;
112 case 'u':
113 sc.type = SINK_UDP;
114 break;
115 default:
116 usage();
117 break;
118 }
119 }
120 argc -= optind;
121 argv += optind;
122
123 if (all && fib != -1)
124 errx(1, "-a and -f are mutually exclusive");
125 if (fib == -1) {
126 size_t len;
127
128 error = sysctlbyname("net.my_fibnum", &fib, &len, NULL, 0);
129 if (error != 0)
130 err(1, "sysctlbyname(net.my_fibnum)");
131 }
132
133 if (argc == 2) {
134 laddr = argv[0];
135 lport = atoi(argv[1]);
136 } else if (argc == 1) {
137 laddr = NULL;
138 lport = atoi(argv[0]);
139 } else {
140 usage();
141 }
142 addrinfo(&sc, laddr, lport);
143
144 check_multibind(&sc);
145
146 sc.kq = kqueue();
147 if (sc.kq == -1)
148 err(1, "kqueue");
149
150 if (all) {
151 size_t len;
152
153 len = sizeof(sc.nfibs);
154 error = sysctlbyname("net.fibs", &sc.nfibs, &len, NULL, 0);
155 if (error != 0)
156 err(1, "sysctlbyname(net.fibs)");
157 } else {
158 sc.nfibs = 1;
159 }
160
161 sc.fds = calloc(sc.nfibs, sizeof(int));
162 if (sc.fds == NULL)
163 err(1, "calloc");
164 for (int i = 0; i < sc.nfibs; i++) {
165 struct kevent kev;
166 int s;
167
168 if (sc.type == SINK_TCP)
169 s = socket(sc.ss.ss_family, SOCK_STREAM, 0);
170 else
171 s = socket(sc.ss.ss_family, SOCK_DGRAM, 0);
172 if (s == -1)
173 err(1, "socket");
174 error = setsockopt(s, SOL_SOCKET, SO_SETFIB,
175 all ? &i : &fib, sizeof(int));
176 if (error != 0)
177 err(1, "setsockopt(SO_SETFIB)");
178
179 error = bind(s, (struct sockaddr *)&sc.ss, sc.ss.ss_len);
180 if (error != 0)
181 err(1, "bind");
182
183 if (sc.type == SINK_TCP) {
184 error = listen(s, 5);
185 if (error != 0)
186 err(1, "listen");
187 }
188
189 EV_SET(&kev, s, EVFILT_READ, EV_ADD, 0, 0, NULL);
190 error = kevent(sc.kq, &kev, 1, NULL, 0, NULL);
191 if (error != 0)
192 err(1, "kevent");
193
194 sc.fds[i] = s;
195 }
196
197 for (;;) {
198 struct kevent kev;
199 socklen_t optlen;
200 int n;
201
202 n = kevent(sc.kq, NULL, 0, &kev, 1, NULL);
203 if (n == -1)
204 err(1, "kevent");
205 if (n == 0)
206 continue;
207
208 optlen = sizeof(fib);
209 error = getsockopt((int)kev.ident, SOL_SOCKET, SO_FIB,
210 &fib, &optlen);
211 if (error == -1)
212 err(1, "getsockopt(SO_FIB)");
213
214 if (sc.type == SINK_TCP) {
215 int cs;
216
217 printf("accepting connection from FIB %d\n", fib);
218
219 cs = accept((int)kev.ident, NULL, NULL);
220 if (cs == -1)
221 err(1, "accept");
222 close(cs);
223 } else {
224 char buf[1024];
225 ssize_t nb;
226
227 printf("receiving datagram from FIB %d\n", fib);
228
229 nb = recvfrom((int)kev.ident, buf, sizeof(buf), 0,
230 NULL, NULL);
231 if (nb == -1)
232 err(1, "recvfrom");
233 }
234 }
235
236 return (0);
237 }
238