158 lines
3.2 KiB
C
158 lines
3.2 KiB
C
/*
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* discard
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* Written in 2020-2021 by Lucas
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* CC0 1.0 Universal/Public domain - No rights reserved
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*
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* To the extent possible under law, the author(s) have dedicated all
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* copyright and related and neighboring rights to this software to the
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* public domain worldwide. This software is distributed without any
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* warranty. You should have received a copy of the CC0 Public Domain
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* Dedication along with this software. If not, see
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* <http://creativecommons.org/publicdomain/zero/1.0/>.
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*/
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#include <err.h>
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#include <errno.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <sys/types.h>
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#include <sys/socket.h>
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#include <netdb.h>
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#define nelems(_a) (sizeof((_a)) / sizeof((_a)[0]))
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static void
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print_listen_address(const struct sockaddr *sa, socklen_t salen, int family)
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{
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char host[NI_MAXHOST], serv[NI_MAXSERV];
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int error;
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int flags = NI_NUMERICHOST | NI_NUMERICSERV;
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error = getnameinfo(sa, salen, host, NI_MAXHOST, serv, NI_MAXSERV,
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flags);
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if (error) {
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warnx("%s", gai_strerror(error));
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} else {
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if (family == AF_INET6)
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fprintf(stderr, "Listening on [%s]:%s\n", host, serv);
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else
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fprintf(stderr, "Listening on %s:%s\n", host, serv);
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}
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}
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static void
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listen_sock_setup(const char *port, int socktype, int *s, size_t *maxsocks)
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{
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struct addrinfo hints, *res, *res0;
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const char *cause = NULL;
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int error, save_errno, nsock;
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memset(&hints, 0, sizeof(hints));
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hints.ai_family = AF_UNSPEC;
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hints.ai_socktype = socktype;
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hints.ai_flags = AI_PASSIVE;
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error = getaddrinfo(NULL, port, &hints, &res0);
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if (error)
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errx(1, "%s", gai_strerror(error));
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nsock = 0;
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for (res = res0; res && nsock < *maxsocks; res = res->ai_next) {
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s[nsock] = socket(res->ai_family, res->ai_socktype,
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res->ai_protocol);
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if (s[nsock] == -1) {
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cause = "socket";
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continue;
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}
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if (bind(s[nsock], res->ai_addr, res->ai_addrlen) == -1) {
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cause = "bind";
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save_errno = errno;
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close(s[nsock]);
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errno = save_errno;
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continue;
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}
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if (listen(s[nsock], 5) == -1) {
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cause = "listen";
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continue;
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}
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print_listen_address(res->ai_addr, res->ai_addrlen,
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res->ai_family);
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nsock++;
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}
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if (nsock == 0)
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err(1, "%s", cause);
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freeaddrinfo(res0);
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*maxsocks = nsock;
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}
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static void
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handle_tcp(const char *port)
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{
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int s[8];
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size_t nsocks = nelems(s);
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size_t i;
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listen_sock_setup(port, SOCK_STREAM, s, &nsocks);
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for (i = 0; i < nsocks; i++)
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close(s[i]);
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}
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static void
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handle_udp(const char *port)
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{
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errx(1, "UDP unimplemented");
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}
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static void
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usage(void)
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{
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fprintf(stderr, "Usage: %s -t | -u\n", getprogname());
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exit(1);
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}
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int
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main(int argc, char *argv[])
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{
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const char *port = NULL;
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int ch, do_tcp, do_udp;
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do_tcp = do_udp = 0;
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while ((ch = getopt(argc, argv, "tu")) != -1) {
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switch (ch) {
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case 't':
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do_tcp = 1;
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break;
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case 'u':
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do_udp = 1;
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break;
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default:
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usage();
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}
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}
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argc -= optind;
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argv += optind;
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port = geteuid() == 0 ? "discard" : "9999";
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if (argc > 0)
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usage();
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if (!do_tcp && !do_udp)
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errx(1, "one of -t or -u is needed");
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if (do_tcp && do_udp)
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errx(1, "-t and -u are mutually exclusive");
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if (do_udp)
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handle_udp(port);
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if (do_tcp)
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handle_tcp(port);
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return 0;
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}
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