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/*
* mDNS registration handler. This file is part of Shairport.
* Copyright (c) Paul Lietar 2013
* All rights reserved.
*
* Permission is hereby granted, free of charge, to any person
* obtaining a copy of this software and associated documentation
* files (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use,
* copy, modify, merge, publish, distribute, sublicense, and/or
* sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*/
#include "mdns.h"
#include "common.h"
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
int mdns_pid = 0;
/*
* Do a fork followed by a execvp, handling execvp errors correctly.
* Return the pid of the new process upon success, or -1 if something failed.
* Check errno for error details.
*/
static int fork_execvp(const char *file, char *const argv[]) {
int execpipe[2];
int pid = 0;
if (pipe(execpipe) < 0) {
return -1;
}
if (fcntl(execpipe[1], F_SETFD, fcntl(execpipe[1], F_GETFD) | FD_CLOEXEC) < 0) {
close(execpipe[0]);
close(execpipe[1]);
return -1;
}
pid = fork();
if (pid < 0) {
close(execpipe[0]);
close(execpipe[1]);
return -1;
} else if (pid == 0) { // Child
close(execpipe[0]); // Close the read end
execvp(file, argv);
// If we reach this point then execve has failed.
// Write erno's value into the pipe and exit.
if (write(execpipe[1], &errno, sizeof(errno)) != sizeof(errno))
debug(1, "Execve has failed and there was a further error writing an error message, duh.");
debug(1, "execve has failed.");
_exit(-1);
return 0; // Just to make the compiler happy.
} else { // Parent
close(execpipe[1]); // Close the write end
int childErrno;
// Block until child closes the pipe or sends errno.
if (read(execpipe[0], &childErrno, sizeof(childErrno)) ==
sizeof(childErrno)) { // We received errno
errno = childErrno;
return -1;
} else { // Child closed the pipe. execvp was successful.
return pid;
}
}
}
static int mdns_external_avahi_register(char *apname, __attribute__((unused)) int port) {
char mdns_port[6];
snprintf(mdns_port, sizeof(mdns_port), "%d", config.port);
char *argvwithoutmetadata[] = {
NULL, apname, config.regtype, mdns_port, MDNS_RECORD_WITHOUT_METADATA, NULL};
#ifdef CONFIG_METADATA
char *argvwithmetadata[] = {NULL, apname, config.regtype, mdns_port, MDNS_RECORD_WITH_METADATA,
NULL};
#endif
char **argv;
#ifdef CONFIG_METADATA
if (config.metadata_enabled)
argv = argvwithmetadata;
else
#endif
argv = argvwithoutmetadata;
argv[0] = "avahi-publish-service";
int pid = fork_execvp(argv[0], argv);
if (pid >= 0) {
mdns_pid = pid;
return 0;
} else
warn("Calling %s failed !", argv[0]);
argv[0] = "mDNSPublish";
pid = fork_execvp(argv[0], argv);
if (pid >= 0) {
mdns_pid = pid;
return 0;
} else
warn("Calling %s failed !", argv[0]);
// If we reach here, both execvp calls failed.
return -1;
}
static int mdns_external_dns_sd_register(char *apname, __attribute__((unused)) int port) {
char mdns_port[6];
snprintf(mdns_port, sizeof(mdns_port), "%d", config.port);
char *argvwithoutmetadata[] = {
NULL, apname, config.regtype, mdns_port, MDNS_RECORD_WITHOUT_METADATA, NULL};
#ifdef CONFIG_METADATA
char *argvwithmetadata[] = {NULL, apname, config.regtype, mdns_port, MDNS_RECORD_WITH_METADATA,
NULL};
#endif
char **argv;
#ifdef CONFIG_METADATA
if (config.metadata_enabled)
argv = argvwithmetadata;
else
#endif
argv = argvwithoutmetadata;
int pid = fork_execvp(argv[0], argv);
if (pid >= 0) {
mdns_pid = pid;
return 0;
} else
warn("Calling %s failed !", argv[0]);
return -1;
}
static void kill_mdns_child(void) {
if (mdns_pid)
kill(mdns_pid, SIGTERM);
mdns_pid = 0;
}
mdns_backend mdns_external_avahi = {.name = "external-avahi",
.mdns_register = mdns_external_avahi_register,
.mdns_unregister = kill_mdns_child,
.mdns_dacp_monitor = NULL,
.mdns_dacp_dont_monitor = NULL};
mdns_backend mdns_external_dns_sd = {.name = "external-dns-sd",
.mdns_register = mdns_external_dns_sd_register,
.mdns_unregister = kill_mdns_child,
.mdns_dacp_monitor = NULL,
.mdns_dacp_dont_monitor = NULL};
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