/* SPDX-License-Identifier: GPL-2.0 */

/** \file audioc_common.c Code shared between para_gui and para_audioc.
 *
 * There is only one public function here: \ref connect_audiod().
 */

#include "para.h"

#include <netinet/in.h>
#include <sys/socket.h>
#include <netdb.h>

#include "audioc.h"
#include "string.h"
#include "fd.h"
#include "error.h"
#include "net.h"

/*
 * Prepend \0, and cocatenate all arguments using \0 as the separater.
 */
static size_t concat_args(unsigned num_inputs, char * const *argv,
		char **result)
{
	size_t len = 0;
	char *p;

	assert(num_inputs > 0);
	for (unsigned n = 0; n < num_inputs; n++)
		len += strlen(argv[n]) + 1;
	p = *result = alloc(len + 1);
	p[0] = '\0';
	p++;
	for (unsigned n = 0; n < num_inputs; n++)
		p += sprintf(p, "%s", argv[n]) + 1;
	assert(p == *result + len + 1);
	return len + 1;
}

#ifdef HAVE_UCRED
/*
 * Send a buffer and the credentials of the current process to a socket. On
 * success, this call returns the number of bytes sent.
 */
static ssize_t send_cred_buffer(int sock, struct iovec *iov)
{
	char control[sizeof(struct cmsghdr) + sizeof(struct ucred)];
	struct msghdr msg;
	struct cmsghdr *cmsg;
	struct ucred c;
	int ret;

	/* Response data */
	c.pid = getpid();
	c.uid = getuid();
	c.gid = getgid();
	/* compose the message */
	memset(&msg, 0, sizeof(msg));
	msg.msg_iov = iov;
	msg.msg_iovlen = 1;
	msg.msg_control = control;
	msg.msg_controllen = sizeof(control);
	/* attach the ucred struct */
	cmsg = CMSG_FIRSTHDR(&msg);
	cmsg->cmsg_level = SOL_SOCKET;
	cmsg->cmsg_type = SCM_CREDENTIALS;
	cmsg->cmsg_len = CMSG_LEN(sizeof(struct ucred));
	*(struct ucred *)CMSG_DATA(cmsg) = c;
	msg.msg_controllen = cmsg->cmsg_len;
	ret = sendmsg(sock, &msg, 0);
	if (ret < 0)
		return -ERRNO_TO_PARA_ERROR(errno);
	return ret;
}
#else /* no ucred */
static ssize_t send_cred_buffer(int fd, struct iovec *iov)
{
	return xwrite(fd, iov->iov_base, iov->iov_len);
}
#endif /* HAVE_UCRED */

/**
 * Establish a connection to the local socket and send a command.
 *
 * \param sname The path to the local socket. NULL for default.
 * \param num_inputs Number of arguments, including subcommand and options.
 * \param argv Argument vector, does not need to be NULL terminated.
 *
 * \return The file descriptor on success, negative error code otherwise.
 */
int connect_audiod(const char *sname, unsigned num_inputs, char **argv)
{
	int fd = -1, ret;
	char *args;
	struct iovec iov;

	iov.iov_len = concat_args(num_inputs, argv, &args);
	assert(args);
	iov.iov_base = args;
	if (!sname) {
		char *tmp = make_message("/var/paraslash/audiod_socket.%s",
			para_hostname());
		ret = connect_local_socket(tmp);
		free(tmp);
	} else
		ret = connect_local_socket(sname);
	if (ret < 0)
		goto free_args;
	fd = ret;
	ret = send_cred_buffer(fd, &iov);
	if (ret < 0)
		close(fd);
	else
		ret = fd;
free_args:
	free(args);
	if (ret < 0)
		PARA_NOTICE_LOG("failed to connect to para_audiod\n");
	return ret;
}