/*
 * Copyright (C) 2011-2014 Felix Fietkau <nbd@openwrt.org>
 *
 * SPDX-License-Identifier: LGPL-2.1-only
 */

#define _GNU_SOURCE

#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
#ifdef FreeBSD
#include <sys/param.h>
#endif
#include <fcntl.h>
#include <string.h>
#include <syslog.h>

#include <libubox/usock.h>

#include "ubusd.h"

static void ubus_client_cmd_free(struct ubus_client_cmd *cmd);

static void handle_client_disconnect(struct ubus_client *cl)
{
	struct ubus_msg_buf_list *ubl, *ubl2;
	struct ubus_client_cmd *cmd, *cmd2;

	list_for_each_entry_safe(cmd, cmd2, &cl->cmd_queue, list)
		ubus_client_cmd_free(cmd);

	ubusd_monitor_disconnect(cl);
	ubusd_proto_free_client(cl);

	/*
	 * Freeing the client's objects above can queue new messages for the
	 * disconnecting client itself (e.g. the subscribers-gone notification
	 * sent by ubus_unsubscribe), so the tx queue must be flushed last.
	 */
	list_for_each_entry_safe(ubl, ubl2, &cl->tx_queue, list)
		ubus_msg_list_free(ubl);
	if (cl->pending_msg_fd >= 0)
		close(cl->pending_msg_fd);
	if (cl->pending_msg)
		ubus_msg_free(cl->pending_msg);
	uloop_fd_delete(&cl->sock);
	close(cl->sock.fd);
	free(cl);
}

static void ubus_client_cmd_free(struct ubus_client_cmd *cmd)
{
	list_del(&cmd->list);
	ubus_msg_free(cmd->msg);
	free(cmd->lookup_path);
	free(cmd);
}

static void ubus_client_cmd_queue_process(struct ubus_client *cl)
{
	struct ubus_client_cmd *cmd, *tmp;

	list_for_each_entry_safe(cmd, tmp, &cl->cmd_queue, list) {
		int ret = ubusd_cmd_lookup(cl, cmd);

		/* Stop if the last command caused buffering again */
		if (ret == -2)
			break;

		ubus_client_cmd_free(cmd);
	}
}

static int ubusd_recv_fd(struct msghdr *msghdr)
{
	struct cmsghdr *cmsg;

	for (cmsg = CMSG_FIRSTHDR(msghdr); cmsg; cmsg = CMSG_NXTHDR(msghdr, cmsg)) {
		if (cmsg->cmsg_level != SOL_SOCKET || cmsg->cmsg_type != SCM_RIGHTS)
			continue;
		if (cmsg->cmsg_len < CMSG_LEN(sizeof(int)))
			continue;

		return *(int *) CMSG_DATA(cmsg);
	}

	return -1;
}

static void client_cb(struct uloop_fd *sock, unsigned int events)
{
	struct ubus_client *cl = container_of(sock, struct ubus_client, sock);
	uint8_t fd_buf[CMSG_SPACE(sizeof(int))] = { 0 };
	struct msghdr msghdr = { 0 };
	struct ubus_msg_buf *ub;
	struct ubus_msg_buf_list *ubl, *ubl2;
	static struct iovec iov;

	msghdr.msg_iov = &iov;
	msghdr.msg_iovlen = 1;

	/* first try to tx more pending data */
	list_for_each_entry_safe(ubl, ubl2, &cl->tx_queue, list) {
		ssize_t written;

		ub = ubl->msg;
retry_writev:
		written = ubus_msg_writev(sock->fd, ub, cl->txq_ofs);
		if (written < 0) {
			switch(errno) {
			case EINTR:
				goto retry_writev;
			case EAGAIN:
			case EACCES:
				break;
			default:
				goto disconnect;
			}
			break;
		}

		cl->txq_ofs += written;
		cl->txq_len -= written;
		if (cl->txq_ofs < ub->len + sizeof(ub->hdr))
			goto retry_writev;

		cl->txq_ofs = 0;
		ubus_msg_list_free(ubl);
	}

	if (list_empty(&cl->tx_queue) && (events & ULOOP_WRITE)) {
		/* Process queued commands */
		ubus_client_cmd_queue_process(cl);

		/* prevent further ULOOP_WRITE events if we don't have data
		 * to send anymore */
		if (list_empty(&cl->tx_queue))
			uloop_fd_add(sock, ULOOP_READ | ULOOP_EDGE_TRIGGER);
	}

retry:
	if (!sock->eof && cl->pending_msg_offset < (int) sizeof(cl->hdrbuf)) {
		int offset = cl->pending_msg_offset;
		int bytes;

		iov.iov_base = ((char *) &cl->hdrbuf) + offset;
		iov.iov_len = sizeof(cl->hdrbuf) - offset;

		msghdr.msg_control = fd_buf;
		msghdr.msg_controllen = cl->pending_msg_fd < 0 ? sizeof(fd_buf) : 0;

		bytes = recvmsg(sock->fd, &msghdr, 0);
		if (bytes < 0)
			goto out;

		if (cl->pending_msg_fd < 0) {
			int fd = ubusd_recv_fd(&msghdr);

			if (fd >= 0)
				cl->pending_msg_fd = fd;
		}

		cl->pending_msg_offset += bytes;
		if (cl->pending_msg_offset < (int) sizeof(cl->hdrbuf))
			goto out;

		if (blob_raw_len(&cl->hdrbuf.data) < sizeof(struct blob_attr))
			goto disconnect;
		if (blob_pad_len(&cl->hdrbuf.data) > UBUS_MAX_MSGLEN)
			goto disconnect;

		cl->pending_msg = ubus_msg_new(NULL, blob_raw_len(&cl->hdrbuf.data), false);
		if (!cl->pending_msg)
			goto disconnect;

		cl->hdrbuf.hdr.seq = be16_to_cpu(cl->hdrbuf.hdr.seq);
		cl->hdrbuf.hdr.peer = be32_to_cpu(cl->hdrbuf.hdr.peer);

		memcpy(&cl->pending_msg->hdr, &cl->hdrbuf.hdr, sizeof(cl->hdrbuf.hdr));
		memcpy(cl->pending_msg->data, &cl->hdrbuf.data, sizeof(cl->hdrbuf.data));
	}

	ub = cl->pending_msg;
	if (ub) {
		/*
		 * offset and len derive from client-controlled input, but the
		 * read stays within bounds: ub->data was allocated with exactly
		 * blob_raw_len(ub->data) bytes (already capped at UBUS_MAX_MSGLEN
		 * when the header was received), and offset only grows until it
		 * reaches that total, at which point the message is accepted and
		 * pending_msg is reset below. So offset <= blob_raw_len(ub->data)
		 * and offset + len never exceed the allocation.
		 */
		int offset = cl->pending_msg_offset - sizeof(ub->hdr);
		int len = blob_raw_len(ub->data) - offset;
		int bytes = 0;

		if (len > 0) {
			bytes = read(sock->fd, (char *) ub->data + offset, len);
			if (bytes <= 0)
				goto out;
		}

		if (bytes < len) {
			cl->pending_msg_offset += bytes;
			goto out;
		}

		/* accept message */
		ub->fd = cl->pending_msg_fd;
		cl->pending_msg_fd = -1;
		cl->pending_msg_offset = 0;
		cl->pending_msg = NULL;
		ubusd_monitor_message(cl, ub, false);
		ubusd_proto_receive_message(cl, ub);
		goto retry;
	}

out:
	if (!sock->eof || !list_empty(&cl->tx_queue))
		return;

disconnect:
	handle_client_disconnect(cl);
}

static bool get_next_connection(int fd)
{
	struct ubus_client *cl;
	int client_fd;

	client_fd = accept(fd, NULL, 0);
	if (client_fd < 0) {
		switch (errno) {
		case ECONNABORTED:
		case EINTR:
			return true;
		default:
			return false;
		}
	}

	cl = ubusd_proto_new_client(client_fd, client_cb);
	if (cl)
		uloop_fd_add(&cl->sock, ULOOP_READ | ULOOP_EDGE_TRIGGER);
	else
		close(client_fd);

	return true;
}

static void server_cb(struct uloop_fd *fd, unsigned int events)
{
	bool next;

	do {
		next = get_next_connection(fd->fd);
	} while (next);
}

static struct uloop_fd server_fd = {
	.cb = server_cb,
};

static int usage(const char *progname)
{
	fprintf(stderr, "Usage: %s [<options>]\n"
		"Options: \n"
		"  -A <path>:		Set the path to ACL files\n"
		"  -s <socket>:		Set the unix domain socket to listen on\n"
		"\n", progname);
	return 1;
}

static int sighup_pipe[2] = { -1, -1 };

static void sighup_handler(int sig)
{
	int saved_errno = errno;
	char c = 0;
	ssize_t r = write(sighup_pipe[1], &c, sizeof(c));
	(void)r;
	errno = saved_errno;
}

static void sighup_fd_cb(struct uloop_fd *ufd, unsigned int events)
{
	char buf[16];
	while (read(ufd->fd, buf, sizeof(buf)) > 0)
		;
	ubusd_acl_load();
}

static struct uloop_fd sighup_ufd = {
	.cb = sighup_fd_cb,
};

/*
 * Best effort only: the -s option may point somewhere else entirely, and
 * usock() reports a clear error if the requested socket path is unusable.
 */
static void mkdir_sockdir(void)
{
	char *ubus_sock_dir, *tmp;

	ubus_sock_dir = strdup(UBUS_UNIX_SOCKET);
	if (!ubus_sock_dir)
		return;

	tmp = strrchr(ubus_sock_dir, '/');
	if (tmp) {
		*tmp = '\0';
		if (mkdir(ubus_sock_dir, 0755) && errno == EEXIST) {
			struct stat st;

			if (stat(ubus_sock_dir, &st) || !S_ISDIR(st.st_mode))
				fprintf(stderr, "%s exists but is not a directory\n",
					ubus_sock_dir);
		}
	}

	free(ubus_sock_dir);
}

#include <libubox/ulog.h>

int main(int argc, char **argv)
{
	const char *ubus_socket = UBUS_UNIX_SOCKET;
	int ret = 0;
	int ch;

	signal(SIGPIPE, SIG_IGN);

#ifdef __linux__
	ret = pipe2(sighup_pipe, O_NONBLOCK | O_CLOEXEC);
#else
	ret = pipe(sighup_pipe);
	if (ret == 0) {
		fcntl(sighup_pipe[0], F_SETFL, O_NONBLOCK);
		fcntl(sighup_pipe[0], F_SETFD, FD_CLOEXEC);
		fcntl(sighup_pipe[1], F_SETFL, O_NONBLOCK);
		fcntl(sighup_pipe[1], F_SETFD, FD_CLOEXEC);
	}
#endif
	if (ret == 0)
		signal(SIGHUP, sighup_handler);
	else
		signal(SIGHUP, SIG_IGN);

	ulog_open(ULOG_KMSG | ULOG_SYSLOG, LOG_DAEMON, "ubusd");
	openlog("ubusd", LOG_PID, LOG_DAEMON);
	uloop_init();

	if (sighup_pipe[0] >= 0) {
		sighup_ufd.fd = sighup_pipe[0];
		uloop_fd_add(&sighup_ufd, ULOOP_READ);
	}

	while ((ch = getopt(argc, argv, "A:s:")) != -1) {
		switch (ch) {
		case 's':
			ubus_socket = optarg;
			break;
		case 'A':
			ubusd_acl_dir = optarg;
			break;
		default:
			return usage(argv[0]);
		}
	}

	mkdir_sockdir();
	unlink(ubus_socket);
	umask(0111);
	server_fd.fd = usock(USOCK_UNIX | USOCK_SERVER | USOCK_NONBLOCK, ubus_socket, NULL);
	if (server_fd.fd < 0) {
		perror("usock");
		ret = -1;
		goto out;
	}
	uloop_fd_add(&server_fd, ULOOP_READ | ULOOP_EDGE_TRIGGER);
	ubusd_acl_load();

	uloop_run();
	unlink(ubus_socket);

out:
	uloop_done();
	return ret;
}