core-admin/qrexec/write_stdin.c

/*
 * The Qubes OS Project, http://www.qubes-os.org
 *
 * Copyright (C) 2010  Rafal Wojtczuk  <rafal@invisiblethingslab.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 *
 */

#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include "qrexec.h"
#include "buffer.h"
#include "glue.h"

int flush_client_data(int fd, int clid, struct buffer *buffer)
{
	int ret;
	int len;
	for (;;) {
		len = buffer_len(buffer);
		if (len > MAX_DATA_CHUNK)
			len = MAX_DATA_CHUNK;
		ret = write(fd, buffer_data(buffer), len);
		if (ret == -1) {
			if (errno != EAGAIN) {
				return WRITE_STDIN_ERROR;
			} else
				return WRITE_STDIN_BUFFERED;
		}
		buffer_remove(buffer, len);
		len = buffer_len(buffer);
		if (!len) {
			struct server_header s_hdr;
			s_hdr.type = MSG_XON;
			s_hdr.clid = clid;
			s_hdr.len = 0;
			write_all_vchan_ext(&s_hdr, sizeof s_hdr);
			return WRITE_STDIN_OK;
		}
	}

}


int write_stdin(int fd, int clid, char *data, int len,
		struct buffer *buffer)
{
	int ret;

	if (buffer_len(buffer)) {
		buffer_append(buffer, data, len);
		return WRITE_STDIN_BUFFERED;
	}
	
	ret = write(fd, data, len);
	if (ret == len)
		return WRITE_STDIN_OK;
	if (ret == -1) {
		if (errno == EAGAIN) {
			struct server_header s_hdr;
			buffer_append(buffer, data, len);

			s_hdr.type = MSG_XOFF;
			s_hdr.clid = clid;
			s_hdr.len = 0;
			write_all_vchan_ext(&s_hdr, sizeof s_hdr);

			return WRITE_STDIN_BUFFERED;
		} else
			return WRITE_STDIN_ERROR;
	} else {
		fprintf(stderr,
			"writes < PIPE_BUF were supposed to be atomic ?\n");
		return WRITE_STDIN_ERROR;
	}

}