Add hotplug support to the Linux backend.

There are two ways to configure hotplug support for Linux: udev, and netlink. It
is strongly recommened that udev support is used on systems that utilize udev.
We reenforce this recommendation by defaulting to --with-udev=yes at configure
time. To enable netlink support run configure with --with-udev=no. If udev
support is enabled all device enumeration is done with udev.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>

1 files changed, 231 insertions, 0 deletions

diff --git a/libusb/os/linux_netlink.c b/libusb/os/linux_netlink.c
new file mode 100644
index 0000000..c7fbaeb
--- /dev/null
+++ b/libusb/os/linux_netlink.c
@@ -0,0 +1,231 @@
+/* -*- Mode: C; c-basic-offset:8 ; indent-tabs-mode:t -*- */
+/*
+ * Linux usbfs backend for libusb
+ * Copyright (C) 2007-2009 Daniel Drake <dsd@gentoo.org>
+ * Copyright (c) 2001 Johannes Erdfelt <johannes@erdfelt.com>
+ * Copyright (c) 2013 Nathan Hjelm <hjelmn@mac.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "config.h"
+#include <ctype.h>
+#include <dirent.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <poll.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <arpa/inet.h>
+
+#include "libusb.h"
+#include "libusbi.h"
+#include "linux_usbfs.h"
+
+#include <linux/netlink.h>
+#include <linux/filter.h>
+
+#define KERNEL 1
+
+static int linux_netlink_socket = -1;
+static pthread_t libusb_linux_event_thread;
+
+static void *linux_netlink_event_thread_main(void *arg);
+
+struct sockaddr_nl snl = { .nl_family=AF_NETLINK, .nl_groups=KERNEL };
+
+int linux_netlink_start_event_monitor(void)
+{
+	int ret;
+
+	snl.nl_groups = KERNEL;
+
+	linux_netlink_socket = socket(PF_NETLINK, SOCK_RAW|SOCK_CLOEXEC|SOCK_NONBLOCK, NETLINK_KOBJECT_UEVENT);
+	if (-1 == linux_netlink_socket) {
+		return LIBUSB_ERROR_OTHER;
+	}
+
+	ret = bind(linux_netlink_socket, (struct sockaddr *) &snl, sizeof(snl));
+	if (0 != ret) {
+		return LIBUSB_ERROR_OTHER;
+	}
+
+	/* TODO -- add authentication */
+	/* setsockopt(linux_netlink_socket, SOL_SOCKET, SO_PASSCRED, &one, sizeof(one)); */
+
+	ret = pthread_create(&libusb_linux_event_thread, NULL, linux_netlink_event_thread_main, NULL);
+	if (0 != ret) {
+		return LIBUSB_ERROR_OTHER;
+	}
+
+	return LIBUSB_SUCCESS;
+}
+
+int linux_netlink_stop_event_monitor(void)
+{
+	int r;
+
+	if (-1 == linux_netlink_socket) {
+		/* already closed. nothing to do */
+		return LIBUSB_SUCCESS;
+	}
+
+	r = close(linux_netlink_socket);
+	if (0 > r) {
+		usbi_err(NULL, "error closing netlink socket. %s", strerror(errno));
+		return LIBUSB_ERROR_OTHER;
+	}
+
+	pthread_cancel(libusb_linux_event_thread);
+
+	linux_netlink_socket = -1;
+
+	return LIBUSB_SUCCESS;
+}
+
+static const char *netlink_message_parse (const char *buffer, size_t len, const char *key)
+{
+	size_t keylen = strlen(key);
+	size_t offset;
+
+	for (offset = 0 ; offset < len && '\0' != buffer[offset] ; offset += strlen(buffer + offset) + 1) {
+		if (0 == strncmp(buffer + offset, key, keylen) &&
+		    '=' == buffer[offset + keylen]) {
+			return buffer + offset + keylen + 1;
+		}
+	}
+
+	return NULL;
+}
+
+/* parse parts of netlink message common to both libudev and the kernel */
+static int linux_netlink_parse(char *buffer, size_t len, int *detached, const char **sys_name,
+			       uint8_t *busnum, uint8_t *devaddr) {
+	const char *tmp;
+	int i;
+
+	errno = 0;
+
+	*sys_name = NULL;
+	*detached = 0;
+	*busnum   = 0;
+	*devaddr  = 0;
+
+	tmp = netlink_message_parse((const char *) buffer, len, "ACTION");
+	if (0 == strcmp(tmp, "remove")) {
+		*detached = 1;
+	} else if (0 != strcmp(tmp, "add")) {
+		usbi_dbg("unknown device action");
+		return -1;
+	}
+
+	/* check that this is a usb message */
+	tmp = netlink_message_parse(buffer, len, "SUBSYSTEM");
+	if (NULL == tmp || 0 != strcmp(tmp, "usb")) {
+		/* not usb. ignore */
+		return -1;
+	}
+
+	tmp = netlink_message_parse(buffer, len, "BUSNUM");
+	if (NULL == tmp) {
+		/* no bus number (likely a usb interface). ignore*/
+		return -1;
+	}
+
+	*busnum = (uint8_t)(strtoul(tmp, NULL, 10) & 0xff);
+	if (errno) {
+		errno = 0;
+		return -1;
+	}
+
+	tmp = netlink_message_parse(buffer, len, "DEVNUM");
+	if (NULL == tmp) {
+		return -1;
+	}
+
+	*devaddr = (uint8_t)(strtoul(tmp, NULL, 10) & 0xff);
+	if (errno) {
+		errno = 0;
+		return -1;
+	}
+
+	tmp = netlink_message_parse(buffer, len, "DEVPATH");
+	if (NULL == tmp) {
+		return -1;
+	}
+
+	for (i = strlen(tmp) - 1 ; i ; --i) {
+		if ('/' ==tmp[i]) {
+			*sys_name = tmp + i + 1;
+			break;
+		}
+	}
+
+	/* found a usb device */
+	return 0;
+}
+
+static void *linux_netlink_event_thread_main(void *arg)
+{
+	struct pollfd fds = {.fd = linux_netlink_socket,
+			     .events = POLLIN};
+	unsigned char buffer[1024];
+	struct iovec iov = {.iov_base = buffer, .iov_len = sizeof(buffer)};
+	struct msghdr meh = { .msg_iov=&iov, .msg_iovlen=1,
+			     .msg_name=&snl, .msg_namelen=sizeof(snl) };
+	uint8_t busnum, devaddr;
+	int detached, r;
+	size_t len;
+
+	/* silence compiler warning */
+	(void) arg;
+
+	while (1 == poll(&fds, 1, -1)) {
+		const char *sys_name = NULL;
+
+		if (POLLIN != fds.revents) {
+			break;
+		}
+
+		/* read netlink message */
+		memset(buffer, 0, sizeof(buffer));
+		len = recvmsg(linux_netlink_socket, &meh, 0);
+		if (len < 32) {
+			usbi_dbg("error recieving message from netlink");
+			continue;
+		}
+
+		/* TODO -- authenticate this message is from the kernel or udevd */
+
+		r = linux_netlink_parse(buffer, len, &detached, &sys_name,
+					&busnum, &devaddr);
+		if (r)
+			continue;
+
+		usbi_dbg("netlink hotplug found device busnum: %hhu, devaddr: %hhu, sys_name: %s, removed: %s",
+			 busnum, devaddr, sys_name, detached ? "yes" : "no");
+
+		/* signal device is available (or not) to all contexts */
+		if (detached)
+			linux_hotplug_disconnected(busnum, devaddr, sys_name);
+		else
+			linux_hotplug_enumerate(busnum, devaddr, sys_name);
+	}
+
+	return NULL;
+}