summaryrefslogtreecommitdiff
path: root/src/libcamera/ipc_unixsocket.cpp
blob: 7df86e885f23a23d4858b3ddf770b94ee0dc807c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
 * Copyright (C) 2019, Google Inc.
 *
 * ipc_unixsocket.cpp - IPC mechanism based on Unix sockets
 */

#include "libcamera/internal/ipc_unixsocket.h"

#include <poll.h>
#include <string.h>
#include <sys/socket.h>
#include <unistd.h>

#include "libcamera/internal/log.h"

/**
 * \file ipc_unixsocket.h
 * \brief IPC mechanism based on Unix sockets
 */

namespace libcamera {

LOG_DEFINE_CATEGORY(IPCUnixSocket)

/**
 * \struct IPCUnixSocket::Payload
 * \brief Container for an IPC payload
 *
 * Holds an array of bytes and an array of file descriptors that can be
 * transported across a IPC boundary.
 */

/**
 * \var IPCUnixSocket::Payload::data
 * \brief Array of bytes to cross IPC boundary
 */

/**
 * \var IPCUnixSocket::Payload::fds
 * \brief Array of file descriptors to cross IPC boundary
 */

/**
 * \class IPCUnixSocket
 * \brief IPC mechanism based on Unix sockets
 *
 * The Unix socket IPC allows bidirectional communication between two processes
 * through unnamed Unix sockets. It implements datagram-based communication,
 * transporting entire payloads with guaranteed ordering.
 *
 * The IPC design is asynchronous, a message is queued to a receiver which gets
 * notified that a message is ready to be consumed by the \ref readyRead
 * signal. The sender of the message gets no notification when a message is
 * delivered nor processed. If such interactions are needed a protocol specific
 * to the users use-case should be implemented on top of the IPC objects.
 *
 * Establishment of an IPC channel is asymmetrical. The side that initiates
 * communication first instantiates a local side socket and creates the channel
 * with create(). The method returns a file descriptor for the remote side of
 * the channel, which is passed to the remote process through an out-of-band
 * communication method. The remote side then instantiates a socket, and binds
 * it to the other side by passing the file descriptor to bind(). At that point
 * the channel is operation and communication is bidirectional and symmmetrical.
 *
 * \context This class is \threadbound.
 */

IPCUnixSocket::IPCUnixSocket()
	: fd_(-1), headerReceived_(false), notifier_(nullptr)
{
}

IPCUnixSocket::~IPCUnixSocket()
{
	close();
}

/**
 * \brief Create an new IPC channel
 *
 * This method creates a new IPC channel. The socket instance is bound to the
 * local side of the channel, and the method returns a file descriptor bound to
 * the remote side. The caller is responsible for passing the file descriptor to
 * the remote process, where it can be used with IPCUnixSocket::bind() to bind
 * the remote side socket.
 *
 * \return A file descriptor on success, negative error code on failure
 */
int IPCUnixSocket::create()
{
	int sockets[2];
	int ret;

	ret = socketpair(AF_UNIX, SOCK_DGRAM | SOCK_NONBLOCK, 0, sockets);
	if (ret) {
		ret = -errno;
		LOG(IPCUnixSocket, Error)
			<< "Failed to create socket pair: " << strerror(-ret);
		return ret;
	}

	ret = bind(sockets[0]);
	if (ret)
		return ret;

	return sockets[1];
}

/**
 * \brief Bind to an existing IPC channel
 * \param[in] fd File descriptor
 *
 * This method binds the socket instance to an existing IPC channel identified
 * by the file descriptor \a fd. The file descriptor is obtained from the
 * IPCUnixSocket::create() method.
 *
 * \return 0 on success or a negative error code otherwise
 */
int IPCUnixSocket::bind(int fd)
{
	if (isBound())
		return -EINVAL;

	fd_ = fd;
	notifier_ = new EventNotifier(fd_, EventNotifier::Read);
	notifier_->activated.connect(this, &IPCUnixSocket::dataNotifier);

	return 0;
}

/**
 * \brief Close the IPC channel
 *
 * No communication is possible after close() has been called.
 */
void IPCUnixSocket::close()
{
	if (!isBound())
		return;

	delete notifier_;
	notifier_ = nullptr;

	::close(fd_);

	fd_ = -1;
	headerReceived_ = false;
}

/**
 * \brief Check if the IPC channel is bound
 * \return True if the IPC channel is bound, false otherwise
 */
bool IPCUnixSocket::isBound() const
{
	return fd_ != -1;
}

/**
 * \brief Send a message payload
 * \param[in] payload Message payload to send
 *
 * This method queues the message payload for transmission to the other end of
 * the IPC channel. It returns immediately, before the message is delivered to
 * the remote side.
 *
 * \return 0 on success or a negative error code otherwise
 */
int IPCUnixSocket::send(const Payload &payload)
{
	int ret;

	if (!isBound())
		return -ENOTCONN;

	Header hdr = {};
	hdr.data = payload.data.size();
	hdr.fds = payload.fds.size();

	if (!hdr.data && !hdr.fds)
		return -EINVAL;

	ret = ::send(fd_, &hdr, sizeof(hdr), 0);
	if (ret < 0) {
		ret = -errno;
		LOG(IPCUnixSocket, Error)
			<< "Failed to send: " << strerror(-ret);
		return ret;
	}

	return sendData(payload.data.data(), hdr.data, payload.fds.data(), hdr.fds);
}

/**
 * \brief Receive a message payload
 * \param[out] payload Payload where to write the received message
 *
 * This method receives the message payload from the IPC channel and writes it
 * to the \a payload. If no message payload is available, it returns
 * immediately with -EAGAIN. The \ref readyRead signal shall be used to receive
 * notification of message availability.
 *
 * \todo Add state machine to make sure we don't block forever and that
 * a header is always followed by a payload.
 *
 * \return 0 on success or a negative error code otherwise
 * \retval -EAGAIN No message payload is available
 * \retval -ENOTCONN The socket is not connected (neither create() nor bind()
 * has been called)
 */
int IPCUnixSocket::receive(Payload *payload)
{
	if (!isBound())
		return -ENOTCONN;

	if (!headerReceived_)
		return -EAGAIN;

	payload->data.resize(header_.data);
	payload->fds.resize(header_.fds);

	int ret = recvData(payload->data.data(), header_.data,
			   payload->fds.data(), header_.fds);
	if (ret < 0)
		return ret;

	headerReceived_ = false;
	notifier_->setEnabled(true);

	return 0;
}

/**
 * \var IPCUnixSocket::readyRead
 * \brief A Signal emitted when a message is ready to be read
 */

int IPCUnixSocket::sendData(const void *buffer, size_t length,
			    const int32_t *fds, unsigned int num)
{
	struct iovec iov[1];
	iov[0].iov_base = const_cast<void *>(buffer);
	iov[0].iov_len = length;

	char buf[CMSG_SPACE(num * sizeof(uint32_t))];
	memset(buf, 0, sizeof(buf));

	struct cmsghdr *cmsg = (struct cmsghdr *)buf;
	cmsg->cmsg_len = CMSG_LEN(num * sizeof(uint32_t));
	cmsg->cmsg_level = SOL_SOCKET;
	cmsg->cmsg_type = SCM_RIGHTS;

	struct msghdr msg;
	msg.msg_name = nullptr;
	msg.msg_namelen = 0;
	msg.msg_iov = iov;
	msg.msg_iovlen = 1;
	msg.msg_control = cmsg;
	msg.msg_controllen = cmsg->cmsg_len;
	msg.msg_flags = 0;
	memcpy(CMSG_DATA(cmsg), fds, num * sizeof(uint32_t));

	if (sendmsg(fd_, &msg, 0) < 0) {
		int ret = -errno;
		LOG(IPCUnixSocket, Error)
			<< "Failed to sendmsg: " << strerror(-ret);
		return ret;
	}

	return 0;
}

int IPCUnixSocket::recvData(void *buffer, size_t length,
			    int32_t *fds, unsigned int num)
{
	struct iovec iov[1];
	iov[0].iov_base = buffer;
	iov[0].iov_len = length;

	char buf[CMSG_SPACE(num * sizeof(uint32_t))];
	memset(buf, 0, sizeof(buf));

	struct cmsghdr *cmsg = (struct cmsghdr *)buf;
	cmsg->cmsg_len = CMSG_LEN(num * sizeof(uint32_t));
	cmsg->cmsg_level = SOL_SOCKET;
	cmsg->cmsg_type = SCM_RIGHTS;

	struct msghdr msg;
	msg.msg_name = nullptr;
	msg.msg_namelen = 0;
	msg.msg_iov = iov;
	msg.msg_iovlen = 1;
	msg.msg_control = cmsg;
	msg.msg_controllen = cmsg->cmsg_len;
	msg.msg_flags = 0;

	if (recvmsg(fd_, &msg, 0) < 0) {
		int ret = -errno;
		if (ret != -EAGAIN)
			LOG(IPCUnixSocket, Error)
				<< "Failed to recvmsg: " << strerror(-ret);
		return ret;
	}

	memcpy(fds, CMSG_DATA(cmsg), num * sizeof(uint32_t));

	return 0;
}

void IPCUnixSocket::dataNotifier(EventNotifier *notifier)
{
	int ret;

	if (!headerReceived_) {
		/* Receive the header. */
		ret = ::recv(fd_, &header_, sizeof(header_), 0);
		if (ret < 0) {
			ret = -errno;
			LOG(IPCUnixSocket, Error)
				<< "Failed to receive header: " << strerror(-ret);
			return;
		}

		headerReceived_ = true;
	}

	/*
	 * If the payload has arrived, disable the notifier and emit the
	 * readyRead signal. The notifier will be reenabled by the receive()
	 * method.
	 */
	struct pollfd fds = { fd_, POLLIN, 0 };
	ret = poll(&fds, 1, 0);
	if (ret < 0)
		return;

	if (!(fds.revents & POLLIN))
		return;

	notifier_->setEnabled(false);
	readyRead.emit(this);
}

} /* namespace libcamera */