[libcamera-devel] [PATCH 1/2] libcamera: ipc: unix: Add a IPC mechanism based on Unix sockets
Niklas Söderlund
niklas.soderlund at ragnatech.se
Thu Jun 27 04:09:54 CEST 2019
To be able to isolate an IPA component in a separate process an IPC
mechanism is needed to communicate with it. Add an IPC mechanism based
on Unix sockets which allows users to pass both data and file descriptors
to and from the IPA process.
The implementation allows users to send both data and file descriptors
in the same message. This allows users to more easily implement
serialization and deserialization of objects as all elements belonging
to an object can be sent in one message.
Signed-off-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>
---
src/libcamera/include/ipc_unixsocket.h | 59 +++++
src/libcamera/ipc_unixsocket.cpp | 288 +++++++++++++++++++++++++
src/libcamera/meson.build | 2 +
3 files changed, 349 insertions(+)
create mode 100644 src/libcamera/include/ipc_unixsocket.h
create mode 100644 src/libcamera/ipc_unixsocket.cpp
diff --git a/src/libcamera/include/ipc_unixsocket.h b/src/libcamera/include/ipc_unixsocket.h
new file mode 100644
index 0000000000000000..68edbe72e2af1298
--- /dev/null
+++ b/src/libcamera/include/ipc_unixsocket.h
@@ -0,0 +1,59 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2019, Google Inc.
+ *
+ * ipc_unixsocket.h - IPC mechanism based on Unix sockets
+ */
+
+#ifndef __LIBCAMERA_IPC_UNIXSOCKET_H__
+#define __LIBCAMERA_IPC_UNIXSOCKET_H__
+
+#include <cstdint>
+#include <sys/types.h>
+#include <vector>
+
+#include <libcamera/event_notifier.h>
+
+namespace libcamera {
+
+class IPCUnixSocket
+{
+public:
+ struct Payload {
+ std::vector<uint8_t> data;
+ std::vector<int32_t> fds;
+ };
+
+ IPCUnixSocket();
+
+ int create();
+ int attach(int fd);
+ void close();
+
+ Signal<const Payload &> payloadReceived;
+
+ int send(Payload &payload);
+
+private:
+ struct Header {
+ uint32_t data;
+ uint8_t fds;
+ };
+
+ int configure();
+
+ int sendData(void *buffer, size_t length, const int32_t *fds, unsigned int num);
+
+ int recv();
+ int recvData(void *buffer, size_t length, int32_t *fds, unsigned int num);
+
+ void dataNotifier(EventNotifier *notifier);
+
+ int fd_;
+ bool master_;
+ EventNotifier *notifier_;
+};
+
+} /* namespace libcamera */
+
+#endif /* __LIBCAMERA_IPC_UNIXSOCKET_H__ */
diff --git a/src/libcamera/ipc_unixsocket.cpp b/src/libcamera/ipc_unixsocket.cpp
new file mode 100644
index 0000000000000000..7b3d8995374dac1e
--- /dev/null
+++ b/src/libcamera/ipc_unixsocket.cpp
@@ -0,0 +1,288 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2019, Google Inc.
+ *
+ * ipc_unixsocket.cpp - IPC mechanism based on Unix sockets
+ */
+
+#include "ipc_unixsocket.h"
+
+#include <string.h>
+#include <sys/socket.h>
+#include <unistd.h>
+
+#include "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 IPC mechanism provided by libcamera are centred around passing arrays of
+ * raw bytes and file descriptors between processes. The primary users of the
+ * IPC objects are pipeline handlers and Image Processing Algorithms components.
+ * A pipeline handler would act as an IPC master and send messages for an IPA to
+ * process and react to.
+ *
+ * The IPC design is asynchronous, a message is queued to a receiver which gets
+ * notified that a message is ready to be consumed by a signal. The queuer of
+ * the message gets no notification when a message is delivers nor processed.
+ * If such interactions are needed a protocol specific to the users use-case
+ * should be implemented on top of the IPC objects.
+ *
+ * The IPC design can transmit messages in any direction and the only difference
+ * from a master and slave operation is how they are created and attached to one
+ * another. After the two parts are setup the operation to send and receive
+ * messages are the same for both.
+ */
+
+IPCUnixSocket::IPCUnixSocket()
+ : fd_(-1), master_(false), notifier_(nullptr)
+{
+}
+
+/**
+ * \brief Create an new IPC channel
+ *
+ * Create a new IPC channel. Returned on success is a file descriptor which
+ * needs to be passed to the slave process and used when attaching to the IPC
+ * channel using attach().
+ *
+ * \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, 0, sockets);
+ if (ret) {
+ ret = -errno;
+ LOG(IPCUnixSocket, Error)
+ << "Failed to create socket pair: " << strerror(-ret);
+ return ret;
+ }
+
+ fd_ = sockets[0];
+ master_ = true;
+
+ ret = configure();
+ if (ret)
+ return ret;
+
+ return sockets[1];
+}
+
+/**
+ * \brief Attach to an existing IPC channel
+ * \param[in] fd File descriptor
+ *
+ * Attach to an existing IPC channel. The \a fd argument is the file descriptor
+ * returned from create() in the master process and passed to the slave process
+ * to be able to establish the IPC channel.
+ *
+ * \return 0 on success or a negative error code otherwise
+ */
+int IPCUnixSocket::attach(int fd)
+{
+ fd_ = fd;
+
+ return configure();
+}
+
+/**
+ * \brief Close the IPC channel
+ *
+ * Close the IPC channel, no communication is possible after close() have been
+ * called.
+ */
+void IPCUnixSocket::close()
+{
+ delete notifier_;
+
+ if (fd_ == -1)
+ return;
+
+ ::close(fd_);
+
+ fd_ = -1;
+}
+
+/**
+ * \brief Send a message payload
+ * \param[in] payload Message payload to send
+ *
+ * Queues the message payload for transmission to the other end of the IPC
+ * channel.
+ *
+ * \return 0 on success or a negative error code otherwise
+ */
+int IPCUnixSocket::send(Payload &payload)
+{
+ Header hdr;
+ int ret;
+
+ if (fd_ < 0)
+ return -ENOTCONN;
+
+ hdr.data = payload.data.size();
+ hdr.fds = payload.fds.size();
+
+ ret = ::send(fd_, &hdr, sizeof(hdr), 0);
+ if (ret < 0) {
+ ret = -errno;
+ LOG(IPCUnixSocket, Error)
+ << "Failed to send: " << strerror(-ret);
+ return ret;
+ }
+
+ ret = sendData(payload.data.data(), hdr.data, payload.fds.data(), hdr.fds);
+ if (ret)
+ return ret;
+
+ return 0;
+}
+
+/**
+ * \var IPCUnixSocket::payloadReceived
+ * \brief A Signal emitted when a message payload is received
+ */
+
+int IPCUnixSocket::configure()
+{
+ notifier_ = new EventNotifier(fd_, EventNotifier::Read);
+ notifier_->activated.connect(this, &IPCUnixSocket::dataNotifier);
+
+ return 0;
+}
+
+int IPCUnixSocket::sendData(void *buffer, size_t length, const 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;
+ 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::recv()
+{
+ Payload payload;
+ Header hdr;
+ int ret;
+
+ if (fd_ < 0)
+ return -ENOTCONN;
+
+ ret = ::recv(fd_, &hdr, sizeof(hdr), 0);
+ if (ret < 0) {
+ ret = -errno;
+ LOG(IPCUnixSocket, Error)
+ << "Failed to recv header: " << strerror(-ret);
+ return ret;
+ }
+
+ payload.data.resize(hdr.data);
+ payload.fds.resize(hdr.fds);
+
+ ret = recvData(payload.data.data(), hdr.data, payload.fds.data(), hdr.fds);
+ if (ret)
+ return ret;
+
+ payloadReceived.emit(payload);
+
+ 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;
+ 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)
+{
+ recv();
+}
+
+} /* namespace libcamera */
diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build
index 985aa7e8ab0eb6ce..45bd9d1793aa0b19 100644
--- a/src/libcamera/meson.build
+++ b/src/libcamera/meson.build
@@ -13,6 +13,7 @@ libcamera_sources = files([
'ipa_interface.cpp',
'ipa_manager.cpp',
'ipa_module.cpp',
+ 'ipc_unixsocket.cpp',
'log.cpp',
'media_device.cpp',
'media_object.cpp',
@@ -38,6 +39,7 @@ libcamera_headers = files([
'include/formats.h',
'include/ipa_manager.h',
'include/ipa_module.h',
+ 'include/ipc_unixsocket.h',
'include/log.h',
'include/media_device.h',
'include/media_object.h',
--
2.21.0
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