Rework transport protocol

Use a more simple tranport protocol for the realtime data. Use a piece
of shared memory and a socket where we use a 1byte read/write to trigger
remote actions. Also use a ringbuffer for events.

pinos/client/mem.c

@@ -0,0 +1,150 @@
+/* Pinos
+ * Copyright (C) 2016 Wim Taymans <wim.taymans@gmail.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 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
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#include <string.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <errno.h>
+#include <sys/mman.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <sys/syscall.h>
+
+#include <pinos/client/log.h>
+#include <pinos/client/mem.h>
+
+/*
+ * No glibc wrappers exist for memfd_create(2), so provide our own.
+ *
+ * Also define memfd fcntl sealing macros. While they are already
+ * defined in the kernel header file <linux/fcntl.h>, that file as
+ * a whole conflicts with the original glibc header <fnctl.h>.
+ */
+
+static inline int memfd_create(const char *name, unsigned int flags) {
+    return syscall(SYS_memfd_create, name, flags);
+}
+
+/* memfd_create(2) flags */
+
+#ifndef MFD_CLOEXEC
+#define MFD_CLOEXEC       0x0001U
+#endif
+
+#ifndef MFD_ALLOW_SEALING
+#define MFD_ALLOW_SEALING 0x0002U
+#endif
+
+/* fcntl() seals-related flags */
+
+#ifndef F_LINUX_SPECIFIC_BASE
+#define F_LINUX_SPECIFIC_BASE 1024
+#endif
+
+#ifndef F_ADD_SEALS
+#define F_ADD_SEALS (F_LINUX_SPECIFIC_BASE + 9)
+#define F_GET_SEALS (F_LINUX_SPECIFIC_BASE + 10)
+
+#define F_SEAL_SEAL     0x0001  /* prevent further seals from being set */
+#define F_SEAL_SHRINK   0x0002  /* prevent file from shrinking */
+#define F_SEAL_GROW     0x0004  /* prevent file from growing */
+#define F_SEAL_WRITE    0x0008  /* prevent writes */
+#endif
+
+
+#undef USE_MEMFD
+
+SpaResult
+pinos_memblock_alloc (PinosMemblockFlags  flags,
+                      size_t              size,
+                      PinosMemblock      *mem)
+{
+  if (mem == NULL || size == 0)
+    return SPA_RESULT_INVALID_ARGUMENTS;
+
+  mem->flags = flags;
+  mem->size = size;
+
+  if (flags & PINOS_MEMBLOCK_FLAG_WITH_FD) {
+#ifdef USE_MEMFD
+    mem->fd = memfd_create ("pinos-memfd", MFD_CLOEXEC | MFD_ALLOW_SEALING);
+    if (mem->fd == -1) {
+      pinos_log_error ("Failed to create memfd: %s\n", strerror (errno));
+      return SPA_RESULT_ERROR;
+    }
+#else
+    char filename[] = "/dev/shm/spa-tmpfile.XXXXXX";
+    mem->fd = mkostemp (filename, O_CLOEXEC);
+    if (mem->fd == -1) {
+      pinos_log_error ("Failed to create temporary file: %s\n", strerror (errno));
+      return SPA_RESULT_ERROR;
+    }
+    unlink (filename);
+#endif
+
+    if (ftruncate (mem->fd, size) < 0) {
+      pinos_log_warn ("Failed to truncate temporary file: %s", strerror (errno));
+      close (mem->fd);
+      return SPA_RESULT_ERROR;
+    }
+#ifdef USE_MEMFD
+    if (flags & PINOS_MEMBLOCK_FLAG_SEAL) {
+      unsigned int seals = F_SEAL_GROW | F_SEAL_SHRINK | F_SEAL_SEAL;
+      if (fcntl (mem->fd, F_ADD_SEALS, seals) == -1) {
+        pinos_log_warn ("Failed to add seals: %s", strerror (errno));
+      }
+    }
+#endif
+    if (flags & PINOS_MEMBLOCK_FLAG_MAP_READWRITE) {
+      int prot = 0;
+
+      if (flags & PINOS_MEMBLOCK_FLAG_MAP_READ)
+        prot |= PROT_READ;
+      if (flags & PINOS_MEMBLOCK_FLAG_MAP_WRITE)
+        prot |= PROT_WRITE;
+
+      mem->ptr = mmap (NULL, size, prot, MAP_SHARED, mem->fd, 0);
+    } else {
+      mem->ptr = NULL;
+    }
+  } else {
+    mem->ptr = malloc (size);
+    mem->fd = -1;
+  }
+  return SPA_RESULT_OK;
+}
+
+void
+pinos_memblock_free  (PinosMemblock *mem)
+{
+  if (mem == NULL)
+    return;
+
+  if (mem->flags & PINOS_MEMBLOCK_FLAG_WITH_FD) {
+    if (mem->ptr)
+      munmap (mem->ptr, mem->size);
+    if (mem->fd != -1)
+      close (mem->fd);
+  } else {
+    free (mem->ptr);
+  }
+  mem->ptr = NULL;
+  mem->fd = -1;
+}