Implement IPC::ChannelFactory, a class that accept()s on a UNIX socket.

ipc/unix_domain_socket_util.cc

Index: ipc/unix_domain_socket_util.cc
diff --git a/ipc/unix_domain_socket_util.cc b/ipc/unix_domain_socket_util.cc
new file mode 100644
index 0000000000000000000000000000000000000000..1611d8cc14211ba121bf056daf9b3045faab649b
--- /dev/null
+++ b/ipc/unix_domain_socket_util.cc
@@ -0,0 +1,171 @@
+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ipc/unix_domain_socket_util.h"
+
+#include <fcntl.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/un.h>
+#include <unistd.h>
+
+#include "base/file_util.h"
+#include "base/files/file_path.h"
+#include "base/logging.h"
+#include "base/posix/eintr_wrapper.h"
+
+namespace IPC {
+
+// Verify that kMaxPipeNameLength is a decent size.
+COMPILE_ASSERT(sizeof(((sockaddr_un*)0)->sun_path) >= kMaxPipeNameLength,
+               BAD_SUN_PATH_LENGTH);
+
+namespace {
+
+// returns fd (>= 0) on success, -1 on failure.
+int MakeUnixAddrForPath(const std::string& pipe_name,
+                        struct sockaddr_un* unix_addr,
+                        size_t* unix_addr_len) {
+  DCHECK_GT(pipe_name.length(), 0u);
+  DCHECK_LT(pipe_name.length(), kMaxPipeNameLength);
+
+  if (pipe_name.length() == 0 || pipe_name.length() >= kMaxPipeNameLength)
+    return -1;
+
+  // Create socket.
+  int fd = socket(AF_UNIX, SOCK_STREAM, 0);
+  if (fd < 0)
+    return -1;
+
+  // Make socket non-blocking
+  if (fcntl(fd, F_SETFL, O_NONBLOCK) == -1) {
+    PLOG(ERROR) << "fcntl(O_NONBLOCK) " << pipe_name;
+    if (HANDLE_EINTR(close(fd)) < 0)
+      PLOG(ERROR) << "close " << pipe_name;

[Mark Mentovai, 2013/02/28 04:57:56]

Wanna use your FD scoper here too? You’d need to return fd.release().

[jeremya, 2013/02/28 05:58:18]

Done.

+    return -1;
+  }
+
+  // Create unix_addr structure.
+  DCHECK(unix_addr);
+  memset(unix_addr, 0, sizeof(struct sockaddr_un));
+  unix_addr->sun_family = AF_UNIX;
+  int path_len = snprintf(unix_addr->sun_path, kMaxPipeNameLength,

[Mark Mentovai, 2013/02/28 04:57:56]

Why not just strncpy?

[jeremya, 2013/02/28 05:58:18]

Done. Do I need to check the return value? strncpy looks pretty straightforward.

+                          "%s", pipe_name.c_str());
+  DCHECK_EQ(static_cast<int>(pipe_name.length()), path_len);
+  *unix_addr_len = offsetof(struct sockaddr_un, sun_path) + path_len + 1;
+  return fd;
+}
+
+}  // namespace
+
+bool CreateServerUnixDomainSocket(const base::FilePath& pipe_path,
+                                  int* server_listen_fd) {
+  DCHECK(server_listen_fd);
+
+  std::string pipe_name = pipe_path.value();
+  base::FilePath pipe_dir = pipe_path.DirName();
+
+  struct sockaddr_un unix_addr;
+  size_t unix_addr_len;
+  int fd = MakeUnixAddrForPath(pipe_name, &unix_addr, &unix_addr_len);
+  if (fd < 0)
+    return false;
+  file_util::ScopedFD scoped_fd(&fd);

[Mark Mentovai, 2013/02/28 04:57:56]

…meaning fd will be closed when this function returns, even if it returns
success, although you’re giving it back to the caller in server_listen_fd?

You’ll want something like *server_listen_fd = fd.release().

[jeremya, 2013/02/28 05:58:18]

... yep. good catch, i found this independently after some searching for why it
suddenly stopped working. oops.

+
+  // Make sure the path we need exists.
+  if (!file_util::CreateDirectory(pipe_dir))
+    return false;
+
+  // Delete any old FS instances.
+  if (unlink(pipe_name.c_str()) < 0)
+    PLOG(ERROR) << "unlink " << pipe_name;
+
+  // Bind the socket.
+  if (bind(fd, reinterpret_cast<const sockaddr*>(&unix_addr),
+           unix_addr_len) != 0) {

[Mark Mentovai, 2013/02/28 04:57:56]

Sometimes you write <0 (on line 81), and sometimes != 0 (here and on line 93).
Be consistent.

[jeremya, 2013/02/28 05:58:18]

Done.

+    PLOG(ERROR) << "bind " << pipe_path.value();
+    return false;
+  }
+
+  // Start listening on the socket.
+  const int listen_queue_length = 1;
+  if (listen(fd, listen_queue_length) != 0) {
+    PLOG(ERROR) << "listen " << pipe_path.value();
+    return false;
+  }
+
+  *server_listen_fd = fd;
+  return true;
+}
+
+bool CreateClientUnixDomainSocket(const base::FilePath& pipe_path,
+                                  int* client_socket) {
+  DCHECK(client_socket);
+
+  std::string pipe_name = pipe_path.value();
+  base::FilePath pipe_dir = pipe_path.DirName();
+
+  struct sockaddr_un unix_addr;
+  size_t unix_addr_len;
+  int fd = MakeUnixAddrForPath(pipe_name, &unix_addr, &unix_addr_len);
+  if (fd < 0)
+    return false;
+  file_util::ScopedFD scoped_fd(&fd);

[Mark Mentovai, 2013/02/28 04:57:56]

Same thing here.

[jeremya, 2013/02/28 05:58:18]

Done.

+
+  if (HANDLE_EINTR(connect(fd, reinterpret_cast<sockaddr*>(&unix_addr),
+                           unix_addr_len)) != 0) {
+    PLOG(ERROR) << "connect " << pipe_path.value();
+    return false;
+  }
+
+  *client_socket = fd;
+  return true;
+}
+
+bool GetPeerEuid(int fd, uid_t* client_euid) {
+#if defined(OS_MACOSX) || defined(OS_OPENBSD)
+  uid_t peer_euid;
+  gid_t peer_gid;
+  if (getpeereid(fd, &peer_euid, &peer_gid) != 0) {
+    PLOG(ERROR) << "getpeereid " << fd;
+    return false;
+  }
+  *client_euid = peer_euid;
+  return true;
+#elif defined(OS_SOLARIS)
+  return false;
+#else
+  struct ucred cred;
+  socklen_t cred_len = sizeof(cred);
+  if (getsockopt(fd, SOL_SOCKET, SO_PEERCRED, &cred, &cred_len) != 0) {
+    PLOG(ERROR) << "getsockopt " << fd;
+    return false;
+  }
+  if (static_cast<unsigned>(cred_len) < sizeof(cred)) {
+    NOTREACHED() << "Truncated ucred from SO_PEERCRED?";
+    return false;
+  }
+  *client_euid = cred.uid;
+  return true;
+#endif
+}
+
+bool ServerAcceptConnection(int server_listen_fd, int* server_socket) {
+  DCHECK(server_socket);
+
+  int accept_fd = HANDLE_EINTR(accept(server_listen_fd, NULL, 0));
+  if (accept_fd < 0)
+    return false;
+  if (fcntl(accept_fd, F_SETFL, O_NONBLOCK) == -1) {
+    PLOG(ERROR) << "fcntl(O_NONBLOCK) " << accept_fd;
+    if (HANDLE_EINTR(close(accept_fd)) < 0)
+      PLOG(ERROR) << "close " << accept_fd;
+    return false;
+  }
+
+  *server_socket = accept_fd;
+  return true;
+}
+
+}  // namespace IPC

[Mark Mentovai, 2013/02/28 04:57:56]

These functions look like they’d be pretty easy to write a couple of simple
tests for.