init: clean up file / socket descriptor creation

clang-tidy hinted that some of this code wasn't right.  Looking
deeper, there is really not much related to file and socket
descriptors, except that they're published in similar ways to the
environment.  All of the abstraction into a 'Descriptor' class takes
us further away from specifying what we really mean.

This removes that abstraction, adds stricter checks and better errors
for parsing init scripts, reports sockets and files that are unable to
be acquired before exec, and updates the README.md for the passcred
option.

Test: build, logd (uses files and sockets) works
Change-Id: I59e611e95c85bdbefa779ef69b32b9dd4ee203e2

1 files changed, 47 insertions, 0 deletions

diff --git a/init/service_utils.cpp b/init/service_utils.cpp
index 34aa8370f..836145d62 100644
--- a/init/service_utils.cpp
+++ b/init/service_utils.cpp
@@ -27,9 +27,12 @@
 #include <android-base/stringprintf.h>
 #include <android-base/strings.h>
 #include <android-base/unique_fd.h>
+#include <cutils/android_get_control_file.h>
+#include <cutils/sockets.h>
 #include <processgroup/processgroup.h>
 
 #include "mount_namespace.h"
+#include "util.h"
 
 using android::base::GetProperty;
 using android::base::StartsWith;
@@ -135,8 +138,52 @@ void OpenConsole(const std::string& console) {
     dup2(fd, 2);
 }
 
+void PublishDescriptor(const std::string& key, const std::string& name, int fd) {
+    std::string published_name = key + name;
+    for (auto& c : published_name) {
+        c = isalnum(c) ? c : '_';
+    }
+
+    std::string val = std::to_string(fd);
+    setenv(published_name.c_str(), val.c_str(), 1);
+}
+
 }  // namespace
 
+Result<void> SocketDescriptor::CreateAndPublish(const std::string& global_context) const {
+    const auto& socket_context = context.empty() ? global_context : context;
+    auto result = CreateSocket(name, type, passcred, perm, uid, gid, socket_context);
+    if (!result) {
+        return result.error();
+    }
+
+    PublishDescriptor(ANDROID_SOCKET_ENV_PREFIX, name, *result);
+
+    return {};
+}
+
+Result<void> FileDescriptor::CreateAndPublish() const {
+    int flags = (type == "r") ? O_RDONLY : (type == "w") ? O_WRONLY : O_RDWR;
+
+    // Make sure we do not block on open (eg: devices can chose to block on carrier detect).  Our
+    // intention is never to delay launch of a service for such a condition.  The service can
+    // perform its own blocking on carrier detect.
+    android::base::unique_fd fd(TEMP_FAILURE_RETRY(open(name.c_str(), flags | O_NONBLOCK)));
+
+    if (fd < 0) {
+        return ErrnoError() << "Failed to open file '" << name << "'";
+    }
+
+    // Fixup as we set O_NONBLOCK for open, the intent for fd is to block reads.
+    fcntl(fd, F_SETFL, flags);
+
+    LOG(INFO) << "Opened file '" << name << "', flags " << flags;
+
+    PublishDescriptor(ANDROID_FILE_ENV_PREFIX, name, fd.release());
+
+    return {};
+}
+
 Result<void> EnterNamespaces(const NamespaceInfo& info, const std::string& name, bool pre_apexd) {
     for (const auto& [nstype, path] : info.namespaces_to_enter) {
         if (auto result = EnterNamespace(nstype, path.c_str()); !result) {