From ecc14a595809846cd09760d2c59b1fdfa9660ce8 Mon Sep 17 00:00:00 2001 From: Adam Langley Date: Wed, 11 May 2022 22:32:47 +0000 Subject: [PATCH] init: Add option to listen on sockets before starting service. Review note: Original change was a p-o-c by agl in https://r.android.com/2094350 which I think is actually production quality. I'm just taking it over so that he doesn't get spammed by any review comments as that's not a good use of his time. Needed for the hardware entropy daemon (see bug). Original commit message: If one needs to create a service that synchronously starts listening on a socket then there are currently no good options. The traditional UNIX solution is to have the service create the socket and then daemonise. In this situation, init could start the service with `exec_start` and yet not block forever because the service forks and exits. However, when the initial child process exits, init kills the daemon process: > init: Killed 1 additional processes from a oneshot process group for > service 'foo'. This is new behavior, previously child processes > would not be killed in this case. Next, there is a `socket` option for services and (although the documentation didn't nail this down), the socket is created synchronously by `start`. However, init doesn't call `listen` on the socket so, until the service starts listening on the socket itself, clients will get ECONNREFUSED. This this change adds a `+listen` option, similar to `+passcred` which allows a socket service to reliably handle connections. Bug: 243933553 Test: Started prng_seeder from init using the new listen flag Change-Id: I91b3b2b1fd38cc3d96e19e92b76c8e95788191d5 --- init/README.md | 7 ++++--- init/property_service.cpp | 3 ++- init/service_parser.cpp | 9 ++++++--- init/service_utils.cpp | 3 ++- init/service_utils.h | 1 + init/util.cpp | 7 +++++-- init/util.h | 4 ++-- 7 files changed, 22 insertions(+), 12 deletions(-) diff --git a/init/README.md b/init/README.md index fed81db15..7b3d32ac0 100644 --- a/init/README.md +++ b/init/README.md @@ -352,9 +352,10 @@ runs the service. `socket [ [ [ ] ] ]` > Create a UNIX domain socket named /dev/socket/_name_ and pass its fd to the - launched process. _type_ must be "dgram", "stream" or "seqpacket". _type_ - may end with "+passcred" to enable SO_PASSCRED on the socket. User and - group default to 0. 'seclabel' is the SELinux security context for the + launched process. The socket is created synchronously when the service starts. + _type_ must be "dgram", "stream" or "seqpacket". _type_ may end with "+passcred" + to enable SO_PASSCRED on the socket or "+listen" to synchronously make it a listening socket. + User and group default to 0. 'seclabel' is the SELinux security context for the socket. It defaults to the service security context, as specified by seclabel or computed based on the service executable file security context. For native executables see libcutils android\_get\_control\_socket(). diff --git a/init/property_service.cpp b/init/property_service.cpp index 7e925380f..c2ba8d559 100644 --- a/init/property_service.cpp +++ b/init/property_service.cpp @@ -1404,7 +1404,8 @@ void StartPropertyService(int* epoll_socket) { StartSendingMessages(); if (auto result = CreateSocket(PROP_SERVICE_NAME, SOCK_STREAM | SOCK_CLOEXEC | SOCK_NONBLOCK, - false, 0666, 0, 0, {}); + /*passcred=*/false, /*should_listen=*/false, 0666, /*uid=*/0, + /*gid=*/0, /*socketcon=*/{}); result.ok()) { property_set_fd = *result; } else { diff --git a/init/service_parser.cpp b/init/service_parser.cpp index 32c57c43c..24a202444 100644 --- a/init/service_parser.cpp +++ b/init/service_parser.cpp @@ -434,11 +434,14 @@ Result ServiceParser::ParseSocket(std::vector&& args) { << "' instead."; } - if (types.size() > 1) { - if (types.size() == 2 && types[1] == "passcred") { + for (size_t i = 1; i < types.size(); i++) { + if (types[i] == "passcred") { socket.passcred = true; + } else if (types[i] == "listen") { + socket.listen = true; } else { - return Error() << "Only 'passcred' may be used to modify the socket type"; + return Error() << "Unknown socket type decoration '" << types[i] + << "'. Known values are ['passcred', 'listen']"; } } diff --git a/init/service_utils.cpp b/init/service_utils.cpp index eed5c65db..d19f5eef5 100644 --- a/init/service_utils.cpp +++ b/init/service_utils.cpp @@ -168,7 +168,8 @@ void Descriptor::Publish() const { Result SocketDescriptor::Create(const std::string& global_context) const { const auto& socket_context = context.empty() ? global_context : context; - auto result = CreateSocket(name, type | SOCK_CLOEXEC, passcred, perm, uid, gid, socket_context); + auto result = CreateSocket(name, type | SOCK_CLOEXEC, passcred, listen, perm, uid, gid, + socket_context); if (!result.ok()) { return result.error(); } diff --git a/init/service_utils.h b/init/service_utils.h index 9b65dca74..65a2012ff 100644 --- a/init/service_utils.h +++ b/init/service_utils.h @@ -54,6 +54,7 @@ struct SocketDescriptor { int perm = 0; std::string context; bool passcred = false; + bool listen = false; bool persist = false; // Create() creates the named unix domain socket in /dev/socket and returns a Descriptor object. diff --git a/init/util.cpp b/init/util.cpp index 2d401425e..3d428557e 100644 --- a/init/util.cpp +++ b/init/util.cpp @@ -89,8 +89,8 @@ Result DecodeUid(const std::string& name) { * daemon. We communicate the file descriptor's value via the environment * variable ANDROID_SOCKET_ENV_PREFIX ("ANDROID_SOCKET_foo"). */ -Result CreateSocket(const std::string& name, int type, bool passcred, mode_t perm, uid_t uid, - gid_t gid, const std::string& socketcon) { +Result CreateSocket(const std::string& name, int type, bool passcred, bool should_listen, + mode_t perm, uid_t uid, gid_t gid, const std::string& socketcon) { if (!socketcon.empty()) { if (setsockcreatecon(socketcon.c_str()) == -1) { return ErrnoError() << "setsockcreatecon(\"" << socketcon << "\") failed"; @@ -145,6 +145,9 @@ Result CreateSocket(const std::string& name, int type, bool passcred, mode_ if (fchmodat(AT_FDCWD, addr.sun_path, perm, AT_SYMLINK_NOFOLLOW)) { return ErrnoError() << "Failed to fchmodat socket '" << addr.sun_path << "'"; } + if (should_listen && listen(fd, /* use OS maximum */ 1 << 30)) { + return ErrnoError() << "Failed to listen on socket '" << addr.sun_path << "'"; + } LOG(INFO) << "Created socket '" << addr.sun_path << "'" << ", mode " << std::oct << perm << std::dec diff --git a/init/util.h b/init/util.h index 0181bf073..e58e70e61 100644 --- a/init/util.h +++ b/init/util.h @@ -44,8 +44,8 @@ static const char kColdBootDoneProp[] = "ro.cold_boot_done"; extern void (*trigger_shutdown)(const std::string& command); -Result CreateSocket(const std::string& name, int type, bool passcred, mode_t perm, uid_t uid, - gid_t gid, const std::string& socketcon); +Result CreateSocket(const std::string& name, int type, bool passcred, bool should_listen, + mode_t perm, uid_t uid, gid_t gid, const std::string& socketcon); Result ReadFile(const std::string& path); Result WriteFile(const std::string& path, const std::string& content);