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SystemServer+LibCore: Implement socket takeover

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SystemServer can now create sockets on behalf of services before spawning any
of them, and pass the open socket fd as fd 3. CLocalServer gains a method to
complete the takeover and listen on the passed fd.

This is not used by any services at the moment.
This commit is contained in:
Sergey Bugaev 2019-11-26 19:27:21 +03:00 • committed by Andreas Kling
parent 396ad4d6b2
commit c9e21b2bcc
5 changed files with 146 additions and 10 deletions
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74
Libraries/LibCore/CLocalServer.cpp
View file

@ -3,18 +3,67 @@
#include <LibCore/CNotifier.h>
#include <stdio.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <unistd.h>
CLocalServer::CLocalServer(CObject* parent)
: CObject(parent)
{
m_fd = socket(AF_LOCAL, SOCK_STREAM | SOCK_NONBLOCK | SOCK_CLOEXEC, 0);
ASSERT(m_fd >= 0);
}
CLocalServer::~CLocalServer()
{
}
bool CLocalServer::take_over_from_system_server()
{
if (m_listening)
return false;
constexpr auto socket_takeover = "SOCKET_TAKEOVER";
if (getenv(socket_takeover)) {
dbg() << "Taking the socket over from SystemServer";
// Sanity check: it has to be a socket.
struct stat stat;
int rc = fstat(3, &stat);
if (rc == 0 && S_ISSOCK(stat.st_mode)) {
// The SystemServer has passed us the socket as fd 3,
// so use that instead of creating our own.
m_fd = 3;
// It had to be !CLOEXEC for obvious reasons, but we
// don't need it to be !CLOEXEC anymore, so set the
// CLOEXEC flag now.
fcntl(m_fd, F_SETFD, FD_CLOEXEC);
// We wouldn't want our children to think we're passing
// them a socket either, so unset the env variable.
unsetenv(socket_takeover);
m_listening = true;
setup_notifier();
return true;
} else {
if (rc != 0)
perror("fstat");
dbg() << "It's not a socket, what the heck??";
}
}
dbg() << "Failed to take the socket over from SystemServer";
return false;
}
void CLocalServer::setup_notifier()
{
m_notifier = CNotifier::construct(m_fd, CNotifier::Event::Read, this);
m_notifier->on_ready_to_read = [this] {
if (on_ready_to_accept)
on_ready_to_accept();
};
}
bool CLocalServer::listen(const String& address)
{
if (m_listening)
@ -22,20 +71,25 @@ bool CLocalServer::listen(const String& address)
int rc;
m_fd = socket(AF_LOCAL, SOCK_STREAM | SOCK_NONBLOCK | SOCK_CLOEXEC, 0);
ASSERT(m_fd >= 0);
auto socket_address = CSocketAddress::local(address);
auto un = socket_address.to_sockaddr_un();
rc = ::bind(m_fd, (const sockaddr*)&un, sizeof(un));
ASSERT(rc == 0);
if (rc < 0) {
perror("bind");
ASSERT_NOT_REACHED();
}
rc = ::listen(m_fd, 5);
ASSERT(rc == 0);
m_listening = true;
if (rc < 0) {
perror("listen");
ASSERT_NOT_REACHED();
}
m_notifier = CNotifier::construct(m_fd, CNotifier::Event::Read, this);
m_notifier->on_ready_to_read = [this] {
if (on_ready_to_accept)
on_ready_to_accept();
};
m_listening = true;
setup_notifier();
return true;
}