262 lines
11 KiB
C++
262 lines
11 KiB
C++
#include "TCPServer.h"
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#include "EPoll.h"
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#include "Exception.h"
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#include "Log.h"
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#include "TCPSession.h"
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#include <chrono>
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#include <vector>
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namespace core {
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TCPServer::TCPServer(EPoll &ePoll, IPAddress address, TLSInfo *tlsInfo, std::string delimiter, int depth, std::string text)
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: TCPSocket(ePoll, tlsInfo, text), commands(delimiter, depth) {
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// Wires the subscription (pub/sub) command set into this server's
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// own command dispatch - previously missing entirely here (the
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// subscriptions member existed but nothing ever routed these verbs
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// to it), so publish/subscribe/catalog/etc were unreachable on any
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// TCPServer built after the TLS work, even though SubscriptionManager
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// itself was still fully implemented.
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commands.add(subscriptions, "publish");
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commands.add(subscriptions, "unpublish");
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commands.add(subscriptions, "subscribe");
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commands.add(subscriptions, "unsubscribe");
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commands.add(subscriptions, "catalog");
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commands.add(subscriptions, "event");
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commands.add(subscriptions, "invite");
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setDescriptor(socket(AF_INET, SOCK_STREAM, 0));
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int yes = 1;
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setsockopt(getDescriptor(), SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(int));
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if (bind(getDescriptor(), address.getPointer(), address.addressLength) < 0)
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throw coreutils::Exception("Error on bind to socket: " + std::to_string(errno));
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// Was 20 - small enough that a burst of connection attempts
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// arriving faster than this process calls accept() (a port scan,
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// or just several real clients reconnecting around the same
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// moment) can fill the kernel's own backlog before the
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// application layer gets a chance to drain it, silently dropping
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// the overflow SYNs rather than queuing them. 128 gives real
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// bursts meaningfully more headroom; still bounded, not unlimited.
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if (listen(getDescriptor(), 128) < 0)
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throw coreutils::Exception("Error on listen to socket");
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// See isKnownListeningSocket()'s own doc comment - registers this
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// listening socket as safe for Thread::run() to dispatch to
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// directly, distinct from the shared_ptr-owned TCPSession registry.
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{
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std::lock_guard<std::mutex> guard(listeningSocketsMutex());
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listeningSockets().insert(this);
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}
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}
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TCPServer::~TCPServer() {
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coreutils::Log(coreutils::LOG_DEBUG_2) << "Closing server socket " << getDescriptor() << ".";
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close(getDescriptor());
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}
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void TCPServer::connectionRequest() {
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coreutils::Log(coreutils::LOG_DEBUG_2) << "Connection request is being received on socket " << getDescriptor() << ".";
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// Outside the lock.lock()/unlock() below, not nested inside it -
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// sweepStaleSessions() takes the same `lock` itself (see its own
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// comment), and this mutex isn't recursive.
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sweepStaleSessions();
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lock.lock();
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TCPSession *session = accept();
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// The shared_ptr constructed here IS the session's real, strong
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// ownership from now on (see sessions' own doc comment). A second
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// reference to the SAME shared_ptr (never a second, independent
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// std::shared_ptr<TCPSession>(session) call on the same raw
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// pointer - that would create a second, competing control block
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// and a guaranteed double-free) also goes into the tryGet()
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// registry, which is what Thread::run()'s epoll dispatch actually
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// uses to safely reach this object (see TCPSession::tryGet()'s
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// own comment on why).
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if (session) {
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auto sessionPtr = std::shared_ptr<TCPSession>(session);
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sessions.push_back(sessionPtr);
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TCPSession::registerLive(session, sessionPtr);
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}
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// Must run ON THE SESSION, not `this` (the listening server) - the
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// unqualified registerSocket()/acceptSocket() calls this replaced
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// built the SSL* handshake state on the SERVER's own TLS-base
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// member instead of the newly accepted session's, leaving every
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// session's own `ssl` uninitialized and segfaulting the first time
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// real data arrived on it (SSL_read() against a never-SSL_new()'d
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// pointer - confirmed via gdb). Sessions already correctly inherit
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// this server's SSL_CTX at construction (TCPSession's own
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// TLS(SSL_CTX*)-taking constructor) - performTLSHandshake() just
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// needed to actually be invoked on that object.
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if (session && tlsInfo)
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session->performTLSHandshake();
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lock.unlock();
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}
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void TCPServer::sweepStaleSessions() {
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// 30 seconds is generous for completing a TCP handshake plus a
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// TLS handshake plus sending a first real message over any real
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// network - deliberately not aimed at catching anything borderline,
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// only connections that never progressed at all.
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static const std::chrono::seconds GRACE_PERIOD(30);
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auto now = std::chrono::steady_clock::now();
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// Collect under `lock` (sessions is mutated elsewhere under the
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// same mutex - see its own doc comment), then drop the lock before
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// actually removing anything. removeFromSessionList() takes `lock`
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// itself for each call; calling it while still holding the guard
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// below would deadlock on this non-recursive mutex.
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std::vector<TCPSession *> stale;
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{
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std::lock_guard<std::mutex> guard(lock);
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for (auto &s : sessions)
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if (!s->hasReceivedData && (now - s->acceptedAt) > GRACE_PERIOD)
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stale.push_back(s.get());
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}
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for (auto *s : stale) {
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coreutils::Log(coreutils::LOG_DEBUG_2) << "Reaping stale, never-active session " << s->getDescriptor() << ".";
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removeFromSessionList(s);
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}
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}
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void TCPServer::receiveData(coreutils::ZString &buffer) {
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// See this override's own doc comment in TCPServer.h - the
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// listening socket always uses the plain read()/ENOTCONN detection
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// path, never TLS::receiveData(), regardless of whether this server
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// is TLS-configured.
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Socket::receiveData(buffer);
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}
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TCPSession * TCPServer::accept() {
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try
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{
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TCPSession *session = getSocketAccept(ePoll);
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session->setDescriptor(::accept(getDescriptor(), (struct sockaddr *)&session->ipAddress.addr, &session->ipAddress.addressLength));
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// if(blackList && blackList->contains(session->ipAddress.getClientAddress())) {
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// session->shutdown();
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// Log(LOG_WARN) << "Client at IP address " << session->ipAddress.getClientAddress() << " is blacklisted and was denied a connection.";
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// return NULL;
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// }
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// if(whiteList && !whiteList->contains(session->ipAddress.getClientAddress())) {
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// session->shutdown();
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// Log(LOG_WARN) << "Client at IP address " << session->ipAddress.getClientAddress() << " is not authorized and was denied a connection.";
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// return NULL;
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// }
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return session;
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}
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catch (coreutils::Exception e) {
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coreutils::Log(coreutils::LOG_EXCEPT) << "Major error on session initialization. Error is '" << e.text << "'.";
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}
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catch (...) {
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coreutils::Log(coreutils::LOG_EXCEPT) << "Unnspecified error on session initialization.";
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}
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return NULL;
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}
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void TCPServer::removeFromSessionList(TCPSession *session) {
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lock.lock();
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for (auto cursor = sessions.begin(); cursor < sessions.end(); ++cursor)
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if (cursor->get() == session)
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{
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// Drops the one strong-owning reference. If nothing else is
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// currently pin()'d to this session, the object is actually
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// destroyed right here, synchronously - same timing as
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// before this change for the common (no-contention) case.
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// If some other thread IS mid-call via its own pin()'d
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// shared_ptr right now, destruction is safely deferred until
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// that reference is released too, instead of the crash
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// (double-delete / use-after-free, confirmed live via
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// AddressSanitizer under concurrent load) that raw-pointer
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// ownership produced here before.
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sessions.erase(cursor);
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break;
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}
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lock.unlock();
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// Removes this pointer from the tryGet() lookup registry too (see
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// TCPSession::tryGet()'s own comment). Safe to do after releasing
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// `lock` and regardless of whether the erase() above was actually
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// the last reference: tryGet() correctly reports "gone" the moment
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// a session's real refcount hits zero, via the weak_ptr's own
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// expiration - this call is just tidying the registry map itself,
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// not something later correctness depends on.
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TCPSession::unregisterLive(session);
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}
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void TCPServer::sessionErrorHandler(std::string errorString, std::stringstream &out) {
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throw coreutils::Exception(errorString);
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}
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TCPSession * TCPServer::getSocketAccept(EPoll &ePoll) {
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return new TCPSession(ePoll, this);
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}
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void TCPServer::output(std::stringstream &out)
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{
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out << "Use the 'help' command to list the commands for this server." << std::endl;
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}
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int TCPServer::processCommand(coreutils::ZString &request, TCPSession &session)
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{
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// Was unguarded, like every other method below - `sessions` is
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// mutated under `lock` by connectionRequest()/removeFromSessionList()
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// (a session accepting or disconnecting on another thread), but
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// every READ of it here had no lock at all. Confirmed live via
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// dmesg: a real segfault at a stable, deterministic instruction
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// offset (same crash signature as the Subscription::subscribers
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// race fixed earlier this session, in SubscriptionManager.cpp) -
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// Socket::write() -> resetSocket() dereferencing a null EPoll
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// reference, consistent with iterating `sessions` while another
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// thread concurrently erased and freed one of its entries.
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// sendToAll() in particular is what most real gameplay broadcasts
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// (combat, position, chat) go through, so this is very likely the
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// actual dominant cause of that crash, not just the ItemDataBase
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// subscriber list this session's earlier fix addressed.
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std::lock_guard guard(lock);
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int sequence = 0;
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for (auto &sessionx : sessions)
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{
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session.out << "|" << ++sequence;
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sessionx->output(session.out);
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session.out << "|" << std::endl;
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}
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return 1;
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}
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void TCPServer::sendToAll(std::stringstream &data) {
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std::lock_guard guard(lock);
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for (auto &session : sessions)
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session->write(data.str());
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data.str("");
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}
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void TCPServer::sendToAll(std::stringstream &data, TCPSession &sender) {
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std::lock_guard guard(lock);
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for (auto &session : sessions)
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if (session.get() != &sender)
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session->write(data.str());
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data.str("");
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}
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void TCPServer::sendToAll(std::stringstream &data, TCPSession &sender, SessionFilter filter) {
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std::lock_guard guard(lock);
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for (auto &session : sessions)
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if (filter.test(*session))
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if (session.get() != &sender)
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session->write(data.str());
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data.str("");
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}
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std::shared_ptr<TCPSession> TCPServer::getSessionByAlias(void *alias) {
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coreutils::Log(coreutils::LOG_DEBUG_1) << alias;
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std::lock_guard guard(lock);
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for (auto &session : sessions)
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if (session->alias == alias)
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return session;
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return nullptr;
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}
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}
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