X-Git-Url: https://git.sesse.net/?p=cubemap;a=blobdiff_plain;f=server.cpp;h=69615e705aba182b9fbbf168c56ea5c78931695c;hp=31e5c0a31da327bc80499c543bbb4dee932b74bb;hb=50651c954803c1941e6ad1bb494712891c18f7d2;hpb=97bdb597d4847308ce9d6982505b56a3a09e930b

diff --git a/server.cpp b/server.cpp
index 31e5c0a..852ecdd 100644
--- a/server.cpp
+++ b/server.cpp
@@ -1,90 +1,988 @@
+#include <assert.h>
+#include <errno.h>
+#include <netinet/in.h>
+#include <pthread.h>
+#include <stdint.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
-#include <stdint.h>
-#include <assert.h>
-#include <arpa/inet.h>
-#include <curl/curl.h>
+#include <sys/epoll.h>
+#include <sys/sendfile.h>
 #include <sys/socket.h>
-#include <pthread.h>
 #include <sys/types.h>
-#include <sys/ioctl.h>
-#include <sys/epoll.h>
-#include <errno.h>
-#include <vector>
-#include <string>
+#include <unistd.h>
+#include <algorithm>
 #include <map>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "tlse.h"
 
-#include "metacube.h"
+#include "acceptor.h"
+#include "accesslog.h"
+#include "log.h"
+#include "metacube2.h"
+#include "parse.h"
 #include "server.h"
-#include "mutexlock.h"
+#include "state.pb.h"
+#include "stream.h"
+#include "util.h"
+
+#ifndef SO_MAX_PACING_RATE
+#define SO_MAX_PACING_RATE 47
+#endif
 
 using namespace std;
 
-Server::Server()
+extern AccessLogThread *access_log;
+
+namespace {
+
+inline bool is_equal(timespec a, timespec b)
+{
+	return a.tv_sec == b.tv_sec &&
+	       a.tv_nsec == b.tv_nsec;
+}
+
+inline bool is_earlier(timespec a, timespec b)
 {
-	pthread_mutex_init(&mutex, NULL);
+	if (a.tv_sec != b.tv_sec)
+		return a.tv_sec < b.tv_sec;
+	return a.tv_nsec < b.tv_nsec;
+}
+
+}  // namespace
 
+Server::Server()
+{
 	epoll_fd = epoll_create(1024);  // Size argument is ignored.
 	if (epoll_fd == -1) {
-		perror("epoll_fd");
+		log_perror("epoll_fd");
 		exit(1);
 	}
 }
 
-void Server::run()
+Server::~Server()
 {
-	pthread_t thread;
-	pthread_create(&thread, NULL, Server::do_work_thunk, this);
+	safe_close(epoll_fd);
 }
 
-void *Server::do_work_thunk(void *arg)
+vector<ClientStats> Server::get_client_stats() const
 {
-	Server *server = static_cast<Server *>(arg);
-	server->do_work();
-	return NULL;
+	vector<ClientStats> ret;
+
+	lock_guard<mutex> lock(mu);
+	for (const auto &fd_and_client : clients) {
+		ret.push_back(fd_and_client.second.get_stats());
+	}
+	return ret;
 }
 
 void Server::do_work()
 {
-	for ( ;; ) {
-		MutexLock lock(&mutex);
-		printf("server thread running\n");
-		sleep(1);
+	while (!should_stop()) {
+		// Wait until there's activity on at least one of the fds,
+		// or 20 ms (about one frame at 50 fps) has elapsed.
+		//
+		// We could in theory wait forever and rely on wakeup()
+		// from add_client_deferred() and add_data_deferred(),
+		// but wakeup is a pretty expensive operation, and the
+		// two threads might end up fighting over a lock, so it's
+		// seemingly (much) more efficient to just have a timeout here.
+		int nfds = epoll_pwait(epoll_fd, events, EPOLL_MAX_EVENTS, EPOLL_TIMEOUT_MS, &sigset_without_usr1_block);
+		if (nfds == -1 && errno != EINTR) {
+			log_perror("epoll_wait");
+			exit(1);
+		}
+
+		lock_guard<mutex> lock(mu);  // We release the mutex between iterations.
+	
+		process_queued_data();
+
+		// Process each client where we have socket activity.
+		for (int i = 0; i < nfds; ++i) {
+			Client *client = reinterpret_cast<Client *>(events[i].data.ptr);
+
+			if (events[i].events & (EPOLLERR | EPOLLRDHUP | EPOLLHUP)) {
+				close_client(client);
+				continue;
+			}
+
+			process_client(client);
+		}
+
+		// Process each client where its stream has new data,
+		// even if there was no socket activity.
+		for (unique_ptr<Stream> &stream : streams) {
+			vector<Client *> to_process;
+			swap(stream->to_process, to_process);
+			for (Client *client : to_process) {
+				process_client(client);
+			}
+		}
+
+		// Finally, go through each client to see if it's timed out
+		// in the READING_REQUEST state. (Seemingly there are clients
+		// that can hold sockets up for days at a time without sending
+		// anything at all.)
+		timespec timeout_time;
+		if (clock_gettime(CLOCK_MONOTONIC_COARSE, &timeout_time) == -1) {
+			log_perror("clock_gettime(CLOCK_MONOTONIC_COARSE)");
+			continue;
+		}
+		timeout_time.tv_sec -= REQUEST_READ_TIMEOUT_SEC;
+		while (!clients_ordered_by_connect_time.empty()) {
+			const pair<timespec, int> &connect_time_and_fd = clients_ordered_by_connect_time.front();
+
+			// See if we have reached the end of clients to process.
+			if (is_earlier(timeout_time, connect_time_and_fd.first)) {
+				break;
+			}
+
+			// If this client doesn't exist anymore, just ignore it
+			// (it was deleted earlier).
+			auto client_it = clients.find(connect_time_and_fd.second);
+			if (client_it == clients.end()) {
+				clients_ordered_by_connect_time.pop();
+				continue;
+			}
+			Client *client = &client_it->second;
+			if (!is_equal(client->connect_time, connect_time_and_fd.first)) {
+				// Another client has taken this fd in the meantime.
+				clients_ordered_by_connect_time.pop();
+				continue;
+			}
+
+			if (client->state != Client::READING_REQUEST) {
+				// Only READING_REQUEST can time out.
+				clients_ordered_by_connect_time.pop();
+				continue;
+			}
+
+			// OK, it timed out.
+			close_client(client);
+			clients_ordered_by_connect_time.pop();
+		}
+	}
+}
+
+CubemapStateProto Server::serialize()
+{
+	// We don't serialize anything queued, so empty the queues.
+	process_queued_data();
+
+	// Set all clients in a consistent state before serializing
+	// (ie., they have no remaining lost data). Otherwise, increasing
+	// the backlog could take clients into a newly valid area of the backlog,
+	// sending a stream of zeros instead of skipping the data as it should.
+	//
+	// TODO: Do this when clients are added back from serialized state instead;
+	// it would probably be less wasteful.
+	for (auto &fd_and_client : clients) {
+		skip_lost_data(&fd_and_client.second);
 	}
+
+	CubemapStateProto serialized;
+	for (const auto &fd_and_client : clients) {
+		serialized.add_clients()->MergeFrom(fd_and_client.second.serialize());
+	}
+	for (unique_ptr<Stream> &stream : streams) {
+		serialized.add_streams()->MergeFrom(stream->serialize());
+	}
+	return serialized;
 }
-	
-void Server::add_client(int sock)
+
+void Server::add_client_deferred(int sock, Acceptor *acceptor)
+{
+	lock_guard<mutex> lock(queued_clients_mutex);
+	queued_add_clients.push_back(std::make_pair(sock, acceptor));
+}
+
+void Server::add_client(int sock, Acceptor *acceptor)
 {
-	MutexLock lock(&mutex);
-	Client new_client;
-	new_client.state = Client::READING_REQUEST;
-	new_client.header_bytes_sent = 0;
-	new_client.bytes_sent = 0;
+	const bool is_tls = acceptor->is_tls();
+	auto inserted = clients.insert(make_pair(sock, Client(sock)));
+	assert(inserted.second == true);  // Should not already exist.
+	Client *client_ptr = &inserted.first->second;
 
-	clients.insert(make_pair(sock, new_client));
+	// Connection timestamps must be nondecreasing. I can't find any guarantee
+	// that even the monotonic clock can't go backwards by a small amount
+	// (think switching between CPUs with non-synchronized TSCs), so if
+	// this actually should happen, we hack around it by fudging
+	// connect_time.
+	if (!clients_ordered_by_connect_time.empty() &&
+	    is_earlier(client_ptr->connect_time, clients_ordered_by_connect_time.back().first)) {
+		client_ptr->connect_time = clients_ordered_by_connect_time.back().first;
+	}
+	clients_ordered_by_connect_time.push(make_pair(client_ptr->connect_time, sock));
 
 	// Start listening on data from this socket.
 	epoll_event ev;
-	ev.events = EPOLLIN;
-	ev.data.fd = sock;
+	if (is_tls) {
+		// Even in the initial state (READING_REQUEST), TLS needs to
+		// send data for the handshake, and thus might end up needing
+		// to know about EPOLLOUT.
+		ev.events = EPOLLIN | EPOLLOUT | EPOLLET | EPOLLRDHUP;
+	} else {
+		// EPOLLOUT will be added once we go out of READING_REQUEST.
+		ev.events = EPOLLIN | EPOLLET | EPOLLRDHUP;
+	}
+	ev.data.ptr = client_ptr;
 	if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, sock, &ev) == -1) {
-		perror("epoll_ctl(EPOLL_CTL_ADD)");
+		log_perror("epoll_ctl(EPOLL_CTL_ADD)");
+		exit(1);
+	}
+
+	if (is_tls) {
+		assert(tls_server_contexts.count(acceptor));
+		client_ptr->tls_context = tls_accept(tls_server_contexts[acceptor]);
+		if (client_ptr->tls_context == nullptr) {
+			log(ERROR, "tls_accept() failed");
+			close_client(client_ptr);
+			return;
+		}
+		tls_make_exportable(client_ptr->tls_context, 1);
+	}
+
+	process_client(client_ptr);
+}
+
+void Server::add_client_from_serialized(const ClientProto &client)
+{
+	lock_guard<mutex> lock(mu);
+	Stream *stream;
+	int stream_index = lookup_stream_by_url(client.url());
+	if (stream_index == -1) {
+		assert(client.state() != Client::SENDING_DATA);
+		stream = nullptr;
+	} else {
+		stream = streams[stream_index].get();
+	}
+	auto inserted = clients.insert(make_pair(client.sock(), Client(client, stream)));
+	assert(inserted.second == true);  // Should not already exist.
+	Client *client_ptr = &inserted.first->second;
+
+	// Connection timestamps must be nondecreasing.
+	assert(clients_ordered_by_connect_time.empty() ||
+	       !is_earlier(client_ptr->connect_time, clients_ordered_by_connect_time.back().first));
+	clients_ordered_by_connect_time.push(make_pair(client_ptr->connect_time, client.sock()));
+
+	// Start listening on data from this socket.
+	epoll_event ev;
+	if (client.state() == Client::READING_REQUEST) {
+		// See the corresponding comment in Server::add_client().
+		if (client.has_tls_context()) {
+			ev.events = EPOLLIN | EPOLLOUT | EPOLLET | EPOLLRDHUP;
+		} else {
+			ev.events = EPOLLIN | EPOLLET | EPOLLRDHUP;
+		}
+	} else {
+		// If we don't have more data for this client, we'll be putting it into
+		// the sleeping array again soon.
+		ev.events = EPOLLOUT | EPOLLET | EPOLLRDHUP;
+	}
+	ev.data.ptr = client_ptr;
+	if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, client.sock(), &ev) == -1) {
+		log_perror("epoll_ctl(EPOLL_CTL_ADD)");
 		exit(1);
 	}
+
+	if (client_ptr->state == Client::WAITING_FOR_KEYFRAME ||
+	    client_ptr->state == Client::PREBUFFERING ||
+	    (client_ptr->state == Client::SENDING_DATA &&
+	     client_ptr->stream_pos == client_ptr->stream->bytes_received)) {
+		client_ptr->stream->put_client_to_sleep(client_ptr);
+	} else {
+		process_client(client_ptr);
+	}
+}
+
+int Server::lookup_stream_by_url(const string &url) const
+{
+	map<string, int>::const_iterator stream_url_it = stream_url_map.find(url);
+	if (stream_url_it == stream_url_map.end()) {
+		return -1;
+	}
+	return stream_url_it->second;
+}
+
+int Server::add_stream(const string &url, size_t backlog_size, size_t prebuffering_bytes, Stream::Encoding encoding, Stream::Encoding src_encoding)
+{
+	lock_guard<mutex> lock(mu);
+	stream_url_map.insert(make_pair(url, streams.size()));
+	streams.emplace_back(new Stream(url, backlog_size, prebuffering_bytes, encoding, src_encoding));
+	return streams.size() - 1;
+}
+
+int Server::add_stream_from_serialized(const StreamProto &stream, int data_fd)
+{
+	lock_guard<mutex> lock(mu);
+	stream_url_map.insert(make_pair(stream.url(), streams.size()));
+	streams.emplace_back(new Stream(stream, data_fd));
+	return streams.size() - 1;
 }
 	
-void Server::add_stream(const string &stream_id)
+void Server::set_backlog_size(int stream_index, size_t new_size)
+{
+	lock_guard<mutex> lock(mu);
+	assert(stream_index >= 0 && stream_index < ssize_t(streams.size()));
+	streams[stream_index]->set_backlog_size(new_size);
+}
+
+void Server::set_prebuffering_bytes(int stream_index, size_t new_amount)
+{
+	lock_guard<mutex> lock(mu);
+	assert(stream_index >= 0 && stream_index < ssize_t(streams.size()));
+	streams[stream_index]->prebuffering_bytes = new_amount;
+}
+	
+void Server::set_encoding(int stream_index, Stream::Encoding encoding)
+{
+	lock_guard<mutex> lock(mu);
+	assert(stream_index >= 0 && stream_index < ssize_t(streams.size()));
+	streams[stream_index]->encoding = encoding;
+}
+
+void Server::set_src_encoding(int stream_index, Stream::Encoding encoding)
 {
-	// TODO
+	lock_guard<mutex> lock(mu);
+	assert(stream_index >= 0 && stream_index < ssize_t(streams.size()));
+	streams[stream_index]->src_encoding = encoding;
 }
 	
-void Server::set_header(const string &stream_id, const string &header)
+void Server::set_header(int stream_index, const string &http_header, const string &stream_header)
 {
-	// TODO
-	printf("got header! %lu bytes\n", header.size());
+	lock_guard<mutex> lock(mu);
+	assert(stream_index >= 0 && stream_index < ssize_t(streams.size()));
+	streams[stream_index]->http_header = http_header;
+
+	if (stream_header != streams[stream_index]->stream_header) {
+		// We cannot start at any of the older starting points anymore,
+		// since they'd get the wrong header for the stream (not to mention
+		// that a changed header probably means the stream restarted,
+		// which means any client starting on the old one would probably
+		// stop playing properly at the change point). Next block
+		// should be a suitable starting point (if not, something is
+		// pretty strange), so it will fill up again soon enough.
+		streams[stream_index]->suitable_starting_points.clear();
+	}
+	streams[stream_index]->stream_header = stream_header;
 }
 	
-void Server::add_data(const string &stream_id, const char *data, size_t bytes)
+void Server::set_pacing_rate(int stream_index, uint32_t pacing_rate)
 {
-	// TODO
+	lock_guard<mutex> lock(mu);
+	assert(clients.empty());
+	assert(stream_index >= 0 && stream_index < ssize_t(streams.size()));
+	streams[stream_index]->pacing_rate = pacing_rate;
+}
+
+void Server::add_gen204(const std::string &url, const std::string &allow_origin)
+{
+	lock_guard<mutex> lock(mu);
+	assert(clients.empty());
+	ping_url_map[url] = allow_origin;
+}
+
+void Server::create_tls_context_for_acceptor(const Acceptor *acceptor)
+{
+	assert(acceptor->is_tls());
+
+	bool is_server = true;
+	TLSContext *server_context = tls_create_context(is_server, TLS_V12);
+
+	const string &cert = acceptor->get_certificate_chain();
+	int num_cert = tls_load_certificates(server_context, reinterpret_cast<const unsigned char *>(cert.data()), cert.size());
+	assert(num_cert > 0);  // Should have been checked by config earlier.
+
+	const string &key = acceptor->get_private_key();
+	int num_key = tls_load_private_key(server_context, reinterpret_cast<const unsigned char *>(key.data()), key.size());
+	assert(num_key > 0);  // Should have been checked by config earlier.
+
+	tls_server_contexts.insert(make_pair(acceptor, server_context));
+}
+
+void Server::add_data_deferred(int stream_index, const char *data, size_t bytes, uint16_t metacube_flags)
+{
+	assert(stream_index >= 0 && stream_index < ssize_t(streams.size()));
+	streams[stream_index]->add_data_deferred(data, bytes, metacube_flags);
+}
+
+// See the .h file for postconditions after this function.	
+void Server::process_client(Client *client)
+{
+	switch (client->state) {
+	case Client::READING_REQUEST: {
+		if (client->tls_context != nullptr) {
+			if (send_pending_tls_data(client)) {
+				// send_pending_tls_data() hit postconditions #1 or #4.
+				return;
+			}
+		}
+
+read_request_again:
+		// Try to read more of the request.
+		char buf[1024];
+		int ret;
+		if (client->tls_context == nullptr) {
+			ret = read_nontls_data(client, buf, sizeof(buf));
+			if (ret == -1) {
+				// read_nontls_data() hit postconditions #1 or #2.
+				return;
+			}
+		} else {
+			ret = read_tls_data(client, buf, sizeof(buf));
+			if (ret == -1) {
+				// read_tls_data() hit postconditions #1, #2 or #4.
+				return;
+			}
+		}
+
+		RequestParseStatus status = wait_for_double_newline(&client->request, buf, ret);
+	
+		switch (status) {
+		case RP_OUT_OF_SPACE:
+			log(WARNING, "[%s] Client sent overlong request!", client->remote_addr.c_str());
+			close_client(client);
+			return;
+		case RP_NOT_FINISHED_YET:
+			// OK, we don't have the entire header yet. Fine; we'll get it later.
+			// See if there's more data for us.
+			goto read_request_again;
+		case RP_EXTRA_DATA:
+			log(WARNING, "[%s] Junk data after request!", client->remote_addr.c_str());
+			close_client(client);
+			return;
+		case RP_FINISHED:
+			break;
+		}
+
+		assert(status == RP_FINISHED);
+
+		if (client->tls_context && !client->in_ktls_mode && tls_established(client->tls_context)) {
+			// We're ready to enter kTLS mode, unless we still have some
+			// handshake data to send (which then must be sent as non-kTLS).
+			if (send_pending_tls_data(client)) {
+				// send_pending_tls_data() hit postconditions #1 or #4.
+				return;
+			}
+			ret = tls_make_ktls(client->tls_context, client->sock);
+			if (ret < 0) {
+				log_tls_error("tls_make_ktls", ret);
+				close_client(client);
+				return;
+			}
+			client->in_ktls_mode = true;
+		}
+
+		int error_code = parse_request(client);
+		if (error_code == 200) {
+			construct_header(client);
+		} else if (error_code == 204) {
+			construct_204(client);
+		} else {
+			construct_error(client, error_code);
+		}
+
+		// We've changed states, so fall through.
+		assert(client->state == Client::SENDING_SHORT_RESPONSE ||
+		       client->state == Client::SENDING_HEADER);
+	}
+	case Client::SENDING_SHORT_RESPONSE:
+	case Client::SENDING_HEADER: {
+sending_header_or_short_response_again:
+		int ret;
+		do {
+			ret = write(client->sock,
+		                    client->header_or_short_response.data() + client->header_or_short_response_bytes_sent,
+				    client->header_or_short_response.size() - client->header_or_short_response_bytes_sent);
+		} while (ret == -1 && errno == EINTR);
+
+		if (ret == -1 && errno == EAGAIN) {
+			// We're out of socket space, so now we're at the “low edge” of epoll's
+			// edge triggering. epoll will tell us when there is more room, so for now,
+			// just return.
+			// This is postcondition #4.
+			return;
+		}
+
+		if (ret == -1) {
+			// Error! Postcondition #1.
+			log_perror("write");
+			close_client(client);
+			return;
+		}
+		
+		client->header_or_short_response_bytes_sent += ret;
+		assert(client->header_or_short_response_bytes_sent <= client->header_or_short_response.size());
+
+		if (client->header_or_short_response_bytes_sent < client->header_or_short_response.size()) {
+			// We haven't sent all yet. Fine; go another round.
+			goto sending_header_or_short_response_again;
+		}
+
+		// We're done sending the header or error! Clear it to release some memory.
+		client->header_or_short_response.clear();
+
+		if (client->state == Client::SENDING_SHORT_RESPONSE) {
+			// We're done sending the error, so now close.	
+			// This is postcondition #1.
+			close_client(client);
+			return;
+		}
+
+		Stream *stream = client->stream;
+		if (client->stream_pos == size_t(-2)) {
+			// Start sending from the beginning of the backlog.
+			client->stream_pos = min<size_t>(
+			    stream->bytes_received - stream->backlog_size,
+			    0);
+			client->state = Client::SENDING_DATA;
+			goto sending_data;
+		} else if (stream->prebuffering_bytes == 0) {
+			// Start sending from the first keyframe we get. In other
+			// words, we won't send any of the backlog, but we'll start
+			// sending immediately as we get the next keyframe block.
+			// Note that this is functionally identical to the next if branch,
+			// except that we save a binary search.
+			client->stream_pos = stream->bytes_received;
+			client->state = Client::WAITING_FOR_KEYFRAME;
+		} else {
+			// We're not going to send anything to the client before we have
+			// N bytes. However, this wait might be boring; we can just as well
+			// use it to send older data if we have it. We use lower_bound()
+			// so that we are conservative and never add extra latency over just
+			// waiting (assuming CBR or nearly so); otherwise, we could want e.g.
+			// 100 kB prebuffer but end up sending a 10 MB GOP.
+			deque<size_t>::const_iterator starting_point_it =
+				lower_bound(stream->suitable_starting_points.begin(),
+					    stream->suitable_starting_points.end(),
+					    stream->bytes_received - stream->prebuffering_bytes);
+			if (starting_point_it == stream->suitable_starting_points.end()) {
+				// None found. Just put us at the end, and then wait for the
+				// first keyframe to appear.
+				client->stream_pos = stream->bytes_received;
+				client->state = Client::WAITING_FOR_KEYFRAME;
+			} else {
+				client->stream_pos = *starting_point_it;
+				client->state = Client::PREBUFFERING;
+				goto prebuffering;
+			}
+		}
+		// Fall through.
+	}
+	case Client::WAITING_FOR_KEYFRAME: {
+		Stream *stream = client->stream;
+		if (stream->suitable_starting_points.empty() ||
+		    client->stream_pos > stream->suitable_starting_points.back()) {
+			// We haven't received a keyframe since this stream started waiting,
+			// so keep on waiting for one.
+			// This is postcondition #3.
+			stream->put_client_to_sleep(client);
+			return;
+		}
+		client->stream_pos = stream->suitable_starting_points.back();
+		client->state = Client::PREBUFFERING;
+		// Fall through.
+	}
+	case Client::PREBUFFERING: {
+prebuffering:
+		Stream *stream = client->stream;
+		size_t bytes_to_send = stream->bytes_received - client->stream_pos;
+		assert(bytes_to_send <= stream->backlog_size);
+		if (bytes_to_send < stream->prebuffering_bytes) {
+			// We don't have enough bytes buffered to start this client yet.
+			// This is postcondition #3.
+			stream->put_client_to_sleep(client);
+			return;
+		}
+		client->state = Client::SENDING_DATA;
+		// Fall through.
+	}
+	case Client::SENDING_DATA: {
+sending_data:
+		skip_lost_data(client);
+		Stream *stream = client->stream;
+
+sending_data_again:
+		size_t bytes_to_send = stream->bytes_received - client->stream_pos;
+		assert(bytes_to_send <= stream->backlog_size);
+		if (bytes_to_send == 0) {
+			return;
+		}
+
+		// See if we need to split across the circular buffer.
+		bool more_data = false;
+		if ((client->stream_pos % stream->backlog_size) + bytes_to_send > stream->backlog_size) {
+			bytes_to_send = stream->backlog_size - (client->stream_pos % stream->backlog_size);
+			more_data = true;
+		}
+
+		ssize_t ret;
+		do {
+			off_t offset = client->stream_pos % stream->backlog_size;
+			ret = sendfile(client->sock, stream->data_fd, &offset, bytes_to_send);
+		} while (ret == -1 && errno == EINTR);
+
+		if (ret == -1 && errno == EAGAIN) {
+			// We're out of socket space, so return; epoll will wake us up
+			// when there is more room.
+			// This is postcondition #4.
+			return;
+		}
+		if (ret == -1) {
+			// Error, close; postcondition #1.
+			log_perror("sendfile");
+			close_client(client);
+			return;
+		}
+		client->stream_pos += ret;
+		client->bytes_sent += ret;
+
+		if (client->stream_pos == stream->bytes_received) {
+			// We don't have any more data for this client, so put it to sleep.
+			// This is postcondition #3.
+			stream->put_client_to_sleep(client);
+		} else if (more_data && size_t(ret) == bytes_to_send) {
+			goto sending_data_again;
+		}
+		break;
+	}
+	default:
+		assert(false);
+	}
+}
+
+bool Server::send_pending_tls_data(Client *client)
+{
+	// See if there's data from the TLS library to write.
+	if (client->tls_data_to_send == nullptr) {
+		client->tls_data_to_send = tls_get_write_buffer(client->tls_context, &client->tls_data_left_to_send);
+		if (client->tls_data_to_send == nullptr) {
+			// Really no data to send.
+			return false;
+		}
+	}
+
+send_data_again:
+	int ret;
+	do {
+		ret = write(client->sock, client->tls_data_to_send, client->tls_data_left_to_send);
+	} while (ret == -1 && errno == EINTR);
+	assert(ret < 0 || size_t(ret) <= client->tls_data_left_to_send);
+
+	if (ret == -1 && errno == EAGAIN) {
+		// We're out of socket space, so now we're at the “low edge” of epoll's
+		// edge triggering. epoll will tell us when there is more room, so for now,
+		// just return.
+		// This is postcondition #4.
+		return true;
+	}
+	if (ret == -1) {
+		// Error! Postcondition #1.
+		log_perror("write");
+		close_client(client);
+		return true;
+	}
+	if (ret > 0 && size_t(ret) == client->tls_data_left_to_send) {
+		// All data has been sent, so we don't need to go to sleep.
+		tls_buffer_clear(client->tls_context);
+		client->tls_data_to_send = nullptr;
+		return false;
+	}
+
+	// More data to send, so try again.
+	client->tls_data_to_send += ret;
+	client->tls_data_left_to_send -= ret;
+	goto send_data_again;
+}
+
+int Server::read_nontls_data(Client *client, char *buf, size_t max_size)
+{
+	int ret;
+	do {
+	        ret = read(client->sock, buf, max_size);
+	} while (ret == -1 && errno == EINTR);
+
+	if (ret == -1 && errno == EAGAIN) {
+	        // No more data right now. Nothing to do.
+	        // This is postcondition #2.
+	        return -1;
+	}
+	if (ret == -1) {
+	        log_perror("read");
+	        close_client(client);
+	        return -1;
+	}
+	if (ret == 0) {
+	        // OK, the socket is closed.
+	        close_client(client);
+	        return -1;
+	}
+
+	return ret;
+}
+
+int Server::read_tls_data(Client *client, char *buf, size_t max_size)
+{
+read_again:
+	int ret;
+	do {
+		ret = read(client->sock, buf, max_size);
+	} while (ret == -1 && errno == EINTR);
+
+	if (ret == -1 && errno == EAGAIN) {
+		// No more data right now. Nothing to do.
+		// This is postcondition #2.
+		return -1;
+	}
+	if (ret == -1) {
+		log_perror("read");
+		close_client(client);
+		return -1;
+	}
+	if (ret == 0) {
+		// OK, the socket is closed.
+		close_client(client);
+		return -1;
+	}
+
+	// Give it to the TLS library.
+	int err = tls_consume_stream(client->tls_context, reinterpret_cast<const unsigned char *>(buf), ret, nullptr);
+	if (err < 0) {
+		log_tls_error("tls_consume_stream", err);
+		close_client(client);
+		return -1;
+	}
+	if (err == 0) {
+		// Not consumed any data. See if we can read more.
+		goto read_again;
+	}
+
+	// Read any decrypted data available for us. (We can reuse buf, since it's free now.)
+	ret = tls_read(client->tls_context, reinterpret_cast<unsigned char *>(buf), max_size);
+	if (ret == 0) {
+		// No decrypted data for us yet, but there might be some more handshaking
+		// to send. Do that if needed, then look for more data.
+		if (send_pending_tls_data(client)) {
+			// send_pending_tls_data() hit postconditions #1 or #4.
+			return -1;
+		}
+		goto read_again;
+	}
+	if (ret < 0) {
+		log_tls_error("tls_read", ret);
+		close_client(client);
+		return -1;
+	}
+
+	assert(ret > 0);
+	return ret;
+}
+
+// See if there's some data we've lost. Ideally, we should drop to a block boundary,
+// but resync will be the mux's problem.
+void Server::skip_lost_data(Client *client)
+{
+	Stream *stream = client->stream;
+	if (stream == nullptr) {
+		return;
+	}
+	size_t bytes_to_send = stream->bytes_received - client->stream_pos;
+	if (bytes_to_send > stream->backlog_size) {
+		size_t bytes_lost = bytes_to_send - stream->backlog_size;
+		client->stream_pos = stream->bytes_received - stream->backlog_size;
+		client->bytes_lost += bytes_lost;
+		++client->num_loss_events;
+	}
+}
+
+int Server::parse_request(Client *client)
+{
+	vector<string> lines = split_lines(client->request);
+	if (lines.empty()) {
+		return 400;  // Bad request (empty).
+	}
+
+	// Parse the headers, for logging purposes.
+	// TODO: Case-insensitivity.
+	multimap<string, string> headers = extract_headers(lines, client->remote_addr);
+	multimap<string, string>::const_iterator referer_it = headers.find("Referer");
+	if (referer_it != headers.end()) {
+		client->referer = referer_it->second;
+	}
+	multimap<string, string>::const_iterator user_agent_it = headers.find("User-Agent");
+	if (user_agent_it != headers.end()) {
+		client->user_agent = user_agent_it->second;
+	}
+
+	vector<string> request_tokens = split_tokens(lines[0]);
+	if (request_tokens.size() < 2) {
+		return 400;  // Bad request (empty).
+	}
+	if (request_tokens[0] != "GET") {
+		return 400;  // Should maybe be 405 instead?
+	}
+
+	string url = request_tokens[1];
+	client->url = url;
+	if (url.size() > 8 && url.find("?backlog") == url.size() - 8) {
+		client->stream_pos = -2;
+		url = url.substr(0, url.size() - 8);
+	} else {
+		client->stream_pos = -1;
+	}
+
+	map<string, int>::const_iterator stream_url_map_it = stream_url_map.find(url);
+	if (stream_url_map_it == stream_url_map.end()) {
+		map<string, string>::const_iterator ping_url_map_it = ping_url_map.find(url);
+		if (ping_url_map_it == ping_url_map.end()) {
+			return 404;  // Not found.
+		} else {
+			return 204;  // No error.
+		}
+	}
+
+	Stream *stream = streams[stream_url_map_it->second].get();
+	if (stream->http_header.empty()) {
+		return 503;  // Service unavailable.
+	}
+
+	client->stream = stream;
+	if (setsockopt(client->sock, SOL_SOCKET, SO_MAX_PACING_RATE, &client->stream->pacing_rate, sizeof(client->stream->pacing_rate)) == -1) {
+		if (client->stream->pacing_rate != ~0U) {
+			log_perror("setsockopt(SO_MAX_PACING_RATE)");
+		}
+	}
+	client->request.clear();
+
+	return 200;  // OK!
+}
+
+void Server::construct_header(Client *client)
+{
+	Stream *stream = client->stream;
+	if (stream->encoding == Stream::STREAM_ENCODING_RAW) {
+		client->header_or_short_response = stream->http_header +
+			"\r\n" +
+			stream->stream_header;
+	} else if (stream->encoding == Stream::STREAM_ENCODING_METACUBE) {
+		client->header_or_short_response = stream->http_header +
+			"Content-encoding: metacube\r\n" +
+			"\r\n";
+		if (!stream->stream_header.empty()) {
+			metacube2_block_header hdr;
+			memcpy(hdr.sync, METACUBE2_SYNC, sizeof(hdr.sync));
+			hdr.size = htonl(stream->stream_header.size());
+			hdr.flags = htons(METACUBE_FLAGS_HEADER);
+			hdr.csum = htons(metacube2_compute_crc(&hdr));
+			client->header_or_short_response.append(
+				string(reinterpret_cast<char *>(&hdr), sizeof(hdr)));
+		}
+		client->header_or_short_response.append(stream->stream_header);
+	} else {
+		assert(false);
+	}
+
+	// Switch states.
+	client->state = Client::SENDING_HEADER;
+	change_epoll_events(client, EPOLLOUT | EPOLLET | EPOLLRDHUP);
+}
+	
+void Server::construct_error(Client *client, int error_code)
+{
+	char error[256];
+	snprintf(error, 256, "HTTP/1.0 %d Error\r\nContent-type: text/plain\r\n\r\nSomething went wrong. Sorry.\r\n",
+		error_code);
+	client->header_or_short_response = error;
+
+	// Switch states.
+	client->state = Client::SENDING_SHORT_RESPONSE;
+	change_epoll_events(client, EPOLLOUT | EPOLLET | EPOLLRDHUP);
+}
+
+void Server::construct_204(Client *client)
+{
+	map<string, string>::const_iterator ping_url_map_it = ping_url_map.find(client->url);
+	assert(ping_url_map_it != ping_url_map.end());
+
+	if (ping_url_map_it->second.empty()) {
+		client->header_or_short_response =
+			"HTTP/1.0 204 No Content\r\n"
+			"\r\n";
+	} else {
+		char response[256];
+		snprintf(response, 256,
+		         "HTTP/1.0 204 No Content\r\n"
+		         "Access-Control-Allow-Origin: %s\r\n"
+			 "\r\n",
+			 ping_url_map_it->second.c_str());
+		client->header_or_short_response = response;
+	}
+
+	// Switch states.
+	client->state = Client::SENDING_SHORT_RESPONSE;
+	change_epoll_events(client, EPOLLOUT | EPOLLET | EPOLLRDHUP);
+}
+
+template<class T>
+void delete_from(vector<T> *v, T elem)
+{
+	typename vector<T>::iterator new_end = remove(v->begin(), v->end(), elem);
+	v->erase(new_end, v->end());
+}
+	
+void Server::close_client(Client *client)
+{
+	if (epoll_ctl(epoll_fd, EPOLL_CTL_DEL, client->sock, nullptr) == -1) {
+		log_perror("epoll_ctl(EPOLL_CTL_DEL)");
+		exit(1);
+	}
+
+	// This client could be sleeping, so we'll need to fix that. (Argh, O(n).)
+	if (client->stream != nullptr) {
+		delete_from(&client->stream->sleeping_clients, client);
+		delete_from(&client->stream->to_process, client);
+	}
+
+	if (client->tls_context) {
+		tls_destroy_context(client->tls_context);
+	}
+
+	// Log to access_log.
+	access_log->write(client->get_stats());
+
+	// Bye-bye!
+	safe_close(client->sock);
+
+	clients.erase(client->sock);
+}
+
+void Server::change_epoll_events(Client *client, uint32_t events)
+{
+	epoll_event ev;
+	ev.events = events;
+	ev.data.ptr = client;
+
+	if (epoll_ctl(epoll_fd, EPOLL_CTL_MOD, client->sock, &ev) == -1) {
+		log_perror("epoll_ctl(EPOLL_CTL_MOD)");
+		exit(1);
+	}
+}
+
+void Server::process_queued_data()
+{
+	{
+		lock_guard<mutex> lock(queued_clients_mutex);
+
+		for (const pair<int, Acceptor *> &id_and_acceptor : queued_add_clients) {
+			add_client(id_and_acceptor.first, id_and_acceptor.second);
+		}
+		queued_add_clients.clear();
+	}
+
+	for (unique_ptr<Stream> &stream : streams) {
+		stream->process_queued_data();
+	}
 }