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41d03670d67a36d9cc084a8c333b07cd81e71cfc
psopeeps-newserv/src/IPStackSimulator.cc
T
Martin Michelsen a7e3d4853a add session replay functions
2022-07-01 11:02:47 -07:00

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#include "IPStackSimulator.hh"
#include <stdint.h>
#include <string.h>
#include <netinet/in.h>
#include <event2/buffer.h>
#include <event2/bufferevent.h>
#include <event2/listener.h>
#ifndef PHOSG_WINDOWS
#include <arpa/inet.h>
#else
#include <winsock2.h>
#include <ws2tcpip.h>
#endif
#include <string>
#include <phosg/Network.hh>
#include <phosg/Random.hh>
#include <phosg/Time.hh>
#include "Loggers.hh"
#include "IPFrameInfo.hh"
#include "DNSServer.hh"
using namespace std;
static const size_t DEFAULT_RESEND_PUSH_USECS = 200000; // 200ms
// Note: these functions exist because seq nums are allowed to wrap around the
// 32-bit integer space by design. We have to do the subtraction before the
// comparison to allow integer overflow to occur if needed.
static inline bool seq_num_less(uint32_t a, uint32_t b) {
return (a - b) & 0x80000000;
}
static inline bool seq_num_less_or_equal(uint32_t a, uint32_t b) {
return (a == b) || seq_num_less(a, b);
}
static inline bool seq_num_greater(uint32_t a, uint32_t b) {
return (b - a) & 0x80000000;
}
static __attribute__((unused)) inline bool seq_num_greater_or_equal(uint32_t a, uint32_t b) {
return (a == b) || seq_num_greater(a, b);
}
string IPStackSimulator::str_for_ipv4_netloc(uint32_t addr, uint16_t port) {
be_uint32_t be_addr = addr;
char addr_str[INET_ADDRSTRLEN];
if (!inet_ntop(AF_INET, &be_addr, addr_str, INET_ADDRSTRLEN)) {
return string_printf("<UNKNOWN>:%hu", port);
} else {
return string_printf("%s:%hu", addr_str, port);
}
}
string IPStackSimulator::str_for_tcp_connection(shared_ptr<const IPClient> c,
const IPClient::TCPConnection& conn) {
uint64_t key = IPStackSimulator::tcp_conn_key_for_connection(conn);
string server_netloc_str = str_for_ipv4_netloc(conn.server_addr, conn.server_port);
string client_netloc_str = str_for_ipv4_netloc(c->ipv4_addr, conn.client_port);
int fd = bufferevent_getfd(c->bev.get());
return string_printf("%d+%016" PRIX64 " (%s -> %s)",
fd, key, client_netloc_str.c_str(), server_netloc_str.c_str());
}
IPStackSimulator::IPStackSimulator(
std::shared_ptr<struct event_base> base,
std::shared_ptr<ServerState> state)
: base(base),
state(state),
pcap_text_log_file(state->ip_stack_debug ? fopen("IPStackSimulator-Log.txt", "wt") : nullptr) {
memset(this->host_mac_address_bytes, 0x90, 6);
memset(this->broadcast_mac_address_bytes, 0xFF, 6);
}
IPStackSimulator::~IPStackSimulator() {
if (this->pcap_text_log_file) {
fclose(this->pcap_text_log_file);
}
}
void IPStackSimulator::listen(const std::string& socket_path) {
this->add_socket(::listen(socket_path, 0, SOMAXCONN));
}
void IPStackSimulator::listen(const std::string& addr, int port) {
this->add_socket(::listen(addr, port, SOMAXCONN));
}
void IPStackSimulator::listen(int port) {
this->add_socket(::listen("", port, SOMAXCONN));
}
void IPStackSimulator::add_socket(int fd) {
this->listeners.emplace(
evconnlistener_new(
this->base.get(),
IPStackSimulator::dispatch_on_listen_accept,
this,
LEV_OPT_REUSEABLE,
0,
fd),
evconnlistener_free);
}
uint32_t IPStackSimulator::connect_address_for_remote_address(uint32_t remote_addr) {
// Use an address not on the same subnet as the client, so that PSO Plus and
// Episode III will think they're talking to a remote network and won't reject
// the connection.
if ((remote_addr & 0xFF000000) != 0x23000000) {
return 0x23232323;
} else {
return 0x24242424;
}
}
IPStackSimulator::IPClient::IPClient(struct bufferevent* bev)
: bev(bev, bufferevent_free), ipv4_addr(0) {
memset(this->mac_addr, 0, 6);
}
static void flush_and_free_bufferevent(struct bufferevent* bev) {
bufferevent_flush(bev, EV_READ | EV_WRITE, BEV_FINISHED);
bufferevent_free(bev);
}
IPStackSimulator::IPClient::TCPConnection::TCPConnection()
: server_bev(nullptr, flush_and_free_bufferevent),
pending_data(evbuffer_new(), evbuffer_free),
resend_push_event(nullptr, event_free) { }
void IPStackSimulator::dispatch_on_listen_accept(
struct evconnlistener* listener, evutil_socket_t fd,
struct sockaddr *address, int socklen, void* ctx) {
reinterpret_cast<IPStackSimulator*>(ctx)->on_listen_accept(
listener, fd, address, socklen);
}
void IPStackSimulator::on_listen_accept(struct evconnlistener* listener,
evutil_socket_t fd, struct sockaddr*, int) {
int listen_fd = evconnlistener_get_fd(listener);
ip_stack_simulator_log.info("Client fd %d connected via fd %d", fd, listen_fd);
struct bufferevent *bev = bufferevent_socket_new(this->base.get(), fd,
BEV_OPT_CLOSE_ON_FREE | BEV_OPT_DEFER_CALLBACKS);
shared_ptr<IPClient> c(new IPClient(bev));
c->sim = this;
this->bev_to_client.emplace(make_pair(bev, c));
bufferevent_setcb(bev, &IPStackSimulator::dispatch_on_client_input, nullptr,
&IPStackSimulator::dispatch_on_client_error, this);
bufferevent_enable(bev, EV_READ | EV_WRITE);
}
void IPStackSimulator::dispatch_on_listen_error(
struct evconnlistener* listener, void* ctx) {
reinterpret_cast<IPStackSimulator*>(ctx)->on_listen_error(listener);
}
void IPStackSimulator::on_listen_error(struct evconnlistener* listener) {
int err = EVUTIL_SOCKET_ERROR();
ip_stack_simulator_log.error("Failure on listening socket %d: %d (%s)",
evconnlistener_get_fd(listener), err, evutil_socket_error_to_string(err));
event_base_loopexit(this->base.get(), nullptr);
}
void IPStackSimulator::dispatch_on_client_input(
struct bufferevent* bev, void* ctx) {
reinterpret_cast<IPStackSimulator*>(ctx)->on_client_input(bev);
}
void IPStackSimulator::on_client_input(struct bufferevent* bev) {
struct evbuffer* buf = bufferevent_get_input(bev);
shared_ptr<IPClient> c;
try {
c = this->bev_to_client.at(bev);
} catch (const out_of_range&) {
size_t bytes = evbuffer_get_length(buf);
ip_stack_simulator_log.warning("Ignoring data received from unregistered client (0x%zX bytes)",
bytes);
evbuffer_drain(buf, bytes);
return;
}
while (evbuffer_get_length(buf) >= 2) {
uint16_t frame_size;
evbuffer_copyout(buf, &frame_size, 2);
if (evbuffer_get_length(buf) < static_cast<size_t>(frame_size + 2)) {
break; // No complete frame available; done for now
}
evbuffer_drain(buf, 2);
string frame(frame_size, '\0');
evbuffer_remove(buf, frame.data(), frame.size());
try {
this->on_client_frame(c, frame);
} catch (const exception& e) {
if (this->state->ip_stack_debug) {
ip_stack_simulator_log.warning("Failed to process client frame: %s", e.what());
print_data(stderr, frame);
}
}
}
}
void IPStackSimulator::dispatch_on_client_error(
struct bufferevent* bev, short events, void* ctx) {
reinterpret_cast<IPStackSimulator*>(ctx)->on_client_error(bev, events);
}
void IPStackSimulator::on_client_error(struct bufferevent* bev,
short events) {
if (events & BEV_EVENT_ERROR) {
int err = EVUTIL_SOCKET_ERROR();
ip_stack_simulator_log.warning("Client caused error %d (%s)", err,
evutil_socket_error_to_string(err));
}
if (events & (BEV_EVENT_EOF | BEV_EVENT_ERROR)) {
ip_stack_simulator_log.info("Client fd %d disconnected", bufferevent_getfd(bev));
this->bev_to_client.erase(bev);
}
}
void IPStackSimulator::on_client_frame(
shared_ptr<IPClient> c, const string& frame) {
if (this->state->ip_stack_debug) {
fputc('\n', stderr);
ip_stack_simulator_log.info("Client sent frame");
print_data(stderr, frame);
}
this->log_frame(frame);
FrameInfo fi(frame);
if (this->state->ip_stack_debug) {
string fi_header = fi.header_str();
ip_stack_simulator_log.info("Frame header: %s", fi_header.c_str());
}
if (fi.arp) {
this->on_client_arp_frame(c, fi);
} else if (fi.ipv4) {
uint16_t expected_ipv4_checksum = fi.computed_ipv4_header_checksum();
if (fi.ipv4->checksum != expected_ipv4_checksum) {
throw runtime_error(string_printf(
"IPv4 header checksum is incorrect (%04hX expected, %04hX received)",
expected_ipv4_checksum, fi.ipv4->checksum.load()));
}
if (memcmp(fi.ether->src_mac, c->mac_addr, 6)) {
throw runtime_error("client sent IPv4 packet from different MAC address");
}
if (fi.ipv4->src_addr != c->ipv4_addr) {
throw runtime_error("client sent IPv4 packet from different IPv4 address");
}
if (fi.udp) {
uint16_t expected_udp_checksum = fi.computed_udp4_checksum();
if (fi.udp->checksum != expected_udp_checksum) {
throw runtime_error(string_printf(
"UDP checksum is incorrect (%04hX expected, %04hX received)",
expected_udp_checksum, fi.udp->checksum.load()));
}
this->on_client_udp_frame(c, fi);
} else if (fi.tcp) {
uint16_t expected_tcp_checksum = fi.computed_tcp4_checksum();
if (fi.tcp->checksum != expected_tcp_checksum) {
throw runtime_error(string_printf(
"TCP checksum is incorrect (%04hX expected, %04hX received)",
expected_tcp_checksum, fi.tcp->checksum.load()));
}
this->on_client_tcp_frame(c, fi);
} else {
throw runtime_error("frame uses unsupported IPv4 protocol");
}
} else {
throw runtime_error("frame is not IPv4");
}
}
void IPStackSimulator::on_client_arp_frame(
shared_ptr<IPClient> c, const FrameInfo& fi) {
if (fi.arp->hwaddr_len != 6 ||
fi.arp->paddr_len != 4 ||
fi.arp->hardware_type != 0x0001 ||
fi.arp->protocol_type != 0x0800) {
throw runtime_error("unsupported ARP parameters");
}
if (fi.payload_size < 20) {
throw runtime_error("ARP payload too small");
}
// Populate the client's addresses if needed
if (!memcmp(c->mac_addr, "\0\0\0\0\0\0", 6)) {
memcpy(c->mac_addr, fi.ether->src_mac, 6);
}
if (c->ipv4_addr == 0) {
c->ipv4_addr = *reinterpret_cast<const be_uint32_t*>(
reinterpret_cast<const uint8_t*>(fi.payload) + 6);
}
EthernetHeader r_ether;
memcpy(r_ether.dest_mac, fi.ether->src_mac, 6);
memcpy(r_ether.src_mac, this->host_mac_address_bytes, 6);
r_ether.protocol = fi.ether->protocol;
ARPHeader r_arp;
r_arp.hardware_type = fi.arp->hardware_type;
r_arp.protocol_type = fi.arp->protocol_type;
r_arp.hwaddr_len = 6;
r_arp.paddr_len = 4;
r_arp.operation = 0x0002;
// The incoming payload is:
// uint8_t src_mac[6]; // MAC address of client
// uint8_t src_ip[4]; // IP address of client
// uint8_t dest_mac[6]; // MAC address of host (all zeroes)
// uint8_t dest_ip[4]; // IP address of host
// The outgoing payload is:
// uint8_t dest_mac[6]; // MAC address of host (from configuration)
// uint8_t dest_ip[4]; // IP address of host
// uint8_t src_mac[6]; // MAC address of client
// uint8_t src_ip[4]; // IP address of client
const char* payload_bytes = reinterpret_cast<const char*>(fi.payload);
uint8_t r_payload[20];
memcpy(&r_payload[0], this->host_mac_address_bytes, 6);
memcpy(&r_payload[6], payload_bytes + 16, 4);
memcpy(&r_payload[10], payload_bytes, 10);
struct evbuffer* out_buf = bufferevent_get_output(c->bev.get());
uint16_t frame_size = sizeof(r_ether) + sizeof(r_arp) + sizeof(r_payload);
evbuffer_add(out_buf, &frame_size, 2);
evbuffer_add(out_buf, &r_ether, sizeof(r_ether));
evbuffer_add(out_buf, &r_arp, sizeof(r_arp));
evbuffer_add(out_buf, r_payload, sizeof(r_payload));
if (this->state->ip_stack_debug) {
ip_stack_simulator_log.info("Sending ARP response");
}
if (this->pcap_text_log_file) {
StringWriter w;
w.write(&r_ether, sizeof(r_ether));
w.write(&r_arp, sizeof(r_arp));
w.write(r_payload, sizeof(r_payload));
this->log_frame(w.str());
}
}
void IPStackSimulator::on_client_udp_frame(
shared_ptr<IPClient> c, const FrameInfo& fi) {
// We only implement the DNS server here
if (fi.udp->dest_port != 53) {
throw runtime_error("UDP packet is not DNS");
}
if (fi.payload_size < 0x0C) {
throw runtime_error("DNS payload too small");
}
EthernetHeader r_ether;
memcpy(r_ether.dest_mac, fi.ether->src_mac, 6);
memcpy(r_ether.src_mac, this->host_mac_address_bytes, 6);
r_ether.protocol = fi.ether->protocol;
IPv4Header r_ipv4;
r_ipv4.version_ihl = 0x45;
r_ipv4.tos = 0;
// r_ipv4.size filled in later
r_ipv4.id = 0;
r_ipv4.frag_offset = 0;
r_ipv4.ttl = 20; // TODO: Does this value actually matter? Looks like it just has to be nonzero
r_ipv4.protocol = 17; // UDP
// r_ipv4.checksum filled in later
r_ipv4.src_addr = fi.ipv4->dest_addr;
r_ipv4.dest_addr = fi.ipv4->src_addr;
UDPHeader r_udp;
r_udp.src_port = fi.udp->dest_port;
r_udp.dest_port = fi.udp->src_port;
// r_udp.size filled in later
// r_udp.checksum filled in later
uint32_t resolved_address = this->connect_address_for_remote_address(c->ipv4_addr);
string r_data = DNSServer::response_for_query(
fi.payload, fi.payload_size, resolved_address);
r_ipv4.size = sizeof(IPv4Header) + sizeof(UDPHeader) + r_data.size();
r_udp.size = sizeof(UDPHeader) + r_data.size();
r_ipv4.checksum = FrameInfo::computed_ipv4_header_checksum(r_ipv4);
r_udp.checksum = FrameInfo::computed_udp4_checksum(
r_ipv4, r_udp, r_data.data(), r_data.size());
struct evbuffer* out_buf = bufferevent_get_output(c->bev.get());
if (this->state->ip_stack_debug) {
string remote_str = this->str_for_ipv4_netloc(fi.ipv4->src_addr, fi.udp->src_port);
ip_stack_simulator_log.info("Sending DNS response to %s", remote_str.c_str());
}
uint16_t frame_size = sizeof(r_ether) + sizeof(r_ipv4) + sizeof(r_udp) + r_data.size();
evbuffer_add(out_buf, &frame_size, 2);
evbuffer_add(out_buf, &r_ether, sizeof(r_ether));
evbuffer_add(out_buf, &r_ipv4, sizeof(r_ipv4));
evbuffer_add(out_buf, &r_udp, sizeof(r_udp));
evbuffer_add(out_buf, r_data.data(), r_data.size());
if (this->pcap_text_log_file) {
StringWriter w;
w.write(&r_ether, sizeof(r_ether));
w.write(&r_ipv4, sizeof(r_ipv4));
w.write(&r_udp, sizeof(r_udp));
w.write(r_data.data(), r_data.size());
this->log_frame(w.str());
}
}
uint64_t IPStackSimulator::tcp_conn_key_for_connection(
const IPClient::TCPConnection& conn) {
return (static_cast<uint64_t>(conn.server_addr) << 32) |
(static_cast<uint64_t>(conn.server_port) << 16) |
static_cast<uint64_t>(conn.client_port);
}
uint64_t IPStackSimulator::tcp_conn_key_for_client_frame(
const IPv4Header& ipv4, const TCPHeader& tcp) {
return (static_cast<uint64_t>(ipv4.dest_addr) << 32) |
(static_cast<uint64_t>(tcp.dest_port) << 16) |
static_cast<uint64_t>(tcp.src_port);
}
uint64_t IPStackSimulator::tcp_conn_key_for_client_frame(const FrameInfo& fi) {
if (!fi.ipv4 || !fi.tcp) {
throw logic_error("tcp_conn_key_for_frame called on non-TCP frame");
}
return IPStackSimulator::tcp_conn_key_for_client_frame(*fi.ipv4, *fi.tcp);
}
void IPStackSimulator::on_client_tcp_frame(
shared_ptr<IPClient> c, const FrameInfo& fi) {
if (this->state->ip_stack_debug) {
ip_stack_simulator_log.info("Client sent TCP frame (seq=%08" PRIX32 ", ack=%08" PRIX32 ")",
fi.tcp->seq_num.load(), fi.tcp->ack_num.load());
}
if (fi.tcp->flags & (TCPHeader::Flag::NS | TCPHeader::Flag::CWR |
TCPHeader::Flag::ECE | TCPHeader::Flag::URG)) {
throw runtime_error("unsupported flag in TCP packet");
}
if (fi.tcp->flags & TCPHeader::Flag::SYN) {
// We never make connections back to the client, so we should never receive
// a SYN+ACK. Essentially, no other flags should be set in any received SYN.
if ((fi.tcp->flags & 0x0FFF) != TCPHeader::Flag::SYN) {
throw runtime_error("TCP SYN contains extra flags");
}
StringReader options_r(fi.tcp + 1, fi.tcp_options_size);
size_t max_frame_size = 1400;
while (!options_r.eof()) {
uint8_t option = options_r.get_u8();
uint8_t option_size = (option < 2) ? 1 : options_r.get_u8();
switch (option) {
case 0: // End of options list
options_r.go(options_r.size());
break;
case 1: // No option (padding)
break;
case 2: // Max segment size
if (option_size != 4) {
throw runtime_error("incorrect size for TCP max frame size option");
}
max_frame_size = options_r.get_u16b();
break;
case 3: // Window scale (ignored)
if (option_size != 3) {
throw runtime_error("incorrect size for TCP window scale option");
}
options_r.skip(option_size);
break;
case 4: // Selective ACK supported (ignored)
if (option_size != 2) {
throw runtime_error("incorrect size for TCP selective ACK supported option");
}
break;
case 5: // Selective ACK (ignored)
options_r.skip(option_size - 2);
break;
case 8: // Timestamps (ignored)
if (option_size != 10) {
throw runtime_error("incorrect size for TCP timestamps option");
}
options_r.skip(8);
break;
default:
throw runtime_error("invalid TCP option");
}
}
uint64_t key = this->tcp_conn_key_for_client_frame(fi);
auto emplace_ret = c->tcp_connections.emplace(key, IPClient::TCPConnection());
auto& conn = emplace_ret.first->second;
string conn_str;
if (emplace_ret.second) {
// Connection is new; initialize it
conn.client = c;
conn.resend_push_event.reset(event_new(this->base.get(), -1, EV_TIMEOUT,
&IPStackSimulator::dispatch_on_resend_push, &conn));
conn.server_addr = fi.ipv4->dest_addr;
conn.server_port = fi.tcp->dest_port;
conn.client_port = fi.tcp->src_port;
conn.next_client_seq = fi.tcp->seq_num + 1;
conn.acked_server_seq = random_object<uint32_t>();
conn.resend_push_usecs = DEFAULT_RESEND_PUSH_USECS;
conn.awaiting_first_ack = true;
conn.max_frame_size = max_frame_size;
conn_str = this->str_for_tcp_connection(c, conn);
if (this->state->ip_stack_debug) {
ip_stack_simulator_log.info("Client opened TCP connection %s (acked_server_seq=%08" PRIX32 ", next_client_seq=%08" PRIX32 ")",
conn_str.c_str(), conn.acked_server_seq, conn.next_client_seq);
} else {
ip_stack_simulator_log.info("Client opened TCP connection %s",
conn_str.c_str());
}
} else {
// Connection is NOT new; this is probably a resend of an earlier SYN
if (!conn.awaiting_first_ack) {
throw logic_error("SYN received on already-open connection after initial phase");
}
// TODO: We should check the syn/ack numbers here instead of just assuming
// they're correct
conn_str = this->str_for_tcp_connection(c, conn);
if (this->state->ip_stack_debug) {
ip_stack_simulator_log.info("Client resent SYN for TCP connection %s",
conn_str.c_str());
}
}
// Send a SYN+ACK (send_tcp_frame always adds the ACK flag)
this->send_tcp_frame(c, conn, TCPHeader::Flag::SYN);
if (this->state->ip_stack_debug) {
ip_stack_simulator_log.info("Sent SYN+ACK on %s (acked_server_seq=%08" PRIX32 ", next_client_seq=%08" PRIX32 ")",
conn_str.c_str(), conn.acked_server_seq, conn.next_client_seq);
}
} else {
// This frame isn't a SYN, so a connection object should already exist
uint64_t key = this->tcp_conn_key_for_client_frame(fi);
IPClient::TCPConnection* conn;
try {
conn = &c->tcp_connections.at(key);
} catch (const out_of_range&) {
throw runtime_error("non-SYN frame does not correspond to any open TCP connection");
}
bool conn_valid = true;
if (fi.tcp->flags & TCPHeader::Flag::ACK) {
if (this->state->ip_stack_debug) {
ip_stack_simulator_log.info("Client sent ACK %08" PRIX32, fi.tcp->ack_num.load());
}
if (conn->awaiting_first_ack) {
if (fi.tcp->ack_num != conn->acked_server_seq + 1) {
throw runtime_error("first ack_num was not acked_server_seq + 1");
}
conn->acked_server_seq++;
conn->awaiting_first_ack = false;
} else {
if (seq_num_greater(fi.tcp->ack_num, conn->acked_server_seq)) {
if (this->state->ip_stack_debug) {
ip_stack_simulator_log.info("Advancing acked_server_seq from %08" PRIX32, conn->acked_server_seq);
}
uint32_t ack_delta = fi.tcp->ack_num - conn->acked_server_seq;
size_t pending_bytes = evbuffer_get_length(conn->pending_data.get());
if (pending_bytes < ack_delta) {
throw runtime_error("client acknowledged beyond end of sent data");
}
evbuffer_drain(conn->pending_data.get(), ack_delta);
conn->acked_server_seq += ack_delta;
conn->resend_push_usecs = DEFAULT_RESEND_PUSH_USECS;
if (this->state->ip_stack_debug) {
ip_stack_simulator_log.info("Removed %08" PRIX32 " bytes from pending buffer and advanced acked_server_seq to %08" PRIX32,
ack_delta, conn->acked_server_seq);
}
} else if (seq_num_less(fi.tcp->ack_num, conn->acked_server_seq)) {
throw runtime_error("client sent lower ack num than previous frame");
}
}
if (!conn->server_bev.get()) {
this->open_server_connection(c, *conn);
}
}
if (fi.tcp->flags & (TCPHeader::Flag::RST | TCPHeader::Flag::FIN)) {
bool is_rst = (fi.tcp->flags & TCPHeader::Flag::RST);
if (is_rst && (fi.tcp->flags & TCPHeader::Flag::FIN)) {
throw runtime_error("client sent TCP FIN+RST");
}
string conn_str = this->str_for_tcp_connection(c, *conn);
ip_stack_simulator_log.info("Client closed TCP connection %s", conn_str.c_str());
// TODO: Are we supposed to send a response to an RST? Here we do, and the
// client probably just ignores it anyway
this->send_tcp_frame(c, *conn, fi.tcp->flags & (TCPHeader::Flag::RST | TCPHeader::Flag::FIN));
// Delete the connection object. The unique_ptr destructor flushes the
// bufferevent, and thereby sends an EOF to the server's end.
c->tcp_connections.erase(key);
conn_valid = false;
// Note: The PSH flag isn't required to be set on all packets that contain
// data. The PSH flag just means "tell the application that data is
// available", so some senders only set the PSH flag on the last frame of a
// large segment of data, since the application wouldn't be able to process
// the segment until all of it is available. newserv can handle incomplete
// commands, so we just ignore the PSH flag and forward any data to the
// server immediately.
} else if (fi.payload_size != 0) {
string conn_str = this->state->ip_stack_debug ? this->str_for_tcp_connection(c, *conn) : "";
size_t payload_skip_bytes;
if (fi.tcp->seq_num == conn->next_client_seq) {
payload_skip_bytes = 0;
} else if (seq_num_less(fi.tcp->seq_num, conn->next_client_seq)) {
// If the frame overlaps an existing boundary, we'll accept some of the
// data; otherwise we'll ignore it entirely (but still send an ACK)
uint32_t end_seq = fi.tcp->seq_num + fi.payload_size;
if (seq_num_less_or_equal(end_seq, conn->next_client_seq)) { // Fully "in the past"
payload_skip_bytes = fi.payload_size;
} else { // Partially "in the past"
payload_skip_bytes = fi.payload_size - (end_seq - conn->next_client_seq);
}
} else {
// Payload is in the future - we must have missed a data frame. We'll
// ignore it (but warn) and send an ACK later, and the client should
// retransmit the lost data
if (this->state->ip_stack_debug) {
ip_stack_simulator_log.warning(
"Client sent out-of-order sequence number (expected %08" PRIX32 ", received %08" PRIX32 ", 0x%zX data bytes)",
conn->next_client_seq, fi.tcp->seq_num.load(), fi.payload_size);
}
payload_skip_bytes = fi.payload_size;
}
if (payload_skip_bytes > fi.payload_size) {
throw logic_error("payload skip bytes too large");
}
if (payload_skip_bytes < fi.payload_size) {
const void* payload = reinterpret_cast<const uint8_t*>(fi.payload) + payload_skip_bytes;
size_t payload_size = fi.payload_size - payload_skip_bytes;
if (this->state->ip_stack_debug) {
if (payload_skip_bytes) {
ip_stack_simulator_log.info("Client sent data on TCP connection %s, overlapping existing ack'ed data (0x%zX bytes ignored)",
conn_str.c_str(), payload_skip_bytes);
} else {
ip_stack_simulator_log.info("Client sent data on TCP connection %s",
conn_str.c_str());
}
print_data(stderr, payload, payload_size);
}
// Send the new data to the server
struct evbuffer* server_out_buf = bufferevent_get_output(
conn->server_bev.get());
evbuffer_add(server_out_buf, payload, payload_size);
// Update the sequence number and stats
conn->next_client_seq += payload_size;
conn->bytes_received += payload_size;
}
// Send an ACK
this->send_tcp_frame(c, *conn);
if (this->state->ip_stack_debug) {
ip_stack_simulator_log.info("Sent PSH ACK on %s (acked_server_seq=%08" PRIX32 ", next_client_seq=%08" PRIX32 ", bytes_received=0x%zX)",
conn_str.c_str(), conn->acked_server_seq, conn->next_client_seq, conn->bytes_received);
}
}
if (conn_valid) {
// Try to send some more data if the client is waiting on it
this->send_pending_push_frame(c, *conn);
}
}
}
void IPStackSimulator::open_server_connection(
shared_ptr<IPClient> c, IPClient::TCPConnection& conn) {
if (conn.server_bev.get()) {
throw logic_error("server connection is already open");
}
struct bufferevent* bevs[2];
bufferevent_pair_new(this->base.get(), 0, bevs);
// Set up the IPStackSimulator end of the virtual connection
bufferevent_setcb(bevs[0], &IPStackSimulator::dispatch_on_server_input,
nullptr, &IPStackSimulator::dispatch_on_server_error, &conn);
bufferevent_enable(bevs[0], EV_READ | EV_WRITE);
conn.server_bev.reset(bevs[0]);
// Link the client to the server - the server sees this as a normal TCP
// connection and treats it as if the client connected to one of its listening
// sockets
shared_ptr<const PortConfiguration> port_config;
try {
port_config = this->state->number_to_port_config.at(conn.server_port);
} catch (const out_of_range&) {
bufferevent_free(bevs[1]);
throw logic_error("client connected to port missing from configuration");
}
string conn_str = this->str_for_tcp_connection(c, conn);
if (port_config->behavior == ServerBehavior::PROXY_SERVER) {
if (!this->state->proxy_server.get()) {
ip_stack_simulator_log.error("TCP connection %s is to non-running proxy server",
conn_str.c_str());
flush_and_free_bufferevent(bevs[1]);
} else {
this->state->proxy_server->connect_client(bevs[1], conn.server_port);
ip_stack_simulator_log.info("Connected TCP connection %s to proxy server",
conn_str.c_str());
}
} else if (this->state->game_server.get()) {
this->state->game_server->connect_client(bevs[1], c->ipv4_addr,
conn.client_port, conn.server_port, port_config->version,
port_config->behavior);
ip_stack_simulator_log.info("Connected TCP connection %s to game server",
conn_str.c_str());
} else {
ip_stack_simulator_log.error("No server available for TCP connection %s",
conn_str.c_str());
flush_and_free_bufferevent(bevs[1]);
}
}
void IPStackSimulator::send_pending_push_frame(
shared_ptr<IPClient> c, IPClient::TCPConnection& conn) {
size_t pending_bytes = evbuffer_get_length(conn.pending_data.get());
if (!pending_bytes) {
return;
}
size_t bytes_to_send = min<size_t>(pending_bytes, conn.max_frame_size);
if (this->state->ip_stack_debug) {
ip_stack_simulator_log.info("Sending PSH frame with seq_num %08" PRIX32 ", 0x%zX/0x%zX data bytes",
conn.acked_server_seq, bytes_to_send, pending_bytes);
}
this->send_tcp_frame(c, conn, TCPHeader::Flag::PSH, conn.pending_data.get(),
bytes_to_send);
struct timeval resend_push_timeout = usecs_to_timeval(conn.resend_push_usecs);
event_add(conn.resend_push_event.get(), &resend_push_timeout);
// If the client isn't responding to our PSHes, back off exponentially up to
// a limit of 5 seconds between PSH frames. This window is reset when
// acked_server_seq changes (that is, when the client has acknowledged any new
// data)
conn.resend_push_usecs *= 2;
if (conn.resend_push_usecs > 5000000) {
conn.resend_push_usecs = 5000000;
}
}
void IPStackSimulator::send_tcp_frame(
shared_ptr<IPClient> c,
IPClient::TCPConnection& conn,
uint16_t flags,
struct evbuffer* src_buf,
size_t src_bytes) {
if (!src_bytes != !(flags & TCPHeader::Flag::PSH)) {
throw logic_error("data should be given if and only if PSH is given");
}
EthernetHeader ether;
memcpy(ether.dest_mac, c->mac_addr, 6);
memcpy(ether.src_mac, this->host_mac_address_bytes, 6);
ether.protocol = 0x0800; // IPv4
IPv4Header ipv4;
ipv4.version_ihl = 0x45;
ipv4.tos = 0;
// ipv4.size filled in later
ipv4.id = 0;
ipv4.frag_offset = 0;
ipv4.ttl = 20;
ipv4.protocol = 6; // TCP
// ipv4.checksum filled in later
ipv4.src_addr = conn.server_addr;
ipv4.dest_addr = c->ipv4_addr;
TCPHeader tcp;
tcp.src_port = conn.server_port;
tcp.dest_port = conn.client_port;
tcp.seq_num = conn.acked_server_seq;
tcp.ack_num = conn.next_client_seq;
tcp.flags = (5 << 12) | TCPHeader::Flag::ACK | flags;
tcp.window = 0x1000;
tcp.urgent_ptr = 0;
// tcp.checksum filled in later
ipv4.size = sizeof(IPv4Header) + sizeof(TCPHeader) + src_bytes;
ipv4.checksum = FrameInfo::computed_ipv4_header_checksum(ipv4);
const void* linear_data = src_bytes ? evbuffer_pullup(src_buf, src_bytes) : nullptr;
tcp.checksum = FrameInfo::computed_tcp4_checksum(
ipv4, tcp, linear_data, src_bytes);
struct evbuffer* out_buf = bufferevent_get_output(c->bev.get());
uint16_t frame_size = sizeof(ether) + sizeof(ipv4) + sizeof(tcp) + src_bytes;
evbuffer_add(out_buf, &frame_size, 2);
evbuffer_add(out_buf, &ether, sizeof(ether));
evbuffer_add(out_buf, &ipv4, sizeof(ipv4));
evbuffer_add(out_buf, &tcp, sizeof(tcp));
if (src_bytes) {
evbuffer_add(out_buf, linear_data, src_bytes);
}
if (this->pcap_text_log_file) {
StringWriter w;
w.write(&ether, sizeof(ether));
w.write(&ipv4, sizeof(ipv4));
w.write(&tcp, sizeof(tcp));
w.write(linear_data, src_bytes);
this->log_frame(w.str());
}
}
void IPStackSimulator::dispatch_on_resend_push(evutil_socket_t, short, void* ctx) {
auto* conn = reinterpret_cast<IPClient::TCPConnection*>(ctx);
auto c = conn->client.lock();
if (!c.get()) {
ip_stack_simulator_log.warning("Resend push event triggered for deleted client; ignoring");
} else {
c->sim->on_resend_push(c, *conn);
}
}
void IPStackSimulator::on_resend_push(shared_ptr<IPClient> c, IPClient::TCPConnection& conn) {
this->send_pending_push_frame(c, conn);
}
void IPStackSimulator::dispatch_on_server_input(struct bufferevent*, void* ctx) {
auto* conn = reinterpret_cast<IPClient::TCPConnection*>(ctx);
auto c = conn->client.lock();
if (!c.get()) {
ip_stack_simulator_log.warning("Server input event triggered for deleted client; ignoring");
} else {
c->sim->on_server_input(c, *conn);
}
}
void IPStackSimulator::on_server_input(shared_ptr<IPClient> c, IPClient::TCPConnection& conn) {
struct evbuffer* buf = bufferevent_get_input(conn.server_bev.get());
if (this->state->ip_stack_debug) {
ip_stack_simulator_log.info("Server input event: 0x%zX bytes to read",
evbuffer_get_length(buf));
}
evbuffer_add_buffer(conn.pending_data.get(), buf);
this->send_pending_push_frame(c, conn);
}
void IPStackSimulator::dispatch_on_server_error(
struct bufferevent*, short events, void* ctx) {
auto* conn = reinterpret_cast<IPClient::TCPConnection*>(ctx);
auto c = conn->client.lock();
if (!c.get()) {
ip_stack_simulator_log.warning("Server error event triggered for deleted client; ignoring");
} else {
c->sim->on_server_error(c, *conn, events);
}
}
void IPStackSimulator::on_server_error(
shared_ptr<IPClient> c, IPClient::TCPConnection& conn, short events) {
if (events & BEV_EVENT_ERROR) {
int err = EVUTIL_SOCKET_ERROR();
ip_stack_simulator_log.warning("Received error %d from virtual connection (%s)", err,
evutil_socket_error_to_string(err));
}
if (events & (BEV_EVENT_EOF | BEV_EVENT_ERROR)) {
// Send an RST to the client. Kind of rude (we really should use FIN) but
// the PSO network stack always sends an RST to us when disconnecting, so
// whatever
this->send_tcp_frame(c, conn, TCPHeader::Flag::RST);
// Delete the connection object (this also flushes and frees the server
// virtual connection bufferevent)
string conn_str = this->str_for_tcp_connection(c, conn);
ip_stack_simulator_log.info("Server closed TCP connection %s",
conn_str.c_str());
c->tcp_connections.erase(this->tcp_conn_key_for_connection(conn));
}
}
void IPStackSimulator::log_frame(const string& data) const {
if (this->pcap_text_log_file) {
print_data(this->pcap_text_log_file, data, 0, nullptr,
PrintDataFlags::SKIP_SEPARATOR);
fputc('\n', this->pcap_text_log_file);
fflush(this->pcap_text_log_file);
}
}
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