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SocketCloseTest.cpp
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SocketCloseTest.cpp
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// Linux: g++ -o socketclosetest SocketCloseTest.cpp -lpthread
// Windows: Visual Studio
#ifdef _WIN32
#define _CRT_SECURE_NO_WARNINGS // for sscanf
#include <winsock2.h>
#include <Windows.h>
#endif
#include <stdio.h>
#include <stdlib.h> // for EXIT_FAILURE
#include <string.h> // for strerror()
#include <stdarg.h> // for va_arg stuff
#ifndef _WIN32
#include <errno.h>
#include <pthread.h>
#include <unistd.h>
#include <netinet/in.h>
#endif
#include <string>
#ifdef _WIN32
#define popen _popen
#define pclose _pclose
typedef int socklen_t;
#else
typedef int SOCKET;
#define SOCKET_ERROR (-1)
#define INVALID_SOCKET (-1)
#define closesocket(x) close(x)
typedef long LONG;
typedef unsigned long DWORD;
#define INFINITE 0xFFFFFFFF
#define WINAPI
typedef DWORD(WINAPI *LPTHREAD_START_ROUTINE)(void*);
#endif
// Windows ephemeral port range is 49152-65535, so pick a port out of the range
// to make it easier to find in netstat output.
static const int PORT = 40000;
static const size_t MAX_ERROR_COUNT = 10;
size_t g_warning_count = 0;
volatile size_t g_connect_count = 0;
#ifdef _WIN32
void TrimEnd(char* s) { // Adapted from http://stackoverflow.com/a/123724
char* p = s;
int l = strlen(p);
while (l != 0 && isspace(p[l - 1])) p[--l] = 0;
}
std::string GetErrorString(DWORD err) {
char buf[256];
if (!FormatMessageA(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
NULL, err, 0, buf, sizeof(buf), NULL))
sprintf_s(buf, sizeof(buf), "FormatMessageA(%lu): %lu", err, GetLastError());
TrimEnd(buf);
return buf;
}
const char* GetErrorName(int err) {
if (err == WSAEADDRINUSE) return "WSAEADDRINUSE";
if (err == WSAECONNRESET) return "WSAECONNRESET";
return NULL;
}
std::string GetErrorNumberDescription(int err) {
const char* name = GetErrorName(err);
char buf[128];
if (name != NULL)
sprintf_s(buf, sizeof(buf), "%s (%d)", name, err);
else
sprintf_s(buf, sizeof(buf), "%d", err);
return buf;
}
#endif
void voutput(const char *fmt, va_list ap) {
int err;
#ifdef _WIN32
err = GetLastError(); // Same as WSAGetLastError()
#else
err = errno;
#endif
// Buffer up all output so that multiple threads' output is not interleaved.
std::string output;
char buf[1024];
#ifdef _WIN32
SYSTEMTIME system_time;
GetLocalTime(&system_time);
snprintf(buf, sizeof(buf), "[%02u:%02u:%02u:%03u] ", system_time.wHour, system_time.wMinute, system_time.wSecond, system_time.wMilliseconds);
output.append(buf);
#endif
output.append("error: ");
if (fmt != NULL) {
vsnprintf(buf, sizeof(buf), fmt, ap);
output.append(buf);
output.append(": ");
}
#ifdef _WIN32
snprintf(buf, sizeof(buf), "error %s: %s\n", GetErrorNumberDescription(err).c_str(), GetErrorString(err).c_str());
#else
snprintf(buf, sizeof(buf), "error %d: %s\n", err, strerror(err));
#endif
output.append(buf);
fputs(output.c_str(), stderr);
}
void error(const char *fmt, ...) {
va_list ap;
va_start(ap, fmt);
voutput(fmt, ap);
va_end(ap);
exit(EXIT_FAILURE);
}
#ifndef _WIN32
void Sleep(DWORD milliseconds) {
if (milliseconds == INFINITE) {
for (;;)
Sleep(1000000);
} else {
struct timespec t;
t.tv_sec = milliseconds / 1000;
t.tv_nsec = (milliseconds % 1000) * 1000000;
if (nanosleep(&t, NULL) == -1)
error("nanosleep");
}
}
LONG InterlockedIncrement(volatile LONG* val) {
return __sync_add_and_fetch(val, 1);
}
#endif
void warning(const char *fmt, ...) {
va_list ap;
va_start(ap, fmt);
voutput(fmt, ap);
va_end(ap);
if (++g_warning_count >= MAX_ERROR_COUNT)
Sleep(INFINITE); // block forever to stop error output from subsequent failures
}
#ifdef _WIN32
class Event {
public:
Event(bool manual_reset, bool initial_state) {
event_ = CreateEventW(NULL, manual_reset ? TRUE : FALSE, initial_state ? TRUE : FALSE, NULL);
if (event_ == NULL)
error("CreateEventW");
}
void Set() {
if (!SetEvent(event_))
error("SetEvent");
}
void Wait() {
if (WaitForSingleObject(event_, INFINITE) != WAIT_OBJECT_0)
error("WaitForSingleObject");
}
private:
HANDLE event_;
};
#else
class Event { // Adapted from http://stackoverflow.com/a/178962
public:
Event(bool manual_reset, bool initial_state)
: set_(initial_state), manual_reset_(manual_reset) {
pthread_mutex_init(&mutex_, 0);
pthread_cond_init(&cond_, 0);
}
void Set() {
pthread_mutex_lock(&mutex_);
set_ = true;
pthread_cond_signal(&cond_);
pthread_mutex_unlock(&mutex_);
}
void Wait() {
pthread_mutex_lock(&mutex_);
while (!set_)
pthread_cond_wait(&cond_, &mutex_);
if (!manual_reset_)
set_ = false;
pthread_mutex_unlock(&mutex_);
}
private:
pthread_mutex_t mutex_;
pthread_cond_t cond_;
bool set_;
bool manual_reset_;
};
#endif
void StartThread(LPTHREAD_START_ROUTINE pfn, void* pv) {
#ifdef _WIN32
if (CreateThread(NULL, 0, pfn, pv, 0, NULL) == NULL)
error("CreateThread");
#else
pthread_t thread;
errno = pthread_create(&thread, NULL, (void*(*)(void*))pfn, pv);
if (errno != 0)
error("pthread_create");
#endif
}
void NetStat(size_t* server_connections, size_t* client_connections) {
#ifdef _WIN32
const char* cmd = "netstat -an -p TCP";
#else
const char* cmd = "netstat -an -t -4";
#endif
FILE* p = popen(cmd, "r");
if (p == NULL)
error("popen");
*server_connections = 0;
*client_connections = 0;
char line[1024];
while (fgets(line, sizeof(line), p)) {
int local_port = 0, peer_port = 0;
char state[64];
bool parsed;
#ifdef _WIN32
parsed = sscanf(line, " TCP 127.0.0.1:%d 127.0.0.1:%d %s", &local_port, &peer_port, state) == 3;
#else
char recv_q[64], send_q[64];
parsed = sscanf(line, "tcp %s %s 127.0.0.1:%d 127.0.0.1:%d %s", recv_q, send_q, &local_port, &peer_port, state) == 5;
#endif
if (parsed) {
if (local_port == PORT)
(*server_connections)++;
else if (peer_port == PORT)
(*client_connections)++;
}
}
if (pclose(p) == -1)
error("pclose");
}
class Barrier { // Adapted from http://6xq.net/barrier-intro/
public:
class Context {
public:
Context()
: local_sense_(0) {}
private:
LONG local_sense_;
friend class Barrier;
};
Barrier(LONG total)
: total_(total), count_(0), global_sense_(0) {}
void Wait(Barrier::Context* context) {
context->local_sense_ = !context->local_sense_;
if (InterlockedIncrement(&count_) == total_) {
count_ = 0; // reset to zero
global_sense_ = context->local_sense_; // release everyone else
} else {
while (global_sense_ != context->local_sense_) {
// Busy-wait the CPU which is wasteful, but perhaps it will
// cause all the waiters to run very nearly at the same time.
}
}
}
private:
const LONG total_;
volatile LONG count_;
volatile LONG global_sense_;
};
class SynchronizationPolicy {
public:
virtual void BeforeCloseSocket(SOCKET s) {};
virtual void AfterCloseSocket() {};
};
class WaitSynchronizationPolicy : public SynchronizationPolicy {
public:
WaitSynchronizationPolicy(Event* event1, Event* event2)
: event1_(event1), event2_(event2) {}
void BeforeCloseSocket(SOCKET s) {
event1_->Wait();
}
void AfterCloseSocket() {
event2_->Set();
}
private:
Event* event1_;
Event* event2_;
};
class BarrierSynchronizationPolicy : public SynchronizationPolicy {
public:
BarrierSynchronizationPolicy(Barrier* barrier)
: barrier_(barrier), barrier_context_() {}
void BeforeCloseSocket(SOCKET s) {
barrier_->Wait(&barrier_context_);
}
private:
Barrier* barrier_;
Barrier::Context barrier_context_;
};
class GracefulShutdownSynchronizationPolicy : public SynchronizationPolicy {
public:
void BeforeCloseSocket(SOCKET s) {
int result;
do {
char buf[64];
result = recv(s, buf, sizeof(buf), 0);
} while (result != SOCKET_ERROR && result != 0);
if (result == SOCKET_ERROR) {
// Save error because it will be overwritten by
// getsockname()/getpeername().
#ifdef _WIN32
DWORD saved_err = GetLastError();
#else
int saved_err = errno;
#endif
int local_port = -1, peer_port = -1;
struct sockaddr_in name;
socklen_t namelen = sizeof(name);
if (getsockname(s, (struct sockaddr*)&name, &namelen) != SOCKET_ERROR)
local_port = ntohs(name.sin_port);
namelen = sizeof(name);
if (getpeername(s, (struct sockaddr*)&name, &namelen) != SOCKET_ERROR)
peer_port = ntohs(name.sin_port);
#ifdef _WIN32
SetLastError(saved_err);
#else
errno = saved_err;
#endif
warning("recv on local port %d, peer port %d", local_port, peer_port);
}
}
};
Event g_server_ready(false, false);
DWORD WINAPI TestServerThread(void* arg) {
SynchronizationPolicy* synch_policy = (SynchronizationPolicy*)arg;
SOCKET listener = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if (listener == INVALID_SOCKET)
error("socket");
#ifndef _WIN32
// After process exits, allow a subsequent process to grab the port.
int optval = 1;
if (setsockopt(listener, SOL_SOCKET, SO_REUSEADDR, (char*)&optval, sizeof(optval)) == SOCKET_ERROR)
error("setsockopt");
#endif
struct sockaddr_in sa;
memset(&sa, 0, sizeof(sa));
sa.sin_family = AF_INET;
sa.sin_port = htons(PORT);
sa.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
if (bind(listener, (const sockaddr*)&sa, sizeof(sa)) == SOCKET_ERROR)
error("bind");
if (listen(listener, SOMAXCONN) == SOCKET_ERROR)
error("listen");
g_server_ready.Set(); // let client start connecting
for (;;) {
SOCKET s = accept(listener, NULL, NULL);
if (s == INVALID_SOCKET)
error("accept");
synch_policy->BeforeCloseSocket(s);
if (closesocket(s) == SOCKET_ERROR)
error("closesocket");
synch_policy->AfterCloseSocket();
}
if (closesocket(listener) == SOCKET_ERROR)
error("closesocket");
return 0;
}
DWORD WINAPI TestClientThread(void* arg) {
SynchronizationPolicy* synch_policy = (SynchronizationPolicy*)arg;
g_server_ready.Wait(); // wait for server to start listening
for (;;) {
SOCKET s = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if (s == INVALID_SOCKET)
error("socket");
struct sockaddr_in sa;
memset(&sa, 0, sizeof(sa));
sa.sin_family = AF_INET;
sa.sin_port = htons(PORT);
sa.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
if (connect(s, (const sockaddr*)&sa, sizeof(sa)) == SOCKET_ERROR) {
warning("connect");
if (closesocket(s) == SOCKET_ERROR)
error("closesocket");
} else {
g_connect_count++;
synch_policy->BeforeCloseSocket(s);
if (closesocket(s) == SOCKET_ERROR)
error("closesocket");
synch_policy->AfterCloseSocket();
}
}
return 0;
}
int Usage(int /*argc*/, char** argv) {
fprintf(stderr, "usage: %s <any|client|server|simultaneous|graceful>\n", argv[0]);
fprintf(stderr, "NOTE: This program runs netstat to display connection statistics.\n");
return 1;
}
int main(int argc, char** argv) {
if (argc != 2)
return Usage(argc, argv);
// Windows
// -------
// any: 11000 connects/sec, WSAEADDRINUSE, netstat: 16300 client, 700 server
// client close: 11000 connects/sec, WSAEADDRINUSE, netstat: 16000 client connections
// server close: 6000 connects/sec, no errors, netstat: 16000 server connections, client connections slowly growing
// simultaneous close: 6500 connects/sec, WSAEADDRINUSE, netstat: 16000 server, 16000 client
// graceful close: 6500 connects/sec, occasional WSAECONNRESET on recv(), netstat: 16000 server
// Linux
// -----
// any: wide ranging connects/sec (250-80000), no errors, netstat: 2700 server, 14000 client
// client close: 21000 connects/sec, no errors, netstat: 16000 client connections
// server close: 16000 connects/sec, no errors, netstat: 16000 server connections
// simultaneous close: 48000 connects/sec, no errors, netstat: 8000 server, 8000 client
// graceful close: 17000 connects/sec, no errors, netstat: 16000 server
SynchronizationPolicy* client_policy = NULL;
SynchronizationPolicy* server_policy = NULL;
Event event_initially_nonsignaled(false, false);
Event event_initially_signaled(false, true);
Barrier barrier(2);
if (!strcmp(argv[1], "any")) {
client_policy = server_policy = new SynchronizationPolicy(); // policy does nothing
} else if (!strcmp(argv[1], "client")) {
// server waits for client to do closesocket(), then client tells server to do closesocket()
client_policy = new WaitSynchronizationPolicy(&event_initially_signaled, &event_initially_nonsignaled);
server_policy = new WaitSynchronizationPolicy(&event_initially_nonsignaled, &event_initially_signaled);
} else if (!strcmp(argv[1], "server")) {
// client waits for server to do closesocket(), then server tells client to do closesocket()
client_policy = new WaitSynchronizationPolicy(&event_initially_nonsignaled, &event_initially_signaled);
server_policy = new WaitSynchronizationPolicy(&event_initially_signaled, &event_initially_nonsignaled);
} else if (!strcmp(argv[1], "simultaneous")) {
// client and server try to call closesocket() approximately simultaneously.
client_policy = new BarrierSynchronizationPolicy(&barrier);
server_policy = new BarrierSynchronizationPolicy(&barrier);
} else if (!strcmp(argv[1], "graceful")) {
client_policy = new GracefulShutdownSynchronizationPolicy();
server_policy = new SynchronizationPolicy(); // don't do anything special
} else {
return Usage(argc, argv);
}
#ifdef _WIN32
WSADATA wsaData;
int result = WSAStartup(MAKEWORD(2, 2), &wsaData);
if (result != 0) {
fprintf(stderr, "error: WSAStartup: %d\n", result);
exit(EXIT_FAILURE);
}
#endif
size_t server_connections, client_connections;
NetStat(&server_connections, &client_connections);
if (server_connections != 0)
fprintf(stderr, "There are %zu lingering server connections from 127.0.0.1:%d in netstat.\n", server_connections, PORT);
if (client_connections != 0)
fprintf(stderr, "There are %zu lingering client connections to 127.0.0.1:%d in netstat.\n", client_connections, PORT);
if ((server_connections != 0) || (client_connections != 0)) {
fprintf(stderr, "Wait a minute and try again.\n");
exit(EXIT_FAILURE);
}
StartThread(TestServerThread, server_policy);
StartThread(TestClientThread, client_policy);
while (g_warning_count < MAX_ERROR_COUNT) {
size_t old_connect_count = g_connect_count;
Sleep(1000);
size_t new_connect_count = g_connect_count;
NetStat(&server_connections, &client_connections);
printf("connects per second: %zu, server connections: %zu, client connections: %zu\n",
new_connect_count - old_connect_count, server_connections, client_connections);
}
fprintf(stderr, "exiting after %zu errors\n", MAX_ERROR_COUNT);
NetStat(&server_connections, &client_connections);
printf("server connections: %zu, client connections: %zu\n",
server_connections, client_connections);
exit(EXIT_FAILURE);
return 0;
}