WebServer传输大文件致客户端自动关闭
1
悬赏园豆：5
[待解决问题]
程序运行在云服务器上, Ubuntu 20.04LTS系统，用浏览器测试能正常打开页面，请求一般的html文本和几十kb的小图片无问题，接着放了一个1.63MB（ 1714387字节）的网上找的图过去，客户端图没加载完就自动断连了，应用上看没问题，但我的设计是响应头默认Connection: keep-alive， 客户端自动断连了明显跟设计不符，遂开始debug。
<img src="https://rhino-picbase.oss-cn-hangzhou.aliyuncs.com/img/image-20230113191218513.png" alt="image-20230113191218513" style="zoom:50%;" />
首先排除SIGPIPE，因为自己strace并没有看到有sigpipe,再者客端断后服务器依然正常。strace一看是客户端自己断连触发了服务端EventLoop上的EPOLLRDHUP事件，到这就开始盲区搞不懂了。
自己之后瞎搞了半天，改函数打日志什么的就不说了。
自己还了写客户端模拟发送HTTP报文测试，显示normal close，读了80000多字节，喂喂你都没有读完耶，怎么就读到0了？
int main(int argc, char *argv[]){
const char *ip = argv[1];
int port = atoi(argv[2]);
if(argc < 3){
printf("usage:%s ip port\n", argv[0]);
return;
}
int sockfd = socket(PF_INET, SOCK_STREAM, 0);
assert(sockfd != -1);
struct sockaddr_in serv_addr;
socklen_t serv_addr_len = sizeof(serv_addr);
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = inet_addr(ip);
serv_addr.sin_port = htons(port);
assert(connect(sockfd, (sockaddr*)&serv_addr, serv_addr_len) != -1);
char req[1024] = {0};
const char *path = "image.png";
snprintf(req, 45 + strlen(path),"GET /%s HTTP/1.1\r\nConnection: keep-alive\r\n\r\n",path);
char buf[1024] = {0};
size_t wlen = -1;
size_t nread = 0;
do{
size_t wlen = write(sockfd,req, strlen(req));
printf("write: %s\n", req);
size_t rlen = read(sockfd, buf, sizeof(buf));
buf[rlen] = 0;
nread += rlen;
printf("read: %s\n", buf);
if(rlen > 0){
}
else if(rlen == 0){
perror("normal close");
break;
}
else{
perror("read error:");
break;
}
}while(wlen > 0);
printf("total read: %d\n", nread);
close(sockfd);
return 0;
}
把服务端和客户端分别抽到两个虚拟机排除SSL的因素, 然后两个端设tcpdump抓包输出文件，结果wireshark一看还是客户端自己给服务端发了FIN报文，始终搞不懂为什么。希望有大佬给出建议打破我的unknown unknown。
整个写响应流程涉及的代码如下：
void WebServer::EventLoop(){
int timeoutMS = -1;
while(1){
int nevent = epoll_wait(epollfd_, events_, MAX_EVENTS, timeoutMS);
for(int i = 0; i < nevent; ++i){
int sockfd = events_[i].data.fd;
uint32_t events = events_[i].events;
if(sockfd == listenfd_){
//add new connection
dealNewConn();
}
else if(events & (EPOLLRDHUP | EPOLLHUP | EPOLLERR)){
assert(connMap_[sockfd]);
dealCloseConn(connMap_[sockfd]);
}
else if(events & EPOLLIN){
//read request/close connection
assert(connMap_[sockfd]);
dealRead(connMap_[sockfd]);
}
else if(events & EPOLLOUT){
//send response
assert(connMap_[sockfd]);
dealWrite_debug(connMap_[sockfd]);
}
}
}
}
void WebServer::dealWrite_debug(const HttpConnectionPtr& client){
//正常这里应该是扔线程池，这里debug排除了多线程干扰
onWrite_debug(client);
}
void WebServer::onWrite_debug(const HttpConnectionPtr& client){
//确保用于写的连接还在,防止SF,连接用智能指针管理时尤其注意！
assert(client);
int writeErrno = 0;
ssize_t nwrite = client->writeOut_debug(&writeErrno);
const string& clientAddr = client->getClientAddr().getIpPort();
printf("write %ld byte to %s\n",nwrite,clientAddr.c_str());
if(client->toWriteBytes() == 0){
//传输完成
if(client->isKeepAlive()){
onProcess(client);
return;
}
}
else{
//传输未完成, 场景包括：正在写的时候对端断开连接
if(writeErrno == EAGAIN || writeErrno == EWOULDBLOCK){
epoll_modfd(epollfd_, client->getSocket(), EPOLLOUT | connEvent_);
return;
}
}
dealCloseConn(client);
}
void WebServer::dealCloseConn(const HttpConnectionPtr& client){
int connfd = client->getSocket();
perror("status");
epoll_delfd(epollfd_, connfd);
connMap_.erase(connfd);
}
ssize_t HttpConnection::writeOut_debug(int *saveErrno){
printf("Buffer write: \n");
cout << string(outbuffer_.peek(), outbuffer_.readableBytes()) << endl;
ssize_t len = -1;
ssize_t nwrite = 0;
do{
len = writev(sockfd_, iov_, iovCnt_);
if(iov_[0].iov_len + iov_[1].iov_len == 0){ break; }
if(len <= 0){ saveErrno = &errno; }
else if(static_cast<size_t>(len) <= iov_[0].iov_len){
iov_[0].iov_base = (uint8_t*) iov_[0].iov_base + len;
iov_[0].iov_len -= len;
outbuffer_.retrieve(len);
}
else{
iov_[1].iov_base = (uint8_t*) iov_[1].iov_base + (len - iov_[0].iov_len);
iov_[1].iov_len -= (len - iov_[0].iov_len);
if(iov_[0].iov_len) {
outbuffer_.retrieveAll();
iov_[0].iov_len = 0;
}
}
nwrite += len;
cout << "write: " << len << " " << "write bytes left: " << toWriteBytes() << endl;
}while(HttpConnection::isET && toWriteBytes() > 1024);
return nwrite;
}
//write_debug写响应操作前置的流程函数
bool HttpConnection::process(){
if(inbuffer_.readableBytes() <= 0)
return false;
HttpRequest req;
if(!httpParser_.parseRequest(inbuffer_,req))
return false;
assert(inbuffer_.readableBytes() == 0);
inbuffer_.retrieveAll();
string headkey = req.getHeader("Connection");
if(headkey == string("keep-alive")){
keepAlive_ = true;
}
else if(headkey == string("close")){
close_ = true;
}
HttpResponse resp(close_);
makeResponse(req,resp);
return true;
}
void HttpConnection::makeResponse(HttpRequest& req,HttpResponse& resp){
string path(srcDir_);
string file = (req.getPath() == "/") ? "/index.html" : req.getPath();
iovCnt_ = 1;
cout << "path: " << path + file << endl;
struct stat statbuf;
if(stat(string(path + file).data(),&statbuf) >= 0 && !S_ISDIR(statbuf.st_mode)){
iovCnt_++;
int filefd = open(string(path + file).data(), O_RDONLY);
fileLen_ = statbuf.st_size;
mmFile_ = mmap(0, fileLen_, PROT_READ, MAP_PRIVATE, filefd, 0);
assert(mmFile_ != (void*)-1);
close(filefd);
resp.setFile(true);
}
if(resp.isHaveFile()){
resp.setLine(HttpResponse::k200Ok);
resp.setContentType(MimeType::getFileType(file));
resp.setContentLength(fileLen_);
}
else{
resp.setLine(HttpResponse::k404NotFound);
resp.setCloseConnection(true);
}
resp.appendAllToBuffer(outbuffer_);
iov_[0].iov_base = const_cast<char*>(outbuffer_.peek());
iov_[0].iov_len = outbuffer_.readableBytes();
iov_[1].iov_base = mmFile_;
iov_[1].iov_len = fileLen_;
}
HttpConnection类头部涉及部分：
class HttpConnection : noncopyable{
public:
HttpConnection(int sockfd, const INetAddress& peerAddr, const INetAddress& hostAddr);
~HttpConnection() { onClose();}
ssize_t readIn(int* saveErrno);
bool process();
。。。。
public:
static bool isET;
static const char* srcDir_;
private:
void makeResponse(HttpRequest&,HttpResponse&);
。。。
void *mmFile_;
size_t fileLen_;
struct iovec iov_[2];
size_t iovCnt_;
Buffer inbuffer_;
Buffer outbuffer_;
HttpParser httpParser_;
};
输出效果如下：
# Buffer read 的输出函数没包括在给出的代码里面 算补充吧
Buffer read:
GET /image.png HTTP/1.1
Host: sss.sss.sss.sss:9006
User-Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:108.0) Gecko/20100101 Firefox/108.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,*/*;q=0.8
Accept-Language: zh-CN,zh;q=0.8,zh-TW;q=0.7,zh-HK;q=0.5,en-US;q=0.3,en;q=0.2
Accept-Encoding: gzip, deflate
Connection: keep-alive
Upgrade-Insecure-Requests: 1
# 正式打印部分
path: /home/LinuxC++/Project/re_webserver/root/image.png
Buffer write:
HTTP/1.1 200 OK
Connection: keep-alive
Content-Length: 1714387
Content-Type: image/png
write: 143080 to write bytes left: 1571400
write 143080 byte to ccc.ccc.ccc.ccc:35521
status: Invalid argument
connection ccc.ccc.ccc.ccc:35521 -> sss.sss.sss.sss:9006 closed
connection ccc.ccc.ccc.ccc:35550 -> sss.sss.sss.sss:9006
Note: 发现不同浏览器请求的行为不一样，Chrome除了请求页面还请求favicon.ico，而且似乎会自动检测是不是静态资源，是就自动断连，估计是我Chrome上插件的影响，Firefox就不会，后面的输出结果以Firefox为准。注意是Linux上的Firefox，试过Windows上的Firefox，不知为什么原因请求完资源后客端也会自动断连。
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