Server write error

[wrrte]

제가 작성한 write 코드가 왜 제대로 실행되지 않는지 모르겠어서 3번째 테스트 케이스인 Server -> Client 부터 디버깅을 하고 있는데, 아예 server 측에서 write 함수가 제대로 작동하지 않습니다.

     while ((write_byte =
                write(client_fd, send_buffer + (buffer_size - remaining),
                      remaining)) >= 0) {
      
      printf("write_byte : %d\n", write_byte);

      total_size += write_byte;
      remaining -= write_byte;
      EXPECT_GE(remaining, 0);
      if (remaining == 0)
        break;
    }
    if (write_byte < 0){
      //printf("%d %x %d\n", client_fd, send_buffer + (buffer_size - remaining),remaining);
      printf("error code : %d\n", write_byte);
      printf("errno: %d, message: %s\n", errno, strerror(errno));
      break;
    }

error code : -1
errno: 22, message: Invalid argument
/Users/choemj/KENSv3/app/kens/testtransfer.cpp:189: Failure
Expected equality of these values:
expect_size
Which is: 131072
total_size
Which is: 0

total_size가 0보다 크다면 제가 작성한 read 함수가 ack을 제대로 보내지 않는 등의 문제일 수도 있겠는데, 한 번도 실행되지 않고 바로 Invalid argument 에러가 발생하는 것은 제가 코드를 바꾼다고 해결할 수 있는 문제가 아니지 않나요? 혹시 기존 코드에 문제가 있는지, 아니면 제 코드(client)의 어떤 부분이 서버의 write 코드의 실행에 영향을 끼쳐 이런 에러를 일으킬 수 있는지 궁금합니다.

[lgm9]

Which test case do you mean? What is the 3rd test case? If you are running any test cases with the keyword 'send' on the test transfer, then it would be testing your write function.
Attached code is likely to be in the send part, so I think your write function causes this error.
This was the result of my code on this assignment.

[wrrte]

/**

• Data direction: Server -> Client.
• Same as TestTransfer_Connect_Send_Symmetric but the data direction is
• changed.
  */
  TEST_F(TestEnv_Any, TestTransfer_Connect_Recv_Symmetric) {
  std::unordered_map<std::string, std::string> accept_env;
  std::unordered_map<std::string, std::string> connect_env;

int seed = rand();
accept_env["RANDOM_SEED"] = seed;
connect_env["RANDOM_SEED"] = seed;

ipv4_t ip1 = host1->getIPAddr(0).value();
ipv4_t ip2 = host2->getIPAddr(0).value();

char str_buffer[128];
snprintf(str_buffer, sizeof(str_buffer), "%u.%u.%u.%u", ip1[0], ip1[1],
ip1[2], ip1[3]);
std::string host1_ip(str_buffer);
snprintf(str_buffer, sizeof(str_buffer), "%u.%u.%u.%u", ip2[0], ip2[1],
ip2[2], ip2[3]);
std::string host2_ip(str_buffer);

accept_env["LISTEN_ADDR"] = "0.0.0.0";
accept_env["LISTEN_PORT"] = "9999";
accept_env["BACKLOG"] = "1";
accept_env["LISTEN_TIME"] = "0";
accept_env["ACCEPT_TIME"] = TimeUtil::printTime(
TimeUtil::makeTime(1000, TimeUtil::USEC), TimeUtil::USEC);
accept_env["START_TIME"] =
TimeUtil::printTime(TimeUtil::makeTime(1, TimeUtil::SEC), TimeUtil::USEC);

connect_env["CONNECT_PORT"] = "9999";
connect_env["CONNECT_TIME"] = TimeUtil::printTime(
TimeUtil::makeTime(2000, TimeUtil::USEC), TimeUtil::USEC);
connect_env["START_TIME"] =
TimeUtil::printTime(TimeUtil::makeTime(1, TimeUtil::SEC), TimeUtil::USEC);

connect_env["CONNECT_ADDR"] = host2_ip;
connect_env["BUFFER_SIZE"] = "1024";
connect_env["LOOP_COUNT"] = "128";
connect_env["SENDER"] = "0";
connect_env["EXPECT_SIZE"] = "131072";
int client_pid =
host1->addApplication<TestTransfer_Connect>(*host1, connect_env);

accept_env["SENDER"] = "1";
accept_env["BUFFER_SIZE"] = "1024";
accept_env["LOOP_COUNT"] = "128";
accept_env["EXPECT_SIZE"] = "131072";
int server_pid =
host2->addApplication<TestTransfer_Accept>(*host2, accept_env);

host2->launchApplication(server_pid);
host1->launchApplication(client_pid);

this->runTest();
}

This test case is third case, and this code do not execute write because it is Recv, not send, isn't it?
I got same seq# packet repeatedly even I sent ACK packet with header.th_ack = htonl(ntohl(header.th_seq)+1); and header.th_win = 200; and checksum that all passed previous test case.
And of course, I'm doing in relieble channel.

[lgm9]

Could you specify your question as
I got an error on 'this' test case,
I tried to do things like: "these"
I got the error because of 'this'
to help me exactly understand what problem you've faced.

If you got an error on the recv side, then your error is not related to the part attached to your first question, but it would be related to

int remaining = buffer_size;
int read_byte = 0;
while ((read_byte =
read(client_fd, recv_buffer + (buffer_size - remaining),
remaining)) >= 0) {
total_size += read_byte;
remaining -= read_byte;
EXPECT_GE(remaining, 0);
if (remaining == 0)
break;
}
if (buffer_size - remaining > 0) {
for (int j = 0; j < buffer_size - remaining; j++) {
EXPECT_EQ(send_buffer[j], recv_buffer[j]);
}
}
if (read_byte < 0)
break;
}

As you could see, this is related to the read system call.
Also, if you change your test files, then I might not be able to track your error because the line number would be different from the original test code.

From my test code, the 189th line is a comment line, so I guess your error originates from the 177th line, where the difference between the size that is read (or written) is different from the value expected.

Trying to debug yourself with the printf function in your actual code might help you understand which test case tests which system calls.

[wrrte]

I got an Failure on original 'TestTransfer_Connect_Recv_Symmetric' test case, 177th line EXPECT_EQ(expect_size, total_size);
If I understand write, 177th line means Server's write function didn't execute properly because from 51th line to 183th line in app/kens/testtransfer.cpp is executing server's hidden code, not my code.

I tried to know what is happening in server's code, so I printed out data packets from server.
By doing so, I found server sending same packet with seq#=4294962358 repeatedly, even if I sent ACK packet with ack#=4294962359.
So I thought write code of server didnt' work, so I checked 137~139th line, which is result of server's write.

    while ((write_byte =
                write(client_fd, send_buffer + (buffer_size - remaining),
                      remaining)) >= 0) {

And return value write_byte is -1.

I checked 'is_send' in 134th line is true, so it means 177th line EXPECT_EQ(expect_size, total_size); occurs error because server couldn't execute write well and so 154th line total_size += write_byte; didn't execute.

So I think I got error because server side code write(client_fd, send_buffer + (buffer_size - remaining), remaining) returned -1 and ended, before I do something.

위의 write(client_fd, send_buffer + (buffer_size - remaining), remaining) 코드가 처음 한 번은 제대로 실행되어야 제가 보낸 ack을 받아 계속해서 데이터를 주고받을 수 있을 것 같은데, client가 아무 영향도 주지 않은 맨 처음 상태에서 바로 에러를 띄워버리니 대체 어느 부분을 손보아야 할지 모르겠습니다. handshake과정에서 문제가 생기지 않았다면 client의 read 구현과 상관없이 처음 write는 제대로 실행되어야 하지 않나요?
위에서 언급한 '반복해서 보내는 데이터 패킷'의 데이터 값은 testcase의 send_packet 값과 차이가 전혀 없는 걸로 보아 server가 패킷을 제대로 보내기는 하는 것 같은데, 왜 패킷을 제대로 보냈으면서 -1을 반환하는지 모르겠습니다.

[lgm9]

I got a little confusion here. Did you give your ack = syn + 1 in your handshake or in communication? Try to check the pcap when you run the model solution. I think this might help.

[wrrte]

problem solved! thank you.