Nameserver

Group Members

• Ruturaj Shitole
• Boxin Yang
• Swarup Totloor
• Prince Noah Johnson

Description

A nameserver that listens on a named domain socket and listens for connections, where a client connecting to the nameserver can perform one of the three actions:

• Publish a resource - PUB <resource>
• Request a resource - REQ <resource>
• Exit - exit

The server maintains a list of active connections and the associated resources they provide.

Whenever a client requests for a resource, the server asks the associated client with the resource to provide a file descriptor and then it relays the file descriptor to the client requesting for it.

In this project, we are only concerned with files as resources being passed around. So when a file is published, the client just opens that particular file with some identifying text (if the file doesn't exist.)

Methodology

Project Contributions

The project was divided into several parts, with each group member contributing to different aspects:

• Ruturaj Shitole: Core structure with domain sockets, testing and Makefile
• Boxin Yang: Client implementation, passing file descriptors
• Swarup Totloor: Server implementation with epoll, request relay between clients
• Prince Noah Johnson: Authentication and its testing

High-Level Design

How do we handle each of the requirements for the project? The nameserver:

1. Listens on a named domain socket for incoming client connections. (/tmp/sock-test.socket)
2. Uses accept() to create unique fd per client in the main event loop of the server.
3. The event loop of the server uses epoll for concurrency.
4. Authenticates each client using getsockopt.
5. Relays file descriptors of resources between clients using sendmsg and recvmsg.

For more detailed information on the implementation, please refer to the following files:

• Core server loop
• Client loop
• Auth implementation
• Tests

Testing

To run our project:

1. Compile the project using the provided Makefile:

   make

   The expected output should look like this:

   (TERMINAL_1)@/advos-unix-service$ make
   gcc -Wall -Wextra -Isrc -MMD -MP -c -o .build/server/auth.o src/server/auth.c 
   gcc -Wall -Wextra -Isrc -MMD -MP -c -o .build/server/main.o src/server/main.c 
   gcc -Wall -Wextra -Isrc -MMD -MP -c -o .build/server/server.o src/server/server.c 
   gcc -Wall -Wextra -Isrc -MMD -MP -c -o .build/common/logger.o src/common/logger.c 
   gcc -Wall -Wextra -Isrc -MMD -MP -c -o .build/common/passfd.o src/common/passfd.c 
   gcc -Wall -Wextra -Isrc -MMD -MP -o server.out .build/server/auth.o .build/server/main.o .build/server/server.o .build/common/logger.o .build/common/passfd.o
   gcc -Wall -Wextra -Isrc -MMD -MP -c -o .build/client/client.o src/client/client.c 
   gcc -Wall -Wextra -Isrc -MMD -MP -c -o .build/client/main.o src/client/main.c 
   gcc -Wall -Wextra -Isrc -MMD -MP -o client.out .build/client/client.o .build/client/main.o .build/common/logger.o .build/common/passfd.o

2. Run the server:

   make start_nameserver

   The expected output should look like this:

   (TERMINAL_1)@/advos-unix-service$ make start_nameserver
   ./server.out > server.log 2>&1

3. Run client 1:

   make start_client

   The expected output should look like this:

   (TERMINAL_2)@/advos-unix-service$ make start_client 
   ./client.out
   [info] creating data socket
   [info] created data socket
   Commands available:
       1. PUB <resource>
       2. REQ <resource>
       3. exit
   client>

4. Run client 2 in another terminal:

   make start_client

   The expected output should look like this:

   (TERMINAL_3)@/advos-unix-service$ make start_client 
   ./client.out
   [info] creating data socket
   [info] created data socket
   Commands available:
       1. PUB <resource>
       2. REQ <resource>
       3. exit
   client>

5. Input commands in any client to interact with the other clients.

6. Observe server.log to see the logs for nameserver. If you would like to kill the nameserver, simply use kill <pid> using the PID from the log file.

7. Run the tests:

   make test

   The expected output should look like this:

   (TERMINAL_1)@/advos-unix-service$ make test
   gcc -Wall -Wextra -Isrc -MMD -MP -c -o .build/common/logger.o src/common/logger.c 
   gcc -Wall -Wextra -Isrc -MMD -MP -c -o .build/common/passfd.o src/common/passfd.c 
   gcc -Wall -Wextra -Isrc -MMD -MP -c -o .build/server/auth.o src/server/auth.c 
   gcc -Wall -Wextra -Isrc -MMD -MP -c -o .build/server/server.o src/server/server.c 
   gcc -Wall -Wextra -Isrc -MMD -MP -c -o .build/client/client.o src/client/client.c 
   ---------RUNNING TESTS---------
   test:common_02_test_passfd:test_send_recv_fd:PASSED
   test:client_02_test_handler:test_handle_stdin_event_pub:PASSED
   read 17 bytes
   server> Hello from server
   
   server> Hello from server
   test:client_02_test_handler:test_handle_datasock_event_nonreq:PASSED
   test:server_01_test_utils:test_init:PASSED
   test:server_01_test_utils:test_create_connection_socket:PASSED
   test:server_01_test_utils:test_bind_connection_socket:PASSED
   test:server_01_test_utils:test_create_epoll_fd:PASSED
   test:server_01_test_utils:test_set_nonblocking:PASSED
   test:server_01_test_utils:test_do_op:PASSED
   test:server_01_test_utils:test_get_resource_from_message:PASSED
   test:client_01_test_utils:test_init:PASSED
   test:client_01_test_utils:test_create_data_socket:PASSED
   test:client_01_test_utils:test_create_epoll_fd:PASSED
   test:client_01_test_utils:test_set_nonblocking:PASSED
   test:server_01_test_auth:test_get_client_credentials_invalid:PASSED
   test:common_01_test_logger:test_std_logger_init:PASSED
   test:common_01_test_logger:test_std_log:PASSED
   ---------FINISHED TESTS---------

Attributions

These resources proved to be useful during the development of this project.

1. Domain sockets and event loops -

   • Systems Programming textbook
   • Sockets man page

2. Passing FDs -

   • The Linux Programming Interface

3. Authentication -

   • IBM Docs
   • Getsockopt man page

4. Testing with socket pairs -

   • Socket pairs man page
   • Stack Overflow post

5. ChatGPT -

   • Color codes: Prompt("give me all the color codes for linux terminals")