client.c

#include <unistd.h>
#include <string.h>
#include <assert.h>
#include <errno.h>
#include <stdio.h>
#include <fcntl.h>
#include "client.h"
#include "command.h"

void create_client(ftp_client_t* client, ftp_server_t* server) {
  assert(client != NULL);
  memset(client, 0, sizeof(ftp_client_t));
  client->cntl_fd = client->data_fd
      = client->pasv_listen_fd = client->local_fd = -1;
  client->state = S_INIT;
  client->mode = M_UNKNOWN;
  client->server = server;
  strncpy(client->cwd, server->basepath, PATH_MAX);
}

void try_accept_pasv(ftp_client_t* client) {
  if (client->mode != M_PASV || client->data_fd != -1) {
    return;
  }
  client->data_fd = accept(client->pasv_listen_fd,
                           (struct sockaddr*)&client->data_sockaddr,
                               &client->data_sockaddr_len);
  if (client->data_fd == -1) {
    if (errno != EAGAIN && errno != EWOULDBLOCK) {
      perror("accept() with pasv socket");
      client->data_fd = -1; /* ensure that data_fd is -1 */
    } else {
      /* not an error; still waiting for a connection */
    }
  } else {
    if (fcntl(client->data_fd, F_SETFL, O_NONBLOCK) == -1) {
      perror("fcntl() when trying to accept a PASV connection");
      shutdown(client->data_fd, SHUT_RDWR);
      close(client->data_fd);
      client->data_fd = -1;
    }

    errno = 0;
    epoll_ctl(client->server->epollfd, EPOLL_CTL_ADD, client->data_fd,
              &(struct epoll_event){.data.ptr = client, .events = EPOLLIN});
    if (errno) {
      perror("epoll_ctl() when trying to accept a PASV connection");
      shutdown(client->data_fd, SHUT_RDWR);
      close(client->data_fd);
      client->data_fd = -1;
    }
  }
}

extern const char *VERB_STR[NUM_REQUEST_VERB];
void update_client(ftp_client_t* client) {
  assert(client != NULL);

  chdir(client->cwd);
  try_accept_pasv(client);

  switch (client->state) {
    case S_INIT:
      client->verb = INIT;
      client->state = S_WORK_RESPONSE_0;
      execute_command(client);

    case S_CMD:
      if (read_command_buf(client)) {
        parse_command(client);
        client->state = S_WORK_RESPONSE_0;
        execute_command(client);
      }
      break;
    default:
      execute_command(client);
      break;
  }
  realpath(".", client->cwd);
  chdir(client->server->basepath);
  if (client->state == S_QUIT) {
    ftp_server_t *server = client->server;
    if (client->cntl_fd >= 0) {
      if (epoll_ctl(server->epollfd, EPOLL_CTL_DEL, client->cntl_fd, NULL) == -1) {
        perror("epoll_ctl() on cntl_fd in S_QUIT");
      }
      if (shutdown(client->cntl_fd, SHUT_RDWR) == -1) perror("close() on cntl_fd in S_QUIT");
      if (close(client->cntl_fd) == -1) perror("close() on cntl_fd in S_QUIT");
    }
    if (client->data_fd >= 0) {
      if (epoll_ctl(server->epollfd, EPOLL_CTL_DEL, client->data_fd, NULL))
        perror("epoll_ctl() on data_fd in S_QUIT");
      if (shutdown(client->data_fd, SHUT_RDWR) == -1) perror("close() on data_fd in S_QUIT");
      if (close(client->data_fd) == -1) perror("close() on data_fd in S_QUIT");
    }
    if (client->pasv_listen_fd >= 0) {
      if (epoll_ctl(server->epollfd, EPOLL_CTL_DEL, client->pasv_listen_fd, NULL))
        perror("epoll_ctl() on pasv_listen_fd in S_QUIT");
      if (shutdown(client->pasv_listen_fd, SHUT_RDWR) == -1) perror("close() on pasv_listen_fd in S_QUIT");
      if (close(client->pasv_listen_fd) == -1) perror("close() on pasv_listen_fd in S_QUIT");
    }
    free(client);
#pragma clang diagnostic push
#pragma ide diagnostic ignored "DanglingPointer"
    // YES, client is freed, but we need to know all invalid pointers in the current poll round.
    server->closed[server->num_closed++] = client;
#pragma clang diagnostic pop
    server->num_client--;
  }
}