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server.c
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server.c
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#include <assert.h>
#include <netdb.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <syslog.h>
#include <unistd.h>
enum { CMD_SIZE = 100 };
// package type
enum {
DATA_PACKAGE = 0,
OPEN_PACKAGE = 1,
CLOSE_PACKAGE = 2,
};
int create_listener(char *service) {
struct addrinfo *res = NULL;
int gai_err;
struct addrinfo hint = {
.ai_family = AF_UNSPEC,
.ai_socktype = SOCK_STREAM,
.ai_flags = AI_PASSIVE,
};
if ((gai_err = getaddrinfo(NULL, service, &hint, &res))) {
fprintf(stderr, "gai error: %s\n", gai_strerror(gai_err));
return -1;
}
int sock = -1;
for (struct addrinfo *ai = res; ai; ai = ai->ai_next) {
sock = socket(ai->ai_family, ai->ai_socktype, 0);
int one = 1;
setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
if (sock < 0) {
perror("socket");
continue;
}
if (bind(sock, ai->ai_addr, ai->ai_addrlen) < 0) {
perror("bind");
close(sock);
sock = -1;
continue;
}
if (listen(sock, SOMAXCONN) < 0) {
perror("listen");
close(sock);
sock = -1;
continue;
}
break;
}
freeaddrinfo(res);
return sock;
}
struct open_package {
size_t args_count;
char *cmd;
char **args;
};
struct package {
int package_type;
size_t size;
char *data;
};
// OPEN_PACKAGE structure
// args_count len(cmd) cmd len(args[0]) args[0] ...
// len(args[args_count-1]) args[args_count-1] size_t size_t chars
// size_t chars ... size_t chars
int read_open_package(int socket, struct open_package *package) {
ssize_t r;
size_t args_count;
r = recv(socket, &args_count, sizeof(args_count), MSG_WAITALL);
assert(r == sizeof(args_count));
size_t len_cmd;
r = recv(socket, &len_cmd, sizeof(len_cmd), MSG_WAITALL);
assert(r == sizeof(len_cmd));
char *cmd = calloc(len_cmd + 1, sizeof(*cmd));
r = recv(socket, cmd, len_cmd, MSG_WAITALL);
assert(r == len_cmd);
cmd[len_cmd] = '\0';
char **args = calloc(args_count + 2, sizeof(*args));
args[0] = cmd;
args[args_count + 1] = NULL;
for (size_t arg_i = 1; arg_i <= args_count; ++arg_i) {
size_t len_arg;
r = recv(socket, &len_arg, sizeof(len_arg), MSG_WAITALL);
assert(r == sizeof(len_arg));
args[arg_i] = calloc(len_arg + 1, sizeof(*args[arg_i]));
r = recv(socket, args[arg_i], len_arg, MSG_WAITALL);
assert(r == len_arg);
}
package->args_count = args_count;
package->cmd = cmd;
package->args = args;
return 0;
}
volatile int child_finished_flag = 0;
void child_is_done(int sig) {
wait(NULL);
child_finished_flag = 1;
}
// PACKAGE structure
// package_type size data
// int size_t chars
int read_package(int socket, struct package *package) {
ssize_t r;
int package_type;
r = recv(socket, &package_type, sizeof(package_type), MSG_WAITALL);
if (r == -1) {
return 2;
}
assert(r == sizeof(package_type));
size_t size;
r = recv(socket, &size, sizeof(size), MSG_WAITALL);
assert(r == sizeof(size));
char *data = calloc(size, sizeof(*data));
for (size_t i = 0; i < size; ++i) {
r = recv(socket, data + i, sizeof(*data), MSG_WAITALL);
assert(r == sizeof(*data));
}
package->package_type = package_type;
package->size = size;
package->data = data;
if (package->package_type == CLOSE_PACKAGE) {
return 1;
}
return 0;
}
int main(int argc, char *argv[]) {
if (argc != 2) {
fprintf(stderr, "Usage: %s SERVICE\n", argv[0]);
return 1;
}
// make a daemon
pid_t pid = fork();
if (pid < 0) {
fprintf(stderr, "fork error\n");
exit(EXIT_FAILURE);
}
if (pid > 0) {
exit(EXIT_SUCCESS);
}
if (setsid() < 0) {
fprintf(stderr, "setsid error\n");
exit(EXIT_FAILURE);
}
int sock = create_listener(argv[1]);
if (sock < 0) {
fprintf(stderr, "create_listener error\n");
exit(EXIT_FAILURE);
}
while (1) {
int connection = accept(sock, NULL, NULL);
pid_t cmd_executor = fork();
if (cmd_executor < 0) {
fprintf(stderr, "executor error\n");
exit(EXIT_FAILURE);
}
if (cmd_executor == 0) {
// read open package
struct open_package *op;
op = malloc(sizeof(*op));
if (read_open_package(connection, op)) {
fprintf(stderr, "read open package error\n");
exit(EXIT_FAILURE);
}
int fd_write_handler[2];
int p = pipe(fd_write_handler);
if (p == -1) {
fprintf(stderr, "pipe error\n");
exit(EXIT_FAILURE);
}
// executor fork----> executor ----------\ //
// \ || \ //
// \ || pipe \ //
// \ || > //
// ---> package_handler <--- client
pid_t executor_process = fork();
if (executor_process < 0) {
fprintf(stderr, "fork package handler error\n");
exit(EXIT_FAILURE);
}
if (executor_process > 0) {
// package_handler
struct sigaction sa_sigchld = {.sa_handler = child_is_done};
sigaction(SIGCHLD, &sa_sigchld, NULL);
// reading packages until "STOP package"
// sending them to executor
struct package *p;
p = malloc(sizeof(*p));
while (!child_finished_flag && !read_package(connection, p)) {
ssize_t r = write(fd_write_handler[1], p->data, p->size);
if (r != p->size) {
fprintf(stderr, "written %ld, expected %ld\n", r,
p->size);
exit(EXIT_FAILURE);
}
}
assert(p->package_type == CLOSE_PACKAGE || child_finished_flag);
if (p->package_type == CLOSE_PACKAGE) {
kill(executor_process, SIGKILL);
}
close(connection);
exit(EXIT_SUCCESS);
} else {
// executor
int client_socket_out = dup(connection);
// dup out to socket
dup2(client_socket_out, STDOUT_FILENO);
dup2(client_socket_out, STDERR_FILENO);
// dup in from pipe from package_handler
dup2(fd_write_handler[0], STDIN_FILENO);
close(connection);
close(client_socket_out);
// execvp(cmd, args)
execvp(op->cmd, op->args);
fprintf(stderr, "execvp fail\n");
exit(EXIT_FAILURE);
}
}
close(connection);
}
}