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126 строки
2.9 KiB
C
126 строки
2.9 KiB
C
#include "cache.h"
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#include "lockfile.h"
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#include "unix-socket.h"
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#include "unix-stream-server.h"
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#define DEFAULT_LOCK_TIMEOUT (100)
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/*
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* Try to connect to a unix domain socket at `path` (if it exists) and
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* see if there is a server listening.
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*
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* We don't know if the socket exists, whether a server died and
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* failed to cleanup, or whether we have a live server listening, so
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* we "poke" it.
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*
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* We immediately hangup without sending/receiving any data because we
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* don't know anything about the protocol spoken and don't want to
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* block while writing/reading data. It is sufficient to just know
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* that someone is listening.
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*/
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static int is_another_server_alive(const char *path,
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const struct unix_stream_listen_opts *opts)
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{
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int fd = unix_stream_connect(path, opts->disallow_chdir);
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if (fd >= 0) {
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close(fd);
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return 1;
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}
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return 0;
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}
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int unix_ss_create(const char *path,
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const struct unix_stream_listen_opts *opts,
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long timeout_ms,
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struct unix_ss_socket **new_server_socket)
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{
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struct lock_file lock = LOCK_INIT;
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int fd_socket;
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struct unix_ss_socket *server_socket;
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*new_server_socket = NULL;
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if (timeout_ms < 0)
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timeout_ms = DEFAULT_LOCK_TIMEOUT;
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/*
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* Create a lock at "<path>.lock" if we can.
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*/
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if (hold_lock_file_for_update_timeout(&lock, path, 0, timeout_ms) < 0)
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return -1;
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/*
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* If another server is listening on "<path>" give up. We do not
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* want to create a socket and steal future connections from them.
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*/
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if (is_another_server_alive(path, opts)) {
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rollback_lock_file(&lock);
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errno = EADDRINUSE;
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return -2;
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}
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/*
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* Create and bind to a Unix domain socket at "<path>".
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*/
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fd_socket = unix_stream_listen(path, opts);
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if (fd_socket < 0) {
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int saved_errno = errno;
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rollback_lock_file(&lock);
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errno = saved_errno;
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return -1;
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}
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server_socket = xcalloc(1, sizeof(*server_socket));
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server_socket->path_socket = strdup(path);
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server_socket->fd_socket = fd_socket;
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lstat(path, &server_socket->st_socket);
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*new_server_socket = server_socket;
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/*
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* Always rollback (just delete) "<path>.lock" because we already created
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* "<path>" as a socket and do not want to commit_lock to do the atomic
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* rename trick.
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*/
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rollback_lock_file(&lock);
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return 0;
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}
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void unix_ss_free(struct unix_ss_socket *server_socket)
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{
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if (!server_socket)
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return;
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if (server_socket->fd_socket >= 0) {
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if (!unix_ss_was_stolen(server_socket))
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unlink(server_socket->path_socket);
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close(server_socket->fd_socket);
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}
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free(server_socket->path_socket);
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free(server_socket);
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}
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int unix_ss_was_stolen(struct unix_ss_socket *server_socket)
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{
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struct stat st_now;
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if (!server_socket)
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return 0;
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if (lstat(server_socket->path_socket, &st_now) == -1)
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return 1;
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if (st_now.st_ino != server_socket->st_socket.st_ino)
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return 1;
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if (st_now.st_dev != server_socket->st_socket.st_dev)
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return 1;
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if (!S_ISSOCK(st_now.st_mode))
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return 1;
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return 0;
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}
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