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https://github.com/fish-shell/fish-shell
synced 2024-12-26 04:43:10 +00:00
Critical section locking for fishd
darcs-hash:20050928014309-344c5-92a1e5aa31eceacc4f76cdb2638358d1014c2e3f.gz
This commit is contained in:
netocrat
parent
67f20b9b16
commit
6f08ee51e8
3 changed files with 164 additions and 42 deletions
41
common.c
41
common.c
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@ -19,6 +19,8 @@ parts of fish.
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#include <signal.h>
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#include <locale.h>
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#include <time.h>
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#include <sys/time.h>
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#include <fcntl.h>
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#if HAVE_NCURSES_H
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#include <ncurses.h>
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@ -52,6 +54,12 @@ parts of fish.
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*/
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#define ERROR_MAX_COUNT 1
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/**
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The number of nanoseconds to wait between polls when attempting to acquire
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a lockfile
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*/
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#define LOCKPOLLINTERVAL 1000000
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struct termios shell_modes;
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/**
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@ -1062,3 +1070,36 @@ wchar_t *unescape( wchar_t * in, int escape_special )
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return in;
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}
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/**
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Attempt to acquire a lock based on a lockfile, waiting LOCKPOLLINTERVAL
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nanoseconds between polls and timing out after timeout seconds,
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thereafter forcibly attempting to obtain the lock. Returns the opened
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lockfile's descriptor or -1 if not possible to open the file or on error.
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Contains a race condition when the lockfile is on an NFS filesystem
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according to Linux manpage open(2)
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*/
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int acquire_lock_file(const char *lockfile, const int timeout)
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{
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int ret = -1;
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struct timespec pollint;
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struct timeval start, end;
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double elapsed;
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if (gettimeofday(&start, NULL) == 0) {
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pollint.tv_sec = 0;
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pollint.tv_nsec = LOCKPOLLINTERVAL;
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while ((ret = open(lockfile, O_EXCL|O_CREAT|O_RDONLY)) == -1) {
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if (gettimeofday(&end, NULL) != 0)
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break;
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elapsed = end.tv_sec + end.tv_usec/1000000.0 -
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(start.tv_sec + start.tv_usec/1000000.0);
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if (elapsed >= timeout) {
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(void)unlink(lockfile);
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ret = open(lockfile, O_EXCL|O_CREAT|O_RDONLY);
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break;
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}
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(void)nanosleep(&pollint, NULL);
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}
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}
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return ret;
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}
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2
common.h
2
common.h
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@ -246,3 +246,5 @@ wchar_t *unescape( wchar_t * in, int escape_special );
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void block();
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void unblock();
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int acquire_lock_file(const char *lockfile, const int timeout);
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163
fishd.c
163
fishd.c
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@ -50,6 +50,16 @@ down and save.
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*/
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#define HOSTNAME_LEN 32
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/**
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The string to append to the socket name to name the lockfile
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*/
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#define LOCKPOSTFIX ".lock"
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/**
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The timeout in seconds on the lockfile for critical section
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*/
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#define LOCKTIMEOUT 1
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/**
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The list of connections to clients
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*/
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@ -61,55 +71,112 @@ static connection_t *conn;
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static int sock;
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/**
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Connects to the fish socket
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Constructs the fish socket filename
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*/
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static int get_socket()
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static char *get_socket_filename(void)
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{
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int s, len;
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struct sockaddr_un local;
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char *name;
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char *dir = getenv( "FISHD_SOCKET_DIR" );
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char *uname = getenv( "USER" );
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char *dir = getenv("FISHD_SOCKET_DIR");
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char *uname = getenv("USER");
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if( !dir )
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if (dir == NULL)
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dir = "/tmp";
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if( uname==0 )
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{
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struct passwd *pw;
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pw = getpwuid( getuid() );
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uname = strdup( pw->pw_name );
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}
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name = malloc( strlen(dir)+ strlen(uname)+ strlen(SOCK_FILENAME) + 2 );
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strcpy( name, dir );
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strcat( name, "/" );
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strcat( name, SOCK_FILENAME );
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strcat( name, uname );
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if( strlen( name ) >= UNIX_PATH_MAX )
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{
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debug( 1, L"Filename too long: '%s'", name );
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exit(1);
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if (uname == NULL) {
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struct passwd *pw;
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pw = getpwuid(getuid());
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uname = strdup(pw->pw_name);
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}
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name = malloc(strlen(dir)+ strlen(uname)+ strlen(SOCK_FILENAME) + 2);
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if (name == NULL) {
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perror("get_socket_filename");
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exit(EXIT_FAILURE);
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}
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strcpy(name, dir);
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strcat(name, "/");
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strcat(name, SOCK_FILENAME);
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strcat(name, uname);
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if (strlen(name) >= UNIX_PATH_MAX) {
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debug(1, L"Filename too long: '%s'", name);
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exit(EXIT_FAILURE);
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}
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return name;
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}
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/**
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Acquire the lock file for the socket
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Returns an fd that should be closed to unlock
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*/
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int acquire_socket_lock_file(const char *sock_name, char **lockfile)
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{
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int fd;
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int len = strlen(sock_name);
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*lockfile = malloc(len + strlen(LOCKPOSTFIX) + 1);
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if (*lockfile == NULL) {
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perror("get_socket");
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exit(EXIT_FAILURE);
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}
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(void)strcpy(*lockfile, sock_name);
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(void)strcpy(*lockfile + len, LOCKPOSTFIX);
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if ((fd = acquire_lock_file(*lockfile, LOCKTIMEOUT)) == -1) {
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fprintf(stderr, "Unable to obtain lockfile %s, exiting",
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*lockfile);
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exit(EXIT_FAILURE);
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}
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return fd;
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}
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/**
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Connects to the fish socket and starts listening for connections
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*/
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static int get_socket(void)
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{
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int s, len, doexit = 0;
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int exitcode = EXIT_FAILURE;
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struct sockaddr_un local;
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char *lockfile;
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char *sock_name = get_socket_filename();
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int fd_lockfile;
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/**
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Start critical section protected by lock file
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*/
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fd_lockfile = acquire_socket_lock_file(sock_name, &lockfile);
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debug(1, L"Acquired lockfile %s", lockfile);
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debug( 1, L"Connect to socket at %s", name );
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local.sun_family = AF_UNIX;
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strcpy(local.sun_path, sock_name);
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len = strlen(local.sun_path) + sizeof(local.sun_family);
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debug(1, L"Connect to socket at %s", sock_name);
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if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) == -1) {
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perror("socket");
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exit(1);
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doexit = 1;
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goto unlock;
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}
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/**
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First check whether the socket has been opened by another fishd;
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if so, exit with success status
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*/
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if (connect(s, (struct sockaddr *)&local, len) == 0) {
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debug(1, L"Socket already exists, exiting");
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doexit = 1;
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exitcode = 0;
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goto unlock;
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}
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local.sun_family = AF_UNIX;
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strcpy(local.sun_path, name );
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unlink(local.sun_path);
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len = strlen(local.sun_path) + sizeof(local.sun_family);
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free( name );
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if (bind(s, (struct sockaddr *)&local, len) == -1) {
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perror("bind");
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exit(1);
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doexit = 1;
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goto unlock;
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}
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/*
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if( setsockopt( s, SOL_SOCKET, SO_PASSCRED, &on, sizeof( on ) ) )
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{
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@ -118,14 +185,30 @@ static int get_socket()
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}
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*/
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if( fcntl( s, F_SETFL, O_NONBLOCK ) != 0 )
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{
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if( fcntl( s, F_SETFL, O_NONBLOCK ) != 0 ) {
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wperror( L"fcntl" );
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close( s );
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return -1;
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close( s );
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doexit = 1;
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} else if (listen(s, 64) == -1) {
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wperror(L"listen");
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doexit = 1;
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}
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unlock:
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(void)close(fd_lockfile);
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(void)unlink(lockfile);
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debug(1, L"Released lockfile %s", lockfile);
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/**
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End critical section protected by lock file
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*/
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free(lockfile);
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free(sock_name);
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if (doexit)
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exit(exitcode);
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return s;
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}
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@ -277,12 +360,8 @@ static void save()
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static void init()
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{
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program_name=L"fishd";
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sock = get_socket();
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if (listen(sock, 64) == -1)
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{
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wperror(L"listen");
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exit(1);
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}
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daemonize();
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