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/*
ulockmgr_server: Userspace Lock Manager Server
Copyright (C) 2006 Miklos Szeredi <miklos@szeredi.hu>
This program can be distributed under the terms of the GNU GPL.
See the file COPYING.
*/
/* #define DEBUG 1 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <dirent.h>
#include <pthread.h>
#include <stdint.h>
#include <errno.h>
#include <assert.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/wait.h>
struct message {
unsigned intr : 1;
unsigned nofd : 1;
pthread_t thr;
int cmd;
int fd;
struct flock lock;
int error;
};
struct fd_store {
struct fd_store *next;
int fd;
int origfd;
int inuse;
};
struct owner {
struct fd_store *fds;
pthread_mutex_t lock;
};
struct req_data {
struct owner *o;
int cfd;
struct fd_store *f;
struct message msg;
};
#define MAX_SEND_FDS 2
static int receive_message(int sock, void *buf, size_t buflen, int *fdp,
int *numfds)
{
struct msghdr msg;
struct iovec iov;
size_t ccmsg[CMSG_SPACE(sizeof(int) * MAX_SEND_FDS) / sizeof(size_t)];
struct cmsghdr *cmsg;
int res;
int i;
assert(*numfds <= MAX_SEND_FDS);
iov.iov_base = buf;
iov.iov_len = buflen;
memset(&msg, 0, sizeof(msg));
memset(ccmsg, -1, sizeof(ccmsg));
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
msg.msg_control = ccmsg;
msg.msg_controllen = sizeof(ccmsg);
res = recvmsg(sock, &msg, MSG_WAITALL);
if (!res) {
/* retry on zero return, see do_recv() in ulockmgr.c */
res = recvmsg(sock, &msg, MSG_WAITALL);
if (!res)
return 0;
}
if (res == -1) {
perror("ulockmgr_server: recvmsg");
return -1;
}
if ((size_t) res != buflen) {
fprintf(stderr, "ulockmgr_server: short message received\n");
return -1;
}
cmsg = CMSG_FIRSTHDR(&msg);
if (cmsg) {
if (cmsg->cmsg_type != SCM_RIGHTS) {
fprintf(stderr,
"ulockmgr_server: unknown control message %d\n",
cmsg->cmsg_type);
return -1;
}
memcpy(fdp, CMSG_DATA(cmsg), sizeof(int) * *numfds);
if (msg.msg_flags & MSG_CTRUNC) {
fprintf(stderr,
"ulockmgr_server: control message truncated\n");
for (i = 0; i < *numfds; i++)
close(fdp[i]);
*numfds = 0;
}
} else {
if (msg.msg_flags & MSG_CTRUNC) {
fprintf(stderr,
"ulockmgr_server: control message truncated(*)\n");
/* There's a bug in the Linux kernel, that if
not all file descriptors were allocated,
then the cmsg header is not filled in */
cmsg = (struct cmsghdr *) ccmsg;
memcpy(fdp, CMSG_DATA(cmsg), sizeof(int) * *numfds);
for (i = 0; i < *numfds; i++)
close(fdp[i]);
}
*numfds = 0;
}
return res;
}
static int closefrom(int minfd)
{
DIR *dir = opendir("/proc/self/fd");
if (dir) {
int dfd = dirfd(dir);
struct dirent *ent;
while ((ent = readdir(dir))) {
char *end;
int fd = strtol(ent->d_name, &end, 10);
if (ent->d_name[0] && !end[0] && fd >= minfd &&
fd != dfd)
close(fd);
}
closedir(dir);
}
return 0;
}
static void send_reply(int cfd, struct message *msg)
{
int res = send(cfd, msg, sizeof(struct message), MSG_NOSIGNAL);
if (res == -1)
perror("ulockmgr_server: sending reply");
#ifdef DEBUG
fprintf(stderr, "ulockmgr_server: error: %i\n", msg->error);
#endif
}
static void *process_request(void *d_)
{
struct req_data *d = d_;
int res;
assert(d->msg.cmd == F_SETLKW);
res = fcntl(d->f->fd, F_SETLK, &d->msg.lock);
if (res == -1 && errno == EAGAIN) {
d->msg.error = EAGAIN;
d->msg.thr = pthread_self();
send_reply(d->cfd, &d->msg);
res = fcntl(d->f->fd, F_SETLKW, &d->msg.lock);
}
d->msg.error = (res == -1) ? errno : 0;
pthread_mutex_lock(&d->o->lock);
d->f->inuse--;
pthread_mutex_unlock(&d->o->lock);
send_reply(d->cfd, &d->msg);
close(d->cfd);
free(d);
return NULL;
}
static void process_message(struct owner *o, struct message *msg, int cfd,
int fd)
{
struct fd_store *f = NULL;
struct fd_store *newf = NULL;
struct fd_store **fp;
struct req_data *d;
pthread_t tid;
int res;
#ifdef DEBUG
fprintf(stderr, "ulockmgr_server: %i %i %i %lli %lli\n",
msg->cmd, msg->lock.l_type, msg->lock.l_whence,
msg->lock.l_start, msg->lock.l_len);
#endif
if (msg->cmd == F_SETLK && msg->lock.l_type == F_UNLCK &&
msg->lock.l_start == 0 && msg->lock.l_len == 0) {
for (fp = &o->fds; *fp;) {
f = *fp;
if (f->origfd == msg->fd && !f->inuse) {
close(f->fd);
*fp = f->next;
free(f);
} else
fp = &f->next;
}
if (!msg->nofd)
close(fd);
msg->error = 0;
send_reply(cfd, msg);
close(cfd);
return;
}
if (msg->nofd) {
for (fp = &o->fds; *fp; fp = &(*fp)->next) {
f = *fp;
if (f->origfd == msg->fd)
break;
}
if (!*fp) {
fprintf(stderr, "ulockmgr_server: fd %i not found\n",
msg->fd);
msg->error = EIO;
send_reply(cfd, msg);
close(cfd);
return;
}
} else {
newf = f = malloc(sizeof(struct fd_store));
if (!f) {
msg->error = ENOLCK;
send_reply(cfd, msg);
close(cfd);
return;
}
f->fd = fd;
f->origfd = msg->fd;
f->inuse = 0;
}
if (msg->cmd == F_GETLK || msg->cmd == F_SETLK ||
msg->lock.l_type == F_UNLCK) {
res = fcntl(f->fd, msg->cmd, &msg->lock);
msg->error = (res == -1) ? errno : 0;
send_reply(cfd, msg);
close(cfd);
if (newf) {
newf->next = o->fds;
o->fds = newf;
}
return;
}
d = malloc(sizeof(struct req_data));
if (!d) {
msg->error = ENOLCK;
send_reply(cfd, msg);
close(cfd);
free(newf);
return;
}
f->inuse++;
d->o = o;
d->cfd = cfd;
d->f = f;
d->msg = *msg;
res = pthread_create(&tid, NULL, process_request, d);
if (res) {
msg->error = ENOLCK;
send_reply(cfd, msg);
close(cfd);
free(d);
f->inuse--;
free(newf);
return;
}
if (newf) {
newf->next = o->fds;
o->fds = newf;
}
pthread_detach(tid);
}
static void sigusr1_handler(int sig)
{
(void) sig;
/* Nothing to do */
}
static void process_owner(int cfd)
{
struct owner o;
struct sigaction sa;
memset(&sa, 0, sizeof(struct sigaction));
sa.sa_handler = sigusr1_handler;
sigemptyset(&sa.sa_mask);
if (sigaction(SIGUSR1, &sa, NULL) == -1) {
perror("ulockmgr_server: cannot set sigusr1 signal handler");
exit(1);
}
memset(&o, 0, sizeof(struct owner));
pthread_mutex_init(&o.lock, NULL);
while (1) {
struct message msg;
int rfds[2];
int res;
int numfds = 2;
res = receive_message(cfd, &msg, sizeof(msg), rfds, &numfds);
if (!res)
break;
if (res == -1)
exit(1);
if (msg.intr) {
if (numfds != 0)
fprintf(stderr,
"ulockmgr_server: too many fds for intr\n");
pthread_kill(msg.thr, SIGUSR1);
} else {
if (numfds != 2)
continue;
pthread_mutex_lock(&o.lock);
process_message(&o, &msg, rfds[0], rfds[1]);
pthread_mutex_unlock(&o.lock);
}
}
if (o.fds)
fprintf(stderr,
"ulockmgr_server: open file descriptors on exit\n");
}
int main(int argc, char *argv[])
{
int nullfd;
char *end;
int cfd;
sigset_t empty;
if (argc != 2 || !argv[1][0])
goto out_inval;
cfd = strtol(argv[1], &end, 10);
if (*end)
goto out_inval;
/* demonize current process */
switch(fork()) {
case -1:
perror("ulockmgr_server: fork");
exit(1);
case 0:
break;
default:
_exit(0);
}
if (setsid() == -1) {
perror("ulockmgr_server: setsid");
exit(1);
}
(void) chdir("/");
sigemptyset(&empty);
sigprocmask(SIG_SETMASK, &empty, NULL);
if (dup2(cfd, 4) == -1) {
perror("ulockmgr_server: dup2");
exit(1);
}
cfd = 4;
nullfd = open("/dev/null", O_RDWR);
if (nullfd >= 0) {
dup2(nullfd, 0);
dup2(nullfd, 1);
}
close(3);
closefrom(5);
while (1) {
char c;
int sock;
int pid;
int numfds = 1;
int res = receive_message(cfd, &c, sizeof(c), &sock, &numfds);
if (!res)
break;
if (res == -1)
exit(1);
assert(numfds == 1);
pid = fork();
if (pid == -1) {
perror("ulockmgr_server: fork");
close(sock);
continue;
}
if (pid == 0) {
close(cfd);
pid = fork();
if (pid == -1) {
perror("ulockmgr_server: fork");
_exit(1);
}
if (pid == 0)
process_owner(sock);
_exit(0);
}
waitpid(pid, NULL, 0);
close(sock);
}
return 0;
out_inval:
fprintf(stderr, "%s should be started by libulockmgr\n", argv[0]);
return 1;
}