path: root/xenscreen.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
#include <time.h>

#include <xs.h>

#include "list.h"
#include "xenstore.h"
#include "apps.h"

/* ------------------------------------------------------------- */

#define BUFSIZE     64
#define PRE_STATE   "%16s: "

struct dom {
    int                domid;
    char               name[BUFSIZE];
    char               tty[BUFSIZE];
    int                connected;
    int                destroyed;
    struct list_head   next;
};
static LIST_HEAD(doms);
static int domcnt;

static char *screenrc       = "/etc/xen/xenscreenrc";
static char *screen_session = "xencon";
static char *screen_title   = "watch";

/* ------------------------------------------------------------- */

static struct dom *find_dom(int domid)
{
    struct dom *dom;
    struct list_head *item;

    list_for_each(item, &doms) {
	dom = list_entry(item, struct dom, next);
	if (dom->domid == domid)
	    return dom;
    }
    return NULL;
}

static struct dom *get_dom(int domid)
{
    struct dom *dom;

    dom = find_dom(domid);
    if (!dom) {
	dom = malloc(sizeof(*dom));
	memset(dom,0,sizeof(*dom));
	dom->domid = domid;
	list_add_tail(&dom->next, &doms);
    }
    return dom;
}

/* ------------------------------------------------------------- */

static int termsig;

static void catchsig(int sig)
{
    termsig = sig;
}

static void try_attach_screen(struct dom *dom, int boot)
{
    int rc;
    
    if (dom->connected)
	return;
    if (!strlen(dom->name))
	return;
    if (!strlen(dom->tty))
	return;

    fprintf(stderr, PRE_STATE "%s (%d) @ %s\n",
	    "connecting", dom->name, dom->domid, dom->tty);

    if (0 != access(dom->tty, R_OK)) {
	fprintf(stderr, "        error: no access to tty %s\n", dom->tty);
	return;
    }

    /* known-racy, but better than nothing ... */
    rc = run_application(1, "fuser", "fuser", "-s", dom->tty, NULL);
    if (0 == rc) {
	fprintf(stderr,"        error: tty %s already in use\n", dom->tty);
	return;
    }

    rc = run_application(1, "screen", "screen",
			 "-X", "-S", screen_session,
			 "screen", "-L", "-t", dom->name, dom->tty,
			 NULL);
#if 0
    /*
     * Hmm, not exactly the most elegant way to do this, has
     * some ugly glitches too.
     *
     * Switches back from the new window to the previous one.
     * Better would be to not switch in the first place,
     * seems screen can't do that though :-(
     */
    if (!boot)
	rc = run_application(1, "screen", "screen",
			     "-X", "-S", screen_session,
			     "other",
			     NULL);
#endif

    dom->connected = 1;
    domcnt++;
}

static void try_release_domain(struct dom *dom)
{
    if (!dom->destroyed)
	return;
    fprintf(stderr, PRE_STATE "%s (%d)%s\n", "disappeared",
	    dom->name, dom->domid, dom->connected ? " [conn]" : "");
    if (dom->connected)
	domcnt--;
    list_del(&dom->next);
    free(dom);
}

static void builtin_screen_setup(void)
{
    static char *config[] = {
	"sorendition =s wb",
	"hardstatus lastline \"%{=b bw} xen |%{-} %-w%{= yb} %50>%n* %t %{-}%+w%<\"",
	"logfile /var/log/xenscreen.%t",
	NULL /* EOF */,
    };
    char cmdline[256];
    int line,try,rc;

#if 1
    /* FIXME: Hmm, doesn't work reliable without that one ... */
    sleep(1);
#endif

    for (line = 0; config[line] != NULL; line++) {
	for (try = 0; try < 5; try++) {
	    snprintf(cmdline, sizeof(cmdline), "screen -X -S %s %s",
		     screen_session, config[line]);
	    rc = run_cmdline(1,cmdline);
	    if (0 == rc)
		break;
	    sleep(1);
	}
    }
}

/* ------------------------------------------------------------- */

int main(int argc, char *argv[])
{
    struct sigaction act,old;
    fd_set set;
    struct xs_handle *xenstore = NULL;
    xs_transaction_t xst;
    char **vec = NULL;
    int domid;
    char path[BUFSIZE], value[BUFSIZE];
    unsigned int count, i, rc;
    struct dom *dom;
    time_t last_ctrl_c = 0;

    if (!have_application("screen")) {
	fprintf(stderr, "screen not installed, exiting\n");
	exit(1);
    }

    if (NULL == getenv("STY") || NULL == strstr(getenv("STY"),screen_session)) {
	/* not running inside screen, try to attach */
	rc = run_application(1, "screen", "screen",
			     "-S", screen_session,
			     "-r", "-p", "=",
			     NULL);
	if (0 == rc)
	    exit(0);

	/* failing that, start a new screen session */
	if (0 != access(screenrc, R_OK))
	    screenrc = "/dev/null";
	execlp("screen", "screen",
	       "-S", screen_session,
	       "-c", screenrc,
	       "-t", screen_title, argv[0],
	       NULL);
	perror("execlp(screen)");
	exit(1);

    } else if (0 != access(screenrc, R_OK)) {
	/* no screenrc: do mini setup */
	builtin_screen_setup();
    }

    /* setup signal handler */
    memset(&act,0,sizeof(act));
    sigemptyset(&act.sa_mask);
    act.sa_handler = catchsig;
    sigaction(SIGTERM,&act,&old);
    sigaction(SIGINT,&act,&old);

    fprintf(stderr,
	    "###\n"
	    "### Xen consoles in screen\n"
	    "### This is the watch process\n"
	    "###\n"
	    "\n");

    /* connect to xenstore */
    xenstore = xenstore_open(1,1,1,1);
    if (NULL == xenstore) {
	fprintf(stderr, "can't access xenstore, exiting\n");
	exit(1);
    }
    xs_watch(xenstore, "/local/domain", "token");

    /* look for running domains */
    if (!(xst = xs_transaction_start(xenstore))) {
	fprintf(stderr,"Oops, can't start xenstore transaction\n");
	exit(1);
    }
    vec = xs_directory(xenstore, xst, "/local/domain", &count);
    xs_transaction_end(xenstore, xst, 0);

    fprintf(stderr,"looking for existing domains\n");
    for (i = 0; i < count; i++) {
	domid = atoi(vec[i]);
	dom = get_dom(domid);
	snprintf(path, sizeof(path), "/local/domain/%d/name", domid);
	xenstore_read(xenstore, path, dom->name, sizeof(dom->name));
	snprintf(path, sizeof(path), "/local/domain/%d/console/tty", domid);
	xenstore_read(xenstore, path, dom->tty, sizeof(dom->tty));
	try_attach_screen(dom, 1);
    }
    rc = run_application(1, "screen", "screen",
			 "-X", "-S", screen_session,
			 "select", "0",
			 NULL);
    rc = run_application(1, "screen", "screen",
			 "-X", "-S", screen_session,
			 "windowlist", "-b",
			 NULL);

    /* main loop */
    fprintf(stderr,"ok, watching out for changes now\n");
    for (;;) {
	if (termsig) {
	    if (!domcnt)
		break;
	    if (time(NULL) - last_ctrl_c < 3)
		break;
	    fprintf(stderr,
		    "\n"
		    "Got ^C - still %d domain(s) active - not quitting.\n"
		    "\n"
		    "You should better use detach instead (^A d).\n"
		    "Or kill all windows (^A \\) if you don't want\n"
		    "keep screen hanging around.\n"
		    "\n"
		    "Hit ^C within 3 secs again to quit nevertheless.\n"
		    "\n",
		    domcnt);
	    last_ctrl_c = time(NULL);
	    termsig = 0;
	}

	FD_ZERO(&set);
	FD_SET(xs_fileno(xenstore), &set);
	switch (select(xs_fileno(xenstore)+1, &set, NULL, NULL, NULL)) {
	case -1:
	    if (EINTR == errno)
		continue; /* termsig check */
	    perror("select");
	    break;
	case 0:
	    fprintf(stderr,"Huh, select() timeout?\n");
	    exit(1);
	    break;
	default:
	    break;
	}
	
	if (vec)
	    free(vec);
	vec = xs_read_watch(xenstore, &count);
	if (NULL == vec) {
	    fprintf(stderr,"xs_read_watch() failed\n");
	    exit(1);
	}
	if (2 != sscanf(vec[XS_WATCH_PATH], "/local/domain/%d/%64s", &domid, path)) {
	    if (1 != sscanf(vec[XS_WATCH_PATH], "/local/domain/%d", &domid))
		continue;
	    strcpy(path, "");
	}
	dom = get_dom(domid);

	if (0 == strcmp(path,"")) {
	    rc = xenstore_read(xenstore, vec[XS_WATCH_PATH], value, sizeof(value));
	    if (0 != rc)
		dom->destroyed = 1;

	} else if (0 == strcmp(path, "console/tty")) {
	    rc = xenstore_read(xenstore, vec[XS_WATCH_PATH], value, sizeof(value));
	    if (0 != rc)
		continue;
	    strcpy(dom->tty, value);

	} else if (0 == strcmp(path, "name")) {
	    rc = xenstore_read(xenstore, vec[XS_WATCH_PATH], value, sizeof(value));
	    if (0 != rc)
		continue;
	    strcpy(dom->name, value);
	    fprintf(stderr, PRE_STATE "%s (%d)\n", "new domain", dom->name, dom->domid);

	} else {
	    continue;

	}

	try_attach_screen(dom, 0);
	try_release_domain(dom);
    }
    return 0;
}