xen screen management tool

1 files changed, 273 insertions, 0 deletions

diff --git a/xenscreen.c b/xenscreen.c
new file mode 100644
index 0000000..e091976
--- /dev/null
+++ b/xenscreen.c
@@ -0,0 +1,273 @@
+#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
+
+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 *screenrc       = "/home/kraxel/projects/xenwatch/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 rc;
+    
+    if (dom->connected)
+	return;
+    if (!strlen(dom->name))
+	return;
+    if (!strlen(dom->tty))
+	return;
+
+    fprintf(stderr,"    conn: %s (%d) @ %s\n",
+	    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;
+    }
+
+    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", "-t", dom->name, dom->tty,
+			 NULL);
+    dom->connected = 1;
+    domcnt++;
+}
+
+static void try_release_domain(struct dom *dom)
+{
+    if (!dom->destroyed)
+	return;
+    fprintf(stderr,"    gone: %s (%d)%s\n", dom->name, dom->domid,
+	    dom->connected ? " [conn]" : "");
+    if (dom->connected)
+	domcnt--;
+    list_del(&dom->next);
+    free(dom);
+}
+
+/* ------------------------------------------------------------- */
+
+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 */
+	rc = run_application(1,"screen", "screen",
+			     "-d", "-m",
+			     "-S", screen_session,
+			     "-c", screenrc,
+			     "-t", screen_title, argv[0],
+			     NULL);
+	execlp("screen", "screen",
+	       "-S", screen_session,
+	       "-r", "-p", "=",
+	       NULL);
+	perror("execlp(screen)");
+	exit(1);
+    }
+
+    /* 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);
+    }
+
+    /* main loop */
+    fprintf(stderr,"... done, watching for new ones appear\n");
+    for (;;) {
+	if (termsig) {
+	    if (!domcnt)
+		break;
+	    if (time(NULL) - last_ctrl_c < 3)
+		break;
+	    fprintf(stderr,"Still %d domain(s) active - not quitting.\n", domcnt);
+	    fprintf(stderr,"Better try detach instead (Ctrl-A d).\n");
+	    fprintf(stderr,"Hit Ctrl-C within 3 secs again to quit nevertheless.\n");
+	    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,"    boot: %s (%d)\n", dom->name, dom->domid);
+
+	} else {
+	    continue;
+
+	}
+
+	try_attach_screen(dom);
+	try_release_domain(dom);
+    }
+    return 0;
+}