Once again thanks for replying, I appreciate your patience.
Actually I already realized that mistake and replaced "daemon_open" with
"domain_open".
But getting the "unknown error" has now changed into a "segmentation
fault" and apparently
it occurs after i execute the "xs_directory" function to get the path in
buf2 variable (line31 below).
I checked the value of 'len' variable after the call and it turns out to
be arbitrarily large.
What am I doing wrong here ? After replacing "daemon_open" with
"domain_open" all the rest
of the calls to xs.h functions remain the same or are there specific
"daemon" and "domain"
versions of functions? (apparently its the former case)
A few related questions:
-Are there any specific initializations/calls that need to be made from
inside domU to first initialize
and then access xenstore ? Or the functions exposed by xs.h are the only
thing required ? Apparently
xenstore is initialized by dom0 once at startup only.
-Does ability to communicate with xenstore depend on whether the ethernet
interface b/w
dom0 and domU is working or not (since it uses sockets)? Currently my domU
can't ping dom0 or any one else
for that matter.
-I am trying to only read the xenstore(which is allowed to all domains by
default), does my problem
in anyway relate to xenstore access permissions ?
-Are you aware of any user-space management tools available that access
xenstore from within domU?
Sorry for a detailed mail but I am just a beginner and dont know a lot of
stuff.
I'll appreciate your help once again.
-------------------------------------------------------------------------------------------
1 #include <xs.h>
2 #include <sys/types.h>
3 #include <stdio.h>
4 #include <string.h>
5
6 void main(int argc, char *argv[])
7 {
8
9 struct xs_handle *xs;
10 xs_transaction_t th;
11 char *path;
12 int fd;
13 fd_set set;
14 int er;
15 struct timeval tv = {.tv_sec = 0, .tv_usec = 0 };
16 char **vec;
17 unsigned int num;
18 char * buf;
19 char ** buf2;
20 unsigned int len;
21
22 unsigned int domid;
23
24 printf("Msg1\n");
25
26 /* Get a connection to the daemon */
27 xs = xs_domain_open();
28 if ( xs == NULL ) error();
29
30 th = xs_transaction_start(xs);
31 buf2 = xs_directory(xs, th,"/local/domain", &len);
32 xs_transaction_end(xs, th, true);
33
34 int i=0;
35
36 for(i=0;i<len;i++)
37 {
38 printf("%s\n",buf2[i]);
39 }
40
41
42 // I am running dom0 and oly 1 domU so this condition chooses one of
them
43 if(len>1)
44 domid = atoi(buf2[1]);
45 if(len==1)
46 domid = atoi(buf2[0]);
47 //sprintf( domid, "%ui", buf2[0] );
48
49 printf("Domid: %i\n", domid);
50
51 /* Get the local domain path */
52 path = xs_get_domain_path(xs, domid);
53 if ( path == NULL ) error();
54
55 printf("Msg3\n");
56
57 /* Make space for our node on the path */
58 path = realloc(path, strlen(path) + strlen("/memory/target") + 1);
59 if ( path == NULL ) error();
60 strcat(path, "/memory/target");
61
62 /* Create a watch on /local/domain/%d/mynode. */
63 er = xs_watch(xs, path, "mytoken");
64 if ( er == 0 ) error();
65
66 /* We are notified of read availability on the watch via the
67 * file descriptor.
68 */
69 fd = xs_fileno(xs);
70
71 while (1)
72 {
73 FD_ZERO(&set);
74 FD_SET(fd, &set);
75
76 /* Poll for data. */
77 if ( select(fd + 1, &set, NULL, NULL, &tv) > 0
78 && FD_ISSET(fd, &set))
79 {
80 /* I am not sure how num works -- please describe. */
81 vec = xs_read_watch(xs, &num);
82 if ( !vec ) error();
83 printf("vec contents: %s|%s\n", vec[XS_WATCH_PATH],
84 vec[XS_WATCH_TOKEN]);
85
86 /* Prepare a transaction and do a read. */
87 th = xs_transaction_start(xs);
88 buf = xs_read(xs, th, vec[XS_WATCH_PATH], &len);
89 xs_transaction_end(xs, th, true);
90 if ( buf )
91 {
92 printf("buflen: %d\nbuf: %s\n", len, buf);
93 }
94
95 /* Prepare a transaction and do a write. */
96 /*th = xs_transaction_start(xs);
97
98 er = xs_write(xs, th, path, "somestuff", strlen("somestuff"));
99 xs_transaction_end(xs, th, true);
100 if ( er == 0 ) error();*/
101 }
102 }
103
104 /* Cleanup */
105 close(fd);
106 xs_daemon_close(xs);
107 free(path);
108
109 }
----- Original Message -----
From: "Vincent Hanquez" <vincent@xxxxxxxxxxxxx>
To: "Umar Farooq Minhas" <umarfm13@xxxxxxxxxxx>
Cc: <aball@xxxxxxxxxxxxxxxxxx>; <xen-devel@xxxxxxxxxxxxxxxxxxx>
Sent: Wednesday, November 22, 2006 10:52 AM
Subject: Re: [Xen-devel] Regarding Xenstore/Xenbus
On Mon, Nov 20, 2006 at 08:21:20PM -0500, Umar Farooq Minhas wrote:
Thanks for your reply. I was into trying out xenstore acess using
'libxenstore.so'. I have copied the exact code that I am trying to run
(most of this comes from xenstore wiki). The issue is that I am able to
run
this code from dom0 but when I try to run it from inside a domU after
the
first printf output i.e. "Msg1" it terminates abnormally saying "unknown
error". My guess is that its failing when it calls xs_daemon_open(). I
can't figure out what am i missing. Some processes need to be started
before i can acess xenstore? Are there any packages that need to be
installed in domU to access xenstore? I already have 'xen-devel',
'xen-lib'
and 'xen-tools' packages installed inside domU. Please help.
you need to use "domain_open" instead of "daemon_open" in domU.
daemon_open is using a direct unix socket to communicate with xenstored.
this socket is only accessible to dom0. domU need to use the other way
to communicate with xenstored.
Cheers,
--
Vincent Hanquez
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