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block: Call attention to truncation of long NBD exports 

Commit 93676c88 relaxed our NBD client code to request export names up
to the NBD protocol maximum of 4096 bytes without NUL terminator, even
though the block layer can't store anything longer than 4096 bytes
including NUL terminator for display to the user.  Since this means
there are some export names where we have to truncate things, we can
at least try to make the truncation a bit more obvious for the user.
Note that in spite of the truncated display name, we can still
communicate with an NBD server using such a long export name; this was
deemed nicer than refusing to even connect to such a server (since the
server may not be under our control, and since determining our actual
length limits gets tricky when nbd://host:port/export and
nbd+unix:///export?socket=/path are themselves variable-length
expansions beyond the export name but count towards the block layer
name length).

Reported-by: Xueqiang Wei <xuwei@redhat.com>
Fixes: https://bugzilla.redhat.com/1843684
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20200610163741.3745251-3-eblake@redhat.com>
This commit is contained in:
Eric Blake 2020-06-08 13:26:38 -05:00
parent 5c4fe018c0
commit 5c86bdf120
2 changed files with 18 additions and 10 deletions
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7
block.c
View File

@ -6809,8 +6809,11 @@ void bdrv_refresh_filename(BlockDriverState *bs)
pstrcpy(bs->filename, sizeof(bs->filename), bs->exact_filename);
} else {
QString *json = qobject_to_json(QOBJECT(bs->full_open_options));
snprintf(bs->filename, sizeof(bs->filename), "json:%s",
qstring_get_str(json));
if (snprintf(bs->filename, sizeof(bs->filename), "json:%s",
qstring_get_str(json)) >= sizeof(bs->filename)) {
/* Give user a hint if we truncated things. */
strcpy(bs->filename + sizeof(bs->filename) - 4, "...");
}
qobject_unref(json);
}
}

21
block/nbd.c
View File

@ -1984,6 +1984,7 @@ static void nbd_refresh_filename(BlockDriverState *bs)
{
BDRVNBDState *s = bs->opaque;
const char *host = NULL, *port = NULL, *path = NULL;
size_t len = 0;
if (s->saddr->type == SOCKET_ADDRESS_TYPE_INET) {
const InetSocketAddress *inet = &s->saddr->u.inet;
@ -1996,17 +1997,21 @@ static void nbd_refresh_filename(BlockDriverState *bs)
} /* else can't represent as pseudo-filename */
if (path && s->export) {
snprintf(bs->exact_filename, sizeof(bs->exact_filename),
"nbd+unix:///%s?socket=%s", s->export, path);
len = snprintf(bs->exact_filename, sizeof(bs->exact_filename),
"nbd+unix:///%s?socket=%s", s->export, path);
} else if (path && !s->export) {
snprintf(bs->exact_filename, sizeof(bs->exact_filename),
"nbd+unix://?socket=%s", path);
len = snprintf(bs->exact_filename, sizeof(bs->exact_filename),
"nbd+unix://?socket=%s", path);
} else if (host && s->export) {
snprintf(bs->exact_filename, sizeof(bs->exact_filename),
"nbd://%s:%s/%s", host, port, s->export);
len = snprintf(bs->exact_filename, sizeof(bs->exact_filename),
"nbd://%s:%s/%s", host, port, s->export);
} else if (host && !s->export) {
snprintf(bs->exact_filename, sizeof(bs->exact_filename),
"nbd://%s:%s", host, port);
len = snprintf(bs->exact_filename, sizeof(bs->exact_filename),
"nbd://%s:%s", host, port);
}
if (len > sizeof(bs->exact_filename)) {
/* Name is too long to represent exactly, so leave it empty. */
bs->exact_filename[0] = '\0';
}
}