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nbd/client: Drop pointless buf variable

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There's no need to read into a temporary buffer (oversized
since commit 7d3123e1) followed by a byteswap into a uint64_t
to check for a magic number via memcmp(), when the code
immediately below demonstrates reading into the uint64_t then
byteswapping in place and checking for a magic number via
integer math.  What's more, having a different error message
when the server's first reply byte is 0 is unusual - it's no
different from any other wrong magic number, and we already
detected short reads. That whole strlen() issue has been
present and useless since commit 1d45f8b5 in 2010; perhaps it
was leftover debugging (since the correct magic number happens
to be ASCII)?  Make the error messages more consistent and
detailed while touching things.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Richard W.M. Jones <rjones@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20181215135324.152629-9-eblake@redhat.com>
This commit is contained in:
Eric Blake 2018-12-15 07:53:10 -06:00
parent 3c1fa35d74
commit ef2e35fcc8
2 changed files with 9 additions and 16 deletions
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22
nbd/client.c
View File

@ -733,7 +733,6 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char *name,
QIOChannel **outioc, NBDExportInfo *info,
Error **errp)
{
char buf[256];
uint64_t magic;
int rc;
bool zeroes = true;
@ -754,27 +753,20 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char *name,
goto fail;
}
if (nbd_read(ioc, buf, 8, errp) < 0) {
error_prepend(errp, "Failed to read data: ");
if (nbd_read(ioc, &magic, sizeof(magic), errp) < 0) {
error_prepend(errp, "Failed to read initial magic: ");
goto fail;
}
buf[8] = '\0';
if (strlen(buf) == 0) {
error_setg(errp, "Server connection closed unexpectedly");
goto fail;
}
magic = ldq_be_p(buf);
magic = be64_to_cpu(magic);
trace_nbd_receive_negotiate_magic(magic);
if (memcmp(buf, "NBDMAGIC", 8) != 0) {
error_setg(errp, "Invalid magic received");
if (magic != NBD_INIT_MAGIC) {
error_setg(errp, "Bad initial magic received: 0x%" PRIx64, magic);
goto fail;
}
if (nbd_read(ioc, &magic, sizeof(magic), errp) < 0) {
error_prepend(errp, "Failed to read magic: ");
error_prepend(errp, "Failed to read server magic: ");
goto fail;
}
magic = be64_to_cpu(magic);
@ -913,7 +905,7 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char *name,
}
info->flags = oldflags;
} else {
error_setg(errp, "Bad magic received");
error_setg(errp, "Bad server magic received: 0x%" PRIx64, magic);
goto fail;
}

3
nbd/nbd-internal.h
View File

@ -46,8 +46,9 @@
/* Size of oldstyle negotiation */
#define NBD_OLDSTYLE_NEGOTIATE_SIZE (8 + 8 + 8 + 4 + 124)
#define NBD_INIT_MAGIC 0x4e42444d41474943LL /* ASCII "NBDMAGIC" */
#define NBD_REQUEST_MAGIC 0x25609513
#define NBD_OPTS_MAGIC 0x49484156454F5054LL
#define NBD_OPTS_MAGIC 0x49484156454F5054LL /* ASCII "IHAVEOPT" */
#define NBD_CLIENT_MAGIC 0x0000420281861253LL
#define NBD_REP_MAGIC 0x0003e889045565a9LL