nbd: Treat flags vs. command type as separate fields
Current upstream NBD documents that requests have a 16-bit flags,
followed by a 16-bit type integer; although older versions mentioned
only a 32-bit field with masking to find flags. Since the protocol
is in network order (big-endian over the wire), the ABI is unchanged;
but dealing with the flags as a separate field rather than masking
will make it easier to add support for upcoming NBD extensions that
increase the number of both flags and commands.
Improve some comments in nbd.h based on the current upstream
NBD protocol (https://github.com/yoe/nbd/blob/master/doc/proto.md),
and touch some nearby code to keep checkpatch.pl happy.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1476469998-28592-3-git-send-email-eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/block/nbd-client.c b/block/nbd-client.c
index 40b28ab..8ca5030 100644
--- a/block/nbd-client.c
+++ b/block/nbd-client.c
@@ -1,6 +1,7 @@
/*
* QEMU Block driver for NBD
*
+ * Copyright (C) 2016 Red Hat, Inc.
* Copyright (C) 2008 Bull S.A.S.
* Author: Laurent Vivier <Laurent.Vivier@bull.net>
*
@@ -258,7 +259,7 @@
if (flags & BDRV_REQ_FUA) {
assert(client->nbdflags & NBD_FLAG_SEND_FUA);
- request.type |= NBD_CMD_FLAG_FUA;
+ request.flags |= NBD_CMD_FLAG_FUA;
}
assert(bytes <= NBD_MAX_BUFFER_SIZE);
@@ -343,11 +344,7 @@
void nbd_client_close(BlockDriverState *bs)
{
NbdClientSession *client = nbd_get_client_session(bs);
- struct nbd_request request = {
- .type = NBD_CMD_DISC,
- .from = 0,
- .len = 0
- };
+ struct nbd_request request = { .type = NBD_CMD_DISC };
if (client->ioc == NULL) {
return;
diff --git a/include/block/nbd.h b/include/block/nbd.h
index fd58390..5fe2670 100644
--- a/include/block/nbd.h
+++ b/include/block/nbd.h
@@ -1,4 +1,5 @@
/*
+ * Copyright (C) 2016 Red Hat, Inc.
* Copyright (C) 2005 Anthony Liguori <anthony@codemonkey.ws>
*
* Network Block Device
@@ -32,7 +33,8 @@
uint64_t handle;
uint64_t from;
uint32_t len;
- uint32_t type;
+ uint16_t flags;
+ uint16_t type;
};
struct nbd_reply {
@@ -40,6 +42,8 @@
uint32_t error;
};
+/* Transmission (export) flags: sent from server to client during handshake,
+ but describe what will happen during transmission */
#define NBD_FLAG_HAS_FLAGS (1 << 0) /* Flags are there */
#define NBD_FLAG_READ_ONLY (1 << 1) /* Device is read-only */
#define NBD_FLAG_SEND_FLUSH (1 << 2) /* Send FLUSH */
@@ -47,10 +51,12 @@
#define NBD_FLAG_ROTATIONAL (1 << 4) /* Use elevator algorithm - rotational media */
#define NBD_FLAG_SEND_TRIM (1 << 5) /* Send TRIM (discard) */
-/* New-style global flags. */
+/* New-style handshake (global) flags, sent from server to client, and
+ control what will happen during handshake phase. */
#define NBD_FLAG_FIXED_NEWSTYLE (1 << 0) /* Fixed newstyle protocol. */
-/* New-style client flags. */
+/* New-style client flags, sent from client to server to control what happens
+ during handshake phase. */
#define NBD_FLAG_C_FIXED_NEWSTYLE (1 << 0) /* Fixed newstyle protocol. */
/* Reply types. */
@@ -61,10 +67,10 @@
#define NBD_REP_ERR_INVALID ((UINT32_C(1) << 31) | 3) /* Invalid length. */
#define NBD_REP_ERR_TLS_REQD ((UINT32_C(1) << 31) | 5) /* TLS required */
+/* Request flags, sent from client to server during transmission phase */
+#define NBD_CMD_FLAG_FUA (1 << 0)
-#define NBD_CMD_MASK_COMMAND 0x0000ffff
-#define NBD_CMD_FLAG_FUA (1 << 16)
-
+/* Supported request types */
enum {
NBD_CMD_READ = 0,
NBD_CMD_WRITE = 1,
diff --git a/nbd/client.c b/nbd/client.c
index f6db836..4620e8d 100644
--- a/nbd/client.c
+++ b/nbd/client.c
@@ -1,4 +1,5 @@
/*
+ * Copyright (C) 2016 Red Hat, Inc.
* Copyright (C) 2005 Anthony Liguori <anthony@codemonkey.ws>
*
* Network Block Device Client Side
@@ -714,11 +715,13 @@
TRACE("Sending request to server: "
"{ .from = %" PRIu64", .len = %" PRIu32 ", .handle = %" PRIu64
- ", .type=%" PRIu32 " }",
- request->from, request->len, request->handle, request->type);
+ ", .flags = %" PRIx16 ", .type = %" PRIu16 " }",
+ request->from, request->len, request->handle,
+ request->flags, request->type);
stl_be_p(buf, NBD_REQUEST_MAGIC);
- stl_be_p(buf + 4, request->type);
+ stw_be_p(buf + 4, request->flags);
+ stw_be_p(buf + 6, request->type);
stq_be_p(buf + 8, request->handle);
stq_be_p(buf + 16, request->from);
stl_be_p(buf + 24, request->len);
diff --git a/nbd/nbd-internal.h b/nbd/nbd-internal.h
index 7e78064..99e5157 100644
--- a/nbd/nbd-internal.h
+++ b/nbd/nbd-internal.h
@@ -53,10 +53,10 @@
/* This is all part of the "official" NBD API.
*
* The most up-to-date documentation is available at:
- * https://github.com/yoe/nbd/blob/master/doc/proto.txt
+ * https://github.com/yoe/nbd/blob/master/doc/proto.md
*/
-#define NBD_REQUEST_SIZE (4 + 4 + 8 + 8 + 4)
+#define NBD_REQUEST_SIZE (4 + 2 + 2 + 8 + 8 + 4)
#define NBD_REPLY_SIZE (4 + 4 + 8)
#define NBD_REQUEST_MAGIC 0x25609513
#define NBD_REPLY_MAGIC 0x67446698
diff --git a/nbd/server.c b/nbd/server.c
index ac42391..38a0fef 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -1,4 +1,5 @@
/*
+ * Copyright (C) 2016 Red Hat, Inc.
* Copyright (C) 2005 Anthony Liguori <anthony@codemonkey.ws>
*
* Network Block Device Server Side
@@ -652,21 +653,23 @@
/* Request
[ 0 .. 3] magic (NBD_REQUEST_MAGIC)
- [ 4 .. 7] type (0 == READ, 1 == WRITE)
+ [ 4 .. 5] flags (NBD_CMD_FLAG_FUA, ...)
+ [ 6 .. 7] type (NBD_CMD_READ, ...)
[ 8 .. 15] handle
[16 .. 23] from
[24 .. 27] len
*/
magic = ldl_be_p(buf);
- request->type = ldl_be_p(buf + 4);
+ request->flags = lduw_be_p(buf + 4);
+ request->type = lduw_be_p(buf + 6);
request->handle = ldq_be_p(buf + 8);
request->from = ldq_be_p(buf + 16);
request->len = ldl_be_p(buf + 24);
- TRACE("Got request: { magic = 0x%" PRIx32 ", .type = %" PRIx32
- ", from = %" PRIu64 " , len = %" PRIu32 " }",
- magic, request->type, request->from, request->len);
+ TRACE("Got request: { magic = 0x%" PRIx32 ", .flags = %" PRIx16
+ ", .type = %" PRIx16 ", from = %" PRIu64 ", len = %" PRIu32 " }",
+ magic, request->flags, request->type, request->from, request->len);
if (magic != NBD_REQUEST_MAGIC) {
LOG("invalid magic (got 0x%" PRIx32 ")", magic);
@@ -1013,7 +1016,6 @@
struct nbd_request *request)
{
NBDClient *client = req->client;
- uint32_t command;
ssize_t rc;
g_assert(qemu_in_coroutine());
@@ -1030,13 +1032,12 @@
TRACE("Decoding type");
- command = request->type & NBD_CMD_MASK_COMMAND;
- if (command != NBD_CMD_WRITE) {
+ if (request->type != NBD_CMD_WRITE) {
/* No payload, we are ready to read the next request. */
req->complete = true;
}
- if (command == NBD_CMD_DISC) {
+ if (request->type == NBD_CMD_DISC) {
/* Special case: we're going to disconnect without a reply,
* whether or not flags, from, or len are bogus */
TRACE("Request type is DISCONNECT");
@@ -1053,7 +1054,7 @@
goto out;
}
- if (command == NBD_CMD_READ || command == NBD_CMD_WRITE) {
+ if (request->type == NBD_CMD_READ || request->type == NBD_CMD_WRITE) {
if (request->len > NBD_MAX_BUFFER_SIZE) {
LOG("len (%" PRIu32" ) is larger than max len (%u)",
request->len, NBD_MAX_BUFFER_SIZE);
@@ -1067,7 +1068,7 @@
goto out;
}
}
- if (command == NBD_CMD_WRITE) {
+ if (request->type == NBD_CMD_WRITE) {
TRACE("Reading %" PRIu32 " byte(s)", request->len);
if (read_sync(client->ioc, req->data, request->len) != request->len) {
@@ -1083,12 +1084,11 @@
LOG("operation past EOF; From: %" PRIu64 ", Len: %" PRIu32
", Size: %" PRIu64, request->from, request->len,
(uint64_t)client->exp->size);
- rc = command == NBD_CMD_WRITE ? -ENOSPC : -EINVAL;
+ rc = request->type == NBD_CMD_WRITE ? -ENOSPC : -EINVAL;
goto out;
}
- if (request->type & ~NBD_CMD_MASK_COMMAND & ~NBD_CMD_FLAG_FUA) {
- LOG("unsupported flags (got 0x%x)",
- request->type & ~NBD_CMD_MASK_COMMAND);
+ if (request->flags & ~NBD_CMD_FLAG_FUA) {
+ LOG("unsupported flags (got 0x%x)", request->flags);
rc = -EINVAL;
goto out;
}
@@ -1110,7 +1110,6 @@
struct nbd_request request;
struct nbd_reply reply;
ssize_t ret;
- uint32_t command;
int flags;
TRACE("Reading request.");
@@ -1134,7 +1133,6 @@
reply.error = -ret;
goto error_reply;
}
- command = request.type & NBD_CMD_MASK_COMMAND;
if (client->closing) {
/*
@@ -1144,11 +1142,12 @@
goto done;
}
- switch (command) {
+ switch (request.type) {
case NBD_CMD_READ:
TRACE("Request type is READ");
- if (request.type & NBD_CMD_FLAG_FUA) {
+ /* XXX: NBD Protocol only documents use of FUA with WRITE */
+ if (request.flags & NBD_CMD_FLAG_FUA) {
ret = blk_co_flush(exp->blk);
if (ret < 0) {
LOG("flush failed");
@@ -1181,7 +1180,7 @@
TRACE("Writing to device");
flags = 0;
- if (request.type & NBD_CMD_FLAG_FUA) {
+ if (request.flags & NBD_CMD_FLAG_FUA) {
flags |= BDRV_REQ_FUA;
}
ret = blk_pwrite(exp->blk, request.from + exp->dev_offset,
