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authorEric Blake <eblake@redhat.com>2017-11-08 15:57:03 -0600
committerEric Blake <eblake@redhat.com>2017-11-09 10:25:11 -0600
commitef8c887ee01a4e4c8c5c28c86ea5b45162c51bcd (patch)
treee6eaa1e3a1825c56e6da57211be6d4b61d59a8e3 /nbd/server.c
parentb4176cb314995ad225d6c2b531568801feb04f3f (diff)
nbd/server: Fix structured read of length 0
The NBD spec was recently clarified to state that a read of length 0 should not be attempted by a compliant client; but that a server must still handle it correctly in an unspecified manner (that is, either a successful no-op or an error reply, but not a crash) [1]. However, it also implies that NBD_REPLY_TYPE_OFFSET_DATA must have a non-zero payload length, but our existing code was replying with a chunk that a picky client could reject as invalid because it was missing a payload (our own client implementation was recently patched to be that picky, after first fixing it to not send 0-length requests). We are already doing successful no-ops for 0-length writes and for non-structured reads; so for consistency, we want structured reply reads to also be a no-op. The easiest way to do this is to return a NBD_REPLY_TYPE_NONE chunk; this is best done via a new helper function (especially since future patches for other structured replies may benefit from using the same helper). [1] https://github.com/NetworkBlockDevice/nbd/commit/ee926037 Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <20171108215703.9295-8-eblake@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Diffstat (limited to 'nbd/server.c')
-rw-r--r--nbd/server.c21
1 files changed, 20 insertions, 1 deletions
diff --git a/nbd/server.c b/nbd/server.c
index 6ebb7d9c2e..df771fd42f 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -1273,6 +1273,21 @@ static inline void set_be_chunk(NBDStructuredReplyChunk *chunk, uint16_t flags,
stl_be_p(&chunk->length, length);
}
+static int coroutine_fn nbd_co_send_structured_done(NBDClient *client,
+ uint64_t handle,
+ Error **errp)
+{
+ NBDStructuredReplyChunk chunk;
+ struct iovec iov[] = {
+ {.iov_base = &chunk, .iov_len = sizeof(chunk)},
+ };
+
+ trace_nbd_co_send_structured_done(handle);
+ set_be_chunk(&chunk, NBD_REPLY_FLAG_DONE, NBD_REPLY_TYPE_NONE, handle, 0);
+
+ return nbd_co_send_iov(client, iov, 1, errp);
+}
+
static int coroutine_fn nbd_co_send_structured_read(NBDClient *client,
uint64_t handle,
uint64_t offset,
@@ -1286,6 +1301,7 @@ static int coroutine_fn nbd_co_send_structured_read(NBDClient *client,
{.iov_base = data, .iov_len = size}
};
+ assert(size);
trace_nbd_co_send_structured_read(handle, offset, data, size);
set_be_chunk(&chunk.h, NBD_REPLY_FLAG_DONE, NBD_REPLY_TYPE_OFFSET_DATA,
handle, sizeof(chunk) - sizeof(chunk.h) + size);
@@ -1544,10 +1560,13 @@ reply:
if (ret < 0) {
ret = nbd_co_send_structured_error(req->client, request.handle,
-ret, msg, &local_err);
- } else {
+ } else if (reply_data_len) {
ret = nbd_co_send_structured_read(req->client, request.handle,
request.from, req->data,
reply_data_len, &local_err);
+ } else {
+ ret = nbd_co_send_structured_done(req->client, request.handle,
+ &local_err);
}
} else {
ret = nbd_co_send_simple_reply(req->client, request.handle,