Received: from eggs.gnu.org ([2001:4830:134:3::10]:37722) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eBuAB-0007e5-IE for qemu-devel@nongnu.org; Mon, 06 Nov 2017 22:02:56 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eBuAA-0003Wo-A8 for qemu-devel@nongnu.org; Mon, 06 Nov 2017 22:02:55 -0500 From: Eric Blake Date: Mon, 6 Nov 2017 21:02:36 -0600 Message-Id: <20171107030236.23633-9-eblake@redhat.com> In-Reply-To: <20171107030236.23633-1-eblake@redhat.com> References: <20171107030236.23633-1-eblake@redhat.com> Subject: [Qemu-devel] [PATCH 8/8] nbd/server: Fix structured read of length 0 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: qemu-block@nongnu.org, pbonzini@redhat.com, vsementsov@virtuozzo.com The NBD spec is being clarified that a read of length 0 should not be attempted by a compliant client; but that a server must handle it correctly. However, it also implies that NBD_REPLY_TYPE_OFFSET_DATA must have a non-zero payload length, which means that we must either give an error or use a no-op REPLY_TYPE_NONE in response to a zero-length read, so that we don't trip up any clients that might kill the connection if we send a data chunk without data. Signed-off-by: Eric Blake --- nbd/server.c | 21 ++++++++++++++++++++- nbd/trace-events | 1 + 2 files changed, 21 insertions(+), 1 deletion(-) 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, diff --git a/nbd/trace-events b/nbd/trace-events index bbc75f6414..92568edce5 100644 --- a/nbd/trace-events +++ b/nbd/trace-events @@ -55,6 +55,7 @@ nbd_receive_request(uint32_t magic, uint16_t flags, uint16_t type, uint64_t from nbd_blk_aio_attached(const char *name, void *ctx) "Export %s: Attaching clients to AIO context %p\n" nbd_blk_aio_detach(const char *name, void *ctx) "Export %s: Detaching clients from AIO context %p\n" nbd_co_send_simple_reply(uint64_t handle, uint32_t error, const char *errname, int len) "Send simple reply: handle = %" PRIu64 ", error = %" PRIu32 " (%s), len = %d" +nbd_co_send_structured_done(uint64_t handle) "Send structured reply done: handle = %" PRIu64 nbd_co_send_structured_read(uint64_t handle, uint64_t offset, void *data, size_t size) "Send structured read data reply: handle = %" PRIu64 ", offset = %" PRIu64 ", data = %p, len = %zu" nbd_co_send_structured_error(uint64_t handle, int err, const char *errname, const char *msg) "Send structured error reply: handle = %" PRIu64 ", error = %d (%s), msg = '%s'" nbd_co_receive_request_decode_type(uint64_t handle, uint16_t type, const char *name) "Decoding type: handle = %" PRIu64 ", type = %" PRIu16 " (%s)" -- 2.13.6