Re: [Libguestfs] [PATCH v3 09/14] nbd/server: Initial support for extended headers

Time to support clients that request extended headers. Now we can finally reach the code added across several previous patches. Even though the NBD spec has been altered to allow us to accept NBD_CMD_READ larger than the max payload size (provided our response is a hole or broken up over more than one data chunk), we are not planning to take advantage of that, and continue to cap NBD_CMD_READ to 32M regardless of header size. For NBD_CMD_WRITE_ZEROES and NBD_CMD_TRIM, the block layer already supports 64-bit operations without any effort on our part. For NBD_CMD_BLOCK_STATUS, the client's length is a hint, and the previous patch took care of implementing the required NBD_REPLY_TYPE_BLOCK_STATUS_EXT. Signed-off-by: Eric Blake <eblake(a)redhat.com&gt; --- nbd/nbd-internal.h | 5 +-

static inline void set_be_simple_reply(NBDClient *client, struct iovec *iov, - uint64_t error, NBDRequest *request) + uint32_t error, NBDStructuredError *err, + NBDRequest *request) { - NBDSimpleReply *reply = iov->iov_base; + if (client->header_style >= NBD_HEADER_EXTENDED) { + NBDExtendedReplyChunk *chunk = iov->iov_base; - iov->iov_len = sizeof(*reply); - stl_be_p(&reply->magic, NBD_SIMPLE_REPLY_MAGIC); - stl_be_p(&reply->error, error); - stq_be_p(&reply->handle, request->handle); + iov->iov_len = sizeof(*chunk); + stl_be_p(&chunk->magic, NBD_EXTENDED_REPLY_MAGIC); + stw_be_p(&chunk->flags, NBD_REPLY_FLAG_DONE); + stq_be_p(&chunk->handle, request->handle); + stq_be_p(&chunk->offset, request->from); + if (error) { + assert(!iov[1].iov_base); + iov[1].iov_base = err; + iov[1].iov_len = sizeof(*err); + stw_be_p(&chunk->type, NBD_REPLY_TYPE_ERROR); + stq_be_p(&chunk->length, sizeof(*err)); + stl_be_p(&err->error, error); + stw_be_p(&err->message_length, 0); + } else { + stw_be_p(&chunk->type, NBD_REPLY_TYPE_NONE); + stq_be_p(&chunk->length, 0); + } + } else { + NBDSimpleReply *reply = iov->iov_base; + + iov->iov_len = sizeof(*reply); + stl_be_p(&reply->magic, NBD_SIMPLE_REPLY_MAGIC); + stl_be_p(&reply->error, error); + stq_be_p(&reply->handle, request->handle); + } } static int coroutine_fn nbd_co_send_simple_reply(NBDClient *client, @@ -1906,30 +1966,44 @@ static int coroutine_fn nbd_co_send_simple_reply(NBDClient *client,

{ NBDReply hdr; int nbd_err = system_errno_to_nbd_errno(error); + NBDStructuredError err; struct iovec iov[] = { {.iov_base = &hdr}, {.iov_base = data, .iov_len = len} }; + assert(!len || !nbd_err); trace_nbd_co_send_simple_reply(request->handle, nbd_err, nbd_err_lookup(nbd_err), len); - set_be_simple_reply(client, &iov[0], nbd_err, request); + set_be_simple_reply(client, &iov[0], nbd_err, &err, request); - return nbd_co_send_iov(client, iov, len ? 2 : 1, errp); + return nbd_co_send_iov(client, iov, iov[1].iov_len ? 2 : 1, errp); } static inline void set_be_chunk(NBDClient *client, struct iovec *iov, uint16_t flags, uint16_t type, NBDRequest *request, uint32_t length) { - NBDStructuredReplyChunk *chunk = iov->iov_base; + if (client->header_style >= NBD_HEADER_EXTENDED) { + NBDExtendedReplyChunk *chunk = iov->iov_base; - iov->iov_len = sizeof(*chunk); - stl_be_p(&chunk->magic, NBD_STRUCTURED_REPLY_MAGIC); - stw_be_p(&chunk->flags, flags); - stw_be_p(&chunk->type, type); - stq_be_p(&chunk->handle, request->handle); - stl_be_p(&chunk->length, length); + iov->iov_len = sizeof(*chunk); + stl_be_p(&chunk->magic, NBD_EXTENDED_REPLY_MAGIC); + stw_be_p(&chunk->flags, flags); + stw_be_p(&chunk->type, type); + stq_be_p(&chunk->handle, request->handle); + stq_be_p(&chunk->offset, request->from); + stq_be_p(&chunk->length, length); + } else { + NBDStructuredReplyChunk *chunk = iov->iov_base; + + iov->iov_len = sizeof(*chunk); + stl_be_p(&chunk->magic, NBD_STRUCTURED_REPLY_MAGIC); + stw_be_p(&chunk->flags, flags); + stw_be_p(&chunk->type, type); + stq_be_p(&chunk->handle, request->handle); + stl_be_p(&chunk->length, length); + } } static int coroutine_fn nbd_co_send_structured_done(NBDClient *client,