Re: [Libguestfs] [PATCH v3 06/14] nbd/server: Refactor handling of request payload

Upcoming additions to support NBD 64-bit effect lengths allow for the possibility to distinguish between payload length (capped at 32M) and effect length (up to 63 bits). Without that extension, only the NBD_CMD_WRITE request has a payload; but with the extension, it makes sense to allow at least NBD_CMD_BLOCK_STATUS to have both a payload and effect length (where the payload is a limited-size struct that in turns gives the real effect length as well as a subset of known ids for which status is requested). Other future NBD commands may also have a request payload, so the 64-bit extension introduces a new NBD_CMD_FLAG_PAYLOAD_LEN that distinguishes between whether the header length is a payload length or an effect length, rather than hard-coding the decision based on the command. Note that we do not support the payload version of BLOCK_STATUS yet. For this patch, no semantic change is intended for a compliant client. For a non-compliant client, it is possible that the error behavior changes (a different message, a change on whether the connection is killed or remains alive for the next command, or so forth), but all errors should still be handled gracefully. Signed-off-by: Eric Blake <eblake(a)redhat.com&gt; --- nbd/server.c | 55 +++++++++++++++++++++++++++++++++--------------- nbd/trace-events | 1 + 2 files changed, 39 insertions(+), 17 deletions(-) diff --git a/nbd/server.c b/nbd/server.c index cf38a104d9a..5812a773ace 100644 --- a/nbd/server.c +++ b/nbd/server.c @@ -2316,6 +2316,8 @@ static int coroutine_fn nbd_co_receive_request(NBDRequestData *req, NBDRequest * Error **errp) { NBDClient *client = req->client; + bool extended_with_payload; + int payload_len = 0; int valid_flags; int ret; @@ -2329,27 +2331,41 @@ static int coroutine_fn nbd_co_receive_request(NBDRequestData *req, NBDRequest * trace_nbd_co_receive_request_decode_type(request->handle, request->type, nbd_cmd_lookup(request->type)); - if (request->type != NBD_CMD_WRITE) { - /* No payload, we are ready to read the next request. */ - req->complete = true; - } - 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 */ + req->complete = true; return -EIO; } + /* Payload and buffer handling. */ + extended_with_payload = client->header_style >= NBD_HEADER_EXTENDED && + (request->flags & NBD_CMD_FLAG_PAYLOAD_LEN); if (request->type == NBD_CMD_READ || request->type == NBD_CMD_WRITE || - request->type == NBD_CMD_CACHE) - { + request->type == NBD_CMD_CACHE || extended_with_payload) { if (request->len > NBD_MAX_BUFFER_SIZE) { error_setg(errp, "len (%" PRIu64" ) is larger than max len (%u)", request->len, NBD_MAX_BUFFER_SIZE);

return -EINVAL; }

- if (request->type != NBD_CMD_CACHE) { + if (request->type == NBD_CMD_WRITE || extended_with_payload) { + payload_len = request->len; + if (request->type != NBD_CMD_WRITE) { + /* + * For now, we don't support payloads on other + * commands; but we can keep the connection alive. + */ + request->len = 0; + } else if (client->header_style >= NBD_HEADER_EXTENDED && + !extended_with_payload) { + /* The client is noncompliant. Trace it, but proceed. */ + trace_nbd_co_receive_ext_payload_compliance(request->from, + request->len); + } + } + + if (request->type == NBD_CMD_WRITE || request->type == NBD_CMD_READ) { req->data = blk_try_blockalign(client->exp->common.blk, request->len); if (req->data == NULL) { @@ -2359,18 +2375,20 @@ static int coroutine_fn nbd_co_receive_request(NBDRequestData *req, NBDRequest * } } - if (request->type == NBD_CMD_WRITE) { - assert(request->len <= NBD_MAX_BUFFER_SIZE); - if (nbd_read(client->ioc, req->data, request->len, "CMD_WRITE data", - errp) < 0) - { + if (payload_len) { + if (req->data) { + ret = nbd_read(client->ioc, req->data, payload_len, + "CMD_WRITE data", errp); + } else { + ret = nbd_drop(client->ioc, payload_len, errp); + } + if (ret < 0) { return -EIO; } - req->complete = true; - trace_nbd_co_receive_request_payload_received(request->handle, - request->len); + payload_len); } + req->complete = true; /* Sanity checks. */ if (client->exp->nbdflags & NBD_FLAG_READ_ONLY && @@ -2400,7 +2418,10 @@ static int coroutine_fn nbd_co_receive_request(NBDRequestData *req, NBDRequest * client->check_align); } valid_flags = NBD_CMD_FLAG_FUA; - if (request->type == NBD_CMD_READ && + if (request->type == NBD_CMD_WRITE && + client->header_style >= NBD_HEADER_EXTENDED) { + valid_flags |= NBD_CMD_FLAG_PAYLOAD_LEN; + } else if (request->type == NBD_CMD_READ && client->header_style >= NBD_HEADER_STRUCTURED) { valid_flags |= NBD_CMD_FLAG_DF; } else if (request->type == NBD_CMD_WRITE_ZEROES) { diff --git a/nbd/trace-events b/nbd/trace-events index e2c1d68688d..adf5666e207 100644 --- a/nbd/trace-events +++ b/nbd/trace-events @@ -71,6 +71,7 @@ nbd_co_send_extents(uint64_t handle, unsigned int extents, uint32_t id, uint64_t 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)" nbd_co_receive_request_payload_received(uint64_t handle, uint64_t len) "Payload received: handle = %" PRIu64 ", len = %" PRIu64 +nbd_co_receive_ext_payload_compliance(uint64_t from, uint64_t len) "client sent non-compliant write without payload flag: from=0x%" PRIx64 ", len=0x%" PRIx64 nbd_co_receive_align_compliance(const char *op, uint64_t from, uint64_t len, uint32_t align) "client sent non-compliant unaligned %s request: from=0x%" PRIx64 ", len=0x%" PRIx64 ", align=0x%" PRIx32 nbd_trip(void) "Reading request"