From c8720ca03e01cf68f23a2017586db57abe12de0f Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Mon, 25 Sep 2023 14:22:32 -0500 Subject: [PATCH] nbd/server: Prepare to receive extended header requests Although extended mode is not yet enabled, once we do turn it on, we need to accept extended requests for all messages. Previous patches have already taken care of supporting 64-bit lengths, now we just need to read it off the wire. Note that this implementation will block indefinitely on a buggy client that sends a non-extended payload (that is, we try to read a full packet before we ever check the magic number, but a client that mistakenly sends a simple request after negotiating extended headers doesn't send us enough bytes), but it's no different from any other client that stops talking to us partway through a packet and thus not worth coding around. Signed-off-by: Eric Blake Reviewed-by: Vladimir Sementsov-Ogievskiy Message-ID: <20230925192229.3186470-16-eblake@redhat.com> --- nbd/nbd-internal.h | 5 ++++- nbd/server.c | 43 ++++++++++++++++++++++++++++++------------- 2 files changed, 34 insertions(+), 14 deletions(-) diff --git a/nbd/nbd-internal.h b/nbd/nbd-internal.h index 133b1d94b5..dfa02f77ee 100644 --- a/nbd/nbd-internal.h +++ b/nbd/nbd-internal.h @@ -34,8 +34,11 @@ * https://github.com/yoe/nbd/blob/master/doc/proto.md */ -/* Size of all NBD_OPT_*, without payload */ +/* Size of all compact NBD_CMD_*, without payload */ #define NBD_REQUEST_SIZE (4 + 2 + 2 + 8 + 8 + 4) +/* Size of all extended NBD_CMD_*, without payload */ +#define NBD_EXTENDED_REQUEST_SIZE (4 + 2 + 2 + 8 + 8 + 8) + /* Size of all NBD_REP_* sent in answer to most NBD_OPT_*, without payload */ #define NBD_REPLY_SIZE (4 + 4 + 8) /* Size of reply to NBD_OPT_EXPORT_NAME */ diff --git a/nbd/server.c b/nbd/server.c index 56e9b41828..501749d62b 100644 --- a/nbd/server.c +++ b/nbd/server.c @@ -1411,11 +1411,13 @@ nbd_read_eof(NBDClient *client, void *buffer, size_t size, Error **errp) static int coroutine_fn nbd_receive_request(NBDClient *client, NBDRequest *request, Error **errp) { - uint8_t buf[NBD_REQUEST_SIZE]; - uint32_t magic; + uint8_t buf[NBD_EXTENDED_REQUEST_SIZE]; + uint32_t magic, expect; int ret; + size_t size = client->mode >= NBD_MODE_EXTENDED ? + NBD_EXTENDED_REQUEST_SIZE : NBD_REQUEST_SIZE; - ret = nbd_read_eof(client, buf, sizeof(buf), errp); + ret = nbd_read_eof(client, buf, size, errp); if (ret < 0) { return ret; } @@ -1423,13 +1425,21 @@ static int coroutine_fn nbd_receive_request(NBDClient *client, NBDRequest *reque return -EIO; } - /* Request - [ 0 .. 3] magic (NBD_REQUEST_MAGIC) - [ 4 .. 5] flags (NBD_CMD_FLAG_FUA, ...) - [ 6 .. 7] type (NBD_CMD_READ, ...) - [ 8 .. 15] cookie - [16 .. 23] from - [24 .. 27] len + /* + * Compact request + * [ 0 .. 3] magic (NBD_REQUEST_MAGIC) + * [ 4 .. 5] flags (NBD_CMD_FLAG_FUA, ...) + * [ 6 .. 7] type (NBD_CMD_READ, ...) + * [ 8 .. 15] cookie + * [16 .. 23] from + * [24 .. 27] len + * Extended request + * [ 0 .. 3] magic (NBD_EXTENDED_REQUEST_MAGIC) + * [ 4 .. 5] flags (NBD_CMD_FLAG_FUA, NBD_CMD_FLAG_PAYLOAD_LEN, ...) + * [ 6 .. 7] type (NBD_CMD_READ, ...) + * [ 8 .. 15] cookie + * [16 .. 23] from + * [24 .. 31] len */ magic = ldl_be_p(buf); @@ -1437,13 +1447,20 @@ static int coroutine_fn nbd_receive_request(NBDClient *client, NBDRequest *reque request->type = lduw_be_p(buf + 6); request->cookie = ldq_be_p(buf + 8); request->from = ldq_be_p(buf + 16); - request->len = (uint32_t)ldl_be_p(buf + 24); /* widen 32 to 64 bits */ + if (client->mode >= NBD_MODE_EXTENDED) { + request->len = ldq_be_p(buf + 24); + expect = NBD_EXTENDED_REQUEST_MAGIC; + } else { + request->len = (uint32_t)ldl_be_p(buf + 24); /* widen 32 to 64 bits */ + expect = NBD_REQUEST_MAGIC; + } trace_nbd_receive_request(magic, request->flags, request->type, request->from, request->len); - if (magic != NBD_REQUEST_MAGIC) { - error_setg(errp, "invalid magic (got 0x%" PRIx32 ")", magic); + if (magic != expect) { + error_setg(errp, "invalid magic (got 0x%" PRIx32 ", expected 0x%" + PRIx32 ")", magic, expect); return -EINVAL; } return 0;