NBD commit 6d34500b clarified how clients and servers are supposed to behave before closing a connection. It added NBD_REP_ERR_SHUTDOWN (for the server to announce it is about to go away during option haggling, so the client should quit sending NBD_OPT_* other than NBD_OPT_ABORT) and ESHUTDOWN (for the server to announce it is about to go away during transmission, so the client should quit sending NBD_CMD_* other than NBD_CMD_DISC). It also clarified that NBD_OPT_ABORT gets a reply, while NBD_CMD_DISC does not.
This patch merely adds the missing reply to NBD_OPT_ABORT and teaches the client to recognize server errors. Actually teaching the server to send NBD_REP_ERR_SHUTDOWN or ESHUTDOWN would require knowing that the server has been requested to shut down soon (maybe we could do that by installing a SIGINT handler in qemu-nbd, which transitions from RUNNING to a new state that waits for the client to react, rather than just out-right quitting). Signed-off-by: Eric Blake <ebl...@redhat.com> --- include/block/nbd.h | 13 +++++++++---- nbd/nbd-internal.h | 1 + nbd/client.c | 16 ++++++++++++++++ nbd/server.c | 16 +++++++++++++++- 4 files changed, 41 insertions(+), 5 deletions(-) diff --git a/include/block/nbd.h b/include/block/nbd.h index d707761..2fd1a67 100644 --- a/include/block/nbd.h +++ b/include/block/nbd.h @@ -82,12 +82,17 @@ typedef struct nbd_reply nbd_reply; #define NBD_FLAG_C_NO_ZEROES (1 << 1) /* End handshake without zeroes. */ /* Reply types. */ +#define NBD_REP_ERR(value) ((UINT32_C(1) << 31) | (value)) + #define NBD_REP_ACK (1) /* Data sending finished. */ #define NBD_REP_SERVER (2) /* Export description. */ -#define NBD_REP_ERR_UNSUP ((UINT32_C(1) << 31) | 1) /* Unknown option. */ -#define NBD_REP_ERR_POLICY ((UINT32_C(1) << 31) | 2) /* Server denied */ -#define NBD_REP_ERR_INVALID ((UINT32_C(1) << 31) | 3) /* Invalid length. */ -#define NBD_REP_ERR_TLS_REQD ((UINT32_C(1) << 31) | 5) /* TLS required */ + +#define NBD_REP_ERR_UNSUP NBD_REP_ERR(1) /* Unknown option. */ +#define NBD_REP_ERR_POLICY NBD_REP_ERR(2) /* Server denied */ +#define NBD_REP_ERR_INVALID NBD_REP_ERR(3) /* Invalid length */ +#define NBD_REP_ERR_PLATFORM NBD_REP_ERR(4) /* Not compiled in */ +#define NBD_REP_ERR_TLS_REQD NBD_REP_ERR(5) /* TLS required */ +#define NBD_REP_ERR_SHUTDOWN NBD_REP_ERR(7) /* Server shutting down */ /* Request flags, sent from client to server during transmission phase */ #define NBD_CMD_FLAG_FUA (1 << 0) diff --git a/nbd/nbd-internal.h b/nbd/nbd-internal.h index 95069db..0d40b1f 100644 --- a/nbd/nbd-internal.h +++ b/nbd/nbd-internal.h @@ -91,6 +91,7 @@ #define NBD_ENOMEM 12 #define NBD_EINVAL 22 #define NBD_ENOSPC 28 +#define NBD_ESHUTDOWN 108 static inline ssize_t read_sync(QIOChannel *ioc, void *buffer, size_t size) { diff --git a/nbd/client.c b/nbd/client.c index 68e9473..4140d13 100644 --- a/nbd/client.c +++ b/nbd/client.c @@ -34,6 +34,8 @@ static int nbd_errno_to_system_errno(int err) return ENOMEM; case NBD_ENOSPC: return ENOSPC; + case NBD_ESHUTDOWN: + return ESHUTDOWN; default: TRACE("Squashing unexpected error %d to EINVAL", err); /* fallthrough */ @@ -210,11 +212,21 @@ static int nbd_handle_reply_err(QIOChannel *ioc, nbd_opt_reply *reply, reply->option); break; + case NBD_REP_ERR_PLATFORM: + error_setg(errp, "Server lacks support for option %" PRIx32, + reply->option); + break; + case NBD_REP_ERR_TLS_REQD: error_setg(errp, "TLS negotiation required before option %" PRIx32, reply->option); break; + case NBD_REP_ERR_SHUTDOWN: + error_setg(errp, "Server shutting down before option %" PRIx32, + reply->option); + break; + default: error_setg(errp, "Unknown error code when asking for option %" PRIx32, reply->option); @@ -754,6 +766,10 @@ ssize_t nbd_receive_reply(QIOChannel *ioc, struct nbd_reply *reply) LOG("invalid magic (got 0x%" PRIx32 ")", magic); return -EINVAL; } + if (reply->error == ESHUTDOWN) { + LOG("server shutting down"); + return -EINVAL; + } return 0; } diff --git a/nbd/server.c b/nbd/server.c index dadc928..fa6a994 100644 --- a/nbd/server.c +++ b/nbd/server.c @@ -39,6 +39,8 @@ static int system_errno_to_nbd_errno(int err) case EFBIG: case ENOSPC: return NBD_ENOSPC; + case ESHUTDOWN: + return NBD_ESHUTDOWN; case EINVAL: default: return NBD_EINVAL; @@ -484,6 +486,10 @@ static int nbd_negotiate_options(NBDClient *client) if (ret < 0) { return ret; } + /* Let the client keep trying, unless they asked to quit */ + if (clientflags == NBD_OPT_ABORT) { + return -EINVAL; + } break; } } else if (fixedNewstyle) { @@ -496,7 +502,15 @@ static int nbd_negotiate_options(NBDClient *client) break; case NBD_OPT_ABORT: - return -EINVAL; + /* NBD spec says we must reply before disconnecting, + * but that we must also tolerate guests that don't + * wait for our reply. */ + ret = nbd_negotiate_send_rep(client->ioc, NBD_REP_ACK, + clientflags); + if (!ret) { + ret = -EINVAL; + } + return ret; case NBD_OPT_EXPORT_NAME: return nbd_negotiate_handle_export_name(client, length); -- 2.5.5