Re: [Qemu-devel] [PATCH v5 07/14] nbd: Share common option-sending code in client

[Fam Zheng <famz@redhat.com>]

On Mon, 07/18 22:07, Eric Blake wrote:
> Rather than open-coding each option request, it's easier to
> have common helper functions do the work.  That in turn requires
> having convenient packed types for handling option requests
> and replies.
> 
> Signed-off-by: Eric Blake <eblake@redhat.com>
> 
> ---
> v4: rebase
> v3: rebase, tweak a debug message
> ---
>  include/block/nbd.h |  25 +++++-
>  nbd/nbd-internal.h  |   2 +-
>  nbd/client.c        | 250 ++++++++++++++++++++++------------------------------
>  3 files changed, 126 insertions(+), 151 deletions(-)
> 
> diff --git a/include/block/nbd.h b/include/block/nbd.h
> index 6904eb4..7c5103f 100644
> --- a/include/block/nbd.h
> +++ b/include/block/nbd.h
> @@ -26,15 +26,34 @@
>  #include "io/channel-socket.h"
>  #include "crypto/tlscreds.h"
> 
> -/* Note: these are _NOT_ the same as the network representation of an NBD
> +/* Handshake phase structs - this struct is passed on the wire */
> +
> +struct nbd_option {
> +    uint64_t magic; /* NBD_OPTS_MAGIC */
> +    uint32_t option; /* NBD_OPT_* */
> +    uint32_t length;
> +} QEMU_PACKED;
> +typedef struct nbd_option nbd_option;
> +
> +struct nbd_opt_reply {
> +    uint64_t magic; /* NBD_REP_MAGIC */
> +    uint32_t option; /* NBD_OPT_* */
> +    uint32_t type; /* NBD_REP_* */
> +    uint32_t length;
> +} QEMU_PACKED;
> +typedef struct nbd_opt_reply nbd_opt_reply;

Maybe someday in the future we should rename nbd type names to CamelCase?

> +
> +/* Transmission phase structs
> + *
> + * Note: these are _NOT_ the same as the network representation of an NBD
>   * request and reply!
>   */
>  struct nbd_request {
>      uint64_t handle;
>      uint64_t from;
>      uint32_t len;
> -    uint16_t flags;
> -    uint16_t type;
> +    uint16_t flags; /* NBD_CMD_FLAG_* */
> +    uint16_t type; /* NBD_CMD_* */
>  };
> 
>  struct nbd_reply {
> diff --git a/nbd/nbd-internal.h b/nbd/nbd-internal.h
> index 99e5157..dd57e18 100644
> --- a/nbd/nbd-internal.h
> +++ b/nbd/nbd-internal.h
> @@ -62,7 +62,7 @@
>  #define NBD_REPLY_MAGIC         0x67446698
>  #define NBD_OPTS_MAGIC          0x49484156454F5054LL
>  #define NBD_CLIENT_MAGIC        0x0000420281861253LL
> -#define NBD_REP_MAGIC           0x3e889045565a9LL
> +#define NBD_REP_MAGIC           0x0003e889045565a9LL
> 
>  #define NBD_SET_SOCK            _IO(0xab, 0)
>  #define NBD_SET_BLKSIZE         _IO(0xab, 1)
> diff --git a/nbd/client.c b/nbd/client.c
> index 7c172ed..6e5288a 100644
> --- a/nbd/client.c
> +++ b/nbd/client.c
> @@ -75,64 +75,123 @@ static QTAILQ_HEAD(, NBDExport) exports = QTAILQ_HEAD_INITIALIZER(exports);
> 
>  */
> 
> +/* Send an option request. Return 0 if successful, -1 with errp set if
> + * it is impossible to continue. */
> +static int nbd_send_option_request(QIOChannel *ioc, uint32_t opt,
> +                                   uint32_t len, const char *data,
> +                                   Error **errp)
> +{
> +    nbd_option req;
> +    QEMU_BUILD_BUG_ON(sizeof(req) != 16);
> 
> -/* If type represents success, return 1 without further action.
> - * If type represents an error reply, consume the rest of the packet on ioc.
> - * Then return 0 for unsupported (so the client can fall back to
> - * other approaches), or -1 with errp set for other errors.
> +    if (len == -1) {

This looks like magic, move the strlen() call to caller, or add a comment?

> +        req.length = len = strlen(data);
> +    }
> +    TRACE("Sending option request %"PRIu32", len %"PRIu32, opt, len);

s/%"PRI/%" PRI/g ?

> +
> +    stq_be_p(&req.magic, NBD_OPTS_MAGIC);
> +    stl_be_p(&req.option, opt);
> +    stl_be_p(&req.length, len);
> +
> +    if (write_sync(ioc, &req, sizeof(req)) != sizeof(req)) {
> +        error_setg(errp, "Failed to send option request header");
> +        return -1;
> +    }
> +
> +    if (len && write_sync(ioc, (char *) data, len) != len) {
> +        error_setg(errp, "Failed to send option request data");
> +        return -1;
> +    }
> +
> +    return 0;
> +}
> +
> +/* Receive the header of an option reply, which should match the given
> + * opt.  Read through the length field, but NOT the length bytes of
> + * payload. Return 0 if successful, -1 with errp set if it is
> + * impossible to continue. */
> +static int nbd_receive_option_reply(QIOChannel *ioc, uint32_t opt,
> +                                    nbd_opt_reply *reply, Error **errp)
> +{
> +    QEMU_BUILD_BUG_ON(sizeof(*reply) != 20);
> +    if (read_sync(ioc, reply, sizeof(*reply)) != sizeof(*reply)) {
> +        error_setg(errp, "failed to read option reply");
> +        return -1;
> +    }
> +    be64_to_cpus(&reply->magic);
> +    be32_to_cpus(&reply->option);
> +    be32_to_cpus(&reply->type);
> +    be32_to_cpus(&reply->length);
> +
> +    TRACE("Received option reply %"PRIx32", type %"PRIx32", len %"PRIu32,
> +          reply->option, reply->type, reply->length);
> +
> +    if (reply->magic != NBD_REP_MAGIC) {
> +        error_setg(errp, "Unexpected option reply magic");
> +        return -1;
> +    }
> +    if (reply->option != opt) {
> +        error_setg(errp, "Unexpected option type %x expected %x",
> +                   reply->option, opt);
> +        return -1;
> +    }
> +    return 0;
> +}
> +
> +/* If reply represents success, return 1 without further action.
> + * If reply represents an error, consume the optional payload of
> + * the packet on ioc.  Then return 0 for unsupported (so the client
> + * can fall back to other approaches), or -1 with errp set for other
> + * errors.
>   */
> -static int nbd_handle_reply_err(QIOChannel *ioc, uint32_t opt, uint32_t type,
> +static int nbd_handle_reply_err(QIOChannel *ioc, nbd_opt_reply *reply,
>                                  Error **errp)
>  {
> -    uint32_t len;
>      char *msg = NULL;
>      int result = -1;
> 
> -    if (!(type & (1 << 31))) {
> +    if (!(reply->type & (1 << 31))) {
>          return 1;
>      }
> 
> -    if (read_sync(ioc, &len, sizeof(len)) != sizeof(len)) {
> -        error_setg(errp, "failed to read option length");
> -        return -1;
> -    }
> -    len = be32_to_cpu(len);
> -    if (len) {
> -        if (len > NBD_MAX_BUFFER_SIZE) {
> +    if (reply->length) {
> +        if (reply->length > NBD_MAX_BUFFER_SIZE) {
>              error_setg(errp, "server's error message is too long");
>              goto cleanup;
>          }
> -        msg = g_malloc(len + 1);
> -        if (read_sync(ioc, msg, len) != len) {
> +        msg = g_malloc(reply->length + 1);
> +        if (read_sync(ioc, msg, reply->length) != reply->length) {
>              error_setg(errp, "failed to read option error message");
>              goto cleanup;
>          }
> -        msg[len] = '\0';
> +        msg[reply->length] = '\0';
>      }
> 
> -    switch (type) {
> +    switch (reply->type) {
>      case NBD_REP_ERR_UNSUP:
>          TRACE("server doesn't understand request %" PRIx32
> -              ", attempting fallback", opt);
> +              ", attempting fallback", reply->option);
>          result = 0;
>          goto cleanup;
> 
>      case NBD_REP_ERR_POLICY:
> -        error_setg(errp, "Denied by server for option %" PRIx32, opt);
> +        error_setg(errp, "Denied by server for option %" PRIx32,
> +                   reply->option);
>          break;
> 
>      case NBD_REP_ERR_INVALID:
> -        error_setg(errp, "Invalid data length for option %" PRIx32, opt);
> +        error_setg(errp, "Invalid data length for option %" PRIx32,
> +                   reply->option);
>          break;
> 
>      case NBD_REP_ERR_TLS_REQD:
>          error_setg(errp, "TLS negotiation required before option %" PRIx32,
> -                   opt);
> +                   reply->option);
>          break;
> 
>      default:
>          error_setg(errp, "Unknown error code when asking for option %" PRIx32,
> -                   opt);
> +                   reply->option);
>          break;
>      }
> 
> @@ -147,58 +206,29 @@ static int nbd_handle_reply_err(QIOChannel *ioc, uint32_t opt, uint32_t type,
> 
>  static int nbd_receive_list(QIOChannel *ioc, char **name, Error **errp)
>  {
> -    uint64_t magic;
> -    uint32_t opt;
> -    uint32_t type;
> +    nbd_opt_reply reply;
>      uint32_t len;
>      uint32_t namelen;
>      int error;
> 
>      *name = NULL;
> -    if (read_sync(ioc, &magic, sizeof(magic)) != sizeof(magic)) {
> -        error_setg(errp, "failed to read list option magic");
> +    if (nbd_receive_option_reply(ioc, NBD_OPT_LIST, &reply, errp) < 0) {
>          return -1;
>      }
> -    magic = be64_to_cpu(magic);
> -    if (magic != NBD_REP_MAGIC) {
> -        error_setg(errp, "Unexpected option list magic");
> -        return -1;
> -    }
> -    if (read_sync(ioc, &opt, sizeof(opt)) != sizeof(opt)) {
> -        error_setg(errp, "failed to read list option");
> -        return -1;
> -    }
> -    opt = be32_to_cpu(opt);
> -    if (opt != NBD_OPT_LIST) {
> -        error_setg(errp, "Unexpected option type %" PRIx32 " expected %x",
> -                   opt, NBD_OPT_LIST);
> -        return -1;
> -    }
> -
> -    if (read_sync(ioc, &type, sizeof(type)) != sizeof(type)) {
> -        error_setg(errp, "failed to read list option type");
> -        return -1;
> -    }
> -    type = be32_to_cpu(type);
> -    error = nbd_handle_reply_err(ioc, opt, type, errp);
> +    error = nbd_handle_reply_err(ioc, &reply, errp);
>      if (error <= 0) {
>          return error;
>      }
> +    len = reply.length;
> 
> -    if (read_sync(ioc, &len, sizeof(len)) != sizeof(len)) {
> -        error_setg(errp, "failed to read option length");
> -        return -1;
> -    }
> -    len = be32_to_cpu(len);
> -
> -    if (type == NBD_REP_ACK) {
> +    if (reply.type == NBD_REP_ACK) {
>          if (len != 0) {
>              error_setg(errp, "length too long for option end");
>              return -1;
>          }
> -    } else if (type == NBD_REP_SERVER) {
> +    } else if (reply.type == NBD_REP_SERVER) {
>          if (len < sizeof(namelen) || len > NBD_MAX_BUFFER_SIZE) {
> -            error_setg(errp, "incorrect option length");
> +            error_setg(errp, "incorrect option length %"PRIu32, len);

s/%"/%" /

>              return -1;
>          }
>          if (read_sync(ioc, &namelen, sizeof(namelen)) != sizeof(namelen)) {
> @@ -240,7 +270,7 @@ static int nbd_receive_list(QIOChannel *ioc, char **name, Error **errp)
>          }
>      } else {
>          error_setg(errp, "Unexpected reply type %" PRIx32 " expected %x",
> -                   type, NBD_REP_SERVER);
> +                   reply.type, NBD_REP_SERVER);
>          return -1;
>      }
>      return 1;
> @@ -251,24 +281,10 @@ static int nbd_receive_query_exports(QIOChannel *ioc,
>                                       const char *wantname,
>                                       Error **errp)
>  {
> -    uint64_t magic = cpu_to_be64(NBD_OPTS_MAGIC);
> -    uint32_t opt = cpu_to_be32(NBD_OPT_LIST);
> -    uint32_t length = 0;
>      bool foundExport = false;
> 
>      TRACE("Querying export list");
> -    if (write_sync(ioc, &magic, sizeof(magic)) != sizeof(magic)) {
> -        error_setg(errp, "Failed to send list option magic");
> -        return -1;
> -    }
> -
> -    if (write_sync(ioc, &opt, sizeof(opt)) != sizeof(opt)) {
> -        error_setg(errp, "Failed to send list option number");
> -        return -1;
> -    }
> -
> -    if (write_sync(ioc, &length, sizeof(length)) != sizeof(length)) {
> -        error_setg(errp, "Failed to send list option length");
> +    if (nbd_send_option_request(ioc, NBD_OPT_LIST, 0, NULL, errp) < 0) {
>          return -1;
>      }
> 
> @@ -314,72 +330,29 @@ static QIOChannel *nbd_receive_starttls(QIOChannel *ioc,
>                                          QCryptoTLSCreds *tlscreds,
>                                          const char *hostname, Error **errp)
>  {
> -    uint64_t magic = cpu_to_be64(NBD_OPTS_MAGIC);
> -    uint32_t opt = cpu_to_be32(NBD_OPT_STARTTLS);
> -    uint32_t length = 0;
> -    uint32_t type;
> +    nbd_opt_reply reply;
>      QIOChannelTLS *tioc;
>      struct NBDTLSHandshakeData data = { 0 };
> 
>      TRACE("Requesting TLS from server");
> -    if (write_sync(ioc, &magic, sizeof(magic)) != sizeof(magic)) {
> -        error_setg(errp, "Failed to send option magic");
> -        return NULL;
> -    }
> -
> -    if (write_sync(ioc, &opt, sizeof(opt)) != sizeof(opt)) {
> -        error_setg(errp, "Failed to send option number");
> -        return NULL;
> -    }
> -
> -    if (write_sync(ioc, &length, sizeof(length)) != sizeof(length)) {
> -        error_setg(errp, "Failed to send option length");
> -        return NULL;
> -    }
> -
> -    TRACE("Getting TLS reply from server1");
> -    if (read_sync(ioc, &magic, sizeof(magic)) != sizeof(magic)) {
> -        error_setg(errp, "failed to read option magic");
> -        return NULL;
> -    }
> -    magic = be64_to_cpu(magic);
> -    if (magic != NBD_REP_MAGIC) {
> -        error_setg(errp, "Unexpected option magic");
> -        return NULL;
> -    }
> -    TRACE("Getting TLS reply from server2");
> -    if (read_sync(ioc, &opt, sizeof(opt)) != sizeof(opt)) {
> -        error_setg(errp, "failed to read option");
> -        return NULL;
> -    }
> -    opt = be32_to_cpu(opt);
> -    if (opt != NBD_OPT_STARTTLS) {
> -        error_setg(errp, "Unexpected option type %" PRIx32 " expected %x",
> -                   opt, NBD_OPT_STARTTLS);
> +    if (nbd_send_option_request(ioc, NBD_OPT_STARTTLS, 0, NULL, errp) < 0) {
>          return NULL;
>      }
> 
>      TRACE("Getting TLS reply from server");
> -    if (read_sync(ioc, &type, sizeof(type)) != sizeof(type)) {
> -        error_setg(errp, "failed to read option type");
> +    if (nbd_receive_option_reply(ioc, NBD_OPT_STARTTLS, &reply, errp) < 0) {
>          return NULL;
>      }
> -    type = be32_to_cpu(type);
> -    if (type != NBD_REP_ACK) {
> +
> +    if (reply.type != NBD_REP_ACK) {
>          error_setg(errp, "Server rejected request to start TLS %" PRIx32,
> -                   type);
> +                   reply.type);
>          return NULL;
>      }
> 
> -    TRACE("Getting TLS reply from server");
> -    if (read_sync(ioc, &length, sizeof(length)) != sizeof(length)) {
> -        error_setg(errp, "failed to read option length");
> -        return NULL;
> -    }
> -    length = be32_to_cpu(length);
> -    if (length != 0) {
> +    if (reply.length != 0) {
>          error_setg(errp, "Start TLS response was not zero %" PRIu32,
> -                   length);
> +                   reply.length);
>          return NULL;
>      }
> 
> @@ -466,8 +439,6 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char *name, uint16_t *flags,
> 
>      if (magic == NBD_OPTS_MAGIC) {
>          uint32_t clientflags = 0;
> -        uint32_t opt;
> -        uint32_t namesize;
>          uint16_t globalflags;
>          bool fixedNewStyle = false;
> 
> @@ -517,28 +488,13 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char *name, uint16_t *flags,
>                  goto fail;
>              }
>          }
> -        /* write the export name */
> -        magic = cpu_to_be64(magic);
> -        if (write_sync(ioc, &magic, sizeof(magic)) != sizeof(magic)) {
> -            error_setg(errp, "Failed to send export name magic");
> -            goto fail;
> -        }
> -        opt = cpu_to_be32(NBD_OPT_EXPORT_NAME);
> -        if (write_sync(ioc, &opt, sizeof(opt)) != sizeof(opt)) {
> -            error_setg(errp, "Failed to send export name option number");
> -            goto fail;
> -        }
> -        namesize = cpu_to_be32(strlen(name));
> -        if (write_sync(ioc, &namesize, sizeof(namesize)) !=
> -            sizeof(namesize)) {
> -            error_setg(errp, "Failed to send export name length");
> -            goto fail;
> -        }
> -        if (write_sync(ioc, (char *)name, strlen(name)) != strlen(name)) {
> -            error_setg(errp, "Failed to send export name");
> +        /* write the export name request */
> +        if (nbd_send_option_request(ioc, NBD_OPT_EXPORT_NAME, -1, name,
> +                                    errp) < 0) {
>              goto fail;
>          }
> 
> +        /* Read the response */
>          if (read_sync(ioc, &s, sizeof(s)) != sizeof(s)) {
>              error_setg(errp, "Failed to read export length");
>              goto fail;
> -- 
> 2.5.5
> 
> 

Fam