Since we know that the maximum name we are willing to accept is small enough to stack-allocate, rework the iteration over NBD_OPT_LIST responses to reuse a stack buffer rather than allocating every time. Furthermore, we don't even have to allocate if we know the server's length doesn't match what we are searching for.
Signed-off-by: Eric Blake <ebl...@redhat.com> Reviewed-by: Alex Bligh <a...@alex.org.uk> --- v3: tweak commit message --- nbd/client.c | 130 +++++++++++++++++++++++++++++------------------------------ 1 file changed, 65 insertions(+), 65 deletions(-) diff --git a/nbd/client.c b/nbd/client.c index d346c86..4debb5d 100644 --- a/nbd/client.c +++ b/nbd/client.c @@ -230,14 +230,17 @@ static int nbd_handle_reply_err(QIOChannel *ioc, nbd_opt_reply *reply, return result; } -static int nbd_receive_list(QIOChannel *ioc, char **name, Error **errp) +/* Return -1 if unrecoverable error occurs, 0 if NBD_OPT_LIST is + * unsupported, 1 if iteration is done, 2 to keep looking, and 3 if + * this entry matches want. */ +static int nbd_receive_list(QIOChannel *ioc, const char *want, Error **errp) { nbd_opt_reply reply; uint32_t len; uint32_t namelen; + char name[NBD_MAX_NAME_SIZE + 1]; int error; - *name = NULL; if (nbd_receive_option_reply(ioc, NBD_OPT_LIST, &reply, errp) < 0) { return -1; } @@ -252,97 +255,94 @@ static int nbd_receive_list(QIOChannel *ioc, char **name, Error **errp) error_setg(errp, "length too long for option end"); return -1; } - } else if (reply.type == NBD_REP_SERVER) { - if (len < sizeof(namelen) || len > NBD_MAX_BUFFER_SIZE) { - error_setg(errp, "incorrect option length %"PRIu32, len); - return -1; - } - if (read_sync(ioc, &namelen, sizeof(namelen)) != sizeof(namelen)) { - error_setg(errp, "failed to read option name length"); - return -1; - } - namelen = be32_to_cpu(namelen); - len -= sizeof(namelen); - if (len < namelen) { - error_setg(errp, "incorrect option name length"); - return -1; - } - if (namelen > NBD_MAX_NAME_SIZE) { - error_setg(errp, "export name length too long %" PRIu32, namelen); - return -1; - } - - *name = g_new0(char, namelen + 1); - if (read_sync(ioc, *name, namelen) != namelen) { - error_setg(errp, "failed to read export name"); - g_free(*name); - *name = NULL; - return -1; - } - (*name)[namelen] = '\0'; - len -= namelen; - if (drop_sync(ioc, len) != len) { - error_setg(errp, "failed to read export description"); - g_free(*name); - *name = NULL; - return -1; - } - } else { + return 1; + } else if (reply.type != NBD_REP_SERVER) { error_setg(errp, "Unexpected reply type %" PRIx32 " expected %x", reply.type, NBD_REP_SERVER); return -1; } - return 1; + + if (len < sizeof(namelen) || len > NBD_MAX_BUFFER_SIZE) { + error_setg(errp, "incorrect option length %"PRIu32, len); + return -1; + } + if (read_sync(ioc, &namelen, sizeof(namelen)) != sizeof(namelen)) { + error_setg(errp, "failed to read option name length"); + return -1; + } + namelen = be32_to_cpu(namelen); + len -= sizeof(namelen); + if (len < namelen) { + error_setg(errp, "incorrect option name length"); + return -1; + } + if (namelen != strlen(want)) { + if (drop_sync(ioc, len) != len) { + error_setg(errp, "failed to skip export name with wrong length"); + return -1; + } + return 2; + } + + assert(namelen < sizeof(name)); + if (read_sync(ioc, name, namelen) != namelen) { + error_setg(errp, "failed to read export name"); + return -1; + } + name[namelen] = '\0'; + len -= namelen; + if (drop_sync(ioc, len) != len) { + error_setg(errp, "failed to read export description"); + return -1; + } + return strcmp(name, want) == 0 ? 3 : 2; } +/* Return -1 on failure, 0 if wantname is an available export. */ static int nbd_receive_query_exports(QIOChannel *ioc, const char *wantname, Error **errp) { bool foundExport = false; - TRACE("Querying export list"); + TRACE("Querying export list for '%s'", wantname); if (nbd_send_option_request(ioc, NBD_OPT_LIST, 0, NULL, errp) < 0) { return -1; } TRACE("Reading available export names"); while (1) { - char *name = NULL; - int ret = nbd_receive_list(ioc, &name, errp); + int ret = nbd_receive_list(ioc, wantname, errp); - if (ret < 0) { - g_free(name); - name = NULL; + switch (ret) { + default: + /* Server gave unexpected reply */ + assert(ret < 0); return -1; - } - if (ret == 0) { + case 0: /* Server doesn't support export listing, so * we will just assume an export with our * wanted name exists */ - foundExport = true; - break; - } - if (name == NULL) { - TRACE("End of export name list"); + return 0; + case 1: + /* Done iterating. */ + if (!foundExport) { + error_setg(errp, "No export with name '%s' available", + wantname); + return -1; + } + return 0; + case 2: + /* Wasn't this one, keep going. */ break; - } - if (g_str_equal(name, wantname)) { + case 3: + /* Found a match, but must finish parsing reply. */ + TRACE("Found desired export name '%s'", wantname); foundExport = true; - TRACE("Found desired export name '%s'", name); - } else { - TRACE("Ignored export name '%s'", name); + break; } - g_free(name); - } - - if (!foundExport) { - error_setg(errp, "No export with name '%s' available", wantname); - return -1; } - - return 0; } static QIOChannel *nbd_receive_starttls(QIOChannel *ioc, -- 2.5.5