similar to: [nbdkit PATCH] connections: Don't use uninit memory on early client EOF

The code handling the NBD protocol was located in the same file as the code handling connections, for not really any reason except historical. This is quite a large code movement which splits out the protocol code into four new files: server/protocol-handshake.c initial handshake server/protocol-handshake-newstyle.c " " (newstyle)

These are a couple of patches in preparation for the Block Status implementation. While the patches (especially the second one) are very large they are really just elementary code motion. Rich.

None are supported at present, so this always returns an empty list. --- docs/nbdkit-protocol.pod | 4 ++ server/protocol.h | 2 + server/connections.c | 84 ++++++++++++++++++++++++++++++++++++++++ 3 files changed, 90 insertions(+) diff --git a/docs/nbdkit-protocol.pod b/docs/nbdkit-protocol.pod index 68438fa..4c65e00 100644 --- a/docs/nbdkit-protocol.pod +++

qemu is about to add 'qemu-nbd --list', which exercises NBD_OPT_LIST and NBD_OPT_INFO to give the user as much detail as possible about an export without actually connecting to it. For that to display more than the export name when nbdkit is the server, we need to implement NBD_OPT_INFO. Thankfully, the NBD spec intentionally made the command very similar to NBD_OPT_GO, to the point that

Up to nbdkit 1.22, we never advertised large export lists, so a client had no real reason to give more than 32 NBD_OPT_ commands before finally selecting an export or quitting, and we were justified in dropping indecisive chatty clients as being a waste of server resources. But now that we support .list_exports, it is reasonable for a client (such as 'qemu-nbd --list' or 'nbdinfo

Since commit 86fdb48c6a5362d66865493d9d2172166f99722e we have stored the connection object in thread-local storage. In this very large, but mostly mechanical change we stop passing the connection pointer around everywhere, and instead use the value stored in thread-local storage. This assumes a 1-1 mapping between the connection and the current thread which is true in *most* places.

v1 was here: https://www.redhat.com/archives/libguestfs/2020-February/msg00081.html v2 replaces struct connection *conn = GET_CONN; with GET_CONN; which sets conn implicitly and asserts that it is non-NULL. If we actually want to test if conn is non-NULL or behave differently, then you must use threadlocal_get_conn() instead, and some existing uses do that. Rich.

The third patch is a large but mechanical change which gets rid of passing around struct connection * entirely within the server, preferring instead to reference the connection through thread-local storage. I hope this is a gateway to simplifying other parts of the code. Rich.

On 9/10/19 6:20 AM, Richard W.M. Jones wrote: > This allows plugins (or filters) to read the export name which was > passed to the server from the client. > > UNFINISHED: > > - Needs tests > --- > TODO | 8 ++++++ > docs/nbdkit-plugin.pod | 39 ++++++++++++++++++++++++++++ > server/connections.c | 1 +

--- src/connections.c | 233 +++++++++++++++++++++++++++++++++++++--------- src/protocol.h | 27 ++++-- 2 files changed, 209 insertions(+), 51 deletions(-) diff --git a/src/connections.c b/src/connections.c index ba6e91d..4e9b191 100644 --- a/src/connections.c +++ b/src/connections.c @@ -75,7 +75,9 @@ struct connection { void **handles; size_t nr_handles; + uint32_t cflags;

We don't know how long a plugin's .get_size() will take, but we also documented that it shouldn't change per connection and therefore can be cached. It's not hard to see that we have to consult the size per connection (see commit b3a43ccd for a test that purposefully exposes different sizes to separate clients), nor to search the code to see we already cache it at the protocol

When we added support for .extents, we had nbdkit unconditionally support structured replies if the client requests them, and the plugin's .can_extents has no impact on what the server advertises. However, while the plugin API doesn't care whether the client requested SR, there is still a case to be made for allowing a filter to prevent SR, at least for testing purposese (such as

This is only lightly tested (against just qemu NBD client), and the code might be structured a little better as the _negotiate_handshake_newstyle_options function has now grown to be huge. Anyway works for me. Rich.

There's no substantial difference over v1, I simply fixed a few whitespace issues, moved one struct around and tidied up the comments. Rich.

Experimental and only very lightly tested so far. Rich.

Since the v1 series (0/4, at [1]), I've applied patches 1 and 2, rewritten patch 3 [Forbid NUL in export and context names] into patch 4 here, patch 4 there turned into patch 6 here, and everything else here is new. [1]https://www.redhat.com/archives/libguestfs/2019-September/msg00180.html I don't know if there is a handy reusable function for checking whether a string contains valid

This is the sort of thing I had in mind for option (1) here: https://www.redhat.com/archives/libguestfs/2019-September/msg00047.html It does reveal that the way we currently list exports is naive to say the least ... Rich.

With some crufty sed scripts we can generate functions that map from NBD protocol flags (eg. NBD_CMD_READ) to strings ("NBD_CMD_READ"). This works on GNU sed and with FreeBSD, also with GNU sed's --posix option, so I guess the sed code is POSIX-compatible. Rich.

Fixes the fact that clients could not request the maximum string length except with NBD_OPT_EXPORT_LEN. Updates the testsuite to match. Signed-off-by: Eric Blake <eblake@redhat.com> --- server/protocol-handshake-newstyle.c | 12 +++++++----- tests/test-long-name.sh | 10 ++++------ 2 files changed, 11 insertions(+), 11 deletions(-) diff --git

This allows plugins (or filters) to read the export name which was passed to the server from the client. UNFINISHED: - Needs tests --- TODO | 8 ++++++ docs/nbdkit-plugin.pod | 39 ++++++++++++++++++++++++++++ server/connections.c | 1 + server/internal.h | 1 + server/protocol-handshake-newstyle.c | 30