cifs: try opening channels after mounting

After doing mount() successfully we call cifs_try_adding_channels()
which will open as many channels as it can.

Channels are closed when the master session is closed.

The master connection becomes the first channel.

,-------------> global cifs_tcp_ses_list <-------------------------.
|                                                                  |
'- TCP_Server_Info  <-->  TCP_Server_Info  <-->  TCP_Server_Info <-'
      (master con)           (chan#1 con)         (chan#2 con)
      |      ^                    ^                    ^
      v      '--------------------|--------------------'
   cifs_ses                       |
   - chan_count = 3               |
   - chans[] ---------------------'
   - smb3signingkey[]
      (master signing key)

Note how channel connections don't have sessions. That's because
cifs_ses can only be part of one linked list (list_head are internal
to the elements).

For signing keys, each channel has its own signing key which must be
used only after the channel has been bound. While it's binding it must
use the master session signing key.

For encryption keys, since channel connections do not have sessions
attached we must now find matching session by looping over all sessions
in smb2_get_enc_key().

Each channel is opened like a regular server connection but at the
session setup request step it must set the
SMB2_SESSION_REQ_FLAG_BINDING flag and use the session id to bind to.

Finally, while sending in compound_send_recv() for requests that
aren't negprot, ses-setup or binding related, use a channel by cycling
through the available ones (round-robin).

Signed-off-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 6bd917b4ee1d..5254a09fcc35 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -1001,6 +1001,8 @@ struct cifs_ses {
 	__u8 smb3decryptionkey[SMB3_SIGN_KEY_SIZE];
 	__u8 preauth_sha_hash[SMB2_PREAUTH_HASH_SIZE];
 
+	__u8 binding_preauth_sha_hash[SMB2_PREAUTH_HASH_SIZE];
+
 	/*
 	 * Network interfaces available on the server this session is
 	 * connected to.
@@ -1022,6 +1024,20 @@ struct cifs_ses {
 	atomic_t chan_seq; /* round robin state */
 };
 
+/*
+ * When binding a new channel, we need to access the channel which isn't fully
+ * established yet (one past the established count)
+ */
+
+static inline
+struct cifs_chan *cifs_ses_binding_channel(struct cifs_ses *ses)
+{
+	if (ses->binding)
+		return &ses->chans[ses->chan_count];
+	else
+		return NULL;
+}
+
 static inline
 struct TCP_Server_Info *cifs_ses_server(struct cifs_ses *ses)
 {