If a Delta Chat message has the Message-ID already existing in the db, but a greater "Date", it's a
resent message that can be deleted. Messages having the same "Date" mustn't be deleted because they
can be already seen messages moved back to INBOX. Also don't delete messages having lesser "Date" to
avoid deleting both messages in a multi-device setting.
As ratelimit was introduced to avoid reconnecting immediately after disconnecting
in case of bugs in IMAP protocol handling,
connection attempts should only be counted when IMAP is actually used,
i.e. when the first command (LOGIN) is sent.
Limit the number of IMAP connections to 1 per minute regardless of the reason of reconnection, but
allow one immediate retry. This is more reliable than ratelimiting only in error conditions because
ratelimiting can't be skipped by mistake. Anyway connections shouldn't be frequent in normal
operation mode.
Otherwise when connection is lost IMAP may get into infinite loop
trying to parse remaining bytes:
11-21 18:00:48.442 14858 12946 W DeltaChat: src/imap.rs:1457: Failed to process IMAP FETCH result: io: bytes remaining in stream.
11-21 18:00:48.442 14858 12946 W DeltaChat: src/imap.rs:1457: Failed to process IMAP FETCH result: io: bytes remaining in stream.
11-21 18:00:48.442 14858 12946 W DeltaChat: src/imap.rs:1457: Failed to process IMAP FETCH result: io: bytes remaining in stream.
11-21 18:00:48.442 14858 12946 W DeltaChat: src/imap.rs:1457: Failed to process IMAP FETCH result: io: bytes remaining in stream.
11-21 18:00:48.442 14858 12946 W DeltaChat: src/imap.rs:1457: Failed to process IMAP FETCH result: io: bytes remaining in stream.
11-21 18:00:48.442 14858 12946 W DeltaChat: src/imap.rs:1457: Failed to process IMAP FETCH result: io: bytes remaining in stream.
Returning an error bubbles it up to `fetch_idle()`
which will call `trigger_reconnect()` and drop the connection.
Ensure the client does not busy loop
skipping IDLE if UIDNEXT of the mailbox is higher than
the last seen UID plus 1, e.g. if the message
with UID=UIDNEXT-1 was deleted before we fetched it.
We do not fallback to UIDNEXT=1 anymore
if the STATUS command cannot determine UIDNEXT.
There are no known IMAP servers with broken STATUS so far.
This allows to guarantee that select_with_uidvalidity()
sets UIDNEXT for the mailbox and use it in fetch_new_messages()
to ensure that UIDNEXT always advances even
when there are no messages to fetch.
Winmail Pro Mail Server 5.1.0616 does not return UIDNEXT
in response to SELECT, but returns it when explicitly requested
via STATUS command:
? SELECT INBOX
* FLAGS (\Draft \Answered \Flagged \Deleted \Seen \Recent)
* OK [PERMANENTFLAGS (\Draft \Answered \Flagged \Deleted \Seen)] Limited
* 2 EXISTS
* 0 RECENT
* OK [UIDVALIDITY 1697802109] Ok
? OK [READ-WRITE] Ok SELECT completed
? STATUS INBOX (UIDNEXT)
* STATUS "INBOX" (UIDNEXT 4)
? OK STATUS completed
Previously used FETCH method is reported to fail for some users,
the FETCH command sometimes returns no results.
Besides, there is no guarantee that the message with
the highest sequence number has the highest UID.
In the worst case if STATUS does not return UIDNEXT
in response to explicit request, we fall back to setting
UIDNEXT to 1 instead of returning an error.
Set connectivity status to "connected" at the end of connect() call.
Otherwise for servers that do not support IMAP IDLE
connect() is called at the beginning of fake idle
and connectivity stays in "connecting" status most of the time.
Some Dovecot servers are configured
to alias "INBOX.DeltaChat" and "DeltaChat" to the same folder.
In this case Delta Chat moves new emails from "INBOX"
to "DeltaChat", but then discovers the same mail in "INBOX.DeltaChat"
and tries to move it to "DeltaChat" again.
Each time a MOVE command is issued to move the message
from "INBOX.DeltaChat" to "DeltaChat", the message gets a new UID.
To prevent such IMAP move loop between aliased folders,
we do not move the message if we have already seen it on IMAP,
i.e. we have its Message-ID in the `imap` table.
Note that we do not use `rfc724_mid_exists`,
because it checks the `msgs` table and would consider
BCC-self messages seen even before we see them in the Inbox,
preventing their move to the DeltaChat folder.
Duplicate messages and messages without Message-IDs
are not moved anymore, but this is better
than having an infinite move loop.
Message.set_text() and Message.get_text() are modified accordingly
to accept String and return String.
Messages which previously contained None text
are now represented as messages with empty text.
Use Message.set_text("".to_string())
instead of Message.set_text(None).
According to RFC 3501, EXISTS must always be sent in response to SELECT.
But if the server does not send it for some reason,
async-imap uses the default value, so we will essentially fetch `1:*`
and downloading all messages may take a long time.
Moved custom ToSql trait including Send + Sync from lib.rs to sql.rs.
Replaced most params! and paramsv! macro usage with tuples.
Replaced paramsv! and params_iterv! with params_slice!,
because there is no need to construct a vector.
To handle backups the UIs have to make sure they do stop the IO
scheduler and also don't accidentally restart it while working on it.
Since they have to call start_io from a bunch of locations this can be
a bit difficult to manage.
This introduces a mechanism for the core to pause IO for some time,
which is used by the imex function. It interacts well with other
calls to dc_start_io() and dc_stop_io() making sure that when resumed
the scheduler will be running or not as the latest calls to them.
This was a little more invasive then hoped due to the scheduler. The
additional abstraction of the scheduler on the context seems a nice
improvement though.
IIRC, this was written this way back when we didn't have config caching,
in order to save database accesses by getting the config outside the
for loop.
Gmail archives messages marked as `\Deleted` by default if those messages aren't in the Trash. But
if move them to the Trash instead, they will be auto-deleted in 30 days.
This allows to distinguish exceptions,
such as database errors, from invalid user input.
For example, if the From: field of the message
does not look like an email address, the mail
should be ignored. But if there is a database
failure while writing a new contact for the address,
this error should be bubbled up.
There are at least two user reports that fetching existing messages
sometimes results in infinite loop of retrying it. Account is working
if set up from the backup, but never starts working if set up
from scratch.
This change improves error reporting, but also sets FetchedExistingMsgs
before actually trying to do it. This way if the operation fails,
connection is reestablished, but fetching existing messages is not
retried again over and over.
async-imap does not do its own buffering, but calls flush() after
sending each command. Using BufWriter reduces the number of write()
system calls used to send a single command.
Note that BufWriter is set up on top of TLS streams, because
we can't guarantee that TLS libraries flush the stream before
waiting for response.
IMAP capabilities and selected folder are IMAP session,
not IMAP client property.
Moving most operations into IMAP session structure
removes the need to constantly check whether IMAP session exists
and reduces number of invalid states, e.g. when a folder is selected but
there is no connection.
Capabilities are determined immediately after logging in,
so there is no need for `capabilities_determined` flag anymore.
Capabilities of the server are always known if there is a session.
`should_reconnect` flag and `disconnect()` function are removed: we
drop the session on error. Even though RFC 3501 says that a client
SHOULD NOT close the connection without a LOGOUT, it is more reliable
to always just drop the connection, especially after an error.
When a batch of messages is moved from Inbox to DeltaChat folder with a single MOVE command, their
UIDs may be reordered (e.g. Gmail is known for that) which leads to that messages are processed by
receive_imf in the wrong order. But the INTERNALDATE attribute is preserved during a MOVE according
to RFC3501. So, use it for sorting fetched messages.
Since switch to async we don't have spurious "database is busy"
errors anymore. Since an error is irrecoverable in most cases,
we can skip the message. The cost of this is we may
accidentally skip a correct message if I/O fails, but
the advantage is that we are guaranteed to never confuse
irrecoverable error with recoverable one and get stuck in
infinite loop redownloading the same message over and over.
