* Add tests
* Fix some link previews being incorrectly generated from different prior links
PR #12403 added a cache to avoid redundant queries when the OEmbed endpoint can
be guessed from the URL. This caching mechanism is not perfectly correct as
there is no guarantee that all pages from a given domain share the same
OEmbed provider endpoint.
This PR prevents the FetchOEmbedService from caching OEmbed endpoint that
cannot be generalized by replacing a fully-qualified URL from the endpoint's
parameters, greatly reducing the number of incorrect cached generalizations.
* Add support for fetching Create and Announce activities by URI
This should improve compatibility with ZAP and offer a way to fetch boosts,
which is currently not possible.
* Add tests
* Add followed_by? to account_interactions
* Add RemoveFromFollowersService
* Fix AccountBatch to use RemoveFromFollowersService
* Add remove from followers API
Eliminate need to have custom notifications filtering logic in the
streaming API code by publishing notifications into a separate stream
and then simply using the multi-stream capability to subscribe to that
stream when necessary
Fix issue #16603 undefined method `serialize_payload' for Unsuspend Account Service error.
It seems that this service forgot to `include Payloadable` so that `serialize_payload` could not be found in this service.
* Add account statuses cleanup policy model
* Record last inspected toot to delete to speed up successive calls to statuses_to_delete
* Add service to cleanup a given account's statuses within a budget
* Add worker to go through account policies and delete old toots
* Fix last inspected status id logic
All existing statuses older or equal to last inspected status id must be
kept by the current policy. This is an invariant that must be kept so that
resuming deletion from the last inspected status remains sound.
* Add tests
* Refactor scheduler and add tests
* Add user interface
* Add support for discriminating based on boosts/favs
* Add UI support for min_reblogs and min_favs, rework UI
* Address first round of review comments
* Replace Snowflake#id_at_start with with_random parameter
* Add tests
* Add tests for StatusesCleanupController
* Rework settings page
* Adjust load-avoiding mechanisms
* Please CodeClimate
* Add account_notes relationship
* Add tests
* Fix owned account notes not being deleted when an account is deleted
* Add post-migration to clean up orphaned account notes
* Fix Delete and Create-related locks expiring too fast
Fixes#16238
By default, RedisLock expires after 10 seconds, which may not be enough to
process statuses, especially when those have attached media files.
This commit extends those 10 seconds to 15 minutes, which should be plenty
enough to handle any status, while being short enough to not waste many
sidekiq job retries in the exceedingly rare case in which a sidekiq process
would crash when processing a `Create` or `Delete`.
* Fix other RedisLock autorelease durations
Fixes#15645
- things that only perform a few simple database queries (e.g. finding and
saving a record) have been left unchanged, so they'll still use the default
10s duration
- things that perform significantly more complex database queries have been
changed to a 5 minutes timeout
- things that perform multiple HTTP queries have been changed to a 15 minutes
timeout
If a status with a hashtag becomes very popular, it stands to
reason that the hashtag should have a chance at trending
Fix no stats being recorded for hashtags that are not allowed
to trend, and stop ignoring bots
Remove references to hashtags in profile directory from the code
and the admin UI
* Add tests
* Ensure deleted statuses are marked as such
* Save some redis memory by not storing URIs in delete_upon_arrival values
* Avoid possible race condition when processing incoming Deletes
* Avoid potential duplicate Delete forwards
* Lower lock durations to reduce issues in case of hard crash of the Rails process
* Check for `lock.aquired?` and improve comment
* Refactor RedisLock usage in app/lib/activitypub
* Fix using incorrect or non-existent sender for relaying Deletes
* Update devise-two-factor to unreleased fork for Rails 6 support
Update tests to match new `rotp` version.
* Update nsa gem to unreleased fork for Rails 6 support
* Update rails to 6.1.3 and rails-i18n to 6.0
* Update to unreleased fork of pluck_each for Ruby 6 support
* Run "rails app:update"
* Add missing ActiveStorage config file
* Use config.ssl_options instead of removed ApplicationController#force_ssl
Disabled force_ssl-related tests as they do not seem to be easily testable
anymore.
* Fix nonce directives by removing Rails 5 specific monkey-patching
* Fix fixture_file_upload deprecation warning
* Fix yield-based test failing with Rails 6
* Use Rails 6's index_with when possible
* Use ActiveRecord::Cache::Store#delete_multi from Rails 6
This will yield better performances when deleting an account
* Disable Rails 6.1's automatic preload link headers
Since Rails 6.1, ActionView adds preload links for javascript files
in the Links header per default.
In our case, that will bloat headers too much and potentially cause
issues with reverse proxies. Furhermore, we don't need those links,
as we already output them as HTML link tags.
* Switch to Rails 6.0 default config
* Switch to Rails 6.1 default config
* Do not include autoload paths in the load path
* Update twitter-text from 1.14 to 3.1.0
* Disable emoji parsing
* Properly depend on twitter-text for url detection
* Fix some URLs being wrongly detected client-side
* Add test for server-side validation of non-autolinkable URLs
* Fix server-side status length counting
* Change ResolveAccountService's handling of skip_webfinger
Change it so it never makes any webfinger query, as the name would imply.
* Add tests
* Change FollowService to not take an URI for target_account
* Restore domain-block check in FollowService
* Fix tests
* disable NewCops
* update TargetRubyVersion
* Fix Lint/MissingSuper for ActiveModelSerializers::Model
* Fix Lint/MissingSuper for feed
* Fix Lint/FloatComparison
* Do not use instance variables
* Fix being able to import more than allowed number of follows
Without this commit, if someone tries importing a second list of accounts to
follow before the first one has been processed, this will queue imports for
the two whole lists, even if they exceed the account's allowed number of
outgoing follows.
This commit changes it so the individual queued imports aren't exempt from
the follow limit check (they remain exempt from the rate-limiting check
though).
* Catch validation errors to not re-queue failed follows
Co-authored-by: Claire <claire.github-309c@sitedethib.com>
As a regression from the recent optimizations, mentions were left untouched
until `account.destroy`, which would then delete them individually,
and executing queries to find and delete associated notifications, resulting
in a massive slowdown.
Co-authored-by: Claire <claire.github-309c@sitedethib.com>
* Delete status records by batches of 50
* Do not precompute values that are only used once
* Do not generate redis events for removal of public toots older than two weeks
* Filter reported toots a priori for polls and status deletion
* Do not process reblogs when cleaning up public timelines
As in Mastodon proper, reblogs don't appear in public TLs
* Clean the deleted account's own feed in one go
* Refactor Account#clean_feed_manager and List#clean_feed_manager
* Delete instead of destroy a few more associations
* Fix preloading
Co-authored-by: Claire <claire.github-309c@sitedethib.com>
* Fix deleting polls not deleting notifications
* Fix fav notification deletion when deleting a toot
* Refactor DeleteAccountService spec
* Add DeleteAccountService tests for other associations and notifications
* Add favourite handling spec in status removal
Co-authored-by: Claire <claire.github-309c@sitedethib.com>
* Fix account deletion workers being queued multiple times for a single account
* Fix poll votes being unnecessarily instantiated on poll deletion
* Fix favourites being unnecessarily instantiated on status deletion
* Remove inaccurate comments
* Delete polls instead of destroying them
Co-authored-by: Claire <claire.github-309c@sitedethib.com>
* Fix ResolveAccountService accepting mismatching acct: URI
* Set attributes that should be updated regardless of suspension
* Fix key fetching
* Automatically merge remote accounts with duplicate `uri`
* Add tests
* Add "tootctl accounts fix-duplicates"
Finds duplicate accounts sharing a same ActivityPub `id`, re-fetch them and
merge them under the canonical `acct:` URI.
Co-authored-by: Claire <claire.github-309c@sitedethib.com>
* Improve searching for private toots from URL
Most of the time, when sharing toots, people use the toot URL rather than
the toot URI, which makes sense since it is the user-facing URL.
In Mastodon's case, the URL and URI are different, and Mastodon does not
have an index on URL, which means searching a private toot by URL is done
with a slow query that will only succeed for very recent toots.
This change gets rid of the slow query, and attempts to guess the URI from
URL instead, as Mastodon's are predictable.
* Add tests
* Only return status with guessed uri if url matches
Co-authored-by: Claire <claire.github-309c@sitedethib.com>
* Add indication to admin UI of whether a report has been forwarded
* Rework how forwarded status is displayed
Co-authored-by: Claire <claire.github-309c@sitedethib.com>
Extract logic for determining ActivityPub inboxes to send deletes
to to its own class and explicitly include the person the status
replied to (even if not mentioned), people who favourited it, and
people who replied to it (though that one is still not recursive)
* Fix webfinger redirect handling in ResolveAccountService
ResolveAccountService#process_webfinger! handled a one-step webfinger
redirection, but only accepting the result if it matched the exact URI passed
as input, defeating the point of a redirection check.
Instead, use the same logic as in `ActivityPub::FetchRemoteAccountService`,
updating the resulting `acct:` URI with the result of the first webfinger
query.
* Add tests
Nginx can be configured to bypass proxy cache when a special header
is in the request. If the response is cacheable, it will replace
the cache for that request. Proxy caching of media files is
desirable when using object storage as a way of minimizing bandwidth
costs, but has the drawback of leaving deleted media files for
a configured amount of cache time. A cache buster can make those
media files immediately unavailable. This especially makes sense
when suspending and unsuspending an account.
* Fix crash in SuspendAccountWorker
`follows` is an array thanks to `to_a`
* Fix code style issue
Co-authored-by: Eugen Rochko <eugen@zeonfederated.com>
e.g. if someone on an instance that previously had followers gets mentioned
in a private toot, before this PR, they would not receive a
Collection-Synchronization header and may show the toot to the former followers
in addition to the mentioned person.
* Add support for followers synchronization on the receiving end
Check the `collectionSynchronization` attribute on `Create` and `Announce`
activities and synchronize followers from provided collection if possible.
* Add tests for followers synchronization on the receiving end
* Add support for follower synchronization on the sender's end
* Add tests for the sending end
* Switch from AS attributes to HTTP header
Replace the custom `collectionSynchronization` ActivityStreams attribute by
an HTTP header (`X-AS-Collection-Synchronization`) with the same syntax as
the `Signature` header and the following fields:
- `collectionId` to specify which collection to synchronize
- `digest` for the SHA256 hex-digest of the list of followers known on the
receiving instance (where “receiving instance” is determined by accounts
sharing the same host name for their ActivityPub actor `id`)
- `url` of a collection that should be fetched by the instance actor
Internally, move away from the webfinger-based `domain` attribute and use
account `uri` prefix to group accounts.
* Add environment variable to disable followers synchronization
Since the whole mechanism relies on some new preconditions that, in some
extremely rare cases, might not be met, add an environment variable
(DISABLE_FOLLOWERS_SYNCHRONIZATION) to disable the mechanism altogether and
avoid followers being incorrectly removed.
The current conditions are:
1. all managed accounts' actor `id` and inbox URL have the same URI scheme and
netloc.
2. all accounts whose actor `id` or inbox URL share the same URI scheme and
netloc as a managed account must be managed by the same Mastodon instance
as well.
As far as Mastodon is concerned, breaking those preconditions require extensive
configuration changes in the reverse proxy and might also cause other issues.
Therefore, this environment variable provides a way out for people with highly
unusual configurations, and can be safely ignored for the overwhelming majority
of Mastodon administrators.
* Only set follower synchronization header on non-public statuses
This is to avoid unnecessary computations and allow Follow-related
activities to be handled by the usual codepath instead of going through
the synchronization mechanism (otherwise, any Follow/Undo/Accept activity
would trigger the synchronization mechanism even if processing the activity
itself would be enough to re-introduce synchronization)
* Change how ActivityPub::SynchronizeFollowersService handles follow requests
If the remote lists a local follower which we only know has sent a follow
request, consider the follow request as accepted instead of sending an Undo.
* Integrate review feeback
- rename X-AS-Collection-Synchronization to Collection-Synchronization
- various minor refactoring and code style changes
* Only select required fields when computing followers_hash
* Use actor URI rather than webfinger domain in synchronization endpoint
* Change hash computation to be a XOR of individual hashes
Makes it much easier to be memory-efficient, and avoid sorting discrepancy issues.
* Marginally improve followers_hash computation speed
* Further improve hash computation performances by using pluck_each
There are edge cases where requests to certain hosts timeout when
using the vanilla HTTP.rb gem, which the goldfinger gem uses. Now
that we no longer need to support OStatus servers, webfinger logic
is so simple that there is no point encapsulating it in a gem, so
we can just use our own Request class. With that, we benefit from
more robust timeout code and IPv4/IPv6 resolution.
Fix#14091
* Add bell button
Fix#4890
* Remove duplicate type from post-deployment migration
* Fix legacy class type mappings
* Improve query performance with better index
* Fix validation
* Remove redundant index from notifications
DISTINCT clause removes duplicated records according to all the selected
attributes. In reality, it can remove duplicated records only looking at
statuses.id, but the clause confuses the query planner and yields
insufficient performance.
The behavior is also problematic if the scope produced by HashQueryService
is used to query columns without id (using pluck method, for example). The
scope is expected to contain unique statuses, but the uniquness will be
evaluated with some arbitrary columns other than id.
GROUP BY clause resolves those problem by explicitly specifying the
column to take into account for the record distinction.
A workaround for the problem of DISTINCT clause in
Api::V1::Timelines::TagController is no longer necessary and removed.
- Change audio files to not be stripped of metadata
- Automatically extract cover art from audio if it exists
- Add `thumbnail` parameter to `POST /api/v1/media`, `POST /api/v2/media` and `PUT /api/v1/media/:id`
- Add `icon` to represent it in attachments in ActivityPub
- Fix `preview_url` containing URL of missing missing image when there is no thumbnail instead of null
- Fix duration of audio not being displayed on public pages until the file is loaded
* Split media cleanup from reject-media domain blocks to its own service
* Slightly improve ClearDomainMediaService error handling
* Lower DomainClearMediaWorker to lowest-priority queue
* Do not catch ActiveRecord::RecordNotFound in domain block workers
* Fix DomainBlockWorker spec labels
* Add some specs
* Change domain blocks to immediately mark accounts as suspended
Rather than doing so sequentially, account after account, while cleaning
their data. This doesn't change much about the time the block takes to
complete, but it immediately prevents interaction with the blocked domain,
while up to now, it would only be guaranteed when the process ends.
Mastodon enforces the “sensitive” flag on media attachments whenever a toot
is posted with a Content Warning. However, it does so *after* potentially
converting the Content Warning to toot text (when there is no toot text),
which leads to inconsistent and surprising behavior for API clients.
This commit fixes this inconsistency.
Only look up private toots from database if the request failed because of 401,
403 or 404 errors, as those may indicate a private toot, rather than something
that isn't a toot or cannot be processed.
* Change ActivityPub follower/following collections to not link first page
* Add support for hiding followers and following of remote users
* Switch to using a single `hide_collections` column
* Address code style remarks
Fixes#13136
When a user's canonical acct domain is different from its id's domain
(WEB_DOMAIN ≠ LOCAL_DOMAIN), two webfinger queries are required to find the
canonical domain from the URI. However, we skip webfinger queries when
updating only the key of a remote user, which led to the creation of a
duplicate account, using the URI's domain instead of the canonical acct: one.
* Fix invalid votes from the API being accepted
Fixes#12556
- Ensure `choice` is an integer instead of silently converting to 0
- Ensure `choice` corresponds to an actual choice of the poll
* Please CodeClimate
This changes the REST API to return unicode domains in the `acct`
attribute instead of punycode, and to render unicode instead of
punycode on public HTML pages as well.
Fix#7812, fix#12246
* Make BackupService resilient to read timeouts
If an attachment read times out, assume that the resources is
inaccessible and continue the backup without it. This fixes#12280.
* Both errors on one line
* Remove “protocol” argument and return value, as only ActivityPub is supported
* Remove FetchRemoteAccountService, only use ActivityPub::FetchRemoteAccountService
* Fix tests
* Add follow_request notification type
The notification type already existed in the backend but was never pushed
to the front-end. This also means translation strings were also available
for the backend, from the notification mailer.
Unlike other notification types, these are off by default, to match what
I remember of Gargron's view on the topic: that follow requests should not
clutter notifications and should instead be reviewed at the user's own
leisure in the dedicated column.
Since follow requests have their own column, I've deemed it unnecessary to
add a specific tab for them in the notification quick filter.
* Show follow request link in single-column if there are pending requests, even if account isn't locked
* Push follow requests from notifications to the follow_requests list
* Offer to accept or reject follow request from the notification
* Redesign follow request notification
If a poll contains empty options (which is apparently possible on Pleroma),
it is created without them. However, the poll update code doesn't filter
empty options, and thus:
1. Clear known votes, as it assumes the set of options has changed
2. Errors out because it tries adding empty options, which fails validation
This commit fixes that by filtering them out the same way they are filtered
out at poll creation time.
When suspending or silencing a domain, one probably wants the silence or
suspend parts to take effect as soon as possible. Deleting media files can
take a while (possibly days), so perform silencing as soon as possible, and
clean up media afterwards.
* add youtube oembed endpoint
* add check for oembed endpoint
* change unless for a more readable if
* clear blank lines
* endpoint via https
* Fix string literal in condition
* use cache for endpoints
* use cache for endpoints
* clean up and adding check
* clean up and remove redundant return
* add html check
* add false to return
* use double quotes
* use double quotes
* Clean up
* Add backend support for bookmarks
Bookmarks behave like favourites, except they aren't shared with other
users and do not have an associated counter.
* Add spec for bookmark endpoints
* Add front-end support for bookmarks
* Introduce OAuth scopes for bookmarks
* Add bookmarks to archive takeout
* Fix migration
* Coding style fixes
* Fix rebase issue
* Update bookmarked_statuses to latest UI changes
* Update bookmark actions to properly reflect status changes in state
* Add bookmarks item to single-column layout
* Make active bookmarks red
* Fix already-known remote private toots not being searchable by URL
Whenever an URL search fails, and an account is provided, try getting a
private status matching that URL from database.
* Fix searching by `id` field instead of `uri`
* Fix being able to follow oneself by moving to an account that was following the old one
* Add specs
* Add spec to catch MoveWorker issue with local followers following both accounts
* Fix move worker breaking when a local account follows both source and target accounts
* Fix migration from remote to local account not sending Undo Follow
* Fix show_reblogs not being preserved for moved account's followers
* Add ability to add oneself to lists
* Change search results to include oneself when searching through followers
* Mark follow relation as optional in ListAccount
* Add test to handle suspended and missing users in BootstrapTimelineService
* Fix BootstrapTimelineService crashing when bootstrapped accounts are invalid
* Add voters count to polls
* Add ActivityPub serialization and parsing of voters count
* Add support for voters count in WebUI
* Move incrementation of voters count out of redis lock
* Reword “voters” to “people”
* Change silenced accounts to require approval on follow
* Also require approval for follows by people explicitly muted by target accounts
* Do not auto-accept silenced or muted accounts when switching from locked to unlocked
* Add `follow_requests_count` to verify_credentials
* Show “Follow requests” menu item if needed even if account is locked
* Add tests
* Correctly reflect that follow requests weren't auto-accepted when local account is silenced
* Accept follow requests from user-muted accounts to avoid leaking mutes
The reason for unattaching media instead of removing it is to support
delete & redraft functionality, but remote or staff-removed statuses
will never be redrafted, so the media should be deleted immediately
* Add more accurate hashtag search
Using ElasticSearch to index hashtags with edge n-grams and score
them by usage within the last 7 days since last activity. Only
hashtags that have been reviewed and are listable can appear in
searches, unless they match the query exactly
* Fix search analyzer dropping non-ascii characters
- Restrict followers counts to local users to minimize local advantage
- Fix emoji shortcodes causing error in search
- Fix search syntax parse errors not being caught
* Add more accurate account search
When ElasticSearch is available, a more accurate search is implemented:
- Using edge n-gram index for acct and display name
- Using asciifolding and cjk width normalization on display names
- Using Gaussian decay on account activity for additional scoring (recency)
- Using followers/friends ratio for additional scoring (spamminess)
- Using followers number for additional scoring (size)
The exact match precedence only takes effect when the input conforms
to the username format and the username part of it is complete, i.e.
when the user started typing the domain part.
* Support single-letter usernames
* Fix tests
* Fix not picking up account updates
* Add weights and normalization for scores, skip zero terms queries
* Use local counts for accounts index, adjust search parameters
* Fix mistakes
* Using updated_at of accounts is inadequate for remote accounts
* Add database columns for adding notes to domain blocks/restrctions
* Add admin UI to set private and public comments when blocking a domain
* Add text for private and public comments on domain blocks
* Show domain block comments in admin UI
* Add comments to the domain block undo page
* Make UnblockDomainService more robust regarding upgraded domain blocks
* Allow editing domain blocks
* Rename button from “undo domain block” to “view domain block” in account admin UI
* Change test to unsilence silenced users from upgraded blocks
* Add a spam check
* Use Nilsimsa to generate locality-sensitive hashes and compare using Levenshtein distance
* Add more tests
* Add exemption when the message is a reply to something that mentions the sender
* Use Nilsimsa Compare Value instead of Levenshtein distance
* Use MD5 for messages shorter than 10 characters
* Add message to automated report, do not add non-public statuses to
automated report, add trust level to accounts and make unsilencing
raise the trust level to prevent repeated spam checks on that account
* Expire spam check data after 3 months
* Add support for local statuses, reduce expiration to 1 week, always create a report
* Add content warnings to the spam check and exempt empty statuses
* Change Nilsimsa threshold to 95 and make sure removed statuses are removed from the spam check
* Add all matched statuses into automatic report
* Fix BackupService crashing when an attachment is missing
For various reasons such as admin error or out-of-sync media and
database backups, it might be possible for local attachments to be lost.
This commit allows the BackupService to continue its work even if some media
file is missing.
* Change error message
* Remove Salmon and PubSubHubbub endpoints
* Add error when trying to follow OStatus accounts
* Fix new accounts not being created in ResolveAccountService
* Change domain blocks to automatically support subdomains
If a more authoritative domain is blocked (example.com), then the
same block will be applied to a subdomain (foo.example.com)
* Match subdomains of existing accounts when blocking/unblocking domains
* Improve code style
* Add audio uploads
Fix#4827
Accept uploads of OGG, WAV, FLAC, OPUS and MP3 files, and converts
them to OGG. Media attachments get a new `audio` type. In the UI,
audio uploads are displayed identically to video uploads.
* Improve code style
* Record account suspend/silence time and keep track of domain blocks
* Also unblock users who were suspended/silenced before dates were recorded
* Add tests
* Keep track of suspending date for users suspended through the CLI
* Show accurate number of accounts that would be affected by unsuspending an instance
* Change migration to set silenced_at and suspended_at
* Revert "Also unblock users who were suspended/silenced before dates were recorded"
This reverts commit a015c65d2d1e28c7b7cfab8b3f8cd5fb48b8b71c.
* Switch from using suspended and silenced to suspended_at and silenced_at
* Add post-deployment migration script to remove `suspended` and `silenced` columns
* Use Account#silence! and Account#suspend! instead of updating the underlying property
* Add silenced_at and suspended_at migration to post-migration
* Change account fabricator to translate suspended and silenced attributes
* Minor fixes
* Make unblocking domains always retroactive
The @property attribute in HTML is a space-separated list of values.
This change normalizes whitespace and finds the desired value in
the list instead of requiring an exact single-value match.
More details:
https://www.ctrl.blog/entry/rdfa-socialmedia-metadata.html
* Refactor imports
* Export show_reblogs when exporting list of followed users
* Add support for importing show_reblogs with following collection
* Fix tests
* Revert "Fix filtering of favourited_by, reblogged_by, followers and following (#10447)"
This reverts commit 120544067f.
* Revert "Hide blocking accounts from blocked users (#10442)"
This reverts commit 62bafa20a1.
* Improve blocked view of profiles
- Change "You are blocked" to "Profile unavailable"
- Hide following/followers in API when blocked
- Disable follow button and show "Profile unavailable" on public profile as well
* Revert "Add indication that you have been blocked in web UI (#10420)"
This reverts commit bd02ec6daa.
* Revert "Add `blocked_by` relationship to the REST API (#10373)"
This reverts commit 9745de883b.
* Hide blocking accounts from search results
* Filter blocking accouts from account followers
* Filter blocking accouts from account's following accounts
* Filter blocking accounts from “reblogged by” and “favourited by” lists
* Remove blocking account from URL search
* Return 410 on trying to fetch user data from a user who blocked us
* Return 410 in /api/v1/account/statuses for suspended or blocking accounts
* Fix status filtering when performing URL search
* Restore some React improvements
Restore some cleanup from bd02ec6daa
* Refactor by adding `without_blocking` scope
* Fix poll update handler calling method was that was not available
Fix regression from #10209
* Refactor VoteService
* Refactor ActivityPub::DistributePollUpdateWorker and optimize it
* Fix typo
* Fix typo