src/imap/cmd-idle.c

/* Copyright (c) 2002-2018 Dovecot authors, see the included COPYING file */

#include "imap-common.h"
#include "istream.h"
#include "ostream.h"
#include "crc32.h"
#include "mail-storage-settings.h"
#include "imap-commands.h"
#include "imap-keepalive.h"
#include "imap-sync.h"

struct cmd_idle_context {
    struct client *client;
    struct client_command_context *cmd;

    struct imap_sync_context *sync_ctx;
    struct timeout *keepalive_to, *to_hibernate;

    bool manual_cork:1;
    bool sync_pending:1;
};

static void idle_add_keepalive_timeout(struct cmd_idle_context *ctx);
static bool cmd_idle_continue(struct client_command_context *cmd);

static void
idle_finish(struct cmd_idle_context *ctx, bool done_ok, bool free_cmd)
{
    struct client *client = ctx->client;

    timeout_remove(&ctx->keepalive_to);
    timeout_remove(&ctx->to_hibernate);

    if (ctx->sync_ctx != NULL) {
        /* we're here only in connection failure cases */
        (void)imap_sync_deinit(ctx->sync_ctx, ctx->cmd);
    }

    o_stream_cork(client->output);
    io_remove(&client->io);

    if (client->mailbox != NULL)
        mailbox_notify_changes_stop(client->mailbox);

    if (done_ok)
        client_send_tagline(ctx->cmd, "OK Idle completed.");
    else
        client_send_tagline(ctx->cmd, "BAD Expected DONE.");

    o_stream_uncork(client->output);
    if (free_cmd)
        client_command_free(&ctx->cmd);
}

static bool
idle_client_handle_input(struct cmd_idle_context *ctx, bool free_cmd)
{
    const char *line;

    while ((line = i_stream_next_line(ctx->client->input)) != NULL) {
        if (ctx->client->input_skip_line)
            ctx->client->input_skip_line = FALSE;
        else {
            idle_finish(ctx, strcasecmp(line, "DONE") == 0,
                    free_cmd);
            return TRUE;
        }
    }
    return FALSE;
}

static bool idle_client_input_more(struct cmd_idle_context *ctx)
{
    struct client *client = ctx->client;

    client->last_input = ioloop_time;
    timeout_reset(client->to_idle);

    switch (i_stream_read(client->input)) {
    case -1:
        /* disconnected */
        client_disconnect(client, NULL);
        return TRUE;
    case -2:
        client->input_skip_line = TRUE;
        idle_finish(ctx, FALSE, TRUE);
        return TRUE;
    }

    if (ctx->sync_ctx != NULL) {
        /* we're still sending output to client. wait until it's all
           sent so we don't lose any changes. */
        io_remove(&client->io);
        return FALSE;
    }

    return idle_client_handle_input(ctx, TRUE);
}

static void idle_client_input(struct cmd_idle_context *ctx)
{
    struct client *client = ctx->client;

    if (idle_client_input_more(ctx)) {
        if (client->disconnected)
            client_destroy(client, NULL);
        else
            client_continue_pending_input(client);
    }
}

static void keepalive_timeout(struct cmd_idle_context *ctx)
{
    if (ctx->client->output_cmd_lock != NULL) {
        /* it's busy sending output */
        return;
    }

    if (o_stream_get_buffer_used_size(ctx->client->output) == 0) {
        /* Sending this keeps NATs/stateful firewalls alive.
           Sending this also catches dead connections. Don't send
           anything if there is already data waiting in output
           buffer. */
        o_stream_cork(ctx->client->output);
        client_send_line(ctx->client, "* OK Still here");
        o_stream_uncork(ctx->client->output);
    }
    /* Make sure idling connections don't get disconnected. There are
       several clients that really want to IDLE forever and there's not
       much harm in letting them do so. */
    timeout_reset(ctx->client->to_idle);
    /* recalculate time for the next keepalive timeout */
    idle_add_keepalive_timeout(ctx);
}

static bool idle_sync_now(struct mailbox *box, struct cmd_idle_context *ctx)
{
    i_assert(ctx->sync_ctx == NULL);

    /* hibernation can't happen while sync is running.
       the timeout is added back afterwards. */
    timeout_remove(&ctx->to_hibernate);

    ctx->sync_pending = FALSE;
    ctx->sync_ctx = imap_sync_init(ctx->client, box, 0, 0);
    return cmd_idle_continue(ctx->cmd);
}

static void idle_callback(struct mailbox *box, struct cmd_idle_context *ctx)
{
    struct client *client = ctx->client;

    if (ctx->sync_ctx != NULL)
        ctx->sync_pending = TRUE;
    else {
        ctx->manual_cork = TRUE;
        (void)idle_sync_now(box, ctx);
        if (client->disconnected)
            client_destroy(client, NULL);
    }
}

static void idle_add_keepalive_timeout(struct cmd_idle_context *ctx)
{
    struct client *client = ctx->client;
    unsigned int interval = client->set->imap_idle_notify_interval;

    if (interval == 0)
        return;

    interval = imap_keepalive_interval_msecs(client->user->username,
                         client->user->conn.remote_ip,
                         interval);

    timeout_remove(&ctx->keepalive_to);
    ctx->keepalive_to = timeout_add(interval, keepalive_timeout, ctx);
}

static void idle_hibernate_timeout(struct cmd_idle_context *ctx)
{
    struct client *client = ctx->client;

    i_assert(ctx->sync_ctx == NULL);
    i_assert(!ctx->sync_pending);

    if (imap_client_hibernate(&client)) {
        /* client may be destroyed now */
    } else {
        /* failed - don't bother retrying */
        timeout_remove(&ctx->to_hibernate);
    }
}

static void idle_add_hibernate_timeout(struct cmd_idle_context *ctx)
{
    unsigned int secs = ctx->client->set->imap_hibernate_timeout;

    i_assert(ctx->to_hibernate == NULL);

    if (secs == 0)
        return;

    ctx->to_hibernate =
        timeout_add(secs * 1000, idle_hibernate_timeout, ctx);
}

static bool cmd_idle_continue(struct client_command_context *cmd)
{
    struct client *client = cmd->client;
    struct cmd_idle_context *ctx = cmd->context;
    uoff_t orig_offset = client->output->offset;

    if (cmd->cancel) {
        idle_finish(ctx, FALSE, FALSE);
        return TRUE;
    }

    if (ctx->to_hibernate != NULL)
        timeout_reset(ctx->to_hibernate);

    if (ctx->manual_cork)  {
        /* we're coming from idle_callback instead of a normal
           I/O handler, so we'll have to do corking manually */
        o_stream_cork(client->output);
    }

    if (ctx->sync_ctx != NULL) {
        if (imap_sync_more(ctx->sync_ctx) == 0) {
            /* unfinished */
            if (ctx->manual_cork) {
                ctx->manual_cork = FALSE;
                o_stream_uncork(client->output);
            }
            cmd->state = CLIENT_COMMAND_STATE_WAIT_OUTPUT;
            return FALSE;
        }

        if (imap_sync_deinit(ctx->sync_ctx, ctx->cmd) < 0) {
            client_send_untagged_storage_error(client,
                mailbox_get_storage(client->mailbox));
            mailbox_notify_changes_stop(client->mailbox);
        }
        ctx->sync_ctx = NULL;
    }
    if (client->output->offset != orig_offset &&
        ctx->keepalive_to != NULL)
        idle_add_keepalive_timeout(ctx);

    if (ctx->sync_pending) {
        /* more changes occurred while we were sending changes to
           client.

           NOTE: this recurses back to this function,
           so we return here instead of doing everything twice. */
        return idle_sync_now(client->mailbox, ctx);
    }
    if (ctx->to_hibernate == NULL)
        idle_add_hibernate_timeout(ctx);
    cmd->state = CLIENT_COMMAND_STATE_WAIT_INPUT;

    if (ctx->manual_cork) {
        ctx->manual_cork = FALSE;
        o_stream_uncork(client->output);
    }

    if (client->output->closed) {
        idle_finish(ctx, FALSE, FALSE);
        return TRUE;
    }
    if (client->io == NULL) {
        /* input is pending. add the io back and mark the input as
           pending. we can't safely read more input immediately here. */
        client->io = io_add_istream(client->input,
                        idle_client_input, ctx);
        i_stream_set_input_pending(client->input, TRUE);
    }
    return FALSE;
}

bool cmd_idle(struct client_command_context *cmd)
{
    struct client *client = cmd->client;
    struct cmd_idle_context *ctx;

    ctx = p_new(cmd->pool, struct cmd_idle_context, 1);
    ctx->cmd = cmd;
    ctx->client = client;
    idle_add_keepalive_timeout(ctx);
    idle_add_hibernate_timeout(ctx);

    if (client->mailbox != NULL)
        mailbox_notify_changes(client->mailbox, idle_callback, ctx);
    if (!client->state_import_idle_continue)
        client_send_line(client, "+ idling");
    else {
        /* continuing an IDLE after hibernation */
        client->state_import_idle_continue = FALSE;
    }

    io_remove(&client->io);
    client->io = io_add_istream(client->input, idle_client_input, ctx);

    cmd->func = cmd_idle_continue;
    cmd->context = ctx;

    /* check immediately if there are changes. if they came before we
       added mailbox-notifier, we wouldn't see them otherwise. */
    if (client->mailbox != NULL)
        idle_sync_now(client->mailbox, ctx);
    return idle_client_handle_input(ctx, FALSE);
}