servewaf always answers rproxy well within its time limit (closes #182)

A question waits on GeoJS at most 800ms, the new default of
SWWAF_LOOKUP_TIMEOUT. In enforce mode it does not wait at all when it is
over the header limits, on a fetched blocklist with deny, on the CrowdSec
decision list, or over a whole rate limit. Not waiting never lowers a
client's limit. Just before the Core Rule Set, servewaf refuses more than
50 cookies or 100 header fields with 431.

Shared default changed: SWWAF_LOOKUP_TIMEOUT also applies to smallwebwaf
with no command.
Judgement call: SWWAF_REPUTATION_TIMEOUT stays 2s, since no request waits
on the DNS blocklists or AbuseIPDB.

Model: opus-5-5

docs/metrics.md

@@ -17,7 +17,8 @@ label as `exported_instance` unless the scrape sets `honor_labels: true`.
 
 - `smallwebwaf_rate_limit_hits_total`, by `window` and by `kind` (`requests`,
   `bytes` or `refusals`);
-- `smallwebwaf_size_and_time_limit_hits_total`, by `limit`, the setting passed;
+- `smallwebwaf_size_and_time_limit_hits_total`, by `limit`, the setting passed.
+  `servewaf`'s header limits have no setting, so it leaves them out;
 - `smallwebwaf_offences_total`, by `kind`;
 - `smallwebwaf_bans_made_total`, by `cause`;
 - `smallwebwaf_active_bans` and `smallwebwaf_permanent_bans`.

docs/request-log.md

@@ -67,7 +67,8 @@ Every line has:
       CrowdSec decision, each of which bans the client;
     - `country_denied`, `rate_limited`, `rule_blocked` and `waf_blocked`:
       refused by that check;
-    - `too_large` and `timed_out`: a size or time limit was passed;
+    - `too_large`: a size limit was passed, or a header limit in `servewaf`;
+    - `timed_out`: a time limit was passed;
     - `upstream_error`: the app could not be reached, or its answer broke off;
     - `admin`: answered at one of `smallwebwaf`'s own endpoints.
 - `would_action`: in `observe` mode, what `enforce` mode would have done with a

docs/settings.md

@@ -157,7 +157,7 @@ that take `off`, the `_FILE` form, and what each group does and why.
     - an anomaly threshold per AS number.
 - `SWWAF_LOOKUP_DB_PATH` (default empty): the IPinfo Lite database file, in its
   `.mmdb` form, for `SWWAF_LOOKUP_SOURCE=file`.
-- `SWWAF_LOOKUP_TIMEOUT` (default `1s`): how long a request waits for its
+- `SWWAF_LOOKUP_TIMEOUT` (default `800ms`): how long a request waits for its
   client's first answer from GeoJS, and how long a request to GeoJS may take. A
   duration; never `off`.
 - `SWWAF_ADD_LOOKUP_HEADERS` (default `false`): `true` passes the app the
@@ -340,7 +340,10 @@ A few limits are fixed rather than settings:
 - at most 1,000 DNS blocklist queries are under way at once;
 - at most 20,000 anomaly counters are kept;
 - each alert destination's queue holds at most 1,000 alerts;
-- `servewaf` holds at most 10,000 answered requests awaiting their reports.
+- `servewaf` holds at most 10,000 answered requests awaiting their reports;
+- `servewaf` refuses a request with more than 50 cookies or more than 100 header
+  fields (see "Answering in time" under "`servewaf`" in
+  [`SPEC.md`](../SPEC.md)).
 
 ## `servewaf`
 
@@ -358,3 +361,9 @@ at start still shows them.
 request to an app. `SWWAF_WAF_BODY_LIMIT` has an effect up to 64 KiB less one
 byte, whatever its value. A question carries no more of a body than 64 KiB (see
 "`servewaf`" in [`SPEC.md`](../SPEC.md)).
+
+`SWWAF_LOOKUP_TIMEOUT` is the longest a question waits on an outside source.
+Keep it well under `rproxy`'s `SWRP_TIMEOUT_MS`, as the default is. No question
+waits for `SWWAF_REPUTATION_TIMEOUT`, since the DNS blocklists and AbuseIPDB are
+asked in the background (see "Answering in time" under "`servewaf`" in
+[`SPEC.md`](../SPEC.md)).