Update info on each module. New bottom sections.

Author: TonyGravagno

doc/modules/index.md

@@ -27,18 +27,21 @@ and [here](faq.html#what-are-the-locald-and-overrided-directories).
 
 Available C modules:
 
-- [chartable](chartable.html): checks character sets of text parts in messages. (Note:
-"char" as in character, and "table" as in a table of character sets.)
-- [dkim](dkim.html): performs DKIM signatures checks.
-- [fuzzy_check](fuzzy_check.html): checks a message's fuzzy hashes against public blacklists.
-- [regexp](regexp.html): a core module that deals with regular expressions, internal
+- [chartable](chartable.html) - checks character sets of text parts in messages.
+  - (Note: "char" as in character, and "table" as in a table of character sets.)
+- [dkim](dkim.html) - performs [DKIM](http://www.dkim.org/) signatures checks.
+   - The `dkim` C module was previously used for both checking for inbound signatures and for
+  writing outbound signatures. Now these feature are separated, where [dkim](dkim.html) processes inbound
+  messages and the [dkim_signing](dkim_signing.html) Lua module processes outbound messages.
+- [fuzzy_check](fuzzy_check.html) - checks a message's fuzzy hashes against public blacklists.
+- [regexp](regexp.html) - a core module that deals with regular expressions, internal
 functions and Lua code to filter messages.
 
 In prior releases other C modules were enabled by default:
 
-- [spf](spf.html): checks SPF records for messages processed. This C module was removed in
+- [spf](spf.html) - checks SPF records for messages processed. This C module was removed in
 version 2.3 and replaced by an equivalent Lua module.
-- [surbl](surbl.html): extracts URLs from messages and check them against
+- [surbl](surbl.html) - extracts URLs from messages and check them against
 public DNS black-lists to filter messages containing malicious URLs. This module was removed
 in version 2.0 and replaced by the [rbl module](rbl.html). In an upgrade to v2, the existing
 configuration is automatically converted.
@@ -61,22 +64,29 @@ modules {
 If a path is a directory then Rspamd scans it for `*.lua` pattern and load all
 files matched.
 
-The following Lua modules are enabled in the default configuration (but may require additional configuration to work, see notes below):
+The following Lua modules are enabled in the default configuration. Except where noted with a trailing asterisk,
+each of these modules has its own module_name.conf file in $LOCAL_CONFDIR/modules.d. Some modules require
+additional configuration to work, see notes below. :
 
 - [antivirus](antivirus.html) - integrates virus scanners (requires configuration)
 - [arc](arc.html) - checks and signs ARC signatures
 - [asn](asn.html) - looks up ASN-related information
-- [clickhouse](clickhouse.html) - pushes scan-related information to clickhouse DBMS (requires configuration)
-- [bayes_expiry](bayes_expiry.html) - provides expiration of statistical tokens (requires Redis and configuration)
+- [clickhouse](clickhouse.html) - pushes scan-related information to the clickhouse DBMS (requires configuration)
+- [bayes_expiry](bayes_expiry.html) - provides expiration of statistical tokens (requires Redis and configuration) *
 - [dcc](dcc.html) - performs [DCC](http://www.dcc-servers.net/dcc/) lookups to determine message bulkiness (requires configuration)
-- [dkim_signing](dkim_signing.html) - adds DKIM signatures to messages (requires configuration)
-- [dmarc](dmarc.html) - performs DMARC policy checks (requires Redis & configuration for reporting)
+- [dkim_signing](dkim_signing.html) - adds [DKIM](http://www.dkim.org/) signatures to messages (requires configuration)
+   - The `dkim` C module was previously used for both checking for inbound signatures and for
+  writing outbound signatures. Now these feature are separated, where [dkim](dkim.html) processes inbound
+  messages and the [dkim_signing](dkim_signing.html) Lua module processes outbound messages.
+- [dmarc](dmarc.html) - performs DMARC policy checks (requires Redis and configuration for reporting)
 - [elastic](elastic.html) - pushes scan-related information to Elasticsearch. (requires configuration)
-- [emails](emails.html) - extract emails from a message and checks it against DNS blacklists. (requires configuration)
+- [external_services](external_services.html) - allows use of many external services (requires configuration)
 - [force_actions](force_actions.html) - forces actions if selected symbols are detected (requires configuration)
-- [greylisting](greylisting.html) - allows to delay suspicious messages (requires Redis)
+- [forged_recipients](forged_recipients.html) - Check forged recipients **and senders** (e.g. mime and smtp recipients mismatch (requires configuration)
+- [greylist](greylisting.html) - allows suspicious messages to be delayed (requires Redis)
+  - Some documentation refers to this as the 'greylist**ing**' module, but internally it is seen as 'greylist'.
+- [hfilter](hfilter.html) - filters some known bad patterns in hostnames, received headers, helo domains and reverse dns (requires configuration)
 - [history redis](history_redis.html) - stores history in Redis (requires Redis)
-- [ip_score](ip_score.html) - dynamically scores sender reputation (requires Redis). This module is removed since Rspamd 2.0 and replaced by [reputation module](reputation.html). The existing configuration is automatically converted by Rspamd.
 - [maillist](maillist.html) - determines the common mailing list signatures in a message.
 - [metadata_exporter](metadata_exporter.html) - pushes message metadata to external systems (requires configuration)
 - [metric_exporter](metric_exporter.html) - pushes statistics to external monitoring systems (requires configuration)
@@ -85,30 +95,65 @@ The following Lua modules are enabled in the default configuration (but may requ
 - [mime_types](mime_types.html) - applies some rules about mime types met in messages
 - [multimap](multimap.html) - a complex module that operates with different types of maps.
 - [neural networks](neural.html) - allows to post-process messages using neural network classification. (requires Redis).
+  - Some documentation refers to this as the 'neural **network**' module, but internally it is referenced as just 'neural'.
 - [once_received](once_received.html) - detects messages with a single `Received` headers and performs some additional checks for such messages.
 - [phishing](phishing.html) - detects messages with phished URLs.
 - [ratelimit](ratelimit.html) - implements leaked bucket algorithm for ratelimiting (requires Redis & configuration)
-- [replies](replies.html) - checks if an incoming message is a reply for our own message (requires Redis)
 - [rbl](rbl.html) - a plugin that checks messages against DNS runtime blacklists.
+- [replies](replies.html) - checks if an incoming message is a reply for our own message (requires Redis)
 - [reputation](reputation.html) - a plugin that manages reputation evaluation based on various rules.
 - [rspamd_update](rspamd_update.html) - load dynamic rules and other Rspamd updates (requires configuration)
 - [spamassassin](spamassassin.html) - load spamassassin rules (requires configuration)
 - [spf.html](spf.html) - perform SPF checks
 - [trie](trie.html) - uses suffix trie for extra-fast patterns lookup in messages. (requires configuration)
-- [whitelist](whitelist.html) - provides a flexible way to whitelist (or blacklist) messages based on SPF/DKIM/DMARC combinations
 - [url_redirector](url_redirector.html) - dereferences redirects (requires Redis configuration)
+- [whitelist](whitelist.html) - provides a flexible way to whitelist (or blacklist) messages based on SPF/DKIM/DMARC combinations
+
+The following modules have been removed or deprecated:
+
+- [emails](emails.html) - extract email addresses from a message and checks them against DNS blacklists. (requires configuration)
+  - Deprecated, use [rbl](rbl.html).
+- [ip_score](ip_score.html) - dynamically scores sender reputation (requires Redis).
+  - Removed as of v2.0 and replaced by the [reputation module](reputation.html). The existing configuration
+in older installations is automatically converted by an Rspamd upgrade.
 
 The following modules are explicitly disabled in the default configuration, set `enabled = true` in `local.d/${MODULE_NAME}.conf` to enable them:
 
 - [mx_check](mx_check.html) - checks if sending domain has a connectable MX (requires Redis)
+- **p0f** - see below
+- [spamtrap](spamtrap.html) - catch spam trapped emails or even a catch-all domain. Intended for learning Bayes spam. (requires configuration)
 
-The following modules are explicitly disabled and are experimental, so you need to set `enabled = true` in `local.d/${MODULE_NAME}.conf` **AND** to set the global option `enable_experimental = true` in `local.d/options.inc`:
+The following modules are explicitly disabled and are experimental, see below to Enable a module **AND** set the global option `enable_experimental = true` in `local.d/options.inc`:
 
 - [url_reputation](url_reputation.html) - assigns reputation to domains in URLs (requires Redis). Removed in Rspamd 2.0.
 - [url_tags](url_tags.html) - persists URL tags in Redis (requires Redis). Removed in Rspamd 2.0.
 
 Experimental modules are not recommended for production usage!
 
+The following modules require documentation:
+
+- **http_headers**
+- **p0f** - passive OS fingerprinting : [Wikipedia](https://en.wikipedia.org/wiki/P0f) / Rspamd [PR #3037](https://github.com/rspamd/rspamd/pull/3037)
+
+
 ## Disabling module
 
-To disable an entire module you can set `enabled = false;` in `/etc/rspamd/local.d/${MODULE_NAME}.conf`
+To disable an entire module set `enabled = false;` in `$LOCAL_CONFDIR/local.d/${MODULE_NAME}.conf`.
+
+## Enabling a disabled module
+
+To enable an entire module set `enabled = true;` in `$LOCAL_CONFDIR/local.d/${MODULE_NAME}.conf`.
+
+## Config file locations for modules
+
+Here are some guidelines regarding where module configurations are stored:
+
+- The Rspamd-provided configuration files are in `$LOCAL_CONFDIR/modules.d`.
+- Your overrides are set in `$LOCAL_CONFDIR/local.d`
+- The value of `$LOCAL_CONFDIR` is usually `$PREFIX/etc/rspamd`
+- The value of `$CONFDIR` is usually the same as `$LOCAL_CONFDIR`
+- The value of `$PREFIX` is usually null
+- So defaults are usually in `/etc/rspamd/modules.d`, overrides in `/etc/rspamd/local.d`
+- These $values may be changed at build time - the rules here apply for a default build
+- To see the values of the environment variables that are actually being used by Rspamd at run-time,
+Run `rspamadm lua` and enter `rspamd_paths` at the prompt. This returns a JSON object with values. Ctrl-C to exit.