lib-sieve: Made the retention period for redirect duplicate identifie…

…rs configurable.

For accounts that perform many redirects, the lda-dupes database could grow to impractical sizes.
Changed the default retention period from 24 to 12 hours.

INSTALL

@@ -271,6 +271,16 @@ plugin section of the config file (default values are shown if applicable):
    the envelope sender of the redirected message is also always "<>",
    irrespective of what is configured for this setting. 
 
+ sieve_redirect_duplicate_period = 12h
+   In an effort to halt potential mail loops, the Sieve redirect action records
+   identifying information for messages it has forwarded. If a duplicate message
+   is seen, it is not redirected and the message is discarded; i.e., the
+   implicit keep is canceled. This setting configures the period during which
+   the identifying information is recorded. If an account forwards many
+   messages, it may be necessary to lower this setting to prevent the
+   ~/.dovecot.lda-dupes database file (in which these are recorded) from growing
+   to an impractical size.
+
 For example:
 
 plugin {

src/lib-sieve/cmd-redirect.c

@@ -29,12 +29,6 @@
 
 #include <stdio.h>
 
-/*
- * Configuration
- */
-
-#define CMD_REDIRECT_DUPLICATE_KEEP (3600 * 24)
-
 /*
  * Redirect command
  *
@@ -422,6 +416,7 @@ static int act_redirect_commit
 	const struct sieve_action_exec_env *aenv, void *tr_context ATTR_UNUSED,
 	bool *keep)
 {
+	struct sieve_instance *svinst = aenv->svinst;
 	struct act_redirect_context *ctx =
 		(struct act_redirect_context *) action->context;
 	struct sieve_message_context *msgctx = aenv->msgctx;
@@ -501,7 +496,7 @@ static int act_redirect_commit
 
 		/* Mark this message id as forwarded to the specified destination */
 		sieve_action_duplicate_mark(senv, dupeid, strlen(dupeid),
-			ioloop_time + CMD_REDIRECT_DUPLICATE_KEEP);
+			ioloop_time + svinst->redirect_duplicate_period);
 
 		sieve_result_global_log(aenv, "forwarded to <%s>",
 			str_sanitize(ctx->to_address, 128));

src/lib-sieve/sieve-common.h

@@ -203,6 +203,7 @@ struct sieve_instance {
 	unsigned int max_redirects;
 	const struct sieve_address *user_email;
 	struct sieve_address_source redirect_from;
+	unsigned int redirect_duplicate_period;
 };
 
 /*

src/lib-sieve/sieve-config.h

@@ -14,4 +14,6 @@
 
 #define DEFAULT_ENVELOPE_SENDER "MAILER-DAEMON"
 
+#define DEFAULT_REDIRECT_DUPLICATE_PERIOD (3600 * 12)
+
 #endif

src/lib-sieve/sieve-settings.c

@@ -206,6 +206,7 @@ void sieve_settings_load
 	const char *str_setting;
 	unsigned long long int uint_setting;
 	size_t size_setting;
+	sieve_number_t period;
 
 	svinst->max_script_size = SIEVE_DEFAULT_MAX_SCRIPT_SIZE;
 	if ( sieve_setting_get_size_value
@@ -229,6 +230,15 @@ void sieve_settings_load
 		svinst->pool, "sieve_redirect_envelope_from",
 		&svinst->redirect_from);
 
+	svinst->redirect_duplicate_period = DEFAULT_REDIRECT_DUPLICATE_PERIOD;
+	if ( sieve_setting_get_duration_value
+		(svinst, "sieve_redirect_duplicate_period", &period) ) {
+		if (period > UINT_MAX)
+			svinst->redirect_duplicate_period = UINT_MAX;
+		else
+			svinst->redirect_duplicate_period = (unsigned int)period;
+	}
+
 	str_setting = sieve_setting_get(svinst, "sieve_user_email");
 	if ( str_setting != NULL && *str_setting != '\0' ) {
 		svinst->user_email =