From: Grigorii Demidov <grigorii.demidov@nic.cz>
Date: Mon, 26 Jun 2017 10:20:39 +0000 (+0200)
Subject: lib/resolve: better support for forwarder choice
X-Git-Tag: v1.3.2~14^2~2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=cd2755bf635573251bea46f33f68f68f3f8a6b22;p=thirdparty%2Fknot-resolver.git

lib/resolve: better support for forwarder choice
---

diff --git a/lib/nsrep.c b/lib/nsrep.c
index 564caf30c..dd089e13f 100644
--- a/lib/nsrep.c
+++ b/lib/nsrep.c
@@ -335,3 +335,56 @@ int kr_nsrep_copy_set(struct kr_nsrep *dst, const struct kr_nsrep *src)
 
 	return kr_ok();
 }
+
+int kr_nsrep_elect_min_rtt(struct kr_query *qry)
+{
+	/* TODO - sorting instead of searching minimum? */
+	struct kr_nsrep *ns = &qry->ns;
+
+	if (ns->addr[0].ip.sa_family == AF_UNSPEC) {
+		return kr_error(EINVAL);
+	}
+
+	if (ns->addr[1].ip.sa_family == AF_UNSPEC) {
+		/* We have only one entry here, do nothing */
+		return kr_ok();
+	}
+
+	const struct kr_context *ctx = ns->ctx;
+	if (!ctx) {
+		return kr_ok();
+	}
+
+	const struct sockaddr *sock = (const struct sockaddr *)(&ns->addr[0]);
+	unsigned *score = lru_get_try(ctx->cache_rtt, kr_inaddr(sock),
+				      kr_family_len(sock->sa_family));
+	unsigned minimal_score = (score) ? *score : KR_NS_MAX_SCORE + 1;
+	int i = 1;
+	sock = (const struct sockaddr *)(&ns->addr[i]);
+	do {
+		score = lru_get_try(ctx->cache_rtt, kr_inaddr(sock),
+				    kr_family_len(sock->sa_family));
+		if (score) {
+			if (*score < minimal_score) {
+				union inaddr temp_addr = ns->addr[0];
+				ns->addr[0] = ns->addr[i];
+				ns->addr[i] = temp_addr;
+				ns->score = *score;
+				ns->reputation = 0;
+				minimal_score = ns->score;
+			} else if ((kr_rand_uint(100) < 10) &&
+			    (kr_rand_uint(KR_NS_MAX_SCORE) >= *score)) {
+				/* long distance probe */
+				union inaddr temp_addr = ns->addr[0];
+				ns->addr[0] = ns->addr[i];
+				ns->addr[i] = temp_addr;
+				ns->score = *score;
+				ns->reputation = 0;
+				break;
+			}
+		}
+		sock = (const struct sockaddr *)(&ns->addr[++i]);
+	} while ((i < KR_NSREP_MAXADDR) && (sock->sa_family != AF_UNSPEC));
+
+	return kr_ok();
+}
diff --git a/lib/nsrep.h b/lib/nsrep.h
index 302d984c1..9ca108c4c 100644
--- a/lib/nsrep.h
+++ b/lib/nsrep.h
@@ -150,3 +150,12 @@ int kr_nsrep_update_rep(struct kr_nsrep *ns, unsigned reputation, kr_nsrep_lru_t
  * @return              0 on success, error code on failure
  */
 int kr_nsrep_copy_set(struct kr_nsrep *dst, const struct kr_nsrep *src);
+
+/**
+ * Elect address with minimal rtt within current query nsrep list
+ * @note   ns reputation is zeroed
+ * @param  qry          updated query
+ * @return              0 or an error code
+ */
+KR_EXPORT
+int kr_nsrep_elect_min_rtt(struct kr_query *qry);
diff --git a/lib/resolve.c b/lib/resolve.c
index 3b2c008c7..2ef2cd0a3 100644
--- a/lib/resolve.c
+++ b/lib/resolve.c
@@ -1378,9 +1378,11 @@ ns_election:
 		return KR_STATE_FAIL;
 	}
 
-	const bool retry = (qry->flags & (QUERY_TCP|QUERY_STUB|QUERY_FORWARD|QUERY_BADCOOKIE_AGAIN));
+	const bool retry = (qry->flags & (QUERY_TCP|QUERY_STUB|QUERY_BADCOOKIE_AGAIN));
 	if (qry->flags & (QUERY_AWAIT_IPV4|QUERY_AWAIT_IPV6)) {
 		kr_nsrep_elect_addr(qry, request->ctx);
+	} else if (qry->flags & QUERY_FORWARD) {
+		kr_nsrep_elect_min_rtt(qry);
 	} else if (!qry->ns.name || !retry) { /* Keep NS when requerying/stub/badcookie. */
 		/* Root DNSKEY must be fetched from the hints to avoid chicken and egg problem. */
 		if (qry->sname[0] == '\0' && qry->stype == KNOT_RRTYPE_DNSKEY) {