From b4badf720ce484001f606011aee7cd216e5ce4e3 Mon Sep 17 00:00:00 2001
From: Baptiste Assmann <bedis9@gmail.com>
Date: Thu, 19 Nov 2020 22:38:33 +0100
Subject: [PATCH] BUG/MINOR: resolvers: new callback to properly handle SRV
 record errors

When a SRV record was created, it used to register the regular server name
resolution callbacks. That said, SRV records and regular server name
resolution don't work the same way, furthermore on error management.

This patch introduces a new call back to manage DNS errors related to
the SRV queries.

this fixes github issue #50.

Backport status: 2.3, 2.2, 2.1, 2.0
---
 include/haproxy/server.h |  1 +
 src/resolvers.c          |  2 +-
 src/server.c             | 72 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 74 insertions(+), 1 deletion(-)

diff --git a/include/haproxy/server.h b/include/haproxy/server.h
index 4d41e27716..a38c4144e8 100644
--- a/include/haproxy/server.h
+++ b/include/haproxy/server.h
@@ -61,6 +61,7 @@ struct server *new_server(struct proxy *proxy);
 int snr_update_srv_status(struct server *s, int has_no_ip);
 const char *update_server_fqdn(struct server *server, const char *fqdn, const char *updater, int dns_locked);
 int snr_resolution_cb(struct resolv_requester *requester, struct dns_counters *counters);
+int srvrq_resolution_error_cb(struct resolv_requester *requester, int error_code);
 int snr_resolution_error_cb(struct resolv_requester *requester, int error_code);
 struct server *snr_check_ip_callback(struct server *srv, void *ip, unsigned char *ip_family);
 struct task *srv_cleanup_idle_connections(struct task *task, void *ctx, unsigned short state);
diff --git a/src/resolvers.c b/src/resolvers.c
index a64896eb25..a10600b06e 100644
--- a/src/resolvers.c
+++ b/src/resolvers.c
@@ -1739,7 +1739,7 @@ int resolv_link_resolution(void *requester, int requester_type, int requester_lo
 			req = srvrq->requester;
 
 		req->requester_cb       = snr_resolution_cb;
-		req->requester_error_cb = snr_resolution_error_cb;
+		req->requester_error_cb = srvrq_resolution_error_cb;
 	}
 	else if (stream) {
 		if (stream->resolv_ctx.requester == NULL) {
diff --git a/src/server.c b/src/server.c
index 732643cbc4..2582e92a5d 100644
--- a/src/server.c
+++ b/src/server.c
@@ -4071,6 +4071,78 @@ int snr_resolution_cb(struct resolv_requester *requester, struct dns_counters *c
 	return 0;
 }
 
+/*
+ * SRV record error management callback
+ * returns:
+ *  0 on error
+ *  1 when no error or safe ignore
+ *
+ * Grabs the server's lock.
+ */
+int srvrq_resolution_error_cb(struct resolv_requester *requester, int error_code)
+{
+	struct server *s;
+	struct resolv_srvrq *srvrq;
+	struct resolv_resolution *res;
+	struct resolvers *resolvers;
+	int exp;
+
+	/* SRV records */
+	srvrq = objt_resolv_srvrq(requester->owner);
+	if (!srvrq)
+		return 1;
+
+	resolvers = srvrq->resolvers;
+	res = requester->resolution;
+
+	switch (res->status) {
+
+		case RSLV_STATUS_NX:
+			/* stop server if resolution is NX for a long enough period */
+			exp = tick_add(res->last_valid, resolvers->hold.nx);
+			if (!tick_is_expired(exp, now_ms))
+				return 1;
+			break;
+
+		case RSLV_STATUS_TIMEOUT:
+			/* stop server if resolution is TIMEOUT for a long enough period */
+			exp = tick_add(res->last_valid, resolvers->hold.timeout);
+			if (!tick_is_expired(exp, now_ms))
+				return 1;
+			break;
+
+		case RSLV_STATUS_REFUSED:
+			/* stop server if resolution is REFUSED for a long enough period */
+			exp = tick_add(res->last_valid, resolvers->hold.refused);
+			if (!tick_is_expired(exp, now_ms))
+				return 1;
+			break;
+
+		default:
+			/* stop server if resolution failed for a long enough period */
+			exp = tick_add(res->last_valid, resolvers->hold.other);
+			if (!tick_is_expired(exp, now_ms))
+				return 1;
+	}
+
+	/* Remove any associated server */
+	for (s = srvrq->proxy->srv; s != NULL; s = s->next) {
+		HA_SPIN_LOCK(SERVER_LOCK, &s->lock);
+		if (s->srvrq == srvrq) {
+			snr_update_srv_status(s, 1);
+			free(s->hostname);
+			free(s->hostname_dn);
+			s->hostname        = NULL;
+			s->hostname_dn     = NULL;
+			s->hostname_dn_len = 0;
+			resolv_unlink_resolution(s->resolv_requester);
+		}
+		HA_SPIN_UNLOCK(SERVER_LOCK, &s->lock);
+	}
+
+	return 1;
+}
+
 /*
  * Server Name Resolution error management callback
  * returns: