dns: allow limiting dns entry matching to cname name

Allows more precise control on how to match CNAME redirected subdomains

Signed-off-by: Felix Fietkau <nbd@nbd.name>

4 files changed, 18 insertions, 6 deletions

diff --git a/README b/README
index 485d030..10d0c55 100644
--- a/README
+++ b/README
@@ -104,9 +104,13 @@ match is one of:
 - dns:/<regex>
 	POSIX.2 extended regular expression for matching hostnames
 	Only works, if dns lookups are passed to qosify via the add_dns_host ubus call.
+- dns_c:...
+	Like dns:... but only matches cname entries
 
 dscp can be a raw value, or a codepoint like CS0
 Adding a + in front of the value tells qosify to only override the DSCP value if it is zero
+DNS entries are compared in the order in which they are specified in the config, using the
+first matching entry.
 
 
 Planned features:
diff --git a/dns.c b/dns.c
index 5d10c6d..b943ef5 100644
--- a/dns.c
+++ b/dns.c
@@ -169,7 +169,7 @@ dns_parse_question(struct packet *pkt, const void *hdr, uint8_t *dscp, uint32_t
 		return -1;
 
 	cname_cache_get(qname, dscp, seq);
-	qosify_map_lookup_dns_entry(qname, dscp, seq);
+	qosify_map_lookup_dns_entry(qname, false, dscp, seq);
 
 	return 0;
 }
@@ -202,7 +202,7 @@ dns_parse_answer(struct packet *pkt, void *hdr, uint8_t *dscp, uint32_t *seq)
 			      cname, sizeof(cname)) < 0)
 			return -1;
 
-		qosify_map_lookup_dns_entry(cname, dscp, seq);
+		qosify_map_lookup_dns_entry(cname, true, dscp, seq);
 		cname_cache_set(cname, *dscp, *seq);
 
 		return 0;
diff --git a/map.c b/map.c
index e413020..83e119b 100644
--- a/map.c
+++ b/map.c
@@ -406,6 +406,8 @@ int qosify_map_set_entry(enum qosify_map_id id, bool file, const char *str,
 	switch (id) {
 	case CL_MAP_DNS:
 		data.addr.dns.pattern = str;
+		if (str[-2] == 'c')
+			data.addr.dns.only_cname = 1;
 		break;
 	case CL_MAP_TCP_PORTS:
 	case CL_MAP_UDP_PORTS:
@@ -525,6 +527,8 @@ qosify_map_parse_line(char *str)
 
 	if (!strncmp(key, "dns:", 4))
 		qosify_map_set_entry(CL_MAP_DNS, true, key + 4, dscp);
+	if (!strncmp(key, "dns_q:", 6) || !strncmp(key, "dns_c:", 6))
+		qosify_map_set_entry(CL_MAP_DNS, true, key + 6, dscp);
 	if (!strncmp(key, "tcp:", 4))
 		qosify_map_set_entry(CL_MAP_TCP_PORTS, true, key + 4, dscp);
 	else if (!strncmp(key, "udp:", 4))
@@ -715,7 +719,7 @@ void qosify_map_gc(void)
 	uloop_timeout_set(&qosify_map_timer, timeout * 1000);
 }
 
-int qosify_map_lookup_dns_entry(char *host, uint8_t *dscp, uint32_t *seq)
+int qosify_map_lookup_dns_entry(char *host, bool cname, uint8_t *dscp, uint32_t *seq)
 {
 	struct qosify_map_data data = {
 		.id = CL_MAP_DNS,
@@ -738,6 +742,9 @@ int qosify_map_lookup_dns_entry(char *host, uint8_t *dscp, uint32_t *seq)
 		if (e->data.id != CL_MAP_DNS)
 			break;
 
+		if (!cname && e->data.addr.dns.only_cname)
+			continue;
+
 		if (e->data.addr.dns.pattern[0] == '/') {
 			if (regexec(regex, host, 0, NULL, 0) != 0)
 				continue;
@@ -763,7 +770,7 @@ int qosify_map_add_dns_host(char *host, const char *addr, const char *type, int
 	int prev_timeout = qosify_map_timeout;
 	uint32_t lookup_seq = 0;
 
-	if (qosify_map_lookup_dns_entry(host, &data.dscp, &lookup_seq))
+	if (qosify_map_lookup_dns_entry(host, false, &data.dscp, &lookup_seq))
 		return 0;
 
 	data.user = true;
diff --git a/qosify.h b/qosify.h
index 7a598e3..bd08879 100644
--- a/qosify.h
+++ b/qosify.h
@@ -51,7 +51,8 @@ struct qosify_map_data {
 		struct in_addr ip;
 		struct in6_addr ip6;
 		struct {
-			uint32_t seq;
+			uint32_t seq : 30;
+			uint32_t only_cname : 1;
 			const char *pattern;
 			regex_t regex;
 		} dns;
@@ -90,7 +91,7 @@ void qosify_map_set_dscp_default(enum qosify_map_id id, uint8_t val);
 void qosify_map_reset_config(void);
 void qosify_map_update_config(void);
 void qosify_map_set_classes(struct blob_attr *val);
-int qosify_map_lookup_dns_entry(char *host, uint8_t *dscp, uint32_t *seq);
+int qosify_map_lookup_dns_entry(char *host, bool cname, uint8_t *dscp, uint32_t *seq);
 int qosify_map_add_dns_host(char *host, const char *addr, const char *type, int ttl);
 int map_parse_flow_config(struct qosify_flow_config *cfg, struct blob_attr *attr,
 			  bool reset);