When receiving an mDNS request, send a unicast response back.

[meshlink] / src / mdns.c

diff --git a/src/mdns.c b/src/mdns.c
index b243b3ae0430c671333211baa24f5ee1fac1145b..79de309f8805f12442671fa469ea50b33ede58b3 100644 (file)
--- a/src/mdns.c
+++ b/src/mdns.c
@@ -247,14 +247,14 @@ static void buf_check_len_end(cbuf_t *buf, const uint8_t *ptr) {
        }
 }
 
-size_t prepare_packet(void *vdata, size_t size, const char *name, const char *protocol, const char *transport, uint16_t port, int nkeys, const char **keys, const char **values) {
+size_t prepare_packet(void *vdata, size_t size, const char *name, const char *protocol, const char *transport, uint16_t port, int nkeys, const char **keys, const char **values, bool response) {
        // Create the request/response packet right now
        uint8_t *data = vdata;
        buf_t buf = {data, size};
 
        // Header
        buf_add_uint16(&buf, 0); // TX ID
-       buf_add_uint16(&buf, 0); // flags
+       buf_add_uint16(&buf, response ? ntohs(1 << 15) : 0); // flags
        buf_add_uint16(&buf, 1); // 1 question
        buf_add_uint16(&buf, 1); // 1 answer RR
        buf_add_uint16(&buf, 0); // 0 authority RRs
@@ -314,22 +314,24 @@ size_t prepare_packet(void *vdata, size_t size, const char *name, const char *pr
        }
 }
 
-bool parse_packet(const void *vdata, size_t size, char **name, const char *protocol, const char *transport, uint16_t *port, int nkeys, const char **keys, char **values) {
+bool parse_packet(const void *vdata, size_t size, char **name, const char *protocol, const char *transport, uint16_t *port, int nkeys, const char **keys, char **values, bool *response) {
        const uint8_t *data = vdata;
        cbuf_t buf = {data, size};
 
        // Header
        buf_check_uint16(&buf, 0); // TX ID
-       buf_check_uint16(&buf, 0); // flags
+       uint16_t flags = buf_get_uint16(&buf); // flags
        buf_check_uint16(&buf, 1); // 1 question
        buf_check_uint16(&buf, 1); // 1 answer RR
        buf_check_uint16(&buf, 0); // 0 authority RRs
        buf_check_uint16(&buf, 2); // 1 checkitional RR
 
-       if(buf.len == -1) {
+       if(buf.len == -1 || flags & ~ntohs(1 << 15)) {
                return false;
        }
 
+       *response = flags & ntohs(1 << 15);
+
        // Question section: _protocol._transport.local PTR IN
        buf_check_ulabel(&buf, protocol);
        buf_check_ulabel(&buf, transport);