skip edns frag retry if advertised udp payload size is not smaller

If serviced query is in UDP_EDNS_FRAG mode, and EDNS_ADVERTISED_SIZE
is 1232 (the default) or more, then the retry will have the same edns
udp payload size with the same result.

diff --git a/services/outside_network.c b/services/outside_network.c
index c3a6a163892c63abde13bce6e1b3b19e45765875..1f89740da360fb4d960a0c820ffcdd3a30aef059 100644 (file)
--- a/services/outside_network.c
+++ b/services/outside_network.c
@@ -2820,6 +2820,25 @@ serviced_perturb_qname(struct ub_randstate* rnd, uint8_t* qbuf, size_t len)
        }
 }
 
+static uint16_t
+serviced_query_udp_size(struct serviced_query* sq, enum serviced_query_status status) {
+       uint16_t udp_size;
+       if(status == serviced_query_UDP_EDNS_FRAG) {
+               if(addr_is_ip6(&sq->addr, sq->addrlen)) {
+                       if(EDNS_FRAG_SIZE_IP6 < EDNS_ADVERTISED_SIZE)
+                               udp_size = EDNS_FRAG_SIZE_IP6;
+                       else    udp_size = EDNS_ADVERTISED_SIZE;
+               } else {
+                       if(EDNS_FRAG_SIZE_IP4 < EDNS_ADVERTISED_SIZE)
+                               udp_size = EDNS_FRAG_SIZE_IP4;
+                       else    udp_size = EDNS_ADVERTISED_SIZE;
+               }
+       } else {
+               udp_size = EDNS_ADVERTISED_SIZE;
+       }
+       return udp_size;
+}
+
 /** put serviced query into a buffer */
 static void
 serviced_encode(struct serviced_query* sq, sldns_buffer* buff, int with_edns)
@@ -2843,19 +2862,7 @@ serviced_encode(struct serviced_query* sq, sldns_buffer* buff, int with_edns)
                edns.opt_list_in = NULL;
                edns.opt_list_out = sq->opt_list;
                edns.opt_list_inplace_cb_out = NULL;
-               if(sq->status == serviced_query_UDP_EDNS_FRAG) {
-                       if(addr_is_ip6(&sq->addr, sq->addrlen)) {
-                               if(EDNS_FRAG_SIZE_IP6 < EDNS_ADVERTISED_SIZE)
-                                       edns.udp_size = EDNS_FRAG_SIZE_IP6;
-                               else    edns.udp_size = EDNS_ADVERTISED_SIZE;
-                       } else {
-                               if(EDNS_FRAG_SIZE_IP4 < EDNS_ADVERTISED_SIZE)
-                                       edns.udp_size = EDNS_FRAG_SIZE_IP4;
-                               else    edns.udp_size = EDNS_ADVERTISED_SIZE;
-                       }
-               } else {
-                       edns.udp_size = EDNS_ADVERTISED_SIZE;
-               }
+               edns.udp_size = serviced_query_udp_size(sq, sq->status);
                edns.bits = 0;
                if(sq->dnssec & EDNS_DO)
                        edns.bits = EDNS_DO;
@@ -3252,7 +3259,8 @@ serviced_udp_callback(struct comm_point* c, void* arg, int error,
 
        sq->pending = NULL; /* removed after callback */
        if(error == NETEVENT_TIMEOUT) {
-               if(sq->status == serviced_query_UDP_EDNS && sq->last_rtt < 5000) {
+               if(sq->status == serviced_query_UDP_EDNS && sq->last_rtt < 5000 &&
+                  (serviced_query_udp_size(sq, serviced_query_UDP_EDNS_FRAG) < serviced_query_udp_size(sq, serviced_query_UDP_EDNS))) {
                        /* fallback to 1480/1280 */
                        sq->status = serviced_query_UDP_EDNS_FRAG;
                        log_name_addr(VERB_ALGO, "try edns1xx0", sq->qbuf+10,