Record the resolution start time on errors.

Also only record samples on the first try for a server.

BUG: 25731675

Change-Id: I10a68813c6636874e63aca1db661e63e1af72a2d

diff --git a/libc/dns/resolv/res_send.c b/libc/dns/resolv/res_send.c
index 0e30b28..4c4b953 100644 (file)
--- a/libc/dns/resolv/res_send.c
+++ b/libc/dns/resolv/res_send.c
@@ -552,10 +552,17 @@ res_nsend(res_state statp,
                        n = send_vc(statp, buf, buflen, ans, anssiz, &terrno,
                                    ns, &now, &rcode, &delay);
 
-                       struct __res_sample sample;
-                       _res_stats_set_sample(&sample, now, rcode, delay);
-                       _resolv_cache_add_resolver_stats_sample(statp->netid, revision_id, ns,
-                               &sample, params.max_samples);
+                       /*
+                        * Only record stats the first time we try a query. This ensures that
+                        * queries that deterministically fail (e.g., a name that always returns
+                        * SERVFAIL or times out) do not unduly affect the stats.
+                        */
+                       if (try == 0) {
+                               struct __res_sample sample;
+                               _res_stats_set_sample(&sample, now, rcode, delay);
+                               _resolv_cache_add_resolver_stats_sample(statp->netid, revision_id,
+                                       ns, &sample, params.max_samples);
+                       }
 
                        if (DBG) {
                                __libc_format_log(ANDROID_LOG_DEBUG, "libc",
@@ -576,10 +583,13 @@ res_nsend(res_state statp,
                        n = send_dg(statp, buf, buflen, ans, anssiz, &terrno,
                                    ns, &v_circuit, &gotsomewhere, &now, &rcode, &delay);
 
-                       struct __res_sample sample;
-                       _res_stats_set_sample(&sample, now, rcode, delay);
-                       _resolv_cache_add_resolver_stats_sample(statp->netid, revision_id, ns,
-                               &sample, params.max_samples);
+                       /* Only record stats the first time we try a query. See above. */
+                       if (try == 0) {
+                               struct __res_sample sample;
+                               _res_stats_set_sample(&sample, now, rcode, delay);
+                               _resolv_cache_add_resolver_stats_sample(statp->netid, revision_id,
+                                       ns, &sample, params.max_samples);
+                       }
 
                        if (DBG) {
                                __libc_format_log(ANDROID_LOG_DEBUG, "libc", "used send_dg %d\n",n);
@@ -741,7 +751,7 @@ send_vc(res_state statp,
        const u_char *buf, int buflen, u_char *ans, int anssiz,
        int *terrno, int ns, time_t* at, int* rcode, int* delay)
 {
-       *at = 0;
+       *at = time(NULL);
        *rcode = RCODE_INTERNAL_ERROR;
        *delay = 0;
        const HEADER *hp = (const HEADER *)(const void *)buf;
@@ -919,9 +929,6 @@ send_vc(res_state statp,
                return (0);
        }
 
-       struct timespec done = evNowTime();
-       *at = done.tv_sec;
-
        if (truncating) {
                /*
                 * Flush rest of answer so connection stays in synch.
@@ -959,6 +966,7 @@ send_vc(res_state statp,
         * next nameserver ought not be tried.
         */
        if (resplen > 0) {
+           struct timespec done = evNowTime();
            *delay = _res_stats_calculate_rtt(&done, &now);
            *rcode = anhp->rcode;
        }
@@ -1074,7 +1082,7 @@ send_dg(res_state statp,
        int *terrno, int ns, int *v_circuit, int *gotsomewhere,
        time_t *at, int *rcode, int* delay)
 {
-       *at = 0;
+       *at = time(NULL);
        *rcode = RCODE_INTERNAL_ERROR;
        *delay = 0;
        const HEADER *hp = (const HEADER *)(const void *)buf;
@@ -1261,7 +1269,6 @@ retry:
                goto retry;;
        }
        done = evNowTime();
-       *at = done.tv_sec;
        *delay = _res_stats_calculate_rtt(&done, &now);
        if (anhp->rcode == SERVFAIL ||
            anhp->rcode == NOTIMP ||