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-rw-r--r--src/network/res_msend.c27
1 files changed, 22 insertions, 5 deletions
diff --git a/src/network/res_msend.c b/src/network/res_msend.c
index 5192b4d8..35f106dd 100644
--- a/src/network/res_msend.c
+++ b/src/network/res_msend.c
@@ -34,7 +34,7 @@ int __res_msend(int nqueries, const unsigned char *const *queries,
FILE *f, _f;
unsigned char _buf[256];
char line[64], *s, *z;
- int timeout = 5000, attempts = 2, retry_interval;
+ int timeout = 5000, attempts = 2, retry_interval, servfail_retry;
union {
struct sockaddr_in sin;
struct sockaddr_in6 sin6;
@@ -152,6 +152,7 @@ int __res_msend(int nqueries, const unsigned char *const *queries,
qlens[i], MSG_NOSIGNAL,
(void *)&ns[j], sl);
t1 = t2;
+ servfail_retry = 2 * nqueries;
}
/* Wait for a response, or until time to retry */
@@ -160,12 +161,12 @@ int __res_msend(int nqueries, const unsigned char *const *queries,
while ((rlen = recvfrom(fd, answers[next], asize, 0,
(void *)&sa, (socklen_t[1]){sl})) >= 0) {
- /* Ignore non-identifiable packets (no query id) */
- if (rlen < 2) continue;
+ /* Ignore non-identifiable packets */
+ if (rlen < 4) continue;
/* Ignore replies from addresses we didn't send to */
- for (i=0; i<nns && memcmp(ns+i, &sa, sl); i++);
- if (i==nns) continue;
+ for (j=0; j<nns && memcmp(ns+j, &sa, sl); j++);
+ if (j==nns) continue;
/* Find which query this answer goes with, if any */
for (i=next; i<nqueries && (
@@ -174,6 +175,22 @@ int __res_msend(int nqueries, const unsigned char *const *queries,
if (i==nqueries) continue;
if (alens[i]) continue;
+ /* Only accept positive or negative responses;
+ * retry immediately on server failure, and ignore
+ * all other codes such as refusal. */
+ switch (answers[next][3] & 15) {
+ case 0:
+ case 3:
+ break;
+ case 2:
+ if (servfail_retry && servfail_retry--)
+ sendto(fd, queries[i],
+ qlens[i], MSG_NOSIGNAL,
+ (void *)&ns[j], sl);
+ default:
+ continue;
+ }
+
/* Store answer in the right slot, or update next
* available temp slot if it's already in place. */
alens[i] = rlen;