fix negative response and non-response handling for dns queries

previously, all failures to obtain at least one address were treated
as nonexistant names (EAI_NONAME). this failed to account for the
possibility of transient failures (no response at all, or a response
with rcode of 2, server failure) or permanent failures that do not
indicate the nonexistence of the requested name. only an rcode of 3
should be treated as an indication of nonexistence.
This commit is contained in:
Rich Felker 2014-06-03 01:46:40 -04:00
parent ac2a789342
commit d85d261ee6

View File

@ -151,7 +151,10 @@ static int name_from_dns(struct address buf[static MAXADDRS], char canon[static
for (i=0; i<nq; i++) for (i=0; i<nq; i++)
__dns_parse(abuf[i], alens[i], dns_parse_callback, &ctx); __dns_parse(abuf[i], alens[i], dns_parse_callback, &ctx);
return ctx.cnt; if (ctx.cnt) return ctx.cnt;
if (alens[0] < 4 || (abuf[0][3] & 15) == 2) return EAI_AGAIN;
if ((abuf[0][3] & 15) == 3) return EAI_NONAME;
return EAI_FAIL;
} }
int __lookup_name(struct address buf[static MAXADDRS], char canon[static 256], const char *name, int family, int flags) int __lookup_name(struct address buf[static MAXADDRS], char canon[static 256], const char *name, int family, int flags)