>From 19f8642494b7d27b2ceed5c14d4a0b27cb749afe Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Mon, 24 Aug 2020 21:56:48 -0400 Subject: [PATCH 2/2] report res_query failures, including nxdomain/nodata, via h_errno while it's not clearly documented anywhere, this is the historical behavior which some applications expect. applications which need to see the response packet in these cases, for example to distinguish between nonexistence in a secure vs insecure zone, must already use res_mkquery with res_send in order to be portable, since most if not all other implementations of res_query don't provide it. --- src/network/res_query.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/src/network/res_query.c b/src/network/res_query.c index 2f4da2e2..506dc231 100644 --- a/src/network/res_query.c +++ b/src/network/res_query.c @@ -1,3 +1,4 @@ +#define _BSD_SOURCE #include #include @@ -6,7 +7,20 @@ int res_query(const char *name, int class, int type, unsigned char *dest, int le unsigned char q[280]; int ql = __res_mkquery(0, name, class, type, 0, 0, 0, q, sizeof q); if (ql < 0) return ql; - return __res_send(q, ql, dest, len); + int r = __res_send(q, ql, dest, len); + if (r<12) { + h_errno = TRY_AGAIN; + return -1; + } + if ((dest[3] & 15) == 3) { + h_errno = HOST_NOT_FOUND; + return -1; + } + if ((dest[3] & 15) == 0 && !dest[6] && !dest[7]) { + h_errno = NO_DATA; + return -1; + } + return r; } weak_alias(res_query, res_search); -- 2.21.0