[prev in list] [next in list] [prev in thread] [next in thread] 

List:       busybox
Subject:    [PATCH 1/2] nslookup: handle replies without RRs
From:       Jo-Philipp Wich <jo () mein ! io>
Date:       2019-06-27 15:27:28
Message-ID: 20190627152729.6861-1-jo () mein ! io
[Download RAW message or body]

Under some circumstances, a DNS reply might contain no resource records,
e.g. when a valid domain is queried that does not have records of the
requested type.

Example with nslookup from BIND dnsutils:

    $ nslookup -q=SRV example.org
    Server:	10.11.12.13
    Address:	10.11.12.13#53

    Non-authoritative answer:
    *** Can't find example.org: No answer

Currently the busybox nslookup applet simply prints nothing after the
"Non-authoritative answer:" line in the same situation.

This change modifies nslookup to either print "Parse error" or "No answer"
diagnostics, depending on the parse_reply() return value.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>
---
 networking/nslookup.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/networking/nslookup.c b/networking/nslookup.c
index 24e09d4f0..f7fd1d377 100644
--- a/networking/nslookup.c
+++ b/networking/nslookup.c
@@ -615,9 +615,15 @@ static int send_queries(struct ns *ns)
 					G.query[qn].name, rcodes[rcode]);
 			G.exitcode = EXIT_FAILURE;
 		} else {
-			if (parse_reply(reply, recvlen) < 0) {
+			switch (parse_reply(reply, recvlen)) {
+			case -1:
 				printf("*** Can't find %s: Parse error\n", G.query[qn].name);
 				G.exitcode = EXIT_FAILURE;
+				break;
+
+			case 0:
+				printf("*** Can't find %s: No answer\n", G.query[qn].name);
+				break;
 			}
 		}
 		bb_putchar('\n');
-- 
2.11.0

_______________________________________________
busybox mailing list
busybox@busybox.net
http://lists.busybox.net/mailman/listinfo/busybox
[prev in list] [next in list] [prev in thread] [next in thread]