From 63e5ba8e69f03a584b707520db0a0821eda3024f Mon Sep 17 00:00:00 2001 From: =?utf8?q?Uwe=20Kleine-K=C3=B6nig?= Date: Fri, 14 Oct 2022 12:23:07 +0200 Subject: [PATCH] busybox: nslookup: ensure unique transaction IDs for the DNS queries MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit On machines with a coarse monotonic clock (here: TP-Link RE200 powered by a MediaTek MT7620A) it can happen that the two DNS requests (for A and AAAA) share the same transaction ID. If this happens the second reply is wrongly dropped and nslookup reports "No answer". Fix this by ensuring that the transaction IDs are unique. Signed-off-by: Uwe Kleine-König --- ...-transaction-IDs-for-the-DNS-queries.patch | 42 +++++++++++++++++++ 1 file changed, 42 insertions(+) create mode 100644 package/utils/busybox/patches/530-nslookup-ensure-unique-transaction-IDs-for-the-DNS-queries.patch diff --git a/package/utils/busybox/patches/530-nslookup-ensure-unique-transaction-IDs-for-the-DNS-queries.patch b/package/utils/busybox/patches/530-nslookup-ensure-unique-transaction-IDs-for-the-DNS-queries.patch new file mode 100644 index 0000000000..caa5ee78f3 --- /dev/null +++ b/package/utils/busybox/patches/530-nslookup-ensure-unique-transaction-IDs-for-the-DNS-queries.patch @@ -0,0 +1,42 @@ +From: Uwe Kleine-König +Date: Sat, 8 Oct 2022 19:22:52 +0200 +Subject: [PATCH] nslookup: ensure unique transaction IDs for the DNS queries + +The transaction IDs generated by res_mkquery() for both glibc and musl only +depends on the state of the monotonic clock. +For some machines (here: a TP-Link RE200 powered by a MediaTek MT7620A) +the monotonic clock has a coarse resolution (here: 20 µs) and it can happen +that the requests for A and AAAA share the same transaction ID. + +In that case the mapping from received responses to the sent queries +doesn't work and name resolution fails as follows: + + # /bin/busybox nslookup heise.de + Server: 127.0.0.1 + Address: 127.0.0.1:53 + + Non-authoritative answer: + Name: heise.de + Address: 193.99.144.80 + + *** Can't find heise.de: No answer + +because the AAAA reply is dropped as a duplicate reply to the A query. + +To prevent this make sure the transaction IDs are unique. + +Forwarded: http://lists.busybox.net/pipermail/busybox/2022-October/089911.html +--- +--- a/networking/nslookup.c ++++ b/networking/nslookup.c +@@ -978,6 +978,10 @@ int nslookup_main(int argc UNUSED_PARAM, + } + } + ++ /* Ensure the Transaction IDs are unique */ ++ for (rc = 1; rc < G.query_count; rc++) ++ G.query[rc].query[1] = G.query[rc - 1].query[1] + 1; ++ + for (rc = 0; rc < G.serv_count;) { + int c; + -- 2.30.2