Add the DNS ERRORS section to the man page, in preparation for the dns library bump.

diff --git a/doc/man1/haeredes.1 b/doc/man1/haeredes.1
index 900b4c64e195bc044fc68c149b6b178dc3afb778..a614993342201c16d6da9e68baf227922d97b315 100644 (file)
--- a/doc/man1/haeredes.1
+++ b/doc/man1/haeredes.1
@@ -91,6 +91,28 @@ example, to use 10 threads,
 .nf
 $ haeredes [OPTIONS] [DELEGATES] \fI+RTS -N10\fR
 .fi
+.SH DNS ERRORS
+.P
+There are three types of DNS errors that can occur:
+.nr step 1 1
+.IP \n[step] 2
+Timeouts. If the query times out, we don't get an answer back. The
+timeout can be adjusted with the \fB\-\-timeout\fR flag.
+.IP \n+[step]
+Sequence number mismatches. Every DNS query is sent with a sequence
+number; if the response has a different sequence number than the one
+we sent, something is wrong (foul play, or a bug somewhere in the
+stack).
+.IP \n+[step]
+Unexpected RDATA. If we ask for an \fIA\fR record, we expect to get a
+response for an \fIA\fR record. If we get something else -- well,
+something went wrong.
+.P
+Haeredes is designed to ignore these errors. A timeout or bad response
+to a query is not an indication that something is wrong with the DNS
+for the supplied domains. There might be something else wrong with
+your (caching/recursive) DNS infrastructure, but it isn't one of the
+problems that Haeredes is designed to detect.
 .SH OPTIONS
 
 .IP \fB\-\-no\-append\-root\fR,\ \fB-n\fR