fix: populate ldns submodule and add autotools to LDNS build stage

- Re-cloned zonemaster-ldns with --recurse-submodules so the bundled
  ldns C library source (including Changelog and configure.ac) is present
- Added autoconf, automake, libtool to Dockerfile.backend ldns-build stage
  so libtoolize + autoreconf can generate ldns/configure during make

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

zonemaster-ldns/ldns/lua/rns-lib.lua

@@ -0,0 +1,126 @@
+-- ldns defines - need a better way to keep these current
+LDNS_SECTION_QUESTION 		= 0
+LDNS_SECTION_ANSWER 		= 1
+LDNS_SECTION_AUTHORITY 		= 2
+LDNS_SECTION_ADDITIONAL 	= 3
+LDNS_SECTION_ANY 		= 4
+LDNS_SECTION_ANY_NOQUESTION 	= 5
+
+-- rdf types
+LDNS_RDF_TYPE_NONE		= 0
+LDNS_RDF_TYPE_DNAME		= 1
+LDNS_RDF_TYPE_INT8		= 1
+LDNS_RDF_TYPE_INT16		= 3
+LDNS_RDF_TYPE_INT32		= 4
+LDNS_RDF_TYPE_A			= 5
+LDNS_RDF_TYPE_AAAA		= 6
+LDNS_RDF_TYPE_STR		= 7
+LDNS_RDF_TYPE_APL		= 8
+LDNS_RDF_TYPE_B32_EXT		= 9
+LDNS_RDF_TYPE_B64		= 10
+LDNS_RDF_TYPE_HEX		= 11
+LDNS_RDF_TYPE_NSEC		= 12
+LDNS_RDF_TYPE_TYPE		= 13
+LDNS_RDF_TYPE_CLASS		= 14
+LDNS_RDF_TYPE_CERT		= 15
+LDNS_RDF_TYPE_ALG		= 16
+LDNS_RDF_TYPE_UNKNOWN		= 17
+LDNS_RDF_TYPE_TIME		= 18
+LDNS_RDF_TYPE_PERIOD		= 19
+LDNS_RDF_TYPE_TSIGTIME		= 20
+LDNS_RDF_TYPE_HIP		= 21
+LDNS_RDF_TYPE_INT16_DATA	= 22
+LDNS_RDF_TYPE_SERVICE		= 23
+LDNS_RDF_TYPE_LOC		= 24
+LDNS_RDF_TYPE_WKS		= 25
+LDNS_RDF_TYPE_NSAP		= 26
+LDNS_RDF_TYPE_ATMA		= 27
+LDNS_RDF_TYPE_IPSECKEY		= 28
+
+function lua_debug(...)
+	print("[lua]", unpack(arg))
+end
+
+-- transpose 2 rrs in a pkt --
+function lua_record_transpose(pkt, n1, n2)
+	print("[info] [RR] transpose", n1, n2)
+	local rr_n1 = packet.get_rr(pkt, n1)
+	local rr_n2 = packet.set_rr(pkt, rr_n1, n2)
+	local rr_tm = packet.set_rr(pkt, rr_n2, n1)
+	record.free(rm_tm)
+end
+
+-- _R := random
+function lua_record_transpose_R(pkt)
+	local total = packet.rrcount(pkt) - 1
+	local rn1 = math.random(0, total)
+	local rn2 = math.random(0, total)
+	lua_transpose_record(pkt, rn1, rn2)
+end
+
+-- substitute, add, remove
+function lua_record_insert(pkt, r, n)
+	print("[info] [RR] insert after", n)
+	packet.insert_rr(pkt, r, n)
+end
+
+-- add an rr to the end of a pkt --
+-- _E := end
+function lua_record_insert_E(pkt, r)
+	local n = packet.rrcount(pkt) - 1
+	print(n)
+	lua_insert_rr(pkt, r, n)
+end
+
+-- remove an rr from the end of a pkt --
+--pop??
+function lua_record_remove_E(pkt, n)
+	print("[info] [RR] remove", "end")
+end
+
+-- increment the ancount
+function lua_packet_ancount_incr(pkt, n)
+	print("[info] [PKT] ancount incr", n)
+	an = packet.ancount(pkt)
+	n = an + n
+	packet.set_ancount(pkt, n)
+end
+
+---------------------------------
+-- higher level                --
+---------------------------------
+
+-- reverse all the rrs in a pkt --
+function lua_packet_reverse(pkt)
+	local total = packet.rrcount(pkt) - 1
+	for i=0, (total / 2) do
+		lua_transpose_rr(pkt, i, total - i)
+	end
+end
+
+-- write a buffer to a socket
+function lua_udp_write(socket, buffer_wire, sock_from)
+	-- convert the sockaddr_storage to something we
+	-- can work with
+	
+	-- checks
+	if socket == 0 then return -1 end
+	if buffer_wire == nil then return -1 end
+	if sock_from == nil then return -1 end
+	
+	rdf_listen, port_listen = rdf.sockaddr_to_rdf(sock_from)
+
+	bytes = udp.write(socket, buffer_wire, rdf_listen, port_listen) 
+	return bytes
+end
+
+
+-- initialize the pseudo random number generator
+-- frm: http://lua-users.org/wiki/MathLibraryTutorial
+function lua_rand_init() 
+	math.randomseed(os.time())
+	math.random()
+	math.random()
+	math.random()
+end
+lua_rand_init()