From: Konstantin Amelichev <kostya.amelichev@gmail.com>
Date: Sat, 28 May 2022 11:30:32 +0000 (+0400)
Subject: renumber: allow renumbering a subnet to a single IP
X-Git-Tag: v5.5.1~9^2~3
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f96a1ad4b63e9e5ee2e473282ca3fdba75f950a6;p=thirdparty%2Fknot-resolver.git

renumber: allow renumbering a subnet to a single IP

https://github.com/CZ-NIC/knot-resolver/pull/77
originally but changed by vcunat quite a bit.
---

diff --git a/modules/renumber/renumber.lua b/modules/renumber/renumber.lua
index 4272fbd1f..caa47779c 100644
--- a/modules/renumber/renumber.lua
+++ b/modules/renumber/renumber.lua
@@ -3,25 +3,41 @@
 local ffi = require('ffi')
 local prefixes_global = {}
 
+-- get address from config: either subnet prefix or fixed endpoint
+local function extract_address(target)
+	local idx = string.find(target, "!", 1, true)
+	if idx == nil then
+		return target, false
+	end
+	if idx ~= #target then
+		error("[renumber] \"!\" symbol in target is only accepted at the end of address")
+	end
+	return string.sub(target, 1, idx - 1), true
+end
+
 -- Create subnet prefix rule
 local function matchprefix(subnet, addr)
+	local is_exact
+	addr, is_exact = extract_address(addr)
 	local target = kres.str2ip(addr)
 	if target == nil then error('[renumber] invalid address: '..addr) end
 	local addrtype = string.find(addr, ':', 1, true) and kres.type.AAAA or kres.type.A
 	local subnet_cd = ffi.new('char[16]')
 	local bitlen = ffi.C.kr_straddr_subnet(subnet_cd, subnet)
 	if bitlen < 0 then error('[renumber] invalid subnet: '..subnet) end
-	return {subnet_cd, bitlen, target, addrtype}
+	return {subnet_cd, bitlen, target, addrtype, is_exact}
 end
 
 -- Create name match rule
 local function matchname(name, addr)
+	local is_exact
+	addr, is_exact = extract_address(addr) -- though matchname() always leads to replacing whole address
 	local target = kres.str2ip(addr)
 	if target == nil then error('[renumber] invalid address: '..addr) end
 	local owner = todname(name)
 	if not name then error('[renumber] invalid name: '..name) end
 	local addrtype = string.find(addr, ':', 1, true) and kres.type.AAAA or kres.type.A
-	return {owner, nil, target, addrtype}
+	return {owner, nil, target, addrtype, is_exact}
 end
 
 -- Add subnet prefix rewrite rule
@@ -50,7 +66,12 @@ local function renumber_record(tbl, rr)
 		-- If provided, compare record owner to prefix name
 		if match_subnet(prefix[1], prefix[2], prefix[4], rr) then
 			-- Replace part or whole address
-			local to_copy = prefix[2] or (#prefix[3] * 8)
+			local to_copy
+			if prefix[2] and not prefix[5] then
+				to_copy = prefix[2]
+			else
+				to_copy = #prefix[3] * 8
+			end
 			local chunks = to_copy / 8
 			local rdlen = #rr.rdata
 			if rdlen < chunks then return rr end -- Address length mismatch