feat(router) add header regex matching method (#6079)

Co-authored-by: Enrique García Cota <kikito@gmail.com>

CHANGELOG.md

@@ -80,6 +80,9 @@
 - Customizable transparent dynamic TLS SNI name.
   Thanks, [@zhangshuaiNB](https://github.com/zhangshuaiNB)!
   [#8196](https://github.com/Kong/kong/pull/8196)
+- Routes now support matching headers with regular expressions
+  Thanks, [@vanhtuan0409](https://github.com/vanhtuan0409)!
+  [#6079](https://github.com/Kong/kong/pull/6079)
 
 #### Performance
 

kong/router.lua

@@ -462,13 +462,22 @@ local function marshall_route(r)
 
       if header_name ~= "host" then
         local header_values_map = {}
-        for i = 1, #header_values do
+        local header_values_count = #header_values
+        for i = 1, header_values_count do
           header_values_map[lower(header_values[i])] = true
         end
+        local header_pattern
+        if header_values_count == 1 then
+          local first_header = header_values[1]
+          if sub(first_header, 1, 2) == "~*" then
+            header_pattern = sub(first_header, 3)
+          end
+        end
 
         append(headers_t, {
           name = header_name,
           values_map = header_values_map,
+          header_pattern = header_pattern,
         })
       end
     end
@@ -1033,6 +1042,12 @@ do
               matches_headers[header_t.name] = req_header_val
               break
             end
+            -- fallback to regex check if exact match failed
+            if header_t.header_pattern and re_find(req_header_val, header_t.header_pattern) then
+              found_in_req = true
+              ctx.matches.headers[header_t.name] = req_header_val
+              break
+            end
           end
 
         elseif req_header then -- string
@@ -1041,6 +1056,11 @@ do
             found_in_req = true
             matches_headers[header_t.name] = req_header
           end
+          -- fallback to regex check if exact match failed
+          if header_t.header_pattern and re_find(req_header, header_t.header_pattern) then
+            found_in_req = true
+            ctx.matches.headers[header_t.name] = req_header
+          end
         end
 
         if not found_in_req then

spec/01-unit/08-router_spec.lua

@@ -206,6 +206,17 @@ local use_case = {
       },
     },
   },
+  -- 15. headers (regex)
+  {
+    service = service,
+    route = {
+      headers = {
+        user_agent = {
+          "~*windows|linux|os\\s+x\\s*[\\d\\._]+|solaris|bsd",
+        },
+      },
+    },
+  },
 }
 
 describe("Router", function()
@@ -451,6 +462,16 @@ describe("Router", function()
         location = { "my-location-3", "foo" }
       })
       assert.is_nil(match_t)
+
+      local match_t = router.select("GET", "/", nil, "http", nil, nil, nil, nil, nil, {
+        user_agent = "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/83.0.4103.116 Safari/537.36"
+      })
+      assert.truthy(match_t)
+      assert.same(use_case[15].route, match_t.route)
+      assert.same(nil, match_t.matches.method)
+      assert.same(nil, match_t.matches.uri)
+      assert.same(nil, match_t.matches.uri_captures)
+      assert.same({ user_agent = "mozilla/5.0 (x11; linux x86_64) applewebkit/537.36 (khtml, like gecko) chrome/83.0.4103.116 safari/537.36" }, match_t.matches.headers)
     end)
 
     it("multiple [headers] values", function()